An efficient and attack‐resistant key agreement scheme for secure group communications in mobile ad‐hoc networks

As a result of the growing popularity of wireless networks, in particular mobile ad hoc networks (MANET), security over such networks has become very important. Trust establishment, key management, authentication, and authorization are important areas that need to be thoroughly researched before security in MANETs becomes a reality. This work studies the problem of secure group communications (SGCs) and key management over MANETs. It identifies the key features of any SGC scheme over such networks. AUTH‐CRTDH, an efficient key agreement scheme with authentication capability for SGC over MANETs, is proposed. Compared to the existing schemes, the proposed scheme has many desirable features such as contributory and efficient computation of group key, uniform work load for all members, few rounds of rekeying, efficient support for user dynamics, key agreement without member serialization and defense against the Man‐in‐the‐Middle attack, and the Least Common Multiple (LCM) attack. These properties make the proposed scheme well suited for MANETs. The implementation results show that the proposed scheme is computationally efficient and scales well to a large number of mobile users. Copyright © 2007 John Wiley & Sons, Ltd.     

Studies on induction hardening of gray iron and ductile iron

The effect of induction case hardening of a gray cast iron (FG 260) and SG iron (600/3) as a function of applied induction power has been studied. The influence of various operating parameters on the penetration depth has been analysed. The case depth as a function of applied power and the associated changes in microstructure has been investigated. The case depth of SG iron was found to be twice than the gray iron due to higher resistivity of the material and increase in depth of penetration. Both hardness and the depth of penetration increased with increase in applied power associated with martensitic case formation. The surface hardness of both the irons varies between 600 to 800 VHN. The core microstructure in both the irons displayed pearlitic matrix. In the case of SG iron, the nodule size, sphericity and nodularity have reduced in the induction hardened case compared to the core.     

Solubility of Lanthanum in Strontium Titanate

The compound La_xSr,_1-xTiO₃ with x up to 40 at. % is observed to be homogeneous by microscopic examination. The observed X-ray powder pattern corresponds to the cubic perovskite structure. The plot of lattice constant a₀ vs x indicates a Vegard's law dependence within the experimental error. There were no extraneous lines in the X-ray powder pattern.     

Characterization of ZrO2 and SiC ceramic thin films prepared by electrostatic atomization

ZrO₂ and SiC ceramic thin films and their bilayer have been successfully prepared by a newly developed electrostatic atomization technique. This technique can generate fine spray of ceramic suspensions in a micrometer sized range with a narrow size distribution which is crucial for preparation of uniform thin films of these ceramic materials. Compared to some other thin film deposition techniques, such as Chemical vapour deposition (CVD), physical vapour deposition (PVD) and plasma spray (PS) etc. the thin film deposition process using electrostatic atomization is not only cheap but also controllable. The prepared ZrO₂ and SiC thin films were investigated using scanning electron microscopy (SEM) and energy dispersion analysis (EDA) techniques. These thin films were observed to be homogenous with a particle size less than 10 m. The ZrO₂-SiC bilayer was found to have an abrupt interface, implying that the deposition process is controllable and also that functionally graded ceramic/ceramic materials can be prepared in this way if the thickness of each layer is accurately controlled.     

Storage Decisions in Information Systems

The problem is to dynamically store different data records in different storage devices in each period so as to minimize the total expected discounted cost over a planning horizon. Each device has a fixed total capacity, each record has a given storage space requirement, while the number of requests for each record per period is changing stochastically through time. Given an allocation, the total cost per period consists of the storage cost (depending on the storage requirements and device), the access cost including update and retrieval costs (depending on the number of requests) and the transfer cost (depending upon the change of allocation from the previous period). A dynamic programming model is presented to yield optimal strategies. The special case of independent identically distributed demands is completely solved, using a generalized transportation algorithm while a heuristic procedure is indicated for the general problem using parametric analysis.     

A one-bath chrome tanning together with wet-finishing process for reduced water usage and discharge

Environmental impact has become a key issue in the present global industrial activities. A conventional leather processing method involves multi-step process that employs as well as discharges various inorganic as well as organic materials. Further, it demands huge resources like water, time and power. An attempt has been made in the study to overcome these problems by exploring a one-bath chrome tanning together with a wet-finishing process. The one-bath process provides leathers having comparable physical and bulk properties to that of conventionally processed leather. Integration of chrome tanning with post tanning improves the uptake of chromium and thereby chrome content in the leathers. The process results in moderate reductions in pollution loads, water, time and power. More specifically, water usage is reduced by 48% compared to conventional requirement.     

Electrostatic atomization of conducting liquids using ACsuperimposed on DC fields

The objective of this study is to investigate the possibility of using electrostatic atomization to produce fine ceramic particles starting from highly conducting ceramic precursor solutions. The work was directed towards carrying out experimental investigation for the production of uniform droplets formed by the breakup of a permanent jet extending from the capillary nozzle. To control the atomization process an AC field (sine wave) was superimposed on a DC field. For given parameters of electrostatic field, capillary diameters, resistivity of liquids, and flowrate, the jet formation and breakup process was investigated. Several regimes were observed to be in synchronization with the applied potentials and frequencies. In these regimes uniform droplets were produced. Optical techniques were employed to study the breakup process     

Wafer-level package interconnect options

As integrated circuit technology enters the nanometer era, global interconnects are becoming a bottleneck for overall chip performance. In this paper, we show that wafer-level package interconnects are an effective alternative to conventional on-chip global wires. These interconnects behave as LC transmission lines and can be exploited for their near speed of light transmission and low attenuation characteristics. We compare performance measures such as bandwidth, bandwidth density, latency, and power consumption of the package-level transmission lines with conventional on-chip global interconnects for different International Technology Roadmap for Semiconductors (ITRS) technology nodes. Based on these results, we show that package-level interconnects are well suited for power demanding low-latency applications. We also analyze different interconnect options such as memory buses, long inter tile interconnects, clock, and power distribution.     

Ultra-stable nanoparticles of CdSe revealed from mass spectrometry

Nanoparticles under a few nanometres in size have structures and material functions that differ from the bulk because of their distinct geometrical shapes and strong quantum confinement. These qualities could lead to unique device applications. Our mass spectral analysis of CdSe nanoparticles reveals that (CdSe)(33) and (CdSe)(34) are extremely stable: with a simple solution method, they grow in preference to any other chemical compositions to produce macroscopic quantities. First-principles calculations predict that these are puckered (CdSe)(28)-cages, with four- and six-membered rings based on the highly symmetric octahedral analogues of fullerenes, accommodating either (CdSe)(5) or (CdSe)(6) inside to form a three-dimensional network with essentially heteropolar sp(3)-bonding. This is in accordance with our X-ray and optical analyses. We have found similar mass spectra and atomic structures in CdS, CdTe, ZnS and ZnSe, demonstrating that mass-specified and macroscopically produced nanoparticles, which have been practically limited so far to elemental carbon, can now be extended to a vast variety of compound systems.     

Development of compact half-Sierpinski fractal antenna for RFID applications

A compact half-Sierpinski fractal antenna is presented for UHF RFID applications. Taking the thickness of the substrate (177 mum) and compactness (length: width <2 :1) as constraints, the fractal antenna was studied for the highest exhibited gain. A gain close to 0 dBi (-0.64 dBi) with a return loss of less than -10 dB at 915 MHz was observed.