• KIEAE Journal
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• 제7권6호
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• pp.17-22
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• 2007

The integration of PV modules into building facades or roof could raise their temperature that results in the reduction of PV system's electrical power generation. Hot air can be extracted from the space between PV modules and building envelope, and used for heating in buildings. The extraction of hot air from the space will enhance the performance of BIPV systems. The solar collector utilizing these two aspects is called PV/T(photovoltaic/thermal) solar collector. This paper compares the experimental performance of two different types of air type PV/T collector units: the base case of a collector unit with 10cm gap for forced ventilation and the other unit with copper pin attached to PV module to enhance its thermal performance. The experimental results shows that the base case unit had the overall efficiency of 41.9% and the improved unit with copper pin attached to PV module had 50.1% efficiency. For these air type PV/T units, the forced ventilation of the air space improved the electrical performance as well as the thermal performance.

• Nuclear Engineering and Technology
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• 제53권10호
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• pp.3247-3255
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• 2021

As Probabilistic Safety Assessments (PSAs) are thoroughly conducted for the Site Operating States (SOSs) for a single unit, multi-unit Probabilistic Safety Assessments (MUPSAs) are ongoing worldwide to address new technical challenges or issues. In South Korea, the determination of the site operating states for a single site requires a logical approach with reasonable assumptions due to the fact that there are 4-8 operating units for each site. This paper suggests a simulation model that gives a reasonable expectation of the site operation states using the Monte-Carlo method as a stochastic approach and deterministic aspects such as operational policies. Statistical hypothesis tests were conducted so that the reliance of the simulation results can be guaranteed. In this study, 7 units of the Kori site were analysed as a case study. The result shows that the fraction of full power for all 7 units is nearly 0.45. For situations when more than two units are not in operation, the highest fraction combination was obtained for Plant Operation State (POS) 8, which is the stage of inspection and repairment. By entering various site operation scenarios, the simulation model can be used for the analysis of other site operation states.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4042-4051
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• 2021

In this work, we applied a multilevel modeling technique to estimate the diametral creep in the pressure tubes of Korean Canada Deuterium Uranium (CANDU) units. Data accumulated from in-service inspections were used to develop the model. To confirm the strength of the multilevel models, a 2-level multilevel model considering the relationship between channels for a CANDU unit was compared with existing linear models. The multilevel model exhibited a very robust prediction accuracy compared to the linear models with different data pooling methods. A 3-level multilevel model, which considered individual bundles, channels, and units, was also implemented. The influence of the channel installation direction was incorporated into the three-stage multilevel model. For channels that were previously measured, the developed 3-level multilevel model exhibited a very good predictive power, and the prediction interval was very narrow. However, for channels that had never been measured before, the prediction interval widened considerably. This model can be sufficiently improved by the accumulation of more data and can be applied to other CANDU units.

• The Korean Journal of Ecology
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• 제18권1호
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• pp.63-87
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• 1995

The present study was undertaken to classify and describe the Quercus mongolica forest on Mt. Sobaek (36°50'∼ 37°07'N, 128°25'∼ 128°35'E), Korea by a reciprocal averaging methol (RA ordination) and the methodology of the ZM school of phytosociology. Atemporal vegetation tabel was prepared by the RA ordination. As a result it showed that the RA ordination on the first axis is very applicable for selecting the character and differential species of vegetation units of the Quercus mongolica forest. The phytosociological investigations were carried out in 34 stands on the mountain. The field data obtained were classified by the tabel comparison method. For the establishment of new vegetation units, the floristic composition of the Quercus mongolica forest was compared with those of the other vegetation units of the Mt. Sobaek, Considering the candidates of the character and differential species derived from RA ordination. As the result, the forest vegetation was classified into the following vegetation units; Fagetea crenatae Miyawaki et al. 1968 Acero-Quercetalia mongolicas Song 1988 em. Takeda et al.1994 Lindero-Quercetalia mongolicae Kim 1990 1. Lindero-Quercetum mongolicae assoc. nov. 1-1. quercetosum serratae subassoc. nov 1-2. typicum subassoc. nov. Rhododendro-Qurcion mongolicas Song 1988 em. Takeda et al. 1994. It is inferred that the Lindero-Quercion mongolicae and the Rhododendro-Quercion mongolicae corresponded to the cool-temperate forests of central and northern areas, respectively, in Korean Peninsula. Syntaxonomical synonyms were also rearranged based on the result of the present study. On the other hand, the RA ordination of stands and species on the first and second axes revealed some environmental gradients such as altitute, human impact and species richness between the vegetation units. However, the RA ordinations is considered to be less indicative for the gradients of the lower vegetation units than association. With the present study. some phytosociological problems in Korea were discussed here in detail from the floristic viewpoint.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 춘계학술대회
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• pp.315-319
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• 1996

We have developed a prototype patient monitoring system including module-based bedside units, interbed network, and central stations. A bedside unit consists of a color monitor and a main CPU unit with peripherals including a module controller. It can also include up to 3 module cases and 21 different modules. In addition to the 3-channel recorder module, six different physiological parameters of ECG, respiration, invasive blood pressure, noninvasive blood pressure, body temperature, and arterial pulse oximetry with plethysmogaph are provided as parameter modules. Modules and a module controller communicate with up to 1Mbps data rate through an intrabed network based on RS-485 and HDLC protocol. Bedside units can display up to 12 channels of waveforms with any related numeric informations simultaneously. At the same time, it communicates with other bedside units and central stations through interbed network based on 10Mbps Ethernet and TCP/IP protocol. Software far bedside units and central stations fully utilizes gaphical user interface techniques and all functions are controlled by a rotate/push button on bedside unit and a mouse on central station. The entire system satisfies the requirements of AAMI and ANSI standards in terms of electrical safety and performances. In order to accommodate more advanced data management capabilities such as 24-hour full disclosure, we are developing a relational database server dedicated to the patient monitoring system. We are also developing a clinical workstation with which physicians can review and examine the data from patients through various kinds of computer networks far diagnosis and report generation. Portable bedside units with LCD display and wired or wireless data communication capability will be developed in the near future. New parameter modules including cardiac output, capnograph, and other gas analysis functions will be added.

• 콘크리트학회논문집
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• 제19권1호
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• pp.83-90
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• 2007

본 연구에서는 와이어로프 단위를 이용한 철근콘크리트 보의 비 부착형 보강 공법을 제시하였다. 전단에서 파괴된 15개의 보가 제시된 보강 공법에 의해 보수, 보강 된 후 재 실험되었다. 주요 변수는 전단경간비, 와이어로프 단위의 초기 프리스트레스력, 배근 방법 및 간격이다. 실험 결과 제시된 와이어로프로 보강된 보들의 전단강도와 파괴 후 연성 거동이 원래 보의 것들에 비해 매우 향상되었다. 또한 수직 와이어로프보다는 경사 와이어로프가 내력 향상에 유리하였으며 와이어로프에 작용된 초기 프리스트레스의 증가는 콘크리트 스트럿에서 주 인장응력의 크기를 감소시킴으로서 사인장 균열내력을 향상시켰다. 보강된 보의 전단내력과 ACI 318-05 및 EC 2 설계기준과의 비교로부터 전단경간비 2.5 이하의 보강된 보들의 전단내력은 ACI 318-05 기준에 의해 적절히 평가될 수 있었다. 한편 EC 2는 전단경간비 2.5 이상인 보강된 보들에서 와이어로프의 전단 전달 능력을 과대평가하였다.

• The Korean Journal of Ecology
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• 제19권5호
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• pp.431-451
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• 1996

The present studwas undertaken to classify and describe the riverside vegetation around Hanchon (36°27’-36°51’N, 128°15’-128°37’E), a tributary in the upper stream area of Nak-tong River, South Korea by methods of the ZM school of phytosociology. As a result the vegetation was divided into twenty three associations and communities belonging to ten classes. Reflecting various human impacts in the past, the associations and communities of the Artemisietea principis were most plentiful there. The vegetation units obtained in the present study were as follows: A. forest vegetation A-1 Fagetea crenatae:Zelkova serrata community, Larix leptolepis community; B. Shrub vegetation B-1 Salicetea sachalinensis:Salicetum gracilistylae, Salicetum graciliglandis assoc. nov., B-2 Rosetea sachalinensis:Salicetum gracilistylae, Salicetum graciliglandis assoc. nov., B-2 Rosetea multiflorae:Stephanandra incisa community, Lycium chinense community; C. Grassland vegetation C-1 Lemnetea minoris:Spirodela polyrhiza-Lemna paucicostata community, C-2 Bidentetea tripartiti:Polygonetum thunbergii, Polygonetum sieboldii-hydropiperis, Panico Polygonetum hydropiperis, Pharagmitetea :Oenantho- Phalaridetum arundinaceae, Phragmitetum japonicae, Miscanthetum sacchariflori, Phragmites australis community, C-4 Artemisietea principis:Artemisia princeps community, Impatiens textori community, Lactuco indicae-Humuletum japonicae, Pueraria lobata-Humulus japonicus community, Pennisetum alopecuroides community, C-5 chenopodietea:Echinochloa crus-galli var. orizicola community, Digitaria adsecendens community, Polygonum nodosum community, C-6 Miscanthetea sinensis: Miscanthus sinensis community, C-7 Plantaginetea:Eragrotis multicaulis-Plantago asiatica community. It is inferred that the endemic vegetation units in the riverside vegetation of Korea are very rare, because most of the vegetation units obtained in the present study are common with those of Japan. Among the above vegetation units, the Salicetum graciliglandis was established as a new association. On the other hand, the associations and communities of classes characterizing the riverside vegetation increased with a decrease of human impacts from the downstream to the upstream in Hanchon, while the number of the naturalized plants was the reverse. Also based on the present phytosociological work, the relation between the vegetation units and their environmental conditions and the restoration ecology and nature conservation of the riverside vegetation were discussed here in detail.

• 한국식품저장유통학회지
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• 제8권2호
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• pp.131-139
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• 2001

Kiyomi tangor(Citus unshiu x sinensis) was stored at 3$\^{C}$ and 85% relative humidity, and the changes in firmness, pectin degrading enzymes activity and other physicochemical properties of citrus fruits during storage were investigated. Decay ratio and weight loss during 180 days’ storage were increased gradually to 13.0% and 12.9%, respectively. Firmness of fruits with 2 mm probe was decreased gradually from 808.7 g-force to 406.4 g-force, and moisture of peel and flesh were decreased from 76.5% to from 89.6% to 87.6% during storage, respectively. Exo-polygalacturonase activity of peel after 150 days’ storage were increased gradually to 558.09 units/100g. Pectin methylesterase activity of peel and flesh were increased from 14.7 units/g to 2.3 units/g, and from 9.4 units/ml to 2.7 units/ml at 150days’ storage, respectively. Endo-polygalacturonase activities were not changed notably during storage. Alcohol-insoluble solid(AIS) of peel was not changed notably. During storage of the fruits water soluble pectin(WSP) of peel and flesh were increased from 474.49 mg/100g to 614.29mg/100g, and from 66.91mg/100g to 92.74mg/100g as wet basis, respectively. Hexameta-phosphate soluble pectin(HMP) of peel were decreased from 405.5mg/100g to 270.43mg/100g, hydochloric acid soluble pectin(HSP) of peel was also decreased from 544.02mg/100g to 412.64mg/100g during storage. Total pectin substance(TPS) of peel and flesh were decreased from 1,424.01mg/100g to 1,297.36mg/100g, and from 165.51mg/100g to 171.54mg/100g, respectively. Composition ratio of pectin was in order of WSP > HSP > HMP.

• Applied Biological Chemistry
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• 제27권
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• pp.3-17
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• 1984

Anaerobic digestion has recently attracted all over the world and Korea also shows no exception. The major benefits of anaerobic digestion are energy production, water pollution control, pathogen reduction and effective manure production. In Korea it was recognized in late sixties that there was a positive need to find alternative energy for farmers household. The main traditional energy sources in rural area were crop residues and forestry products. Therefore Office of Rural Development through its Rural Guidance Bureau disseminated about 29,000 household biogas units from 1969 to 1975 to provide cooking fuel for farmers household and to improve the mode of farmers living standards. The units were welcomed by farmers at that time. Now, however, most of them are not using due to a number of reasons associated with cold winter and some techno-economical problems (in those day, fossil fuel was quite expensive to compare with other prices and since then farmers income was quickly increased). The author studied on bag type household biogas plant to solve some technical problems of existing household biogas plants, but this also has little appeal for the farmers. From 1977 author studied on village scale biogas plant with two pilot plants. From the viewpoint of energy production, COD removal, kill rate of pathogen and fertilizer value, the results obtained from the experiments were quite promising, but the construction cost of the village scale biogas plant was too high for the farmers in Korea. To find most suitable biogas plant for farmers in Korea through the simplifying the biogas digester, the author developed batch-load biogas plant. By feeding coarse crop residues and manures, total solids concentrations of the batch-load biogas plant are about 28 percent which is much higher than continous digester of 5-8 percent. The batch-load biogas plant was welcomed by many farmers in Korea when it was reported on TV and newspapers. The plant was disseminated 154 units in 1982, 766 units in 1983 and 812 units in 1984 as a promissing project. Besides these biogas plant experiments, studies were also conducted 1) to determine gas production rate with agricultural wastes, 2) to evaluate the effect of loading rate, dilution, retention time on biogas production, 3) to project the amount of potencial energy from agricultural wastes.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.675-680
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• 2002

Cracking and bulging in welded and internally lined pressure vessels that work in thermal-mechanical cycling service have been well known problems in the petrochemical, power and nuclear industries. However, published literature and industry surveys show that similar problems have been occurring during the last 50 years. A better understanding of the causes of cracking and bulging causes is needed to improve the reliability of these pressure vessels. This study attempts to add information required for increasing the knowledge and fundamental understanding required. Typical examples of this problem are the coke drums in the delayed coking units refinery process. This case was selected for experimental work, field study and results comparison. Delayed coking units are among the refinery units that have higher economical yields. To shut down these units represents a high negative economical impact in refinery operations. Also, the maintenance costs associated with repairs are commonly very high. Cracking and bulging occurrences in the coke drums, most often at the weld areas, characterize the history of the operation of delayed coking units. To design and operate more robust coke drums with fewer problems, an improved metallurgical understanding of the cracking and bulging mechanisms is required. A methodology that is based field experience revision and metallurgical analyses for the screening of the most important variables, and subsequent finite element analyses to verify hypotheses and to rank the variables according to their impact on the coke drum lives has been developed. This indicated approach provides useful information for increasing coke drum reliability. The results of this work not only order the most important variables according to their impact in the life of the vessels, but also permit estimation of the life spans of coke drums. In conclusion, the current work shows that coke drums may fail as a combination of thermal fatigue and other degradation mechanisms such as: corrosion at high and low temperatures, detrimental metallurgical transformations and plastic deformation. It was also found that FEA is a very valuable tool for understanding cracking and bulging mechanisms in these services and for ranking the design, fabrication, operation and maintenance variables that affect coke drum reliability.