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21.
Kyeong Joong Kim Jong-Yeul Suh Moon Gi Kang Kyu Tae Park 《Electronics letters》1998,34(13):1302-1303
The boundary is approximated by a polygon which can be encoded with the smallest number of bits for maximum distortion. The temporal redundancy between two successive frames is efficiently removed with the proposed scheme, resulting in a lower bit rate than the conventional algorithms 相似文献
22.
A new method to predict the critical heat flux (CHF) is proposed, based on the fuzzy clustering and artificial neural network. The fuzzy clustering classifies the experimental CHF data into a few data clusters (data groups) according to the data characteristics. After classification of the experimental data, the characteristics of the resulting clusters are discussed with emphasis on the distribution of the experimental conditions and physical mechanism. The CHF data in each group are trained in an artificial neural network to predict the CHF. The artificial neural network adjusts the weight so as to minimize the prediction error within the corresponding cluster. Application of the proposed method to the KAIST CHF data bank shows good prediction capability of the CHF, better than other existing methods. 相似文献
23.
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
24.
This paper deals with the pricing and investment decision problem of multi-modal transportation systems in which the congestion
is a significant factor in the assessment of system costs. This study approaches this congestion pricing problem with a number
of social welfare maximization problems, all of which have the identical structure except financial constraints. One welfare
maximization problem examined in this study yields the pricing and investment decision, which can attain the first-best social
optimality for multi-modal transportation systems. Other welfare maximization problems show he second-best optimal solutions
that can address two policy questions in transportation economics, namely, the cross-subsidy between competing modes and peak-period
congestion charges on a single highway link.
Received: February 2001/Accepted: December 2001
This work was supported in part by funds from BK21 Research Division of Seoul National University for Social Infrastructure
and Construction Technology. 相似文献
25.
Biomechanical finite element analysis of bone cemented hip crack initiation according to stem design
Byeongsoo Kim Byungyoung Moon Junghong Park 《Journal of Mechanical Science and Technology》2006,20(12):2168-2177
The purpose of this investigation was to determine the specific fracture mechanics response of cracks that initiate at the
stem-cement interface and propagate into the cement mantle. Two-dimensional finite element models of idealized stem-cement-bone
cross-sections from the proximal femur were developed for this study. Two general stem types were considered; Rectangular
shape and Charnley type stem designs. The FE results showed that the highest principal stress in the cement mantle for each
case occurred in the upper left and lower right regions adjacent to the stem-cement interface. There was also a general decrease
in maximum tensile stress with increasing cement mantle thickness for both Rectangular and Charnley-type stem designs. The
cement thickness is found to be one of the important fatigue failure parameters which affect the longevity of cemented femoral
components, in which the thinner cement was significantly associated with early mechanical failure for shot-time period. 相似文献
26.
27.
On-line dead-time compensation method using disturbance observer 总被引:7,自引:0,他引:7
Hyun-Soo Kim Hyung-Tae Moon Myung-Joong Youn 《Power Electronics, IEEE Transactions on》2003,18(6):1336-1345
A new on-line dead-time compensation method for a permanent magnet (PM) synchronous motor drive is proposed. Using a simple disturbance observer without any additional circuit and off-line experimental measurement, disturbance voltages in the rotor reference dq frame caused by the dead time and nonideal switching characteristics of power devices are estimated in an on-line manner and fed to voltage references in order to compensate the dead-time effects. The proposed method is applied to a PM synchronous motor drive system and implemented by using software of a digital signal processor (DSP) TMS320C31. Simulations and experiments are carried out for this system and the results well demonstrate the effectiveness of the proposed method. 相似文献
28.
A unified group technology implementation using the backpropagation learning rule of neural networks
Two engineering problems in implementing Group Technology are part family formation and part classification. Regardless of the approach adopted for the formation and classification, a critical problem is how to maintain consistency. The consistency problem can be addressed most effectively if the formation and classification is a single procedure rather than two separate procedures. A feedforward neural network using the Backpropagation learning rule is adopted to automatically generate part families during the part classification process. The spontaneous generalization capability of the neural network is utilized in classifying the parts into the families and creating new families if necessary. A heuristic algorithm using the neural network is described with an illustrative example. 相似文献
29.
Vemulapalli G. Hanumolu P.K. Youn-Jae Kook Un-Ku Moon 《Solid-State Circuits, IEEE Journal of》2005,40(9):1972-1977
An accurately tuned low-voltage linear continuous-time filter is presented in this paper. Accurate tuning is achieved using time-constant matched master-slave tuning combined with power-up mismatch calibration. A low-pass biquad designed for a corner frequency of 115 kHz achieves better than -80-dB total harmonic distortion with a 250-mV/sub pp/ 10-kHz input signal. The prototype implemented in 0.18-/spl mu/m CMOS process occupies an area of 0.4 mm/sup 2/ and dissipates 4.6 mW (2.6 mW for the filter and 2 mW for tuning) of power. 相似文献
30.
Precusors to the YBa2 Cu3 O7-δ material were prepared by both the oxalate precipitation method and conventional ceramic processing. Second-phase grains were observed to develop on the exposed fracture surface during annealing at 500° to 600°C in an ambient atmosphere. The second-phase grains were identified to be BaCO3 using EDX and XRD. The liquid phase, which was formed because of local chemical inhomogeneity in the Y-Ba-Cu-O system, contributed to the formation of second-phase grains as a source of Ba. 相似文献