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41.
Jae Joon Ahn Hyun Woo Byun Kyong Joo Oh Tae Yoon Kim 《Expert systems with applications》2012,39(9):8369-8379
This study considers real estate appraisal forecasting problem. While there is a great deal of literature about use of artificial intelligence and multiple linear regression for the problem, there has been always controversy about which one performs better. Noting that this controversy is due to difficulty finding proper predictor variables in real estate appraisal, we propose a modified version of ridge regression, i.e., ridge regression coupled with genetic algorithm (GA-Ridge). In order to examine the performance of the proposed method, experimental study is done for Korean real estate market, which verifies that GA-Ridge is effective in forecasting real estate appraisal. This study addresses two critical issues regarding the use of ridge regression, i.e., when to use it and how to improve it. 相似文献
42.
Jong Hoo Paik Sahn Nahm Young Sik Kim Hyun Min Park Hwack Joo Lee Jae Dong Byun 《Journal of Materials Science》2003,38(3):621-628
The crystal structure of (Ba1–x
La
x
)[Mg(1 + x)/3Nb(2–x)/3]O3 (BLMN) ceramics with 0 x 1 was investigated using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). When the La content, x, was above 0.1, the 1:2 ordered hexagonal structure found in Ba(Mg1/3Nb2/3)O3 (BMN) was transformed into the 1:1 ordered cubic structure. The 1:1 ordered cubic structure was maintained up to x = 0.7. When x exceeded 0.7, however, BLMN exhibited a 1:1 ordered monoclinic structure, rather than a 1:1 ordered cubic structure. La(Mg2/3Nb1/3)O3 (LMN) has a 1:1 ordered monoclinic P21/n structure with a = 5.6004 Å, b = 5.6414 Å, c = 7.9346 Å, and = 89.9819°. The monoclinic LMN has the in-phase and the anti-phase tilt of oxygen octahedra. The anti-parallel shift of A-site cations was also found in LMN. 相似文献
43.
Linhan Ouyang Yizhong Ma Jai‐Hyun Byun Jianjun Wang Yiliu Tu 《Quality and Reliability Engineering International》2016,32(3):783-794
Multi‐response optimization methods rely on empirical process models based on the estimates of model parameters that relate response variables to a set of design variables. However, in determining the optimal conditions for the design variables, model uncertainty is typically neglected, resulting in an unstable optimal solution. This paper proposes a new optimization strategy that takes model uncertainty into account via the prediction region for multiple responses. To avoid obtaining an overly conservative design, the location and dispersion performances are constructed based on the best‐case strategy and the worst‐case strategy of expected loss. We reveal that the traditional loss function and the minimax/maximin strategy are both special cases of the proposed approach. An example is illustrated to present the procedure and the effectiveness of the proposed loss function. The results show that the proposed approach can give reasonable results when both the location and dispersion performances are important issues. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
44.
Woo‐Jin Byun Bong‐Su Kim Kwang Seon Kim Ki‐Chan Eun Myung‐Sun Song Reinhard Kulke Olaf Kersten Gregor Möllenbeck Matthias Rittweger 《ETRI Journal》2010,32(2):195-203
A new vertical transition between a substrate integrated waveguide in a low‐temperature co‐fired ceramic substrate and an air‐filled standard waveguide is proposed in this paper. A rectangular cavity resonator with closely spaced metallic vias is designed to connect the substrate integrated waveguide to the standard air‐filled waveguide. Physical characteristics of an air‐filled WR‐22 to WR‐22 transition are compared with those of the proposed transition. Simulation and experiment demonstrate that the proposed transition shows a ?1.3 dB insertion loss and 6.2 GHz bandwidth with a 10 dB return loss for the back‐to‐back module. A 40 GHz low‐temperature co‐fired ceramic module with the proposed vertical transition is also implemented. The implemented module is very compact, measuring 57 mm × 28 mm × 3.3 mm. 相似文献
45.
The purpose of this work is to study the effects of specularly reflecting wall under the combined radiative and laminar free
convective heat transfer in an infinite square duct. An absorbing and emitting gray medium is enclosed by the opaque and diffusely
emitting walls. The walls may reflect diffusely or specularly. Boussinesq approximation is used for the buoyancy term. The
radiative heat transfer is evaluated using the direct discrete ordinates method. The parameters under considerations are Rayleigh
number, conduction to radiation parameter, optical thickness, wall emissivity and reflection mode. The differences caused
by the reflection mode on the stream line, and temperature distribution and wall heat fluxes are studied. Some differences
are observed for the categories mentioned above if the order of the conduction to radiation parameter is less than order of
10-3 for the range of Rayleigh number studied. The differences at the side wall heat flux distributions are observed as long as
the medium is optically thin. As the top wall emissivity decreases, the differences between these two modes are increased.
As the optical thickness decreases at the fixed wall emissivity, the differences also increase. The difference of the streamlines
or the temperature contours is not as distinct as the side wall heat flux distributions. The specular reflection may alter
the fluid motion. 相似文献
46.
Jinwook Kim Jeongsik Yang Sangjin Byun Hyunduk Jun Jeongkyu Park Conroy C.S.G. Beomsup Kim 《Solid-State Circuits, IEEE Journal of》2005,40(2):462-471
This work presents a quad-channel serial-link transceiver providing a maximum full duplex raw data rate of 12.5Gb/s for a single 10-Gbit eXtended Attachment Unit Interface (XAUI) in a standard 0.18-/spl mu/m CMOS technology. To achieve low bit-error rate (BER) and high-speed operation, a mixed-mode least-mean-square (LMS) adaptive equalizer and a low-jitter delay-immune clock data recovery (CDR) circuit are used. The transceiver achieves BER lower than <4.5/spl times/10/sup -15/ while its transmitted data and recovered clock have a low jitter of 46 and 64 ps in peak-to-peak, respectively. The chip consumes 178 mW per each channel at 3.125-Gb/s/ch full duplex (TX/RX simultaneous) data rate from 1.8-V power supply. 相似文献
47.
Suh J.-Y. Byun J.-S. Shim J.-H. Oh Y.-J. Shim J.-D. 《Materials Science & Technology》2013,29(11-12):1277-1281
AbstractDifferent microstructures having acicular ferrite as the major phase but with various types and amounts of microphases were obtained by applying different cooling processes to C–Mn steels containing fine non-metallic inclusions. Optical and electron microscopy were carried out to identify the various microphases in the acicular ferrite microstructure, and their mechanical properties were measured and compared to study the effect of the microphases on the microstructure–properties relationship in C–Mn wrought steels. The existence and increase of the fraction of small isolated martensite between the acicular ferrite laths were found to play an important role in determining the tensile strength and low temperature impact toughness of the steels. However, the elongation and room temperature impact toughness were rather insensitive to the microphases. This may be attributed to the uniform distribution and isolation of relatively small martensite due to the fine interlocking character of the acicular ferrite microstructure. 相似文献
48.
In 2004, the American National Standards Institute approved the Role-Based Access Control standard to fulfill "a need among government and industry purchasers of information technology products for a consistent and uniform definition of role based access control (RBAC) features". Such uniform definitions give IT product vendors and customers a common and unambiguous terminology for RBAC features, which can lead to wider adoption of RBAC and increased productivity. However, the current ANSI RBAC Standard has several limitations, design flaws, and technical errors that, it unaddressed, could lead to confusions among IT product vendors and customers and to RBAC implementations with different semantics, thus defeating the standard's purpose. 相似文献
49.
The sulfonation of polymers and the pervaporation behavior of asymmetric polymeric membranes are described in this study. We confirmed that the sulfonic acid group was successively introduced into the polymer chain by FTIR and 1H‐NMR characterization. The phase diagram indicated that the modified polymer could have water tolerance, implying that the polymer–solvent miscibility was lower. The hyperthin skin layer, suitable for pervaporation, depended on the NMP–DGDE composition, which was important for the fabrication of an asymmetric membrane with high water permeance. The asymmetric membrane exhibited water selectivities equal to or slightly lower than those determined for the dense film. The hyperthin skin layer, which had hardly any defects, was possibly formed by the phase‐inversion method. It is obvious that these membranes can be used for the industrial pervaporation process. The permeability and the selectivity of the water–butanol mixture for the asymmetric membranes at 50°C were measured. The permeation rates for water–butanol in the asymmetric membrane were about 80 times greater than those of film, and the separation factor was slightly lower. The NMP–DGDE solvent system might be suitable for a high permeation rate. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 787–798, 2000 相似文献
50.
Graphitic thin films embedded with highly dispersed titanium dioxide (TiO(2)) nanoparticles were incorporated for the first time into the conventional dye-sensitized solar cells (DSSCs), resulting in a remarkably improved cell efficiency due to its superior electron conductivity. Massively ordered arrays of TiO(2) dots embedded in carbon matrix were fabricated via UV-stabilization of polystyrene-block-poly(4-vinylpyridine) films containing TiO(2) precursors followed by direct carbonization. For dye-sensitized TiO(2) based solar cells containing carbon/TiO(2) thin layers at both sides of pristine TiO(2) layer, an increase of 62.3% [corrected] in overall power conversion efficiency was achieved compared with neat TiO(2)-based DSSCs. Such a remarkably improved cell efficiency was ascribed to the superior electron conductivity and extended electron lifetime elucidated by cyclic voltammetry and impedance spectroscopy. 相似文献