• Management Science and Financial Engineering
• /
• v.13 no.1
• /
• pp.93-113
• /
• 2007

In the previous research, we considered a logistics brokerage problem with the objective of minimizing total transportation lead time of freights in a logistics e-marketplace, in which a logistics brokerage agent intermediates empty vehicles and freights registered by car owners and shippers [7]. However, in the logistics e-marketplace, transportation due date tardiness is more important than the transportation lead time, since transportation service level is critically determined by whether the due date is met or not. Therefore, in this paper, we deal with the logistics brokerage problem with the objective of minimizing total tardiness of freights. Hungarian method based matching algorithms, real time matching(RTM), periodic matching(PM), and fixed matching(FM), are used for solving the problem considered in this paper. In order to test performance of the proposed algorithms, we perform computational experiments on a various problem instances. The results show that the waiting-and-matching algorithms, PM and FM, also give better performance than real time matching strategy, RTM, for the total tardiness minimization problem as the algorithms did for the total lead time minimization problem.

• Proceedings of the KSR Conference
• /
• 2003.10c
• /
• pp.377-382
• /
• 2003

In tread braking of freight cars, braking force is produced by the friction between the wheel and the braking shoe. Friction coefficients such as the brake power, weight variation and brake shoe types should be sensitively treated as the design parameters. The conditions of the car, empty and weighted, should also be taken into consideration in brake force design and the control of brake force has some limitations in terms of the brake system design so that the brake materials selection should be considered as important measures to solve that difficulties. Friction characteristics of brake materials should remain within the range of maximum and minimum value and the friction performance should remain stable regardless of braking time and temperature. This study presented an experimental evaluation method to secure optimum braking performance by keeping safe braking effect and braking distance by the friction coefficient of the brake shoe of the freight cars.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.10a
• /
• pp.295-301
• /
• 1997

본 연구의 목적은 수도권 전동차량의 주행성능을 평가하는 방법으로 진동성능을 비교검토하기 위하여 실차측정하고 분석한 것이다. 전동차량의 제작년도별로 측정대상차량을 샘플링하여 다양한 조건에서 진동을 측정하고 실측데이타를 시간영역의 통계적 방법으로 분석한 결과 제작년도에 따른 영향도 약간 나타났으며 전동차량의 2차 현가장치의 종류에 따른 영향을 발견할 수 있었다. 또한 측정선로구간의 특성에 따른 영향도 비교적 잘 나타나고 있음을 알 수 있었다.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.10
• /
• pp.77-83
• /
• 2008

In terms of saving costs, energy and materials, the weight of cars has been gradually reduced by optimizing design of structure, which also gives us good performance. In compliance with this, it should satisfy the lifetime of cars for 25 years under the operation. The purpose of this study is to evaluate the strength of fatigue using date from strain gauges attached carbody and bogie frame. This dynamic stress can be evaluated using S-N curve based on stress amplitude. Modified S-N curve by CORTON-DOLAN is used for more conservative and substantial evaluation. In addition, !he loadings itself of carbody and bogie frame are considered by calculating the rate of the differences which are occurred between empty car and fuiiy occupied car with passengers. Rainflow cycle counting method is applied to arrange the stress data for the modified S-N curve to predict lifetime of the materials. Conclusively the cumulative damages are not only calculated by Miner's Rule, but the safety factors are also determined by Goodman diagram.

• IE interfaces
• /
• v.23 no.2
• /
• pp.164-175
• /
• 2010

In logistics e-marketplaces, brokerage agents intermediate empty vehicles and freights registered by car owners and shippers. In the previous research, we proposed constant periodic/fixed matching algorithms for the logistics brokerage agents with the objective of minimizing the total transportation lead time and the transportation due date tardiness of freights(Jeong, 2004; Jeong, 2007). However, the constant type algorithms cannot consider changes in the balance status of an e-marketplace, i.e. the difference between the numbers of freights and vehicles to wait for matching, because they use non-changing matching periods and amounts. In this paper, we propose variable type algorithms for the logistics brokerage agent, in which the matching periods and amounts are changed continuously by considering the balance status between the freights and vehicles. In order to compare performance of the variable type algorithms to the previous constant type algorithms, we carried out computational experiments on various problem instances. The results show that the variable type algorithms give better performance than the constant type algorithms. We can expect that the logistics brokerage agents can improve their performance by using the proposed variable periodic/fixed matching algorithms.

• Journal of the Korean housing association
• /
• v.17 no.1
• /
• pp.47-58
• /
• 2006

The purpose of this study is to provide the information about improvement method of the detached housing area for children's outdoor activities. This study was accomplished by two research methods; the evaluation of physical environment of two detached housing areas, and the analyzation of satisfaction & consciousness of 190 residents. Outdoor spaces of detached housing area were divided into 6 areas (play space, education facility, commercial facility, green space, street space, and empty space & parking lot). And then, 6 outdoor spaces were evaluated about the physical characters such as accessibility, network, safety, variety, functional, natural elements. Also, the survey for resident's satisfaction and consciousness was used the Likert scale. According to the result of this study, many parts of the detached housing area were not good for children's outdoor activities, and the resident's satisfaction was low. In the sample detached housing areas, negative factors were car and motorcycle. And many residents pointed out the lack of natural elements, variety, and safety of outdoor space in dwelling area. Finally, this study suggested the several constitution method for the children's activities based on the results of evaluation and survey.

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2005.11a
• /
• pp.249-254
• /
• 2005

The purpose of this study is to provide the guideline of the outdoor space of residential land development district for children's outdoor activites. This study was accomplished by the valuation of the physical environment of 5 residential land development districts, the analyzation of behavioral mapping about children's outdoor activities, and the analyzation of satisfaction and the consciousness of 190 residents(parents) & 230 children. Especially, outdoor spaces were divided into 6 parts (play space, education facility, commercial facility, green space, and empty space & parking lot). And than, 6 outdoor spaces were valuated about the physical characters such as accessibility, network, safety, variety, functional, natural elements. Also, the survey for residents and children's consciousness were used the Likert scale. According to the result of this study, many parts of the housing area were not good for children's activities, and resident's satisfaction was low. In the sample areas, negative factors were car and motorcycle. And many residents were pointed out the lack of natural elements, variety, and safety of outdoor space in dwelling area. Finally, this study suggested the guideline children's activities based on the result of analyzation of valuation, behavioral mapping, and survey.

• Korean journal of applied entomology
• /
• v.17 no.3 s.36
• /
• pp.131-138
• /
• 1978

A virus named Cymbidium mild mosaic virus(Cy MMV), was mechanically transmitted to Chenopodium amaranticolor from the leaves of Cymbidium with mild mosaic symptoms. The virus was cultured in C. amaranticolor, in which it produced local chlorotic and ring spots, followed by systemic vein clearing with distortion. CyMMV infected 7 out of 35 species of plants. In C. amaranticolor juice infectivity was lost by heating at $90^{\circ}C$ for 10 miuntes, and by aging at$20^{\circ}C$ for 60 days, and by diluting at $10^{-6}$ when bioassayed on C. amaranticolor. CyMMV was not transmitted by Myzus persicae. The virus was purified after clarification of homogenized C. amaranticolor leaf tissues with chloroform, by differential centrifugation followed by sucrose density gradient centrifugation. Electron microscopic examination of purified preparation showed spherical particles of 28nm in diameter. The UV absorption spectrum of purified preparation was typical of u nucleoprotein (max. at 261nm. min. at 243nm), and showed 260/280=1.72 and max/min=1.26. The value of the sedimentation coefficient of the virus was S20.w=126. In gel-diffusion tests, CyMMV antiserum reacted with CarMV, but not with any of four other viruses (BBWV, CRSV, CMV, TBRV) having similar particles and properties in vitro. In ultra-thin sections of CyMMV infected tissues, a large number of virus particles were found in the cytoplasm of mesophyll cells and in xylem vessels.

• Korean Journal of Health Education and Promotion
• /
• v.19 no.1
• /
• pp.45-58
• /
• 2002

This research was conducted to understand and analyze the physical awareness symptoms of college students and get fundamental research data essential to provide efficient student guidance and public health service at schools. The survey was carried out for 1 month from May 7th, 2001 to June 7th, 2001. The interviewees were 950 enrolled students at junior colleges in Daegu. 26.5% of them were men and 73.5% women. Among the surveyed, public health majors were 76.9%. Daytime students were 64.1 %, and the majority of the students, 42.8%, were atheistic. 56.0% of the students grew up in big cities, 22.2% in medium and small-sized cities, and 21.8% in farming and fishing communities. 66.1 % used public transportation. The majority of the students, 48.7%, answered that the satisfaction level for their majors was average. The result shows that the ocular fatigue was indicated as a greatest complaint, and the female students showed the higher complaint rate than the males. In the study of the complaining rate of physical symptoms by major, the public health majors showed the highest complaining rate in gasping when going up/down stairs, shoulder pain, a burning feeling on empty stomach, and leg/knee pain. On the other hand, the highest complaint factors for the technical majors were ocular fatigue and the feelings of heavy head. In the study of the complaining rate of physical symptoms by transportation, gasping during going up/down stairs and shoulder pain were most common, which were 52.2% and 36.0% respectively. In the study of the insecurity response distribution by transportation, college students who drive a car showed 3.8% and students using public transportation 3.7%. In the study of the insecurity response by subject satisfaction, students who answered dissatisfactory were 8.3%, average 3.9%, satisfied 3.0%. Therefore, it was concluded that students who were dissatisfied with their subjects showed the higher rate of insecurity response. it can be recommended that a school health education program regarding ocular fatigue and shoulder pain should be developed.

• Journal of Environmental Science International
• /
• v.2 no.1
• /
• pp.73-81
• /
• 1993

Adsorption process using granular activated carbon(GAC) has been considered as one of the most effective water treatment technologies to remove humic acid which is recon- niEed as trihalomethane(THM) precursor in chlorination. To design the most effective GAC process, it is necessary to conduct the test of adsor- ption performance by means of isothem, batch rate and column studies and to select the most effective activated carbon according to raw materials of GAC - lignite and coconut shell. The objective of this study is to investigate the adsorption performance of humid acid on two activated carbons - lignite activated carbon(LAC) and coconut shell activated car- bon(CAC) made in Korea. It is available to represent UV-abs and trihalomethane formation potential(THMFP) as concentration of humic acid due to good relationship. The adsorption capacity of humid acid is not concerned with surface area of activated carbon but with pore size related to about $100{\AA}$, and then LAC forming at the extent of mesopore is found to be eight times more effective in adsorption capacity than CAC forming at micropore. The adsorption capacity of LAC and CAC is better at pH 5.5 than at pH 7. Pore and surface diffusion coefficients calculated from the diffusion model are $7.61\times10^{-13}m^2/sec$, $3.52\times10^{-15}m^2/sec$ for CAC, and $3.38\times10^{-12}m^2$/sec and $Ds=1.48{\times}10^{-15}m^2/sec$ for GAC respectively. From the results of column test it shows that the performance of LAC is also better than CAC and the optimal EBCT(Empty Bed Contact Time) is 4.52min. and activated carbon removes selectively the components of humic acid to be easily formed to THM.