Showing papers by "Delhi Technological University published in 2008"

Elliptic curve cryptography

Abstract: This paper describes the Elliptic Curve Cryptography algorithm and its suitability for smart cards.

Strategy development by SMEs for competitiveness: a review

Abstract: Purpose – SMEs are considered as engine for economic growth all over the world. After the globalization of market, SMEs have got many opportunities to work in integration with large‐scale organizations. They cannot exploit these opportunities and sustain their competitiveness if they focus only on certain aspects of their functioning and work in isolation. This paper tries to identify the major areas of strategy development by SMEs for improving competitiveness of SMEs in globalised market.Design/methodology/approach – About 134 research papers, mainly from referred international journals are reviewed to identify thrust areas of research. On the basis of review, gaps are identified and research agenda is proposed.Findings – SMEs have not given due attention for developing their effective strategies in the past. They are localized in functioning. On export fronts SMEs face many constraints due to lack of resources and poor innovative capabilities. For sustaining their competitiveness, they have to benchmar...

Theoretical analysis of a vapour compression refrigeration system with R502, R404A and R507A

Abstract: This paper presents a detailed exergy analysis of an actual vapour compression refrigeration (VCR) cycle. A computational model has been developed for computing coefficient of performance (COP), exergy destruction, exergetic efficiency and efficiency defects for R502, R404A and R507A. The present investigation has been done for evaporator and condenser temperatures in the range of −50 °C to 0 °C and 40 °C to 55 °C, respectively. The results indicate that R507A is a better substitute to R502 than R404A. The efficiency defect in condenser is highest, and lowest in liquid vapour heat exchanger for the refrigerants considered.

Selective Compensation of Power-Quality Problems Through Active Power Filter by Current Decomposition

Abstract: Active power filters (APFs) are used to compensate harmonics, reactive current and negative sequence fundamental frequency current of load current drawn by nonlinear loads. The flexibility of selective compensation, if provided in the control scheme, makes APF versatile device for compensation of reactive power, harmonic currents and unbalance in source currents and their combinations, depending upon the limited rating of the voltage-source inverter employed as an APF. The proposed scheme decomposes the load current into positive and negative sequence fundamental frequency active components, reactive component and harmonic components in synchronous reference frames. The control scheme performs with priority-based scheme, which respects the limited rating of the APF. The simulated results in MATLAB environment and experimental results of the developed prototype of APF are presented to validate the effectiveness of the proposed control scheme. Digital signal processor based implementation of control scheme is also detailed for selective compensation of power-quality problems with details of developed prototype.

Enzymatic Hydrolysis and Ethanol Fermentation of High Dry Matter Wet-Exploded Wheat Straw at Low Enzyme Loading

Abstract: Wheat straw was pretreated by wet explosion using three different oxidizing agents (H2O2, O2, and air). The effect of the pretreatment was evaluated based on glucose and xylose liberated during enzymatic hydrolysis. The results showed that pretreatment with the use of O2 as oxidizing agent was the most efficient in enhancing overall convertibility of the raw material to sugars and minimizing generation of furfural as a by-product. For scale-up of the process, high dry matter (DM) concentrations of 15–20% will be necessary. However, high DM hydrolysis and fermentation are limited by high viscosity of the material, higher inhibition of the enzymes, and fermenting microorganism. The wet-explosion pretreatment method enabled relatively high yields from both enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) to be obtained when performed on unwashed slurry with 14% DM and a low enzyme loading of 10 FPU/g cellulose in an industrial acceptable time frame of 96 h. Cellulose and hemicellulose conversion from enzymatic hydrolysis were 70 and 68%, respectively, and an overall ethanol yield from SSF was 68%.

Comparing the performance of cereal varieties in organic and non-organic cropping systems in different European countries

Abstract: Top ranking varieties are tested in multiple environments before and after registration in order to assess their value for cultivation and use (VCU testing). Recently, interest has increased in obtaining varieties specifically adapted to organic farming conditions. This raised the question if an independent system of trials may be required for this purpose. To help answering this question, through the exchange network of European cereal researchers SUSVAR (www.cost860.dk), a number of data sets of agronomic traits from barley, wheat and winter triticale, from trials performed in Denmark, Sweden, The Netherlands, France, Switzerland, UK and Germany, were made available and analysed using an approach based on mixed models involving parameters describing genetic correlation between the two types of experiments, i.e., organic and non-organic (high or low input). Estimated variance components and correlations were used to evaluate response to selection and index selection. The response to index selection was analysed as a function of the fraction of available trials assigned to the organic system. The genetic correlations were interpreted in terms of ranking agreement. We found high genetic correlations between both systems for most traits in all countries. Despite high genetic correlations, the chances of very good agreement in observed rankings were moderate. Combining information from both organic and non-organic systems is shown to be beneficial. Further, ignoring information from non-organic trials when making decisions regarding performance under organic conditions is a sub-optimal strategy.

Potentiometric urea biosensor based on BSA embedded surface modified polypyrrole film

Abstract: A potentiometric biosensor based on bovine serum albumin (BSA) embedded surface modified polypyrrole has been developed for the quantitative estimation of urea in aqueous solution. The enzyme, urease (Urs), was covalently linked to free amino groups present over the BSA embedded modified surface of the conducting polypyrrole film electrochemically deposited onto an indium–tin-oxide (ITO) coated glass plate. The biosensor has been characterized by UV–visible, infrared spectroscopy and SEM. Potentiometric and spectrophotometric response of the enzyme electrode (Urs/BSA-PPy/ITO) were measured as a function of urea concentration in Tris–HCl buffer (pH 7.0). It has been found that the electrode responds to low urea concentration with wider range of detection. The electrode showed a linear response range of 6.6 × 10−6 to 7.5 × 10−4 M urea. The response time is about 70–90 s reaching to a 95% steady-state potential value and 75% of the enzyme activity is retained for about 2 months. These results indicate an efficient covalent linkage of enzyme to free amino groups of the BSA molecules over the surface of polypyrrole film, which leads to high enzyme loading, an increased lifetime stability of the electrode and an improved wide range of detection of low urea concentration in aqueous solution.

Bianchi type-V perfect fluid space-time models in general relativity

Abstract: The law of variation for the generalized mean Hubble’s parameter in the case of a spatially homogeneous and anisotropic Bianchi type-V space-time metric that yields a constant value of deceleration parameter, is presented The variation for Hubble’s parameter generates two types of solutions for the average scale factor one is of power-law type and second is of the exponential form Using these two forms, Einstein’s field equations for perfect fluid Bianchi type-V models are solved separately that correspond to singular and non-singular models respectively We find that the constant value of deceleration parameter is reasonable for description of the present day universe We also find that the universe decelerates for positive value of deceleration parameter where as it accelerates for negative one The behaviors of observationally important parameters such as expansion scalar, mean anisotropic parameter and shear scalar are discussed Exact expressions for look-back time, luminosity distance and event horizon versus redshift are derived and their significances are discussed in detail It has been observed that the solutions are compatible with the results of recent observations

An Indirect UPFC Model to Enhance Reusability of Newton Power-Flow Codes

Abstract: Power-flow modeling of a unified power-flow controller (UPFC) increases the complexities of the computer program codes for a Newton-Raphson load-flow (NRLF) analysis. This is due to the fact that modifications of the existing codes are needed for computing power injections, and the elements of the Jacobian matrix to take into account the contributions of the series and shunt voltage sources of the UPFC. Additionally, new codes for computing the UPFC real-power injection terms as well as the associated Jacobian matrix need to be developed. To reduce this complexity of programming codes, in this paper, an indirect yet exact UPFC model is proposed. In the proposed model, an existing power system installed with UPFC is transformed into an augmented equivalent network without any UPFC. Due to the absence of any UPFC, the augmented network can easily be solved by reusing the existing NRLF computer codes to obtain the solution of the original network containing UPFC(s). As a result, substantial reduction in the complexities of the computer program codes takes place. Additionally, the proposed model can also account for various practical device limit constraints of the UPFC.

Bulk viscous cosmology in early Universe

Abstract: The effect of bulk viscosity on the early evolution of Universe for a spatially homogeneous and isotropic Robertson-Walker model is considered. Einstein’s field equations are solved by using ‘gamma-law’ equation of state p = (γ − 1)ρ, where the adiabatic parameter gamma (γ) depends on the scale factor of the model. The ‘gamma’ function is defined in such a way that it describes a unified solution of early evolution of the Universe for inflationary and radiation-dominated phases. The fluid has only bulk viscous term and the coefficient of bulk viscosity is taken to be proportional to some power function of the energy density. The complete general solutions have been given through three cases. For flat space, power-law as well as exponential solutions are found. The problem of how the introduction of viscosity affects the appearance of singularity, is briefly discussed in particular solutions. The deceleration parameter has a freedom to vary with the scale factor of the model, which describes the accelerating expansion of the Universe.

Exact Bianchi Type-I Cosmological Models in a Scalar-Tensor Theory

Abstract: In this paper, a spatially homogeneous and anisotropic Bianchi type-I space-time filled with perfect fluid is investigated within the framework of a scalar-tensor theory proposed by Saez and Ballester. Two different physically viable models of the universe are obtained by using a special law of variation for Hubble’s parameter that yields a constant value of deceleration parameter. One of the models is found to generalize a model recently investigated by Reddy et al. (Astrophys. Space Sci. 306:171, 2006). The Einstein’s field equations are solved exactly and the solutions are found to be consistent with the recent observations of type Ia supernovae. A detailed study of physical and kinematical properties of the models is carried out.

Competency and performance analysis of Indian SMEs and large organizations: An exploratory study

Abstract: Purpose – Globalization of markets and increasing expectations of customers have created a turbulent environment for Indian organizations. The purpose of this paper is to study the development of various competencies by small‐, medium‐ and large‐scale Indian organizations under various pressures and constraints.Design/methodology/approach – For collecting data, a questionnaire‐based survey were conducted. Out of 241 responding organizations, 193 were small‐ to medium‐sized enterprises (SMEs) and 48 were larger organizations. Statistical analysis of data acquired from the survey are done by reliability test, t‐test and correlation analysis.Findings – Introduction of new technology and identification of market changes have emerged as most important competencies because they are significantly correlated with subjective performance, objective performance and overall competitiveness of organization. Levels of focus given on competencies development by large organizations differ significantly from SMEs.Research...

An Exact Bianchi Type-I Cosmological Model in Lyra's Manifold

Abstract: A spatially homogeneous and anisotropic Bianchi type-I space–time has been studied within the framework of Lyra's geometry. Exact solutions of the Einstein's field equations have been obtained with a time dependent gauge function by using a special law of variation for Hubble's parameter that yields a constant value of deceleration parameter. It has been found that the solutions generalize the solutions obtained by Rahaman et al. [Astrophys. Space Sci.299, 211 (2005)] and are consistent with the recent observations of type Ia supernovae. A detailed study of physical and kinematical properties of the model has been carried out.

Preparation and Characterization of Potato Starch Based Low Density Polyethylene/Low Density Polyethylene Grafted Maleic Anhydride Biodegradable Polymer Composite

Abstract: Polysaccharide-filled plastics have attracted immense interest from research scientists as a means to develop a biodisintegrable polymer. The objective of the present study is to develop a biodisin...

Knowledge-based image retrieval system

Abstract: Most of the retrieval systems concentrate much on low-level features such as color, texture, shape and position. The present system is mainly developed based on the visual descriptors of the image such as color, texture and shape descriptors, etc. along with the high-level semantic analysis of the image content through different processing modules in the proposed architecture. Similarity measures are proposed and the performance evaluation has been done. As an image browser, apart from retrieving images by image example, it also supports query by natural language. The present system works well both online and offline.We have used unsupervised Kohonen's self-organizing maps (SOM) technique to train the images and our own indexing scheme with reference system based on R-tree SOM. We proposed an approach fuzzy color histogram for color retrieval, and Lie descriptors for the retrieval of shapes. We have also tested our appraoch for MPEG-7 images.

Bianchi type v cosmological models with perfect fluid and heat conduction in lyra's geometry

Abstract: The field equations within the framework of Lyra's geometry with a time-dependent displacement vector field for a Bianchi type-V space–time filled with a perfect fluid and heat flow are presented. Two different classes of physically viable solutions are obtained by using a special law of variation for the generalized mean Hubble's parameter which correspond to singular and nonsingular models with constant deceleration parameter. These models are found to be consistent with the observations on the present day universe. Some thermodynamical relations are studied. The physical and kinematical behaviors of the models are also discussed.

Some Exact Bianchi Type V Perfect Fluid Solutions with Heat Flow

Abstract: The variation law for generalized mean Hubble’s parameter is discussed in a spatially homogeneous and anisotropic Bianchi type V space-time with perfect fluid along with heat-conduction. The variation law for Hubble’s parameter, that yields a constant value of deceleration parameter, generates two types of solutions for the average scale factor, one is of power-law type and other one of exponential form. Using these two forms of the average scale factor, exact solutions of Einstein field equations with a perfect fluid and heat conduction are presented for a Bianchi type V space-time, which represent expanding singular and non-singular cosmological models. We find that the constant value of deceleration parameter is reasonable for the present day universe. The physical and geometrical properties of the models are also discussed in detail.

Corrosion Reliability of Electronic Systems

Abstract: Inherently two factors namely multi-material usage and potential bias makes electronic devices susceptible to corrosion if exposed to humid conditions. The problem is compounded today due to miniaturization and contamination effects. The reduction in size of the components and close spacing on a Printed Circuit Board (PCB) for high density packing has greatly increased the risk of corrosion under humid conditions. An important issue is the failures due to electrolytic metal migration. This paper describes an investigation of the electrolytic migration of Sn-Pb solder lines on PCBs in humid environments under applied potential conditions. Studies were carried out using two electrode potentiostatic polarization experiments and measuring the resulting current due to electrolytic migration. The surface morphology of the electrodes before and after migration testing was investigates using SEM and EDS. An in-service failure of a Ceramic Capacitor due to electrolytic migration in humid environments is also presented.

Bianchi Type-I Space-Time with Variable Cosmological Constant

Abstract: A spatially homogeneous and anisotropic Bianchi type-I perfect fluid model is considered with variable cosmological constant. Einstein’s field equations are solved by using a law of variation for mean Hubble’s parameter, which is related to average scale factor and that yields a constant value of deceleration parameter. An exact and singular Bianchi-I model is presented, where the cosmological constant remains positive and decreases with the cosmic time. It is found that the solutions are consistent with the recent observations of type Ia supernovae. A detailed study of physical and kinematical properties of the model is carried out.

Modeling of fillet welded joint of GMAW process: integrated approach using DOE, ANN and GA

Abstract: An integrated approach based on the use of Design of Experiment (DOE), Artificial Neural Networks (ANN) and Genetic Algorithm (GA) for modeling of Gas Metal Arc Welding (GMAW) process has been explained in this paper. The effects on the five weld bead geometric descriptors by the five weld process variables has been initiated by means of 2n-1 fractional factorial experimental design technique. In this study, the 2n-1 fractional factorial experimental design method was applied on the data available from a published work (Wu in Weld J 43(4):179s–183s, 1964) to determine the main effects as well as 2-factor interaction effects. Using the results of 25-1 fractional factorial design experiments, multiple linear regression equations are postulated for both main as well as 2-factor interaction effects. It is observed that, main and 2-factor interaction linear equations have resulted in a small error between the estimated and experimental values while multiple linear regression equations have fitted the data very well. Back-propagation neural networks are used to associate the welding process variables with the features of the weld bead geometry. It is seen that neural network for estimating the weld bead geometric parameters can be effectively implemented, with little error percentage difference between the estimated and experimental results. In this study, Genetic Algorithms are used for optimizing the process parameters. The five process variables optimized by the GA are well within the vectors of minimum and maximum values of the controllable process variables of the experimental conditions in all the bead geometry descriptor cases. It can be concluded that genetic algorithms can able to optimize the process parameters for the desired weld bead geometric parameters.

Security Requirements Elicitation Using View Points for Online System

Abstract: Security is of great concern for software engineering community for the development of online systems. To handle all the security issues properly we need to have well defined process for Security engineering and this process should be integrated with software development life cycle (SDLC). For integrating security engineering with SDLC the requirement engineers should have clearly understanding of what security requirements are and he/she is able to distinguish security requirements from various architectural and behavioral constraints. In this paper we go on to define a process for security requirements elicitation presenting techniques for activities like requirements discovery, analysis, prioritization and management. With true security requirements identified as early as possible and systematically identified, Architecture team can choose most appropriate mechanism to implement them.

An AHP approach for the selection of Advanced Manufacturing System: a case study

Abstract: Advance Manufacturing Techniques (AMT) help the manufacturing organisations to produce more customised products of higher quality and lower cost within a shorter time span. But implementation of AMT requires high investment and careful planning at all levels of the organisation. This paper presents the case of a traditional manufacturing company which wants to improve its productivity as well as its flexibility to meet its future requirements. Four alternative configurations of the machine shop are designed and Analytic Hierarchy Process (AHP) approach has been applied in the selection of best one.

A wavelet based significance test for periodicities in indian monsoon rainfall

Abstract: This paper is a sequel to a recent study of the authors' that uses a combination of multiresolution analysis (MRA) and classical Fourier spectral methods, to identify 17 peaks in the power spectral...