oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 127 )

2019 ( 651 )

2018 ( 752 )

2017 ( 773 )

Custom range...

Search Results: 1 - 10 of 423762 matches for " K. S. Dasgupta "
All listed articles are free for downloading (OA Articles)
Page 1 /423762
Display every page Item
Delay Resistant Transport Protocol for Deep Space Communication  [PDF]
Mohanchur Sarkar, Kaushal K. Shukla, Kankar S. Dasgupta
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2011, DOI: 10.4236/ijcns.2011.42015
Abstract: 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.
A Framework For Ubiquitous Geospatial Information Integration On Mobile Device Using Orchestration of Geoservices
Arindam Dasgupta,S. K. Ghosh
International Journal of UbiComp , 2010,
Abstract: Geospatial information is one of the essential information in our daily life for any type of decision makingespecially in emergency situation. But most of the organizations collect geospatial data for their ownpurpose in a proprietary way. The current development of geospatial information services emphasis onaccessing and sharing geospatial data from the diverse data repository. Since the amount of geospatialdata is large, distributed, and heterogeneous in nature and needs distributed computation for thegeneration of information, then it is impossible to get the required information in a single click. Theintegration these geospatial data repositories in an interoperable way and processing of thoseinformation will provide the ubiquitous access to geospatial information. The main focus of this paper isto develop a framework which could provide the user specific geospatial information at any location byprocessing of heterogeneous data from the diverse geospatial repositories. The framework utilizesgeospatial web services of open Geospatial Consortium (OGC) standards to integrate the diverse datarepositories in an interoperable manner. An orchestration engine has been adopted to incorporatebusiness logic for chaining of data and processing services to generate user specific geospatialinformation. Two case studies have been presented to realize the orchestration of geospatial webservices.
Electronic Structure and magnetism in Ir based double-perovskite Sr$_2$CeIrO$_6$
S. K. Panda,I. Dasgupta
Physics , 2013, DOI: 10.1142/S0217984913500413
Abstract: The electronic structure and magnetism of Sr$_2$CeIrO$_6$, an Ir-based double perovskite system has been investigated using first-principles calculations. We found that a strong spin-orbit coupling dictate the electronic and magnetic properties of this system. A small value of $U$ along with SOC could open up a gap at the Fermi level, offering the possibility of novel J$_{eff}$ = 1/2 Mott quantum state. Our calculations reveal that the magnetic ground state is antiferromagnetic in agreement with the magnetization data and provide the value of spin and orbital moment for this system which is in agreement with the other isostructural Ir-based compound.
Improving TCP Performance Over Wireless Network With Frequent Disconnections
Purvang Dalal,Nikhil Kothari,K. S. Dasgupta
International Journal of Computer Networks & Communications , 2011,
Abstract: Presented in this paper is the solution to the problem that arises when the TCP/IP protocol suite is usedto provide Internet connectivity through mobile terminals over emerging 802.11 wireless links. Takinginto consideration the strong drive towards wireless Internet access through mobile terminals, theproblem of frequent disconnections causing serial timeouts is examined and analyzed, with the help ofextensive simulations. After a detailed review of wireless link loss recovery mechanism and identificationof related problems, a new scheme with modifications at link layer and transport layer is proposed. Theproposed modifications which depend on interaction between two layers (i) reduce the idle time beforetransmission at TCP by preventing timeout occurrences and (ii) decouple the congestion control fromrecovery of the losses due to link failure. Results of simulation based experiments demonstrateconsiderable performance improvement with the proposed modifications over the conventional TCP,when a wireless sender is experiencing frequent link failures.
FORMAL ANALYSIS OF SECURITY POLICY IMPLEMENTATIONS IN ENTERPRISE NETWORKS
P Bera,Pallab Dasgupta,S K Ghosh
International Journal of Computer Networks & Communications , 2009,
Abstract: The management of security, operations and services in large scale enterprise networks is becomingmore difficult due to complex security policies of the organizations and also due to dynamic changes innetwork topologies. Typically, the global security policy of an enterprise network is implemented in adistributed fashion through appropriate sets of access control rules (ACL rules) across various interfaceswitches (layer 3 switches) in the network. In such networks, verification of the ACL implementationswith respect to the security policies is a major technical challenge to the network administrators. This isdifficult to achieve manually, because of the complex policy constraints (temporal access constraints)and the presence of hidden access paths in the network which may in turn violate one or more policyrules implicitly. The inconsistent hidden access paths may be formed due to transitive relationshipsbetween implemented service access paths in the network. Moreover, the complexity of the problem iscompounded due to dynamic changes in network topologies. In any point of time, the failure of thenetwork interfaces or links may change the network topology as a result alternative routing paths can beformed for forwarding various service packets. Hence, the existing security implementation (distributionof ACL rules) may not satisfy the policies. In this paper, a fault analysis module is incorporated alongwith the verification framework which as a whole can derive a correct ACL implementation with respectto a given security policy specification and can ensure that a correct security implementation is faulttolerant to certain number of link failures. The verification module can find the correct securityimplementation and the fault analysis module can find the number of link failures the existing securityimplementation can tolerate and still satisfy the security policy of the network.
Effect of Addition of Fine SiC Particles on the Dry Sliding Wear Behaviour of Extruded 2014 Al-Alloy
Rupa Dasgupta,A. K. Jha,S. Das
ISRN Tribology , 2013, DOI: 10.5402/2013/648524
Abstract: Composites of 2014 alloy made by dispersing 10 vol.% of fine (20–50?μm) SiC particles using vortex method ensuring uniform distribution of SiC particles in the matrix have shown uniform distribution of SiC particles. Mechanical properties of the composites have also registered an improvement over the alloy. In an attempt to further improve the properties, the composites were subjected to hot extrusion of cylindrical rods along with the alloys under similar experimental conditions. A temperature range of 300–350°C and an extrusion ratio of 10?:?1 were maintained during the process. The extruded samples were compared for their mechanical properties, and improvement was noted. The mechanism of material failure from fractographic studies showed difference in behaviour between the alloy and composite. Dry sliding wear studies carried out on extruded specimens exhibited improved wear behaviour in composites over alloys as measured by volume loss and wear rate. Wear mechanism was studied from the worn surface and correlated with the wear performance. It was observed that the presence of SiC particles reduces the tendency of delamination and thus material removal from the wear surface. 1. Introduction Worldwide, researchers have repeatedly demonstrated on a laboratory scale, attractive properties in aluminium-based metal matrix composites with SiC dispersoids. The property improvements relate to microstructural, mechanical properties such as specific modulus, strength, and wear resistance, in addition to a service temperature capability in selected aluminium-based composites with selected second phase dispersoids. It is an open knowledge for researchers in this field now as to the alloy systems, second phase’s nature, volume fraction, and fabrication routes that can exhibit improved performance. The properties attained are so attractive that these materials hold potential for applications in aerospace, automotive, electronic, sports, ballistic protection, and other general engineering fields [1–14]. However, the expectation to see the MMCs as engineering products would need their mass production and confidence in the ability to subject these materials to secondary processing while maintaining the improved properties attained in the cast condition. Open literature regarding mass production is seldom reported. Attempts at secondary processing of Al-based MMCs especially through extrusion to deform the materials into desired shapes and refine the microstructure are being reported substantially now [15–22]; the extruded MMCs exhibit uniform reinforced distribution,
Improving TCP Performance over Wireless Network with Frequent Disconnections
Purvang Dalal,Nikhil Kothari,K. S. Dasgupta
Computer Science , 2011,
Abstract: Presented in this paper is the solution to the problem that arises when the TCP/IP protocol suite is used to provide Internet connectivity through mobile terminals over emerging 802.11 wireless links. Taking into consideration the strong drive towards wireless Internet access through mobile terminals, the problem of frequent disconnections causing serial timeouts is examined and analyzed, with the help of extensive simulations. After a detailed review of wireless link loss recovery mechanism and identification of related problems, a new scheme with modifications at link layer and transport layer is proposed. The proposed modifications which depend on interaction between two layers (i) reduce the idle time before transmission at TCP by preventing timeout occurrences and (ii) decouple the congestion control from recovery of the losses due to link failure. Results of simulation based experiments demonstrate considerable performance improvement with the proposed modifications over the conventional TCP, when a wireless sender is experiencing frequent link failures.
Control of collar rot disease of groundnut caused by Aspergillus niger by seed soaking with non-conventional chemicals
S. DASGUPTA, S.K. RAJ and SRIKANTA DAS
Indian Phytopathology , 2012,
Abstract: Collar rot of groundnuts was controlled using seed treatment with 9 non-conventional chemicals (barium sulfate, barium nitrate, copper sulfate, copper chloride, zinc sulfate, zinc chloride, manganese sulfate, ferric chloride and mercuric chloride).
Resonant magneto-optic rotation for magnetometry using autonomous frequency stabilization
S. Pradhan,S. Mishra,R. Behera,Poornima,K. Dasgupta
Physics , 2014,
Abstract: The operation of a high sensitive atomic magnetometer using resonant elliptically polarized light is demonstrated. The experimental geometry allows autonomous frequency stabilization of the laser, thereby offers compact operation of the overall device. The magnetometry is based on measurement of the zero magnetic field resonance in degenerate two level system using polarimetric detection and has a preliminary sensitivity of <10 pT/Hz1/2 @ 1 Hz.
Weighted Transition Based Reordering, Columnwise Bit Filling, and Difference Vector: A Power-Aware Test Data Compression Method
Usha Mehta,K. S. Dasgupta,N. M. Devashrayee
VLSI Design , 2011, DOI: 10.1155/2011/756561
Abstract: Test data compression is the major issues for the external testing of IP core-based SoC. From a large pool of diverse available techniques for compression, run length-based schemes are most appropriate for IP cores. To improve the compression and to reduce the test power, the test data processing schemes like “don't care bit filling” and “reordering” which do not require any modification in internal structure and do not demand use of any test development tool can be used for SoC-containing IP cores with hidden structure. The proposed “Weighted Transition Based Reordering-Columnwise Bit Filling-Difference Vector (WTR-CBF-DV)” is a modification to earlier proposed “Hamming Distance based Reordering—Columnwise Bit Filling and Difference vector.” This new method aims not only at very high compression but also aims at shift in test power reduction without any significant on-chip area overhead. The experiment results on ISCAS89 benchmark circuits show that the test data compression ratio has significantly improved for each case. It is also noteworthy that, in most of the case, this scheme does not involve any extra silicon area overhead compared to the base code with which it used. For few cases, it requires an extra XOR gate and feedback path only. As application of this scheme increases run length of zeroes in test set, as a result, the number of transitions during scan shifting is reduced. This may lower scan power. The proposed scheme can be easily integrated into the existing industrial flow. 1. Introduction The testing cost and testing power are the two well-known issues of current generation IC testing [1]. The test cost is directly related to test data volume and hence test data transfer time [2]. Test data compression can solve the problem of test cost by reducing the test data transfer time. The dynamic test power plays a major role in overall test power. The switching activity during test has a large contribution in dynamic power and hence in overall test power. The extensive use of IP cores in SoC has further exaggerated the testing problem. Because of the hidden structure of IP cores, the SoCs containing large IP cores can use only those test data compression techniques and switching reduction technique which do not require any modification or insertion in architecture of IP core. These methods should not also demand the use of ATPG, scan insertion, or any such testing tools. They should be capable to use ready-to-use test data coming with IP core for data compression and power reduction. This test data may be partially specified or fully
Page 1 /423762
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.