A new gradient based particle swarm optimization algorithm for accurate computation of global minimum

Stochastic optimization algorithms like genetic algorithms (GAs) and particle swarm optimization (PSO) algorithms perform global optimization but waste computational effort by doing a random search. On the other hand deterministic algorithms like gradient descent converge rapidly but may get stuck in local minima of multimodal functions. Thus, an approach that combines the strengths of stochastic and deterministic optimization schemes but avoids their weaknesses is of interest. This paper presents a new hybrid optimization algorithm that combines the PSO algorithm and gradient-based local search algorithms to achieve faster convergence and better accuracy of final solution without getting trapped in local minima. In the new gradient-based PSO algorithm, referred to as the GPSO algorithm, the PSO algorithm is used for global exploration and a gradient based scheme is used for accurate local exploration. The global minimum is located by a process of finding progressively better local minima. The GPSO algorithm avoids the use of inertial weights and constriction coefficients which can cause the PSO algorithm to converge to a local minimum if improperly chosen. The De Jong test suite of benchmark optimization problems was used to test the new algorithm and facilitate comparison with the classical PSO algorithm. The GPSO algorithm is compared to four different refinements of the PSO algorithm from the literature and shown to converge faster to a significantly more accurate final solution for a variety of benchmark test functions.     

Solution of some boundary value problems in applied mechanics by the collocation least square method

The conventional simple but crude method of collocation is greatly improved by a least square augmentation. Simplicity in application and good accuracy of the proposed collocation least square scheme is demonstrated by the solution of some complex problems in applied mechanics.Example solutions of such problems include the linear and nonlinear analyses of isotropic plates, orthotropic plates and plates on elastic foundations. Numerical and graphical results are presented and compared with existing solutions. For the problems considered herein, the present method proves to be much less laborious than other numerical methods frequently employed by previous investigators.     

Achieving offshore software development success: An empirical analysis of risk mitigation through relational norms

Behavioral risks such as shirking and misappropriation of information assets are more prominent in offshore software development context and could adversely affect offshore outsourcing success. This paper studies the moderating effects of different relational norms on the link between behavioral risks and offshore software development success. We focused on three major modes of relational norms: norm of flexibility, norm of solidarity and norm of information exchange. Using PLS path modeling to test a sample of 40 US corporations engaged in offshore software development, we found that the norms of solidarity and flexibility reduced the negative effects shirking risk on offshore software development success. Our results suggest that client firms shall benefit by forming the right mode of relational norms to achieve offshore success.     

Enhanced infrared transmission characteristics of microwave-sintered $$\hbox {Y}_{2}\hbox {O}_{3}$$–$$\hbox {MgO}$$MgO nanocomposite

Infrared (IR) transparent ceramics are found to have applications in demanding defence and space missions. In this work, \(\hbox {Y}_{2}\hbox {O}_{3}\)–\(\hbox {MgO}\) nanocomposites were synthesised by a modified single-step combustion technique. The characterisation of the as-prepared powder by X-ray diffraction and transmission electron microscopy revealed the presence of cubic phases of ultra-fine nanostructured \(\hbox {Y}_{2}\hbox {O}_{3 }\) and MgO, with an average crystallite size of \({\sim }19 \hbox { nm}\). For the first time the resistive and microwave heatings were effectively coupled for sintering the sample, and it was found that the sintering temperature and soaking time were reduced considerably. The pellets were sintered to 99.2% of the theoretical density at \(1430{^{\circ }}\hbox {C}\) for a soaking duration of 20 min. The well-sintered pellets with an average grain size of \({\sim }200 \hbox { nm}\) showed better transmittance properties relative to pure yttria. The promising percentage transmission of 80% in the UV–visible region and 82% in the mid-IR region shown by \(\hbox {Y}_{2}\hbox {O}_{3}\)–\(\hbox {MgO}\) nanocomposites can be tailored and made cost-effective to fabricate high-quality IR windows for strategic defence and space missions.     

Boundary layer transition experiments with embedded streamwise vortices

Experiments were conducted with a counter-rotating, streamwise vortex pair embedded in flat plate boundary layers, in a low-turbulence wind tunnel, to understand the role of local separation on transition. Steady, streamwise vortices were generated downstream of gaps in spanwise-uniform, smooth hills (of height h) affixed to the plate, 175 mm from its leading edge. The flow between is directed away from the plate. At the four tunnel speeds 1.8–3.5 m/s considered, the Reynolds numbers based on displacement thickness at this location varied from 248 to 346. Small, medium and large gaps of 2, 4 and 8 mm, respectively, were set up; they were about a third to twice the boundary layer thickness (\(2/3< b/h < 8/3\)). With the closest vortex pairs, transition was observed at all freestream speeds considered. With larger spacing, transition occurred at the highest speed only. The vortex pair caused the flow to separate in all but the largest-gap cases. Separation was steady and re-attachment unsteady in all cases. Velocity fluctuations grew slightly upstream of re-attachment in transitional cases. No evidence was found for separation or re-attachment as a direct cause for transition; transition occurred even without separation. Instead, whenever transition was observed, its origin could be traced to instability of a streak of sufficient amplitude that had been created by the vortex pair. Streak instability appeared as fluctuations growing along its sides and spreading. Anomalous behaviour was also observed with moderate spacing, where transition did not occur in spite of flow separation and streak amplitudes in excess of known thresholds for streak instability.     

Scheduling and variable binding for improved testability in high level synthesis

In this paper, we present a scheduling and a variable binding technique for improved testability in high level synthesis. The scheduling technique called cost based scheduling system (CBSS), is time constrained which minimizes the number of resources (operations) and the number of registers based on a cost function. The CBSS improves the life time of primary input and primary output variables, reduces the life times of intermediate variables and hence improves the controllability and observability. The testability of the register transfer level (RTL) structure generated by this schedule is therefore improved. CBSS considers all the variables and operations jointly for scheduling. CBSS supports various scheduling modes such as multicycled and chained operations, and pipelining. The complexity of our scheduling algorithm is O(c·n²) where c is the number of control steps and n is the number of operations to be scheduled. To generate a highly testable RTL structure, the CBSS is followed by a variable binding technique to bind the variables into registers. An integer linear programming (ILP) approach is proposed with an objective function that minimizes the number of registers and a set of constraints that improves the testability of the RTL structure. Various case studies are presented and the results on different benchmark examples show the potential of our approach.     

A bidding mechanism for Web-based agents involved in information classification

The impact of the World Wide Web on providing an easy information access is clearly evident in all aspects of today's life. As attractive as the information availability is, due to its sheer volume, it creates an information-overload on users. Agent-based collaborative filtering is a technique used to effectively counter this burden. For agents to collaborate successfully, and maintain an overall progress of the entire interconnected environment, a governing mechanism is necessary. In this article, we present an economic framework based on a bidding mechanism for agents to communicate and negotiate with each other, thereby achieving collaborative information classification. D-SIFTER, a system developed using this economic framework, is described along with various experiments and their results.     

Experimental Investigations into the Effects of Microelectric-Discharge Milling Process Parameters on Processing Ti–6Al–4V

Microelectric-discharge milling is acquiring more importance in micromanufacturing because of its unique ability to produce three-dimensional microcavities with high aspect ratio in electrically conductive advanced materials regardless of its mechanical properties. The present study investigates the effects of major microelectric-discharge milling process variables [voltage (V), capacitance (C), electrode rotational speed (ERS), and feed rate (FR)] on Ti–6Al–4V. The output performance measures were identified as material removal rate (MRR) and tool wear rate (TWR) to assess the machinability of Ti–6Al–4V. Experiments were designed and carried out based on response surface methodology-Box-Behnken statistical design. The most influencing parameters for responses (MRR, TWR) were found to be capacitance and FR. At a capacitance of 0.4 µF and FR of 18 mm/min, maximum MRR of 0.9756 mg/h, and TWR of 0.6342 mg/h were observed. Similarly at 0.01 µF and 6 mm/min, minimum MRR of 0.2308 mg/h, and TWR of 0.1259 mg/h were obtained.