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Adaptive TCP: A Sender Side Mechanism with Dynamic Adjustment of Congestion Control Parameters for Performance Improvement in WLAN

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International Journal of Communications, Network and System Sciences 2015年第5期8卷 130-145页

作者： Purvang Dalal mohanchur sarkar Kankar Dasgupta Nikhil Kothari Department of Electronics and Communication D. D. University Nadiad India Space Application Center ISRO Ahmedabad India Indian Institute of Science and Technology Trivandrum India

This paper presents a sender side only TCP mechanism to prevent compromise for bandwidth utilization in IEEE 802.11 wireless networks. In absence of mechanism for accurate and immediate loss discrimination, the TCP sender unnecessarily reduces its Loss Window in response to the packet losses due to transmission errors. At the same time, frequent transmission losses and associated link retransmissions cause inaccuracy for available bandwidth estimate. The proposal, Adaptive TCP tackles the above issues using two refinements. First, sender estimates the degree of congestion by exploiting the statistics for estimated Round Trip Time (RTT). With this, it prevents unnecessary shrinkage of Loss Window and bandwidth estimate. Second, by concluding the uninterrupted evolution of its sending rate in recent past, the Adaptive TCP advances bandwidth estimate under favorable network conditions. This in turn, facilitates for quick growth in TCP’s sending rate after loss recovery and consequently alleviates bandwidth utilization. The authors implement the algorithm on top of TCP NewReno, evaluate and compare its performance with the wireless TCP variants deployed in current Internet. Through intensive simulations it is demonstrated that the Adaptive TCP outperforms other well-established TCP variants, and yields more than 100% of the throughput performance and more than 60% of improvement for bandwidth utilization, compared to TCP NewReno. The simulation results also demonstrated compatibility of Adaptive TCP in a shared wireless environment.

关键词： Bandwidth Estimation Round Trip Time Congestion Estimator Network Utilization Factor Bit Error Rate Fast Retransmit and Recovery

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Link Layer Correction Techniques and Impact on TCP’s Performance in IEEE 802.11 Wireless Networks

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Communications and Network 2014年第2期6卷 49-60页

作者： Purvang Dalal mohanchur sarkar Kankar Dasgupta Nikhil Kothari Department of Electronics and Communication Dharmsinh Desai University Nadiad India Indian Institute of Space Science and Technology Thiruvanthapuram India Indian Space Research Organization Ahmadabad India

TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary congestion control actions while attempting TCP loss recovery. Several independent link loss recovery approaches are proposed by researchers to reduce number of losses visible at TCP. In this paper we first presented a survey of loss mitigation techniques at wireless link layer. Secondly performance evaluation for TCP through Type 0 Automatic Retransmission Request mechanism in erroneous Wireless LAN is presented. In particular, simulations are performed taking into account the wireless errors introduced over IEEE 802.11 link using a well-established 2-State Markov model. TCP performance is evaluated under different settings for maximum link retransmissions allowed for each frame. Simulation results show that, link retransmission improves TCP performance by reducing losses perceived at TCP sender. However, such improvement is often associated with adverse effect on other TCP parameters that may cost a lot in return under extreme network conditions. In this paper an attempt is made to observe impact of link retransmissions on the performance of multiple TCP flows competing with each other. The analysis presented in this paper signifies the scope for maximizing TCP’s throughput at the least possible cost.

关键词： Wireless LAN Cross-Layer Scheme Medium Access Control Round Trip Time Bandwidth Estimation

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Delay Resistant Transport Protocol for Deep Space Communication

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International Journal of Communications, Network and System Sciences 2011年第2期4卷 122-132页

作者： mohanchur sarkar Kaushal K. Shukla Kankar S. Dasgupta 不详

The throughput of conventional transport protocols suffers significant degradation with the increased Round Trip Time (RTT) typically seen in deep space communication. This paper proposes a Delay Resistant Transport Protocol (DR-TCP) for point-to-point communication in deep space exploration missions. The issues related to deep space communication protocol design and the areas where modifications are necessary are investigated, and a protocol is designed that can provide good throughput to the applications using a deep space link. The proposed protocol uses a cross layer based approach to find the allocated bandwidth and avoids initial bandwidth estimation. A novel timeout algorithm estimates the timeout duration with an objective to maximize throughput and avoid spurious timeout events. The protocol is evaluated through extensive simulations in ns2 considering high RTT values typically seen in Lunar and Mars Exploration Networks under different conditions of packet error rates. DR-TCP provides a significant increase in the throughput as compared to traditional transport protocols under the same conditions. A novel adaptive redundant retransmission algorithm is also presented to take care of the high PER in deep space links. The effect of the Retransmission Frequency has been critically analyzed considering both Lunar and Deep Space scenarios under different levels of PER. The results are very encouraging even in high error conditions. The protocol exhibits a RTT independent behavior in throughput, which is the most desirable quality of a protocol for deep space communication.

关键词： Delay Resistant TCP SACK TCP Vegas Deep Space Communication Protocols RTT TP-Planet Saratoga LTP DS-TP

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Tale of mitochondria and mitochondria-associated ER membrane in patient-derived neuronal models of Wolfram syndrome

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Neural Regeneration Research 2025年第9期20卷 2587-2588页

作者： Laetitia Aubry Timothy Barrett Sovan sarkar I-STEM CECSCorbeil-EssonnesFrance UniversitéParis-Saclay Universitéd’EvryINSERMI-STEMUMR861Corbeil-EssonnesFrance Institute of Cancer and Genomic Sciences Institute of Biomedical ResearchCollege of Medical and Dental SciencesUniversity of BirminghamEdgbastonBirminghamUK Department of Endocrinology Birmingham Women’s and Children’s HospitalSteelhouse LaneBirminghamUK

Mitochondria and mitochondria-associated endoplasmic reticulum membrane in neurodegenerative diseases:Mitochondria generate most of the chemical energy needed to power the biochemical reactions of cells,and thus are often referred to as the"powerhouse"of the ***,this organelle is also involved in a pleth,ora of different cellular functions such as calcium(Ca^(2+))homeostasis,apoptosis,oxidative stress,and several metabolic pathways including oxidative phosphorylation,tricarboxylic acid cycle,andβ-oxidation of fatty acids.

关键词： oxidative cycle carboxylic

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Spatio-temporal evaluation of Zr plasma parameters in a single-beam-splitting double-pulse laser-induced plasma

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Plasma Science and Technology 2021年第2期23卷 47-56页

作者： Arnab sarkar Manjeet SINGH Fuel Chemistry Division Bhabha Atomic Research CentreMumbai 400085India Homi Bhabha National Institute AnushaktinagarMumbai 400094India

The plasma shielding effect is one of the major weaknesses of laser-induced breakdown spectroscopy(LIBS)as it causes non-linearity in signal *** LIBS is typically carried out in constant laser energy,this non-linearity causes a reduction in *** this work,we systematically examine laser-induced plasma,formed by two different excitation source modes,*** pulse(SP)-excitation and single-beam-splitting double-pulse(SBS-DP)-excitation over Zr-2.5%Nb *** two most important plasma parameters influencing the emission line intensity,plasma temperature(Te)and electron density(Ne)were studied and compared for both modes of laser *** of the results conclusively demonstrates that due to the splitting of the laser energy in the SBS-DP mode,the plasma shielding effect is significantly *** reduced plasma shielding translates to an increased laser–sample coupling under SBS-DP *** imaging of the total intensity of the laser-induced plasma in both excitation modes was also *** study shows how the plasma shielding effect can be reduced to improve the analytical quality of the LIBS methodology.

关键词： LIBS single-beam-splitting double pulse spatial-temporal evolution plasma temperature electron density

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Seismic bearing capacity of strip footing on partially saturated soil using modal response analysis

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Earthquake Engineering and Engineering Vibration 2022年第3期21卷 641-662页

作者： Abhijit Anand Rajib sarkar Department of Civil Engineering IIT(ISM)DhanbadDhanbad 826004India

The present study proposes a novel and simplified methodology to assess the seismic bearing capacity(SBC) of a shallow strip footing by incorporating strength non-linearity arising due to partial saturation of a soil matrix. Furthermore, developed methodology incorporates the modal response analysis of soil layers to assess SBC. A constant matric suction distribution profile has been considered throughout the depth of the soil. The Van Genuchten equation and corresponding fitting parameters have been considered to quantify matric suction in the analysis. SBC has been obtained for three different geomaterials;viz. sand, fly ash and clay, based on their predominant grain size and diverse soil water characteristics curve(SWCC) attributes. Variation of SBC with different modes of vibration and damping ratio are reported for ranges of matric suction pertinent to the geomaterials considered in the study. The relative significance of matric suction on SBC has been reported for suction values within the transition zone of each geomaterial. It is observed that the SBC of sand is drastically reduced, with matric suction reaching beyond the residual suction value. The SBC of fly ash remains constant beyond the residual suction value, whereas the SBC of clay shows an increasing trend toward the practical range of matric suction values.

关键词： seismic bearing capacity modal analysis matric suction

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Spectral lags of flaring events in LS I+61°303 from RXTE Observations

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Research in Astronomy and Astrophysics 2016年第7期16卷 29-38页

作者： Tamal sarkar Samir sarkar Arunava Bhadra High Energy&Cosmic Ray Research Centre University of North BengalSiliguriWB 734013India University Science Instrumentation Centre University of North BengalSiliguriWB 734013India

This work reports the first discovery of（negative） spectral lags in X-ray emission below 10 ke V from the gamma ray binary LS I＋61？303 during large flaring episodes using Rossi X-ray Timing Explorer（RXTE） observations. It is found from the RXTE data that during the flares, low energy（3–5 ke V） variations lead the higher energy（8–10 ke V） variations by a few tens of seconds whereas no significant time lag is observed during the non-flaring states. The observed spectral lag features for flaring events suggest that inverse Compton scattering may be operating, at least in some part of the system. Another possibility is that the sites of particle acceleration may be different for flaring and non-flaring events such as in the microquasar model, in which the flaring radiation may come from hot spots sitting above the black hole while steady state emissions are due to the jets.

关键词： X-rays:binaries X-rays:individual(LS I+61?303)

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Study of flow characteristics within randomly distributed submerged rigid vegetation

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Journal of Hydrodynamics 2019年第2期31卷 358-367页

作者： Paromita Chakraborty Arindam sarkar School of Civil Engineering Kalinga Institute of Industrial Technology(KIIT)Deemed to be UniversityBhubaneswarOdishaIndia School of Infrastructure Indian Institute of Technology(IIT)Bhubaneswar AurgulBhubaneswarOdishaIndia

Flow through submerged rigid vegetation has been studied both analytically and *** Reynolds stress,present in the governing equation,has been modeled using one of the turbulent stress equations,adopted in numerous *** adva ntage of this turbulent stress model is to replace the mixing length non linear term of the stress with a linear relatio n between stress and the velocity *** velocity field and shear stress are obtained by solving the governing force balance equation numerically.A correlation,validated with the experimental results,has been developed for the relevant non-dimensional numbers.

关键词： Submerged vegetation Reynolds stress drag force stream wise velocity

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Laser-induced plasma electron number density:Stark broadening method versus the Saha-Boltzmann equation

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Plasma Science and Technology 2017年第2期19卷 43-51页

作者： Arnab sarkar Manjeet SINGH Fuel Chemistry Division Bhabha Atomic Research CentreMumbai 400 085India

We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns-Nd：YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser energy and the effect of different laser wavelengths were compared. The experimentally observed line profiles of neutral aluminum have been used to extract the excitation temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadened as well as using the Saha-Boltzmann equation （SBE）. Each approach was also carried out by using the AI emission line and Mg emission lines. It was observed that the,SBE method generated a little higher electron number density value than the Stark broadening, method, but within the experimental uncertainty range. Comparisons of Ne determined by the two methods show the presence of a linear relation which is independent of laser energy or laser wavelength. These results show the applicability of the SBE method for Are determination, especially when the system does not have any pure emission lines whose electron impact factor is known, Also use of Mg lines gives superior results than Al lines.

关键词： plasma parameter laser induced plasma plasma electron density Saha-Boltzmannmethod Stark broadening method

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Time-resolved evaluation of uranium plasma in different atmospheres by laser-induced breakdown spectroscopy

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Plasma Science and Technology 2018年第12期20卷 65-74页

作者： Manjeet SINGH Arnab sarkar Fuel Chemistry Division Bhabha Atomic Research CentreMumbai 400 085India Homi Bhabha National Institute AnushaktinagarMumbai 400 094India

This work reports spectroscopic studies of uranium containing plasma generated in air and argon environments. The 532 nm Q-switched Nd：YAG laser generates the optical breakdown plasma, which was recorded by a spectrometer and an intensified charge coupled device having a resolution of 25 pm. Neutral and ionized uranium lines in the wavelength range of 385.8-391.9 nm indicate significant width and shift variations during the first few microseconds. Electron temperature and density of the plasma are determined using the Boltzmann plot and the Saha-Boltzmann equation at various time delay. The study reveals the power law decay pattern of electron temperature and density, which changes to exponential decay pattern if large gate- width is used to acquire the signal, due to an averaging effect.

关键词： uranium laser induced plasma plasma parameter temporal evaluation electron temperature electron density LIBS

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