Spectra of D-T neutrons transmitted through rare earth mixed concretes

Spectra of D-T neutrons transmitted through different densities of concrete containing rare-earth oxides are measured using a neutron generator. The NE-213 Liquid Scintillation Spectrometer is used in these measurements. The count spectra have been unfolded using the code ‘DUST’. The experimental results are compared with the one dimensional transport code ‘ASFIT’ and also the Monte-Carlo code ‘MORSE-CG’. The computations agree reasonably well with the experimental measurements. The characteristic features of the transmitted neutron spectra are explained based on the available cross-section data.     

On Group Testing Protocols for Binary-Feedback Multiaccess Channel

New group testing protocols are studied for a random multiple access, collision-type, slotted channel with binary feedback of either the success/failure or something/nothing variety. The protocols introduced here exhibit better performance than the ones suggested earlier. Implementation issues are considered.     

SAKE: Software attestation for key establishment in sensor networks

This paper presents a protocol called Software Attestation for Key Establishment (SAKE), for establishing a shared key between any two neighboring nodes of a sensor network. SAKE guarantees the secrecy and authenticity of the key that is established, without requiring any prior authentic or secret cryptographic information in either node. In other words, the attacker can read and modify the entire memory contents of both nodes before SAKE executes. Further, to the best of our knowledge, SAKE is the only protocol that can perform key re-establishment after sensor nodes are compromised, because the presence of the attacker’s code in the memory of either protocol participant does not compromise the security of SAKE. Also, the attacker can perform any active or passive attack using an arbitrary number of malicious, colluding nodes. SAKE does not require any hardware modification to the sensor nodes, human mediation, or secure side channels. However, we do assume the setting of a computationally-limited attacker that does not introduce its own computationally-powerful nodes into the sensor network.SAKE is based on Indisputable Code Execution (ICE), a primitive we introduce in previous work to dynamically establish a trusted execution environment on a remote, untrusted sensor node.     

Fabless-foundry partnership: models and analysis of coordinationissues

The fabless-foundry partnership for integrated circuit (IC) manufacturing business is expected to grow from 12% in 1995 to approximately 17% (i.e., $45B) of the total IC market in 2000. The growth of this market will be even more significant for subquarter micron technologies-whose growth is driven by the multimedia industry. The customer base will extend beyond traditional fabless IC companies into vertically integrated IC manufacturers and system vendors. Given the rate of growth and the high technology profile of products, substantial investments in capital, technology, and skilled workforce have to be dedicated and managed effectively for ensuring a successful partnership. In this paper, we outline the potential coordination problems that may arise in such partnerships, and propose a framework for analyzing issues related to yield information sharing and yield improvement. Our analysis indicates that fabless-foundry contracts that are based on a fixed number of good dies, and better yield information are more profitable     

The Effect of Trace Elements on the Cooling Curves,Microstructure and Mechanical Properties of Eutectic Aluminium-Silicon Alloy

Abstract

The effect of trace elements, used for modification, on the cooling curves obtained during solidification, microstructure and mechanical properties of eutectic aluminium-silicon alloy was investigated. The results of this study indicate the following: 1 The addition of sodium or sodium plus strontium or antimony modifies the eutectic silicon while the addition of sulphur does not alter the microstructure.

2 Those elements which modify the eutectic-silicon, lower the eutectic solidification temperature, while those elements which do not bring about modification, do not alter the eutectic solidification temperature.

3 The addition of those elements which modify the eutectic aluminium-silicon alloy, viz., sodium or sodium plus strontium or antimony improves the UTS and percentage elongation. The addition of titanium to eutectic aluminium-silicon alloy containing these trace elements improves the UTS and percentage elongation to a further extent. Among the various trace elements added to eutectic aluminium-silicon alloy, the addition of sodium plus titanium improves the UTS and percentage elongation to the maximum extent.

     

The powder metallurgy processing of refractory metals and alloys

Molybdenum and tungsten are refractory metals in the elemental form with the largest production volume in the world. The fabrication of these refractory metals, as well as their alloys and intermetallics, using high-temperature powder metallurgy (PM) is reviewed in this article. The primary focus is on the role of traditional high-temperature PM in producing alloys with tailor-made properties. An insight into the bulk production of molybdenum and tungsten alloys with nano-grains is highlighted. For more information, contact R.E. Aune, Royal Institute of Technology, Department of Materials Science and Engineering, SE-100 44 Stockholm, Sweden;+46-8-790-8363;fax+46-8-790-0939;e-mail aune@mse.kth.se.     

Thermophysical properties of silicate slags

The optimization of metallurgical processes requires reliable data of the slag phase. This paper focuses on three properties that are relevant to heat and mass-transfer calculations — viscosities,thermal diffusivities, and surface tensions of silicate melts. A brief account of the experimental techniques used for the measurements of these properties, with special reference to the work carried out in the Division of Metallurgy, Royal Institute of Technology, Stockholm, Sweden, are presented, along with the advantages and limitations. As these properties are structure-oriented, the impact of structure on these properties is also presented. The paper is intended as a state-of-the-art review of the subject.     

Subband speech coding and matched convolutional channel coding formobile radio channels

The effects of digital transmission errors on a family of variable-rate embedded subband speech coders (SBC) are analyzed in detail. It is shown that there is a difference in error sensitivity of four orders of magnitude between the most and the least sensitive bits of the speech coder. As a result, a family of rate-compatible punctured convolutional codes with flexible unequal error protection capabilities have been matched to the speech coder. These codes are optimally decoded with the Viterbi algorithm. Among the results, analysis and informal listening tests show that with a 4-level unequal error protection scheme transmission of 12 kb/s speech is possible with very little degradation in quality over a 16 kb/s channel with an average bit error rate (BER) of 2×10^-2 at a vehicle speed of 60 m.p.h. and with interleaving over two 16 ms speech frames