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981.
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
982.
983.
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
984.
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
985.
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
986.
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
987.
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
988.
A class of adaptive hybrid ARQ schemes for wireless links 总被引:1,自引:0,他引:1
Wireless links are known to suffer location-dependent, time-varying, and bursty errors. This paper considers a class of adaptive error-control schemes in the data link layer for reliable communication over wireless links in which the error-control code and the frame length are chosen adaptively, based on the estimated channel state/condition. Three error-control schemes are considered according to: (1) the number of Reed Solomon code segments a packet is divided into and (2) the way a lost packet is retransmitted. Through throughput performance and computation complexity analyses, these three schemes are compared, and then one of them is claimed to be the most attractive in terms of computation complexity and practicality even though its throughput performance is not the best. The simulation results also verify that this scheme works well over a time-varying fading channel. Error control for the medium access control (MAC) header and its effect on the performance of each error-control scheme are also considered since, without proper error protection for the header, it would be futile to exercise error control on the user data 相似文献
989.
Ki Hyuk Kim Hoi Ju Chung Sung Ho Yoon Sung Woo Hwang Jinwoo Park Soo-Won Kim Joongho Choi Ahn D. 《Components and Packaging Technologies, IEEE Transactions on》2000,23(1):183-189
We present a systematic analysis technique of complementary metal-oxide-semiconductor (CMOS) radio-frequency (RF) integrated circuits (ICs). A full simulation program with integrated circuit emphasis (SPICE) simulation of the whole chip including the package and the die, with the parameters extracted from purely software analysis, has been performed. It is shown that the RF impedance matching without S-parameter based techniques is possible and the measured results agree well with our SPICE-only software based technique 相似文献
990.
Ju H. Choi Alfred Margaryan Ashot Margaryan Frank G. Shi 《Journal of Materials Science》2008,43(3):1109-1113
The dependence of thermo-mechanical, and mechanical properties on various rare earth dopants (RE) including Nd2O3, Er2O3, and Yb2O3 in 0.4MgF2-0.4BaF2-0.1Ba(PO3)2-0.1Al(PO3)3 glasses (MBBA system) is systematically investigated. MBBA system doped with RE dopants presented the potential application
in the field of communication and high power layer system in the previous reports. In this work, it is found that the density
of the doped glass increases with an increasing of RE concentration, which could be understood in terms of cationic field
strength (CFS) effect. The Knoop hardness is found to decrease with the loading time and dopant concentration due to the indentation
size effect (ISE) effect. The observed decrease of thermal expansion coefficient and the increase of glass transition temperature
T
g with increasing dopant concentration are elucidated in terms of the increasing number of strong covalent bonds with increasing
RE dopant concentration. Those results will be of paramount importance before designing optical devices. 相似文献