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41.
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
42.
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
43.
44.
Daniel Won‐Kyu Hong Choong Seon Hong 《International Journal of Network Management》2003,13(2):115-127
This paper proposes a high‐performance connection management architecture to design a common QoS framework applied to an ATM network based on the Open Distributed Processing (ODP) concept. We design the QoS framework in accordance from the RM‐ODP information and computational viewpoints. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
45.
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
46.
Sang Cheol Lee Won Kook Lee 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,55(3):251-261
The extraction of penicillin G from simulated media was performed by water/oil/water (w/o/w) emulsion liquid membranes (ELMs) and studied under various operational conditions in a batch system. The degree of extraction achieved was between 80% and 95% under specific conditions. A concentration of greater than nine times the initial concentration of penicillin G in the external phase was obtained in the internal phase. The pH of the internal aqueous solution, containing a basic salt, was theoretically calculated on the basis of the amount of penicillin G transported into the internal phase. The calculated results agreed with the experimental data well and were used to select a suitable type and concentration of a basic salt in the internal phase to give a pH within the range 5 to 8 where penicillin G was stable after the termination of extraction. The extraction of penicillin G was successfully performed by the ELM process with sodium carbonate in the internal phase. 相似文献
47.
48.
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
49.
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
50.
Summary Cyclic tris(ethylene terephthalate) (CTET) was separated from oligomeric extract of poly(ethylene terephthalate) by the conventional solvent separation method. The structure of CTET was characterized by differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. It is shown that the double melting behavior of meltcrystallized CTET is attributed to the morphological change created by heat-treatment. The effect of the morphological change on the crystal structure of CTET was also examined. 相似文献