A process, composition, and kit for limiting the penetration into the skin and/or the keratinous fibers of at least one cosmetically and/or pharmaceutically active agent present in a base cosmetic and/or pharmaceutical composition for topical application and in particular for reducing the rate of penetration into the skin and/or the keratinous fibers of the active agent(s). The process includes the joint use, with the base composition, of an effective amount of a dispersion of vesicles in a medium, the vesicles comprising at least one ceramide of formula (I):

The present invention relates generally to a process for limiting the penetration into the skin and/or the keratinous fibres of at least one cosmetically and/or pharmaceutically active agent present in a base cosmetic and/or pharmaceutical composition for topical application and in particular for reducing the rate of penetration into the skin and/or the keratinous fibres of the active agent(s).
Numerous families of compounds are known which have the property of activating the penetration into the skin or the keratinous fibres of an active agent present in a cosmetic and/or pharmaceutical composition. Thus, U.S. Pat. No. 4,960,771 discloses the use, in cosmetic or pharmaceutical compositions, of oxazolidinone derivatives for increasing the penetration of active agents in the broadest sense. The use of amides for increasing this penetration is disclosed in U.S. Pat. No. 5,162,315.
U.S. Pat. Nos. 4,837,026, 4,876,249 and 5,030,629 disclose cyclic derivatives which promote the penetration of active agents.
On the other hand, very few families of compounds are known which possess the reverse activity, that is to say effectively reducing the penetration of an active agent of a cosmetic and/or pharmaceutical composition into the skin and/or the keratinous fibres.
However, some oxazolidinone derivatives exhibit this property.
It would be desirable to have available compounds or formulations having properties of reducing the penetration into the skin and/or the keratinous fibres of active agents of cosmetic and/or pharmaceutical compositions.
This is because, for certain cosmetic and/or pharmaceutical formulations for application to the skin and/or the keratinous fibres, it is highly desirable to reduce, slow down or indeed even eliminate the penetration of an active agent of the formulation into the substrate, skin or keratinous fibres to which the cosmetic and/or pharmaceutical formulation is applied, either for reasons of safety or for reasons of effectiveness.
Thus, for reasons of effectiveness, it may be important to reduce the penetration of dyes or of sunscreens into the keratinous fibres and/or the skin.
In the case of sunscreens, the protective effect of which on the skin decreases according to their penetration into the skin, it is desirable to slow down, indeed optionally even eliminate, their penetration into the skin in order to increase the effectiveness thereof.
It would thus be desirable to have available an agent which, used with a base cosmetic and/or pharmaceutical composition comprising at least one cosmetically and/or therapeutically active agent, reduces, indeed even eliminates, the penetration into the skin and/or the keratinous fibres of the cosmetically and/or therapeutically active agent.
The above aim is achieved according to the invention by the joint use, with a base cosmetic and/or pharmaceutical composition comprising at least one cosmetically and/or pharmaceutically active agent, of an effective amount of a dispersion of vesicles in a medium, the vesicles comprising at least one ceramide of formula (I):
in which R1 is chosen from saturated and unsaturated, linear and branched C1-C32, preferably C9-C25, alkyl groups optionally substituted by at least one hydroxyl group, wherein the at least one hydroxyl group is optionally esterified by a group chosen from C1-C35, preferably C8-C28, acyl groups, and R2 is chosen from saturated and unsaturated, linear and branched C1-C50, preferably C6-C35, alkyl groups optionally substituted by at least one hydroxyl group, and wherein the at least one hydroxyl group is optionally esterified by a group chosen from C1-C30, preferably C6-C24, acyl groups.
The medium in which the vesicles are dispersed is essentially an aqueous medium. This means that the medium is sufficiently aqueous so that the vesicles can be dispersed therein.
A subject-matter of the invention is therefore a process for limiting, indeed even eliminating, the penetration into the skin and/or the keratinous fibres of at least one cosmetically and/or pharmaceutically active agent present in a base cosmetic and/or dermal pharmaceutical composition, characterized in that it consists in using, jointly with the base composition, an effective amount of the dispersion of vesicles defined above.
The term xe2x80x9cjoint use of the base composition and of the dispersion of vesiclesxe2x80x9d is understood to mean either the addition of the effective amount of the dispersion of vesicles directly to the base composition before use, such as by application in the form of a film on the skin and/or the keratinous fibres, or the successive application to the skin and/or to the keratinous fibres, in the form of films, of an effective amount of the dispersion of vesicles, followed by the base composition.
The term xe2x80x9ceffective amount of the dispersion of vesiclesxe2x80x9d is understood to mean an amount of the dispersion sufficient to produce a significant effect in limiting the penetration, in particular the rate of penetration, of the active agent or agents of the base composition.
Another subject-matter of the present invention is a cosmetic or pharmaceutical composition which includes at least one cosmetically or pharmaceutically active agent, characterized in that it additionally comprises a dispersion of vesicles as defined above in an amount which is effective in limiting the penetration of the active agent or agents into the skin and/or the keratinous fibres.
The at least one ceramide of the formula (I) is chosen from known compounds. These ceramides and their processes of preparation are disclosed, inter alia, in European Patents EP-500,437, EP-647,617 and EP-790,053, the disclosures of which are specifically incorporated by reference herein.
The dispersion of vesicles can also comprise a mixture of ceramides of formula (I) and/or a stereoisomeric mixture of ceramides of formula (I).
Mention may be made, among the preferred ceramides of formula (I), of
2-(oleoylamino)octadecane-1,3-diol, 2-(lineoylamino)octadecane-1,3-diol,
2-[(2xe2x80x2-hydroxyhexadecanoyl)amino]octadecane-1,3-diol,
2-[(2xe2x80x2-hydroxydecosanoyl)amino]octadecane-1,3-diol,
2-[(D,L-mandeloyl)amino]octadecane-1,3-diol and oleyl chloride.
The particularly preferred ceramide is
2-[(2xe2x80x2-hydroxyhexadecanoyl)amino]octadecane-1,3-diol.
The dispersion of vesicles can comprise at least one second lipids other than the at least one ceramide of formula (I).
The at least one second lipid used in combination with the at least one ceramide of formula (I) in the dispersion of vesicles can be any lipid, other than the at least one ceramide of formula (I) of the dispersion, which makes possible the formation of vesicles and which does not harm the property of limiting penetration of the cosmetically and/or pharmaceutically active agent or agents of the dispersion.
A representative at least one second lipid capable of being used in combination with the at least one ceramide of formula (I), is chosen from alcohols and diols with a chain comprising 8-32 carbon atoms, preferably 12-30 carbon atoms, steroids, such as cholesterol, phospholipids, cholesteryl sulphate and phosphate, amines with a chain comprising 8-32 carbon atoms, preferably 12-30 carbon atoms, and their quaternary ammonium derivatives, dihydroxyalkylamines, polyoxyethylenated amines with a chain comprising 8-32 carbon atoms, preferably 12-30 carbon atoms, esters of aminoalcohols with a chain comprising 8-32 carbon atoms, preferably 12-30 carbon atoms, their salts and quaternary ammonium derivatives, phosphoric esters of alcohols with a chain comprising 8-32 carbon atoms, preferably 12-30 carbon atoms, such as dicetyl hydrogen phosphate and its sodium salt, alkyl sulphates, such as sodium cetyl sulphate, acids with a chain comprising 8-32 carbon atoms, preferably 12-30 carbon atoms, in the form of salts, and lipids of the type of those disclosed in Patents FR-2,315,991, 1,477,048 and 2,091,516 or in International Patent Application WO 93/01571, the disclosures of all of which are specifically incorporated by reference herein.
The term xe2x80x9clipidxe2x80x9d is understood to mean any compound having a chain chosen from saturated and unsaturated, linear and branched, lipophilic chains comprising in particular 8 to 32 carbon atoms, preferably 12 to 30 carbon atoms, for example, oleyl, lanolyl, tetradecyl, hexadecyl, isostearyl, lauryl and alkylphenyl chains. Generally, but not necessarily, these lipids furthermore comprise a hydrophilic chain, which can be an ionic or nonionic group. Mention may be made, as nonionic groups, of groups derived from polyethylene glycol. Use may also be made, as second lipids, of polyglycerol ethers, such as those disclosed in Patents FR-1,477,048, 2,091,516, 2,465,780 and 2,482,128, the disclosures of all of which are specifically incorporated by reference herein.
Use may be made, as ionic groups, of groups chosen from amphoteric, anionic and cationic groups.
The at least one second lipid which can be used in the dispersion of vesicles are representatively chosen from glycolipids, such as lactosylceramide, galactocerebroside, gangliosides and trihexosylceramide, and phospholipids, such as phosphatidylglycerol, phosphatidylinositol, phosphatidylcholine and sphingomyelin.
The at least one second lipid according to the invention can also be representatively chosen from cholesteryl salts, such as cholesteryl sulphates.
The cholesteryl sulphates can be representatively chosen from alkaline sulphates, such as sodium sulphate.
The ratio by weight of the at leasyt one ceramide of formula (I) to the possible at least one second lipid in the dispersion of vesicles generally varies from 80/20 to 20/80, such as from 70/30 to 30/70.
The total concentration of at least one ceramide of formula (I) and the at least one second lipid in the dispersion of vesicles generally varies from 0.05 to 15%, such as from 0.5 to 7.5%, with respect to the total weight of the dispersion.
The dispersion of vesicles can also comprise conventional adjuvants, such as other lipids which are different from the at least one ceramide of formula (I) and the at least one second lipid, emulsifiers, thickeners and solvents.
Representative adjuvants which can be present in the dispersion of vesicles can be chosen from fatty substances, such as mineral, animal and vegetable oils and waxes, fatty acids, fatty acid esters, such as triglycerides of fatty acids having from 6 to 18 carbon atoms and fatty alcohols; emulsifiers, such as oxyethylenated fatty alcohols and polyglycerol alkyl ethers; and solvents, such as lower monoalcohols or polyalcohols comprising 1 to 6 carbon atoms or water.
Specific mono- and polyalcohols are chosen from ethanol, isopropanol, propylene glycol, glycerol and sorbitol.
Representative fatty substances include mineral oils, such as liquid petrolatum; animal oils, such as whale, seal, menhaden, halibut liver, cod, tuna, tortoise, ox hoof, horse hoof, sheep hoof, mink, otter and marmot oils and the like; and vegetable oils, such as almond, wheat germ, olive, maize germ, jojoba, sesame, sunflower, palm, walnut, karite, shorea, macadamia and blackcurrant seed oils and the like.
Representative fatty acid esters can be chosen from esters of saturated and unsaturated C12 to C22 acids and of lower alcohols, such as isopropanol and glycerol, of saturated and unsaturated, linear and branched, C8 to C22 fatty alcohols and of C10-C22 1,2-alkanediols.
Representative fatty substances can be chosen from petrolatum, paraffin, lanolin, hydrogenated lanolin, tallow, acetylated lanolin and silicone oils.
Representative waxes can be chosen from Sipol wax, lanolin wax, beeswax, candelilla wax, microcrystalline wax, carnauba wax, spermaceti, cocoa butter, karite butter, silicone waxes, hydrogenated oils which are solid at 25xc2x0 C., sucroglycerides, Ca, Mg and Al oleates, myristates, linoleates and stearates.
Representative fatty alcohols can be chosen from lauryl, cetyl, myristyl, stearyl, palmityl and oleyl alcohols and Guerbet alcohols, such as 2-octyldodecanol, 2-decyltetradecanol and 2-hexyldecanol.
Representative emulsifying agents can be chosen from polyoxyethylenated fatty alcohols, such as lauryl, cetyl, stearyl and oleyl alcohols comprising from 2 to 20 mol of ethylene oxide and from polyglycerol alkyl ethers, such as C12-C18 alcohols comprising from 2 to 10 mol of glycerol.
It can also be useful to use thickeners, such as cellulose derivatives, polyacrylic acid derivatives, guar gum, locust bean gum or xanthan gum.
The concentration of these adjuvants in the vesicular dispersion generally varies from 0.1 to 20% with respect to the total weight of the dispersion.
The continuous phase of the vesicular dispersion can be representatively chosen from aqueous/alcoholic solutions, water and saline aqueous solutions.
The vesicles generally have a diameter which varies from 0.05 to 5 mm.
The cosmetic and/or pharmaceutical compositions of the process of the invention are all conventional cosmetic and/or pharmaceutical compositions incorporating at least one cosmetically and/or pharmaceutically active agent.
The term xe2x80x9ccosmetically and/or pharmaceutically active agentxe2x80x9d(or xe2x80x9cactive agentxe2x80x9d) is understood to mean any compound or mixture of compounds having a cosmetic and/or pharmaceutical activity.
Representative active agents can be chosen from moisturizing agents, humectants, such as glycerol, sorbitol, pentaerythritol and pyrrolidonecarboxylic acid and its salts; artificial tanning agents, such as dihydroxyacetone, erythrulose, glyceraldehyde and xcex3-dialdehydes for example tartaric aldehyde; water-soluble and liposoluble colorants; water-soluble and liposoluble sunscreens; UV stabilizers; antiperspirants; deodorants; astringents; freshening products; tonics; cicatrizing agents; keratolytic agents; depilatory agents; fragrances and scented waters; plant tissue extracts, such as polysaccharides; antidandruff agents; antiseborrhoeic agents; oxidizing agents, such as bleaching agents, for example aqueous hydrogen peroxide solution; reducing agents, such as thioglycolic acid and its salts; vitamins, such as vitamins E, F or A and their esters; hormones, enzymes, such as superoxide dismutase; antifungals; anti-inflammatories, such as hydrocortisone; antibiotics; bactericides; cytotoxic and antitumour agents; substances intended to improve the condition of dry or senile skin; tocopherols; retinoic acid; antioxidants; essential fatty acids; glycyrrhetinic acid and carotenoids.
The cosmetic and/or dermatological compositions targeted by the present invention can, of course, comprise at least one additional, sunscreen chosen from hydrophilic and lipophilic sunscreens which are active in the UVA and/or UVB regions (absorbers). These additional screening agents can be chosen in particular from cinnamic derivatives, salicylic derivatives, benzylidenecamphor derivatives, benzotriazole derivatives, benzimidazole derivatives, triazine derivatives, benzylmalonic derivatives, b,b-diphenylacrylate derivatives, p-aminobenzoic acid derivatives, and the screening polymers and silicones disclosed in Application WO/93 04665, the disclosure of which is specifically incorporated by reference. Other examples of organic screening agents are given in Patent Application EP-A-0,487,404, the disclosure of which is specifically incorporated by reference.
The preferred active agents are colorants and sunscreens.
The proportion of active agent in the base composition depends on the nature of the active agent and on the desired activity. In general, the at least one active agent represents from 0.05 to 25%, such as 0.5 to 15%, by weight of the base composition.
The base composition can comprise other conventional adjuvants in the conventional proportions. In particular, it can comprise lipids, in particular lipids other than the at least one ceramide of formula (I) described in connection with the vesicular dispersion.
In particular, the base composition can comprise a liquid phase dispersed in an aqueous phase, the constituent(s) of which can be chosen from the group formed by oils, such as esters of fatty acids and of polyols and esters of fatty acids and of branched alcohols of formula R3xe2x80x94COOxe2x80x94R4, in which formula R3 is chosen from residues of higher C7-C19 fatty acids and R4 is chosen from branched C3-C20 hydrocarbonaceous chains; hydrocarbons, such as hexadecane or liquid paraffin; perhydrosqualene; halogenated hydrocarbons, such as perfluorodecahydronaphthalene; perfluorotributylamine; polysiloxanes; esters of organic acids; ethers and polyethers.
This liquid phase can include at least one liposoluble active agent, such as liposoluble sunscreens, tocopherols, vitamins E and F, vitamin A and its esters, retinoic acid, antioxidants, essential fatty acids, glycyrrhetinic acid, keratolytic agents and carotenoids.
The active agents can be dissolved or in the form of a dispersion in the cosmetically and/or pharmaceutically acceptable medium of the base composition. In particular, the active agents can be in the form of a dispersion of vesicles in the medium of the base composition. In the case of water-soluble active agents, they can be present in an aqueous phase encapsulated in vesicles composed of one or more lipids. In the case of liposoluble active agents, they are then found incorporated in the lipid layers of the vesicles.
As indicated above, in the process of the invention, the dispersion of vesicles can be incorporated in the base composition. The incorporation of the dispersion of vesicles can take place either by preparing the dispersion of vesicles and the base composition separately and by combining them in an appropriate fashion or by forming the dispersion of vesicles directly in the base composition during the preparation of the base composition (in situ formation).
In the case of the introduction of a preprepared dispersion of vesicles into a base composition, the amount of dispersion introduced is such that the concentration of the at least one ceramide of formula (I) and of the at least one second lipid in the final composition varies from 0.05 to 15% by weight, such as from 0.5 to 7.5% by weight.
Likewise, when the dispersion of vesicles is formed in situ in the base composition, the total amount of the at least one ceramide of formula (I) and of the at least one second lipid which is introduced is such that the concentration of the at least one ceramide of formula (I) and of the at least one second lipid represents from 0.05 to 15%, such as from 0.5 to 7.5%, by weight of the final composition. In all cases, the ratio by weight of the at least one ceramide of formula (I) to the at least one second lipid varies from 80/20 to 20/80, such as 70/30 to 30/70, in the final compositions.
In the case of the formation of the dispersion of vesicles in situ, during the formulation of the base composition, the at least one active agent can be incorporated in the vesicles of the dispersion of vesicles either in the form of an aqueous solution encapsulated in the lipid phase of the vesicles or in the lipid phase of the vesicles, if the active agent is liposoluble.
The joint use of the dispersion of vesicles and of the base composition can take place by applying first of all the dispersion of vesicles to the skin and/or the keratinous fibres, in order to form a film, and by then applying the base composition comprising the at least one active agent to the film formed.
In this form of use, the dispersion of vesicles and the base composition can be provided in the form of a kit, that is to say be packaged in separate containers present in the same packaging.
The vesicles can be obtained in particular according to the process disclosed in French Patent 2,315,991 of L""Orxc3xa9al, S. A., the disclosure of which is incorporated by reference, according to which a dispersion of vesicles, composed of organized molecular layers including an aqueous phase to be encapsulated, is prepared by bringing into contact, on the one hand, at least one lipid compound, in particular of formula (I), in combination with at least one other lipid, as defined above and, on the other hand, the aqueous phase to be encapsulated in the vesicles, by stirring in order to ensure mixing and to obtain a lamellar phase, by subsequently adding a dispersion liquid in an amount greater than the amount of lamellar phase obtained, and by vigourously shaking for a period of time ranging from 15 minutes to 3 hours approximately.
The ratio by weight of the aqueous dispersion phase which is added to the lamellar phase, which is dispersed, can be from 2:1 to 100:1; the dispersion phase and the aqueous phase to be encapsulated can be isoosmotic.
Stirring can be carried out by means of a shaker. The process can, for example, be carried out at a temperature from 30xc2x0 to 120xc2x0 C.
The dispersion can subsequently be treated by ultrasound and/or be homogenized by a conventional mechanical means.
Another preparation process can comprise using the process known as the REV (reverse-phase evaporation vesicle) process described in Proc. Natl. Acad. Sci. USA., Vol. 75, No. 9, pages 4194-4198 (1978), by Szoka and Papahadjopoulos, the disclosure of which is incorporated by reference.
The process of the invention can be applied in the field of caring for the skin and/or the keratinous fibres, such as the hair, and in the make-up field. In particular, it can advantageously be applied in the field of protecting against sunlight, where, by slowing down penetration of the sunscreen into the skin, it prolongs the protective activity of the screening agent, and in the field of colouring the hair, where it restricts the penetration of colorants into the skin and/or the scalp.
In the following examples, which illustrate the present invention, all percentages and parts are expressed by weight, unless otherwise indicated.

Process for limiting the penetration into the skin and/or the keratinous fibres of an active cosmetic and/or pharmaceutical agent

Abstract: wherein R1 is chosen from saturated and unsaturated, linear and branched C1-C32 alkyl groups optionally substituted by at least one hydroxyl group, wherein said at least one hydroxyl group is optionally esterified by a group chosen from C1-C35 acyls; and R2 is chosen from saturated and unsaturated, linear and branched C1-C50 alkyl groups optionally substituted by at least one hydroxyl groups, and wherein said at least one hydroxyl group is optionally esterified by a group chosen from C1-C30 acyls.


An apparatus for combining the outputs from multiple gain elements of an array within a single resonator cavity to achieve a predetermined spectral output or improved output power is provided. The resonator cavity is comprised of a reflector, preferably deposited on the back facets of the gain element array, and an output coupler. Interposed between the gain element array and the output coupler are an optical element and a reflective diffraction grating. The optical element can be comprised of either a GRIN lens or a uniform index element with a shaped, reflectively coated back surface. The output coupler can be directly coupled to an optical fiber, for example by burying the output coupler into the entrance aperture of the fiber.

The present invention relates generally to optical systems and, more particularly, to an apparatus for combining the outputs from multiple gain elements of an array within a single resonator cavity.
Semiconductor lasers utilizing GaAlAs, GaAs, InGaAs, and other materials have been developed that have found application in a variety of fields including telecommunications, medical testing/treatment, optical measurements, and optical disk reading/writing. Such lasers can be designed with either a single gain element or with an array of discrete gain elements. In order to utilize such lasers, it is often desirable to couple the output from several discrete gain elements into a single output beam, thereby achieving greater output power, spectral bandwidth, beam brightness, etc.
U.S. Pat. No. 5,802,092 discloses a diode laser source in which the output from each of a plurality of concurrently driven laser gain elements within a single diode array are passed through suitable beam filling and focusing optics in order to converge the outputs to a single overlapping spot. Each of the laser gain elements is individually addressable, thus allowing individual elements to fail with only a marginal effect on the optical power and brightness of the overlapping spot. As a result of this design, the lifetime of the device is improved.
U.S. Pat. No. 5,513,201 discloses a system designed to achieve an increased energy density at the light focus of a linear semiconductor laser array. The system utilizes an optical path rotating device interposed between a pair of collimating elements. Each of the collimating elements is designed to provide collimation along a single axis. The system also includes a focussing element for condensing the laser beams that have been collimated in both directions.
U.S. Pat. No. 4,494,235 discloses a frequency stabilized semiconductor laser which utilizes a Fourier diffraction grating with a corrugation having continuous first order differential coefficients. In operation, the semiconductor laser emits a beam from one facet into the diffraction grating. The diffracted light from the grating is fed back into the semiconductor laser in such a way as to cause the semiconductor to emit an output beam with a stable wavelength from another facet. The grating can be rotated to achieve different wavelengths.
U.S. Pat. No. 5,276,695 discloses a tunable, optically pumped, solid state laser which simultaneously emits light at one or more wavelengths. The resonator uses two or more end reflective elements, two curved fold mirrors, and an output coupler reflective element. A wavelength dispersive element, e.g., a prism, is disposed in the reflective path in the laser resonator cavity between one fold mirror and the end reflective element, the wavelength dispersive element providing wavelength tuning capability. In order to optimize the wavelength dispersion performance of the dispersive element, the laser cavity mode is collimated as it passes through the element.
U.S. Pat. No. 5,541,946 discloses a laser which simultaneously emits light at two or more wavelengths. The laser includes at least two gain elements pumped by a single optical pumping source, each gain element generating a different wavelength. The resonator uses two plane highly reflective end elements, three concave fold elements, and an output coupler. A wavelength dispersive element, e.g., a prism, is disposed in the reflective path in the laser resonator cavity to provide a spatially separate path for each of the simultaneously emitted wavelengths. In order to optimize the wavelength dispersion performance of the dispersive element, the laser cavity mode is collimated as it passes through the element.
A tunable semiconductor laser with a single output is disclosed by Soole et al. in Wavelength-selectable Laser Emission from a Multistripe Array Grating Integrated Cavity Laser, Applied Physics Letters 61 (23), Dec. 7, 1992. In the disclosed system, an array of active laser elements is optically coupled to a fixed, etched-in, diffraction grating. Wavelength tuning is accomplished through selective activation of individual laser elements, the wavelength being determined by the position of the activated laser element relative to the etched-in grating.
Although a variety of intracavity beam combiners have been designed, these devices typically require very precise alignment. Accordingly, what is needed in the art is a robust intracavity beam combining system utilizing multiple discrete gain elements and a resonator structure that is primarily contained within a single optical element, thus minimizing system alignment requirements. The present invention provides such a device.
The present invention provides an apparatus for combining the outputs from multiple gain elements of an array within a single resonator cavity using a diffraction grating. The apparatus can be used to achieve a predetermined spectral output or to achieve a relatively high output power from an array of low power laser elements. The multiple gain element array can be a semiconductor diode laser array, an array of side or end pumped solid state laser materials, or a fiber laser array.
In at least one embodiment of the invention, the resonator cavity is comprised of a reflector, preferably deposited on the back facets of the gain element array, and an output coupler. Interposed between the gain element array and the output coupler is an approximately xc2xc pitch GRIN lens and a reflective diffraction grating, the reflective diffraction grating coupled to the back surface of the GRIN lens. The output coupler is preferably coupled to an optical fiber.
In at least one other embodiment of the invention, interposed between the gain element array and the output coupler of the resonator cavity is an optical element in which the back surface is shaped and onto which a highly reflective coating is deposited. Coupled to the front surface of the optical element is a diffraction grating. An entrance aperture on the front surface of the optical element allows light from the gain element array to enter the optic. The light from each element of the array is reflected off of the back surface of the optic onto the diffraction grating, reflected by the diffraction grating back towards the back surface of the optic, and focused by the back surface of the optic onto the output coupler.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.


A HiNAND array with a hierarchical-BL scheme configured to divide a large global bit line (GBL) capacitance into J number of small local bit line (LBL) capacitances for reducing bit line precharge voltage and discharge time to achieve faster Read and Program-Verify speed, lower power consumption, lower latency, and lower word line disturbance for a reliable DRAM-like latch sensing. A reduced precharge voltage can be increased by M-fold (M≧2) using a Multiplier between each bitline and each Latch sense amplifier (SA). Between each Multiplier and each Latch SA, there is a Connector with two optional designs for either fully passing a sense voltage to the Latch SA with a same-polarity and value or reversing the polarity the sensing voltage with additional amplification. The Latch SA is configured to transfer stored threshold states of a memory cell into a bit of a page buffer.

This invention relates generally to memory architecture for improving NAND Read operation. More specifically, various embodiments of the present invention provide a NAND Read scheme for drastic reduction over the high WL-disturbance, high BL-precharge power consumption, and high latency issues in an extremely high-density NAND (HiNAND) memory array, regardless of data storage types such as SLC, MLC, TLC, XLC or Analog storages, regardless of 2-poly floating-gate NAND cell or 1-poly charge-trapping MONOS or SONOS cell, regardless of NMOS cell or PMOS cell, regardless of 2D or 3D NAND technologies.
Nonvolatile memory (NVM) is well known in the art. NVMs that provide the in-system or in-circuit repeatedly electrically programmable and erasable functions today include three major standalone NVMs such as EEPROM, NOR, and NAND Flash Memory and one Embedded Flash, eFlash, memory. All above four NVMs are based on varied technologies.
The EEPROM is suitable for the Byte-alterable Data storage with the highest density below 4 Mb at 0.13 μm node. The NOR flash is suitable for the block-alterable Code storage with the highest density below 8 Gb at 45 nm node. The eFlash is suitable for the page-alterable Code storages with the highest density below 64 Mb at 65 nm node. Lastly, NAND flash is suitable for the sector-alterable Data storage with the highest density below 256 Gb at 19 nm node in MLC storage.
Currently, NAND flash memory has achieved the highest scalability, density and smallest feature of 1× nm node in 2012. The mainstream standalone NAND in mass production is mainly based on 2-poly floating-gate NMOS device, which employs 20V but the extremely low current FN channel-erase and FN channel-program schemes. The NAND flash device and cell array comprises a plurality of NAND Strings that are organized in a matrix with a plurality of rows and columns. Each String is further comprised of a plurality of NMOS NAND cells connected in series sandwiched by two NMOS 1-poly String-select transistors located on top and bottom of a NAND String. The number of NAND flash cells in one String can be made of 8, 16, 32, 64, 128 or arbitrary integer number, depending on NAND density requirement and applications.
Each NAND cell has several different types of storages that include SLC (1 bit per cell), MLC (2 bits per cell), TLC (3 bits per cell), XLC (4 bits per cell) and even Analog storage that stores more than 4 bits.
In three key operations of prior-art NAND such as Erase, Program and Read, of which require either verification in both Erase and Program operations or Read to ensure the desired data or NAND cell's threshold state Vt have been accurately programmed and erased into the selected NAND flash cells in the right locations in accordance with the desired values, storage types and time specs by checking or reading out the selected cells' Vt after Erase and Program operations.
In the specification, a 2-poly NAND array comprising a plurality of 32T NAND-Strings is assumed and used as an example to describe both the conventional NAND Read operation and a HiNAND Read operation based on the present invention, although other String sizes (8, 16, 64, 128, etc.) can be applied. When programming NAND cells in the same selected WL, FN-channel scheme is commonly used for Erase and Program operations. In a typical NAND Program operation, a high step-rising program voltage, Vpgm from 15V to 25V, is applied to one selected WLn but a Vpass(program) of around 10V is applied to the rest of 31 non-selected WLs in the selected Strings along with the gate of bottom String-select transistor connected to Vss and the gate of top String-select transistor connected to Vdd.
As a result, 31 NAND cells in the same String are in conduction-state while the String's bit line is grounded. The plurality of electrons from the selected NAND cells' channels are injected into the floating gate layer, Poly1, and NAND cells' threshold voltage, Vt, are raised from an erased Vt0, E-state, with a negative value to a desired positive value of Vt1, which is referred as a programmed state, A-state.
Similarly, when programming a 1-poly NAND flash device using same FN-channel scheme, a similar step-rising high program voltage, Vpgm, is also applied to the selected 1-poly NAND's control gate with its bit line is grounded. This Vpgm voltage can be same or lower than the Vpgm applied to the above 2-poly NAND flash memory, depending on the coupling ratio from Poly gate to Nitride layer. Electrons from 1-poly NAND cell's channel are then injected into its charge-trapping layer. The step-rising Vpgm voltage is typically set to be between 15V to 25V with a typical increment of ΔVpgm, ranging from 0.2V to 0.4V.
More information about the programming methods can be found in U.S. Pat. No. 6,859,397, titled "Source Side Boosting Technique for Non-volatile Memory;" and U.S. Pat. No. 6,917,542, titled "Detecting Over Programmed Memory;" and U.S. Pat. No. 6,888,758, titled "Programming Non-Volatile Memory," which are incorporated as references herein.
In many cases, Vpgm pulse is applied to the selected WLn of NAND associated with several MHV pass-WL voltages such as Vpass(program) voltages such as Vpass1, Vpass2 and others applied to the non-selected WLn−1 and WLn+1 and the rest of WLn in the selected NAND strings of the selected blocks.
A series of Vpgm pulses (referred to as the programming gate pulses), with the magnitude of the pulses increasing are applied to WLn. Between each rising-step Vpgm pulse, a set of single or multiple program verify pulses like Read operation are performed to determine whether the selected NAND cells(s) in the selected page or WL are being programmed into the desired programmed Vtn values. The programmed Vtn values are determined by the type of storages such as SLC (1-bit per cell), MLC (2-bit per cell), TLC (3-bit per cell), XLC (4-bit per cell) or Analog storage (more than 4-bit per cell).
Since Program-Verify operation is like the regular Read operation, the previously mentioned BL-precharge cycle and discharge cycle would be the same. Therefore, during each Program-Verify cycle, a NAND flash memory has to precharge all long BLs' large capacitance from Vss to VBL as described before. As a result, a large BL precharge current occurs and the large Vpass(read) 6V WL disturbance will be induced on NAND cell. In addition, Program-Verify cycle also has a long latency as Read due to the discharge process starts from a high value of VBL, which ranges from 0.8V to Vdd in today's NAND design.
If any of the selected NAND cells have reached their targeted programmed Vts as determined in Program-Verify step, then the further programs have to be stopped on those NAND cells to avoid or inhibit over-programming into next higher wrong Vt state. For those NAND cells' Vt that do not reach the desired value after Program-Verify operation, then the Vpgm pulses continue applying to those NAND cells in the selected page or WL associated with Vpass of 10V or other HV to the non-selected WLs. If the desired Vts are not reached, then the iterative programming and verify pulses would be repeatedly applied to those cells. Until all NAND cells in the selected page have been programmed successfully into the desired Vt states, then the programming and Program-Verify operations of the selected page would be stopped. The Program and Program-Verify operations would be continued on those remaining pages in the preferred sequence from String bottom to the string top in the selected strings of the selected blocks of the NAND memory. As the Program and Program-Verify operation repeats, the BL precharge current and Vpass WL-induced disturbance will be multiplied.
Typically, each NAND String physically comprises 16, 32, 64, or even 128 WLs and the MLC page number is doubled to SLC page number, TLC density is tripled and XLC density is quadrupled.
A multi-state NAND memory device stores multiple bits of data per NAND cell by differentiating multiple distinct valid Vtn distributions separated by some preferred forbidden ranges such as ΔVtn. Each distinct Vtn has a distribution between Vtnmax and Vtnmin. Each ΔVtn is defined to be a value of Vtnmin of a higher-level state minus the Vtnmax of a lower-level Vtn state. Each Vtn is defined corresponding to a predetermined value for the set of data bits encoded in NAND device.
As the number of bits of data per NAND cell is increased from SLC to MLC, TLC, and XLC, the number of valid Vtn are increased from 2 to 4, 8 and 16. As a result, the NAND data capacity is drastically increased, thus the die cost is greatly reduced.
There is a tradeoff. When each NAND cell storage capacity is programmed to increase, however, the programming time also increases and NAND cell's data reliability greatly degrades accordingly. In some applications, the increased programming time and the lower data reliability cannot be accepted.
But for this invention, we will look into more into the NAND Read and Program-Verify disturbance and precharge BL current consumption issues.
Why does a regular NAND Read operation consume so much power? This is due to the fundamentals of the NAND sensing scheme. Firstly, to read or verify a stored Vt out from a selected NAND cell in the selected NAND string and in a selected page (WLn), today's NAND scheme pre-charges each BL from Vss to a value of VBL first because the resistance of the NAND string is larger than 1 M-ohms if the sensing current is less than 1 μA. Later, to distinguish the NAND cell's Vt, it is determined by reading the final VBL voltage against the VRD in the selected WL. If VBL is discharged to Vss, then NAND cell Vt=VRD. If VBL is not discharged and retains the initial pre-charged VBL, then the NAND cell's Vt is higher than VRD applied on the selected WL. The Read operation of getting the right NAND Vt has to be continued until a new value of VRD is found to discharge the initial VBL to Vss.
In prior-art NAND array architecture, each BL is connected to a plurality of NAND Strings by a long metal line such as metal1 line running in Y-direction with a capacitance value of around 3-5 pf. The VBL value ranges from 0.8V to Vdd. With a lower VBL value, less number of BLs and a shorter BL metal1 line length would reduce each BL and total BL capacitances, thus reducing total each and total BL pre-charge current in NAND Read and Verification cycles.
In one option of the conventional NAND array, the whole physical BLs in one physical page of the NAND array are being commonly divided into two sub-pages such as the odd page and the even page with half of whole BLs. In another option of the conventional NAND, the whole BLs in NAND array are read out simultaneously without being divided into the odd and even pages for less WL-disturbance and it was referred as All-BL Read or All-BL Verify. The total numbers of BLs in each NAND's physical page today can be as high as 8 KB or 65,536, not including the spare BLs for ECC syndrome bytes storage. For example, one NAND page size of 512B requiring extra 16B to store the regular NAND data and ECC spared data respectively. Each BL is connected to a plurality of NAND Strings by a metal, such as metal1 line, with a capacitance value around 3-5 pf, in NAND density above 16 Gb. In a NAND technology node above 4× nm, the BL capacitance mainly attribute to two factors. The first factor is the area of BL metal1 overlaps the flash cells and Strings that are formed in a triple P-well within the Deep N-well on top of P-substrate. The second factor is the N+/P junction capacitance occurs at each NAND String's contact areas. Since only one contact is shared by two long NAND Strings in Y-direction, the number of N+/P Contacts and its capacitance is much smaller than the BL-long metal1 line. Thus, N+/P capacitance is negligible as compared to BL metal1.
When scaling down below 3× nm node, the BL metal1 proximity effect in NAND flash array layout will induce a significant parasitic capacitance between two adjacent BLs. As a result in nGb-density NAND array, each BL will bear a long metal1 BL with a large capacitance comprising over metal1 overlapping area to flash cells on p-substrate and coupling parasitic BL capacitance due to the BL-proximity effect.
During a NAND Read or Program- and Erase-Verification operations, all BLs or one-half of BLs such as odd and even BLs have to be pre-charged from Vss to a desired high value, ranging from 0.8V to Vdd. This precharge operation is done on maximum 8 KB BLs as defined in one physical page. The total precharge current=N×Vdd×CAPBL/Pre-charge time, where N is the number of total BLs. The value of N is 65,536 for 8 KB page and CAPBL is 3 pf. The typical BL precharge time was designed to be around 10 μS today. As a result, a total peak precharge BL current of more than 100 mA will occur in each Read or each Verification cycle. This huge GBL pre-charge current needs to be reduced for a longer storage for battery-driven handheld mobile NAND.
Secondly, a Read-induced or Verify-induced WL-disturbance in NAND flash memory is also frequently encountered during the regular Read and Verify operations and becomes worsen after repeated Read and Verify operations in prior-art NAND flash memory. Just a repeated reading and verification of NAND can quickly corrupt the stored data in each NAND flash cell. Although this corrupted data can be fixed by using a more sophisticated ECC algorithm of flash controller, NAND flash memory will be rendered useless when the Read-induced and Verify-induced errors are too high beyond ECC's fixing capability.
Why a regular Read and Verify operations has induced severe WL-disturbance issue in prior-art NAND flash memory? It is again due to NAND's unique structure in each NAND String. To read the selected cell of each String, the non-selected NAND cells with different stored Vts have to be all in the conduction state. To ensure all of these 31 non-selected NAND cells in a 32T NAND string, the 31 non-selected WLs have to be coupled with a MHV Vpass(read) voltage of around 6.0V, which is higher than the maximum stored Vt of around 4.0V. This Vpass(read) voltage on top gate would couple to the poly1 floating gate of nitride charge layer to attract the electronics from NAND cell's channel. This is like a soft-writing of the NAND cell. As a result, each NAND's Vt would be gradually increased when Read cycles increases.
Take the Read operation of a NAND array comprising a plurality of 32T-strings as an example. The only one selected WL voltage is coupled with one or several preferred VRD voltages but the rest of 31 non-selected WLs and two top and bottom string-select NMOS transistors are coupled with a MHV voltage, Vpass(read). MHV stands for a medium high voltage around 6.0V.
For example, a SLC Read and Verify operations, only one VRD value is needed, VRD=0V, to distinguish the erased state of a negative Vt0≦−0.7V with data "1" from the programmed positive Vt1≧1.0V with a data "0". In this SLC Read operation, only one BL-precharge cycle is required, thus one huge BL precharge current happens.
For a MLC Read operation, three VRD values of VRD1=0V, VRD2=1.5V, VRD3=3.0V are required to distinguished one erased state and three program states such as Vt0 (E-state, 11), Vt1 (A-state, 01), Vt2 (B-state, 00) and Vt3 (C-state, 10), where Vt0<Vt1<Vt2<Vt3. In this MLC Read operation, still only one BL-precharge cycles is required by using the step-rise three VRD voltages to read four logic data with stored Vts. In other words, a MLC Read operation consumes one BL pre-charge current as a SLC Read operation.
Similarly, for a TLC Read operation, there are seven VRD values to distinguish one erased negative-Vt state, Vt0 from the remaining seven programmed positive-Vt states such as Vt1, Vt2, Vt3, Vt4, Vt5, Vt6, and Vt7. A similar step-rise VRD can be applied to the selected WL but still only one BL-precharge current happens in whole TLC Read cycle.
Additionally, for a XLC Read operation, there are fifteen VRD values to distinguish one erased negative-Vt state, Vt0 and remaining fifteen programmed positive-Vt states such as Vt1, Vt2, Vt3, Vt4, Vt5, Vt6, Vt7, Vt8, Vt9, Vt10, Vt11, Vt12, Vt13, Vt14, and Vt15. A similar step-rise VRD can be applied to the selected WL but still only one BL-precharge current happens in whole XLC Read cycle.
All non-selected 31 WLs and two String-select transistors of the selected NAND Strings are applied with a MHV voltage, Vpass(read). The reason is to turn these 31 NAND flash cells into a conduction state to allow the accurate Vt differentiation of one selected NAND cell in the selected WL. Since the maximum program Vtn is set to be around 4.0V, thus Vpass(read) 6.0V is required to turn the maximum-Vt NAND cells into the conduction state for a Read latency spec typically set to be 20 μs. Additionally, the reason to couple the identical Vpass(read) voltage to the top and bottom String-select transistors' gates is to further reduce their turn-on resistance so that a faster BL discharge speed, thus faster Read speed can be achieved.
Although the Vpass(read) of 6.0V in NAND Read operation is lower than the Vpass(program) of 10V, these 31 non-selected NAND cells would suffer a soft programming because the 6.0V gate will be coupled to floating-gate layer. The positive floating-gate voltage will attract the electrons in NAND's channel to inject across NAND thin tunnel oxide layer.
As a result in the repeated NAND Reading, more and more electrons would be gradually injected into all 32 NAND cells' floating-gate in the selected NAND String. Thus, the Vts of 32 NAND cells after each NAND read would be increased unintentionally.
The most severe soft-writing due to Vpass(read) would happen to those NAND cells with the lowest Vt states such as the E-state with Vt≦−0.7V and the A-state=0.7V.
When scaling below 3× nm, the BL proximity effect will result in a severe BL coupling noise to those NAND read operation with a BL-precharge followed a BL-discharge scheme. Since after BL-precharge period, the BL pull-up device is being shut off. In subsequent Read after precharge cycle, the discharged BLs will couple to those adjacent non-discharged BLs to ground, thus it will result in the fault reading. In order to effectively prevent this adjacent BL coupling noise, the conventional NAND's each physical page is divided into two sub-pages such as odd and even sub-pages. During the odd page read, one option of the BLs' voltage of even page are precharged to a VBL voltage for avoiding the Vpass(read) WL-induced disturbance due to the WL-coupling self-boosting effect in the NAND cell channels of the even page but at the expense of consuming one ½-page BL precharge current. The second option of the BLs' voltage of even page are reset to Vss for avoiding consumption of BL precharge current on even page but at the expense of suffering one ½-page Vpass(read) WL-induced disturbance.
For each Read operation, a predetermined the VRD is applied to the selected WL and the a WL-pass voltage, Vpass, ranging from 5-7V is applied to the unselected N−1 WLs to turn the N−1 NAND cells into the conduction state so that the On or Off state of the selected NAND cell can be accurately distinguished. The single VRD value of 0V is for SLC reading, but three distinct VRD values of 0V, 1.5V and 3V are for MLC reading and seven distinct VRD values are for TLC reading and 15 distinct VRD values are for XLC read.
Lastly, one of the drawbacks of the prior-art NAND, the SLC page-read latency averagely is about 20 μs which is too slow as compared to today's fast random NOR read latency of 100 ns for a Gb-density. Since each Read operation is from a NAND String, all the non-selected cells in the non-selected WLs or pages suffer one time of Vpass WL disturbance. MLC will suffer 3 times longer delay of about 60 μs, TLC will suffer 7 times longer delay of about 140 μs and XLC will suffer 15 times longer delay of about 300 μs. As a result, the Vpass WL disturbance becomes more severe issue in NAND memory with higher storage compression. In addition, each Read of NAND programmed states of A, B and C would consume one high BLn precharge current.
In summary, BL pre-charge operation consumes too much power in prior-art NAND Read operation, regardless of SLC, MLC, TLC and XLC, regardless of ALL BL Read or odd and even BL Read schemes.
Furthermore, in today's NAND flash market demand, more MLC, TLC and XLC storages than SLC are strongly required to further reduce the die cost by ½, ⅓, or even ¼. A larger P/E endurance cycles or a longer lifespan for a less Read disturbance and less Read latency for a superior performance are also very important.
Thus an urgent need to reduce the Read disturbances, power-consumption as well as Read latency in the conventional NAND strings and array is strongly required.

Low disturbance, power-consumption, and latency in NAND read and program-verify operations


The connector block allows the transmission of the shock wave that travels along the donor tube (1) to several receiver tubes (4), setting between them a delay device (6) with its corresponding pyrotechnic delay formula (8), and an explosive charge (9), all these components being integrated within the body (4) of the connector block in such a way that the explosive charge (9) is parallel and adjacent to the receiver tubes (10), which are on a parallel plane to said explosive charge and are positioned at right angles to it, inside which a detonator is housed. The explosive charge (9) is positioned so that all the tubes (10) held in the slot (11) are initiated in similar conditions, without suffering the effects of structural differences, thus achieving a homogeneous and safe initiation that does not produce metal shrapnel that could damage the receiver tubes (10).

Until about 1970, sequential blasts were carried out almost exclusively using electric detonators that were connected to each other following the usual techniques for electrical circuits, that is, series connections and parallel connections.
These blasts were also carried out by initiating them using a detonator cord and sequencing them by means of so-called "detonator cord relays" that consisted of metal or plastic sections that would allow the donor and receiver detonating cords to be linked, inserting a specific delay time between their respective detonations.
It seems that for non-electric detonators initiated via shock tube, it was necessary to develop connection systems that allowed sequential blasts to be designed and carried out for a large number of blast-holes, which was mainly achieved by starting the blast-hole detonators via trunk lines of detonating cord or by means of surface detonators (the same for non-electric detonators initiated via shock tube).
In both cases (trunk lines of detonating cord and the use of surface detonators) duct tape was used to fix the tubes that were going to be initiated (receivers) to the detonating cord or to the detonator that was going to initiate them (donor), a slow and imprecise method that gave rise to the use of fast connectors, which were generally made of plastic.
The connectors used to initiate receiver shock tubes by means of detonators consisted of small plastic boxes inside which the detonator was housed, and they had a cover on the side which allowed the detonator tubes that were going to be initiated (receivers) to be attached and fixed to the housing of the detonator that was going to initiate them (donor), so that the axis of the donor detonator and the axes of the receiver tubes remained visibly parallel.
The drawbacks of these connectors resulted from the direction of the initiating energy of a detonator and from its excessive power, causing a large amount of shrapnel that destroyed the receiver tubes, as well as making an excessive amount of noise.
For these reasons, the next generation of connectors, the current state of the art, consists of donor detonators with a lower charge and plastic parts that allow the receiver tubes to be quickly attached to the explosive charge of the donor detonator, so that the axis of this and the axes of the receiver tubes are at right angles, with the aim of avoiding the problems of the direction of the initiating energy of the detonator's charge.
Thus, for example, U.S. Pat. No. 5,423,263 granted to Dyno Nobel Inc. on 13 Jun. 1995 discloses a connector block that transfers the initiation from a detonator inserted into the connector block to one or more shock tubes.
U.S. Pat. Nos. 5,171,935 and 5,398,611 from 15 Dec. 1992 and 21 Mar. 1995 respectively, granted to Ensign Bickford Company, describe plastic blocks with a space inside to house a low-energy detonator, the active end of which is next to a slot into which the shock tubes to be initiated are inserted.
However, reducing the charge of the donor detonator whilst keeping the same size diameter means that said charge must be concentrated into a space at the end of it, which in turn causes new problems that have been covered by different inventions, some of which aim to position the detonator more precisely within its housing.
Thus, in U.S. Pat. No. 5,499,581 granted to Ensign Bickford Company on 19 Mar. 1996, a method is described for better positioning and fixing of the initiating detonator in the corresponding casing inside the connector, by means of a moveable fixture.
On many occasions the proposed innovations aim to facilitate or improve the positioning of the receiver shock tubes in the slot next to the end of the donor detonator that contains the explosive charge.
Thus, U.S. Pat. No. 5,703,319 granted to Ensign Bickford Company on 30 Dec. 1997 describes a connector block that has houses a low energy detonator, as well as a clip forming a slot with the end of the detonator where the shock tubes to be initiated are situated.
Lastly, U.S. Pat. No. 5,792,975 granted to the same company on 11 Aug. 1998 includes several different improvements in the functionality of the connector block and provides a method for assembling the detonator inside said connector block, giving a combination of detonator and connector.
The solutions available with the current state of the art show a connector block with a housing into which a detonator is inserted that is positioned and fixed by means of various mechanisms. The explosive charge of the detonator is situated in such a way that, together with the (more or less) flexible piece that forms part of the connector block, there is a slot in which one or several shock tubes to be initiated (receivers) can be lodged.
By way of an example, international patent WO 03/023316 A1 from 20 Mar. 2003, granted to Orica Explosives Technology, discloses a device comprising a plastic connector block housing a detonator with an active end (from the initiation point of view) around which the receiver shock tubes are situated, immobilised by a clip and a closure that prevents their accidental removal.
Several problems could be linked to connector blocks manufactured according to the current state of the art, among which is the possibility of either intentionally or inadvertently separating the connector block from the detonator housed inside it and using it for purposes other than those for which it was designed and manufactured.
On the other hand, the dimensions and shapes of detonators, as well as the techniques used to manufacture the metal casing of which they are made, determine the fact that the back of the detonator is an area of irregular behaviour when there is a detonation transmission, which can cause shrapnel to destroy some of the receiver tubes or can limit the number of receiver tubes that may be initiated simultaneously.
Some solutions using energy produced on the cylindrical surfaces of the detonator, instead of the end, to initiate the tubes, require special detonators that are difficult or expensive to produce, unless one renounces the idea of using low energy detonators.
Low energy detonators have the advantage of greatly reducing the amount of metal shrapnel produced, but it does not completely avoid this.

Direct load, detonator-less connector for shock tubes


A process for manufacturing a self-sealing elastomer composition, said process comprising the following steps: a masterbatch, comprising at least one diene elastomer and more than 30 phr of a hydrocarbon resin, is firstly manufactured by compounding these various components in a mixer at a temperature or up to a temperature called the “hot compounding” temperature which is above the softening point of the hydrocarbon resin; and then at least one crosslinking system is incorporated into the masterbatch thus prepared, by compounding everything in the same mixer or in a different mixer, at a temperature or up to a temperature which is kept below 100° C., in order to obtain said self-sealing composition.

Particularly in recent years, tire manufacturers have been making considerable efforts to develop novel solutions to a problem dating from the very first use of tired wheels of the inflatable type, namely the problem of how to allow the vehicle to continue to travel despite a considerable or complete loss of pressure of one or more tires. For decades, the spare tire was considered to be the only and universal solution. Then, more recently, the substantial advantages associated with its possible omission have become apparent. The concept of "extended mobility" was developed. The associated techniques allow the same tire to run, depending on certain limits to be respected, after a puncture or a drop in pressure. This makes it possible for example to drive to a breakdown point without having to stop, often in hazardous circumstances, to fit the spare tire.
Self-sealing compositions that allow such an objective to be achieved, and which by definition are capable of automatically ensuring, that is to say without external intervention, that a tire is sealed in the event of a perforation of the latter by a foreign body, such as a nail, are particularly difficult to develop.
To be useable, a self-sealing layer must satisfy many conditions of a physical and chemical nature. In particular, it must be effective over a very wide range of operating temperatures, and be so throughout the lifetime of the tires. It must be capable of closing off the hole when the perforating object remains in place and, when the latter is expelled, said self-sealing layer must be able to fill the hole and seal the tire.
Many solutions have admittedly been devised but have not been able truly to be developed hitherto for vehicle tires, in particular because of difficulties in manufacturing these self-sealing compositions and therefore the final cost thereof.
In particular, effective self-sealing compositions, based on natural rubber and a hydrocarbon resin as tackifier, have been described in the U.S. Pat. No. 4,913,209, U.S. Pat. No. 5,085,942 and U.S. Pat. No. 5,295,525. These compositions are characterized by the combined presence of a high hydrocarbon resin content, always greater than 100 phr, and a large amount of elastomer in the liquid state, generally in the form of depolymerized natural rubber (typically with a molecular weight between 1000 and 100 000).
Firstly, such a high resin content, apart from the fact that it may be prejudicial to hysteresis and consequently to the rolling resistance of tires, requires particularly long and difficult kneading of the elastomeric matrix.
The use of a large amount of liquid elastomer admittedly improves the fluidity of the composition, but such a use is a source of other drawbacks, especially a risk of the self-sealing composition creeping during use at a relatively high temperature (typically above 60° C.), as frequently encountered when using certain tires.
If the liquid elastomer content is reduced or if it is completely omitted, another major manufacturing problem may then arise: in the absence of a filler such as carbon black, or at the very least with an appreciable amount of such as a filler (moreover not desirable, as is known, for this type of application), the composition is not very cohesive. This lack of cohesion may be such that the tack of the composition, resulting from the high content of tackifier employed, is no longer compensated for and carries it away. It then follows that there is a risk of the composition undesirably sticking on the compounding tools, which is unacceptable under industrial operating conditions.

This patent is subject to a terminal disclaimer.

Method for making a self-sealing composition

COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN


An imaging system may include first and second imaging assemblies for synchronously imaging on both sides of a receiver material using directed charged particle or aerosol toner printing methods. The imaging assemblies may in turn each include an imaging member and an intermediate transfer member, and the intermediate transfer member may be a split intermediate transfer member. The imaging system may also use flexible aperture print arrays.

Electrographic and electrophotographic processes form images on selected receivers, typically paper, using small dry colored particles called toner. The toner usually comprises a thermoplastic resin binder, dye or pigment colorants, charge control additives, cleaning aids, fuser release additives, and optionally flow control and tribocharging control surface treatment additives. The thermoplastic toner is typically attached to a print receiver by a combination of heating and pressure using a fusing subassembly that partially melts the toner into the fibers at the surface of the receiver.
Typically, in an electrographic or electrophotographic printer or copier (collectively referred to herein as "printers"), a heated fuser roller/pressure roller nip is used to attach and control the toner image to a receiver. Heat can be applied to the fusing rollers by a resistance heater, such as a halogen lamp. And, it can be applied to the inside of at least one hollow roller and/or to the surface of at least one roller. At least one of the rollers in the heated roller fusing assembly is usually compliant, and when the rollers of the heated roller fusing assembly are pressed together under pressure, the compliant roller then deflects to form a fusing nip.
Most heat transfer between the surface of the fusing roller and the toner occurs in the fusing nip. In order to minimize "offset," which generally refers to the amount of toner that adheres to the surface of the fuser roller, release oil is typically applied to the surface of the fuser roller. Release oil is generally made of silicone oil plus additives that improve the attachment of the release oil to the surface of the fuser roller and that also dissipate static charge buildup on the fuser rollers or fused prints. During imaging, some of the release oil attaches to the imaged and background areas of the fused prints.
The toner image resident on the surface of the imaging member, such as a photosensitive member or dielectric insulating member, may be transferred to a receiver material using a variety of different methods. For example, the transfer may be a direct transfer to the receiver material. Alternatively, the transfer may be an intermediate transfer in which toner is first transferred to an intermediate transfer medium and then transferred a second time in a second transfer station to the final receiver material. Other methods might also be used.
Various printers might have different printing capabilities depending on their design and their particular operational configurations. For example, different printers might have different imaging speeds. Some printers might be designed for low-capacity use and therefore might only be capable of imaging a relatively small number of pages within a given amount of time. Other printers, however, might be designed for high-capacity use and therefore might be capable of imaging a relatively large number of pages within the same amount of time.
In another example of differing print capabilities, some printers might only be capable of printing on a single side of a receiver material. Printing on a single side of a receiver medium is oftentimes referred to as simplex printing. Other printers might be capable of printing on both sides of a receiver material, which is oftentimes referred to as duplex printing. Duplex printing may be used in a variety of different applications, such as commercial printing applications and other high-volume applications. However, it might also be used in low-volume applications and non-commercial applications.
Conventional duplex imaging systems, however, may have various disadvantages. For example, many conventional duplex imaging systems require that the receiver passes through the system multiple times. U.S. Pat. No. 4,095,979 teaches transferring a first image to a first side of a copy sheet, inverting the copy sheet while the first image thereon remains unfixed, transferring the second unfixed image to the second side of the copy sheet, and then transporting the copy sheet with the first and second unfixed images to a fixing station.
U.S. Pat. Nos. 4,191,465, 4,212,529, 4,214,831, 4,447,176, 5,070,369, 5,070,371, 5,070,372, and 5,799,236 all teach the use of inverters, turn around drums, turn over stations and the like that require a receiver to make multiple passes through the system in order to image on both sides of the receiver. These systems, and others like them, require special handling of the receiver, which can reduce the speed with which the systems can perform duplex imaging.
U.S. Pat. Nos. 5,799,226, 5,826,143, 5,899,611, 5,905,931, 5,970,277, 5,930,572, 5,991,563, and 6,038,410 generally pertain to an apparatus in which a single photoconductor carrying a toner image comes into contact with a single intermediate transfer belt and transfers the image to the intermediate transfer belt at a first transfer station using a corona device. The intermediate transfer belt temporarily holds the first image and transports it in a similar fashion to permit the transfer of a second image from the photoconductor to the top-side of a receiver sheet at a first transfer station.
The belt then carries the receiver sheet with the top side image to a second transfer station at which the first image on the intermediate transfer belt is transferred to the bottom side of the receiver sheet. The receiver sheet with duplex images is then transported to a fixing station. Because the intermediate transfer belt temporarily holds the first image for a period of time representing one cycle of the intermediate transfer belt, the speed with which these systems can perform duplex imaging may also be limited. This can be disadvantageous for high-volume and high-speed imaging applications.
Directed aerosol toner development, in the general field of direct electrostatic printing, is an alternative to traditional electrophotographic systems. In directed aerosol toner development, a photoconductor is not required for image formation. Toner in the state of an airborne aerosol may be directed in an image-wise fashion to the surface of an insulating dielectric surface. Alternatively, a real image of toner particles may be written directly on a suitable recording medium. The real toner image is then formed without the need for the charging and exposure steps used in conventional electrophotographic systems.
In addition, a simpler dielectric medium can be used to receive charged particles directly comprising a latent image of charges on the surface. Charged particles include, for example, ions (e.g., cations and anions), dry toner (e.g., electrophotographic and electrographically applied powder paint) and liquid toners (e.g., aqueous, non-aqueous, organic, inorganic, and inks). These are merely examples, and other charged particles might be used.
Light is generally not required in direct electrostatic printing systems, and therefore they also generally do not require the optical sub-systems that are used in conventional electrophotographic systems. In direct electrostatic printing, an aperture array print head system can be used to directly create either a latent image of charged ions that can be subsequently developed with toner material or to directly create a real image of toner particles. Such systems are described in various U.S. patents; however, these systems are not without disadvantages.
First, the printing aperture arrays are subject to attack and damage by reactive species created from the electrical breakdown of air, which is employed in various methods used to create the charged particles. In the electrical breakdown of air associated with, for example, corona emissions, numerous reactive species may be created. These species may include ozone, oxides of nitrogen, nitric acid, reactive atomic species, reactive molecular species and reactive ionic species. These reactive species can attack and damage the print array apparatus and therefore can cause degradation in image quality or even total stoppages in printing.
A second disadvantage of direct electrostatic printing aperture arrays used for the projection of charged particles, such as toner particles, is that the apertures can become clogged with toner material. This clogging reduces the size of the aperture thereby limiting the amount of toner available at the receiver. This can then lead to degradation in image quality of the final printed image. In addition, the toner clogging can reduce the reliability and life of the aperture print array. Other disadvantages may also exist.
Therefore, there exists a need for improved systems for duplex imaging and improved systems for directed aerosol toner printing.

Synchronous duplex printing systems using directed charged particle of aerosol toner development


The present invention provides a heat-driven adsorption vacuum dehumidification system including a vapor adsorption apparatus having a water permeable hydrophilic membrane separating the apparatus into at least a feed section and a low-pressure or vacuum section (evaporator), and providing a water vapor pressure difference to extract moisture from the air flowing through the apparatus into the evaporator, followed by adsorption in an adsorption chamber, and subsequently desorbed when acted as a desorption chamber to form water vapor which is condensed in a condenser. Adsorption and desorption chambers inter-change periodically to form a complete system cycle. Heating of chamber/compartment can be from waste heat or a renewable source in the absence of any electricity supplied externally. Related method for using a heat-driven adsorption vacuum dehumidification system to remove moisture from the air is also provided. The present invention is superior to the adsorption chiller over a wide range of operating conditions.

Air-conditioning systems are used to be a major electricity consumer and carbon footprint in a modern city. With the demand for a better air ventilation in indoor environment, especially under the Covid-19 pandemic, more efforts have been made to attempt to meet the increasing energy demand by better indoor air-conditioning systems whilst reducing carbon emission from these systems.
Thermal cooling systems driven by solar energy or waste heat from a co-/tri-generation system are considered to reduce carbon emission, in particular, in modern cities of tropical/sub-tropical areas where energy demand from air-conditioning systems contribute to the majority of the total energy consumption.
Common thermal cooling systems include absorption chiller (AbC), adsorption chiller (AdC) and desiccant cooling system. In a recent study, Fong et al. (2010) compared different solar cooling systems in Hong Kong and remarked that AbC has a better coefficient of performance (COP) and therefore has a higher potential in a variety of applications in terms of its primary energy saving. However, compared to AdC, life cycle of AbC as well as that of liquid desiccant cooling systems are short and costly in maintenance; solid desiccant cooling system is usually bulkier and lower in energy efficiency as it adds heat to air stream during dehumidification. Hence, many recent studies focused on AdC, especially looking for new adsorbent.
For example, JP475122B1 disclosed a dehumidifier including a hygroscopic filter having hydrophilic inorganic materials such as zeolite, silica gels, etc., to absorb moisture in air, and the absorbed water is recovered by a means using heat to become water vapor.
U.S. Pat. No. 6,442,951B1 disclosed a dehumidifier including a moisture absorber having a desiccant for absorbing moisture from the process air. However, it also involves the use of refrigerant during the vapor compression process which is an environmental unfriendly process.
U.S. Ser. No. 10/486,102B2 disclosed a moisture removal/water harvesting material including hydrophilic micropores-containing material and a low water activity material, where the hydrophilic material can be a superhydrophilic material.
CN106705334A disclosed a fresh air handling system including an energy storage of a phase change material to store heat generated by thermoelectric cooler for regeneration of the adsorbent.
However, none of the foregoing references provide an integrated system that is absent in any environmental unfriendly refrigerant or coolant, or efficiently dehumidifies incoming air from the surroundings.
Conventional dehumidifiers are equipped with a compressor driven by electricity to dehumidify the process air by cooling and reheat the same through a vapor compression refrigerating cycle. Another emerging technology is vacuum dehumidifier which employs an electric vacuum pump to create a vacuum space to transfer moisture from process air outside the dehumidifier into the vacuum space inside the dehumidifier. Vacuum dehumidification (VD) is a mechanism of directly extracting water away from moist air stream passing through a selective medium along a water vapor pressure difference. Both are not environmental-friendly as they create a lot of carbon dioxide emission and noise.
FIG. 1 shows a design of a conventional vacuum dehumidifier, in which moist air is fed into a feed side of a hydrophilic membrane. From the feed side of the hydrophilic membrane, water vapor or permeate is transferred to permeate side of the membrane due to the water vapor pressure difference between two sides of the membrane. A vacuum pump is used to extract the water vapor from the permeate side of the membrane to the ambient while the dry air after VD leaves the feed side as a retentate. Unlike solid desiccant cooling system, VD illustrated in FIG. 1 is an isothermal dehumidification process. Energy performance of VD is better than other conventional dehumidification methods described hereinabove. Air-conditioning system incorporating VD is also considered to have a better overall energy performance by coupling with a radiant cooling system, thus reducing carbon emission.
For example, the following references which are incorporated herein by reference in their entirety provided VD driven by electrical vacuum pump:
US2020088423A1
WO2019062443A1
CN109262778A
CN107036192A
CN103282724A
CN101906800A
JPH0282034A
JPS63220026A
In addition, Qu et al. (2018) reviewed research works on membrane dehumidification including VD; Rahimi-Ahar et al. (2020) proposed VD applied in seawater desalination system; Lim et al. (2020) proposed an alternative vacuum dehumidification system to enhance energy performance and technical feasibility; Scovazzo and MacNeill (2019) provided a vacuum sweep dehumidification system developed based on a previous work (Scovazzo and Scovazzo, 2013), in which membrane tubes were employed to install across the feed flow direction with permeate being sucked into the interior of the membrane tubes for delivery to the ambient through a vacuum pump; Bukshaisha and Fronk (2019) proposed a membrane-based heat pump system using VD, vacuum evaporative cooling and pressurized humidification, in which they remarked that there was energy saving when outdoor temperature was over 21.67° C. under a wide range of weather conditions; Bui et al. (2017a) studied the thermodynamic aspect to show the performance of a VD system and proposed some new configurations to improve its COP significantly; another study by Bui et al. (2017b) proposed a model to determine performance of a VD system and also a prototype to test the system including a membrane made by themselves.
Among those VD systems equipped with electric vacuum pumps, their COP are not much better than that of AdC in a small- to medium-sized application due to their lower electrical efficiencies in such circumstance.
Therefore, there is a need for an improved heat-driven vacuum dehumidifier which utilizes thermal energy to drive the vapor adsorption cycle in order to achieve reduction in carbon dioxide emission while COP is at least comparable to that of electrical VD systems.

Heat-driven adsorption vacuum dehumidification system


A solid electrolytic capacitor (A1) includes a first and a second anode terminals (11a, 11b) projecting in different directions from each other. Preferably, a metal cover (22) for electrically connecting the anode terminals (11a, 11b) to each other is provided. With such an arrangement, the ESR and the ESL can be reduced, and the high frequency characteristics can be enhanced.

A solid electrolytic capacitor is used for canceling a noise generated from an electronic device such as a CPU, for example. Operation speed of CPUs has been improved to a large degree. With respect to a solid electrolytic capacitor, therefore, excellent noise cancellation performance for a wide frequency band including a high frequency band is demanded. A solid electrolytic capacitor is used also for assisting a power supply system for supplying power to an electronic device. In accordance with an increase in clock speed and digitalization of electronic devices, a solid electrolytic capacitor is demanded which is capable of realizing high power supply at high speed. To realize the high power supply, it is necessary that the capacitance is large and that the heat generation at the porous body is reduced.
The frequency characteristics of the impedance Z of a solid electrolytic capacitor is determined by the following formula 1.Z=√{square root over ((R2+(1/ωC−ωL)2))}  [Formula 1]
In the formula 1, ω represents angular velocity, which corresponds to 2π times the frequency. Further, C, R, and L represent the capacitance, the resistance, and the inductance of the solid electrolytic capacitor, respectively. As will be understood from the above formula, in a frequency band lower than the self-resonant frequency, 1/ωC is the major determinant of the impedance Z. Therefore, the impedance can be decreased by increasing the capacitance C. In a high frequency band near the self-resonant frequency, the resistance R is the major determinant. Therefore, to decrease the impedance, the ESR (equivalent series resistance) needs to be decreased. Further, in an ultra high frequency range higher than the self-resonant frequency, ωL is the major determinant. Therefore, to decrease the impedance, the ESL (equivalent series inductance) needs to be decreased. The larger the volume of a porous sintered body is, the higher the ESL of the solid electrolytic capacitor is. Therefore, as the capacitance is increased, decreasing of the impedance in an ultra high frequency range becomes more difficult.
For instance, a solid electrolytic capacitor includes a porous sintered body of a valve metal such as tantalum or niobium and a plurality of anode terminals projecting out from the porous sintered body. (See Patent Document 1, for example) FIGS. 23 and 24 illustrate an example of such a solid electrolytic capacitor. The solid electrolytic capacitor B includes three anode wires 92 projecting from a porous sintered body 91, and the projecting portions serve as anode terminals 93. As shown in FIG. 24, the anode terminals 93 are electrically connected to each other via an anode conduction member 94. A cathode conduction member 95 is electrically connected to a solid electrolytic layer (not shown) formed on a surface of the porous sintered body 91 via a conductive resin layer 96 made of silver paste, for example. The conduction members 94, 95 are electrically connected to an external anode terminal and an external cathode terminal (not shown) for external connection, respectively. The solid electrolytic capacitor B is structured as a so-called two-terminal solid electrolytic capacitor. In the solid electrolytic capacitor B, the ESR is decreased by the provision of the three anode terminals 93.
However, as shown in FIG. 23, the three anode wires 92 extend into the porous sintered body 91 through the same surface of the sintered body in the same direction. In this figure, the maximum of the distances between portions of the conductive resin layer 96 and the anode wires 92 is indicated as the maximum distance b. In the solid electrolytic capacitor B, the maximum distance b is the distance between an anode wire 92 and the portion of the conductive resin layer 96 located at an end of the surface which is opposite from the surface through which the anode wires 92 extend. The larger the maximum distance B is, the higher the resistance and inductance between the anode terminals 93 and the conductive resin layer 96 is. Particularly, when the size of the porous sintered body 91 is increased to increase the capacitance or the porous sintered body 91 is made flat to decrease the ESL, the maximum distance b increases. In such a case, the ESR and the ESL cannot be decreased, so that the high frequency characteristics cannot be sufficiently enhanced. Moreover, when the size of the porous sintered body is increased to realize high power supply, the heat generation at the porous sintered body 91 is increased. Therefore, the heat dissipation performance needs to be enhanced.
Patent Document 1: JP-A-2001-57319 (FIGS. 2 and 3)

Solid electrolytic capacitor with first and second anode wires


A bioaerosol detector is operated in accordance with one or more first inputs. Operating the bioaerosol detector includes filtering pathogens from the air, extracting genetic material from the filtered pathogens, and analyzing the extracted genetic material to identify the filtered pathogens. While operating the bioaerosol detector in accordance with the one or more first inputs, a change is identified in an operating condition for the bioaerosol detector. In response, the bioaerosol detector is operated in accordance with one or more second inputs. At least one input of the one or more second inputs is distinct from a respective input of the one or more first inputs.

Respiratory pathogens such as viruses and bacteria present a significant risk to public health. This risk is demonstrated by outbreaks such as the 1918 influenza pandemic, the 2016 Zika outbreak, and repeated Ebola outbreaks. The World Health Organization, in its September 2019 report "The World at Risk," warned that respiratory pathogens, such as an especially deadly strain of influenza or a disease-causing microorganism engineered or recreated in a laboratory, could spread across the world within three days, eventually killing an estimated 50-80 million people. No vaccine or treatment for a novel pathogen, whether natural or synthetic, can be approved and manufactured in three days. Furthermore, a pathogen such as the Zika virus could asymptomatically infect an entire population before being detected.
Synthetic biology, which allows viruses and other pathogens to be recreated or modified in a laboratory, presents a serious risk of misuse. In 2018, the horsepox virus, an extinct virus related to smallpox, was recreated and instructions for recreating it were published. In 2019, the Centers for Disease Control and Prevention (CDC) recreated the Ebola virus for drug testing. A different state actor or non-state actor might recreate or strengthen a pathogen with less noble intentions.
Viral detection is especially challenging. Each cubic meter of air can contain 1,000 to 100,000 (i.e., 103 to 105) contagious viruses near infected people or animals. The density of viruses in the air depends on the distance to an infected source. Sneezes and coughs by the infected source can increase the viral concentration further. The ability to scan for such viruses is desirable so that areas in which the contagion is present can be identified and avoided or quarantined. Since preventing infection is delay-sensitive, the speed of detection is an important variable. The collection of viruses in the air is RNA/DNA limited, however, so detection will not always be instantaneous. For example, detection may take tens of minutes if not hours. Furthermore, there are an estimated 106 to 107 viruses of all types per cubic meter in the near-surface atmosphere. With only 103 to 105 infectious viruses per cubic meter, signal to noise will be a fundamental tradeoff for detecting infectious viruses. And unlike bacteria, novel or emerging viruses with gene sequences that not been observed before have no conserved genomic signature: there is no localized portion of a virus's genome that can be targeted for identification without prior knowledge of the viral gene sequence. Identifying novel viruses with targeted techniques (e.g. PCR, which uses primers that are already present in the detector at the time of detection) is therefore challenging.

Dynamic modification of bioaerosol detection with genetic identification


Methods of communicating location information from a subscriber to a repeater are described. The subscriber switches from a working channel to a data revert channel, transmits a request for a periodic or one-time window to transmit an update, and determines from grant information in the response announcement the allocated window and frame before switching back to the working channel. Before the allocated time, the subscriber switches to the data revert channel, confirms whether it remains scheduled to transmit the update from a repeater announcement, and if so transmits the location update in either the current or reserved window. The announcements from the repeater contain the identity of the next window and frame and the subscriber reserved to use the window in addition to grant information. The subscribers may or may not be time-aligned and the data and data revert channels may or may not be synchronized.

Wireless communication systems contain subscribers, which may be mobile or portable radio units, and fixed infrastructure through which the subscribers communicate in a trunked mode. The infrastructure contains, for example, base stations and controllers. The subscribers are geographically distributed and generally communicate using different base stations.
Typical communications systems transmit voice, video or other data (hereinafter referred to merely as "data") messages amongst the subscribers and base stations using working channels, which are predetermined frequencies and timeslots. The working channels are random access channels and are different dependent on the message direction: an inbound (or uplink) channel is used for communications from the subscriber to the base station and an outbound (or downlink) channel is used for communications from the base station to the subscriber. When a subscriber wishes to transmit data to other subscribers, the subscriber first determines the status of the uplink channel—i.e., whether it is busy or idle. In European Telecommunications Standards Institute Digital Mobile Radio (ETSI-DMR) systems, the downlink channel periodically transmits a CACH (Common Announcement Channel) burst that indicates the status of the channel.
In many systems, the subscriber is required to monitor the uplink channel for an extended period of time prior to attempting to transmit data. Once the subscriber determines that the uplink channel is idle, the subscriber may attempt to transmit the data by first sending a request to transmit to the base station. If a large number of subscribers use the same working channel, multiple subscribers may attempt to transmit these requests at the same time, causing collisions between the requests. Base stations receiving multiple colliding messages at the same time typically do not respond to the messages as they mutually interfere with one another, causing each message to be retransmitted. Adding to this, communication systems also typically require a confirmation message be sent to the subscriber on the outbound channel to confirm receipt of the message from the subscriber. This increases the bandwidth usage on the outbound channel as well as further increasing the amount of time it takes to transmit the data from the subscriber.
These problems have become increasingly problematic due to the recent desirability of determining the location of the subscriber using the Global Positioning System (GPS) or other systems. As subscriber location information presents a heavy traffic load on a channel due to its frequent transmissions, to minimize the impact that location data might have on other data traffic, such as voice traffic, the location data can be transmitted on a separate random access channel. The throughput of this separate channel, however, is also limited by the above factors, i.e., channel access procedures (which take about 540 ms) and collision probability. Simulation in one example (in which ETSI DMR protocol using half rate FEC, transmissions are 6 bursts and radios have a 150 ms channel access collision window is used) shows that when sending location messages on the separate channel, for a target probability of success to be 93% or better (which is generally considered an acceptable level), no more than 20 updates per minute per channel should be attempted. While this is reasonable when small groups of subscribers are being tracked, it becomes exceedingly problematic if it is desired to track the locations of a large number of subscribers (e.g., greater than several hundred). This situation may occur, for example when governmental agencies (federal, state, or local) wish to track assigned communication devices in emergency service or other government vehicles. Moreover, other industries such as transportation (e.g., trucking), utilities, manufacturing, hospitality, retail, airport, construction, private security, or storage may wish to employ such tracking. In this case, however, the amount of infrastructure equipment employed to provide the tracking while providing acceptable level of success for location requests becomes large and correspondingly costly.
As it is likely that the desirability for location tracking will only increase, and therefore the number of devices being tracked correspondingly increase, it is therefore desirable to provide a method and system for location tracking using the data revert channel(s) in which number of revert channels and the amount of infrastructure employed, and thus cost, is reduced and in which the amount of time for channel access is minimized.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments shown so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Other elements, such as those known to one of skill in the art, may thus be present.

Channel structure for non-contention based windows and contention based random access requests