• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1971-1978
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• 2011

In RFID-based cold-storage systems, product locations are recognized as the logical locations of RFID readers which are attached to the entrance of the cold rooms. However, through these methods, product locations can be incorrect in many different situations of a storage. Cold storage rooms have a huge rage in temperature, and the product in the cold-storage spoils easily. Therefore, highly precise product locations is very important for the product quality In this paper, a new approach is suggested to manage the storage location inaccuracy by adding two readers to existing forklift and attaching RFID tags to the ceiling. One reader recognizes ceiling tags to acquire location data, and the other recognizes product tags to acquire product detail data loaded on the forklift. The product can be seamlessly tracked and traced in realtime by monitoring and analyzing data gathered from these readers. Through the proposed location management method, the effectiveness of the product management in cold-storage can be improved consequently.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.28.2-28.2
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• 2005

• 보일러설비
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• s.75
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• pp.88-92
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• 2000

빙축열시스템의 기존운전방식은 냉동기와 빙축열조의 적절한 조합운전에 의하여 크게 두가지 방식이 이용되고 있다. 이것은 냉동기우선 그리고 빙축열우선 운전방식이며 운전제어의 용이성 그리고 비용측면의 고려 등으로부터 선정되고 있다. 하지만 이러한 운전방식은 운전비용을 절감하기 위한 최선의 기법은 되지 못하고 있으므로, 더욱 운전비를 절감할 수 있는 운전기법을 계획하고 이것으로부터 제어기를 위한 내용에 대하여 설명하고자 한다.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.210-211
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• 2013

냉동차량은 이동 또는 정차 중에도 냉동 부하에 일정 온도를 유지 시켜야한다. 종전의 상용차량에 냉동시스템은 차량의 엔진과 연계하여 압축기를 구동하거나 엔진과 연계된 발전기의 전력을 이용하여 일정 온도를 유지하였다. 이러한 방식은 제어가 쉽지 않고 효율이 낮은 단점을 가지고 있다. 본 논문에서는 이러한 단점을 개선하고자 냉동차량이 정차 중인 무시동 기관에서도 일정 온도를 유지 할 수 있도록 센서리스 제어방식이 적용된 3상 인버터를 제안하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.242-244
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• 2011

최근 넓은 창고에서 물품들을 좀 더 효율적으로 관리하기 위해 RFID(Radio Frequency Identification)를 이용한 창고관리시스템(Warehouse Management System)에 대한 연구가 활발히 진행되고 있다. 창고관리시스템에서 중요한 요소 중 하나는 물품의 정확한 위치파악이다. 특히 냉동 창고에서는 물품 보관을 하는 coldroom의 안팎 온도차이로 인한 물품의 적재위치 오류는 물품의 변질을 가져오게 하므로 실시간 정확한 위치를 파악하는 것이 중요한 요소가 된다. 기존의 연구방법들에서는 coldroom 입구에 RFID리더기를 설치하여 물품이 인식될 때 단지 그곳에 적재되는 것으로 인식하였다. 그러나 이러한 방법으로는 물품이 coldroom으로 들어가다 다시 돌아 나오는 경우, 반대로 물품이 밖으로 나가다 다시 들어오는 경우 등과 같은 상황에서는 물품의 위치가 잘못된 정보를 가지게 된다. 본 논문에서는 냉동 창고관리시스템에서 2대의 RFID리더기가 설치된 지게차를 이용하여 물품의 적재위치 정확성을 높이기 위한 방법을 제안한다. 지게차에 설치된 2개의 RFID리더기는 각각 천장에 부착된 태그로부터 위치데이터와 지게차에 적재된 물품데이터를 획득한다. 2개의 리더기로부터 수집된 데이터를 분석하여 물품의 입/출고 상황정보와 물품의 이동경로정보를 실시간으로 모니터링 할수 있다. 이를 통해 실시간 냉동 창고 적재위치 오류를 감지해 냄으로써 냉동 창고관리시스템의 물품보관에 대한 효율성을 높일 수 있게 된다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.88-90
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• 2011

It is a very important to manage inventory quickly and accurately in Refrigerated commercial warehouses in which a lot of logistics are often shipping and receiving. Because most of systems for managing refrigerated warehouses consist of COBOL, it will be raised maintenance costs. There is no service for consignees who are consumer of refrigerated warehouses and they use only a fax or a phone for orders. In this paper, we design a web mobile middleware platform supporting legacy systems and based on SaaS which supports a variety of value-added services which are fit consignees, solving problem of outdated legacy systems and no services for consignees.

• Journal of Power System Engineering
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• v.10 no.3
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• pp.81-87
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• 2006

This paper deals with an empirical model for decoupling control to control the refrigeration system effectively. The conventional control schemes of the system are mainly focused on representative two control methods, superheat control and capacity control. The capacity control is basically conducted to respond partial loading conditions on the purpose of energy saving. The superheat control is mainly carried out to maintain maximum coefficient of performance (COP). In the variable speed refrigeration system, the capacity and the superheat are controlled by inverters and electronic expansion valves respectively for saving energy and improving cost performance. The capacity and superheat can not be controlled independently because of interfering loop when the compressor speed and opening angle electronic expansion valve is varied. Therefore, we suggest decoupling model to eliminate the interfering loop at first. Next, each transfer function in decoupling control model is obtained from number of experiments.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.187-193
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• 2005

In this paper, we proposes a man-machine interface design for fault diagnosis system with inter-node search method in a Petri net model. First, complicated fault cases are modeled as the Petri net graph expressions. Next, to find out causes of the faults on which we focus, a Petri net model is analyzed using the backward reasoning of transition-invariance in the Petri net. In this step, the inter-node search method algorithm is applied to the Petri net model for reducing the range of sources in faults. Finally, the proposed method is applied to a fault diagnosis of a refrigeration system to confirm the validity of the proposed method.

• Journal of Power System Engineering
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• v.11 no.4
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• pp.50-55
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• 2007

Nowadays, demands on super low temperature condition for industrial and commercial uses are thriving. Considering of its wide application in the present and the future, study of the super-low temperature refrigeration system should be actively carried out. This study is aimed to investigate refrigeration capacity and coefficient of performance(COP) of the cascade refrigeration system, as well as to get the system which can reach evaporator temperature of $-70^{\circ}C$. For this purpose, R290 and R170 are charged in high stage and low stage respectively. Finally the characteristics of system using R290 and R170 will be proposed. Additionally, In this experiment, the flow rate of air flowing through the LS evaporator and the compressor inlet pressure were varied to investigate the refrigeration capacity and coefficient of performance characteristics.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.993-1001
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• 2001

Experimental investigation on the performance of dual-evaporator refrigeration system with an ejector has been carried out. In this study, a hydrofluorocarbon (HFC) refrigerant R134a is chosen as a working fluid. The condenser and two-evaporators are made as concentric double pipes with counter-flow type heat exchangers. Experiments were performed by changing the inlet and outlet temperatures of secondary fluids entering condenser, high-pressure evaporator and low-pressure evaporator at test conditions keeping a constant compressor speed. When the external conditions (inlet temperatures of secondary fluid entering condenser and one evaporator) are fixed, results show that coefficient of performance (COP) increases as the inlet temperature of the other evaporator rises. It is also shown that the COP decreases as the mass flaw rate ratio of suction fluid to motive fluid increases. The COP of dual-evaporator refrigeration system with an ejector is superior to that of a single-evaporator vapor compression system by 3 to 6%.