• Journal of Families and Better Life
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• v.19 no.1
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• pp.95-110
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• 2001

Recently a number of large discount store and those of its users was increasing. The purpose of this study is to investigate the tendency of impulse buying and analyzes factors which influence impulse buying. The data had been collected from questionaries with 474 consumers who visit large discount store. The major statistical methods used for data analysis are frequency, percentile, mean, t-test, multiple regression analysis, one-way ANOVA, and Duncans multiple range test utilizing SPSS Win pc+program. The results of this study are as follows : 1. The four different kind of impulse buying is measured. The overall level of impulse buying is 2.76. Suggestion impulse buying(M=3.19) is the highest, and the lowest is pure impulse buying(M=2.66). 2. In the area of demographic variables is significantly different in the age of twenties and thirties(p<.05). A visit frequency and membership. In the area of in-store variables is significantly different by all factors at impulse buying except waiting time. Especially, point-of-purchase(POP) advertisement and discount sale are very important variables. A visit frequency and membership are significantly different in the area of consumer-related variables. 3. Waiting time, a visit frequency, a POP advertisement, and a discount sale have the positive effects on overall impulse buying. Pure impulse buying is influenced by shopping list, POP advertisement and a stores atmospher. Buying companion, membership, kind of store and waiting time have the effect on reminder impulse buying. Suggestion impulse buying is influenced by school career, shopping list and POP advertisement. Planned impulse buying is influenced by sex, POP advertisement, buying companion and discount sale.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.2
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• pp.579-603
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• 2018

In this paper we propose a QoS-enhanced intelligent stochastic optimal fair real-time packet scheduler, QUEST, for 4G LTE traffic in routers. The objective of this research is to maximize the system QoS subject to the constraint that the processor utilization is kept nearly at 100 percent. The QUEST has following unique advantages. First, it solves the challenging problem of starvation for low priority process - buffered streaming video and TCP based; second, it solves the major bottleneck of the scheduler Earliest Deadline First's failure at heavy loads. Finally, QUEST offers the benefit of arbitrarily pre-programming the process utilization ratio.Three classes of multimedia 4G LTE QCI traffic, conversational voice, live streaming video, buffered streaming video and TCP based applications have been considered. We analyse two most important QoS metrics, packet loss rate (PLR) and mean waiting time. All claims are supported by discrete event and Monte Carlo simulations. The simulation results show that the QUEST scheduler outperforms current state-of-the-art benchmark schedulers. The proposed scheduler offers 37 percent improvement in PLR and 23 percent improvement in mean waiting time over the best competing current scheduler Accuracy-aware EDF.

• Environmental and Resource Economics Review
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• v.11 no.4
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• pp.659-687
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• 2002

This study used a discrete choice model to investigate an association between air pollution and hospital visits for acute respiratory symptoms with the national health interview survey conducted in 1998 in South Korea. The results showed that $NO_2$ and TSP were significantly related to hospital visits in a single-pollutant model, but when they were simultaneously considered, only $NO_2$ remained significant. It was estimated as $NO_2$ level increased by 10%(0.0027ppm) from 0.027ppm (the mean $NO_2$ level), hospital visits increase by 0.176%. This study also measured respondent's out-of-pocket expense and the time cost for commuting and waiting for the visit. We found that on the average, out-of-pocket expense is 5,600 won per hospital visit, but the total cost per hospital visit is measured at 33,440 won with time cost of commuting and waiting at 27,840 won. Time cost was over 63.6~83.3% of the total cost per hospital visit.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.7
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• pp.11-20
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• 1996

In this paper, the performance of the IeEE 802.4 token-passing is analyzed under the assumption that all nodes have finite buffers and finite THT (token tolding time). The loads generated at nodes are assumed to be asymmetric. The priority mechanism is not considered. This paper derives an approximate matrix equation of the queue length distributin in terms of the number of nodes, frame arrival rate and mean service time of a frame in steady state. Based on the matrix equation, the mean token rotation time, the mean waiting time and the blocking probability are derived analytically. the analytic results are compared with simulation results in order to show that the deviations are small.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.1
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• pp.110-122
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• 1993

When voice is transmitted through packet switching network, there needs a overload control, that is, a control for the congestion which lasts short periods and occurrs in local extents. In this thesis, we analyzed the performance of the statistical packet voice multiplexer using the overload control strategy by bit dropping. We assume that the voice is coded accordng to (4,2) embedded ADPCM and that the voice packet is generated and transmitted according to the procedures in the CCITT recomendation G. 764. For the performance analysis, we must model the superposed packet arrival process to the multiplexer as exactly as possible. It is well known that interarrival times of the packets are highly correlated and for this reason MMPP is more suited for the modelling in the viewpoint of accuracy. Hence the packet arrival process in modeled as MMPP and the matrix geometric method is used for the performance analysis. Performance analysis is similar to the MMPP IG II queueing system. But the overload control makes the service time distribution G dependent on system status or queue length in the multiplexer. Through the performance analysis we derived the probability generating function for the queue length and using this we derived the mean and standard deviation of the queue length and waiting time. The numerical results are verified through the simulation and the results show that the values embedded in the departure times and that in the arbitrary times are almost the same. Results also show bit dropping reduces the mean and the variation of the queue length and those of the waiting time.

• Journal of the Korean Statistical Society
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• v.30 no.4
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• pp.661-666
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• 2001

In this paper we consider an M/G/1 queue where the server of the system has a vacation time and the service policy is limited-1. In this system, upon termination of a vacation the server returns to the queue and serves at most one message in the queue before taking another vacation. We consider two models. In the first, if the sever finds the queue empty at the end of a cacation, then the sever immediately takes another vacation. In the second model, if no message have arrived during a vacation, the sever waits for the first arrival to serve. The analysis of this system is particularly useful for a priority class polling system. We derive Laplace-Stieltjes transforms of the waiting time for both models, and compare their mean waiting times.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.3
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• pp.277-287
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• 1992

In this paper, we study the performance eualuations of the FDDI Network, by mathmeticlal analysis and simulation, in which the Integrated Voice/Data transmission system with voice traffic in synchronous mode and data traffic inasynchronous mode.For the mean waiting times of Voice/Data packet, we use two-state of Marcov models for voice traffic with talkspurt and silenci state, and the data traffic would traffic would transmit at the silence state of voice traffic. By the mean wating times, we analyze the relations between synchronous and asynchronous mode. As a result, using Sync/Async mode with voice and data, voice was not under influnece of data traffic. and in the same time,data can be tanaxmitted in a short waiting time, too.

• The KIPS Transactions:PartA
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• v.9A no.4
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• pp.547-554
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• 2002

This paper proposes an efficient dynamic routing algorithm for Multistage Bus Networks(MBN's) in distributed shared memory environment. Our algorithm utilizes extra paths available on MBN and determines routing paths adaptively according to switch traffic in order to distribute traffic among switches. Precisely, a packet is transmitted to the next switch on an extra path having a lighter traffic. As a consequence the proposed algorithm reduces the mean response time and the average number of waiting tasks. The results of simulations, carried out with varying numbers of processors and varying switch sizes, show that the proposed algorithm improves the mean response time by 9% and the average number of waiting tasks by 21.6%, compared to the existing routing algorithms which do not consider extra paths on MBN.

• Clinics in Shoulder and Elbow
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• v.25 no.2
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• pp.121-128
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• 2022

Background: To determine the reasons and factors that contribute to the cancellations of shoulder surgeries at a tertiary referral center and to analyze the characteristics of these patients. Methods: Patients scheduled for shoulder surgery from June 2017 to July 2019 were allocated to a surgery group (n=224) or a cancellation group (n=96). These groups were compared with respect to patient characteristics, types of surgery, distance from patient's home to the hospital, traveling time to the hospital, and waiting period before surgery. Reasons for cancellation and responses were acquired using a telephone interview and were subsequently analyzed. Results: The cancellation group was older, had a less frequent history of trauma, and had a lower proportion of patients undergoing arthroscopic rotator cuff repair than the surgery group (p=0.009, p=0.014, and p=0.017, respectively). In addition, mean distance from the patients' homes to the hospital and preoperative waiting time were both longer in the cancellation group (p=0.001 and p<0.01, respectively). The most common reason given for cancellation was another medical condition (28.1%). Conclusions: Older age, need for arthroscopic rotator cuff repair surgery, longer distance from the patient's home to the hospital, and longer waiting period significantly increased the chance of cancellation. The main reason for canceling surgery was a concurrent medical condition. Therefore, identification of other medical conditions in advance is an important consideration when surgeons recommend shoulder surgery to patients. Surgeons should also consider patient's age, type of surgery, distance from the hospital, and waiting time when assessing the possibility of surgery cancellation.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.4
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• pp.53-60
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• 2022

In a group-testing method, instead of testing a sample, for example, blood individually, a batch of samples are pooled and tested simultaneously. If the pooled test is positive (or defective), each sample is tested individually. However, if negative (or good), the test is terminated at one pooled test because all samples in the batch are negative. This paper considers a queueing system with a two-stage group-testing policy. Samples arrive at the system according to a Poisson process. The system has a single server which starts a two-stage group test in a batch whenever the number of samples in the system reaches exactly a predetermined size. In the first stage, samples are pooled and tested simultaneously. If the pooled test is negative, the test is terminated. However, if positive, the samples are divided into two equally sized subgroups and each subgroup is applied to a group test in the second stage, respectively. The server performs pooled tests and individual tests sequentially. The testing time of a sample and a batch follow general distributions, respectively. In this paper, we derive the steady-state probability generating function of the system size at an arbitrary time, applying a bulk queuing model. In addition, we present queuing performance metrics such as the offered load, output rate, allowable input rate, and mean waiting time. In numerical examples with various prevalence rates, we show that the second-stage group-testing system can be more efficient than a one-stage group-testing system or an individual-testing system in terms of the allowable input rates and the waiting time. The two-stage group-testing system considered in this paper is very simple, so it is expected to be applicable in the field of COVID-19.