An Efficient and Scalable Quasi-Aggregate Signature Scheme Based on LFSR Sequences

Aggregate signatures can be a crucial building block for providing scalable authentication of a large number of users in several applications like building efficient certificate chains, authenticating distributed content management systems, and securing path vector routing protocols. Aggregate signatures aim to prevent resources (signature and storage elements, and computation) from growing linearly in the number of signers participating in a network protocol. In this paper, we present an efficient and scalable quasi-aggregate signature scheme, {rm CLFSR}- {rm QA}, based on third-order linear feedback shift register (cubic LFSR) sequences that can be instantiated using both XTR and GH public key cryptosystems. In the proposed {rm CLFSR}-{rm QA} construction, signers sign messages sequentially; however, the verfier need not know the order in which messages were signed. The proposed scheme offers constant length signatures, fast signing, aggregation, and verification operations at each node, and requires the least storage elements (public keys needed to verify the signature), compared to any other aggregate signature scheme. To the best of our knowledge, {rm CLFSR}- {rm QA} is the first aggregate signature scheme to be constructed using LFSR sequences. We believe that the {rm CLFSR}- {rm QA} signature scheme can be catalytic in improving the processing latency as well as reducing space requirements in building secure, large-scale distributed network protocols. We perform extensive theoretical analysis including correctness and security of {rm CLFSR}- {rm QA} and also present a performance (computation and communication costs, storage overhead) comparison of the proposed scheme with well-known traditional constructions.     

Standardization of work-a statistical approach using spreadsheet

One of the techniques of work study is work measurement employed to ensure the best possible use of human in carrying out a specific activity. Using appropriate measurement procedures, a work standard can be set which will reflect the gross time required by a normal operator working under normal conditions and with normal pace to complete a unit of work satisfactorily. One of the approaches in setting the work standard is based on the statistical analysis of time data. This paper presents a method of establishing work standard by generating statistical control chart using Excell -- an integrated spreadsheet and graphics software for the Apple-Macintosh.     

Simple narrow-linewidth 1.5 ?m InGaAsP DFB external-cavity laser

An external-cavity laser consisting of a 1.5 ?m-wavelength antireflection-coated DFB laser chip, a microscope objective and a mirror provides a stable, single-frequency, narrow-linewidth (?f=40 kHz) output. Because the laser operates in the strong feedback regime, it is immune to external optical perturbations. Single-longitudinal-mode operation is maintained by the DFB grating, and the linewidth is reduced by the extended passive cavity.     

Scientific output of small and medium size firms in high techindustries

The author focuses on the scientific output of small and medium-sized firms in high-tech industries in the US. The indicators for technological output have been defined differently by different researchers. Economists have used patents as the measure of research and development (R&D) output, partly because they are easier to delineate than other indicators. Behavioral researchers interested in the R&D management process have relied on publications as a surrogate measure for R&D output, while research in science policy and innovation has focused on products and processes as indicators of innovation and technical output. The author focuses on all three measures as indicators of R&D output and investigates the interrelationship among them as well as the correlates for this output. Except for the chemical industry. R&D expenditure is closely related to size as measured by annual sales, rather than the net income. It is observed that a growing firm is more likely to spend proportionately more money in R&D. The three output measures-patents, papers, and new products-are correlated, but the pattern of the relationship is different in different industries. It is noted that a firm's grown is linked with new products in only some industries. Patents do not seem to have any effect on sales growth. The growth in R&D is not a factor leading to a higher level of scientific productivity. The important factor is the average level of R&D spending. The policy implication for this observation is to maintain a steady funding level of R&D, avoiding sudden changes in R&D budget     

New Insights into the Appraisal of Flood-Alleviation Benefits: (1) Flood Damage and Flood Loss Information

New approaches to the appraisal of flood-alleviation investment have been developed over the last twenty-five years. This has led to (a) increased precision in benefit-cost analysis, as better data have become available, and (b) a more rational approach to decision making as the UK Government has clarified and enhanced the decision criteria. This paper presents a detailed account of some of these developments, with an emphasis on the data on flood damages and losses avoided by flood-alleviation schemes, and draws out lessons for those involved in this form of investment appraisal.     

Comparative study of electron conduction in azulene and naphthalene

We have studied the feasibility of electron conduction in azulene molecule and compared with that in its isomer naphthalene. We have used non-equilibrium Green’s function formalism to measure the current in our systems as a response of the external electric field. Parallely we have performed the Gaussian calculations with electric field in the same bias window to observe the impact of external bias on the wave functions of the systems. We have found that the conduction of azulene is higher than that of naphthalene inspite of its intrinsic donor-acceptor property, which leads a system to more insulating state. Due to stabilization through charge transfer the azulene system can be fabricated as a very effective molecular wire. Our calculations show the possibility of huge device application of azulene in nano-scale instruments.     

Applications of Anaerobic Digestion for the Treatment of Industrial Wastewaters in Europe

For many decades, anaerobic digestion has been the most important technique of sewage sludge treatment at larger sewage-treatment works. Also, the low running costs of the process make it attractive for the treatment of strong industrial effluents. This paper reviews these advantages and discusses some disadvantages of the anaerobic treatment of industrial effluent. Operating and cost data are presented from Europe and from a detailed UK case study which supports the conclusion that anaerobic treatment will be the most cost-effective method of treatment of strong industrial effluents such as those from food and paper processing.     

Optimum Design of Sewage Sludge Consolidation Tanks

Consolidation is potentially the most cost-effective of all sludge treatment processes. However, traditional design procedures have been oversimplified such that the process has not generally been fully exploited.
The objective of this report is to summarize the Water Research Centre (WRc) procedure for sizing sewage sludge consolidation tanks, and explain the major design aspects which control the effective operation of the plant. The procedure provides a means of sizing tanks to consolidate any particular sewage sludge to any solids concentrations up to the maximum, and is applicable to both the batch and continuous operational modes. To obtain the predicted performance, the essential equipment such as the picket fence and control system, comprising a consolidation plant, must be suitably designed.     

Diffraction by a dielectric half-plane

The problem of diffraction of a plane electromagnetic wave by a dielectric half-plane is reconsidered for solution by utilizing a set of recently developed approximate boundary conditions and the Wiener-Hopf technique. It is observed from the present solution of the problem that reflected waves cease to exist if the angle of incidence takes up the valuetan^{-1}(1/n)wherenrepresents the refractive index of the material of the half-plane under consideration. Expression for the diffracted far field is obtained by using a modification of the saddle point method, and numerical values of the diffraction coefficients are presented in the form of a table for a special value of the refractive indexnand for different values of the parameterkh, hrepresenting the (small) thickness of the half-plane andkthe wavenumber.     

The Use of Different Conveyance Calculations for Modelling Flows in a Compact Compound Channel

Flow measurements have been taken for steady and unsteady flows on a reach of a river having a compact compound channel. The 'single channel', 'divided channel' and 'lateral' distribution methods have been used to calculate conveyances for use in a one-dimensional unsteady flow model of the reach. Comparisons with measured flows show that the divided channel method and the lateral distribution method both underestimate floodplain flow depths. The lateral distribution method gives the closest accuracy in the relative depth range 0.15 ≤ Yr < 0.40. For large flow depths the single channel method becomes more accurate and slightly over-estimates flow depths.
The accuracy of unit width discharge distributions, calculated from the lateral distribution method are assessed by comparison with observed distributions for overbank flows.