• Journal of Korea Society of Industrial Information Systems
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• v.23 no.2
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• pp.29-39
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• 2018

In this paper, we discuss a discrete-time queueing system with dyadic server control policy that combines workload control and multiple vacations. Customers arrive at the system with Bernoulli arrival process. If there is no customer to serve in the system, an idle single server spends a vacation of discrete random variable V and returns. The server repeats the vacation until the total service time of waiting customers exceeds the predetermined workload threshold D. In this paper, we derived the steady-state workload distribution of a discrete-time queueing system which is operating under a more realistic and flexible server control policy. Mean workload is also derived as a performance measure. The results are basis for the analysis of system performance measures such as queue lengths, waiting time, and sojourn time.

• Proceedings of the Korean Society for Information Management Conference
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• 2003.08a
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• pp.355-364
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• 2003

20세기의 도서관은 확산된 인터넷의 보급으로 대출형 도서관의 연장선상에서 이용자의 요구에 따라 관종이나 지역간 협력을 통한 네트워크 운영으로의 도약을 꾀하고 있다. 이후, 도서관의 발전단계는 다양한 서비스를 즐기며 오랜 시간을 관내에 머무를 수 있는 체재형(滯在型)도서관이라고 표방되고 있다. 이는 도서관이 오랜 시간 머물며 다양한 활동이 가능한 공간으로 거듭나기를 바라는 사회적, 시대적 요청에 의한 결과라 할 수 있을 것이다. 이를 위하여 유니버설(universal) 디자인과 에콜로지(ecology) 디자인의 개념을 수용한 환경 친화적 도서관 건축에 대한 사안(私案)들을 제시하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1101-1109
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• 2004

Experimental measurements of flame structure and soot characteristics were performed fur ethene inverse diffusion flames (IDF). IDF has been considered as the excellent flow field to study the incipient soot because soot particle do not experience the oxidation process. In this study, LIF image clarified the reaction zone of IDF with OH signal and PAH distribution. laser light scattering technique also identified the being of soot particle. To address the degree of soot maturing, C/H ratio and morphology of soot sample were investigated. From these measurements, the effect of flow residence time and temperature on soot inception could be suggested, and more details on soot characteristic in the IDF was determined according to fuel dilution and flame condition. The fuel dilution results in a decrease of temperature and enhancement of residence time, but the critical dilution mole fraction is existed for temperature not to effect on soot growth. Also, the soot inception evolved on the specific temperature and its morphology are independent of the fuel dilution ratio of fuel.

• Journal of the Korea Society for Simulation
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• v.33 no.1
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• pp.19-26
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• 2024

The phase-type, PH, distribution is defined as the time to absorption into a terminal state in a continuous-time Markov chain. As the PH distribution includes family of exponential distributions, it has been widely used in stochastic models. Since the PH distribution is represented and generated by an initial probability vector and a generator matrix which is called the Markovian representation, we need to find a vector and a matrix that are consistent with given set of moments if we want simulate a PH distribution. In this paper, we propose an approach to simulate a PH distribution based on distribution function which can be obtained directly from moments. For the simulation of PH distribution of order 2, closed-form formula and streamlined procedures are given based on the Jordan decomposition and the minimal Laplace transform which is computationally more efficient than the moment matching methods for the Markovian representation. Our approach can be used more effectively than the Markovian representation in generating higher order PH distribution in queueing network simulation.

• Journal of the Korea Society for Simulation
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• v.24 no.3
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• pp.17-26
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• 2015

A cluster tool used in many kinds of semiconductor processes for improving the performance and the quality of wafers has a simple configuration, but its schedule is not easy because of its parallel processing module, a lack of intermediate buffers, and time constraints. While there have been many studies on its schedule, most of them have focused on full cycles in which identical work cycles are repeated under constant task times. In this research, we suggest strategies of start-up transient scheduling which satisfies time constraints and converges into a desirable steady schedule for full work cycle. The proposed schedules are expected robust under the stationary stochastic task times. Finally, we show that the strategies make schedules enters the desirable steady schedule and robust using the simulation.

• Korean Journal of Food Science and Technology
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• v.15 no.4
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• pp.392-398
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• 1983

A pilot single-screw food extruder was constructed, and its mechanical properties and product characteristics were investigated by using corn grits. The screw rotational speed was varied and the changes in temperature profile of the barrel for the start-up period of operation were measured. The rate of heat generation for the start-up period was affected by the screw speed and feed rate. The screw speed resulted in a great influence on the estimated dough viscosity. The changes in the dough viscosity could indicate the on-set of termoplastic reaction in the barrel. The expansion ratio during the start-up period mainly depended on the barrel temperature and the degree of thermoplastic reaction in the barrel. The barrel temperatures for the gelatinization and burning of corn grits depended on the screw speed as well as the feed rate.

• Journal of the Korean Chemical Society
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• v.20 no.5
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• pp.431-437
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• 1976

On the condition of adequate air supply, complete removal of carbon monoxide,occurred above $650^{\circ}C$. Using catalysts, the oxidation of carbon monoxide occurred at lower temperatures; on both $MnO_2 \;and\;30%\;MnO_2-70%\;CuO\;at\;250{\circ}C,\;on\;CuO\;at\;450{\circ}C,\;on\;50%\;MnO_2-50%\;CuO\;at\;200{\circ}C,\;and\;on\;70%\;MnO_2-30%\;CuO\;at\;180{\circ}C$. Manganese dioxide (p-type) showed higher activity than cupric oxide (n-type) and a catalyst consisting of 60% $MnO_2-40%$ CuO had the highest activity of all the $MnO_2$-CuO mixture. Over the range of transitional temperature, carbon monoxide removal efficiency decreased linearly with increasing inlet carbon monoxide concentration while temperature was fixed. Residence time of gases in the catalytic reactor, in the range of 0.9 to 1.8 seconds, gave no effect on carbon monoxide conversion.

• Journal of the Korea Society for Simulation
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• v.23 no.4
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• pp.9-19
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• 2014

The automotive industry has made much efforts to deliver finished vehicles to customers with speed and reliability. Decreasing the time a vehicle stays within an assembly plant from production release to shipment contributes to reduce the total order lead-time and consequently, the total transportation cost as well. Conventional shipment planning algorithms are limited in accommodating the dynamics of assembly plant operations as to finished vehicle shipment. This paper presents a market-based multi-agent shipment planning algorithm to optimize the performance of vehicle shipment process, capturing the operationally disruptive events. Experimental results using simulation show that the algorithm improves vehicle shipment performance with respect to lead time, labor efficiency, finished product quality, and transportation efficiency.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.165-168
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• 2003

본 연구에서는 마이크로파응용을 위한 이동통신기기용 안테나 모듈용 유전체재료 개발을 위해 $20\~80$의 중유전율을 가지는 글래스-세라믹스 복합체를 제조하고자 하였다. $BaO-Nd_2O_3-TiO_2$계 세라믹스를 기본조성으로 하고, $Na_2O-BaO-B_2O_3-P_2O_5$계 글래스 프릿의 첨가를 통해 제조된 글래스-세라믹스 복합체의 소결특성 및 유전특성을 조사하였다. 글래스 프릿을 5, 10, $15wt\%$ 첨가하였으며, $800\~950^{\circ}C$에서 각각 1시간동안 소결을 진행하였다. 그 결과로서 글래스 프릿의 한량이 증가하고, 소결온도가 높을수록 유전율$(\epsilon_r)$은 증가하였으며, 복합체의 결정특성은 감소함을 나타내었다.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.209-211
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• 2008

In this paper, a segregated finite element program for the analysis of an axisymmetric steady flow has been developed in order to investigate the flow inside an annular pipe with a periodic obstacle. For the verification of the developed code, a developing pipe flow has been solved and the solution is in a good agreement with the existing results. For the analysis of the flow inside an annular pipe with a periodic obstacle, three types of periodic obstacle are considered. From the present numerical analysis, various physical variables including flow pattern, pressure distribution and residence time are investigated as a preliminary study to the heat transfer analysis of an annular pipe flow with a periodic obstacle.