• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.84-90
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• 2018

When producing a plastic horn cover for an automobile, since the interval between the ribs on the inner surface is narrow, conventional cooling channels cannot be applied and cooling of the mold is difficult. For this reason, the molding operation cannot be completed within a set cycle time. In this study, a conformal cooling channel was applied on the mold to solve the cooling problem. Injection molding simulation was carried out to confirm the effectiveness of the conformal cooling channel. In the analysis results, the mold temperature at the rib section decreased by 33%, and the mold temperature also decreased by 31%. This reduction in temperature allowed for molding within a set cycle time and demonstrated the effectiveness of the conformal cooling channel.

• Journal of the Korea Convergence Society
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• v.9 no.7
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• pp.223-230
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• 2018

In the case of a one-shot logistic equipment system that has been stored for a long time, reliability changes with the passage of time. Therefore, when the time comes to use, the storage reliability of the product is an important quality characteristic, and the existing studies have focused on the research for calculating the optimal period inspection cycle to improve the storage reliability. In this study, we analyzed the influence of the two factors on the storage reliability at the convergence point by analyzing the design reliability as well as the periodic inspection cycle. To do this, we applied the existing Martinez storage reliability model to the missile, a representative product of a one-shot system, and analyzed the quantitative effects of the design reliability and the periodic inspection cycle. From the results of the analysis, it was confirmed that the maintenance of the periodic inspection cycle is more important for the improvement of the storage reliability than the design reliability in the design reliability category of the current product.

• Advances in Energy Research
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• v.4 no.1
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• pp.29-45
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• 2016

There has been a growing interest in the recent time for the development of solar power tower plants, which are mainly used for utility scale power generation. Combined heat and power (CHP) is an efficient and clean approach to generate electric power and useful thermal energy from a single heat source. The waste heat from the topping Brayton cycle is utilized in the bottoming HRSG cycle for driving steam turbine and also to produce process steam so that efficiency of the cycle is increased. A thermal storage system is likely to add greater reliability to such plants, providing power even during non-peak sunshine hours. This paper presents a conceptual configuration of a solar power tower combined heat and power plant with a topping air Brayton cycle. A simple downstream Rankine cycle with a heat recovery steam generator (HRSG) and a process heater have been considered for integration with the solar Brayton cycle. The conventional GT combustion chamber is replaced with a solar receiver. The combined cycle has been analyzed using energy as well as exergy methods for a range of pressure ratio across the GT block. From the thermodynamic analysis, it is found that such an integrated system would give a maximum total power (2.37 MW) at a much lower pressure ratio (5) with an overall efficiency exceeding 27%. The solar receiver and heliostats are the main components responsible for exergy destruction. However, exergetic performance of the components is found to improve at higher pressure ratio of the GT block.

• The Korean Journal of Food And Nutrition
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• v.25 no.1
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• pp.205-213
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• 2012

This study investigated the life cycle of menus and made suggestions on the appropriate time for when new menus should be developed. For this purpose, a total of 636 customers who visited 'T' Restaurant more than 25 times in the past three years were used for analysis. After estimating product life cycles based on sales and selling period, an empirical study was conducted. In terms of product life cycle, a growth stage was observed in the category of pasta and pizza in both stores A and B, whereas sales in the rice category stayed constant. Regarding trend in seasonal sales, a big difference was detected between the two stores. While store A was already in the decline stage of the life cycle in all menu categories, store B remained in the growth stage. In terms of menu life cycle, the product life cycle of long-lived products was observed in the pasta category in both stores A and B. While the pizza category was in the growth stage, the product life cycle of long-lived products was observed in the rice category. It is expected that the results of this study could be useful in development of new menus and product life cycle management to fulfill diverse customer needs in the dining-out business.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.584-589
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• 2006

In this paper, a test apparatus for reliability evaluation of a rotary compressor has been suggested with a short-cycle concept. $CO_2$ refrigerant is adopted for this cycle to avoid phase change during cycle operation. Evaporator is not necessary in short-cycle. Utilizing a short-cycle, the test apparatus was built on the purpose of evaluating the reliability of each rotary compressor on the conveyer belt of the factory. The primary validation of the test apparatus is discussed by analyzing the experimental heat balance data. Additional validation was performed through the overload continuous operation test where the wear rate of the $CO_2$ short-cycle was found to similar to that of the R22 normal-cycle. The reliability evaluation test apparatus with a short-cycle in present investigation was found simple and efficient in the view of reducing sample numbers, costs, and test time in analyzing the reliability of rotary compressors.

• Industrial Engineering and Management Systems
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• v.12 no.4
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• pp.359-367
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• 2013

The amount of international trade is rapidly increasing as a result of globalization. It is well known that as the size of a vessel becomes larger, the transportation cost per container decreases. That is, the economy-of-scale holds even in maritime container transportation. As a result, the sizes of containerships have been steadily increased for reducing transportation costs. In addition, various handling technologies and handling equipment have been introduced to increase the throughput capacities of container terminals. Quay crane (QC) that carries out load/unload operations plays the most important role among various handling equipment in terminals. Two typical examples of advanced QC concepts proposed so far are double trolley QC and supertainer QC. This paper suggests a method of estimating the expected value and the standard deviation of the container handling cycle time of the advanced QCs that involve several handling components which move at the same time. Numerical results obtained by the proposed estimation procedure are compared with those obtained by simulation studies. In order to demonstrate the advantage of advanced QCs, we compared their expected cycle times with those of a conventional QC.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.2
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• pp.49-54
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• 2005

This Paper Presents a non-blocking deadlock detection scheme with immediate cycle detection in multiprocessing systems. We assume an expedient state and a special case where each type of resource has one unit and each request is limited to one resource unit at a time. Unlike the previous deadlock detection schemes, this new method takes O(1) time for detecting a cycle and O(n+m) time for blocking or handling resource release where n and m are the number of processes and that of resources in the system. The deadlock detection latency is thus minimized and is constant regardless of n and m. However, in a multiprocessing system, the operating system can handle the blocking or release on-the-fly running on a separate processor, thus not interfering with user process execution. To some applications where deadlock is concerned, a predictable and zero-latency deadlock detection scheme could be very useful.

• Journal of Society of Preventive Korean Medicine
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• v.14 no.2
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• pp.105-120
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• 2010

Objectives : This study aims to evaluate the effects of expiration-to-inspiration time ratio (E/I-ratio) on heart rate, which represents cardiac autonomic function, and cold-heat in the healthy people. Methods : 49 healthy young volunteers(male : female = 32 : 17) were recruited in the study. The participants completed the questionnaire for yin-yang pattern identification and then we measured the chest plethysmogram for respiration signal and the electrocardiogram for NN intervals during different E/I-ratio from 1 to 2. We compared heart rate variability including RMS-SD, VLF, LF and HF, and the trend-cycle factors decomposed from NN interval data by time series analysis among the respective E/I-ratio. We also confirmed the difference on the trend-cycle factors according to the score of the questionnaire for cold and heat pattern identification. Results : There were differences on the trend-cycle factors from NN interval data, but no significant difference on heart rate variability, among the respective E/I-ratio. We also found significant relationship between the trend-cycle factors and the heat pattern identification scores. Conclusions : The results indicate that cardiac autonomic function can be modulated by the E/I-ratio and the modulation will be slower and more tendencious than respiratory sinus arrhythmia.

• International Journal of Highway Engineering
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• v.17 no.5
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• pp.93-103
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• 2015

PURPOSES : The purpose of this study is to present a linear programing optimization model for the design of lane-based lane-uses and signal timings for an isolated intersection. METHODS: For the optimization model, a set of constraints for lane-uses and signal settings are identified to ensure feasibility and safety of traffic flow. Three types of objective functions are introduced for optimizing lane-uses and signal operation, including 1) flow ratio minimization of a dual-ring signal control system, 2) cycle length minimization, and 3) capacity maximization. RESULTS : The three types of model were evaluated in terms of minimizing delay time. From the experimental results, the flow ratio minimization model proved to be more effective in reducing delay time than cycle length minimization and capacity maximization models and provided reasonable cycle lengths located between those of other two models. CONCLUSIONS : It was concluded that the flow ratio minimization objective function is the proper one to implement for lane-uses and signal settings optimization to reduce delay time for signalized intersections.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.4
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• pp.281-286
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• 2011

The objective of this study is to optimize the four-bed six-step pressure swing adsorption(PSA) process for high purity $CH_4$ recovery from the biogas. The effects of P/F(purge to feed) ratio and cycle time on the process performance were evaluated. The cyclic steady-states of PSA process were reached after 12 cycles. The purity and recovery rate of product gas, pressure and temperature changes were constant as the cycle repeated. It was shown that the P/F ratio gave significant effect on the product recovery rate by increasing the amount of purge gas in purge and regeneration step. The optimal P/F ratio was found to be 0.08. As the cycle time increased, the product purity decreased by increasing the feed gas flow rate. It was found that the optimal operating conditions were P/F ratio of 0.08 and total cycle time of 1,440 seconds with the purity of 97%.