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21.
Hyun-Moo Hur Joon-Hyuk Park Won-Hee You Tae-Won Park 《Journal of Mechanical Science and Technology》2009,23(10):2790-2800
A study was conducted to analyze the influence of wheel profile wear on running stability by using a 1/5 scale bogie model.
The critical speed was analyzed by constructing a dynamic model for the bogie model. And the 1/5 scale bogie and a scaled
roller rig prototype were manufactured to verify the feasibility of applying the scale model; a critical speed test was conducted
for worn wheel profile samples. The test results for the scale model were consistent with the simulation results for the scale
model within the range of 5% or less. Also, the variation of the critical speed of the scale model for the wheel profile wear
shows a similar trend with the analysis results of the full scale model. Therefore, using the scale model to analyze the influence
of wheel profile wear on running stability shows sufficient feasibility as a model to analyze the stability of a full scale
bogie. 相似文献
22.
A Distributed Medium Access Control (D-MAC) protocol based on UWB for high-rate Wireless Personal Area Networks is specified by the WiMedia Alliance. D-MAC protocol is suitable for ubiquitous connection in home networks, military/medical applications due to its inexpensive cost, low power consumption, high data rate, and distributed approach. In contrast to IEEE 802.15.3, D-MAC makes all devices have the same functionality. And its networks are self-organized and provide devices with functions such as access to the medium, channel allocation to devices, data transmission, quality of service and synchronization in a distributed manner. D-MAC fundamentally removes the problems of the centralized MAC approach revealed at IEEE 802.15.3 MAC by adopting a distributed architecture. However, the current D-MAC can’t prevent QoS degradations, occurred by mobile nodes with low data rate due to bad channel status, which cause critical problems in QoS provisioning to isochronous streams and mobile applications. Therefore, we propose a distributed cooperative MAC protocol for multi-hop WiMedia networks using virtual MIMO links. Based on instantaneous Channel State Information among WiMedia devices, our proposed protocol can intelligently select the transmission path with higher data rate to provide advanced QoS with minimum delay for real-time multimedia streaming services. 相似文献
23.
Gyu-Hong Kang Young-Dae Son Gyu-Tak Kim Jin Hur 《Industry Applications, IEEE Transactions on》2009,45(1):161-167
This paper presents a novel design method to reduce the cogging torque of interior-type permanent-magnet (PM) motor. In the design method, the optimal notches are put on the rotor pole face, which have an effect on the variation of PM shape or the residual flux density of PM. Through the space harmonic field analysis, the positions of notches are found, and the optimal shapes of notches are determined by using finite element method. The validity of the proposed method is confirmed by experiments. 相似文献
24.
Management of foreign exchange risk is considered to be as important as trading results in firm performance when international trading and transaction of different kind of currencies are getting popular. Most previous researches on this issue have been based on the foreign exchange market and financial investing and accounting, focusing on theoretical point of view. And it is difficult to apply these research results to each company, since all companies in industry have different financial circumstances. In this paper, the solution for the foreign exchange management is proposed using GA and VaR which is very practical to export-oriented companies. The developed software enables a user to specify the criteria for the foreign exchange trading condition, constraints on dealing amount, GA operator and penalty, and variables in VaR. This approach is useful for managing foreign exchange holdings of a company in a practical way, analyzing past exchange rate trend with dealing results. 相似文献
25.
Jungkeuk Park Kwangbeom Hur Sanggyu Rhim Ho Kang 《Korean Journal of Chemical Engineering》2011,28(1):126-132
Biogas usually contains CH4 and CO2 as main components with the ratio of 6: 4, and its composition varies with wide range depending on digester conditions. In addition to concentration change of each constituent, biogas composition could be changed due to the variations in the organic matter treatment process. The aim of the study is to analyze the production and application to a microturbine system of CH4/N2 rich biogas produced from Gong-Ju wastewater treatment plant. CH4/N2 rich biogas is produced due to the internal wastewater recirculation. The internal wastewater recirculation is intended to enhance NO3 ? removal without additional carbon source input. As a result, the digester was shown to be the highest contributor for nitrogen removal and average CH4 concentration was lowered compared to the typical biogas composition. Nitrate removal rate was influenced by the internal recirculation ratio. Content of N2 has no effect on biogas clean-up system performance. Besides, adaptability of CH4/N2 rich biogas to microturbine was satisfactory with very low NOx and SO2 concentration in microturbine exhaust gas. Influence of high N2 concentration of biogas on NOx concentration was limited due to the low combustion temperature. 相似文献
26.
Quality characteristics of imitation crab sticks made from Alaska Pollack and spent laying hen meat 总被引:1,自引:0,他引:1
Imitation crab stick (ICS) samples were divided into four treatments, a control (C) prepared with Alaska Pollack as a commercial ICS, T1, which consisted of Alaska Pollack with spent laying hen surimi collected by the pH adjust method, T2, which was composed of Alaska Pollack with spent laying hen surimi collected by the filter cake method, and T3, which consisted of Alaska Pollack with whole spent laying hen meat batter collected by the cutting method. The moisture content was significantly higher in T3 than in the other ICS samples; but, there was no significant difference in the crude protein, fat and ash content, regardless of the spent laying hen substitution methods. The lightness (L∗) and whiteness (W) was higher in the control than in the other ICS samples at 0 days of storage, whereas the yellowness (b∗) was significantly higher in T3 than in the other ICS samples. The level of polyunsaturated fatty acids was significantly higher in the control group than in the other ICS samples. Additionally, the pH increased with storage time in the spent laying hen substituted samples (T1, T2 and T3), with T1 showing a significantly higher pH during storage. The TBARS value increased with storage time in all ICS samples, with T2 showing a significantly lower TBARS value than the other ICS samples at the beginning and end of the storage periods. There was no significant difference in any sensory evaluation items among the ICS samples during storage. Thus, we assumed that T3 was better than other ICS samples, because T3 method (cutting) is much easier to collect spent laying hen surimi than T1 (pH adjust) and T2 (filter cake). 相似文献
27.
The independence of processes in queueing systems is generally assumed when developing queueing models. However, real systems often involve several process dependencies, and failure to take these into consideration can lead to serious underestimation of the performance measures. We consider herein a single server queueing system with a Markov renewal process (MRP) for its arrival process and a general service time distribution, and derive the distribution function and correlation coefficient of the departure process. Since the departure process also often corresponds to an arrival process in downstream queues, the results obtained here can be used to derive a better approximation of the performance measures of a non-product form general queueing network. 相似文献
28.
Dietary conjugated linoleic acid (CLA) treatment reduced color a*- and b*-values of cooked chicken breast rolls. Sensory panels rated the color of cooked chicken rolls with CLA treatments darker than the control. The production of carbon monoxide (CO) in cooked chicken rolls increased dramatically after irradiation and was correlated with the increased redness of cooked chicken rolls after irradiation. Consumer test indicated that the color of cooked chicken rolls after irradiation was preferred to the nonirradiated, but no preference for the color among the three CLA treatments was found. Irradiation greatly increased volatile production and induced a metallic off-flavor in chicken rolls. Sensory evaluation indicated that the hardness of chicken rolls increased and juiciness decreased as the dietary level of CLA increased. 相似文献
29.
As pervasive computing is widely adopted and reliable networks are becoming more easily accessible, there is a rapidly growing need to develop a mechanism to analyze and evaluate the performance of ubiquitous environments. This paper presents an information processing model which characterizes a ubiquitous environment where a variety of pieces of information need to be exchanged among devices within a system. The proposed model not only provides analytical tools to evaluate the performance of devices, but also makes it possible to identify key factors in designing a ubiquitous environment. For illustrative purposes, a test bed is constructed and the performance of the system is assessed based on the proposed model. 相似文献
30.
In this paper, a PCS (power conditioner system) design for a fuel cell generation system has been proposed. In order to analyze the dynamic performance of the PCS, a fuel cell stack simulator is also designed, which can consider the dynamic V–I characteristics of the PEMFC (proton exchange membrane fuel cell). First, we explain the PCS design for a fuel cell generation system in detail along with the system configuration and operational principle of the developed PEMFC simulator that has been investigated. In addition, we cover the validity of the proposed system that has been verified by informative simulation and experimental results. 相似文献