Specifying modules to satisfy interfaces: A state transition system approach

Summary We defineinterface, module and the meaning ofM offers I, whereM denotes a module andI an interface. For a moduleM and disjoint interfacesU andL, the meaning ofM using L offers U is also defined. For a linear hierarchy of modules and interfaces,M ₁, I₁, M₂, I₂, ...,M _n, I_n, we present the following composition theorem: IfM ₁ offersI ₁ and, fori=2, ...,n, M _i usingI _i–1 offersI _i, then the hierarchy of modules offersI _n.Our theory is applied to solve a problem posed by Leslie Lamport at the 1987 Lake Arrowhead Workshop. We first present a formal specification of a serializable database interface. We then provide specifications of two modules, one based upon two-phase locking and the other multi-version timestamps; the two-phase locking module uses an interface offered by a physical database. We prove that each module offers the serializable interface. Simon S. Lam is Chairman of the Department of Computer Sciences at the University of Texas at Austin and holds and endowed professorship. His research interests are in the areas of computer networks, communication protocols, performance models, formal methods, and network security. He serves on the editorial boards ofIEEE Transactions on Software Engineering andPerformance Evaluation. He is an IEEE Fellow, and was a corecipient of the 1975 Leonard G. Abraham Prize Paper Award from the IEEE Communications Society. He organized and was program chairman of the first ACM SIGCOMM Symposium on Communications Architectures and Protocols in 1983. He received the BSEE degree (with Distinction) from Washington State University in 1969, and the MS and Ph.D. degrees from the University of California at Los Angeles in 1970 and 1974 respectively. Prior to joining the University of Texas faculty, he was with the IBM T.J. Watson Research Center from 1974 to 1977. A. Udaya Shankar received the B. Tech. degree in Electrical Engineering from the Indian Institute of Technology, Kanpur, in 1976, the M.S. degree in Computer Engineering from Syracuse University, Syracuse, NY, in 1978, and the Ph.D. degree in Electrical Engineering from the University of Texas at Austin, in 1982. Since January 1983, he has been with the University of Maryland, College Park, where he is now an Associate Professor of Computer Science. Since September 1985, he has been with the Institute for Advanced Computer Studies at the University of Maryland. His current research interests include the modeling and analysis of distributed systems and network protocols, from both correctness and performance aspects. He is a member of IEEE and ACM.The work of Simon S. Lam was supported by National Science Foundation grants no. NCR-8613338 and no. NCR-9004464. The work of A. Udaya Shankar was supported by National Science Foundation grants no. ECS-8502113 and no. NCR-8904590     

Rover: scalable location-aware computing

All the components necessary for realizing location-aware computing are available in the marketplace today. What has hindered the widespread deployment of location-based systems is the lack of an integration architecture that scales with user populations. The authors have completed the initial implementation of Rover, a system designed to achieve this sort of integration and to automatically tailor information and services to a mobile user's location. Their studies have validated Rover's underlying software architecture, which achieves system scalability through high-resolution, application-specific resource scheduling at the servers and network. The authors believe that this technology will greatly enhance the user experience in many places, including museums, amusement and theme parks, shopping malls, game fields, offices, and business centers. They designed the system specifically to scale to large user populations and expect its benefits to increase with them.     

A Centralized Mechanism for Preventing DDOS Attack in Wireless Sensor Networks

Wireless sensor networks face numerous limitations. Security and Privacy are the two most essential parameters that require consideration in wireless sensor networks for conveying responsive information amid basic applications. High density and limited communication range of sensor nodes, forwarding packets in sensor networks have caused the performance of during multi-hop data transmission. Hence communication with different devices these days are not secure, due to the absence of centralized monitoring and overprotective requirements. This paper is related to speak about Distributed Denial of Service which debilitates the ability of the network and the data being transmitted. The earlier system guarantees the WSN through a self arranged and confined procedure between the nodes in the sensor environment. Here, the authors present the Centralized Detect Eliminate and Control algorithm for authorization and centralized monitoring component to discover the node that has turned into a victim node and to get rid of the information communicated to the fatality node from the neighbour nodes. Overprotective of the communication between the nodes leads to dependability. The simulation results improve the malicious node detection rate and increase the various parameters like throughput and reduce the average delay. This leads to, the overall detection rate built, eventually enhancing the parameters of the network environment.

     

Comparison of AMSR‐E and TMI sea surface temperature with Argo near‐surface temperature over the Indian Ocean

Sea surface temperature (SST) measurements from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) are compared with near‐surface temperature (foundation SST) in situ measurements obtained from Argo floats over the Indian Ocean. Spatial variation was compared for 2002–2006 and 11 floats were used for temporal variation collocated observations. The results show that TMI and AMSR‐E SST measurements are slightly overestimated during the pre‐ and post‐monsoon seasons and underestimated during the monsoon season. Statistical analysis shows that the SST from the AMSR‐E is better correlated with the Argo foundation SST compared to the TMI. The standard deviation (SD) and root mean square error (RMSE) for AMSR‐E SST are 0.58°C and 0.35°C, respectively, over the Equatorial Indian Ocean (EIO). The corresponding values for the TMI are 0.66°C and 0.47°C. Over the Arabian Sea the SD values are slightly higher compared to the EIO values, whereas RMSE values are less for both TMI and AMSR‐E SST. These retrieval accuracies are above the expected retrieval accuracy. The seasonal average spatial distribution of AMSR‐E SST shows a better match with the Argo foundation SST compared to TMI SST distributions. The robustness of the good spatial match during the monsoon season may be attributed to strong winds.     

Antivirus security: naked during updates

The security of modern computer systems heavily depends on security tools, especially on antivirus software solutions. In the anti‐malware research community, development of techniques for evading detection by antivirus software is an active research area. This has led to malware that can bypass or subvert antivirus software. The common strategies deployed include the use of obfuscated code and staged malware whose first instance (usually installer such as dropper and downloader) is not detected by the antivirus software. Increasingly, most of the modern malware are staged ones in order for them to be not detected by antivirus solutions at the early stage of intrusion. The installers then determine the method for further intrusion including antivirus bypassing techniques. Some malware target boot and/or shutdown time when antivirus software may be inactive so that they can perform their malicious activities. However, there can be another time frame where antivirus solutions may be inactive, namely, during the time of update. All antivirus software share a unique characteristic that they must be updated at a very high frequency to provide up‐to‐date protection of their system. In this paper, we suggest a novel attack vector that targets antivirus updates and show practical examples of how a system and antivirus software itself can be compromised during the update of antivirus software. Local privilege escalation using this vulnerability is also described. We have investigated this design vulnerability with several of the major antivirus software products such as Avira, AVG, McAfee, Microsoft, and Symantec and found that they are vulnerable to this new attack vector. The paper also discusses possible solutions that can be used to mitigate the attack in the existing versions of the antivirus software as well as in the future ones. Copyright © 2013 John Wiley & Sons, Ltd.     

Sorption,diffusion, and pervaporation separation of water–acetic acid mixtures through the blend membranes of sodium alginate and guar gum‐grafted‐polyacrylamide

Nonporous homogeneous dense membranes were prepared from the blends of sodium alginate (Na–Alg) with guar gum‐grafted polyacrylamide (GG‐g‐PAAm) in the ratios of 3 : 1 and 1 : 1 and these were tested for the pervaporation separation of water–acetic acid mixtures at 30°C. Blend compatibility was studied in solution by measuring the viscosity and the speed of sound. Membranes were crosslinked by glutaraldehyde. The GG‐g‐PAAm polymer and the crosslinked blend membranes were characterized by Fourier transform infrared spectra. High separation selectivity was exhibited by the pure Na–Alg membrane for water–acetic acid (HAc) mixtures containing 20 mass % of water. The permeation flux increased with increasing mass percent of water in the feed as well as with an increase in the amount of GG‐g‐PAAm in the blend, but separation selectivity decreased. Sorption selectivity was higher for the Na–Alg membrane than for the blend membranes, but it decreased with increasing mass percent of GG‐g‐PAAm in the blends. Diffusion selectivity values vary systematically with the blend composition, but not with the amount of water in the feed. Diffusion coefficients of the water–HAc mixtures were calculated from Fick's equation using sorption data and compared with those calculated from flux values obtained in pervaporation experiments. The Arrhenius activation parameters were calculated for the 20 mass % of water in the feed using flux and diffusion data obtained at 30, 40, and 50°C. The diffusion and pervaporation results are explained in terms of solution–diffusion concepts. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 259–272, 2002     

Ultrasonically induced in situ polymerization of PANI-SWCNT nanocomposites for electromagnetic shielding applications

Journal of Materials Science: Materials in Electronics - Electromagnetic interference (EMI) shielding has potential importance due to rapid growth in electronic technology. In recent days, carbon...     

Concentration of ω-3 polyunsaturated fatty acids of marine oils using Candida cylindracea lipase: Optimization of reaction conditions

Production of ω-3 fatty acid concentrates from seal blubber oil (SBO) and menhaden oil (MHO) upon enzymatic hydrolysis by Candida cylindracea lipase was optimized. In this process, the content of total ω-3 fatty acids, Y ₁; eicosapentaenoic acid, Y ₂; and docosahexaenoic acid, Y ₃, in the final product was maximized. A three-factor central composite rotatable design was used to study the effect of enzyme concentration (X ₁), reaction time (X ₂), and reaction temperature (X ₃). Second-order polynomial regression models for Y ₁, Y ₂, and Y ₃ were employed to generate response surfaces. After hydrolysis, a maximum of 54.3% total ω-3 fatty acids was obtained from SBO at an enzyme concentration of 308 U/g oil, a reaction time of 40 h, and a reaction temperature of 37°C. Similarly, a maximum of 54.5% total ω-3 fatty acids was obtained from MHO at an enzyme concentration of 340 U/g oil, a reaction time of 45 h, and a reaction temperature of 38°C.     

Simulation Studies of A 76MM Hydrocyclone

The investigation pertains to establishing a simulation methodology for understanding the separation characteristics of a typical hydrocyclone where the work was carried out using a commercially available CFD software. The studies included water flow profiles, water throughput {\&} product split, particle distribution etc. and the simulated results are further validated with suitably performed experiments. The work essentially highlights the performance of the hydrocyclone using numerical studies where water is used as a primary phase and solid particles as secondary ones. This methodology is expected to be useful in the design of hydrocyclones and optimizing the processes.     

Cyclic codes and self-dual codes over F2+uF2

We introduce linear cyclic codes over the ring F₂+uF ₂={0,1,u,u¯=u+1}, where u²=0 and study them by analogy with the Z₄ case. We give the structure of these codes on this new alphabet. Self-dual codes of odd length exist as in the case of Z₄-codes. Unlike the Z₄ case, here free codes are not interesting. Some nonfree codes give rise to optimal binary linear codes and extremal self-dual codes through a linear Gray map