• Journal of Nutrition and Health
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• v.31 no.8
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• pp.1347-1354
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• 1998

The purposes of this study were to : (a) anlayze wating time, service rate, arrival rate, and coustomer expectations/satisfaction in cafeteria business foodservices and (b) identify the differences in those factors between foodservices by menu managmenet systems. The samples were two business foodservices operated by contract management in Seoul. The queue, laptime , service rate, and arrival rate were measured at each foodservice by stopwatch observation. The menu type, delivery system, number of meals served , servide time, and turnover rate of each foodservic was investigated. Questionnaires were developed to survey customer expectations and satisfaction. Satistical data analysis was completed using the SAS package programs for descriptive analysis and t-test. The mean waiting time of island type dafeteria system with separte set -menu was shorter than that of the other. In both foodservices, arrival rates were not significantly different from one another , but sevice rates were significnatly high in dafeteria menu systems. The peak time of the queue was found out at combination set menu line. The separate set menu line had a higher servide rate than the combination set menu line. The mean waiting time of the island type cafeteria line was shorter than that of the straifth type . At the straight type dafeterial line, both arrival rate and service rate were higher than those of island-type. The results of this study suggested that a separate set-menu would be more desirable than a combination set-menu in case of providing set menu with cafeteria menu.

• KDI Journal of Economic Policy
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• v.39 no.2
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• pp.75-98
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• 2017

This paper aims to estimate the social discount rate (SDR) rather than dig into its theoretical foundation. As SDRs can be derived by investigating both the rate of return on investment and the social time preference rate, we estimate the marginal productivity of both private and public capital and the time preference rate based on the Euler equation. In order to provide a single representative SDR, the weighted averages of the marginal productivity and time preference rate, whose weights are determined by the flow of funds data reflecting the social demand of funds, are presented. Based on the empirical results, we argue that the marginal productivity of private capital stands in the middle of the 3% range while that of public capital varies from 4.5% to 8.6%, with the time preference rate showing a decreasing trend from 3.2% in the early 2000s to 1.2% by around 2030. The single representative SDR or the weighted SDR is estimated to be approximately 3.0~4.5% and expected to continue its downward trend for the foreseeable future.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.45 no.2
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• pp.77-84
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• 2009

This paper is to investigate the effect of the immersion time in the traditional hairtail hand line for developing the fishing methods and the fishing gear in the coast of jeju. The operating of 32 times was made with each different immersion time of hairtail hand line, and the relations between the catch and the immersion time were examined. As the result, targeted species rate was over 98% of total catch. From about 800 seconds after casting, the hooking rate was decreased and the bite loss rate was increased, it seems to be made by the decreasing factors of predators including the cutting of branch lines etc. In addition, it was supposed that the hooking rate and the bait loss rate had a deep connection with feeding time zone. The level of the correlation coefficient of the bait loss rate according to the immersion time was 0.54 at $p{\leq}0.01$, in the case of the hooking rate, 0.59 was chosen after about 800 seconds. The hooking rate and the bait loss rate according to the hook number were not irrelevant to the fish school layer. Additionally, it was assumed that the bait loss rate was related to the depth of water.

• Journal of the Korean Society of Safety
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• v.36 no.4
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• pp.47-53
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• 2021

The fatality rate is used to estimate each country's risk level. However, the fatality rate is calculated using the number of fatal accidents and workers, which is collected differently across countries. It is therefore problematic to use these numbers in an equivalent way. This study proposes a new approach for calculating the number of full-time equivalent workers when evaluating individual countries' fatality rate by suggesting an equivalent condition for the calculation of the number of full-time equivalent workers. This study proceeds in three steps: (i) analysis of the fatality rate among various countries; (ii) fatality rate calculation using the full-time equivalent workers; and (iii) comparison of the fatality rate among various countries. The study found that for the fatality rate based on national data, the fatality rate in South Korea (1.72‱) is 10 times higher than that in United Kingdom (0.17‱). However, according to the number of full-time equivalent workers, the fatality rate in South Korea (1.86‱) was three times higher than that in the United Kingdom (0.56‱). These findings reveal a difference in the fatality rate depending on the method used to calculate the number of full-time equivalent workers. Therefore, the number of full-time equivalent workers must be calculated for each country to accurately compare the fatality rate. Ultimately, the study's results highlight the need for clearer standards in the assessment of the fatality rate by country in international organizations such as the ILO.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.143-150
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• 2003

This study deals with the stress-strain-strain rate behaviour of overconsolidated clay. Consolidated-drained stress path tests were performed on the stress-time dependent condition. Stress history consists of rotation angle of stress path, overconsolidation ratio, and magnitude of length of recent stress path. Time history includes loading rate of recent and current stress path. Test results show that all influence factors have an increasing strain rate with time, and the strain rate varies with the change of the rotation angle of stress path. With the increase of overconsolidation ratio and loading rate of current stress path, the strain rate also increases. For the stress history, correlation between stress-strain and strain rate is indicated but the time history is not.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.115-120
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• 2005

This paper introduces models for preventive maintenance policies and considers periodic preventive maintenance policy with minimal repair when the failure of system occurs. It is assumed that minimal repairs do not change the failure rate of the system. The failure rate under prevention maintenance received an effect by a previously prevention maintenance and the slope of failure rate increases the model where it considered. Also the start point of failure rate under prevention maintenance considers the degradation of system and that it increases quotient, it assumed. Per unit time it bought an expectation cost from under this prevention maintenance policy. We obtain the optimal period time and the number for the periodic preventive maintenance by using Nakagawa's Algorithm, which minimizes the expected cost rate per unit time. Finally, it suppose that the failure time of a system has a Weibull distribution as an example and we obtain an expected cost rate per unit time the optimal period time and the number when cost of replacement and cost of minimal repair change.

• Journal of Korean Institute of Industrial Engineers
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• v.21 no.4
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• pp.507-517
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• 1995

The failure rate of an item depends on operational environment. When an item has a chance failure period and a wearout failure period in sequel, the severity of operational environment causes the increase in the slop of wearout failure rate or the increase in the magnitude of chance failure rate. For such a change of operational environment, this paper concerns the change of optimal preventive replacement time. Two preventive replacement policies, age replacement policy and periodic replacement policy with minimal repair, are considered. Investigated properties are: (a) in age replacement policy, optimal preventive replacement time increases as the chance failure rate increases and optimal preventive replacement time decreases as the slope of wearout failure rate increases, and (b) in periodic replacement policy with minimal repair, optimal preventive replacement time increases as the slope of wearout failure rate increases; however, the change of chance failure rate does not alter the optimal preventive replacement time.

• Journal of Mechanical Science and Technology
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• v.14 no.8
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• pp.851-860
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• 2000

Temperature field and cooling rate are important parameters to influence the properties of clad layer and the heat affected zone. In this paper the temperature field and cooling rate of laser cladding are studied by a two-dimensional time-dependent finite element model. Experiment has been carried out by Nd:YAG laser cladding with wire feeding. Research results indicate that at the beginning of cladding, the width and depth of melt pool increase with cladding time. The cooling rate is related to position, cladding time, cladding speed, and preheating temperature. The temperature near melt pool changes rapidly while the temperature far from melt pool changes slowly. With the increase of cladding time, cooling rate decreases. The further the distance from the melt pool, the lower the temperature and the slower the cooling rate. The faster the cladding speed, the faster the cooling rate. The higher the preheating temperature, the slower the cooling rate. The FEM results coincide well with the experiment results.

• International Journal of Highway Engineering
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• v.14 no.6
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• pp.131-138
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• 2012

PURPOSES : Two-lane highways have one lane in each direction, and lane changing and passing maneuvers take place in the opposing lane depending on the availability of passing sight distance. 2001 Korea Highway Capacity Manual (KHCM) is classified into two classes of two-lane highways (Type I, II), and average travel speed and time-delayed rate are used as measures of effectiveness (MOEs). However, since existing two-lane highways have both uninterrupted and interrupted traffic flow-system elements, a variety of free-flow speeds exhibits in two-lane highways. In addition, it is necessary to check if the linear-relationship between volumes and time-delayed rate is appropriate. Then, this study is to reestablish the relationship between average travel speed, time-delayed rate, and flow. METHODS : TWOPAS model was selected to conduct this study, and the free-flow speeds of passenger cars and the percentage of following vehicles observed in two-lane highways were applied to the model as the input. The revised relationships were developed from the computer simulation. RESULTS : In the revised average travel speed vs. flow relationship, the free-flow speed of 90km/h and 70km/h were added. It shows that the relationship between time delayed-rate and flow appeared to be appropriate with the log-function form and that there was no difference in time-delayed rate between the free flow speeds. In addition to revise the relationships, the speed prediction model and the time-delayed rate prediction model were also developed. CONCLUSIONS : The revised relationships between average travel speed, time-delayed rate, and flow would be useful in estimating the Level of Service(LOS) of a two-lane highway.

• Journal of Environmental Science International
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• v.6 no.3
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• pp.219-224
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• 1997

The cloging phenomenon in the fixed film reactor Is shown when biomass growth Is excessive for long operating time. In addition, effluent water Quality gets worse because of detachment of biomass. In this study, we conducted air-backwashing to sustain biomass In reactor to complement these defects. The results of experimental are showed In the following conclusion. The detachment rate was 19.5 - 38.0% when the organic loading rate was 0.40 - 1.32 kg COD/$m^3$/day, the k - backwashing Intensity was 2 L/min(6.7 $m^3$/$m^2$/hrl and the backwashing time was 15 - 19 seconds. And the detachment rate was 32.2 - 58.6 % when the organic loading rate was 1.37 - 2.27 kg COD/$m^2$/day, the backwashing time was 1 - 12 minutes. As orgnic loading rate and backwashing time ale Increased, detachment of fixed biomass Is Increased. The detachment equation with detachment rate(DR, %), backwashing time(BWT, min), fixed biomass concentration(FB. mg/L), and organic leading rate(OLR, kg COD/ms/day) through multiple linear regession was given by the following equation: DR : 17.964 $BWT^{0.1407} FB^{0.0597} OLR^{0.1946}$