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31.
Tripathi Kuldeep Narayan Yadav Ashish Mohan Sharma S. C. 《Wireless Personal Communications》2022,124(3):2475-2504
Wireless Personal Communications - This work aims to implement a clustering scheme to separate vehicles into a cluster that is based on various parameters, such as the total number of relay nodes,... 相似文献
32.
Using channel state dependent packet scheduling to improve TCPthroughput over wireless LANs 总被引:1,自引:0,他引:1
Pravin Bhagwat Partha Bhattacharya Arvind Krishna Satish K. Tripathi 《Wireless Networks》1997,3(1):91-102
In recent years, a variety of mobile computers equipped with wireless communication devices have become popular. These computers
use applications and protocols, originally developed for wired desktop hosts, to communicate over wireless channels. Unlike
wired networks, packets transmitted on wireless channels are often subject to burst errors which cause back to back packet
losses. In this paper we study the effect of burst packet errors and error recovery mechanisms employed in wireless MAC protocols
on the performance of transport protocols such as TCP. Most wireless LAN link layer protocols recover from packet losses by
retransmitting lost segments. When the wireless channel is in a burst error state, most retransmission attempts fail, thereby
causing poor utilization of the wireless channel. Furthermore, in the event of multiple sessions sharing a wireless link,
FIFO packet scheduling can cause the HOL blocking effect, resulting in unfair sharing of the bandwidth. This observation leads
to a new class of packet dispatching methods which explicitly take wireless channel characteristics into consideration in
making packet dispatching decisions. We compare a variety of channel state dependent packet (CSDP) scheduling methods with
a view towards enhancing the performance of transport layer sessions. Our results indicate that by employing a CSDP scheduler
at the wireless LAN device driver level, significant improvement in channel utilization can be achieved in typical wireless
LAN configurations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
33.
Gray James P. Kshemkalyani Ajay D. Matyas Stephan M. Peyravian Mohammad Tsudik Gene 《Telecommunication Systems》1997,7(4):391-408
This paper presents a data compaction/randomization based approach as a mode of block encryption for ATM (Asynchronous Transfer
Mode) cells. The presented approach converts a plaintext into pseudo‐random plaintext before ciphering to conceal patterns
in the plaintext. The underlying idea behind this scheme is the Shannon's principles of “confusion” and “diffusion” which
involve breaking dependencies and introducing as much randomness as possible into the ciphertext. In this scheme, confusion
and diffusion are introduced into the system by first compressing the ATM cell payload and then spreading a continuously changing
random data over the entire content of the cell. As a mode of operation for block ciphering, this scheme offers the following
attractive features:(i) plaintext patterns are pseudo‐randomized and chained with ciphertext (thereby, preventing against
“dictionary”, “known plaintext”, and “statistical analysis” attacks), (ii) it is self‐synchronizing, (iii) cell loss has no
additional negative effect, (iv) no IV (Initialization Vector) storage is required, (v) it is encryption‐algorithm independent,
(vi) there is no cell‐to‐cell dependency (no feedback from previous cells), and (vii) it is highly scalable (i.e., cells from
the same stream can be ciphered and deciphered in parallel). This paper also presents a secure mechanism for in‐band synchronization
of encryption/decryption key updates using a “marker‐cell” that is carried within the data channel. An important aspect of
both the above mechanisms is that they do not require any changes to the ATM cell header or ATM infrastructure.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
34.
Nathan S. Jacobson rew J. Eckel Ajay K. Misra Donald L. Humphrey 《Journal of the American Ceramic Society》1990,73(8):2330-2332
The reactions of a sintered α-SiC with 5% H2 /H2 O/Ar at 1300°C were studied. Thermomchemical modeling indicates that three reaction regions are expected, depending on the initial water vapor or equivalently oxygen content of the gas stream. A high oxygen content ( P (O2 ) > 10−22 atm) leads to a SiO2 formation. This generally forms as a protective film and limits consumption of the SiC (passive oxidation). An intermediate oxygen content (10−22 atm > P (O2 ) > 10−26 atm) leads to SiO and CO formation. These gaseous products can lead to rapid consumption of the SiC (active oxidation). Thermogravimetric studies in this intermediate region gave reaction rates which appear to be controlled by H2 O gas-phase transport to the sample and reacted microstructures showed extensive grain-boundary attack in this region. Finally, a very low oxygen content ( P (O2 ) < 10−26 atm) is thermochemically predicted to lead to selective removal of carbon and formation of free silicon. Experimentally low weight losses and iron silicides are observed in this region. The iron silicides are attributed to reaction of free silicon and iron impurities in the system. 相似文献
35.
36.
Vivek K. Bajpai Ajay Sharma Kwang‐Hyun Baek 《International Journal of Food Science & Technology》2013,48(11):2300-2305
This study investigated the antibacterial mechanism of action of the seed essential oil of Eleutherococcus senticosus (ESEO) against foodborne pathogenic bacteria. Preliminarily, the ESEO (1000 μg disc?1) showed potential antibacterial effect as diameter of inhibition zones (12.0 ± 0.2–37.0 ± 2.0 mm) against the tested foodborne pathogens. The MIC and MBC values of ESEO against the tested bacteria were found in the range of 125–500 and 500–1000 μg mL?1, respectively. At MIC concentration, the ESEO had potential inhibitory effect on the cell viability of the tested pathogens. In addition, SEM analysis showed the inhibitory effect of ESEO as confirmed by considerable morphological alterations on the cell wall of B. cereus ATCC 13061 and E. coli O157:H7 ATCC 43889. Moreover, the ESEO revealed its mode of action against foodborne pathogens on membrane integrity as confirmed by release of extracellular ATP, 260‐nm absorbing materials and leakage of potassium ions. These findings confirm that the ESEO can be used as a potential antibacterial agent in food industry to inhibit the growth of various foodborne pathogens. 相似文献
37.
Colostrum is the initial milk secreted by bovine during parturition and the first few days after birth. Colostrum is a gift of nature used to protect the newborn's immune system and provides passive immunity against pathogens. The presence of bioactive components such as insulin-like growth factor I and II (IGF-I and IGF-II), lactoferrin, lysozyme, lactoperoxidase, and immunoglobulin make the colostrum active against pathogens such as Escherichia coli, Salmonella typhimurium, Shigella dysenteria, Listeria monocytogens, Streptococcus mutans, Bacillus stearothermophilus, and Bacillus subtilis. It is also active against Herpes simple virus type-I (HSV-I), Human Immuno-deficiency virus-I (HIV-I), and human cytomegalovirus. Lysozyme is an antibacterial and lytic enzyme; whereas lactoperoxidase is a major antibacterial found in colostrum; it is toxic to gram-positive and gram-negative bacteria. Lactoperoxidase inactivates the polio virus, vaccinia, and human immunodeficiency virus type-I in-vitro. Immunoglobulins are considered an important bioactive component in colostrum, and it contains high levels of immunoglobulin G (Ig G). Immunosupplementation with bovine milk antibodies has been shown to provide local protection to the gastrointestinal tract against disease. The restricted technical and hygienic problems, along with the unstable physio-chemical nature of colostrum, has resulted in minimal utilization of colostrum on Industrial scale. 相似文献
38.
39.
Jaya Sowjanya Siddireddy Ajay Kumar Vijay Jacqueline Tan Mark Willcox 《Contact lens & anterior eye》2018,41(2):144-153
Purpose
To investigate characteristics of the eyelid margins, meibomian glands and the tear film of contact lens wearers, and to determine whether these characteristics were related to symptoms of contact lens discomfort.Methods
A cross sectional study was performed on thirty existing daily wear soft contact lens wearers (6 male; 24 female) with median age of 23 years (range 18–41). Eyelid signs and tear film characteristics were evaluated during a single visit and subjects completed the contact lens and dry eye questionnaire (CLDEQ-8) to evaluate ocular discomfort.Results
Based on the CLDEQ-8 responses, subjects were classified as symptomatic (n?=?17) or asymptomatic (n?=?13). Grades of foam at meibomian gland orifices (3?±?1), expressibility (2?±?1) and quality of secretions (2?±?1), tear evaporation rate with (112?±?54?g/m2/h) or without (88?±?45?g/m2/h) contact lens wear, fluorescein tear breakup time (8?±?2 seconds) and tear lipid layer thickness (45?±?17?nm) were significantly associated with symptoms of discomfort in symptomatic lens wearers only (r2?>?0.45; p value?<?0.05). Upper lid-wiper epitheliopathy, meibomian gland acini reflectivity and tear meniscus height showed significant correlations with comfort scores in both symptomatic and asymptomatic contact lens wearers (p?<?0.05). A greater number of Demodex mites was also observed in the upper eyelid of symptomatic lens wearers (2?±?1) compared to asymptomatic lens wearers (0?±?0; p value?=?0.042).Conclusions
Morphological irregularities of the meibomian glands and alterations to tear film secretions that affect tear evaporative dynamics were associated with symptoms of discomfort amongst the symptomatic lens wearers. 相似文献40.