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991.
In this paper, we consider the problem of how to represent the locations of Internet hosts in a Cartesian coordinate system to facilitate estimation of network distances among arbitrary Internet hosts. We envision an infrastructure that consists of beacon nodes and provides the service of estimating network distance between pairs of hosts without direct delay measurement. We show that the principal component analysis (PCA) technique can effectively extract topological information from delay measurements between beacon hosts. Based on PCA, we devise a transformation method that projects the raw distance space into a new coordinate system of (much) smaller dimensions. The transformation retains as much topological information as possible and yet enables end hosts to determine their coordinates in the coordinate system. The resulting new coordinate system is termed as the Internet Coordinate System (ICS). As compared to existing work (e.g., IDMaps and GNP), ICS incurs smaller computation overhead in calculating the coordinates of hosts and smaller measurement overhead (required for end hosts to measure their distances to beacon hosts). Finally, we show via experiments with both real-life and synthetic data sets that ICS makes robust and accurate estimates of network distances, incurs little computational overhead, and its performance is not susceptible to the number of beacon nodes (as long as it exceeds a certain threshold) and the network topology. 相似文献
992.
S. K. Choi S. R. Kim D. G. Choi 《Journal of Materials Science: Materials in Electronics》2000,11(8):603-607
The effect of the tetragonality (c/a) ratio on photo-induced domain switching in (Pb1-xLax)TiO3 ferroelectric ceramics preliminarily poled at 1.5kVmm-1 was investigated by measuring photovoltaic current and acoustic emission (AE) signals. Results of total increment of photovoltaic current (Jpv), total AE event count and AE energy distribution showed that non-steady state behavior of Jpv was dominantly dependent on the activity of 90° domain switching during illumination. The activity of photo-induced domain switching was explained in terms of the coercive field and the space charge field. It was confirmed that the magnitudes of the space charge field and coercive field were found to be optimal for the photo-induced 90° domain switching at a c/a of 1.021. 相似文献
993.
994.
J. H. Choi W. H. Lee J. J. Park B. D. Youn 《Structural and Multidisciplinary Optimization》2008,35(6):531-540
Design optimization of layered plate bonding process is conducted by considering uncertainties in a manufacturing process,
to reduce the crack failure arising due to the difference of thermal expansion coefficients of the adherents. Robust optimization
is performed to minimize the mean and variance of the residual stress, which is the major cause of the failure, while constraining
the distortion and the instantaneous maximum stress to the allowable limits. In this optimization, the dimension reduction
(DR) method is employed to quantify the uncertainty of the responses in the bonding process. It is expected that the DR method
benefits the optimization from the perspectives of efficiency, accuracy, and simplicity. Response surface method (RSM) combined
with sequential approximate optimization (SAO) technique is employed as an optimization tool. The obtained robust optimal
solution is verified by the Monte Carlo simulation. 相似文献
995.
996.
Ho-Lim Choi Hee-Jung Byun Won-Gyu Song Jun-Won Son Jong-Tae Lim 《Artificial Life and Robotics》2000,4(4):193-197
We present a method to calssify electromyogram (EMG) signals which are utilized as control signals for a patient-responsive
walker-supported system for paraplegics. Patterns of EMG signals for different walking motions are classified via adequate
filtering, real EMG signal extraction, AR-modeling, and a modified self-organizing feature map (MSOFM). In particular, a data-reducing
extraction algorithm is employed for real EMG signals. Moreover, MSOFM classifies and determines the results automatically
using a fixed map. Finally, the experimental results are presented for validation. 相似文献
997.
Byung Rae Cho Sangmun Shin Yongsun Choi Jami Kovach 《The International Journal of Advanced Manufacturing Technology》2009,44(9-10):841-853
Pharmaceutical formulation design with the development of analytical technologies and methodologies is an integral part of a drug’s research and development. Conventional pharmaceutical formulation design problems are typically studied under the assumption of an unconstrained experimental region with a single quality characteristic. In real world pharmaceutical formulation design problems, however, we are often faced with multiple quality characteristics with a constrained experimental region due to physical limitations. In order to address these needs, we propose a multidisciplinary optimization process for the optimal design of pharmaceutical formulations by developing a response surface simplex design (RSSD) and a response surface D-optimal design (REDD) for experimental modeling and by developing a partitioned composite desirability function (PCDF) for multidisciplinary optimization. Two actual case studies are also presented here for model verification purposes. 相似文献
998.
Young-Keun Choi Dong Myung Lee Yeong Bin Cho 《The International Journal of Advanced Manufacturing Technology》2009,42(1-2):180-188
This paper focuses on multi-criteria assembly sequence planning (ASP) known as a large-scale, time-consuming combinatorial problem. Although the ASP problem has been tackled via a variety of optimization techniques, these techniques are often inefficient when applied to larger-scale problems. Genetic algorithm (GA) is the most widely known type of evolutionary computation method, incorporating biological concepts into analytical studies of systems. In this research, an approach is proposed to optimize multi-criteria ASP based on GA. A precedence matrix is proposed to determine feasible assembly sequences that satisfy precedence constraints. A numerical example is presented to demonstrate the performance of the proposed algorithm. The results of comparison in the provided experiment show that the developed algorithm is an efficient approach to solve the ASP problem and can be suitably applied to any kind of ASP with large numbers of components and multi-objective functions. 相似文献
999.
1000.
A Fabry-Perot hemispherical open resonator is designed and constructed in order to measure dielectric properties of BeO in the Ka-band (26 – 40 GHz) frequency range. Based on both analytic calculations and simulations by a 3-D finite element electromagnetic code, HFSS, the hemispherical open resonator is designed to excite a TEM0,0,17 mode at 28 GHz. The TEM0,0,17 mode is experimentally identified by a field perturbation technique. Dielectric measurements are made by both frequency variation and length variation methods. Measurements show that permittivity and loss tangent of BeO are 6.69 and 6.5 × 10?4 - 7.2× 10?4, respectively, in the frequency range of 26 – 34 GHz. 相似文献