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The main purpose of this paper is to compare the performance of three commonly used global search algorithms, namely tree‐based augmented spatial digital tree, cell‐based no binary search and D‐cell, in the discrete element simulations.

A large number of test cases with up to five million particles/discrete objects are employed to numerically examine the computational costs of the three search algorithms and their performance is compared.

Comprehensive comparisons reveal that the D‐cell is more efficient than the tree‐based search algorithms for large‐scale problems. The parametric study of the D‐cell algorithm itself shows that the performance of the algorithm is strongly dependent on the cell dimension chosen.

The only limitation of the current work is that the tested domain shape is regular, and thus more complex domain shapes may need to be considered.

The paper provides clear guidance regarding the possible actual computational performance of the tested search algorithms for practical applications.

Conjugate laminar forced convection heat transfer in the entry region of eccentric annuli is numerically investigated. Heat transfer parameters are presented for a fluid of Pr = 0.7 flowing in an annulus of radius ratio 0.5 for four values of dimensionless eccentricity ranging from 0.1 to 0.7. Solid‐fluid conductivity ratio (KR) is varied to cover the range for practical cases with commonly encountered inner and outer tube thickness. Boundary conditions applied are isothermal heating of the inner surface of the core tube, while the outer surface of the external tube is maintained at the inlet fluid temperature. Limits for KR above which the conjugation can be neglected are obtained.

The purpose of this paper is to investigate the effect of reinforcement, inhomogeneity and initial stress on the propagation of shear waves. The problem consists of magneto poroelastic medium sandwiched between self-reinforced medium and poroelastic half space. Using Biot’s theory of wave propagation, the frequency equation is obtained.

Shear wave propagation in magneto poroelastic medium embedded between a self-reinforced medium and poroelastic half space is investigated. This particular setup is quite possible in the Earth crust. All the three media are assumed to be inhomogeneous under initial stress. The significant effects of initial stress and inhomogeneity parameters of individual media have been studied.

Phase velocity is computed against wavenumber for various values of self-reinforcement, heterogeneity parameter and initial stress. Classical elasticity results are deduced as a particular case of the present study. Also in the absence of inhomogeneity and initial stress, frequency equation is discussed. Graphical representation is made to exhibit the results.

Shear wave propagation in magneto poroelastic medium embedded between a self-reinforced medium, and poroelastic half space are investigated in presence of initial stress, and inhomogeneity parameter. For heterogeneous poroelastic half space, the Whittaker’s solution is obtained. From the numerical results, it is observed that heterogeneity parameter, inhomogeneity parameter and reinforcement parameter have significant influences on the wave characteristics. In addition, frequency equation is discussed in absence of inhomogeneity and initial stress. For the validation purpose, numerical results are also computed for a particular case.

PROPELLERS, fans and axial compressors are all airscrews, the only difference being in the use to which they are put. Propeller theory and practice has been put on a firm basis by men like Glauert and the parameters used are now well established. The question therefore arises of whether or not it is advisable to hand over the parameters and results of propeller theory to the theory and practice of axial compressors.

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.

The purpose of this study was to analyze the heat transfer in a square porous cavity that has a solid block placed at its center. The prime focus of this study is to investigate the effect of size of the square solid block and other physical parameters on the heat transfer rate from the hot surface into the porous medium. The left vertical surface of cavity is maintained at a hot temperature and the right vertical surface at a cool temperature, T_c. The finite element method is used to simplify the governing equations and is solved iteratively. It is noted that the size of the solid block plays a vital role in dictating the heat transfer from the hot surface to porous medium.

The current work is based on finite element formulation of a square porous cavity that has a solid square block placed at its center. Governing equations were solved iteratively.

The size of the solid block has a pronounced effect on the heat transfer behavior inside the porous cavity.

This study highlights the heat transfer due to a conducting square solid block at mid of porous cavity.

Finds the regions of dynamic instability of elastic beams constrained at the ends by means of translational and rotational elastic springs, using the equation of boundary frequencies. Obtains the diagrams showing the regions of instability of the beam, as a function of the dynamic component of the periodic forcing function and its frequency, from that equation in exact form. In this procedure inertial, stiffness and constraint characteristics of the examined system are taken into account. Presents selected applications concerning the analysed problem.

The purpose of this paper is to introduce two new automatic methods for evaluating the performance of search engines. The reported study uses the methods to experimentally investigate which search engine among three popular search engines (Ask.com, Bing and Google) gives the best performance.

The study assesses the performance of three search engines. For each one the weighted average of similarity degrees between its ranked result list and those of its metasearch engines is measured. Next these measures are compared to establish which search engine gives the best performance. To compute the similarity degree between the lists two measures called the “tendency degree” and “coverage degree” are introduced; the former assesses a search engine in terms of results presentation and the latter evaluates it in terms of retrieval effectiveness. The performance of the search engines is experimentally assessed based on the 50 topics of the 2002 TREC web track. The effectiveness of the methods is also compared with human‐based ones.

Google outperformed the others, followed by Bing and Ask.com. Moreover significant degrees of consistency – 92.87 percent and 91.93 percent – were found between automatic and human‐based approaches.

The findings of this work could help users to select a truly effective search engine. The results also provide motivation for the vendors of web search engines to improve their technology.

The paper focuses on two novel automatic methods to evaluate the performance of search engines and provides valuable experimental results on three popular ones.

In multihop wireless networks, the number of neighbors has an important role in the network performance since links are dynamically formed between a node and its neighbors. This paper aims to investigate this issue.

The paper quantitatively studies the effects of the average number of neighbors in multihop wireless networks on the network connectivity, the number of hops needed to traverse a certain distance, which can be used to determine the hop diameter of a network, and the total energy consumed by packet transmission, which can be used to choose an optimum average number of neighbors that minimizes the energy consumption. This paper also presents an analysis of the energy consumption that can be applied to a wide range of access protocols and show the effect of a variety of factors.

Results show that the minimum average number of neighbors to guarantee the overall network connectivity depends on the size of a network coverage. There is a sharp knee in the network connectivity with decrease of the average number of neighbors, N. If the distance between a source and destination, d, is known, the number of hops needed to reach the destination is usually between d/R∼2d/R, where R is the transmission range. A larger average number of neighbors N leads to a smaller number of hops to traverse a certain distance, which in turn results in a smaller traffic load caused by relaying packets. However, a bigger N also causes more collisions when a contention medium access scheme is used, which leads to more energy consumed by packet transmission. The results show that the optimum N which minimizes the energy is obtained by balancing several factors affecting the energy.

The paper provides a useful study on the effects of the number of neighbors in multihop wireless networks.

This paper examines global imbalance and rebalancing issues from the viewpoint of Korea. As IMF (2009) notes, the unwinding of global imbalance seems inevitable and, in fact, it is in progress. We illustrate that Korea, with a flexible exchange rate system and relatively balanced current accounts, has little direct linkage to global imbalance. However, we also find that Korea is not immune to the costly adjustment process of imbalance due to the triangular trade between Korea, China and the U.S. The fact that Korea is ‘indirectly’ linked to global imbalance limits Korea’s ability to cope with the situation. Boosting domestic demand, often mentioned recommendation for East Asia, is not an appropriate solution for Korea with low personal savings rate. A lot depends on China’s policy. If China reduces its dependence on U.S. market and increases domestic consumption despite unemployment risk in export manufacturing sector, it will provide Korea with an opportunity for more stable growth based on China’s final demand. Korea can also make efforts to increase economic integration and expand monetary cooperation in Asia that would help to increase consumption demands and final goods trade in the region.