text:
General Motors will sell a compressed natural gas bi-fuel commercial pickup truck early in the fourth quarter of 2012.
DETROIT, Mich. — General Motors will sell a compressed natural gas bi-fuel commercial pickup truck early in the fourth quarter of 2012.
"Customers want a choice when it comes to fuel because it helps them manage their business costs," said Brian Small, general manager, GM Fleet and Commercial Operations. "We listened and we are going to move fast to bring a bi-fuel CNG product to market to meet our customer's needs."
GM is the only manufacturer currently providing a single-source commercial option with the Chevrolet Express and GMC Savana CNG cargo vans. The addition of a bi-fuel CNG pickup will help satisfy a broader range of needs for commercial customers looking for a one-stop alternative fuel vehicle from the factory, according to GM.
The bi-fuel commercial trucks will be covered by GM's three-year, 36,000-mile new vehicle limited warranty and five-year, 100,000-mile limited powertrain warranty and vehicle emissions warranty, meeting all Environmental Protection Agency (EPA) and California Air Resources Board (CARB) emission certification requirements.
IMPCO Automotive is the Tier-One supplier for integrating the CNG bi-fuel delivery and storage system into the pickups alongside the Express and Savana CNG-dedicated cargo vans at IMPCO Automotive's facility in Union City, Ind.
A new study from Penn Medicine researchers in the Center for Clinical Epidemiology and Biostatistics demonstrated that bed bugs, like the triatomines, can transmit Trypanosoma cruzi, the parasite that causes Chagas disease.
The National Pest Management Association (NPMA) is seeking a qualified regulatory affairs professional to direct the day-to-day management and execution of NPMA's federal and state regulatory affairs programs
The country has detected its first domestic case of the painful mosquito-borne viral disease chikungunya in the southwest of the country, the state government of Chiapas said on Saturday.
The company's latest Technical Bulletin provides an in-depth description of variables to consider when developing integrated pest management (IPM) programs in school settings.
Ronnie Caldwell, president of Innovative Pest Management, Denver, N.C., is one of the stars of the new Bruce Hedrick video 'A Better Man.'


text:
We stayed here for a weekend to see the sights in Moscow. The WiFi and mini bar were excellent. The rooms clean and comfortable. The breakfast was adequate and gave us a good boost for the start of the day. The staff were excellent if a little rushed given how busy they were. The hotel is 3 mins from a... More
- Reservation Options:
- TripAdvisor is proud to partner with Booking.com, Expedia, Travelocity, Priceline, Hotels.com, Orbitz, Agoda, Despegar.com, Odigeo, Hotel.de, TripOnline SA and Tingo so you can book your Katerina Park Hotel reservations with confidence. We help millions of travelers each month to find the perfect hotel for both vacation and business trips, always with the best discounts and special offers.
- Also Known As:
- Katerina Park Hotel Moscow
- Eurolux Hotel Moscow

subset: commoncrawl


text:
Keeping the garden tidy requires a few deft moves with the right tools, and, time and again over the seasons, shrub rakes are... Read more »
Entire books have been written on the science of making compost, but it isn't as hard as people think. In five easy steps, you... Read more »
Weeding, pruning, and raking all make a huge difference in the appearance of a garden, but, to finish the job, you have to rou... Read more »
The Fiskars® aluminum shrub rake features a slim head with uniquely tapered tines that are perfect for reaching into tight spac... Read more »
Our Eco Bin Composter features an easy-to-assemble, easy-to-use design that can simplify and speed the composting process. It i... Read more »
Our HardShell® Kangaroo® Gardening Container is perfect for all your outdoor cleanup needs — whether you're gathering yard and... Read more »
Are school fundraiser ideas keeping you up at night? A unique handmade art piece that represents your school is sure to be a p... Read more »
Creating beautiful and personal touches does not have to be difficult, especially when you have great designs to work with! Read more »
Recycle and give a new life to some of your old T-shirts Read more »
Teresa Collins is a top craft celebrity who has been featured numerous times on My Craft Channel, HSN, QVC and DIY network, wel... Read more »
Teresa Collins is a top craft celebrity who has been featured numerous times on My Craft Channel, HSN, QVC and DIY network, wel... Read more »
Our unique Tag Maker with Built-in Eyelet Setter features an innovative design that makes it easy to create tags perfect for gi... Read more »
By creating a few simple tags, you won't be caught at the fabric store not knowing what fabrics or yardage you have in your st... Read more »
A brocade drawstring pouch can be a beautiful and luxurious accessory or gift. Read more »
Transform a simple hoodie into a super simple unicorn costume and take the stress and pressure out of making a complicated Hal... Read more »
Perfect for a wide range of sewing and quilting tasks, our Amplify® RazorEdge™ Serrated Fabric Shears sense blade separation an... Read more »
Perfect for a wide range of sewing and quilting tasks, our Amplify® RazorEdge™ Fabric Shears sense blade separation and force t... Read more »
Perfect for a wide range of crafting and mixed media tasks, our Amplify® Mixed Media Shears sense blade separation and force th... Read more »
Are school fundraiser ideas keeping you up at night? A unique handmade art piece that represents your school is sure to be a p... Read more »
Try some new punches out and make some cards to celebrate World Card Making Day! Read more »
A personalized Duck Tape® crown is quick and easy to make with your Fiskars® Duck® Edition Scissors. It is a fun way to cele... Read more »
Our Preschool Training Scissors features a special training lever that opens the blades after each cut, helping children learn... Read more »
Children love our Designer Non-stick Blunt-tip Kids Scissors for the colorful handle patterns that make cutting fun and the non... Read more »
Our Designer Non-stick Student Scissors are larger than our Kids Scissors but smaller than adult scissors, perfect for those ol... Read more »
Transform a basic jacket into something personal and unique. Read more »
Create a simple reusable calendar to plan all of your back to school activities. Read more »
Creating a miniature collage with your Fiskars® Duck® Edition Scissors is a great way to use up any last bits of Duck Tape® yo... Read more »
Designed for long, easy cuts down strips of Duck® Tape, our Duck® Edition Scissors feature a non-stick blade coating that preve... Read more »
Designed for all-purpose cutting through a range of craft materials that incorporate glue, tape and other sticky adhesives, our... Read more »
Designed for tight, precise cuts through a range of craft materials that incorporate glue, tape and other sticky adhesives, our... Read more »
Our belief is that gardening should be a joy, not a struggle. Our PowerGear® tools are designed to make taking care of your landscape easier and more enjoyable.
Because PowerGear® tools multiply your leverage and cutting power, you'll discover that the effort it takes to cut a branch is dramatically reduced.
This extra cutting power also means our loppers and shears can be lighter and smaller than traditional tools, reducing strain on your hands, wrists and muscles when you're reaching to cut a branch or have a lot of branches to cut.
PowerGear® pruners feature a contoured handle with a unique rolling design that fits the shape and natural motion of your hand for easy, comfortable pruning.
Many PowerGear® tools have been awarded the Ease-of-Use Commendation from the Arthritis Foundation®. But they're not just for people with arthritis — they're for anyone who wants to make maintaining beautiful trees and shrubs easier.
Learn more about Ease of Use »
The first time you try PowerGear® tools, you'll be amazed. But it's not magic — it's the gears. Our patented technology multiplies your leverage to give you up to three times more power on every cut. This means you can power through thick branches that you wouldn't be able to cut with traditional tools.
Our blades are slim and sharp to glide through branches smoothly, fully hardened to stay sharp through heavy use. They include a special low-friction coating to cut without gumming up with sap and debris and resist rust for lasting value.
All of our PowerGear® tools are designed for lasting durability and performance, helping you maintain a beautiful landscape year after year. They're also backed up with a full lifetime warranty as a guarantee of quality.
Fiskars is known for developing quality, long-lasting tools — like our iconic Orange-Handled Scissors — that help people do the things they love. Our PowerGear® tools set the standard for pruning power and ease of use worldwide.
PowerGear® tools aren't just loved by gardeners around the world — they've also earned awards for extraordinary design excellence.
Watch Choosing the Right Pruning Tools video»
Use pruners to make quick, clean cuts on flowers, stems, shrubs and branches up to 1" in diameter.
Use loppers to power through thick branches up to 2" in diameter.
Use hedge shears to sculpt and shape your hedges and decorative shrubs, or cut back grasses and perennials.
Many people hesitate to cut back their trees, hedges and shrubs — they're afraid they'll hurt their plants. The truth is, proper pruning can improve the health and appearance of your trees and shrubs while protecting them from damage.
Sign up today for project inspiration, tips, techniques and product specials.
© Fiskars Brands, Inc.
Orange-handled scissors are a registered trademark of Fiskars Corporation.


text:
Tug engineers withdrew plans to strike at Port Hedland, Australia's biggest iron ore port, tug operator Teekay Shipping said on Thursday, removing a threat to exports
Port operator APM Terminals, a unit of shipping and oil conglomerate A.P. Moller-Maersk , said on Thursday it had signed a memorandum of understanding with the
Lynden Logistics, LLC signed a letter of intent with Chieftain Metals Corp. to provide barge services in support of the construction and production of the Tulsequah Mine in British Columbia.
South Korea launches a massive new government agency this week to handle emergency rescue and safety management seven months after a ferry disaster killed 304 people
The U.S. Coast Guard (USCG) and U.S. Environmental Protection Agency (EPA) will soon take action to ensure compliance with the forthcoming 0.10 percent fuel sulphur limits in the North American and U.
Dr. David Mazurek, a civil engineering professor at the U.S. Coast Guard Academy, has been named the winner of the 2015 U.S. Coast Guard Engineer of the Year Award.


text:
This unofficial site is designed to provide statistical information and background detail on the Shrimpers from their formation in 1906 to the present day. It lists every first team player since 1920, every football league and cup match and more.
Southend are in a play off spot 7th in SkyBet League 2, lost 1-2 at home to Vanarama Conference outfit Chester FC in the FA Cup 1st round, lost 1-2 at home to League 1 Walsall in the 1st round of the Capital One Cup and lost 4-2 on penalties (Coker saved; Barnard missed) after drawing 2-2 against AFC Wimbledon away in the Johnson's Paint Trophy.
If you want more Southend United information check out the official club website, the Shrimperzone forums, the Sky Bet League site, the Southend Evening Echo site or the BBC Essex Radio site.
Southend were the first and last team to win at the Abbey Stadium during Cambridge United`s League period.
There are no records of any Southend players having a birthday today.1912: Customs House 0 Southend 1 : FA Cup Qualifying Round 3
1946: Southend 2 Aldershot 1 : Division 3 South
1974: A P Leamington 1 Southend 2 : FA Cup Round 1
1991: Southend 2 Barnsley 1 : Division 2
1996: Stoke City 1 Southend 2 : Division 1
2013: Southend 2 York City 1 : League Two
There have been 136439 visits to this site since it was updated. 9197 are unique visitors with 3 online at this moment.


text:
Our Newest Items :: Downloads :: Hot Deals NEW :: Message Board :: Why Shop Here? :: Contact Us
Hot Deal
Cards Of Influence by Kenton Knepper
$39.95 $13.50
Save: 66% off
Reward Points
No points earned yet on current order.
Log in to see how many reward points you have already earned
Great store/Service
Great place. I used to order at magic.org and Penguin, but then I came across MJM and I saw 10% discount and read some testimonials, read about how...
Really great service and good prices
I recently was contemplating an order with you guys, but had a few questions. Well, the questions were answered almost as fast as I could ask them....


text:
Editing of Bulbapedia is currently restricted. Please see this message for more details.
Pokémon Omega Ruby and Alpha Sapphire have arrived!
Check BNN and Bulbanews for up-to-date Pokémon news and discuss it on the forums or in our IRC channel.
Imakuni?'s PC (Vending S3)
From Bulbapedia, the community-driven Pokémon encyclopedia.
|This article is about a Japanese Pokémon Trading Card Game card which has not yet been officially released in English and, hence, may not be released outside of Japan. As such, this article may contain translated Japanese terms instead of English terms.
Imakuni?'s PC (Japanese: イマクニ?のパソコン Imakuni?'s Personal Computer) is a Pass Card card. It is part of the Extended Sheet 3.
Card text
- The entire card is hand drawn, as are several of the bonus cards released in Extended Sheet 3.
- This is one of several 'spoof' cards that are featured exclusively in Japanese releases.
|This article is part of Project TCG, a Bulbapedia project that aims to report on every aspect of the Pokémon Trading Card Game.


text:
Easier street races for Grand Theft Auto: Vice CityHome / PC - Windows /
This page contains Grand Theft Auto: Vice City Hints for PC - Windows called "Easier street races" and has been posted or updated on May 19, 2008 by wheeliegal92. Let us know what you think of this Hint by thumbs voting.
- Developer: Rockstar North
- Publisher: Rockstar Games
- Genre: Action Adventure Modern
- Release Date: May 12, 2003
- ESRB: Mature
Easier street races
There are two things that are extremely helpful when street racing. First, you do not have to park in the pink area. Hitting a competitor will start the race automatically. To get an advantage, get some speed in the direction of the first checkpoint, then just barely nick the lead car as you fly by. They will all be left in your dust, and probably will not catch up. Secondly, especially for the final race, you may want to block them off with a giant vehicle, like a Coach or Packer. When coupled with the first trick, you just may win.
Back to all Cheats
Stuck on this game? Set a specific, clearly defined question and let others answer your question or view answers to previously asked questions. If you think you are an Grand Theft Auto: Vice City expert then please try to help others with their questions.
Grand Theft Auto: Vice City - Trailer
- Aug 22, 2014, Views: 207
Grand Theft Auto: Vice City - Action Gameplay
- Aug 22, 2014, Views: 155
Grand Theft Auto: Vice City - Blue Hesper Trailer
- Aug 22, 2014, Views: 131
Grand Theft Auto: Vice City - Shakedown Gameplay
- Aug 22, 2014, Views: 164
- EverQuest 2: Altar Of Malice - Expansion Trailer, (PC)
- The Book Of Unwritten Tales 2 - Gameplay Video, (PC)
- Company Of Heroes 2: Ardennes Assault - Gameplay Review Trailer, (PC)
- Construction Simulator 2015 - Teaser Trailer, (PC)
- Never Alone - Gameplay Review Trailer, (PC)
- Adventure Time: Secret Of The Nameless Kingdom - Demo Gameplay, (PC)
- Soul Axiom - Teaser Trailer, (PC)
- Onikira - Demon Killer - Gameplay Review Trailer, (PC)
- Kim Kardashian: Hollywood - Gameplay, (iPhone-iPod)
- Episode: Choose Your Story - Gameplay, (iPhone-iPod)
- How To Train Your Dragon 2 - Ready To Fly Trailer, (Wii)
- The Settlers - Kingdoms Of Anteria - Announcement Trailer, (PC)
- Entwined - Quick Look Trailer, (PS3)
- Blue Estate - Official Launch Trailer, (PS4)
- Goat Commando 3D Simulator - Gameplay, (iPhone-iPod)
- Munin - Official Launch Trailer, (iPad)


text:
word meaing,,,,,pussy boy invented kanjari
kuku: howz about u du 1 kus walad! huh!
kuku: howz about u du 1 kus walad! huh!
by 3zeema fara7 April 18, 2008
10 Words Trending Now
Alphabetical List
Type your email address below to get our free Urban Word of the Day every morning!
Emails are sent from firstname.lastname@example.com. We'll never spam you.×


text:
This facial loving milf got the ride and suck of her life after putting up a room for rent. The lucky mature had the pleasure of meeting and fucking a young black stud, something she'd always secretly dreamed of. After flirting with him for a while the little blonde devil decide to push the envelope and go to straight on fucking as part of sealing their deal and our amateur milf got her reward. The guy sprayed his juices on her pretty little face giving her a massive facial from a massively hung stud!
Mommy makes me cum!
Tattooed milf all dressed up still gets down and dirty and gets a rewarding facial! She might be wearing her business clothes at first but that hot body anyone would like to fuck doesn't stay hidden for long, she takes a cock like she hasn't had any in ages and there's no stopping her once she gets started, yummy mommy!
Redhead MILF with big tits and big appetite for cum
Taking off this milfs sleazy leopard patter dress was easy for our well hung stud. Satisfying her enormous appetite for cum took a little more work though. After enjoying this redhead milfs generous cleavage this guy knew he was going to get a fantastic ride out of the mature slut, so he didn't waste any time undressing her and getting down to business. Her craving cunt could barely take in his thick stick but once the fun started it was all screams and moans until the final orgasm. He dropped his generous load painting that mature woman's face with a huge and messy facial!
Black guy on white milf anal and facial
What do you think rich white MILFs like this one dream for all day? Pretty sure it's about having a black stud give her dirty milf face a facial she won't soon forget. The guy takes advantage of the horny mature slut and rams her naughty tight asshole until he's satisfied and she's screaming and cursing. But to top it all off he decides he needs to teach her dirty mouth a lesson too so he shoves his big dick inside it until she finally takes his full load all over her face and lips, what a naughty milf who loves huge facials!
Big boobed redhead milf slowly sucking
You just gotta love a sweet redhead MILF like this, especially when she's asking for a big messy facial. After undressing her new lover she just couldn't wait to go down on his nice hard wad, starting to slowly suck his cock with her delicious lips. She was eagerly hoping that the guy would make her happy with a huge facial but the guy wasn't ready yet. That nice mature ass and pussy deserved some hard fucking first before he unleashed his load in her dirty mouth.
Sharing a dick was always a dirty fantasy for this young teen babe and her smokin hot MILF girlfriend, and it finally came true! The two horny girls enjoyed some sensual kissing and caressing before getting down to the real hardcore business of satisfying that cock. They each took the man's dick inside them in turns, making him harder and stiffer, ready to release his semen to them. But they would only let the poor fellow finish by giving this teen cunt and her milf lover a dirty facial, making sure that they share that load on both their faces!


text:
"Having enjoyed several Shutterfly photo books received as gifts from my son, I couldn't resist trying to create them myself. The ease of creation and the wonderful results got me hooked on Shutterfly. I've created six books so far, and I have the intention of scanning in all our photos and creating photo books to showcase them all.
Just when I thought this photo creativity couldn't get any better, I decided to try my hand at greeting cards. My wife and I recently retired to the west coast and wanted some all-purpose cards to use for note cards and thank you cards. The quality of the cards I received has surpassed my expectation by a mile. They are incredible. I went with matte finish which I prefer. The cards are coated in what seems to be a plastic protective layer which will likely make these cards keepers. They're nice enough to frame.
Even with the shipping cost, the cards are cost effective to give as one-off personalized birthday cards. I'll never use a store bought card again."
"This was my first time using Shutterfly for something other than a calendar. Only ordered one box of cards to see if the quality of reproduction and paper stock was as good as the calendars. To my delight, it was. These cards are so good, and the envelopes are also very good quality. I have sent thank you cards out in the past, and have NEVER received any response from the recipients (not that I would expect to), but with these cards, I did hear from the two people I sent them to as soon as they received it. My only criticism is the delivery time. While I received an e-mail from Shutterfly telling me that my package was on its way, it seems to take much longer for delivery (same for calendar orders) than it does for other companies I have used. With that said, based on the quality, the versatility of designing your own card, and the ability to shop multiple products while on the Shutterfly site, I am hooked on Shutterfly. The other website company that I have used in the past does not allow you to make multiple product purchases - you need to order one item, and then go in and design/place your next order (no shopping cart available). Based on my satisfaction with these Thank You cards, I've already ordered other Shutterfly products to see if I will be as satisfied as I was with these Thank You cards. If so, it's going to make my "gift giving" needs much easier throughout 2013!
I highly recommend these Cards."
"Great card, quality photo print. Typical of Shutterfly. I used this card to thank my guests for thier baptism gift to my daughter. I sent a picture of them with her, because of this each was customized. This was one of the few cards you can order in qty of 1."
"I uploaded 3 pictures into this card from my computer, also inserted 2 paragraphs and ordered it in one night. My cards arrived quickly, Shutterfly got it right the first time, super high quality. Very satisfied, will order more."
"I had an amazing picture of my grandson as he walking down the sidewalk alone. I wanted just the right framed card to put it on and was excited to find the Dots Slate Multi card. The colors of the frame seemed to match his outfit perfect. This card made the cutes Grand~Parents Day card.
I would recommend this feature to anyone wanting a unique card."
You have so much for which to be thankful. Stay on top of it all with personalized thank you notes and thank you cards to have handy at your desk. Perfect for thanking a party host or holiday gift-giver, photo thank you cards and non-photo thank you cards are a more personal alternative to a store-bought thank you card. With plenty of room to express your gratitude with style our collection of thank you cards also make a wonderful personalized gift.You might also like: boy thank you cards, girl thank you cards, teen thank you cards, adult thank you cards, graduation thank you cards, baby boy thank you cards, baby girl thank you cards, neutral thank you cards, holiday thank you cards and wedding thank you cards.


text:
Outreach Counselor
Organization: Urban PeakTitle: Outreach Counselor
Categories: Nonprofit Jobs
Region: Denver Metro Area
Subcategory: Programs/Services
Org Type: 501(c)(3)
Under the supervision of the Outreach Supervisor, the Outreach Counselor will be responsible for connecting with youth on the streets and to build healthy and strong relationships with these youth in hopes of helping them on a path of the youth's choosing. The Outreach Counselor acts as a liaison on the streets to inform youth, community groups and businesses about the services offered by Urban Peak to promote the health, safety and well-being of homeless and runaway youth and to assist youth in permanently exiting street life. Other duties include coverage of the Drop-in Center, outreach on the streets and to Denver area shelters, intensive case management of a designated case load and HIV and AIDS education. Works as part of a larger interagency team to coordinate care and outreach services as part of the Denver Street Outreach Collaborative.
· The position requires a Bachelor's degree in human services, social work, psychology, sociology or related field; and a minimum of two years (2) experience working with high-risk adolescent populations or youth experiencing homelessness.
· Experience in providing trauma informed care or willingness to adapt this approach is required.
· Experience, competence and sensitivity and, the ability to connect well and work effectively with the homeless youth population, especially youth who identify as LGBTQ, are often difficult to engage, mentally ill, addicted to substances or otherwise impaired.
· Skill in operating office equipment, such as computers, software (e.g., Microsoft Word, Excel and PowerPoint; email) and telephones.
· Skill in oral and written communications.
· Skill in negotiating and mediating, particularly in sensitive situations.
· Able to communicate effectively with a diverse population.
· Able to make sound decisions, using available information while maintaining appropriate confidentiality.
· Able to function as a member of an interdisciplinary team and work with collaborating agencies.
· Able to manage tasks and activities in an environment that sometimes includes interpersonal conflict and chaos.
· Must be team-oriented and able to coordinate with various departments and staff.
· Knowledge of street outreach and ability to train volunteers in conducting street outreach and demonstrated appreciation of clear and appropriate boundaries with youth are also required.
· Must be insurable as a driver on Urban Peak's auto liability policy to transport youth using an Urban Peak vehicle and an approved personal vehicle
· Must pass both federal and state background checks
· Must pass pre-employment drug screening.
This is a full-time position requiring a schedule of 40 hours per week. These may
be early morning, day, evening, and late evening hours, including some daytime
hours for required meetings and weekend hours.Work on holidays will also be
This is a non-exempt position with a starting wage range of $15.14 per hour, depending upon skills, qualifications, and experience.
To apply:
Please submit cover letter, resume, and the names and telephone numbers of three (3) professional and/or academic references to:
Urban Peak
ATTN: Human Resources
730 21st Street
Denver, CO 80205
Fax: (303) 295-6116
E-mail: email@example.com
All attachments should be in Microsoft Word (.doc) or portal document format (.pdf). Also, include your first and last name and the title of the position you are applying for in the subject field of the email (Example: Job Title – Last Name, First Name).
This position will be filled as soon as a qualified candidate is identified.
Due to limited staffing resources we are unable to respond to phone inquiries, including calls to check on the status of a submitted application. Applicants will only be contacted if selected for an interview.
This job announcement is not intended to be an exhaustive list of all duties, responsibilities, or qualifications associated with the position.
Urban Peak is an equal opportunity employer and seeks a diverse pool of applicants.
This is a posting on Colorado Nonprofit Association's Career Center.


text:
Mario and Sonic's winter outing dated for October 16
Mario and Sonic at the Olympic Games a lot, but -- as horrible as we thought it was -- it managed to capture the interest (and money) of almost every man, woman, and child in all of the UK. So, Sega is working as fast as it can to get the latest version of its new money-printing machine, Mario and Sonic at the Olympic Winter Games, out to retail, announcing that the game will release this October.
Breaking News
Dying Light cancelled on Xbox 360, PS3
Featured Stories
Get a closer look at final retail Amiibos
Posted on Nov 22nd 2014 9:00AM
Barely Related: Star-Lord's dance-off, comet sounds
Posted on Nov 21st 2014 8:30PM
Games we love and hate
Posted on Nov 21st 2014 3:00PM


text:
Dr. Nichola A. Carpendale, MD
Urgent Care Medicine, Palo Alto Medical Foundation
- 795 El Camino Real
Palo Alto, CA 94301
- 1 Office Location
- (650) 853-2952
Dr. Nichola A. Carpendale has been practicing medicine for 29 years. Dr. Carpendale graduated from the Medical College of Pennsylvania in 1985. She practices medicine in Palo Alto, CA and specializes in Urgent Care Medicine. Dr. Carpendale is affiliated with El Camino Hospital, Stanford Hospital & Clinics and Washington Hospital Healthcare System. She speaks Arabic, Chinese, English, French, German, Italian, Korean, Polish, Portuguese, Russian, Spanish, Tagalog and Vietnamese.
Gender: Female
Years in Practice: 29 Years
Languages Spoken: Arabic, Chinese, English, French, German, Italian, Korean, Polish, Portuguese, Russian, Spanish, Tagalog, Vietnamese
Medical School: Medical College of Pennsylvania
Graduation Date: 1985
Hospital Affiliations: El Camino Hospital, Stanford Hospital & Clinics, Washington Hospital Healthcare System
Specialties: Urgent Care Medicine


text:
Forgot Password? | Not a User? Sign up
Your browser does not support iframes.
Kentucky's new tourism TV advertising campaign, "There's Only One," has received national recognition in the 2012 Telly Awards.
New West LLC was notified Friday that it won a silver award, the highest honor, for the campaign. The award was given in the Regional TV & Multi-Market Cable category within the subcategory of Campaign – Promotional/Branding.
Abraham Lincoln Birthplace National Historic Site is part of the campaign: "Only one birthplace of Lincoln.:
The merger between two of the nation's leading Midwest-based general merchandise retail chains, Shopko and Pamida, is now complete, creating one of the largest U.S. retailers focused on serving smaller, rural communities.
With nearly $3 billion in annual revenues, the combined entity, which is retaining the Shopko name, features nearly 350 locations in 22 states with more than 20,000 employees.
Financial details of the merger were not disclosed.
Members of the Leadership LaRue County class visited Frankfort in February. From left, Jessica Davis, Jeremy Hinton, Faith Miller, JoAnna Hinton, Allison Shepherd, Adam Gordon, Beth Turner, Diana Leathers, Nedra Jurcak, Clint Williams and Patti Donahue. The class is sponsored by the LaRue County Chamber of Commerce.
Dr. James Mumford has accepted the position of medical director for Passport Health Plan. He is joining the Plan's medical affairs team and will be responsible for improving the Plan's quality and clinical processes. Dr. Mumford was most notably a previous surveyor for the National Committee for Quality Assurance.
The LaRue County Chamber of Commerce hosted a ribbon-cutting ceremony for a new photography business located on North Lincoln Boulevard in Hodgenville.
Melanie Wells Photography held their grand opening Friday with the help of several Chamber members and guests.
The shop is located behind the MAM Candy building.
Wells opened her doors in January after leaving her job as a night shift coordinator for the Internet help desk at Bluegrass Cellular Inc. after seven and a half years of service to pursue her dream.
Magnolia Bank Board of Directors have announced several promotions:
Chong Mike has been selected as the January Employee of the Month for Nationwide Uniform.
She has been employed with Nationwide since May 1996 and is under the supervision of Dawn Burgess in the special forces dept.
She will receive a special award for her dedication and service.
As the economy continues to show signs of recovery, the LaRue County Chamber and its members are looking ahead to the 2012 tourist season with great enthusiasm.
Sandy Wheeler has been selected as the February Employee of the Month for Nationwide Uniform.
She has been employed with Nationwide since November 1993 and is under the supervision of Charlotte Elzy in the shipping department. She will receive an award for her dedication and service.
Tony York has been in and out of Hardin County's restaurant business for more than 25 years. In 1985, he started working for Green Bamboo, and later he moved to Stone Hearth and Glendale's The Depot before eventually taking ownership of the restaurant.
York said it was common practice in Hardin County restaurants to allow customers to bring alcohol in to drink with a meal if they asked.
"Nobody questioned the legality of it because it was never pursued," he said.
Copyright © 2014
The LaRue County Herald is your source for local news, sports, events and information in LaRue County, KY, and the surrounding area.


text:
Upcoming Events
Chicago, IL -- Illinois Carol Fisher Chapter
Welcome to Team Illinois! This winter our Chicago-area team trains along the Chicago lakefront.
Not sure about a half marathon yet? Join us for TC Lite! TC Lite is a 5 week, 5 mile training and fundraising program. Training starts on November 11 and runs through the event, Rudolph Ramble on December 14.
Summer 2015 brings new adventures for Team Challenge Illinois as we head to Newport, Road Island and Napa Valley, California. Both races will be in July and training will begin the final week of March. Stay tuned for more information about our summer 2015 program!
For more information, call Bridget at 630-815-2990, e-mail firstname.lastname@example.com, or join us for one of the upcoming Group Training Sessions listed below.
Information Meetings
Team Events!
|Event Name
|Sat, Nov 22
|Group Training Session -- PB Team
|Recreation Drive, Chicago
|Sat, Nov 29
|Schaumburg Turkey Trot --
|Elk Grove Village
Change Your Life: Join Our Team
Here's what Team Challenge offers you:
- Personalized fitness training by an experienced coach for a period of three to four months
- Expenses-paid weekend away to a great destination race
- A supportive team to train with each week
- Training clinics and helpful tips on topics like nutrition, hydration, injury prevention and shoe fit
- Team Manager, a dedicated staff person from CCFA who coordinates team events, guides you through fundraising, and is your #1 personal cheerleader
- Mentor, a past participant of Team Challenge who can show you the ropes and be your personal fundraising coach
- Team uniform including a training shirt and race day singlet
ContactBridget Hannon
Team Challenge Endurance Manager
Illinois Carol Fisher Chapter
2200 East Devon Avenue, Suite 392
Des Plaines, IL 60018


text:
StartUpHire is the place to find Database Engineer/DBA jobs. Review the list of Database Engineer/DBA career opportunities to the left. These Database Engineer/DBA jobs represent some of the most rewarding careers available.
You can refine your job search for Database Engineer/DBA career opportunities by adding a job title, company name, or keyword to the search box above … or click the "Advanced Search" link for more options.
Don't see the employment opportunity you're looking for? Check back soon for more Database Engineer/DBA jobs, or sign up for an email alert (link below) to receive periodic updates on new Database Engineer/DBA jobs.
Vormetric is making the world a better place by enabling organizations around the world ? including 17 of the Fortune 25 ? to both reduce their risk and lower their costs as they protect what matters: their sensitive data. The threats to our customers? valuable data are ever9/29/2014 San Jose, CA Save This Job
DB2 DBA/Support Engineer. full time. Menlo park, Ca. This is a full time role for a DB2 DBA/Support professional who would work with professional services and support during both installation and for future DB2 support cases. The ideal candidate will have strong experience11/25/2014 Menlo Park, CA Save This Job
What We Do: The Fieldglass Vendor Management System (VMS) allows organizations to better procure and manage their flexible workforces, including contingent labor, independent contractors and services managed through Statements of Work. Leading companies rely on Fieldglass to gain10/29/2014 Naperville, IL Save This Job
You know LivingSocial as the marketplace to buy and share the best things to do in your city and beyond. And while we're bringing excitement and value to our merchants and consumers, we're also committed to creating a world-class environment for our employees. Our talented11/21/2014 Washington, DC Save This Job


text:
Nairaland ForumWelcome, Guest: Join Nairaland / Login / Trending / Recent / New
Stats: 1272884 members, 1746590 topics. Date: Sunday, 23 November 2014 at 02:00 AM
Nairaland Forum / Nairaland / General / Education / Imo State University Imsu Admission First List Out! (24292 Views)
Imo State University (IMSU) 2012/2013 Admissions & Post Ume Thread / Imo State University [IMSU] Releases 2nd Supplementary Admission List / National Open University(noun) Admission First List Is Out: (1) (2) (3) (4)
|Imo State University Imsu Admission First List Out! by hopc: 1:18pm On Jan 11, 2010
IMO STATE UNIVERSITY ( IMSU) Admission first list is OUT
If your name is not yet out don't lose hope second list will come out soon
Admission Guarantee Only for Social Science
candidates. Your admission is at your hand stop waiting when manner will
fall from above work yourself into the university.
FOR YOUR 95% assurance of getting admission.
What if it did not work out? I don't think so because your admission is rest assured
its not all about stories its your real and rare chance but then how determine are you?.
100% assurance of getting your money back. If it did not work out!
Further inquiry call 08030948096
Email firstname.lastname@example.com
|Re: Imo State University Imsu Admission First List Out! by Paschaldasilva(m): 7:49pm On Jan 11, 2010
nice to hear that.
|Re: Imo State University Imsu Admission First List Out! by mecussey(m): 11:31am On Jan 12, 2010
This years admission to IMSU is above every body's head, don't let any body dupe you, unless you are Ohakim sister inlaw brother,
|Re: Imo State University Imsu Admission First List Out! by jambanswers2014: 8:57pm On Sep 09
Gain admission into any nigerian with my aid call me now lets talk 08139396628
(0) (Reply)
Students Dont Want ASUU Strike To End - ASUU President / Nigerian Graduates With 5.0 CGPA From Russian University / Fire Outbreak At Awolowo Hall, OAU University (Pictures)
(Go Up)
|Sections: politics (1) business autos (1) jobs (1) career education (1) romance computers phones travel sports fashion health
religion celebs tv-movies music-radio literature webmasters programming techmarket
Links: (0) (1) (2) (3) (4) (5) (6) (7) (8) (9)
Nairaland - Copyright © 2005 - 2014 Oluwaseun Osewa. All rights reserved. See Nairalist and How To Advertise. 16


text:
In March of 1970, having been shown an advertisement for the newly-published book in the New York Times, Coca-Cola brand manager Ira C. Herbert wrote to Grove Press and asked that they stop using the quote "it's the real thing"—a slogan associated with the soft-drink since the 1940s—when promoting Diary of a Harlem Schoolteacher, Jim Haskins' classic first-hand account of life as an African-American teacher in 1960s Harlem, New York. A few days later, Grove Press's Richard Seaver responded defiantly with a letter that was both hugely entertaining and instantly effective, as it resulted in silence from the beverage behemoth from that point on. The full exchange can be read below.
- 2
- 154
Page Views
- 37
Posted by dotCore |
Submitted: Aug 15 2013 / 15:31


text: Uncover a Golden Ticket and win up to £5,000,000 at 888ladies Bingo Visit 888Ladies Save For Later by Bettingpro StaffPosted Share: 0 0 0 Get Bingo Alerts Uncover your dazzling Golden Ticket until 27th February to take part in the Golden Ticket game on 6th March, 2011 where you could win up to £5,000,000. There is £50,000 guaranteed to be won at 888ladies. This year there are more ways to grab a golden ticket with both extra tickets and extra ways to win. There are five fun, different ways for you to win 40 Golden Tickets which are up for grabs every day. 888Ladies has five ways to win everyday. 1. New comers win Golden Tickets on your first deposit888ladies will be welcoming their newbies to the 888ladies family with Golden Tickets. 10 Daily Golden Tickets will be given away in a raffle for all new comers who have deposited for the first time that day. 2. Instant Gamers - Score Golden Tickets on Instant Games888ladies is giving away 5 Daily Golden Tickets every day in a raffle for all those who have wagered £50 or more on all instant games that day. Also, there are another 5 Daily Golden Tickets up for grabs for all those who have wagered £50 or more on the Irish luck slot machine. That's 10 Golden Tickets each day for the instant gamers. 3. Freebies - Get Golden Tickets with Free BingoThere are 5 Daily Golden Tickets available to all those who won 1 of the 5 free Golden bingo games that day. Bingo on the Golden Pattern and you will win a Golden ticket plau £5 for free. You can get up to 6 free cards per game at 888ladies. Golden Room: Studio 75 Golden Times: Daily- 7:00, 9:00, 15:00, 22:00, 00:00 Card price: FREE (max 6 tickets) 4. 75 Ballers - Snap up Golden Tickets in 75 ball bingo888ladies is giving away 10 Daily Golden Tickets to all those who won on the "Golden Pattern" in the 75 ball bingo games that day. Max out to win a Golden ticket as well as the £50 guaranteed Jackpot; tickets cost as little as 10p each. Golden Room: Studio 75 @ 11:45, 13:45, 15:45, 17:45, 23:45 Golden Room: cheeky chatters @ 18:45, 19:45, 20:45, 21:45, 22:45 Card price: 10p 5. Gold Ladies - Exclusive Golden Tickets for Gold ladies888ladies is giving away five Daily Golden Tickets to all the Gold 888ladies who bingo on a full house (3 lines) in the 90 ball Champagne Time room. Max out to win a Golden ticket in addition to the £55 guaranteed Jackpot, for as little as 5p per card. Golden Room: Champagne Time Golden Times: Daily- 19:30, 20:30, 21:30, 22:30, 23:30 Card price: 5p (max 96 tickets) The Final £5,000,000 Golden GameWhen you win your Golden Ticket(s), you will receive an actual shiny Golden Ticket in the post. Then you must await the exciting £5,000,000 Golden bingo game which will take place on 6th March at 9.00pm. It has a guaranteed jackpot of £50,000. Visit 888Ladies Read our 888Ladies review Deposit £5 play with £20 with the 15FREE promo code now! From Around the Site How to make £340 profit from risk free bets on Manchester United beating Arsenal on Saturday Ladbrokes punter bets £10,000 on Jimmy Bullard to win I'm A Celebrity Paddy Power pay out on Chelsea winning the Premier League Arsenal v Manchester United free bets and enhanced odds No Deposit Required Free Bets No Deposit Required Free Bets at Casinos - November 2014 facebook Twitter gPlus Send email Reddit More Reddit Su Link All Bingo News Recent Bingo Promotions Articles Lucky Pants Bingo Halloween SpecialsLucky Pants Bingo gears up for Halloween; join now to cash in on some spooky wins.... bet365 Bingo's Top Promos for the WeekTake part in these top weekly promos for big wins and bonuses at bet365 Bingo.... William Hill Bingo's Top Offers for the WeekTake part in the top promotions this week for big wins at William Hill Bingo.... Ladbrokes Bingo's £1 Million GiveawayThere's a share of £1 Million and daily bonuses waiting to be won Ladbrokes Bingo.... Betfred Bingo's £1 Million Giveaway & Other OffersThere's a lot waiting to be won at Betfred Bingo this month; sign up now to find out more.... Win a trip to New York & Boston at JackpotjoyRelive the romance of the iconic Breakfast at Tiffany's and win a trip to New York at Jackpotjoy.... Win £1 Million & Other Top Bonuses at Betfair BingoTake home a share of £1 Million and other top bonuses all this month at Betfair Bingo.... bet365 Bingo's Top Promo Line UpWin a trip to New York and other exciting offers at bet365 Bingo this month.... William Hill Bingo's £1 Million GiveawayWin a share of £1 million at William Hill Bingo; join now to find out how.... More Stories Tags888Ladies


text:
Here's your chance to buy 3D TV for less. Hurry and Save Up to 53% Off Toshiba 3D LED HDTVs with WiFi! Each TV comes with four pairs of 3D glasses. Deal includes Free shipping
Choose from the following sizes of Toshiba 3D LED HDTVs with WiFi:
- $399 for a 32″ (32TL515U) ($849.99 list price)
- $699 for a 42″ (42TL515U) ($1,099.99 list price)
- $799 for a 47" (47TL515U) ($1,399.99 list price)
- 3D enhances movies, TV, and games
- Built-in WiFi
- NetTV with Yahoo! for internet browsing
- Full HDTV (1080p) for vibrant, detailed picture
- ClearScan 240Hz for blur-free action
- Gaming mode reduces delay between controller and TV
- Comes with four pairs of 3D glasses to add depth to Sylvester Stallone films


text:
Event Calendar
Filthy Animals Video Release Party
Tickets $10 (or $5 in zombie dress) 18+ ID Required Deepcave Records present Filthy Animals "Killin Me" Video Release Party with Fresh I.E., Triple Cyanide & Yung Kode, the Heatbag Family (ADHD, RCKR, Winnipeg's Most) and Foreign Objekts. "Killin Me" video filmed at the 2010 Winnipeg Zombie Walk directed by Ryan Cheale. UFC update to be provided throughout the evening. The Pyramid Cabaret: 176 Fort Street, Winnipeg, MB R3C 1C9 http://www.facebook.com/event.php?eid=235050443175587
- Where:
- Pyramid Cabaret
- 176 Fort St.
- 204-957-7777
- www.pyramid7.com
- When:
- Saturday, July 30, 2011 from 9:00 PM to 12:00 AM
- What:
- Concerts > Hip Hop
- Neighbourhood:
- Centre , City Centre , Downtown
Ads by Google
Event Search
View more like this
Photo Store Gallery
Ads by Google


text:
ADD in School ADD Warehouse ADDitude MagazineAll Kinds of MindsAnxiety Disorders Association of AmericaAttention Research Update Born to Explore!CHADD - Children and Adults with ADHDChild Development Center, University of California IrvineDr. Thomas E. Brown Edge Foundation Family Education Great SchoolsinsideADHD.orgKidshealth.orgMayo ClinicNational Institute of Mental Health National Resource Center on ADHD NonstimulantADHDmed.comNonverbal Learning Disorder on the WebSharpBrainsTeens with ADHDadd-adhd.orgadd.orgShire ADHD Scholarship Program
Remember Me
Forgot your password?
Haven't registered yet?
22 hours agoGreen & Gold Shop's Annual "After Thanksgiving Sale"
11/19/20142015 Athletic Hall of Fame Inductees Announced
11/17/2014Faculty Blog: Mr. Bodle, Math
11/12/2014Faculty Blog: Mr. Froelich '08, Math and Engineering
11/6/2014Faculty Blog: Ms. Good, English


text:
green coffee bean consumer report
Coffee bean - wikipedia, the free encyclopedia, A coffee bean is a seed of the coffee plant, and is the source for coffee. it is the pit inside the red or purple fruit often referred to as a cherry. even though. Which green coffee bean extract works best?, Answers to some commonly asked questions. what is chlorogenic acid? chlorogenic acid is a substance present in green coffee bean extract that has been studied and. Ftc charges green coffee bean sellers with deceiving, Ftc charges green coffee bean sellers with deceiving consumers through fake news sites and bogus weight loss claims.
"pure green coffee bean extract" results & side effects, Http://greencoffeebeanextractoz.com (click this links to check out pure green coffee bean extract customer's feedback, results and side effects.) pure. Ripoff report | pure health 100.com, green coffee bean, Pure health 100.com, green coffee bean extract complaint review: pure health 100.com, green coffee bean extract scam, ripoff! internet. Green coffee bean extract customer reviews & ratings, How does it work? as one may gather through the name of green coffee bean max, the product works fundamentally through the green coffee bean extract ingredient..
Consumer lab: green coffee bean supplements low, A new consumerlab study found that not all green coffee bean supplements, which are reported to help with weight loss, may not contain the effective compounds. Top coffee reviews | best coffee – consumer reports, Looking for the best coffee? consumer reports has honest ratings and reviews on coffee from the unbiased experts you can trust.. Green coffee beans | ebay - electronics, cars, fashion, Find great deals on ebay for green coffee beans green coffee bean extract. shop with confidence..


text:
Cancer Health Center
Nutrition Therapy
While undergoing cancer therapy, patients may experience taste changes or develop sudden dislikes for certain foods. Their sense of taste may return partially or completely, but it may be a year after therapy ends before their sense of taste is normal again. A randomized clinical trial found that zinc sulfate during treatment may be helpful in expediting the return of taste after head and neck irradiation.[39][Level of evidence: I]
Suggestions for helping cancer patients manage taste changes include the following:
- Eat small, frequent meals and healthy snacks.
- Be flexible. Eat meals when hungry rather than at set mealtimes.
- Use plastic utensils if foods taste metallic.
- Try favorite foods.
- Plan to eat with family and friends.
- Have others prepare the meal.
- Try new foods when feeling best.
- Substitute poultry, fish, eggs, and cheese for red meat.
- A vegetarian or Chinese cookbook can provide useful nonmeat, high-protein recipes.
- Use sugar-free lemon drops, gum, or mints when experiencing a metallic or bitter taste in the mouth.
- Add spices and sauces to foods.
- Eat meat with something sweet, such as cranberry sauce, jelly, or applesauce.
Xerostomia (dry mouth) is most commonly caused by radiation therapy that is directed at the head and neck.[35] A number of medications may also induce xerostomia. Dry mouth may affect speech, taste sensation, ability to swallow, and use of oral prostheses. There is also an increased risk of cavities and periodontal disease because less saliva is produced to cleanse the teeth and gums.
A primary method of coping with xerostomia is to drink plenty of liquids (25–30 mL/kg per day) and eat moist foods with extra sauces, gravies, butter, or margarine.[25,36,40] In addition, hard candy, frozen desserts such as frozen grapes, chewing gum, flavored ice pops, and ice chips may be helpful.[32] Oral care is very important to help prevent infections. Irradiation to the head and neck of a patient who has permanent dry mouth symptoms may result in reduced intake of energy, iron, zinc, selenium, and other key nutrients.[41][Level of evidence: II] Special efforts should be made to help tailor meals and snacks for individuals with xerostomia.


text:
A time dependent performance model for multihop wireless networks with CBR traffic
ABSTRACT In this paper, we develop a performance modeling technique for analyzing the time varying network layer queueing behavior of multihop wireless networks with constant bit rate traffic. Our approach is a hybrid of fluid flow queueing modeling and a time varying connectivity matrix. Network queues are modeled using fluid-flow based differential equation models which are solved using numerical methods, while node mobility is modeled using deterministic or stochastic modeling of adjacency matrix elements. Numerical and simulation experiments show that the new approach can provide reasonably accurate results with significant improvements in the computation time compared to standard simulation tools.
- SourceAvailable from: David Tipper[Show abstract] [Hide abstract]
ABSTRACT: In this paper, we develop a performance modeling technique for analyzing the time varying network layer queuing behavior of multihop wireless networks with constant bit rate (CBR) traffic. Our approach is a hybrid of a time varying adjacency matrix and a fluid flow queuing network model. Mobile network topology is modeled using time varying adja- cency matrix, while node queues are modeled using fluid flow based differential equations which are solved using numerical methods. Numerical and simulation experiments show that this new approach can provide reasonably accurate results. Moreover, when compared to the computation time required in a standard discrete event simulator, the fluid flow based model is shown to be a more scalable tool. Finally, an illustrative example of our modeling technique application is given to show its capability of capturing the time varying network performance as a function of traffic load, node mobility and wireless link quality.IEEE Transactions on Vehicular Technology 08/2014; · 2.06 Impact Factor
Conference Paper: Energy balanced chain in IEEE 802.15.4 low rate WPAN[Show abstract] [Hide abstract]
ABSTRACT: IEEE 802.15.4 Low Rate Wireless Personal Area Network (LR-WPAN) intends to provide low-power ubiquitous communications between devices. However, energy utilization by devices (or nodes) in the network often impacts the application functionality and lifetime due to limited battery capacity. For instance, in the typical multihop LR-WPAN used for data detection and monitoring, the traffic flow often converges to the data sink and such a many-to-one pattern typically results in energy imbalance. Previous research has proposed many approaches to solve this issue. However, a common limitation is about using the idealized energy model, such as "first order radio model", which is the idealized estimation for RF transmission energy cost of the node. In this paper, we develop a realistic and representative LR-WPAN RF transceiver energy model from the measured data on Chipcon CC2420 and corresponding power control policy. Further, with this energy model, we formulate an optimized energy balanced chain (OEBC) model to maximize the network lifetime. Finally, the OEBC model is applied to develop the network deployment strategy by optimizing node placement, node density and traffic flow distribution.Computing, Networking and Communications (ICNC), 2013 International Conference on; 01/2013
Conference Paper: Improving WLAN throughput via reactive jamming in the presence of hidden terminals[Show abstract] [Hide abstract]
ABSTRACT: In the area of performance analysis of wireless networks, one critical issue is the hidden terminal problem, which is considered as one of the severest reasons for the degradation of network performance. In this paper, we incorporate reactive jamming scheme with distributed coordination function (DCF) in IEEE 802.11 based wireless local area networks (WLANs) to improve network throughput in the presence of hidden terminals. In the proposed protocol, we schedule access point (AP) to broadcast jamming signal reactively to hinder the simultaneous transmission of hidden terminals. Both analytical and numerical results show that our reactive jamming based protocol can constantly improve WLAN throughput for a wide range of conditions, compared with the traditional RTS/CTS.Wireless Communications and Networking Conference (WCNC), 2013 IEEE; 01/2013
Page 1
A Time Dependent Performance Model for Multihop Wireless Networks with
CBR Traffic
Kunjie Xu, Siriluck Tipmongkonsilp
David Tipper, Prashant Krishnamurthy
Graduate Telecommunications and Networking Program
University of Pittsburgh, Pittsburgh, PA
email@example.com, email@example.com
{tipper, firstname.lastname@example.com
Yi Qian
Department of Computer
& Electronics Engineering
University of Nebraska-Lincoln, NE
In this paper, we develop a performance modeling tech-
nique for analyzing the time varying network layer queue-
rate traffic. Our approach is a hybrid of fluid flow queue-
ing modeling and a time varying connectivity matrix. Net-
work queues are modeled using fluid-flow based differential
equation models which are solved using numerical meth-
ods, while node mobility is modeled using deterministic or
stochastic modeling of adjacency matrix elements. Numeri-
cal and simulation experiments show that the new approach
can provide reasonably accurate results with significant im-
provements in the computation time compared to standard
simulation tools.
1. Introduction
Interest in multihop wireless networks, such as wire-
less mesh networks (WMN) [1], vehicular ad-hoc networks
(VANET) [2], or mobile ad-hoc networks (MANET) [3],
has increased significantly in recent years. Multihop wire-
less networks are expected to become an important part of
the communications landscape and may work in a fully au-
tonomous scenario or as an extension to an infrastructure
network. In multihop wireless networks, nodes must coop-
erate with one another to dynamically establish routes using
wireless links. Routes may involve multiple hops with each
node acting as a router. Since network nodes may move
arbitrarily, the network topology is expected to change fre-
quently and unpredictably. Hence, multihop wireless net-
works require highly adaptive protocols and efficient fail-
This research was funded in part by the US Army Research Office
under the Multi-University Research Initiative (MURI) grant W911NF-
ure recovery strategies to deal with the frequent topology
changes. Multihop wireless networks also inherit the tradi-
tional problems of wireless communications and network-
ing (e.g., asymmetric channels and signal propagation, links
that are of poor quality in comparison to wired links, hidden
terminal and exposed terminal problems, etc.), which when
combined with the other unique aspects, such as mobility
and lack of infrastructure make their design and develop-
ment challenging [1] [2] [3].
Fundamental to the design of efficient multihop wire-
less networks is the ability to estimate and predict the per-
formance of such networks. Traditionally, multihop wire-
less network performance has been evaluated using discrete
event based computer simulations. Most of the literature
adopts a steady state simulation methodology, where for a
given network scenario the simulation is conducted over a
fixed period of time, with multiple runs from different ran-
dom number seeds and collected data being averaged over
the runs. Additionally, the observations gathered during the
transient period in each run are usually eliminated to avoid
initialization bias.
A weakness of most of the literature on the performance
of multihop wireless networks is that steady state analysis
techniques are used even though transient or nonstationary
periods will occur in the network, especially after a link
or node failure. The importance of this transient behav-
ior after link/node failures has been illustrated in several
network technologies including circuit switched networks
[4], packet switched data networks [5], packet based sig-
naling networks [6], cellular networks [7], and MANETs
[8]. This work, taken together, demonstrates that the dom-
inant factor on network performance after a dynamic event
such as a link failure is the transient or nonstationary con-
gestion period. Due to the mobility of nodes and their
limited battery life, link and node failures are common in
multihop wireless networks. Thus, one would expect that
Page 2
transient/nonstationary conditions to occur often and likely
dominate the performance behavior [8]. Hence, routing
schemes, QoS mechanisms, and congestion control tech-
niques designed and evaluated via steady state analysis may
not make optimum use of network resources after a failure
or during nonstationary periods.
Simulation studies of time varying behavior for such net-
works are possible [9], though computationally difficult. To
study nonstationary behavior, the measurements of quan-
tities observed over small intervals or at specific points in
time are important. Therefore, the time average is not a
proper approach and ensemble averages are more appropri-
ate. The idea is to construct ensemble average curves of
quantities of interest across a set of statistically identical but
distinct independent simulation runs, along with the calcu-
lated confidence interval. With many such points collected
at different time instants, the behavior of the system can be
shown as a function of time. However, to assure the accu-
rate portrayal of the actual system, a large number of runs
are required resulting in large amounts of CPU time and
scalability issues. In summary, while significant progress
has been made towards developing multihop wireless net-
work protocols [1, 2, 3] and developing simulation tools
[10, 11, 12, 13] to estimate their performance, relatively lit-
tle work has appeared on performance models which cap-
ture their time varying behavior.
In this paper, we develop a new performance modeling
networks, which includes both time varying and steady state
behavior. Network queues are modeled using fluid flow
based differential equations, which can be solved by us-
ing numerical integration methods. Node connectivity, rep-
resenting topology changes, are integrated into the model
using either deterministic or stochastic based connectivity
matrix modeling techniques. Our approach is shown to be
more scalable than nonstationary discrete event simulations
while allowing the same insight into the interaction of net-
work nodes/protocols.
The rest of the paper is organized as follows. Section
II provides the details of our modeling approach. Section
III presents numerical results from both our modeling ap-
proach and for comparison standard simulation. Section IV
studies the computational time complexity of our proposed
modeling technique and gives numerical results illustrating
the advantages of our method in comparison to simulation.
Our conclusions and future works are given in Section V.
The network topology in multihop wireless networks can
change dynamically depending on the link connectivity be-
tween each node pair. When nodes in the networks are al-
lowed to move arbitrarily, it will lead to frequent changes
in the topology of the queueing network model. For that
reason, we propose a hybrid approach to approximate the
network performance using two components: (1) a time
varying adjacency matrix model to represent the network
topology and (2) a fluid flow model based set of differential
equations which model the time dependent queueing behav-
ior of each node. In developing a performance model of the
network, we start with modeling a single queue and then
generalize to a arbitrary queue in a network. We adopt a
fluid-flow based approximation technique to describe the
time varying behavior of the queue at each network node,
with the help of an approximation concept. Specifically, the
Pointwise Stationary Fluid Flow Approximation (PSFFA)
method [8] [18] [19], which models the average number in
the system at a queue by one or more nonlinear differential
equations which are derived from a pointwise mapping of
the steady-state queueing relationship and can be solved nu-
merically using standard numerical integration techniques.
2.1Network Topology Modeling
Consider a multihop wireless network consisting of M
nodes, the network topology in terms of connectivity at any
time t is modeled with a M x M adjacency matrix denoted
as A(t).
radio range which is a function of a variety of factors, such
as the distance between the nodes, antenna radiation pat-
tern, power level, geographic terrain, propagation environ-
ment, interference, receiver sensitivity, speed, etc. In gen-
eral, the range of every node is different and the connectiv-
ity among nodes can be asymmetric (i.e., aij(t) = 1 while
aji(t) = 0). Given an initial placement of the network
nodes, the dynamic network topology due to node mobility
is reflected in the adjacency matrix by changes in the aij(t)
values with time. Information about node movement and
connectivity can be determined from experimentally gath-
ered trace data, a discrete event simulation of a mobility
model (e.g., random waypoint) or stochastic/probabilistic
models of mobility effects on link connectivity [16] [17].
In the trace based approach, the data is mined for the link
connectivity information versus time.
approach, a mobility model is used to create the network
topology dynamics. Specifically, every node pair is checked
aMM(t) ...
whereaij(t) =
if node i and j are directly connected
at time t
The connectivity between two nodes is determined by their
In the simulation
Page 3
for the possible connectivity change based on their current
speeds and directions. Note, that changes in speed, direc-
tion and power level are also considered events. The event
times are placed in chronological order and as time evolves
the pair wise connectivity calculation is repeated for every
event time and the matrix is changed accordingly. In this
way, the adjacency matrix can reflect the topology change
dynamically. Note that no traffic need be generated just
the node mobility and range of the nodes, this can be ac-
complished using existing tools such as the BonnMotion
simulator [14]. A computationally simpler approach is to
model mobility by directly manipulating the elements of
the adjacency matrix according to a planned experiment or
a stochastic/probabilistic model (as shown in Section III).
Such a probabilistic model can be developed either from
the mobility model assumptions and analysis [15] or from
fitting a statistical model to data gathered from a test bed or
simulation (for example, two-state MMPP [17]).
2.2 Fluid Flow Model Background
Consider a single server first in first out queueing system
with a nonstationary arrival process, where λ(t) represents
the ensemble average arrival rate at time t. The model is de-
veloped by focusing on the dynamics of the packet queues
at the transmission link. With x(t) defined as the state vari-
able representing the ensemble average number in the sys-
tem at time t, ˙ x = dx/dt is the rate of change of the state
variable with respect to time. According to the flow conser-
vation principle, the rate of change of the average number
in the system equals to the difference between the flow in
and the flow out of the system at time t, denoted by fin(t)
and fout(t) resulting in:
˙ x(t) = −fout(t) + fin(t)
For infinite waiting space queues, the flow in equals the ar-
rival rate fin(t) = λ(t). The flow out can be related to
the ensemble average utilization of the server as fout(t) =
μCρ(t), where 1/μ refers to average packet length, C de-
fines the server capacity and ρ(t) is the server utilization.
Thus μC represents the average service rate in number of
packets per unit time. This equation can model a wide range
of queueing systems as shown in [5] and [19]. The fluid
flow equation can then be written in terms of the average
arrival rate and the departure rate as:
˙ x(t) = −μCρ(t) + λ(t)
The utilization ρ(t) in (2) depends on stochastic model-
ing assumptions of the queue under study such as traffic
arrival process and service time distribution. In general,
the exact expression of ρ(t) is difficult to determine. In
[19] we proposed the function be determined by an approx-
imation approach - matching the equilibrium point in the
differential equation at particular time instant to the cor-
responding steady state queueing theory result. To adopt
thismappingapproach, weassumethattheserverutilization
function can be approximated by the non-negative function
G(x(t)), which represent the ensemble average utilization
of the server at time t as a function of the state variable x(t).
Then (2) can be written as:
˙ x(t) = −μC(G(x(t))) + λ(t)
In general, the function G(x(t)) is nonlinear and we can
solve for x(t) in (3) using numerical methods as follows.
Given an initial condition of the state variable at time zero
as x(0) and an approximation of the arrival rate as a con-
stant λ over a small time step [0,Δt] (i.e., λ = λ(Δt/2)),
equation (3) can be solved numerically for state variable at
the end of the time interval x(Δt), which then becomes an
initial condition for the next time step [Δt,2Δt]. The ar-
rival rate for the new time step is adjusted and the procedure
is repeated for each time interval along the time horizon.
Numerical studies in [18] have shown that results from the
PSFFA model are reasonably accurate. Here we derive the
PSFFA model for the queueing system of interest beginning
with the general multiple traffic stream case.
2.3Multiple Traffic Stream Fluid Flow
Consider the case of a single queue with S differ-
ent traffic streams, each with the average arrival rate of
λ1(t),λ2(t),...,λS(t) respectively as illustrated in Fig. 1.
Figure 1. Queuing model with S traffic
The aggregate traffic can be considered as one arrival pro-
cess λT(t) =
semble average number of stream l in the system at time
t, the total average number in the system is defined as
xT(t) =?S
˙ xT(t) = −μC(G(xT(t))) + λT(t)
We note that the flow conservation principle also applies
to each traffic stream. Therefore, a state model can also
be developed for each stream with G(xl(t),xT(t)), as the
average utilization function of the link by stream l traffic, as
l=1λl(t). Let xl(t) represents the en-
l=1xl(t), and the state model in (3) becomes:
Page 4
a function of the total average number in the system xTand
the average number of stream l packets in the system xl.
˙ xl(t) = −μC(Gl(xl(t),xT(t))) + λl(t) ∀l = 1,2,...,S
Thus the transmission link can be described by a set of S
coupled state equations, each representing the traffic behav-
ior of its own stream. Next we tailor this model to the case
of periodic traffic streams.
2.4 Modeling CBR Traffic
We focus on modeling a queue with constant bit rate in-
put traffic streams and consider two cases: (1) where all
CBR streams have the same data rate and (2) when the CBR
streams have different data rates. The two cases are studied
in turn below.
Case I: Identical Sources
Consider a queuing model as in Fig. 1 where all the traf-
fic sources have the same period (although not necessarily
insynchronization)andthepacketshavethesamesize. This
model is often referred to as the S ∗D/D/1 queue. The pe-
riod of the S input streams is measured in server time units
D, and the server utilization equals to ρ = S/D which must
have ρ < 1 for stability.
Following [23] and [25], we model lack of synchroniza-
tion among the streams by assuming that the first arrival of
each flow is independently and uniformly distributed over
the first arrival period interval. Let Ltdenote the number of
customers present at time t and Qt(r) = Pr{Lt> r} is the
survival function or complementarydistribution ofthe num-
ber in the system at arbitrary instant t. Further let A(u,t)
denote the number of arrivals in an interval (u,t). As noted
in [23] the survival function can be written as:
Qt(r) =
where ps(r) = Pr{A(t − s,t) = r + s} and π0(r,s) =
Pr{system empty at t−s| r+s arrivals in (t−s,t)}. Not-
ing that the binomial distribution provides the probability of
arrivals during an interval. Then Qt(r) [25] can be written
Qt(r) =
?D − S + r
r + s
1 −s
D − s
for 0 ≤ r < S
where the first three terms in the sum represent the number
of arrivals and the rightmost term represents the probabil-
ity the system is initially empty given r + s arrivals. The
total average number in the system xT can be found using
Qt(r) [23], since the mean of nonnegative variable xTcan
be computed as xT=?S−1
?D − S + r
The above formula can be used to numerically determine
xTfor a given traffic mix (i.e., S,D,ρ ). We apply a curve
fitting approach using the (ρ,xT) data from (8) to find the
utilization function G(.). The resulting G(xT(t)) is in the
form of a polynomial (i.e., G(xT(t)) = axn
... + k) and can be substituted back into the general fluid
flow model (4).
Determining the state model for each traffic stream
l at a queue, following the approach of steady state
equilibrium matching with ˙ xT(t) = 0, from (4) and
(5), we find λT(t)= μCG(xT(t)) and λl(t)
μCGl(xl(t),xT(t)) ∀l = 1,2,...,S, respectively. Solv-
ing these equations along with G(xT(t)) determined from
data fitting, the average utilization for stream l packets,
Gl(xl(t),xT(t)) can be determined as
This can be substituted into (5) to provide the multiple traf-
fic stream fluid flow model.
Case II: Non-identical Sources
Now we consider the case where a group of sources with
different rates are multiplexed on a transmission link where
the total bit rate is less than the transmission capacity to
ensure stability. Suppose there are m types of sources with
Niof type i generating traffic with the arrival period of Di
time units, for i = 1,2,...,m. This type of queue may
be referred to as a N1D1+ N2D2+ ... + NmDm/D/1
queue. Similar to Case I, we rely on numerical analysis of
the queue length distribution to find the utilization function
G(.). Following the same approach as before, we focus on
determining Qt(r) using (6).
Determining ps(r) in (6), we note for an interval of
length s, a type i stream will generate [s/Di] arrivals
and possibly one additional arrival with probability αi =
s/Di− [s/Di]. Considering all Niof type i sources, the
total number of arrivals equals to Ni[s/Di]+kiwhere kiis
a random variable representing additional arrivals for each
traffic type with the following distribution:
r=0Qt(r) [24]. Therefore, for the
S ∗ D/D/1 queue, xTis given by:
r + s
1 −s
D − s
for 0 ≤ r < S
T+ bxn−1
G(xl(t),xT(t)) =
∗ G(xT(t))
T+ bxn−1
+ ... + k?
bsi(k) = Pr{ki= k}
? ?Ni
i(1 − αi)Ni−kfor 0 ≤ k ≤ Ni
Page 5
Let qs(k) be defined as the distribution of?kifor all m
types, it is given by:
qs(k) =
for 0 ≤ k ≤
Ni (11)
Then the probability ps(r) of r + s arrivals during time in-
terval (t − s,t) can be determined from qs(k) as:
The conditional probability of queue being idle at the be-
ginning of the interval π0(r,s) in (6) is difficult to derive.
However, bounds for probabilities Qt(r) can be obtained
from the fact that (1 − ρ) ≤ π0≤ 1, where ρ corresponds
to the server utilization?Ni/Di. Substituting in (6), we
A tighter upper bound has been derived in [26] as:
ps(k) =
qs(r + s −?
iNi[s/Di] ≤ r + s ≤?
iNi([s/Di] + 1)
have the bounds:
(1 − ρ)
ps(r) ≤ Qt(r) ≤
Qt(r) ≤
Ni− ki
Di(1 − αsi)
bsi(ki)1 −
with (x)+= max{0,x} and ds =?Ni[s/Di]. Noting
(13) or (14) to find the corresponding bounds for xT. After
that, curve fitting the data pair (ρ,xT) results in the poly-
nomial utilization function G(xT(t)), which can be substi-
tuted back into the general fluid flow model (5). The re-
sult is two fluid flow models, one providing a lower bound
and the other an upper bound. As an alternative, one can
simplify the computation by assuming homogeneous traf-
fic. For the lower bound, traffic from all sources are fixed
with period of Dmax= max{Di} and for the upper bound
the traffic period equals to Dmin= min{Di}. We can ap-
ply Dmaxand Dmininto (8) from S ∗D/D/1 to obtain the
upper and lower bounds of the data pair (ρ,xT) and then
find out the utilization function for each bound by curve fit-
ting. Once the bounding fluid models for the total traffic
flow xT are found, one can similarly find upper and lower
bounding fluid models for each traffic stream using (9).
that xT =?S−1
r=0Qt(r), one can use function Qt(r) from
2.5 Networks with Periodic Traffic
Consider a multihop wireless network consisting of M
nodes with all traffic being constant bit rate. An arbitrary
node i is shown in Fig. 2. At each node, there are M − 1
possible traffic types, sorted into M − 1 classes based on
their destinations. We assume that packets are generated at
the node i destined for node j according to a determinis-
tic process, (which can be nonstationary), with mean rate
the queueing system at node i destined for node j at time
t. We denote the average packet length with 1/μ and let Ci
denote the transmission capacity of node i. When consider-
ing the network as a whole, (5) must be modified to clearly
identify the source node i and destination node j for each
state variable xj
through intermediate nodes when a direct link is not acces-
sible. We define aij(t) in the adjacency matrix to represent
node connectivity, as described in section 2.1. Similarly, in
order to model multihop routing, we define the routing vari-
able rj
the routing algorithm, with rj
destined to node j is routed through network node k at time
t and rj
i(t). Let xj
i(t) denote the average number of packets in
i(t), as well as to model traffic being routed
ik(t) as a zero/one indicator variable determined by
ik(t) = 1 if traffic from node i
ik(t) = 0 otherwise.
flow from node 1
flow from node M
flow from node 2
flow to node 1
flow to node M
flow to node 2
Figure 2. An arbitrary node i queueing model.
Note that, the flow out of node i to node k of a particular
traffic class j will depend upon the existence of a direct link
between i and k and the routing variables for traffic class j.
Hence one must modify the flow out term in (3) to incorpo-
rate aik(t) and rj
class j traffic to node k is given by
ik(t). Specifically, the flow out of node i of
class j traffic flow out of node i to node k
= μCi(Gj
The flow of class j traffic into the node i queue will consist
of traffic generated at node i with rate γj
of class j traffic to node i from other network nodes. For
example, the flow of class j traffic into node i from node l
is given by
i(t) and the flow
class j traffic flow into node i from node l
= μCl(Gj
In interconnecting queues, the literature [20]-[22] indi-
cates that the output from a queueing system with deter-
ministic service time should be treated as a delayed input to
the next stage. This idea is applicable to our model, where
the input to the next stage is a superposition of the delayed
Page 6
input streams from the nearby nodes plus any external arriv-
ing traffic. We illustrate the concept by considering a sim-
plified two stage tandem queue model as in Fig. 3(a)-(b), let
xi(t), λi(t) and Gi(t) be the average number in the system,
total average arrival rate and average utilization at node i,
respectively. Then, λl(t) = γ1(t) is the arrival rate to the
first queue, and μCGl(t) is the departure rate from the first
queue. The departure rate then becomes the input to the sec-
ond queue with a deterministic propagation delay of service
periodDstimeunits, thatisλ2(t) = μCG1(t−Ds)+γ2(t).
We can then write a set of fluid flow equations at node 1 and
node 2, for Fig. 3(a)-(b) as:
˙ x1(t) = −μCG1(t) + γ1(t)
˙ x2(t) = −μCG2(t) + γ2(t) + μCG1(t − Ds)
node 2
(a) Original System
node 1
node 2
(b) Equivalent model
Delay = D
Figure 3. A two-node deterministic service
system with its equivalent model.
The general M nodes network hybrid model combining
fluid-flow model with routing and connectivity is obtained
by summing the flow in and out over all possible nodes:
˙ xj
i(t) = −μCi(Gj
ik(t) +
i(t) +
l(t − Ds),xT(t − Ds)))
∀i,j = 1,2,...,M
For a queue with the superposition of periodic arrival
streams, the server utilization function G(.) can be written
in the form of polynomial expression given in (9). There-
fore, the final network fluid flow model is
˙ xj
i(t) = −μCixj
T(t) + bxn−1
(t) + ... + k?
xT(t − Ds)
ik(t) + γj
i(t) +
i(t − Ds)
T(t − Ds) + bxn−1
(t − Ds) + ... + k?(aik(t)rj
∀i,j = 1,2,...,M
Given a routing algorithm, connectivity model and traffic
information, this model can be solved numerically for the
mean queue lengths as a function of time using any standard
numerical integration technique.
2.6 Additional Performance Metrics
In addition to the mean queue length versus time, other
performance metrics can be evaluated from the model. Here
for the sake of brevity we discuss estimation of the end-to-
end delay only. Typically, a packet is forwarded from the
source via a path which may include several intermediate
nodes until it reaches the destination. As a result, the end-
to-end delay is the sum of the delays experienced at each
node along the way. The delay at a node consists of the
processing time, the queuing delay, the transmission time
on the link and the propagation time over the link to the
next node. In general, the queueing and transmission delay
are the main factors.
From Little's theorem, the average number in the system
is equivalent to the product of the average arrival rate and
the average time in the system. If x denotes the average
number in the system, λ is the average arrival rate and W is
the average waiting time, then x = λW. With the assump-
tion of constant arrival rate over a small step, the change in
average waiting time can be related to the rate of change in
average number in the system˙W = ˙ x/λ. Now consider a
path P of j−1 hops from source node 1 to destination node
j (class j traffic), given by (1,2), (2,3)...(j − 1,j), where
(i,i+1) represents a link on the path, for ∀i = 1,2...j −1.
The average node delay at node i for class j traffic on link
(i,i + 1) is denoted by Wj
P can be written as WP(t) =?j−1
change of this path delay is given by:
i(t) and the total latency of path
i(t). However, as
we are interested in the time dependent behavior, the rate of
˙WP(t) =
˙ xj
according to (18), λj
i(t) can be calculated by
i(t) = γj
i(t) +
xT(t − Ds)))(aik(t)rj
l(t − Ds),
We solved the fluid flow based model, presented in the
previous section, using the fifth order Runge-Kutta numer-
ical integration routine with variable time step Δt in Mat-
lab. For comparison purposes, an equivalent discrete event
Page 7
simulation is built using OPNET 14.5 [11]. In our OPNET
model, each queue of the node is configured as a first in first
out (FIFO) queue with infinite buffer size and each traffic
stream is buffered at a different subqueue. In addition, we
use minimum hop routing for both the fluid flow model and
the discrete event simulation. The discrete event simulation
results are the average of 4096 runs using the nonstationary
simulation methodology of [9] discussed in the introduc-
A simple simulation scenario of three nodes with pre-
determined connectivity change between nodes at each time
interval during the length of simulation time as illustrated
in Fig. 4(a) - (f), is studied first. This topology is used to
evaluate the accuracy of our proposed model. In this setup,
when the direct link is no longer available, traffic must be
rerouted through relay nodes and uses some available por-
tion of the shared link capacity. We set the capacity for all
nodes Ci= 104bps with packet length 1/μ = 1250 bytes,
so that the average service rate 1/Dsis normalized to one
packet per second.
(a) t<100(b) 100<=t<200(c) 200<=t<300
(d) 300<=t<400 (e) 400<=t<500 (f) 500<=t
Figure 4. Three node network connectivity
For case I, the rate of externally arriving packets of each
node pair are set to γ2
packets per second but are not synchronized (i.e., the first
arrival from each stream is determined from a uniform [0,5]
random variable). As described in Section II.C case I, we
first compute the data pair (xT,ρ) from (8). Curve fitting
the data pair (ρ,xT), the server utilization function is deter-
mined as G(xT) = 0.0832x3
This is then used in (19) to model the network. Fig. 5
shows the results of the effect of topology change on the
average number in system and end-to-end delay for traffic
at node 1 destined for node 2. For the time interval t < 100
sec, all nodes are directly connected. Nodes go through an
initial transient period and reaches steady state. For time
100 ≤ t < 200 sec, the link between node 1 and 3 breaks
and traffic going through this link has to go through the re-
lay node 2. But traffic x2
terval 300 ≤ t < 400 sec, the link between node 2 and
node 3 breaks, leading to traffic re-routing and an increase
in the number of x2
server utilization of node 1, the average queuing time of
1= γ3
1= γ1
2= γ3
2= γ1
3= γ2
3= 0.2
T− 0.4353x2
T+ 1.0843xT.
1is not affected. For the time in-
1packets in the system. Due to higher
each packet at node 1 increases and we can see the rise in
2. During the time t ≥ 500 sec, link 1-2 breaks and x2
has to go through the relay node 3 to reach the destination.
Hence, the end-to-end delay consists of propagation delay
in link 1-3 and link 3-2 as well as the queueing delay at node
1 and node 3. The behavior of the other network nodes and
traffic streams are similar and not shown here for the sake
of brevity.
0100 200300 400500 600
t (second)
Average Number of Packets
Hybrid Modeling
0 100200 300400500 600
t (second)
End−to−end Delay (second)
Hybrid Modeling
Figure 5. Average number of packets and
end-to-end delay of x2
1with S ∗D/D/1 queue.
Next we tested the performance of the fluid flow model
with case II, the rates of externally arrivals are set as: γ2
0.16 γ3
packets per second. The baseline case when all links are
working results in each node being a N1D1+ N2D2/D/1
queue with D1 = 1/0.16 = 6.25 and D2 = 1/0.2 = 5.
Following the procedure described in section II.D case II,
we calculate the data pair (xT,ρ) for the lower bound from
the left hand term in (13) and the upper bound from (14).
The resulting lower and upper bounds utilization functions
are Glower(xT) = −63.5754x3
and Gupper(xT) = 0.2061x3
utilization functions are then used in (19) to form two mod-
els of the network. Fig. 6 shows the behavior of the traffic at
node 2 destined for node 3 (i.e., x3
are connected through direct link, the bounds are tight, but
when the direct link breaks, a wider gap occurs between
bounds. The first reason is that the server utilization ρ of the
1= 0.2 γ1
2= 0.16 γ3
2= 0.2 γ1
3= 0.16 γ2
3= 0.2
T+ 49.7702x2
T− 7.8764xT
T+1.1257xT. The
2). Here, while all nodes
Page 8
relay node becomes higher so that the lower bound gener-
ated by (13) drops off. Secondly, (13) does not make use of
any information of the kicombination to tighten the bound.
Another way to possibly reduce the gap between bounds is
by assuming homogeneous traffic, as discussed in section
2.4 case II and as implemented in the next scenario.
0 100 200300 400 500 600
t (second)
Average Number of Packets
Hybrid Modeling
0 100200300400 500600
t (second)
End−to−end Delay (second)
Hybrid Modeling
Figure 6. Average number of packets and
end-to-end delay of traffic destined for node
3 at node 2
Next we consider a five node network with the random
waypoint mobility (RWM) model. Recently in [16] and
[17], it is shown that the RWM model link connectivity
can be modeled as a two-state Markov process with on-off
(connected-disconnected) transition, with both link on and
off durations following exponential distributions. This link
connectivity model can reproduce the average link stability
statistics of RWM model without requiring a detailed node
mobility simulation. In this experiment, each link is expo-
nentially distributed on duration with a mean of 50 seconds
and off duration with a mean of 10 seconds. The link ca-
pacity and packet length remain the same as ones in the
three node network scenario. The externally arrival rates
are assigned as: γ3
0.22 γ5
ing behavior of the network, we randomly select the time
interval [2100 2200] from a 6000 seconds of the total ex-
periment duration. The link connectivity as determined by
the RWM for the time interval is shown in Fig. 7. In the
following discussion, we focus on the traffic from node 1
1= 0.25 γ5
1= 0.16 γ5
2= 0.18 γ5
4= 0.25. In order to illustrate the typical time vary-
destined for node 5 and all the routes of class 5 traffic going
through node 1 are marked by dotted lines in the figure.
(a) 2100<=t<2115
(b) 2115<=t<2124(c) 2124<=t<2131
(d) 2131<=t<2136(e) 2136<=t<2161 (f) 2161<=t<2166
(g) 2166<=t<2177
(h) 2177<=t<2185(i) 2185<=t<=2200
Figure 7. Typical RWM connectivity scenario
for five node network.
Fig. 8 shows the average number in system x5
end-to-end delay of the packets from node 1 destined for
node 5 during the time interval [2100 2200]. Initially, ev-
ery packet goes through the direct link (1-5). Then, during
the time interval 2124 ≤ t < 2136 sec, a large transient
increase in x5
(4-5) breaks, the traffic x5
reach the destination. This event also results in the increase
of end-to-end delay of the packets x5
utilization of node 1. At t = 2136 sec link (4-5) recovers
and the x5
Starting from t = 2161 sec, link (1-5) breaks and the rout-
ing protocol redirects the packet x5
5. Notice that at t = 2177 sec the link (3-5) is disconnected
and it causes the x5
3 to node 2 resulting in a further increase in the end-to-end
delay. At t = 2185 sec the direct link (1-5) is working again
and the traffic is rerouted over the direct link resulting in a
decrease in the delay.
The fluid flow numerical results presented in Fig. 8, are
calculated by assuming "homogeneous traffic" instead of
(13) (14). For the lower bound, all sources are assumed
to have homogeneous traffic with the period of Dmax =
max{Di} = 1/0.16 = 6.25, while for the upper bound,
the homogeneous traffic becomes Dmin = min{Di} =
1/0.25 = 4. Following the procedure in Section II.D
case I, we obtain the utilization function for both bounds
as Glower(xT) = 0.0889x3
Gupper(xT) = 0.0743x3
are used in (19) to form the two bounding models of the
network. From Fig. 8, we notice that the lower and upper
1and the
1occurs due to traffic rerouting, when the link
4needs to go through node 1 to
1, because of the higher
4traffic is rerouted back to the direct link (4-5).
1through node 3 to node
1traffic to take one more hop from node
T− 0.4496x2
T− 0.4159x2
T+ 1.0706xT,
T+ 1.0993xT, which
Page 9
bounds are tighter than ones in three node network scenario.
Hence, the "homogeneous traffic" approach might be better
choice than (13) and (14), when the?m
iNiDi/D/1 queue
has close arrival rates.
2100 2110212021302140
t (second)
2150 2160 21702180 21902200
Average Number of Packets
Hybrid Modeling
21002110 21202130 2140
t (second)
End−to−end Delay (second)
Hybrid Modeling
Figure 8. Average number of packets and
end-to-end delay of traffic at node 1 destined
for node 5.
4.1 Complexity Analysis
The proposed hybrid modeling approach is composed of
a fluid flow queueing model together with a time varying
connectivity matrix. At each time interval, network met-
rics are evaluated by integrating a set of fluid flow model
based differential equations with a specific connectivity ma-
trix. Similarly to other areas of complexity theory, the ex-
act number of arithmetic operations required for solving the
differential equations with one step time by Runge-Kutta
algorithm is hard to determine but an upper bound on the
complexity order can be obtained.
Let dt refer to the time step size of solving the differ-
ential equations and T be the length of the time interval of
interest. Then T/dt represents the number of total times to
solve the set of differential equations. Let K denote the av-
erage time to execute one arithmetic operation on a CPU.
Following [27], C(n,p,α) denotes the upper bound on the
number of arithmetic operations required within one step
time, so that n differential equations can be solved by a
p−th order explicit Runge-Kutta algorithm with maximum
error e−α. According to the expression for C(n,p,α) in
[27], with the pre-defined value of p and α, C increases lin-
early with n. As a result, only considering the varying of n
in K ·(T/dt)·C(n,p,α), the computation time complexity
of our hybrid modeling TCHis upper bounded by O(n).
For an M-node wireless network, regardless of the number
of externally arriving traffic flows, the number of differen-
tial equations n is M(M − 1). Therefore, the upper bound
of TCHis O(M(M − 1)).
4.2 Comparison by Sample Networks
To further evaluate the complexity we numerically de-
termined the computational time for a set of sample net-
work implementations. We constructed both OPNET dis-
crete event simulation and the proposed hybrid fluid flow
model for network settings of three nodes, four nodes, five
nodes and thirteen nodes networks, as shown in Fig. 9. The
numerical results are shown in Table I when both hybrid
modeling and simulation were run on a laptop with Intel
T7400 2.16GHz Duo-Core Processor with 2GB memory.
For the discrete event simulation the time given is the to-
tal time to execute 4096 runs. This result shows that for the
hybrid modeling, the numerical computation time is propor-
tional to the number of differential equations. However, the
computation time required to complete the OPNET discrete
event simulation increases with the total number of events
which is a complex function of the amount of traffic, topol-
ogy changes and accuracy desired.
(a) 3 Nodes(b) 4 Nodes (c) 5 Nodes(d) 13 Nodes
Figure 9. Topologies of sample networks
Table 1. Computation Time Comparison (in
# # Flows of
# Diff.
Page 10
In this paper, we propose a performance modeling tech-
nique to represent time varying behavior of multihop wire-
less networks with CBR traffic, using time varying connec-
tivity matrix modeling and numerical method based queue-
ing analysis. Network queues are modeled using fluid flow
based differential equations and solved using numerical in-
tegration routines, while topology change is integrated into
the connectivity matrix using deterministic or probabilistic
modeling techniques. The proposed hybrid modeling ap-
proach can generally be applied to a wide range of queue-
ing systems. Numerical results using the proposed model
have been given in comparison with results from traditional
discrete event simulations. The computation time required
by both approaches is also shown side by side. We be-
lieve that this hybrid modeling approach is a proper tool
for evaluating the time-varying behavior of multihop wire-
less networks. With the computation time saved from the
fluid flow based hybrid modeling method, it is a tremendous
gain in flexibility for modeling complex networks. Future
work includes validating the model with testbed measure-
ment results and developing additional features (e.g., multi-
rate links) to increase the fidelity of the model.
[1] I. F. Akyildiz and X. Wang, "A survey on wireless mesh net-
works", IEEE Communications Magazine, vol. 43, no. 9, pp.
S23-S30, September 2005.
[2] H. Moustafa and Y. Zhang, Vehicular networks, Techniques,
Standards, and Applications, CRC Press, 2009.
[3] I. Chlamtac, M. Conti, and J. Liu, "Mobile Ad Hoc
Networking: Imperatives and Challenges", Ad Hoc Net-
works(Elsevier), vol. 1, no. 1, pp. 13-64, 2003.
[4] D. Logothetis and K. Trivedi, "The Effect of Detection and
Restoration Times for Error Recovery in Communications
Networks", Journal of Network and Systems Management,
vol. 5, no. 2, pp. 173-196, 1997.
[5] D. Tipper, J. Hammond, S. Sharma, A. Khetan, K. Balakr-
ishnan and S. Menon, "An Analysis of the Congestion Ef-
fects of Link Failures in Wide Area Networks", IEEE Jour-
nal on Selected Areas in Communications, vol. 12, no.1, pp.
179-192, 1994.
[6] M. Rumsewicz and D. Smith, "A Comparison of SS7 Con-
gestion Control Options During Mass Call-in Situations",
IEEE/ACM Transactions on Networking, vol. 3, no.1, pp.
1-9, Feburary 1995.
[7] D. Tipper, C. Charnsripinyo, H. Shin, and T. Dahlberg, "Sur-
vivability Analysis for Mobile Cellular Networks", in Proc.
Communication Networks and Distributed Systems Model-
ing and Simulation Conference San Antonio, Texas, January
[8] D. Tipper, Y. Qian and X. Hou, "Modeling the Time Varying
Behavior of Mobile Ad-Hoc Networks", in Proc. 7th ACM
International Symposium on Modeling, Analysis and Simu-
lation of Wireless and Mobile Systems, October 2004, pp. 12
- 19.
[9] W. Lovegrove, J. Hammond, and D. Tipper, "Simulation
Methods for Studying Nonstationary Behavior of Computer
Networks", IEEE Journal on Selected Areas in Communica-
tions, vol. 8, no. 9, pp. 1696-1708, 1990.
[10] Glomosim Tool, http://pcl.cs.ucla.edu/projects/glomosim/.
[11] OPNET Simulation Tool, http://www.opnet.com/.
[12] NS-2 Simulation Tool, http://www.isi.edu/nsnam/ns/.
[13] QualNet Simulation Tool, http://www.qualnet.com/.
[14] BonnMotion, Mobility scenario generation and analysis tool
[15] T. Camp, J. Boleng, and V. Davies, "A Survey of Mobility
Models for Ad Hoc Network Research", Wireless Commu-
nication & Mobile Computing (WCMC): Special issue on
Mobile Ad Hoc Networking: Research, Trends and Applica-
tions, vol. 2, no. 5, pp. 483-502, 2002.
[16] T. Lin and S. F. Midkiff, "Mobility versus Link Stability
in the Simulation of Mobile Ad Hoc Networks", in Proc.
Communication Networks and Distributed Systems Model-
ing and Simuation Conference (CNDS), January 2003.
[17] S. K. Hwang and D. S. Kim, "Markov Model of Link Con-
nectivity in Mobile Ad Hoc Networks", Telecommunication
System, vol. 34, no. 1-2, pp. 51-58, February 2007.
[18] D. Tipper and M. K. Sundareshan, "Numerical Methods for
Modeling Computer Networks under Nonstationary Condi-
tions", IEEE Journal on Selected Areas in Communications,
vol. 8, no. 9, pp. 1682-1695, December 1990.
[19] W. Wang, D. Tipper and S. Banerjee, "A Simple Approxi-
mation for Modeling Nonstationary Queues", in Proc. IEEE
INFOCOM, vol. 1, 1996, pp. 255 - 262.
[20] M. J. Neely, and C. E. Rohrs, "Equivalent models and anal-
ysis for multi-stage tree networks of deterministic service
time queues", in Proc. the 38th Annual Allerton Conference
on Communication, Control, and Computing, October 2001.
[21] M. J. Neely, "Exact Queueing Analysis of Discrete Time
Tandems with Arbitrary Arrival Processes", in Proc. IEEE
International Conference on Communication (ICC), vol. 4,
2003, pp. 2212-2225.
[22] M. J. Neely, "Equivalent Models for Queueing Analysis of
Deterministic Service Time Tree Networks", IEEE Transac-
tion on Information Theory, vol. 51, no. 10, pp. 3576-3584,
[23] J. W. Roberts, and J. T. Virtamo, "The Superposition of Pe-
riodic Cell Arrival Streams in an ATM Multiplexer", IEEE
TransactiononCommunications, vol.39, no.2, pp.298-303,
[24] Elise T. Lee and John Wang, Statistical Methods for Survival
Data Analysis, New York: John Wiley and Sons, 1992.
[25] Piet Van Mieghem, Performance Analysis of Communica-
tions Networks and Systems, Cambridge University Press,
[26] J. T. Virtamo and J. W. Roberts, "Evaluating Buffer Require-
mentsinanATMMultiplexer", inProc.IEEEGLOBECOM,
vol. 3, November 1989, pp. 1473 - 1477.
[27] A.G. Werschulz, "Computational complexity of one-step
methods for systems of differential equations", Math. Com-
put., vol. 34, no. 149, pp. 155-174, 1980.