• Journal of the Korean Statistical Society
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• v.31 no.4
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• pp.491-507
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• 2002

We analyze a single server bulk input queue with optional server vacations under a single vacation policy and balking phenomenon. The service times of the customers as well as the vacation times of the server have been assumed to be arbitrary (general). We further assume that not all arriving batches join the system during server's vacation periods. The supplementary variable technique is employed to obtain time-dependent probability generating functions of the queue size as well as the system size in terms of their Laplace transforms. For the steady state, we obtain probability generating functions of the queue size as well as the system size, the expected number of customers and the expected waiting time of the customers in the queue as well as the system, all in explicit and closed forms. Some special cases are discussed and some known results have been derived.

• Health Policy and Management
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• v.19 no.3
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• pp.109-124
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• 2009

Background: This study aimed to examine whether cases of punishing false claimants threat general physicians to check their medical cost claims with care to avoid being suspected, and identify empirically general deterrence effects of the on-site investigation system in the Korean National Health Insurance. Methods: 800 clinics were selected among a total of 15,443 clinics that had no experience of on-site investigation until June 2007 using a stratified proportional systematic sampling method. We conducted logistic multiple regression to examine the association between factors related to provider's perception of on-site investigation and high level of perceived deterrence referring to fear of punishment after adjusting provider's service experiences and general characteristics. Results: The probability of high perceived deterrence was higher 1.7 times (CI: 1.13-2.56), 2.73 times (CI: 1.68-4.45) each among clinics exchanging the information once or more per year or once or more for 2-3 months than among clinics no exchanging the information about on-site investigation. Also, the probability of high perceived deterrence was higher 2.27 times (CI: 1.28-4.45) among clinics that knows more than 3 health care institutions having experienced an on-site investigation than among clinics knowing no case. Conclusion: A clinic knowing more punishment cases by onsite investigation and exchanging more frequently information about on-site investigation is likely to present high perceived deterrence. This result will provide important information to enlarge preventive effects of on-site investigation on fraud and abuse claims.

• Korean Journal of Occupational Health Nursing
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• v.23 no.2
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• pp.89-96
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• 2014

Purpose: The purpose of this study is to discover the influence of the working conditions on women workers' occupational stress. Methods: Descriptive method is used to identify women's stress depending on their general working features and conditions by conducting a survey of them in women-dominated service industries. SPSS 18.0 program is used for data analysis and descriptive statistics is presented with standard deviation, frequency and percentage. ${\chi}^2$-test is used as an analysis tool. To figure out factors that influence their stress, logistic regression analysis is used for general features and working conditions as independent variables, and occupational stress as a dependent variable. Results: As a result, among the independent variables, employment status, weekly working hours, career, shiftwork, and work-family-balance are meaningful factors that influence their stress. Temporary workers' stress is 3.65 times higher (p<.001), and workers working over 48 hours a week have 1.97 times higher stress (p<.003). Workers with over 5 years' career are under 1.73 times higher stress (p<.046) and shift workers are under 3.51 times higher stress (p<.001). Work family balance results in 1.93 times higher stress (p<.009). Conclusion: It is necessary to seek how to prevent and manage women workers' stress considering features.

• Management Science and Financial Engineering
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• v.14 no.1
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• pp.23-34
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• 2008

In this study, we consider stationary waiting times in a Poisson driven single-server m-node queues in series. We assume that service times at nodes are independent, and are either deterministic or non-overlapped. Each node excluding the first node has a finite waiting line and every node is operated under a FIFO service discipline and a communication blocking policy (blocking before service). By applying (max, +)-algebra to a corresponding stochastic event graph, a special case of timed Petri nets, we derive the explicit expressions for stationary waiting times at all areas, which are functions of finite buffer capacities. These expressions allow us to compute the performance measures of interest such as mean, higher moments, or tail probability of waiting time. Moreover, as applications of these results, we introduce optimization problems which determine either the biggest arrival rate or the smallest buffer capacities satisfying probabilistic constraints on waiting times. These results can be also applied to bounds of waiting times in more general systems. Numerical examples are also provided.

• Journal of information and communication convergence engineering
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• v.19 no.4
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• pp.257-262
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• 2021

Providing web services to users has become expensive in recent times. For better web services, a web server is provided with high-performance technology. To achieve great web service experiences, tools such as general-purpose graphics processing units (GPGPUs), artificial intelligence, high-performance computing, and three-dimensional simulation are widely used. However, graphics processing units (GPUs) are used in high-speed operations and have limited general applications. In this study, we developed a task queue in a GPU to improve the performance of a web service using a multiprocessor and studied how to receive and process user requests in bulk. We propose the use of a GPGPU-based task queue to process user requests more than GPGPU based a central processing unit thread, and to process more GPU threads on task queue at about 136% to 233%, and proved that the proposed method is effective for web service.

• The Korean Journal of Food And Nutrition
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• v.18 no.3
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• pp.175-191
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• 2005

This study carried out a survey of students in Gangwon province's general opinion and satisfaction with the school food-service programs implemented in Gangwon province. The method involved a survey of 1,500 elementary, middle, and high school students from 30 schools. The main results of this study can be summarized as follows: With regards to their general opinion of the school food-service programs, $70\%$ of the students answered that the size of the portions was appropriate. Moreover, the survey students answered that they were satisfied with the current method in which the food services. The elementary school students were found to be the best at maintaining public order when the food services were being conducted. The largest complaint which the students had towards these food service programs was the taste of the food itself. With regard to the students' degree of satisfaction with the school food service programs, the highest level of satisfaction with the atmosphere during meal times(3.88), followed by the degree of satisfaction with the food(3.27), and the school cafeteria environment(3.20), and the sanitary conditions of the food service facilities(3.14). The overall opinion and degree of satisfaction with school food service programs demonstrated significant differences, depending on the school level and type of food service.

• Journal of the Korea Society for Simulation
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• v.28 no.3
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• pp.65-74
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• 2019

For many years, it has been widely studied on fork-join production systems but there is not much literature focusing on the finite buffer(s) of either individuals or shared, and generally distributed processing times. Usually, it is difficult to handle finite buffer(s) through a standard queueing theoretical approach. In this study, by using the max-plus algebraic approach we studied buffer-shared fork-join production systems with general processing times. However, because it cannot provide proper computational ways for performance measures, we developed simulation models using @RISK software and the expressions derived from max-plus algebra. From the simulation experiments, we compared some properties on waiting time with respect to a buffer capacity under two blocking policies: BBS (Blocking Before Service) and BAS (Blocking After Service).

• Journal of the Korean Home Economics Association
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• v.43 no.11 s.213
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• pp.127-140
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• 2005

Sanitary management performance and knowledge of employees in hospital food service was evaluated by survey questionnaire to improve their sanitary management performance, analyse the weak points of sanitary management, and determine more practical and efficient alternatives of sanitation education. For this study, we selected 6 dieticians and 250 employees working in the six general hospitals larger than 400 beds in Gyeonggi and Incheon area. The questionnaire consisted of three parts: general subjects in the nutrition division of hospitals, sanitation education of dieticians, and sanitary management performance and knowledge of employees. The average ratio of HACCP related equipment and facilities of the target hospitals was relatively high at $86.5\%$. The number of sanitation education was 1.99 times/month by regular schedule and 6.47 times/month by occasional schedule. The average dietician's inspection time of cooking was 178.77 minutes/day. The average point of sanitary management performance was 4.62/5.0, showing a relatively high grade. In each region of sanitary management performance, food treatment sanitation was marked with the highest point, at 4.85, fellowed by cleaning and sterilizing sanitation at 4.65, personnel sanitation at 4.61 point and device and utensil sanitation was ranked with the lowest point at 4.53. Sanitary management performance was affected by the number of occasional education which was highest at 6-10times/month. The mean score of sanitary knowledge was 11.17/15.0. The assigned position, type of employment, status, working career and number of occasional education affected the mean score of sanitary knowledge of employees significantly. Sanitary knowledge of employees was highest in the case that occasional education was peformed at 6-10 times/month. There was no correlation between the sanitary management performance and sanitary knowledge of employees. In contrast, there were correlations between sanitary management performance and dietician's inspection time of cooking and number of employees.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.119-129
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• 2019

Although line production systems with finite buffers have been studied over several decades, except for some special cases there are no explicit expressions for system performances such as waiting times(or response time) and blocking probability. Recently, a max-plus algebraic approach for buffer-sharing systems with constant processing times was introduced and it can lead to analytic expressions for (higher) moment and tail probability of stationary waiting. Theoretically this approach can be applied to general processing times, but it cannot give a proper way for computing performance measures. To this end, in this study we developed simulation models using @RISK software and the expressions derived from max-plus algebra, and computed and compared blocking probability, waiting time (or response time) with respect to two blocking policies: communication(BBS: Blocking Before Service) and production(BAS: Blocking After Service). Moreover, an optimization problem which determines the minimum shared-buffer capacity satisfying a predetermined QoS(quality of service) is also considered.

• Environmental Analysis Health and Toxicology
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• v.27
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• pp.2.1-2.4
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• 2012

Objectives: This study is a cross-sectional study to investigate the frequency of humidifier and humidifier disinfectant usage in the general population. Methods: A questionnaire was applied to 94 subjects (46 male, 48 female) from the general population of Gyeonggi Province. The questionnaire consisted of 3 scales (general characteristics, 5 items about humidifier usage, 5 items about humidifier disinfectant usage). Results: Thirty-five (37.2%) of the 94 subjects use a humidifier and humidifier disinfectant usage was found to be 18.1%. The frequency of humidifier usage is 4.8 times per a week and the humidifier disinfectant usage is 2.4 times per a week. Humidifier usage rate was highest in January. and then tended to rise gradually from October. Conclusions: Although this study population was not representative, we can say that approximately 50 percent of the humidifier users use a humidifier disinfectant and the trend of using a humidifier has shown seasonality.