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911.
Anirban Chatterjee G. K. Mahanti Ananya Mahanti 《International Journal of Numerical Modelling》2015,28(2):164-174
A binary firefly algorithm inspired by the behavior of artificial fireflies has been applied to thin a planar concentric ring array antenna to minimize the peak sidelobe level in a number of predefined ϕ‐planes. Two different cases comprising two different design specifications for the optimized thinned array have been considered. In the first case, the array is thinned to reduce the peak sidelobe level while keeping the first null beamwidth and half power beamwidth of the array below their specified values in all the defined ϕ‐planes. In the second case, peak sidelobe level of the array is reduced regardless of any pre‐specified values of first null beamwidth and half power beamwidth. To illustrate the superiority of binary firefly algorithm, the thinning of the array for the two different cases has been compared with binary particle swarm optimization algorithm. Results clearly show the superiority of binary firefly algorithm in finding optimum solutions for both cases. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
912.
Material selection is a very fast growing multi-criteria decision-making (MCDM) problem involving a large number of factors influencing the selection process. Proper choice of material is a critical issue for the success and competitiveness of the manufacturing organizations in the global market. Selection of the most appropriate material for a particular engineering application is a time consuming and expensive process where several candidate materials available in the market are taken into consideration as the tentative alternatives. Although a large number of mathematical approaches is now available to evaluate, select and rank the alternative materials for a given engineering application, this paper explores the applicability and capability of two almost new MCDM methods, i.e. complex proportional assessment (COPRAS) and evaluation of mixed data (EVAMIX) methods for materials selection. These two methods are used to rank the alternative materials, for which several requirements are considered simultaneously. Two illustrative examples are cited which prove that these two MCDM methods can be effectively applied to solve the real time material selection problems. In each example, a list of all the possible choices from the best to the worst suitable materials is obtained which almost match with the rankings as derived by the past researchers. 相似文献
913.
The spherulitic linear growth rates of a homo-poly(propylene) and a series of propylene-ethylene copolymers, all synthesized with the same type of metallocene catalyst were analyzed. The inter-chain distribution of comonomer content is uniform in these copolymers and the intra-chain distribution adheres to the random behavior. Furthermore, the concentration of stereo and regio defects is constant for all copolymers. Thus, with these polymers it was possible to investigate the influence of ethylene content on the crystallization kinetics, as extracted from their linear growth rates. All iPPs investigated display mixed polymorphic behavior during isothermal crystallization and major emphasis was given to integrate the simultaneous development of the α and γ polymorphs, and their intimate structural relations during growth, in the analysis of the crystallization kinetics. A sharp break in spherulitic growth is found between times domains of mixed α+γ growth and growth of pure γ crystals reflecting a drastic change in growth mechanisms at the point where α development ceases. The rates corresponding to α growth are significantly higher than those characteristics of γ growth. In addition, growth data in the domain of mixed α+γ growth, which, following the structural models for α and γ branching, reflect the growth pattern of α crystals, display a discontinuity in the temperature gradient at the changeover from growth of mixed α+γ to γ dominated growth. This behavior correlates with that found in other systems that undergo a similar extended chain to folded change in crystallization mechanisms. The temperature coefficient of the linear growth rates is analyzed according to regime theory for both domains of growth. The results allow a quantitative framework for discussion of the interfacial free energies of α and γ crystals obtained from this analysis. 相似文献
914.
C. V. Jiji Subhasis Chaudhuri Priyam Chatterjee 《Multidimensional Systems and Signal Processing》2007,18(2-3):123-152
In this paper we study the usefulness of different local and global, learning-based, single-frame image super-resolution reconstruction
techniques in handling three specific tasks, namely, de-blurring, de-noising and alias removal. We start with the global,
iterative Papoulis–Gerchberg method for super-resolving a scene. Next we describe a PCA-based global method which faithfully
reproduces a super-resolved image from a blurred and noisy low resolution input. We also study several multi-resolution processing
schemes for super-resolution where the best edges are learned locally from an image database. We show that the PCA-based global
method is efficient in handling blur and noise in the data. The local methods are adept in capturing the edges properly. However,
both local and global approaches cannot properly handle the aliasing present in the low resolution observation. Hence we propose
an alias removal technique by designing an alias-free upsampling scheme. Here the unknown high frequency components of the
given partially aliased (low resolution) image is generated by minimizing the total variation of the interpolant subject to
the constraint that part of alias free spectral components in the low resolution observation are known precisely and under
the assumption of sparsity in the data. 相似文献
915.
Tuhin Chatterjee 《Polymer-Plastics Technology and Engineering》2019,58(6):630-640
Shape memory polymer nanocomposite of EOC-EPDM blend has been prepared by the incertion of two different types of POSS nanoclay namely octaisobutyl POSS and trisilanolIsobutyl POSS. Compared to TSIB POSS, OIB POSS shows significant impact upon the shape memory behaviour of the blend. With increasing amount of POSS nanoclay, reduction in percentage shape fixity is lower for the nanocomposite containing OIB POSS rather than the TSIB POSS containing nanocomposite. On the other side, presence of closed cage like structure also results higher shape recovery ratio and lower shape recovery induction time for OIB POSS containing nanocomposite. 相似文献
916.
The phenomenon of stress relaxation in thermoplastic elastomers (TPEs) is common and influences the end-use properties of polymers. Temperature scanning stress relaxation (TSSR) method extends an advanced method to study the stress relaxation of TPEs at elevated temperatures. A reactive blend system based on maleic anhydride grafted styrene-ethylene-butylene-styrene and thermoplastic polyurethane is explored for its relaxation behavior at temperature up to 200°C with TSSR meter. The relaxation spectrum revealed the transitions occurring in the blends as well as the extent of interfacial interaction present. Direct measurement of elasticity of the blends was obtained from the TSSR index (RI). Glass transition temperature of the samples was measured from dynamic mechanical analysis. The elastic nature of the blends was also pursued from the storage modulus values and results were in line with TSSR results. The density of crosslinks in the system was assessed with both TSSR and the conventional Flory-Rehner equation and a similar trend was obtained. Atomic force microscopy and scanning electron microscopy revealed the dispersed morphology of the blends. 相似文献
917.
Development of a Management Model for a Surface Waterlogged and Drainage Congested Area 总被引:2,自引:0,他引:2
Lohani Anil K. Ghosh Narayan C. Chatterjee Chandranath 《Water Resources Management》2004,18(5):497-518
Inadequate drainage outlet causing surface waterlogging every year mainly during monsoon period (June through October) over a depressed land of 1062 km2 in Mokama group of tals, India, led to a loss of one crop rotation. A management model aiming at minimization of the waterlogged area under constraints of control monsoon runoffs from tributaries discharge water to the depressed land has been developed. Magnitudes of regulated flows are guided by irrigation water requirement of crops grown in commands of different tributaries joined to the depressed land. A nonlinear optimization model has been envisaged and solved setting a total of 160 constraints satisfying conditions of water requirement for crops grown in two seasons and their time-dependent storage requirement. The optimization model has been solved using the Quantitative Systems for Business (QSB) software, which considers a line search methodology for unconstrained problems, and a sequential unconstrained minimization technique (SUMT) with penalty function methodology for constrained problems. The management model provides a solution for strategic water resources development and management in a basin having problems of scarcity, surplus and non-uniform distribution of surface water. 相似文献
918.
Rima Chatterjee Manoj Mukhopadhyay 《Bulletin of Engineering Geology and the Environment》2002,61(2):169-178
The petrophysical and mechanical properties of reservoir rocks from two major basins on the east coast of India were studied using samples cored from 19 wells in the Krishna-Godavari and Cauvery basins. Several of these drill holes are located in the producing oilfields in these basins. The purpose of the study was to investigate the relationships between the properties of the rocks including dry density, effective porosity, uniaxial compressive strength, tensile strength and Young's modulus. Their relationships are further elucidated using regression analyses. The results indicated that the petrophysical and geomechanical properties vary widely for the different sedimentary rocks and basement samples related to their depth and geological age. It is emphasized that the work should be further extended to assess its full potential in reservoir studies of the oilfields in these basins. 相似文献
919.
Characterization of transition joints of commercially pure titanium to 304 stainless steel 总被引:4,自引:0,他引:4
Solid-state direct bonding between commercially pure titanium and type 304 austenitic stainless steel has been carried out in the temperature range of 850–950 °C, under a uniaxial pressure of 3 MPa for 1 h. The diffusion bonds have been evaluated using light microscopy, electron probe microanalysis (EPMA), X-ray diffraction (XRD) technique and tensile testing. Light microscopy shows that different intermediate layers are formed in the reaction zone, and the width of these layers increases with an increase in bonding temperature. EPMA revealed that, at any particular bonding temperature, Ti traverses a minimum distance in the 304 stainless steel side, whereas Fe, Cr and Ni travel comparatively larger distances in the Ti side. This microanalysis also indicated different step formations in the concentration profile of Ti, Fe and Cr over different composition ranges in the diffusion zone indicating formation of intermetallic phases that were detected by XRD. Brittle intermetallic phases lower the strength and ductility of the diffusion bonded couples significantly. Best room temperature tensile strength, 217 MPa, has been obtained at 850 °C processing temperature due to minimal deleterious effects. 相似文献
920.
Pant P. De V.K. Chatterjee A. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1998,6(4):538-545
This paper demonstrates a new approach for minimizing the total of the static and the dynamic power dissipation components in a complementary metal-oxide-semiconductor (CMOS) logic network required to operate at a specified clock frequency. The algorithms presented can be used to design ultralow-power CMOS logic circuits by joint optimization of supply voltage, threshold voltage and device widths. The static, dynamic and short-circuit energy components are considered and an efficient heuristic is developed that delivers over an order of magnitude savings in power over conventional optimization methods 相似文献