• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.182-188
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• 2011

In this paper, analysis on the performance characteristics of R744-R404A cascade refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree, compressor efficiency, and condensing and evaporating temperature in R404A high- and R744 low-temperature cycle, respectively. The main results were summarized as follows : It was observed that the highest COP of the system is achieved by higher superheating degree in R744 cycle than that in R404A cycle. The COP of the system increased by giving the subcooling degree in both cycles. The COP of the cascade system is the highest value when the system is operated at an optimum evaporation temperature.

• 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.

• 발명특허
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• v.30 no.6 s.348
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• pp.48-50
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• 2005

• Journal of Navigation and Port Research
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• v.36 no.10
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• pp.803-810
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• 2012

Since the introduction of reefer container for seaborne transportation, international trade of reefer products has increased continuously with the development of refrigerate technology, increased speed of the ship and change of consumption pattern. Reefer cargo is perishable and sensitive to temperature, humidity compared with general cargo and normally reefer cargo is more valuable than general cargo. Therefore it needs special care for its handling in transit including land and sea in order to prevent cargo damage. However, lots of claims relating to reefer cargo damage rise frequently in workplace. It may increase unnecessary logistic cost and time. The aim of this study is to improve and prevent damage to reefer container cargo in transit for the purpose of benefits to both merchants and carriers to save unnecessary logistic cost and time as well as to contribute to deliver the cargo more safely and efficiently to destination.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.6
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• pp.575-581
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• 2013

In this paper, the influences of several factors, such as subcooling, superheating degree, internal heat exchanger efficiency, and etc. to the optimal amount of refrigerant charge are investigated for the case of R744-R404A cascade refrigeration system. Refrigerants used in the cascade refrigeration system are R404A in high temperature cycle and R744 in the low temperature cycle. The main results are summarized as follows : The mass flow rate ratio decreases with increasing subcooling, superheating degree and internal heat exchanger efficiency in the high temperature cycle, and evaporating temperature and compression efficiency in the low temperature cycle. And the mass flow rate ratio decreases with decreasing temperature difference of cascade heat exchanger and evaporating, condensing temperature in the high temperature cycle, and subcooling, superheating degree and internal heat exchanger efficiency in the low temperature cycle.

• Korean journal of applied entomology
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• v.39 no.2
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• pp.99-103
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• 2000

The green lacewing, Chrysopa pallens (Rambur), was reared on artificial diets supplementedwith natural products such as lyophilized beef liver, silk worm pupae powder and drone honey beepowder. The performance of the green lacewing was improved siginificantly on only the diet to whichadded 1 % of silk worm pupae powder (wt/v). Larval developement was completed in 15.6 f 0.99 days,cocoon weight was 16.4f2.94 mg, and suvival to adult was 89.3% at 27$^{\circ}$C. And another diet made bymixing 4 part of lyophilized beef liver powder, 4 part of lyophilized beef powder, 3 part of lyophilizedchicken egg, 4 part of sucrose, and 50 mg each of vitamin C and Vanderzant's vitamin B mixture waspromising. Larval development of the green lacewing on this diet was completed in 12.7 f 1.45 days at27"C, pupal weight was 18.1 f 2.24mg, suvival to adult was loo%, and 633f70.4 eggs were laid in 20days after beginning of oviposition.ginning of oviposition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.7
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• pp.564-571
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• 2001

The present study investigated the effect of key parameters on the performance of a cascade system using R-22 and R-23 refrigerants. Experimental data for the cascade system have been compared with simulation results using thermodynamic analysis. The cascade system tested at the evaporating temperature of $-80^{\circ}C $ and the condensing temperature of$40^{\circ}C $. The key experimental parameters were the evaporating temperature of the HTC(-35, -30, -25, -20, $-15^{\circ}C $) and mass flux of the HTC(200, 250, 300kg/$m^2$s). As the evaporating temperature and the mass flux of the HTC were increased respectively, the COP and the refrigerating efficiency were increased and then decreased while the volume flow rate per unit refrigeration capacity showed the opposite trend. The maximum COP and refrigerating efficiency were obtained at the evaporating temperature of the HTC of $-25^{\circ}C $ and the mass flux of 250 kg/$m^2$s.

• The Journal of Bigdata
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• v.9 no.1
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• pp.153-168
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• 2024

In summer, as chillers are considered the main energy consumer of building, the efficient chiller operation is considered important. However, it is difficult to operate chillers to meet the cooling demand of the building as the demand fluctuates with various factors like the internal, external environment and behavior of the occupants and as chiller's constraint cause the current operation constrains operation in future. To address these problems, this study proposes a multi-chiller operation model based on deep reinforcement learning considering the minimum up-time of the chiller. The proposed model learns the value of the chiller operations according to the state composed of metrological and cooling system information and determines operation that minimizes the difference between the supply load and the cooling demand among feasible operations. The practical applicability was improved by applying the training algorithm considering the minimum up-time constraint and Experiments results using the actual data from a Korean university confirmed that the proposed model complies with the chiller constraints and outperforms the existing chiller operation logic of the university in terms of differences from the building cooling demand.

• Clinical and Experimental Reproductive Medicine
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• v.12 no.2
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• pp.99-116
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• 1985

소의 번식효율을 증가시키기 위한 기초실험으로서 6%, 10% 및 20%의 bovine serum albumin 을 사용한 선인들의 방법과 tyrode액을 사용하여 시도한 저자의 방법으로 소의 원정액, 희석정액 및 일반시판 냉동정액으로부터 고활력정자를 분리수집하여 정자의 각종 성상과 광학현미경적 형태를 비교관찰한 결과는 다음과 같다. 1. 원정액으로부터 bovine serum albumin을 사용하여 분리한 정자는 대조군에 비하여 운동성, 운동성 정자수, 정상정자율 및 전진운동성이 현저히 높았고 정자회수율은 6%일 때 가장 높았다. 2. 원정액으로부터 bovine serum albumin을 사용하여 고활력정자를 분리한 후 냉동한 정액의 정자운동성, 정상정자율 및 전진운동성은 대조군에 비하여 현저히 높았고, 이러한 현상은 bovine serum albumin의 농도가 20%일 때에 가장 현저하게 나타났다. 3. Bovine serum albumin을 사용하여 분리한 고활력정자의 냉동전 및 냉동후의 광학현미경적인 기형율은 대조군에 비하여 현저히 낮았다. 4. Bovine serum albumin을 사용하여 분리한 고활력정자는 전자현미경으로 세포막의 확장 및 공포 형성, acrosome의 확장과 density loss의 변형율이 대조군에 비하여 낮았다. 5. 일반시판 냉동정액으로부터의 고활력정자의 분리는 bovine serum albumin을 사용할 때는 어려웠으나, tyrode액을 사용한 이 실험에서는 가능하였다. 6. 원정액, 희석정액 및 냉동정액의 고활력정자회수율은 tyrode 액을 이용하여 80분간 정치하였을때 현저히 높았다. 7. Tyrode 액을 이용하여 원정액, 희석정액 및 냉동정액으로부터 분리된 고활력정자의 운동성, 전진운동성 및 정상정자율은 대조군에 비하여 현저히 높았다. 8. Tyrode 액을 이용하여 원정액, 희석정액 및 냉동정액으로부터 분리한 고활력정자의 광학현미경적 기형율은 대조군에 비하여 현저히 낮았다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.47-51
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• 2017

Recently international cooperations are formed to deal with the environmental pollution of the atmosphere generated by the vapor compression refrigeration system. A refrigeration technique, which can replace existing CFC refrigerants that are the main cause of environmental contamination, has received greater attention. Magnetic refrigeration is a refrigeration technique using the magnetocaloric effect of the magnetic material, and is an eco-friendly refrigeration technology using the solid refrigerant instead of CFC refrigerants. Also it is regarded as an efficient refrigeration system to generate temperature difference between high and low sides using the temperature change of magnetic refrigerants according to the change of magnetic field, instead of using power-consuming and noisy compressor. In this paper, we introduce the magnetic refrigeration apparatus using concentric Halbach cylinder permanent magnets and the experimental results using the apparatus.