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991.
Gyoojae Choi Yungmyun Yoo Jongsoon Im 《Journal of Mechanical Science and Technology》2001,15(8):1090-1096
In this paper, new methods for efficiently solving linear acceleration equations of multibody dynamic simulation exploiting sparsity for real-time simulation are presented. The coefficient matrix of the equations tends to have a large number of zero entries according to the relative joint coordinate numbering. By adequate joint coordinate numbering, the matrix has minimum off-diagonal terms and a block pattern of non-zero entries and can be solved efficiently. The proposed methods, using sparse Cholesky method and recursive block mass matrix method, take advantages of both the special structure and the sparsity of the coefficient matrix to reduce computation time. The first method solves thenxn sparse coefficient matrix for the accelerations, wheren denotes the number of relative coordinates. In the second method, for vehicle dynamic simulation, simple manipulations bring the original problem of dimensionnxn to an equivalent problem of dimension 6×6 to be solved for the accelerations of a vehicle chassis. For vehicle dynamic simulation, the proposed solution methods are proved to be more efficient than the classical approaches using reduced Lagrangian multiplier method. With the methods computation time for real-time vehicle dynamic simulation can be reduced up to 14 per cent compared to the classical approach. 相似文献
992.
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
993.
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
994.
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
995.
996.
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
997.
Hyung-Yun Choi 《Journal of Mechanical Science and Technology》2001,15(7):995-1001
The finite element human head model is developed for traumatic injury assessment. The model is constructed based on the precise anatomical geometry and validated with test results. In this paper, structural and physiologic explanation of human head will be introduced as well as the modeling methodology. Some of simulation results are also chosen to present major features of the model. 相似文献
998.
Nonlinear analysis of 3-D steel frames 总被引:1,自引:0,他引:1
In this paper, a nonlinear analysis of three-dimensional steel frames is developed. This analysis accounts for material and geometric nonlinearities. The material nonlinearity considers the gradual yielding associated with member forces. The geometric nonlinearity includes the second-order effects associated with P-δ and P-Δ. The material nonlinearity at a section is considered using the concept of the P–M hinge consisting of many fibers. The geometric nonlinearity is considered by the use of stability functions. The modified incremental displacement method is used as the solution technique. The load–displacement relationships predicted by the proposed analysis compare well with those given by other approaches. 相似文献
999.
Soo Cheong Chang Jin Sung Yoo Je Wan Woo Joong So Choi 《Korean Journal of Chemical Engineering》1999,16(5):581-584
Superabsorbent poly(acrylamide-sodiumallylsulfonate) was synthesized from acrylamide (AM) and sodiumallylsulfonate (SAS) by
a solution polymerization method. N,N’-methylenebisacrylamide (BIS) was used as the crosslinker; potassium persulfite (PP)
and N,N,N’,N’-tetra-methylenediamine (TMEDA) were used as the redox initiator during the synthesis. The absorption capacities
of the synthesized superabsorbent poly(AM-SAS) were repeatedly measured to obtain the optimal poly(AM-SAS) according to the
variations of monomer concentration at 298.15 K. Its maximal absorption capacity appeared as 811 times at 0.1 mol/L among
from 0.01 mol/L to 0.16 mol/L of SAS concentrations. The swelling equilibria at those conditions from 298.15 K to 318.15 K
were measured and used to estimate the parameters by correlating with the Flory-Huggins model. The swelling behavior could
be described by the parameters and the calculated values agreed satisfactorily with the experimental data. 相似文献
1000.
Polyelectrolyte multilayer films composed of a polycation (poly(allylamine hydrochloride) PAH) and a polyanion (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) PEDOT:PSS) were prepared by a spin self-assembly method, and their electrochemical and electrochromic properties were investigated. The change in the surface charge and the optical absorption spectra of the multilayer films revealed that sequential deposition of polyelectrolyte was successfully achieved during the spin self-assembly. The electrochromic properties of 20-bilayered PAH/PEDOT:PSS were also investigated. The response time for the coloring and bleaching processes was 6.2 and 2.5 s, respectively, and the coloration efficiency was 199.3 cm2/C. These results indicate that a spin self-assembly process could be a viable alternative for the fabrication of electrochromic devices. 相似文献