• Composites Research
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• 제14권4호
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• pp.27-34
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• 2001

토탈 라그랑지안 방법과 변형율을 가정한 Hellinger-Reissner 원리에 기초한 유한요소법을 이용하여 패치로 보강된 구형 복합재료 쉘의 후좌굴 거동 및 진동 특성을 살펴보았다. 패치 요소는 따로 다른 유한요소를 사용하지 않고 쉘의 중앙면과 다른 기준점을 잡아 두께 변수를 택하여 정식화를 하였다. 비선형 해법으로 원통형 호-길이법을 적용하였고, 후 좌굴 진동은 미소 진폭을 갖는다고 가정하였다. 구형 쉘 패넬에서 패치가 비선형 거동 및 진동수에 미치는 영향을 고찰하였고, 그 결과 패치는 하중지지도를 개선시키킨다. 패치로 보강된 패널의 1차 고유진동수는 등가 패널에 비하여 낮으나, 하중을 받는 경우 1차 고유진동수는 급격히 감소하지 않았다.

• 한국건축시공학회지
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• 제6권3호
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• pp.107-114
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• 2006

In this study, the experiment was carried out to investigate and analyze the engineering properties of concrete using fine aggregate of PS bal slagl. The main experimental variables were water/cement ratio 30, 40, 50(%), water content $170kg/m^3$, replacement ratio of slag fine aggregate 0, 25, 50, 75(%) in experiment I and water/cement ratio 30, 40, 50(%), water content 165, 170, 175($kg/m^3$), replacement ratio of fine aggregate of PS ball 0, 50 in experiment II. According to the test results, the principle conclusions are summarized as follows (1) The workability of slag fine aggregate-mixed concrete tends to improve, as the replacement rate increases. (2) The air content of slag fine aggregate-mixed concrete tends to decrease, as the replacement rate increases. (3) The unit volume weight of slag fine aggregate-mixed concrete tends to significantly increase, as the replacement rate increases. (4) The compressive strength of slag fine aggregate-mixed concrete tends to show more increasing propensity, in case the curing period is relatively long, as the replacement rate increases.

• 태양에너지
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• 제4권2호
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• pp.13-28
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• 1984

Direct Absorption Receiver and Thermal Storage System is a complex problem. This paper describes only characteristic of fluid flow on the receiver. The fluid thicknesses of Molten Salts (Melting Point : $397^{\circ}C$) flowing on the receiver of modified protopype ($10m{\times}10m$) were calculated theorectically, changing the receiver slope from 60 degree to 85 degree (5 steps). The receiver temperatures were $430^{\circ}C$ at the top part and $950^{\circ}C$ at the low part. The flow thickness of the Molten Salts at the top part of the receiver are around 1.9mm in the case of maximum insolution ($50{\times}10^6$juoule/sec; 58.898kg/sec of flow rate) and 2.0mm at the low part. In the case of 3/10 of maximum insolation (flow rate = 17.669kg/sec) the flow thickness at the top part are around 0.9mm and 0.4mm at the low part, and in the case of 1/10 of maximum insolation (flow rate = 5.889 kg/see) the flow thickness at the top part are around 0.6mm and 0.3mm at the low part. From experimental measurements of a normal fresh water thickness flowing on the model plate ($12.7cm{\times}111.76cm$), around 0.8mm at the top part of the plate and around 0.7mm at the low part were obtained in the case of maximum insolation (flow rate = 0.12496 kg/see). In the case of 3/10 (flow rate = 0.03748 kg/see) and 1/10 (flow rate = 0.012496 kg/see) of maximum insolation, around 0.5mm and 0.4mm at the top part, and around 0.3mm and 0.2mm at the low part were obtained respectively. The reason why the thickness of the Molten Salts increase at the low part of the receiver only in case of maximum insolation is that decreasing rate of the viscosity of the Molten Salts is larger than decreasing rate of the density of the Molten Salts during temperature increase from the top to the low receiver plate and decrease of the fluid velocity in accordance with continuity principle. In all cases without the above maximum insolation, the thickness of the Molten Salts and the fresh water decreased at the low part of the plate because of gravity force effects rather than friction effects and of continuity principle. All simillar flow patterns were obtained through all cases of the insolation making an exception of only maximum insolation.

• 혜화의학회지
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• 제10권2호
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• pp.91-96
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• 2002

We arrived at the following conclusions after we have studied esophagitis through the literatures of oriental and western medicine. 1. The western medical causes of acute esophagitis are corrosiveness chemical material, esophageal or gastric disease, trauma, blister stomatitis, filamentous fungus infection and uremia of chronic patient etc, and the oriental medical causes are qi and blood stagnation, blood stasis and stagnation, stagnant phlegm by coldness, heating, dyspepsia and food poisoning etc. 2. The western medical causes of chronic esophagitis are malfunction of lower esophageal sphincter, esophageal tom chink and hernia, increase of gastric pressure by overeating, fatness, pregnancy and ascites etc, and the oriental medical causes are asthenic cardiac qi, hepatic qi attacking stomach by seven kinds of depression, cold-damp stagnation and insufficiency of gastric qi by overeating, excessive drinking and sexual indulgence etc. 3. The main symptoms of acute esophagitis are severe chest pain, instantly vomiting, swallowing pain etc, and chronic esophagitis are occasionally light chest pain, heart bum, anorexia, dysphagia, dizziness, general body weakness etc. These symptoms are come under thoracic obstruction, acid regurgitation, vomiting and chest pain of oriental medicine. 4. The western medical diagnoses of acute and chronic esophagitis have used radiation test, esophageal endoscopy, esophageal pressure test and biopsy etc, and the oriental medical diagnoses have used syndrome differentiation by four examination of inspection, listening and smelling examination, inquiring, pulse-taking and palpitation. 5. The western medical treatments of acute esophagitis have regarded preservation stability of esophagus as a principle, and the oriental medical treatments mainly have used expelling pathogen of expelling cold and regulating qi, cooling and removing stasis, promoting blood circulation to remove blood stasis, eliminating phlegm and regulating qi. 6. The western medical treatments of chronic esophagitis have regarded decrease flowing backward of gastric juice as a purpose, and the oriental medical treatments mainly have used strengthening body resistance of replenishing and strengthening cardioqi, dispersing stagnated hepatoqi, expelling cold and dehygrosis, invigorating stomach and nourishing qi.

• Preventive Nutrition and Food Science
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• 제16권4호
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• pp.394-407
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• 2011

Better understanding of the complex factors leading to human diseases will be necessary for both long term prevention and for managing short and long-term health problems. The underlying causes, leading to a global health crisis in both acute and chronic diseases, include finite global health care resources for sustained healthy human survival, the population explosion, increased environmental pollution, decreased clean air, water, food distribution, diminishing opportunities for human self-esteem, increased median life span, and the interconnection of infectious and chronic diseases. The transition of our pre-human nutritional requirements for survival to our current culturally-shaped diet has created a biologically-mismatched human dietary experience. While individual genetic, gender, and developmental stage factors contribute to human diseases, various environmental and culturally-determined factors are now contributing to both acute and chronic diseases. The transition from the hunter-gatherer to an agricultural-dependent human being has brought about a global crisis in human health. Initially, early humans ate seasonally-dependent and calorically-restricted foods, during the day, in a "feast or famine" manner. Today, modern humans eat diets of caloric abundance, at all times of the day, with foods of all seasons and from all parts of the world, that have been processed and which have been contaminated by all kinds of factors. No longer can one view, as distinct, infectious agent-related human acute diseases from chronic diseases. Moreover, while dietary and environmental chemicals could, in principle, cause disease pathogenesis by mutagenic and cytotoxic mechanisms, the primary cause is via "epigenetic", or altered gene expression, modifications in the three types of cells (e.g., adult stem; progenitor and terminally-differentiated cells of each organ) during all stages of human development. Even more significantly, alteration in the quantity of adult stem cells during early development by epigenetic chemicals could either increase or decrease the risk to various stem cell-based diseases, such as cancer, later in life. A new concept, the Barker hypothesis, has emerged that indicates pre-natal maternal dietary exposures can now affect diseases later in life. Examples from the studies of the atomic bomb survivors should illustrate this insight.

• Journal of Preventive Medicine and Public Health
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• 제7권1호
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• pp.203-209
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• 1974

This study is intended to comparison of the recent ideal number of children and atrial approach for analyzing value system for children that form attitude affecting birth control with earlier study conducted 10 years ago. In general the traditional fertility pattern of Korea may be considered as 'early marriage and high fertility' backed by the confucian value system of a farming-oriented country. A selective attitude favoring sons contributes substantially to fertility. But Korea is now moving toward a late marriage and fertility pattern. This has been due to the repid introduction of western culture and a partial acceptance of western value systems, a relative weakening of traditional value systems, a gradual increase in infant and child servival rates thresh medicines, and a desire to avoid having too many children because of economic poverty. This study showed following results: Ideal number of sons and daughters in urban area was decreased by 0.2 respectively compared to earlier study. In rural area, the number of decrease of sons and daughters was 0.5 and 0.2 respectively. The conception concerning Happiness has changed to wealth from health in previous opinion. Regarding attitude toward having sons, 98 percent of them wanted to have sons positively, moreover 10 percent of them wanted two or more sons. Regarding reasons for the wanting sons, we see that economic and traditional considerations, such as dependance in old age, and inheritance of the family line, are a principle concern of about 56 percent in both areas. The rate of dependence in old age was decreased conspicuously compare to previous study while the rate of helding rituals was increased remarkably in rural area. Among reasons for limiting family size. 'for better living and for better education for their children were main rasons reted 46 percent in urban, 51 percent in rural areas. The rates were not changed compare to previous study. Regarding attitude of those who have no son or children, the rate of re-marriage with second wife was decreased remarkably in rural area and the rate of living without special behaivor for having son was increased compare to previous study.

• Macromolecular Research
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• 제17권7호
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• pp.528-532
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• 2009

The size and shape of free volume (FV) holes available in membrane materials control the rate of gas diffusion and its permeability. Based on this principle, a segmented, thermo-sensitive polyurethane (TSPU) membrane with functional gate, i.e., the ability to sense and respond to external thermo-stimuli, was synthesized. This smart membrane exhibited close-open characteristics to the size of the FV hole and water vapor permeation and thus can be used as smart food packaging materials. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), positron annihilation lifetimes (PAL) and water vapor permeability (WVP) were used to evaluate how the morphological structure of TSPU and the temperature influence the FV holes size. In DSC and DMA studies, TSPU with a crystalline transition reversible phase showed an obvious phase-separated structure and a phase transition temperature at $53^{\circ}C$ (defined as the switch temperature and used as a functional gate). Moreover, the switch temperature ($T_s$) and the thermal-sensitivity of TSPU remained available after two or three thermal cyclic processes. The PAL study indicated that the FV hole size of TSPU is closely related to the $T_s$. When the temperature varied cyclically from $T_s-10{\circ}C$ to $T_s+10^{\circ}C$, the average radius (R) of the FV holes of the TSPU membrane also shifted cyclically from 0.23 to 0.467 nm, exhibiting an "open-close" feature. As a result, the WVP of the TSPU membrane also shifted cyclically from 4.30 to $8.58\;kg/m^2{\cdot}d$, which produced an "increase-decrease" response to the thermo-stimuli. This phase transition accompanying significant changes in the FV hole size and WVP can be used to develop "smart materials" with functional gates and controllable water vapor permeation, which support the possible applications of TSPU for food packaging.

• Journal of Power Electronics
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• 제13권4호
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• pp.626-635
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• 2013

An analysis of the junction capacitance in resonant rectifiers which has a significant impact on the operating point of resonance circuits is studied in this paper, where the junction capacitance of the rectifier diode is to decrease the resonant current and output voltage in the circuit when compared with that in an ideal rectifier diode. This can be represented by a simplified series resonant equivalent circuit and a voltage transfer function versus the normalized operating frequency at varied values of the resonant capacitor. A low voltage to high voltage push-pull DC/DC resonant converter was used as a design example. The design procedure is based on the principle of the half bridge class-DE resonant rectifier, which ensures more accurate results. The proposed scheme provides a more systematic and feasible solution than the conventional resonant push-pull DC/DC converter analysis methodology. To increase circuit efficiency, the main switches and the rectifier diodes can be operated under the zero-voltage and zero-current switching conditions, respectively. In order to achieve this objective, the parameters of the DC/DC converter need to be designed properly. The details of the analysis and design of this DC/DC converter's components are described. A prototype was constructed with a 62-88 kHz variable switching frequency, a 12 $V_{DC}$ input voltage, a 380 $V_{DC}$ output voltage, and a rated output power of 150 W. The validity of this approach was confirmed by simulation and experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.355-358
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• 2004

Currently, to overcome the limit of a 14V power supply system and to enhance the stability of this system high and to make the fuel efficiency better, a research development of a 42V power supply system is actively the progress. As an intermediate step to change into an unity power supply system, a 42V/14V dual power supply system uses a DC/DC Converter as one of structure elements. Considering the main electric power sources in the next generation of the car is a 42V system a 14V power supply system has advantages as follows : In be managed efficiently and to increase the redundancy at start, to jump start with any vehicles, etc. We need the introduction of a hi-directional converter that can flow the energy each other in a dual 42V-l2V system. This paper proposed the ZVS hi-directional CUK DC/DC converter which decrease the weight with the size of the DC/DC Converter and minimize the loss when the switching happen. In this paper, a circuit design method and an action principle of the circuit was proposed. To verify the proposed circuit, a comprehensive evaluation with theoretical analysis, simulation results is presented.

• Journal of Dairy Science and Biotechnology
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• 제14권1호
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• pp.43-56
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• 1996

The world dairy industry has been driving their dairy policy on the basis of the self-supportihg principle. With progressing the GATT negotiation, the objective production amount has been reduced to maintain the optimum level, which decreasing the extra supply and over-stock before the U.R talks. The Oceania countries, where has the price competition capability, are continually increasing the milk production amount. Even through the USA is trying to increase their production amount with new export policy, the U.S.S.R collapse-down caused to decrease the milk production in world-wide basis. Because the U.S.S.R produced the highest amount of milk in the world. Moreover Europe Union countries, which recorded the half amount of dairy products in the world was decreasing their milk production. Therefore, about 4% of shortage is encountering at major dairy production countries in the standpoint of supply and demand. The drastic increasement of foreign dairy product import affects the domestic dairy industry with raw milk replacement and new dairy food demands creation since 1995, the initial period of free import system. Now, the domestic dairy industry are facing the inevitable problems such as the correction of producting and processing system. First of all, our dairy industry should resettle down the dairy production structure on the basis of self-supply of raw milk and offer the accurate dairy food informations. We still need to improve the raw milk quality. Also, more efforts are needed to have proper raw milk price policy. General domestic policies including the settlement of raw milk supply and demand, the reliability of inspection system in raw milk, ideal raw milk price system, centralization of raw milk collection, specially separated dairy organization should be improved legally in our dairy industry.