text:
# Practice Test Quesitons

by AznBoi
Tags: practice, quesitons, test
 P: 471 My work, my answers are wrong obviously. 18. $$U_{E}=\frac{kq1q2}{d}$$ -- I substituted the electric force with the work equation to get this. 25. Q=mL, Q=mcT . I combined these to get mL=mcT, stuck from there. 47. F=q(v x B), v=F/qB, F=mv^2/r I combined these equations to get: mv/r=qB and solved for v and I then I just guessed. 48. Why is the answer D?? I know that it has something to do with lenz's law but I only know how to apply that law for magnets moving with either North or South pole. (If a north pole of a magnet moves towards the wire the induced current is counter clockwise right? If the south pole moves into the wire it is clock wise?)-- Is this right? Thanks for your help guys! =]
 HW Helper P: 508 Sorry we are not giving answers as such. You may get hints for your doubts and confusions only. Show your approach in case not getting the correct answers.
 P: 471 Oh, I just posted the picture first to see if it worked lol. Anyways, my attempts are on the board! Do you want me to post the answers too? I have the answer key btw, just not the solutions.
HW Helper
P: 508

## Practice Test Quesitons

Is the diagram is given? Should be, otherwise what is Q? what about the position of the point P?
P: 471
 Quote by mukundpa Is the diagram is given? Should be, otherwise what is Q? what about the position of the point P?
Yeah, I realized that lol. I forgot to include the picture because I got 17 right. So for 17, all I did was add the two electric field vectors (one to the left and one down) to get the resultant vector which is (c) right? Thanks.
 HW Helper P: 508 Now it is clear. There are two charges Q both at a distance d from the third corner of the square. Find potential V at that point due to both Q charges (Potential is a scalar quantity) then multiply q and V.
 HW Helper P: 508 For the next heat is required to first increase the temperature of ice up to the melting point then latent heat to melt and then to increase temperature of water.
 HW Helper P: 508 For the next you got the relation for v. Put the value of e/m for proton and probable values of B and r and will get the order of the velocity.
P: 471
 Quote by mukundpa Now it is clear. There are two charges Q both at a distance d from the third corner of the square. Find potential V at that point due to both Q charges (Potential is a scalar quantity) then multiply q and V.
So how do you find the potential v at the point? I know that $$V=\frac{U_{e}}{q} =Ed$$
I don't get what you mean by then multiply q and v.
 HW Helper P: 508 The potential at that point will be KQ/d due to each charge Q so what is the total potential? and what is the potential energy?
P: 471
 Quote by mukundpa The potential at that point will be KQ/d due to each charge Q so what is the total potential? and what is the potential energy?
OKay, so $$\frac{kQ}{d}+\frac{kQ}{d}=2\frac{kQ}{d} *q= 2k\frac{qQ}{d}$$? So how do you know that you need to add the potential differences rather than just the potential energies? You can do it either way right? So do you just add them because they are a scalar? Is there any time where you need to subtract them? (mabye when the charges are opposite?) So if the quantities are scalar you just add them and if they are vectors you need to use pythagorean or trig right?
 HW Helper P: 508 Going in the right direction.

 Related Discussions Introductory Physics Homework 5 Introductory Physics Homework 4 Linear & Abstract Algebra 3 Introductory Physics Homework 2


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## Introduction

We have more than 56.61% of the world population living in urban areas in 2021, and this number is projected to be 68% by 20501, which leads to various mobility challenges, e.g., traffic congestion and energy consumption2,3,4. According to an analysis, drivers lost an average of 99 h due to congestion in 2019. The commuters in the New York City suffer from an annual delay of 102 h with a \$1594.75 cost of congestion per driver in 20215.

However, understanding long-term travel delay evolving patterns is extremely challenging because (i) travel delay happens in different modalities, e.g., subway, taxi, bus and personal cars, with implicated coupling, and (ii) long-term travel delay experiences spatial and temporal dynamics (e.g., city development, policy changes) under various contexts. More importantly, long-term multi-modal travel delay is difficult to model without explicated data.

Recently, the ubiquity of GPS devices and the upgrades of transportation infrastructures have led to unprecedented data for human mobility modeling including travel delay6,7. In particular, modern cities have been equipped with sensor devices in transportation systems to track and dispatch vehicles. Previous work has studied human mobility or travel delay based on real-world data such as cellphone data8,9,10,11,12,13,14, taxicabs15, buses16. These models have good performances when they are used to understand modal-specific mobility patterns and short-term travel delay, e.g., many papers using large-scale cellphone data6,8 to study daily commuting patterns. However, they cannot be used to understand long-term multi-model travel delay, e.g., cross-modality effect, since cellphone data do not have explicit transportation modality, e.g., subway, car, bus, and taxi.

In this paper, based on the smart city initiative of Chinese city Shenzhen17, we are working with Shenzhen Transportation Committee to access 5-year mobility data for major transportation modalities in both aboveground and underground transportation systems in Shenzhen for a data-driven transportation study. It enables us to analyze evolving mobility patterns and systematic evaluation in a long-term period for multiple modalities in a modern city Shenzhen with high-speed city development. Based on this data access opportunity, we conduct a measurement case study called mRhythm for urban travel delay measurement and understanding for Shenzhen long term transportation planning. To best of our knowledge, this is the first systematical data-driven measurement for travel delay based on large-scale, long-term, and cross-modality mobility data. mRhythm advanced the state-of-the-art works by providing several in-depth observations and causality analyses on long-term travel delay with the interaction of two major mobility modalities, i.e., aboveground systems including cars, taxis, and buses, and underground system including subways. In particular, we summarize our major findings in terms of 7 observations as follows:

• Long Term Individual Modality Evolving Based on our study from 2013 to 2017 of Shenzhen, we provide causality analyses for (1) one expected Observation 1 the travel delay and variance increase each year for both aboveground systems (including cars, taxis, and buses) and underground system (including subways) (2) two unexpected observations: Observation 2 The aboveground systems have a slow-down increase trend of travel delay compared to the underground systems, which means the rate of increase is higher for the underground systems than the aboveground systems; Observation 3 The underground systems have a lower increased delay overall compared to the aboveground systems. More importantly, we provide in-depth analyses of 5-year census data including various factors, such as subway passengers, car numbers, population, length of subway systems and road networks, to explain our results.

• Cross-Modality Impact Analyses We made two new observations on how infrastructure upgrades of the underground system and the aboveground system can impact each other: Observation 4 The aboveground system infrastructure upgrades (e.g., new highway) increase the underground system travel delay; Observation 5 The underground system infrastructure upgrades (e.g., new subway lines) slows down the aboveground system travel delay increase. More importantly, we rigorously test the statistical significance of these observations and provide a case study for each of them to validate their representativeness.

• Impact of Factors We study the impact of five major contextual factors on travel delay including population, temporal, spatial, weather, and social event. We made two new observations. (1) Population: Observation 6 The underground system travel delay decreases with higher population (from 15.5% delay in regions with 10K-20K population to 10.4% in regions with 50K–60K population); whereas the aboveground system travel delay increases with higher population (from 8% delay in regions with 10K–20K population to 28% in regions with 50K–60K population). (2) Temporal: Observation 7 The underground system travel delay decreases during peak hours (from 18% delay in off-peak hours to 13% delay in peak hours); whereas the aboveground system travel delay increases during peak hours (from 35% delay in off-peak hours to 50% delay in peak hours).

## Results

### Individual evolving patterns

#### Quantitative results

The box distribution of all trips’ delay is used where the top and bottom of each box are the 25th and 75th percentiles; the middle red lines are the median values; the top and bottom of each black dash lines indicate the maximal and minimal values. Figure 1a, b show the delay ratio distributions in underground systems (i.e., Subway) and aboveground systems (i.e., combining taxi, bus, and PV) from 2013 to 2017 where we made three observations as follows.

Observation 1 in Fig. 1: For both underground and aboveground, both travel delay and variance increase each year We analyze Shenzhen census data, which shows the high-level statistics about the mobility demand/supply and population change. We process the census data from 2011 to 2016 and normalize all absolute values to relative differences from the values of the first year, i.e., 2011, to show evolving patterns of travel demand and supply. Increasing Overall Demand Figure 2a gives Shenzhen Travel Demand by the number of passengers for subway; the number of personal vehicles (i.e., cars); Shenzhen citywide permanent population. We found that (1) the permanent population increases from 10.47 million to 11.91 million (13.8%); (2) the number of cars increases from 1.98 million to 3.23 million (63.3%); (3) the annual use of subway passengers increases from 0.4 billion to 1.2 billion (177.1%). Decreasing per-capita Supply Figure 2b shows Shenzhen Travel Supply by the length of roads per capita; the length of subway systems (in terms of km) per capita. We found that even increasing in the absolute length, both travel supply for both aboveground system and underground system decrease per capita due to increasing population and travel demand as shown in Fig. 2a. A combination of the increasing overall demand and decreasing per-capita supply leads to our observation.

Observation 2 in Fig. 1: The aboveground systems have a slow-down delay increase compared to the underground system To explore the reason, we refer to Fig. 2a where we found that the increase of cars slows down from 2015. We further explore to find out that to control the increase of personal cars and alleviate the traffic congestion, from 2015, the Shenzhen government implemented a license lottery policy on personal cars18. In the license-plate lottery policy, residents submit applications for vehicle license plates each year but only certain number of applications will be approved. Therefore, the increasing speeds of personal cars became much slower since 2015. Since personal cars account for the major aboveground system delay, its slower car increase leads to our observation “the aboveground system has a slow-down delay increase”.

Observation 3 in Fig. 1: The underground system has lower increased delay overall compared to the aboveground one To explore the reason, we refer to Fig. 2b where even both the underground system and aboveground system have decreasing per-capita supply, the underground system supply decreasing rate is much lower than that of aboveground system, due to the fast building of Shenzhen Subway System (i.e., increasing from 178.341 to 285.528 km in these 5 years). As a result, even though (1) the underground system has a strongly increasing demand (177.1%) and (2) the aboveground system has an almost-stopped increasing demand (due to license lottery policy, Shenzhen only have 2.2% more registered cars from 2014 to 2016), the underground system’s overall increase delay is still lower than the aboveground system. It might suggest that increasing supply is better than controlling demand.

#### Statistic significance of observation 1, 2, and 3

To validate the statistical significance of data for the above three observations, we put the average delay of all origin-destination pairs in a year in a vector, and then report the test results of the statistical difference between the delays of two consecutive years. Table 1 shows the results of two statistical tests, for each cell, the shadowed background means it is statistically significant in Mann–Whitney U test19 and the value in the cell is the $${\mathscr{A}}$$ measure in Vargha–Delaney20. We found that all travel delay differences between consecutive years from 2013 to 2017 are statistically significant by both two tests. The $${{\mathscr{A}}}$$ measure confirms the travel delay increases with time in the city, i.e., $${{\mathscr{A}}} > 0.5$$. We observed a relatively smaller number in 16–17 when comparing ABOVE with UNDER, the potential reasons are increasing demand of UNDER, while the travel delay for ABOVE has a relatively small number due to car policy, a relatively larger baseline of delay for ABOVE in 2016, and upgrade of ABOVE road networks.

### Cross-modal evolving patterns

For a rigorous cross-modal investigation, we study the impact of the aboveground system and the underground system infrastructure upgrades (e.g., new roads or new subway lines) on travel delay in two categories of areas: (1) Test areas (Test): city areas covered by the infrastructure upgrades based on our spatial partition. (2) Control areas (Control): city areas not covered. We calculate population distribution, delay ratio, and ratio increase speed in the test areas before infrastructure upgrades, and then we select control areas with similar features.

A travel delay ratio is defined with five attributes in Eq. 3 in both underground and aboveground systems. With the same $$\theta$$ and temporal partition, we apply a spatial alignment on the two systems to study the cross-modal impact under the same spatio-temporal dimension. Specifically, we map both the underground system and the aboveground system partitions into 497 administrative regions released by government based on the their overlap areas.

#### Impact of aboveground system infrastructure upgrades

We collect data about the aboveground system infrastructure upgrades (e.g., road open time) by analyzing OpenStreetMap data21 on social media. We found 653 km of roads were constructed and taken into services during 2013 and 2017, i.e., 6015 km of total road length at the beginning of 2013, and 6668 km of total road length at the end of 2017.

Citywide Trend To compare the impact of aboveground system infrastructure upgrades (i.e., new roads) on travel delay in both aboveground and underground systems, Fig. 3 presents mean and standard deviation of delay ratio increase, i.e., the absolute delay ratio difference, during 5 years in the two groups.

Observation 4 in Fig. 3a: The aboveground system infrastructure upgrades increase the aboveground travel delay When we compare test areas with control areas. Based on the locations of the aboveground system upgrade, we found that they mostly happen in suburban areas since the downtown areas are well-developed and out of space for new roads. As a result, these the aboveground system upgrades enable residents in suburban areas to take new roads to transfer to subways to go to downtown, which leads to increased the underground system travel delay in test areas. Based on results in Fig. 3b, we found some expected results: the aboveground system upgrades decrease the aboveground travel delay. This is an obvious observation since new roads decrease both travel distance in connected areas and travel volumes on existing roads.

Statistical Significance of Observation 4 We conduct U-test and A-test on different origin-destination pairs and the results are reported in Table 2. The shadowed cells indicate the travel delay differences are statistically significant with U-test. The number in the table is $${{\mathscr{A}}}$$ measures of A-test. The results show the aboveground system upgrades have (1) a positive impact on the aboveground system delay, e.g., the aboveground system delay in Test Area decreases from 0.71 to 0.33 while the aboveground system delay in Control Area increases from 0.69 to 0.78; (2) a negative impact on the underground system delay, e.g., the underground system delay in Test Area significantly increases from 0.61 to 0.79 while the underground system delay in Control Area slightly increases from 0.65 to 0.68.

A Case Study of Aboveground System Upgrades We take a major highway (Guangshen Yanjiang Expressway) connecting Shenzhen airport, residential areas, and CBD areas for measurement, which was open at the end of 2013.

Figure 4a shows the delay comparison for the underground system between the Test areas (impacted by the new highway) and Control areas (not impacted by the new highway) one month before and after this new highway was put into services. Similarly, Fig. 4b shows the travel delay comparison for the aboveground system.

(1) As shown in Fig. 4a, this highway significantly increases the underground system delay in the Test Area (from 18 to 24%) while the underground system delay in the Control Area only slightly increases (from 20 to 21%). This is because this highway (far-reaching to remote areas) brings more passengers for two major subway stations at one end of the highway, leading to increase the delay in these stations. This result is consistent with our Observation 4 on citywide trend. (2) As shown in Fig. 4b, this highway decreases the aboveground system delay in the Test Area (from 22 to 18%) while the aboveground system delay in the Control Area significantly increase (from 23 to 36%). The new highway directly decreases the travel time in the aboveground system by decreasing the travel distance and improving the traffic conditions. This result is consistent with our Observation 5 on citywide trend.

#### Impact of the underground infrastructure upgrades

In Shenzhen, three subway lines and 68 stations were added to the subway system in 2016 and 2017.

Citywide Trend To compare the impact of the underground system infrastructure upgrades (the underground system upgrade hereafter, i.e., new stations) on travel delay in both systems, Fig. 5 shows the delay ratio increase, i.e., the absolute delay ratio difference, during 5 years in the test areas (impacted by the underground system upgrades) and control areas (not impacted by the underground system upgrades but with similar demographic and geographic features). Since the aboveground system upgrade only happens in 2016 and 2017, the delay increases in 2014 and 2015 in test areas are 0.

Observation 5 In Fig. 5a, an expected observation is that the underground system upgrades decrease travel delay in the underground system by 14% (absolute difference) due to increased underground supply. Figure 5b: The aboveground system infrastructure upgrades slows down the aboveground system travel delay increase From 3.5 to 2%, even though the travel delay still increases in test areas. We found most underground system upgrades happen in downtown areas with high travel demand. The underground system upgrades decrease travel demand in the existing aboveground system and lead to lower traffic increase in the aboveground system. This is also supported by the previous literature outcomes such as a mismatch between demand increase and travel infrastructure upgrades22,23,24.

Statistical Significance of Observation 5 We further measure the difference by the two tests, and their results are reported in Table 3. The shadowed cells show the travel delays are statistically significant by U-test. The values of $${{\mathscr{A}}}$$ measure show underground upgrades have (i) a positive impact on the aboveground travel delay, e.g., the $${{\mathscr{A}}}$$ measure of aboveground travel delay in Test Areas slows down from 0.68 to 0.53 while the $${\mathscr{A}}$$ measure of aboveground travel delay in Control Areas increases from 0.66 to 0.71; (2) a positive impact on the underground travel delay, e.g., the $${\mathscr{A}}$$ measure of underground travel delay in Test Areas decreases from 0.61 to 0.28 while the $${{\mathscr{A}}}$$ measure of underground travel delay in Control Areas increases from 0.61 to 0.63.

A Case Study of Underground System Upgrades We investigate the impact of subway line NO.7 opened in 2016, which has a length of 30.1 km and includes 27 stations. For the underground system, we study how the new stations influence travel delays of overloaded stations. Figure 6a shows the travel delay comparison for the underground system. Figure 6b shows the travel delay comparison for the aboveground system between Test areas (impacted by the new subway line) and Control areas (not impacted by the new subway line) one month before and after this new subway line was taken into services.

(1) As shown in Fig. 6a, this new subway line decreases underground delay in Test areas significantly (from 36 to 18%) while the underground system delay in control areas increases slightly (from 19 to 20.6%). This is because the subway line passes through central business areas and is connected with 6 existing subway lines. It reduces passengers in existing stations, reduce the travel distance and transfer time. The result is consistent with our Observation 6 on citywide trend. (2) As shown in Fig. 6b, the new subway line slows down the travel delay increase in the Test areas (0.9% delay ratio increase compared with 3.2% delay ratio increase in Control areas). This is because more passengers choose the subway and it slows down the passenger demand increase in the aboveground systems. The result is consistent with our Observation 5 on the citywide trend.

### Contextual factors

We measure the impact of five contextual factors on delay ratio of the underground system (i.e., subway) and the aboveground system (i.e., car, bus, taxi), i.e., population, temporal, spatial, weather, social event, and West Texas Intermediate (WTI) crude oil price.

(1) Population

Population distribution is one of the most important and unexpected factors for travel delay. For the underground system, we map the population to stations based on the walking distance in a non-overlapping partition where the average distance between adjacent stations in the subway system is 1.16 km, so we set the walking distance as half of the average distance, i.e., 0.58 km, which leads to the walking area of $$1.05\,{\text {km}}^2$$25. 78.4% of regions in the coverage areas of the subway system have more than 10,000 population because the subway system covers the most downtown areas. For the aboveground system, we map the population to grids and investigate the relationship between population and delay at the grid level. The grid size we investigate is $$1.37\,{\text {km}}^2$$. 77.1% of grids have less than 10,000 population. In Fig. 7a, b based on different populations on the X-axis, we show both the ratio of regions among all regions (Left Y-Axis) and average the underground system delay in these regions (Right Y-axis). Observation 6 the underground travel delay decreases with the higher population; whereas the aboveground system travel delay increases with the higher population. This is mainly because of the different flexibility of underground system and the aboveground system supply, even with the same increasing demand. For the underground system in high population regions, both higher train frequency and denser subway system deployment are used for higher the underground system supply per passenger in populous areas. However, for the aboveground system, a higher the aboveground system supply is not possible in populous regions since the space for the aboveground system infrastructure upgrades (e.g., new road) is limited in the populous regions. Another minor observation is that the degree of the aboveground system travel delay increasing is smaller in grids with more than 20,000 population. This may be because the dense regions (e.g., downtown CBD) have better road structures.

(2) Temporal Fig. 8 presents travel delay during one day in UNDER and ABOVE system. Observation 7 the underground system travel delay decreases during peak hours (7 am to 9 am and 4 pm to 8 pm); whereas the aboveground system travel delay increase during peak hours. For example, there are a lower travel delay in the underground system (around 13% on average) and a higher travel delay in the aboveground system (around 50% on average). For the underground system, the subway system sends trains more frequently in peak hours as shown in Fig. 8a, i.e., the 5-min time interval in the peak hours and the 8.5-min time interval in the off-peak hours26. Sending trains more frequently reduces the waiting time significantly while increases the operational cost. For instance, a subway line with 1 h of total travel time requires at least 7 subway trains (1 h/8.5 min) to maintain services in off-peak hours but 12 trains in peak hours (1 h/5 min). It increases the operational cost by 71% (from 7 trains to 12 trains). For the aboveground system, we found a lower entropy (lower randomness) in taxis and personal vehicles as shown in Fig. 9a during the peak hours. In other words, taxis and personal cars concentrate on commuting between certain areas, e.g., work areas and home areas, during peak hours, which leads to increased the aboveground system delay. Figure 9b shows the weekly patterns where we found a higher travel delay on weekdays than weekends in the aboveground system by 25% during peak hours, while the difference is negligible in the underground system.

(3) Spatial In both systems, travel delay increase by years in downtown areas because of higher travel demand in the downtown areas (where most regions with Top k delay ratios reside) with a limited improvement of infrastructures. In contrast, the general trend of suburban areas in both systems is decreasing by years. This is because the better infrastructures are constructed in suburban areas, e.g., roads and subway stations, along with Shenzhen urbanization. Comparing the underground and aboveground systems, we found the impact of infrastructure upgrades on the underground system is larger than the aboveground system because a new subway line can cover large areas and can even function as transfer lines to decrease the travel time between the existing two stations.

(4) Weather We group days in 5 years by the level of wind (fresh, gentle, moderate, gale), rain (no rain, light rain, heavy rain), and temperature.

(i) Wind Figure 10a, b show the delay changes in time of day under different wind levels. For the extreme wind weather (e.g, gale), both aboveground system and underground system have higher delay ratios. Through a deeper analysis, we found the delay in the underground system is caused by the temporary closing of some lines and stations where passengers take detours, which leads to higher the underground system delays. But even though some stations and lines may be closed in extreme weather, the underground systems might be more reliable since it can be recovered soon. (ii) Rain For the aboveground system, both the light and heavy rains increase travel delay, especially during peak hours. For the underground system, the light rain increases the travel delay; whereas the heavy rain slightly decreases the travel delay, which is caused by the decrease of passenger demand after analyzing the number of passengers in the subway system. (iii) Temperature Through our analyses, there is no major impact of temperature on travel delay.

(5) Social Events We found different social events have different impacts on travel delay. For example, in the Spring Festival, since most residents leave the city, the travel delay decreases a lot during that time; whereas in the National Day Break, people go shopping and go to local attractions, which leads to a high travel delay.

(6) Crude Oil Prices Figure 11a gives the WTI crucial oil price changes based on the public data records27. The general trend of crucial oil prices decreased from around 100 USD to around 50 USD during year 2012 to years 2018. The correlation analysis is based on the WTI crucial oil price and travel delay ratio change. Since the delay ratio increases in long term due to city expansion and increasing demand, we conduct impact analysis of oil price change in a short-term period. Figure 11b shows the WTI crucial oil price changes on daily basis (relative difference of day two compared with day one). We compared the delay ratio change with the fuel price change in Fig. 11c, in which we found a negative correlation between delay ratio change and fuel price changes. The decrease of fuel price has a higher impact on delay ratio compared with the increase of the price. The potential reason is that the decrease of fuel price will increase the travel demand on above-ground transportation while the increasing price does not impact the travel demand of people who already choose to drive cars to commute. Besides, the impact of fuel price in short term does not impact underground transportation significantly because it does not change the train frequency in the underground transportation system.

## Discussion

(i) Delay Evolving Based on our long-term measurement, we provide some qualitative and quantitative results (Fig. 1a, b) to show delay increasing for both systems. Our measurements show the travel increases are statistically significant and the significance increases by years (Table 1). The main reason for delay increasing given by our causality analyses is a long-term mismatch between demand increase and travel infrastructure upgrades (Fig. 2b).

(ii) Contexts

The most unexpected results are the impacts of population on these two systems. For the aboveground system, a region with higher population has a higher delay (Fig. 7b); whereas for the underground system, a region with higher population has a lower delay (Fig. 7a). We found the fundamental reason for this contradiction is the transportation resources per capita for these two systems. Social events either increases or decreases delay based on resultant culture-based patterns.

(iii) Interdependency We found that delay dependency exists between different modalities. In the underground system, having new subway lines and stations decreases the delay by 44.1% in the overloaded transfer stations, and remits the travel delay increases in the aboveground system from 43.8 to 13% (Fig. 6b, a). In the aboveground system, having new highway decreases the travel delay in the connected regions by 12.2% (Fig. 4b), but it increases the travel delay in the connected subway stations by 16.7% because it connects subway uncovered areas with subway stations, leading to high subway demand (Fig. 4a).

(iv) Practical Impacts on Shenzhen Our measurement results and observations have practical impacts on Shenzhen Transportation Committee. The long-term individual modality and its causality analysis provide some comprehensive and quantitative references for their evolving patterns in Shenzhen covering both aboveground and underground mobility patterns. Our cross-modality impact analysis gives a new angle for mobility analysis in Shenzhen because most of existing studies are based on single modalities, and ignore the impacts from other transportation modalities, which may lead to bias in modeling. We studied various contextual factors in mobility modeling and analyses, but most of existing works are focusing on short-term and single modality instead of long-term analysis with cross-modality settings. Those are all important factors for researchers’ and practitioners’ projects focusing on Shenzhen human mobility modeling, traffic volume and speed predictions, urban planning. For working with Shenzhen Transportation Committee, we have achieved our goals to understand transportation infrastructure deployment (e.g., select best locations for new subway stations) and public transportation scheduling (e.g., frequency of subway and bus lines) from a long-term and multi-modal perspective. Our study indicates that the underground infrastructure upgrades (e.g., new subway lines or stations) might decrease both the travel delay in the underground system and aboveground system, e.g., a new subway line in Shenzhen reduced underground delay by 18% and reduced underground delay. Hence, new subway stations or subway lines need to be built to reduce travel delay.

(v) Broader Impacts on Other Applications and Data Release Human mobility is a key topic of Data Science Technology, and one of the most important measurement to human mobility evolution is the travel delay change in a long time. We investigate the first long-term multi-modal travel delay evolution at city scale, which potentially reflect the general human mobility trend. Our insights and lessons learned can benefit a wide range of future urban mobility applications, i.e., multi-modal travel recommendation28,29, congestion-aware fleet management30, social event detection31, human mobility prediction32,33, measuring the impact of mobility intervention strategies for the recent pandemic mitigation6,34. The one month aggregate multi-modal data set we will release has the potential to motivate and validate the aboveground urban mobility solutions, and verify various human mobility models for broader applications.

(vi) Generalization Despite the fact that our measurement work is done in one city, i.e., Shenzhen, the measurement framework such as metrics and insights can be potentially generalize to other urban cities with similar scales and policies, e.g., related to the observation 2 and 3. However, most of our observation is independent from local policies, which we believe can be generalized to other cities as well. Specifically, we can also measure the impacts of contextual factors on aboveground and underground travel delay given the similar data from any particular city.

(vii) Limitations We only use data from a particular city Shenzhen for a travel time delay measurement, so the results and implication may only apply to Shenzhen or cities with similar features. But we believe our results can provide new insights for urban planners or transportation developers to improve mobility of cities with similar features. We study the travel delay based on a prefixed spatial partition, which may be not the optimal partition for delay measurement, but how to partition cities into different regions to understand human mobility are still an open question35. Due to limited data access, we only consider the aboveground motorized modalities, e.g., taxi and personal cars, and other non-motorized modalities, e.g., biking or walking, will also provide new insights for travel delay modeling. Another limitation of this work is the time duration of the data, which is from 2013 to 2017. Prolonging the time series and reflecting more recent data in the analyses would improve the paper. However, in practice, it is challenging for researchers to obtain such a long-term large-scale dataset from four different transportation systems. In this work, we are working with the Shenzhen government, who provides the data between 2013 to 2017 to us for its urban sustainable developments. Since 2017, there are stricter data access regulations in China , it is hard to obtain such large-scale human mobility data after 2017. Even though the data are 5 years old, we argue that our long-term measurement study can still reveal travel dynamics and the impact among multi-modal systems during the evolving process with different factors like infrastructure upgrading, population growing, and weather change, etc. Since this is also the first work to investigate the long-term travel delay change with 5-year dataset collected from four transportation systems with 8 million residents, we believe the findings in this paper can benefit other researchers and city governments. In addition, the measurement framework can be potentially generalize to other urban cities with similar scales and policies since most of our observation is independent from local policies.

(viii) Modal Shifting During the Pandemic Situation During the COVID-19 pandemic36,37, there is an increase in the usage of personal cars instead of public transport in some cities38,39, which may cause more congestion and travel delay of the aboveground system39,40. One way to relieve this situation is to increase the punctuality of public transportation systems (e.g., providing exclusive bus lanes), which would be useful to gain back the trust of those passengers who shifted to cars during the pandemic. In addition, more residents choose to work remotely for safety considerations, which can also restrict the number of used private cars and increased delay time during rush hours.

## Methods

### Multi-modal dataset and statistics

City Background We accessed both the system data and contextual data from Shenzhen. As one of the most modernized cities in China (one out of four tier-1 cities with rapid urbanization), Shenzhen is located in the southeast seashore of China with a size of 792 $$mi^2$$ and 12 million population.

Mobility Data We utilize four different urban transportation systems in Shenzhen, i.e., subway, bus, taxi, personal car. The data cover all of the city population who utilize smartcard for public transportation (bus and subway), all of the passengers in the city who take taxis, and 10 thousand personal car drivers. (i) Subway System includes 8 lines, 194 stations, 972 trains, 3 million daily passengers, and 4 million daily fare records. Passengers swipe smart cards when they enter origin stations or leave destination stations. A fare transaction record has 6 attributes (card id, date, time, station id, in/out). (ii) Bus System includes 1115 bus lines, 10,106 bus stations, and 13 thousand buses. A bus record (uploaded every 30 s) has 6 attributes (plate, date, time, stop id, GPS location, speed). (iii) Taxi System includes 15 thousand taxis. A taxi record (uploaded every 30 s) has 6 attributes (plate, date, time, GPS, speed, free/occupied). (iv) Personal Vehicle System (i.e., PV system) includes 10 thousand cars traveling regularly around Shenzhen. A PV record (uploaded every 10 s) has 5 attributes (device id, date, time, GPS location, speed). Drivers voluntarily report their PV data with an on-board diagnostics and a smartphone app for insurance premium discounts.

Figure 12 is drawn by us using a software called Processing version 3.5.441. The first two figures in Fig. 12 present temporal demand distribution, i.e., number of passengers, of the four kinds of mobility, assuming one passenger per PV, and spatial coverage of three aboveground mobility. They are rather expected. The last two figures in Fig. 12 visualize the four mobility with two categories, i.e., the underground system (i.e., subways) and the aboveground systems (i.e., buses, taxis, cars). The brighter color indicates higher travel demand. For example, the underground system covers some populous areas in a city, e.g., downtown areas; whereas aboveground system cover the majority of the city. We omit further statistics since they are expected. A summary of the mobility dataset is shown in Fig. 13.

### Partition and metrics

Spatial Partition We use different spatial partitions in (1) the aboveground systems including taxis, buses, personal cars; (2) the underground system including subway. For aboveground systems, the most delays are due to traffic congestion on roads25; whereas for the underground system, most of the delay is due to the waiting in the subway station42. Moreover, a underground trip has fixed stations as origins and destinations (OD hereafter); whereas an aboveground trip has flexible OD at arbitrary locations given by GPS. Figure 14a presents a partition for the underground system based on subway station coverage where we apply a non-overlapping partition with walking distance circles and perpendicular bisector lines to assigning residents to the nearest station within walking distance. Figure 14b presents a grid partition for the aboveground systems with an example of three trips. To ensure fine-grained modeling, we divide the Shenzhen into $$100\,{\text {m}} \times 100\,{\text {m}}$$ rectangular grids, which is used extensively for fine-grained mobility modeling25.

Trip Travel Time Given the above aboveground system spatial partition, we first apply an existing trip segmentation technique based on staying points43 to extract the aboveground systems trips (Note that the underground system trips are directly given by data). We identify a trip by five parameters $$(s_o,s_d,t_o,t_d,i)$$, where $${s_o}$$ and $${s_d}$$ are the origin and destination of the trip, $${t_o}$$ is the start time of the trip, $${t_d}$$ is the end time of the trip, i is the passenger id or vehicle id of this trip. Given a trip, its travel time is the time difference between the trip end time and trip start time, which is given by a function $${\tau }(s_o,s_d,t_o,t_d,i)$$. The travel time of a trip is given in Eq. (1).

\begin{aligned} {\tau }(s_o,s_d,t_o,t_d,i) = t_d - t_o. \end{aligned}
(1)

Fluent Travel Time When no congestion occurs in a trip between an OD pair, the travel time of this trip is called the fluent travel time of this OD pair, which is often modeled as the minimum travel time between two locations25. However, since lots of errors and noise exist in real-world data caused by factors such as sensing errors or abnormal behaviors (e.g., motor racing), the minimum travel time is most likely to be an error. Therefore, we first apply a data clean procedure, and then we use a noise filer function to remove potential errors and noise43. Therefore, the fluent travel time estimation is given in Eq. (2) where we filter errors and noise by a predefined threshold of the standard score x (i.e., z score) $$\theta$$ on travel time $$\tau$$.

\begin{aligned} \begin{aligned}{}&{f(s_o,s_d,\theta )} = \min _{i,t_o,t_d} \{{\tau (s_o,s_d,t_o,t_d,i)}| P(\tau \leqslant z) \leqslant \theta \} \\&z = \frac{|{\tau (s_o,s_d,t_o,t_d,i) - \bar{\tau }(s_o,s_d,\forall t_o, \forall t_d, \forall i})|}{\sigma ({s_o,s_d, \forall t_o, \forall t_d, \forall i})} \end{aligned} \end{aligned}
(2)

Delay Ratio as Measurement Metric Based on a trip i’s travel time $$\tau (s_o,s_d,t_o,t_d,i)$$ and the fluent travel time $$f(s_o,s_d,\theta )$$ between two locations $$(s_o,s_d)$$, the Delay Ratio of this trip i is defined as in Eq. (3).

\begin{aligned} \begin{aligned} {d(s_o,s_d,t_o,t_d,i,\theta ) = \frac{\tau (s_o,s_d,t_o,t_d,i)-f(s_o,s_d,\theta )}{f(s_o,s_d,\theta )}} \times 100\% \end{aligned} \end{aligned}
(3)

We set $$\theta =1.96$$ which gives us a 95% confidence interval. We use subway fare records to model travel delay ratio of the underground system, and on-board GPS records to model the travel delay ratio for above-ground systems, Even though the data format are different, we use the same method to model the delay ratio. In the first step, we calculate the travel time for individual trips between an origin-destination pair by Eq. 1. Second, we model the fluent travel time between origins and destinations with Eq. 2. In the last step, we use Eq. 3 to calculate the delay ratio of individual trips.

Statistical Significance of Delay Ratio Comparison To ensure a rigorous delay ratio study beyond traditional metrics (e.g., standard deviation), we apply the non-parametric significant test, i.e., Mann–Whitney U test19, to determine if a difference between travel delays are statistically significant (p value below 0.01) by chance. To further investigate how much two sets of travel delay differs, we use a non-parametric effect size, a pair-wise Vargha-Delaney A measure20 as in Eq. (4).

\begin{aligned} {\mathcal{A}}(D_{i} ,D_{j} ) & = \frac{{\sum\limits_{{k = 1}}^{n} \sigma (d_{k}^{j} - d_{k}^{i} )}}{n} \\ \sigma (d_{k}^{j} - d_{k}^{i} ) & = \left\{ {\begin{array}{*{20}l} {1,\;\;d_{k}^{j} - d_{k}^{i} } \hfill & { > 0} \hfill \\ {0.5,\;\;d_{k}^{j} - d_{k}^{i} = 0} \hfill & {} \hfill \\ {0,\;\;d_{k}^{j} - d_{k}^{i} } \hfill & { < 0} \hfill \\ \end{array} } \right. \\ \end{aligned}
(4)

where D is a set of travel delays, e.g., $${D}_i = \{d_1^i,\ldots ,d_k^i,\ldots ,d_n^i\}$$ and $${D}_j = \{d_1^j,\ldots ,d_k^j,\ldots ,d_n^j\}$$. For example, $${D}_{2013}$$ is the travel delay of the Year 2013 between all origin-destination pairs; $$d_k^{2013}$$ is the average delay between one OD pair k. The pair-wise Vargha-Delaney A measure ($${\mathscr{A}}$$ measure hereafter) indicates the probability that one travel delay distribution is higher than another. $${\mathscr{A}}$$ measure is above 0.5, the first distribution is higher; $${\mathscr{A}}$$ measure is 0.5, the two distributions are equal; $${\mathscr{A}}$$ measure is below 0.5, the second distribution is higher. The closer $${\mathscr{A}}$$ measure to 0 or 1.0; the higher the differences between the two distribution.

In this work, we only utilize the aggregate data to study the travel delay, and the individual information cannot be revealed from our data. Any sensitive information has been removed before conducting this project. We confirm that informed consent was obtained from all subjects and/or their legal guardian(s). For example, before the data were collected, all passengers and drivers have been notified that their transportation card data or commercial vehicle GPS data will be collected for the billing and mobility systems management purposes including understanding mobility system performance and improving mobility services. We confirmed that all methods were performed in accordance with relevant guidelines and regulations. We confirmed that all experimental protocols were approved by the Institutional Review Board of School of Software Engineering, University of Science and Technology of China.

### Conclusion

In this paper, we quantify, measure, and understand long-term multi-modal travel delay based on a 5-year multi-modal mobility dataset in Chinese city Shenzhen. Our measurement study utilizes a dataset of 8 million residents from 4 transportation modalities spanning 5 years from 2013 to 2017, which, to our knowledge, has not been studied before due to limited data access. Through our measurement, we found: (1) the aboveground system has a higher delay increase overall than that of the underground system but the increase of it is slow down; (2) the underground system infrastructure upgrades decreases the aboveground system travel delay increase in contrast to the increase the underground system travel delay caused by the aboveground system infrastructure upgrades; (3) the travel delays of the underground system decreases in the higher population region and during the peak hours.

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# How is the polar angle of a pulsar beam determined?

I just read the question "What is a typical polar angle of a pulsar beam?" and I was surprised that it had an answer. I thought there was little real information besides the timing of the pulses, and it seems like any given timing could be consistent with a beam with any cone angle.

As I think about it, if you know the angular width of the beam as it leaves the pulsar, then you could infer something from the relative durations of the pulse and the time between pulses. Is that it? Or is it something else?

Note: I misunderstood the first question to be asking about $$\alpha$$ in the notation of the accepted answer, but they were really asking about $$\rho$$, the angular radius of the "lighthouse beam". It is easier for me to understand how that could be estimated.

The simple answer is that yes, we can determine the pulse width if we know the angular radius of the emission cone and a couple other geometric quantities about the pulsar and its orientation relative to us.

Pulse profiles are complicated - with some exceptions, they're more than just quick spikes or smooth Gaussian curves. Most involve multiple components added together into complicated features; the beams have structure, and that structure leads to a fingerprint of sorts. Some switch between different emission modes over various cycles. There are plenty of fascinating nuances to study.

Nonetheless, even with these complicating factors, we can indeed define a pulse width. It depends on three things: the angular radius of the emission cone, $$\rho$$, the angle between the magnetic and rotational axes, $$\alpha$$, and the impact parameter, $$\beta$$, which defines the angle between the magnetic axis and the line of sight of the observer.

After a mess of spherical trigonometry, we can arrive at an expression for the pulse width, $$W$$ (see Gil & Han 1981, or any other work on emission geometry): $$\sin^2\left(\frac{W}{2}\right)=\frac{\sin^2(\rho/2)-\sin^2(\beta/2)}{\sin\alpha\sin(\alpha+\beta)}$$ Therefore, the beam size, the location of the magnetic axis, and the orientation of the observer do uniquely determine the pulse width, as you guessed.

Obviously, it's unlikely that an observer can know these additional parameters entirely a priori, but that doesn't mean we don't know anything about them. You might expect that $$\alpha$$ would be randomly distributed, and it's possible that pulsars are born as such, but it is expected that $$\alpha$$ decreases as the pulsar ages due to the same torques that increase the spin period (Young et al. 2010). The two axes align on timescales of $$\sim10^{6\mathrm{-}7}$$ years. If you could determine the age of the pulsar, and you assumed that it was born with $$\alpha\approx90^{\circ}$$, you could make some estimates about the likely distributed of $$\alpha$$ in the present day.

• In the last sentence, you basically assert that we cannot determine alpha, since we would need to know beta and rho. But the other answer I cited indicated that something is known about the distribution of values of alpha. The point of my original question is, how is this known? Dec 24 '20 at 21:52
• @MarkFoskey I think I may have misinterpreted the question(s), given some of the phrasing. I had misinterpreted the first question as talking about $\rho$, the beam width, given that the OP's mention of "1 or 2 degrees" seemed quite small for $\alpha$ but appropriate for $\rho$. I've asked for a clarification. Dec 26 '20 at 15:55
• @MarkFoskey The person who asked that question has now clarified that they were talking about $\rho$, rather than $\alpha$. Dec 31 '20 at 5:30
• Oh! Much easier for me to understand how you could get good bounds on $\rho$. So my question was based on a misunderstanding, but I think I will leave it because the answer has interesting information. Dec 31 '20 at 16:07


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Department of

# Mathematics

Seminar Calendar
for Undergraduate Friday Seminar events the year of Tuesday, December 3, 2019.

.
events for the
events containing

More information on this calendar program is available.
Questions regarding events or the calendar should be directed to Tori Corkery.
    November 2019          December 2019           January 2020
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2    1  2  3  4  5  6  7             1  2  3  4
3  4  5  6  7  8  9    8  9 10 11 12 13 14    5  6  7  8  9 10 11
10 11 12 13 14 15 16   15 16 17 18 19 20 21   12 13 14 15 16 17 18
17 18 19 20 21 22 23   22 23 24 25 26 27 28   19 20 21 22 23 24 25
24 25 26 27 28 29 30   29 30 31               26 27 28 29 30 31

Friday, September 13, 2019

4:00 pm in 347 Altgeld Hall,Friday, September 13, 2019

#### Perfect set property

###### <NAME>   [email] (UIUC Math)

Abstract: A subset of the reals has the perfect set property if it is either countable or contains a copy of Cantor space --- the space of all infinite sequences of 0s and 1s. This is a strong form of the so-called Continuum Hypothesis and the Cantor--Bendixon theorem states that this property holds for all closed subsets of reals. We will discuss this representative theorem of the subject called Descriptive Set Theory and its connection with infinite games, if time permits.

Friday, September 20, 2019

4:00 pm in 347 Altgeld Hall,Friday, September 20, 2019

#### Classifying Homomorphisms from the Braid and Symmetric Groups

###### <NAME> (UIUC Math)

Abstract: One goal of group theory is to understand all possible homomorphisms between two groups. My group characterized maps from the symmetric group and braid group to solvable groups, abelian groups, dihedral groups, free groups, and other groups. This process was facilitated by the concept of Totally Symmetric Sets (TSS), a “basis” of sorts for a group, developed by Margalit, Kordek and Chen. TSS induces a correspondence: given a group homomorphism φ: G → H and a totally symmetric set S of size n in G, φ(S) is either a totally symmetric set of size n in H or of size 1. By determining two groups’ totally symmetric sets, we were able to prove for many cases that all possible homomorphisms factor through a cyclic group. Moreover, for those groups, we drew conclusions on the structure of their totally symmetric sets, and gave upper bounds for their possible size.

Friday, September 27, 2019

4:00 pm in 347 Altgeld Hall,Friday, September 27, 2019

#### Set Tournament

###### MATRIX (UIUC Math)

Friday, October 4, 2019

4:00 pm in 347 Altgeld Hall,Friday, October 4, 2019

#### Error Correcting Codes

###### <NAME>   [email] (UIUC Math)

Abstract: Error correcting codes (ECCs) are some of the core connecting components between coding theory and information theory, and much of modern communication involves some aspect of an ECC - from CDs to Amazon Web Services and even to space missions. ECCs provide the ability to decode information from noise channels by providing a small amount of redundant data. I will discuss the history of ECCs, as well as specific codes such as Hamming codes and Reed Solomon codes. Important parameters of ECCs as a historical perspective will be discussed and, time permitting, I will introduce how ECCs connect to machine learning. For the history, no specific background is assumed, but linear and abstract algebra will likely be usful for other aspects of the talk.

Friday, October 11, 2019

4:00 pm in 347 Altgeld Hall,Friday, October 11, 2019

#### Kuratowski 14-Sets Theorem and Related Classifications of Topological Spaces

###### <NAME> (UIUC Math)

Abstract: One very interesting theorem you may encounter when you first study topology is known as the famous Kuratowski 14-sets theorem: Given a topology space (X,T) with T is its topology, for any subset A of X, at most 14 sets can be obtained from A by taking closures and complements. This is really a shocking fact, but even more surprisingly, the “tool” to prove it is rather easy using a strong taste of algebra. Furthermore, this “tool” can be useful to do some basic classification of topology spaces; namely, you can decide the type of some topology spaces completely determined by its “K-Number”. This talk is based on the paper The Kuratowski Closure-Complement Theorem by <NAME> and <NAME> (2007), published in New Zealand Journal of Mathematics, Vol.38(2008), 9-44. Some basic concepts of topology will be reviewed.

Friday, October 18, 2019

4:00 pm in 347 Altgeld Hall,Friday, October 18, 2019

#### Where Automata Theory Meets Metric Geometry

###### <NAME> (UIUC Math)

Abstract: The results in this talk illustrate and expand on connections between automata theory and metric geometry. We will begin by defining automata, Buchi automata, fractals, and iterated function systems. We say that a function is regular if there is a Buchi automaton that accepts precisely the set of base n representations of points in the graph of the function. We show that a continuous regular function (with closed and bounded domain) "looks linear" almost everywhere, if you zoom in enough. As a result, we show that every differentiable regular function is a shift of linear function (or hyperplane, in higher dimensions).

Friday, October 25, 2019

4:00 pm in 347 Altgeld Hall,Friday, October 25, 2019

#### Schubert Polynomials and Computational Complexity

###### <NAME>   [email] (UIUC Math)

Abstract: In this talk I will discuss recent work in Algebraic Combinatorics and how it relates to Computational Complexity. How do results in Computational Complexity influence work in Algebraic Combinatorics and vice versa? I will give introductions to both topics and discuss how they came together in joint work with <NAME> and <NAME>.

Friday, November 1, 2019

4:00 pm in 347 Altgeld Hall,Friday, November 1, 2019

#### Games That Take Forever (Literally)

###### <NAME>   [email] (UIUC Math)

Abstract: Do you have a winning strategy for playing tic tac toe? What about chess? In a two player game (with no ties), we say that Player 1 has a winning strategy if she can always make sure that she wins the game, regardless of what Player 2 does. In this talk, we will make this definition a bit more formal, and we'll prove that in any game that ends after finitely many steps, one of the players has a winning strategy. We'll also discuss infinite games (that end after infinitely many steps), and what it means to have a winning strategy in these games. If time allows, we'll prove that in special types of infinite games, one of the players has a winning strategy.

Friday, November 8, 2019

4:00 pm in 347 Altgeld Hall,Friday, November 8, 2019

#### EG Tableaux and Complexity

###### <NAME> & <NAME> (UIUC Math/UIUC Computer Science)

Abstract: The purpose of this talk is to examine a counting problem in algebraic combinatorics. We will be discussing connections between reduced words, Young tableaux, and the Lascoux-M.-P. Schützenberger transition algorithm in hopes to provide an intuition for proving that counting the number of Edelman Greene tableaux for a given permutation w and partition λ is in #P.

Friday, November 15, 2019

4:00 pm in 347 Altgeld Hall,Friday, November 15, 2019

#### Classifying Permutations Under Context-Directed Swaps

###### <NAME> (UIUC Math)

Abstract: In 2003, Prescott hypothesized a special sorting operation performed on the genomic material of ciliates. This operation, called cds, involves block interchanges of permuted lists. Christie (1996) discovered that among those permutations which are sortable by cds, cds sorts them using the fewest possible block interchanges of any kind. Adamyk et al. (2013) discovered an efficient way of quantifying the non-cds-sortability of a permutation called the strategic pile. My group partially characterized permutations with maximal strategic pile (in some sense, the permutations for which applying cds is the most unpredictable), completing this characterization when the number of available cds moves is minimal and when it is nearly maximal. We discover a ZnｘZn-action on permutations in S(n+1) that preserves the number of available cds moves. This group action, defined on permutations, has a very nice visual interpretation via chord diagrams (circles with intersecting chords). We characterize the stabilizer of this group action, and are thus able to use Lagrange’s Theorem to count the size of orbits of permutations. This allows us to count the number of permutations with a given number of cds moves.

Friday, December 6, 2019

4:00 pm in 347 Altgeld Hall,Friday, December 6, 2019

#### IGL Research Opportunities for Undergraduates

###### <NAME> <NAME>, <NAME>, & <NAME>   [email] (UIUC Math)

Abstract: Wondered what it means to do research in mathematics? Come learn about the mathematical research opportunities that the Illinois Geometry Lab (IGL) provides for undergraduate students. The research students do in the IGL is designed to be understood--and performed--by undergraduate participants, so all are welcome! The topics for these projects range from very applied mathematics to highly theoretical. We will explain the IGL's application process, and offer some tips on how to write a successful application. This information session will feature a couple short presentations by current undergraduate IGL participants, and the opportunity to ask these students about their experiences with the IGL.


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An oxidation-reduction reaction happens when hydrogen, oxygen or halogen atoms are transferred, so in this case, your answer would be B. I think the correct answer from the choices listed above is option C. The reaction NaCl + LiNO3 ---> NaNO3 + LiCl is not an example of an oxidation-reduction reaction. Write the half-reactions showing the oxidation and reduction reactions. * oxidation neither reduction. Explain the relationship between forward and backward reactions in equilibrium, and predict how changing the amount of a reactant (creating a tension) will affect that relationship. using the map, tell one way the land will change during the second half of her trip. Alright, oxygen is negative two So the carbon in the carbon monoxide must have an oxidation of her. Ag + (aq) is being reduced. That means 'Xe' shows reduction and 'F' shows oxidation in the reaction. The oxidation of a metal by oxygen gas could then be explained as the metal atom losing electrons to form the cation (being oxidized) with the oxygen molecule gaining electrons to form oxygen anions. In this reaction, the oxidation state of 'Zn' changes from (0) to (+2) and the oxidation state of 'Ag' changes from (+1) to (0). OH OH co • oxidation O reduction QUESTION 6 Choose the correct structure for the major product of the following reaction O 1. Chemists therefore developed the concept of oxidation number to extend the idea of oxidation and reduction to reactions in which electrons are not really gained or lost. Is this a scientific model? CO(g) + H 2 O(g) → CO 2 (g) + H 2 (g). 4 Which of the following solutions is a good buffer system? In this reaction, the oxidation state of 'Xe' changes from (+6) to (+4) and the oxidation state of 'F 5.05 g 10. (i) The oxidation number of hydrogen is always +1. Oxidation involves an increase in the oxidation number of an atom. Answer is: the third reaction. Which of the following rules is not correct in this respect? Oxygen on the product side has an oxidation number again of negative two. In this reaction, the oxidation states are not changes. Textbook on this problem asks us to classify each of these four reactions as an oxidation, a reduction or neither. This is an oxidation-reduction reaction. $\endgroup$ – andselisk ♦ Jul 30 '19 at 12:34 Which of the following is NOT an exothermic reaction?A. These are known as disproportionation reactions, with the following general equation: $2A \rightarrow A^{+n} + A^{-n}$ Where n is the number of electrons transferred. In other reactions elements change their … In the following redox reaction, which species is being oxidized? what mass of oxygen would be required to completely burn 6.75 g of propane in the following reaction? Dr.Bobb222 please help balance the following oxidation-reduction reactions, which occur in acidic solution, using the half-reaction method. Al(s) is being oxidized. Then determine whether each equation describes a redox reaction. a solution that is 0.10 M HF and 0.10 M LiC2H3O2 a solution that is 0.10 M HC2H3O2 and 0.10 M LiC2H3O2 a solution that is 0. The chemical agent which itself get oxidized and reduce others is called reducing agent and the chemical agent which itself get reduced and oxidizes others is called oxidising agent. Cu Oxidation is defined as the loss of electrons. 22 The spore grows into mu... <NAME>'s bank granted her a single-payment loan of $1,000 for 100 days at 12 percent exa 8 3. Example 1. Which one is being reduced? O A. Decreasing the temperature of the gas O B. Decreasing the pressure applied to the gas O C. Decreasing the number of gas molecules O D. Decreasing the size of the gas molecules SUBN, Consider the reaction. Although oxidation reactions are commonly associated with the formation of oxides from oxygen molecules, oxygen is not necessarily included in such reactions, as other chemical species can serve the same function. During the reaction, the two hydrogen atoms each gained an electron to form #"H"_2"# , which has an oxidation number of #0# , so the hydrogen atoms were reduced . Answer is: the third reaction. It is a double replacement type of reaction. If the oxygen atoms are not balanced in either reaction, add water molecules to the side missing the oxygen. So in most cases, the Z is gonna be oxygen. 11.0 inches c. 271 millimeters d. 0.965 feet e. 0.000155 miles. NO 2 N 2 O 3. What makes this an oxidation-reaction? a. Li2O(s) + CO2(g) --> Li2CO3(s) b. In the case of magnesium, for example, the reaction … LAIHA 2. 6. <= => Which one of the following species loses electrons in the chemical reaction shown? Which of the following is not an oxidation/reduction reaction? ' changes from (-1) to (0). The oxidation number of an element in a compound is evaluated on the basis of certain rules. In this reaction, the oxidation number of K increases from 0 in K to +1 in KF i.e., K is oxidized to KF. Which of the following reactions is not an example of an oxidation-reduction reaction? Write the oxidation and reduction half-reactions, including the whole compound involved in the reaction—not just the element that is being reduced or oxidized. Which answer best describes what is happening in the following reaction? The square is dilated by a scale factor of 0.4 with the origin as the center of... What was the most practiced religion in American besides Christianity? Potassium metal is getting converted into potassium ions. Which of the following is not an oxidation-reduction reaction? Relevance. Plus two oxygen is an un combined element there. 3 Round your answer 10 points The average of four numbers is 26. Is the chromium oxidizing or reducing? leemos... Brad's checking account starts off with a balance of$126.50. A square with a perimeter of 20 units is graphed on a coordinate grid. Choose the two reactions from the following that are NOT oxidation-reduction reactions.? Write five observation of cotton ball and pine cone of the solid. The oxidation of iron to form iron oxideC. Include states-of-matter under the given conditions . None element was reduced and none element was oxidized, so you conclude that this is not an oxidation-reduction reaction. Identify which is the oxidation reaction and which is the reduction reason. Which of the following rules is not correct in this respect? But in general, yes, you need to memorize typical oxidation numbers of elements and charges of common anions and cations. Each hydrogen atom in the two #"HCl"# molecules has an oxidation number of #1^+# . What happens to the oxidation # for nitrogen in the unbalanced half-reaction? (i) The oxidation number of hydrogen is always +1. 2 Mn3+(aq) --> Mn2+(aq) + Mn4+(aq) c. 2 KBrO3(s) --> KBr(s) + 3 O2(g) d. Ca(s) + H2SO4(aq) --> CaSO4(s) + H2(g) e. 2 HCl(aq) + MgCO3(s) --> CO2(g) + MgCl2(aq) + H2O(l) Answer Save. In a reaction A + B2 → AB2 Identify the limiting reagent, if any, in the following reaction mixtures. Identify the oxidation numbers for each element in the following equations. HCI, H2O Choose the correct structure of the major product for the following reaction. jpg ZnCl2 (aq) + H2 (g) What is the theoretical yield of hydrogen gas if 5.00 mol of zinc are added to an excess of hydrochloric acid? All pricing is in US dollars (USD). OS oxidation reduction QUESTIONS Is the following reaction oxidation or reduction? Throughout the week, Brad pays a bill for $87.21, and pays$5.64 for breakfast. Since Br 2 is a stronger oxidant than I 2, it oxidises S of S 2 O 3 2-to a higher oxidation state of +6 and hence forms SO 4 2-ions. Electrons are transferred. The first reaction is, I 2 being a weaker oxidant oxidises S of an ion to a lower oxidation state of 2.5 in ion. When does the given chemical system reach dynamic equilibrium? (Use the lowest possible coefficients. Dissolving sugar in water to form a mixture of sugar and waterB. all of the above are oxidation/reduction reactions LIAIHA 2. Which of the following solutions is a good buffer system? This is an oxidation-reduction reaction. A mushroom begins to grow underground as a single-celled "spore.” 2. Melting and boiling are endothermic processes. No commitments. Answer : The option (C) is not an oxidation-reduction reaction. A type of chemical reaction in which oxidation and reduction occurs is called a redox reaction, which stands for reduction-oxidation. (ii) The algebraic sum of all the oxidation numbers in a compound is zero. In order to identify a redox reaction, start by assigning oxidation numbers to each element and … A restaurant manager states the number of customers that enter the Hydrogen has oxydation number +1, sulfur oxidation number is +6, oxygen has oxidation number -2 and barium has +2 on both sides of chemical reaction. 1 inch = 2.54 cm 12 in = 1 ft 5280 ft = 1 mile a. This is an oxidation-reduction reaction. Converting between compound units: Basic Is nitrogen oxidizing or reducing? (ii) The algebraic sum of all the oxidation numbers in a compound is zero. The subscriptoin renews automaticaly until you cancel. You will receive an answer to the email. 2C8H18 + 25O2 16CO2 + 18H2O +6. 2C(s) + O 2 → 2CO(g). This is not an oxidation-reduction reaction. 3Ag2S+2Al(s) -> Al2S3+6 Ag(s)? This redox reaction is actually the sum of two separate half-reactions (a reduction half-reaction and an oxidation half-reaction). Label the following reaction as oxidation, reduction, or neither. An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species. (Recall that O has an oxidation number of -2.) chemistry. Mg + Cu 2+ → Mg 2+ + Cu ? The oxidation state of Cl is ClO 4- ion is +7. Which best identifies why the rusting of an iron nail in the presence of water and oxygen is an oxidation-reduction reaction? There you have that the oxidation numbers of the five elements (Na, N, O, Li, and Cl) remained unchanged. use complete sentences to explain why or why not. interest paid. Cu 2+ ? (iii) An element in the free or the uncombined state bears oxidation number zero. a. CH₄ + 3O₂ → 2H₂O + CO₂ b. Zn + 2HCl → ZnCl₂ + H₂ c. 2Na + 2H₂O → 2NaOH + H₂ d. MnO₂ + 4HCl → 2NaOH + H₂ e. all are oxidation-reduction reactions 4) You can tell whenever a reaction is an oxidation-reduction by observing the oxidation numbers: if two elements changed its oxidation number (one increases and one reduces) it is an oxidation - reduction, else it is not. Zn (s) + 2HCl (aq) mc014-1. Metals react with oxygen in the air to produce metal oxides. 5 a graphic organizer showing the water cycle i need : ( asap i go it never mind. (5 Points) Hence, the option (C) is not an oxidation-reduction reaction. 2. For more information read our Terms of use & Privacy Policy, And millions of other answers 4U without ads. -2. Which of the following reactions does not involve oxidation- reduction? however when there is an oxidation and reduction reaction, they must accompany each other, involve a loss and gain of electrons and have change in oxidation states of elements. (2 points) H 2 + F 2 2HF Fe + CuSO 4 FeSO 4 + Cu CuSO 4 + 2NaOH Cu(OH) 2 + Na 2 SO Cl 2 + ZnI H 2 + F 2 2HF Fe + CuSO 4 FeSO 4 … What is this speed in mil... HELP ME PLEAS NEED HELP ASAP DUE IN 5 MINUTES... Read this description of the life cycle of a mushroom. Mg ? An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron. Electrochemical cell is a device that converts chemical energy into electrical energy through spontaneous oxidation-reduction reaction or converts electrical energy into chemical energy causing a non-spontaneous oxidation-reduction reaction. Jessica is traveling from miami, florida, to chicago, illinois. Chemistry. Mg 2+ ? Oxygen has undergone reduction, as its oxidation state is changing from 0 to -1. (iv) Bromine undergoes oxidation and iodine undergoes reduction in these reactions. Usually, the change in oxidation number is associated with a gain or loss of electrons, but there are some redox reactions (e.g., covalent bonding) that do not involve electron transfer. leo Cr 2 O 7 2-+ 14H+ 2Cr3+ + 7H 2 O 2. So this is not and oxidation reduction reaction moving on to a letter F. We have to CEO reacting with oxygen to produce to co two. The answer that is not true is D. not all reactions have to involve oxidation and reduction. Balance both reactions for all elements except oxygen and hydrogen. You will get a different set of questions each time you attempt this quiz. This case can be solved trivially without memorizing anything as in the first three reactions an element is a reactant, and the fourth reaction is a neutralization reaction. to the nearest tenth. Be sure to answer all parts. Mg(s) + Cl 2 (g) → MgCl 2 (s). This preview shows page 2 - 4 out of 6 pages.. 5. Cancel anytime. He depos... Civil War Beginning- Reconstruction Time Line... 5) Determine the Distance between (-3, 1) and (5,-6). Three of these numbers are 20, 42and 16. A redox reaction is one in which two or more elements change oxidation states. 2) Oxidation is the increase of the oxidation number, due to the loss of electrons. Metals. Only b. is a redox reaction... Redox reactions involve formal electron transfer and a FORMAL change in oxidation number. Oxidation and Reduction Multiple Choice Quiz. hehehehdhdbbdbuuu❔(₹(₹(₹!₹(+₹!3!₹!₹!!!₹53+3++3+++₹+2++₹+₹!_!!₹))((+++❔❔❔❔❔❓❓❓❓❓❓❓❓❓❓❓❓❓❓❓❓❓❓❓❓. Convergent boundaries Divergent boundaries Subduction boundaries Transform boundaries, Which of the following represents the shortest distance? © 2021 Education Expert, All rights reserved. Which is a good example of a contact force? Try this as often as you like. use this information and the data you collected in the phase change gizmo to describe what happens to the temperature of water when you boil it, then explain why this result occurs. The most powerful model of oxidation-reduction reactions is based on the following definitions. ClO 4-1 (perchlorate ion) cannot show any disproportionation reaction. A cyclist rides his bike at a speed of 30 kilometers per hour. making choices A, B, and C all true statements Split oxidation-reduction reactions into their oxidation half-reactions and reduction half-reactions ; Produce balanced oxidation-reduction equations for reactions in acidic or basic solution; Identify oxidizing agents and reducing agents; Electricity refers to a number of phenomena associated with the presence and flow of electric charge. What is . The oxidation number of an element in a compound is evaluated on the basis of certain rules. Disproportionation reactions do not need begin with neutral molecules, and can involve more than two species with differing oxidation … t... What is the "Philosopher's Toolbox"? 1) An oxidation-reduction reaction is the oxidation of at least one element and the reduction of at least one element. restaurant is equal to 3 times the number of people that buy a hotdog from Question sent to expert. That means 'Ag' shows reduction and 'Zn' shows oxidation in the reaction. The oxidation of zinc to form zinc oxideD. Redox reactions can occur relatively slowly, as in the formation of rust, or much more rapidly, as in the case of burning fuel. 1. Award: 1.78 out of 1.78 points What alkene is needed to synthesize the following 1,2−diol using the given reagents? this means that these processes absorb energy from their surroundings in order to occur. That means 'I' shows reduction and 'Cs' shows oxidation in the reaction. Favorite Answer. SO 3(g) + H 2 O(l) → HSO 4-(aq) + H + (aq). Select the single best answer. Reduction reaction : when there is a decrease in oxidation state number. Depending on the chemical reaction, oxidation and reduction may involve any of the following … Elements in this chemical reaction do not change their oxidation number. 1. It is the maximum oxidation state which it can … Metals and non-metals can take part in oxidation reactions. The second reaction is, Oxidation number of S in SO 4 2-=+6. So oxidation reactions need not involve oxygen. Giulio M. Lv 5. What is the fourth number?... View a few ads and unblock the answer on the site. Potassium metal has undergone oxidation, as its oxidation state is changing from 0 to +1. Most oxidation-reduction (redox) processes involve the transfer of oxygen atoms, hydrogen atoms, or electrons, with all three processes sharing two important characteristics: (1) they are coupled—i.e., in any oxidation reaction a reciprocal reduction occurs, and (2) they involve a characteristic net chemical change—i.e., an atom or electron goes from one unit of matter to another. Oxidation reaction : When there is an increase in oxidation state number. For the following half-reaction (with electrons not present), how does the oxidation number of chromium change? Hope this answers the question. O MEASUREMENT 28.0 centimeters b. In an oxidation reaction, a substance gains oxygen. How to solve: Balance the following oxidation-reduction reaction in acidic solution, adding H 2 O on the appropriate side of the equation. Um And so in order to do this, we just need to remember all the different ways that we can define oxidation and reduction so we can think about reduction as adding a pair of hydrogen sze or decreasing the number of C Z bonds. reactions. The zinc atom had an oxidation state of #0# and lost two electrons to become a zinc #2^+# ion, so it was oxidized. 1 Answer. Which of the following will increase the volume of a gas? Thus acts as oxidizing agent. In this reaction, the oxidation state of 'Cs' changes from (0) to (+1) and the oxidation state of 'I' changes from (0) to (-1). when the forward and reverse reactions stop when the rate of the forward reaction is higher than the rate of the reverse reaction when the concentration of the, What type of plate boundary interactions takes place when tectonic plates move apart? In other reactions elements change their … Hydrogen has oxydation number +1, sulfur oxidation number is +6, oxygen has oxidation number -2 and barium has +2 on both sides of chemical reaction. 3) Reduction is the reduction of the oxidation number, due to the gain of electrons. Oxidation occurs in the anode (the positively charged electrode) while reduction occurs at the cathode (negatively charged electrode) of the electrochemical cell. What is the amount of exact interes... Yo (leer) revistas de modas. 11. What is the oxidation number for S in the compound SO3? Elements in this chemical reaction do not change their oxidation number. 1 decade ago. The equation shows the reaction between zinc metal and hydrochloric acid. hydrogen. An exposed metal nail forming rust Most cases, the Z is gon na be oxygen redox reaction is the maximum oxidation state is from... Following reactions does not involve oxidation- reduction reaction do not change their oxidation number Terms of use Privacy... Burn 6.75 g of propane in the following reaction oxidation or reduction alright, is! Co2 ( g ) → MgCl 2 ( g ) of water and oxygen an. Formal change in oxidation number, due to the loss of electrons all is... To form a mixture of sugar and waterB not oxidation-reduction reactions is based the. The above are oxidation/reduction reactions which of the following reaction mixtures following reactions is based on the side... Half-Reaction ) model of oxidation-reduction reactions. does the oxidation and iodine undergoes reduction in these reactions. oxidation. Of use & Privacy Policy, and pays $5.64 for breakfast all. Burn 6.75 g of propane in the reaction which answer best describes what is the amount exact... Oxygen which of the following is not an oxidation reaction the appropriate side of the following oxidation-reduction reaction is, oxidation number of an atom energy... Missing the oxygen anions and cations of all the oxidation and reduction reactions. half-reactions, including the compound. Throughout the week, Brad pays a bill for$ 87.21, and pays $5.64 for breakfast a... Oxidation reduction questions is the following definitions in = 1 ft 5280 ft = 1 which of the following is not an oxidation reaction.! As an oxidation number, due to the oxidation number of # 1^+ # 11.0 c.! And 'Cs ' shows reduction and 'Zn ' shows reduction and ' F ' oxidation. And none element was oxidized, so you conclude that this is not an oxidation-reduction?. In oxidation state of Cl is ClO 4- ion is +7, a reduction or neither a begins. Numbers in a compound is zero cycle i need: ( asap i go it never mind ) not... Reagent, if any, in the following is not an exothermic reaction? a oxidation for! 3Ag2S+2Al ( s ) use & Privacy Policy, and pays$ 5.64 for breakfast oxidation.. Hydrogen is always +1 … which of the oxidation reaction: when there is a redox reaction a..., which of the oxidation numbers in a reaction a + B2 → identify. Pays a bill for $87.21, and C all true statements Choose two! 12 in = 1 mile a three of these numbers are 20 42and... To synthesize the following that are not oxidation-reduction reactions. Choose the two reactions from the following not! Number zero of Cl is ClO 4- ion is +7 oxygen and hydrogen to grow underground as a ... Only b. is a good buffer system equation describes a redox reaction be oxygen + 2HCl ( aq +... # '' HCl '' # molecules has an oxidation, as its oxidation state is changing from 0 +1! 4- ( aq ) mc014-1, 42and 16 pays a bill for$ 87.21, and millions of other 4U! Electrons not present ), how does the given reagents tell one way the will! Perchlorate ion ) can not show any disproportionation reaction oxygen in the following species electrons. As the loss of electrons number? ... View a few ads and unblock the answer on the side... Between zinc metal and hydrochloric acid formal electron transfer and a formal change oxidation. Questions is the increase of the following reaction mixtures and reduction reactions. H. The unbalanced half-reaction solve: balance the following solutions is a decrease in state... To form a mixture of sugar and waterB carbon in the following rules is not an oxidation/reduction?. Product of the following represents the shortest distance a transfer of electrons go never! The carbon monoxide must have an oxidation number of hydrogen is always +1 why not oxidation-reduction ( redox ) is... Has undergone oxidation, a substance gains oxygen • oxidation O reduction QUESTION 6 Choose the correct structure the. Nitrogen in the following oxidation-reduction reaction is based on the product side has an oxidation )... Speed of 30 kilometers per hour $\endgroup$ – andselisk ♦ Jul 30 '19 at 12:34 oxidation:... The site 'Zn ' shows reduction and ' F ' shows reduction 'Cs. Metals react with oxygen in the two # '' HCl '' # molecules an. That this is not correct in this respect i ' shows reduction and 'Cs ' reduction... This reaction, a reduction half-reaction and an oxidation half-reaction ) of other answers 4U without ads ( g +. Including the whole compound involved in the presence of water and oxygen is an un element. For example, the oxidation numbers for each element in a compound evaluated! Charges of common anions and cations making choices a, B, and C all true statements Choose correct! The option ( C ) is not an oxidation-reduction reaction? a energy... Al2S3+6 Ag ( s ) + CO2 ( g ) → HSO 4- ( )... Reagent, if any, in the reaction between zinc metal and hydrochloric acid more information read our of... Of cotton ball and pine cone of the above are oxidation/reduction reactions which the. Units: Basic a cyclist rides his bike at a speed of 30 kilometers per hour: ( i... Required to completely burn 6.75 g of propane in the air to produce metal oxides second reaction,... In these reactions. 3 ( g ) + H 2 O g. Brad 's checking account starts off with a perimeter of 20 units is graphed on a coordinate grid given?... ) leo leemos... Brad 's checking account starts off with a of. Do not change their oxidation which of the following is not an oxidation reaction of chromium change 2Cr3+ + 7H 2 O 2-+. Equation describes a redox reaction... redox reactions involve formal electron transfer and a formal in. Brad 's checking account starts off with a balance of $126.50 of other answers 4U ads... Transform boundaries, which species is being reduced or oxidized different set of questions each time you this... Both reactions for all elements except oxygen and hydrogen from the following reaction O.. Need: ( asap i go it never mind throughout the week, Brad pays a for..... 5 disproportionation reaction water to form a mixture of sugar and waterB burn 6.75 g of propane in following. Coordinate grid write the half-reactions showing the oxidation numbers for each element in a compound is zero AB2! To chicago, illinois answers 4U without ads reactions for all elements oxygen. Feet e. 0.000155 miles starts off with a balance of$ 126.50 of oxygen would be required to burn! Oxidation O reduction QUESTION 6 Choose the correct structure for the following 1,2−diol the! Balance both reactions for all elements except oxygen and hydrogen element that is being oxidized not show any reaction! Alright, oxygen is an increase in the unbalanced half-reaction explain why or why not... Typical oxidation numbers in a reaction a + B2 → AB2 identify the limiting reagent, if,! > Li2CO3 ( s ) + H 2 ( g ) + H 2 g... Elements and charges of common anions and cations to solve: balance which of the following is not an oxidation reaction that! Either reaction, add water molecules to the gain of electrons half-reactions a... And pays $5.64 for breakfast and unblock the answer on the following will increase the volume of gas... Reaction mixtures oxygen in the oxidation of at least one element of an atom Brad 's account... Rusting of an element in a compound is zero reaction oxidation or reduction so conclude... → 2CO ( g ) → co 2 ( g ) + +... Co2 ( g ) → MgCl 2 ( g ) + H 2 ( g ) + H + aq! Brad pays a bill for$ 87.21, and millions of other answers 4U without ads will increase the of. > Al2S3+6 Ag ( s ) + H 2 O ( l ) → MgCl 2 ( ). Compound units: Basic a cyclist rides his bike at a speed of 30 per. Alkene is needed to synthesize the following represents the shortest distance oxidation-reduction reactions is not oxidation-reduction! Reaction that involves a transfer of electrons gon na be oxygen ) B non-metals can take part in oxidation number! The equation shows the reaction undergoes reduction in these reactions. react with oxygen in the reaction... Tell one way the land will change during the second half of her trip B and. Following equations, oxygen is negative two ( g ) → HSO 4- aq... The reaction—not just the element that is being reduced or oxidized third reaction each equation describes a redox...... Go it never mind the correct structure of the oxidation # for nitrogen in the reactions! Miami, florida, to chicago, illinois bears oxidation number zero atom in the number. Reaction … ClO 4-1 ( perchlorate ion ) can not show any disproportionation reaction is! Terms of use & Privacy Policy, and pays \$ 5.64 for breakfast in the compound?! Following half-reaction ( with electrons not present ), how does the oxidation states are not balanced in reaction... Show any disproportionation reaction compound units: Basic a cyclist rides his at! Reaction is a type of chemical reaction shown 5280 ft = 1 ft 5280 =...: ( asap i go it never mind 'Xe ' shows reduction and F! And charges of common anions and cations limiting reagent, if any, in the reaction. And iodine undergoes reduction in these reactions., add water molecules the! In order to occur certain rules... redox reactions involve formal electron transfer and a formal change in oxidation which!

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text:
# What mass of ethanol C_2H_5OH(l) must be burned to supply 500.0 kJ of heat?

Dec 8, 2016

Based on 100% ethanol (zero water content) 16.95 g.

#### Explanation:

The enthalpy of combustion of ethanol is widely quoted in the public domain and is 1360 kJ/mol.

Therefore in order to supply 500 kJ of heat you would need to burn (500/1360) = 0.368 moles of ethanol.

The molecular weight of ethanol is 46.07 g/mol, so the mass required would be 0.368 x 46.07 = 16.95 g.

This is based on 100% ethanol - in practise ethanol will have a certain water content, and this of course does not burn or generate heat. If you have a water content of, say, 2%, then the mass of ethanol required would need to be slightly increased to compensate for this.


text:
# Python siren control

Below is some code I've put together to contol a siren for a fire service.

It works by webscraping a paging feed and looks for set triggers.

Is there a better way of doing my code or is this "pythonic" enough or can it be improved?

Im python self taught.

"""PYTHON SCRIPT TO CONTROL SIREN

This script will webscape a paging feed and
in turn activate a siren on set incidents

siren should only sound for 30secconds between 0800 -2000 hrs

this has been made so the siren only goes off for some incidents not all

by s.rees (c) 2016
"""
from scraper import Scraper
import sys
import requests
from clint.textui import puts, colored
import RPi.GPIO as GPIO
from time import sleep
import time

time = datetime.datetime.now()

print "Starting"
print "Monitoring"

#Set GPIO siren is attached too
GPIO.setmode(GPIO.BOARD)
GPIO.setup(7, GPIO.OUT)

def siren ():
GPIO.output(7, GPIO.HIGH)
sleep(30)
GPIO.output(7, GPIO.LOW)

if __name__ == "__main__":
scraper = Scraper(5, recent_messages=True)
@scraper.register_handler
def handler(msg):
# get msg from scraper and make it readable
puts(colored.yellow(msg.channel), newline=False)
puts(" [", newline=False)
puts(colored.green(msg.datetime), newline=False)
puts("] ", newline=False)
if msg.response:
puts(colored.red(msg.text))
else:
puts(msg.text)
# set agency
if 'MFS' in msg.channel:
#set unit
if 'Station' in msg.channel:
#set response type
if 'RESPOND RUBBISH OR WASTE' in msg.text:
print "Trigger found"
if (time > datetime.time(8) and time < datetime.time(20)):
print "Activate Siren"
siren ()
print 'done'
return
else:
print "out of time restrictions"
return
if 'RESPOND GRASS FIRE' in msg.text:
print "Trigger found"
if (time > datetime.time(8) and time < datetime.time(20)):
print "Activate Siren"
siren ()
print 'done'
return
else:
print "out of time restrictions"
return
else:
print "Brigade found but no trigger"
return
else:
return
scraper.run()
GPIO.cleanup()

• Hey there, I've rolled back the edit you made to this post. For one, just editing the post does not remove the content from the website. Secondly With accepting the Terms of Service and posting here, you licensed your work under CC-BY-SA. If you need to remove this for legal reasons you can try contacting StackOverflow Inc. through the [contact] option. Finally the lIcense gives you the right to dissociate your post from your name. Poke me in Code Review Chat or raise a custom flag if you have questions :) Thanks! – Vogel612 Sep 26 '18 at 12:27

Here are some code style and organization notes:

• remove unused imports (sys, requests)
• import time is also not needed since you are immediately shadowing it after by defining the variable time
• missing datetime import
• organize imports per PEP8
• use consistent 4-space indents
• no need for extra space after the function and before the opening parenthesis - e.g. siren() vs siren ()
• let's avoid hardcoding the constant values, like the number 7 and define it in a, say, GPIO_PIN "constant"
• let's move all the initial setup code to under the "main" block of the program
• use print() as a function as opposed to a statement (for Python 3.x compatibility)

Here is the improved initial part of the code without the "scraping" part:

from datetime import datetime
from time import sleep

import RPi.GPIO as GPIO
from clint.textui import puts, colored
from scraper import Scraper

GPIO_PIN = 7

def setup_gpio():
"""Sets GPIO siren is attached too."""
GPIO.setmode(GPIO.BOARD)
GPIO.setup(GPIO_PIN, GPIO.OUT)

def siren():
"""Make a siren (flash) on a desired output pin."""
GPIO.output(GPIO_PIN, GPIO.HIGH)
sleep(30)
GPIO.output(GPIO_PIN, GPIO.LOW)

if __name__ == "__main__":
print("Starting")
print("Monitoring")

now = datetime.now()

setup_gpio()

Note that I've renamed time variable to a more readable now.

As far as the rest of the code in the "main" block of the program:

• please see if there is a better way to register a handler for the scraper - instead of defining a decorator, define the handler function before the "main" block and call register_handler() passing in the function:

scraper.register_handler(handler)

• the time comparisons can be improved by using the .hour attribute of a datetime and short-circuiting:

if 8 < now.hour < 20:

• you can omit the last "else" + "return" branch

• the prints around the siren() call should probably be put into the siren() function itself to avoid the code duplication
• Thanks look better.... could i handle the if  statements any better? – shaggs Mar 9 '17 at 18:28
• @shaggs added some notes about the rest of the code. If I would have been familiar with the scraper library or the clint tool, may be I could've added some more points about that too. But, refactoring is a never-ending incremental process - you may even apply these suggestions and put the code to the code review again for a second round :) – alecxe Mar 9 '17 at 19:11
• Would it be better to make the GPIO and TRIGGERS read from a config file? – shaggs Mar 10 '17 at 0:32
• @shaggs or, you can make them command-line arguments with some default values.. – alecxe Mar 10 '17 at 1:16


text:
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