• 한국전기전자재료학회논문지
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• 제24권5호
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• pp.422-426
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• 2011

Piezoelectric materials can be used to convert mechanical energy into electrical energy. In this study, we investigated the possibility of harvesting from mechanical vibration force using a high efficient piezoelectric material-polyvinylidene fluoride (PVDF). A piezoelectric energy harvesting system consists of rectifier, filter capacitor, resistance. The experiments were carried out with impacting force to PVDF film with the thickness of 1 ${\mu}m$. The output power was measured with change in the load resistance value from 100 ${\Omega}$ to 2.2 $M{\Omega}$. The highest power was obtained under optimization by selection of suitable resistive load and capacitance. A power of 0.3082 ${\mu}W/mm^2$ was generated at the external vibration force of 5 N (10 Hz) across a 1 $M{\Omega}$ optimal resistor. Also, the maximum power of 0.345 ${\mu}W/mm^2$ was generated at 22 ${\mu}F$ and 1 $M{\Omega}$. The developed system was expected at a solution to overcome the critical problem of making up small size energy harvester.

• 수산해양기술연구
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• 제42권4호
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• pp.195-202
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• 2006

To determine the relative efficiency and mesh selectivity of gill net for the Pacific saury, Cololabis saira, a series of fishing experiments was carried out in the Northwest Pacific Ocean from August 13 to October 13 in 2002, using gill nets of different mesh size(30, 33, 35, 37, 39 and 42mm) constructed from two kinds of twine material(monofilament, twisted multifilament nylon web). The relative efficiency of two material gears was expressed as the ratio obtained by dividing monofilament catch by multifilament catch in number. The master selection curve of each material gear was estimated by applying the extended Kitahara's method. The catch of experimental gears is mostly Pacific saury(98.6%), Cololabis saira. The kinds of bycatch are common squid(0.7%), Pacific mackerel(0.6%), etc. Catch comparisons in the two gears showed that monofilament nylon nets are 1.7 times more efficient. The optimum values in monofilament and multifilament gill net for Pacific saury are 8.28 and 8.23, respectively.

• 대한치과보철학회지
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• 제37권5호
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• pp.567-580
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• 1999

Accurate reproduction of intraoral tissue is essential in the fabrication of fixed prosthesis. This selection of impression material and method is very important. In this study, vinyl polysiloxane type impression material $Panasil^{(R)}$ was used. Three impression methods ; one-step technique, individual tray technique, and individual tooth tray technique using the vinyl polysiloxane type bite registration material $Futar^{(R)}$ Occlusion, were used to take horizontal and vertical impression. Improved stone models were fabricated. The amount of occlusal surface discrepaneies, interabutment distance discrepancies, amount of marginal defect were evaluated with the $X-PLAN360d^{(R)}$ and photoscanning. The results were as follows. 1. There was no significant difference in occlusal surface according to the directions and techniques of impression taking. 2. There was no significant difference in interabutment distance discrepancies according to the directions and techniques of impression taking 3. There was no significant difference in marginal discrepancies according to the direction of impression taking but there was significant difference between one-step technique and individual tray technique, individual tooth tray technique (P<0.05). Taken together, these results suggest that individual tray technique and individual tooth tray technique are more accurate for impression taking than one-step technique.

• 한국농촌건축학회논문집
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• 제8권1호
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• pp.33-42
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• 2006

The rice mill occurred from modernization process of the farming village. It comes to follow in intention of the architect and is not the position building. By the user of the building it comes to follow necessary and it is a position thing. The like this rice mill was the community center of the village. Also the material which is unique and form quality were land mark of the village. The object of research is the rice mill where it takes charge of a like this role. And the scope of research is 8 rice mills of Eomjeong Myeon Chungju City which is located in the northern Chungbuk area. The progress of research the documentary survey, actual measurement, question, field work it analyzed the construction quality which the rice mill keeps with base and it arranges. The results of study are follows; 1. conditions of location : The rice mill the entrance of the village, the crossroads system is formed most the place is doing in the place which well. 2. The inside composition of a space : In order to compose the work space and the store space efficiently the plane surface is doing a rectangular form. 3. Form of roof : The roof raises the efficient characteristic of the work where is not the design which is intended to be naturally formed from the space composition for. 4. Selection of material : Most it was a natural enemy and an utility, it selected the scientific material and it used.

• 한국유기농업학회지
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• 제23권4호
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• pp.659-682
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• 2015

This study was conducted to suggest ideal management system for organic materials. As the performing method of the study, surveyed results on understanding of related persons (organic farmer 846, organic materials manufacture 70 and Organic materials Auditors 7) with eco-friendly farming were used. And the opinion on unintentional pollution source contained in organic materials was surveyed additionally. The issues pointed out by organic farmers on product of organic materials were high price (60% to total), poor efficacy (16%), disorder on distribution system (13%) and containing chemicals as a pesticide (10%). And notification system for organic materials was accepted in general (positive and so so 76%) while most interviewees preferred (89%) unification of certification system dominantly. As unintentional contamination source, pollution on imported row material was indicated as major reason, and other causes were confirmed as insertion during manufacturing process, agricultural by-products using as product additive et al. Based on these surveyed results, authors suggest bellows as considerable methods for effective improvement of management system on organic material. First, establish new integrated certification system which contains standard of quality certification and notification system on organic material. Second, for evaluation of efficacy, apply relative evaluation system of significance such as Duncan's multiple test instead of existing absolute evaluation system. Third, constitute and operate selection of standard comparison subcommittee in organic Agro-materials committee in RDA.

• Steel and Composite Structures
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• 제22권4호
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• pp.875-888
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• 2016

The proper selection of materials for the intended use of the structural member is of particular interest. The paper deals with determining both the mechanical properties at different temperatures and the behavior in tensile creep as well as fatigue testing of tensile stressed specimens made of low alloy 42CrMo4 steel delivered as annealed and cold drawn. This steel is usually used in engineering practice in design of statically and dynamically stressed components. Displayed engineering stress - strain diagrams indicate the mechanical properties, creep curves indicate the material creep behavior while experimental investigations of fatigue may ensure the fatigue limit determination for considered stress ratio. Also, hardness testing provides an insight into material resistance to plastic deformation. Experimentally obtained results regarding material properties were: tensile strength (735 MPa / $20^{\circ}C$, 105 MPa / $680^{\circ}C$), yield strength (593 MPa / $20^{\circ}C$, 76 MPa / $680^{\circ}C$). Fatigue limit in the amount of 532.26 MPa, as maximum stress at stress ratio R = 0.25 at ambient temperature was calculated on the basis of experimentally obtained results. Regarding the creep resistance it is visible that this steel can be treated as creep resistant at high temperatures (including $580^{\circ}C$) when applied stress is of low level (till 0.2 of yield stress).

• 한국세라믹학회지
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• 제50권5호
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• pp.333-340
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• 2013

To fabricate spherical lithium titanate ($Li_2TiO_3$) pebbles which are used for a breeder material in fusion reactor, titanium oxide ($TiO_2$) granules were used as a starting material. The granules were pre-sintered, and then aqueous lithium nitrate solution infiltrated into the granules at vacuum condition. The granules were crystallized to $Li_2TiO_3$ after sintering under the control of process parameters. In this study, the concentration of lithium in the solution, as well as the number of penetration times and sintering temperature affected the final crystallite phase and the microstructure of the pebbles. In particular, the sphericity and size of the pebbles were effectively controlled by a technical rolling process. The useful spherical $Li_2TiO_3$ pebbles which have 10~20% porosity and 60~120 N compressive strength were obtained through the sintering at $1000{\sim}1100^{\circ}C$ in the multi-times infiltration process with 50 wt% solution. The physical properties of pebbles such as density, porosity and strength, can be controlled by a selection of $TiO_2$ powders and control of processing parameters. It can be thought that the lithium penetration method is a useful method for the fabrication of mass product of spherical $Li_2TiO_3$ pebbles.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.101-105
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• 2001

고압용 가교 Polyethylene 절연 케이블의 도체와 절연체 사이, 절연체와 외부 차폐층 사이에는 계면에서의 부분방전을 방지하고 전기적 스트레스를 완화할 목적으로 반도전층이 설계되어 있다. 이 반도전층의 성질은 케이블의 품질과 신뢰성에 매우 중요한 관련이 있다. 일반적으로 반도전층은 압출 성형하는데 Base Polymer에 다량의 카본블랙을 혼합하여 도전화 한다. 절연층과 반도전층간 계면의 평활도는 전력 케이블의 수명과 깊은 관계가 있는데 만약 평활도가 좋지 않으면 전기적 Stress 가 증가하여 전선 수명이 짧아진다. 계면 평활도를 나쁘게 하는 주 요인은 계면의 Void, 반도전층의 돌기와 이물, 탄화물 등이다. 반도전 Compound 제조에 있어서 Carbon Black의 선택과 분산성은 전선수명을 결정하는 중요한 요소이다.

• 한국콘텐츠학회논문지
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• 제13권4호
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• pp.104-114
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• 2013

본 연구는 디지털 방송 환경 하에서 독립제작사 제작 방송 다큐멘터리의 소재 유형을 다양화하고 전문화 함으로써 시청자의 시청 권리를 확대하는데 연구목적을 두고 있다. 이를 위해 독립제작사 제작 방송 다큐멘터리인 <수요기획>(KBS 1TV)의 지난 10년 간 방송분을 분석대상으로 방송 소재를 유형화했다. 연구결과에 의하면, 완전 공모제 방식의 외주제작 방송 다큐멘터리인 <수요기획>의 제작에 국내 대부분의 독립제작사들이 참여했고, 제작규모 면에서 영세한 독립제작사들이 완전 공모제 방식을 적극 활용해 제작해 온 것으로 나타났다. 방송 소재 유형을 9가지로 분류해 분석한 결과, 시사 소재 유형이 33.4%, 휴먼 소재 유형이 18.5%를 차지하고 있었으며 독립제작사의 수익 극대화를 위해 연작 형식이 채택되기도 한 것으로 분석되었다. 방송 다큐멘터리의 소재 유형화 과정을 분석한 본 연구는 독립제작사의 방송 다큐멘터리 소재 선정의 유형을 체계적으로 분석했다는데 연구의의를 찾을 수 있다.

• 한국건축시공학회지
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• 제18권1호
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• pp.41-49
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• 2018

본 연구는 고강도, 고유동의 성질을 갖고, 시공 후 수축현상이 저감되어 균열발생을 저감시킬 수 있는 바닥모르타르 배합선정에 관한 연구로서, 최적배합을 선정하기 위한 배합시험과 선정된 배합의 압축강도, 휨강도, 플로, 길이변화성능 및 염화물침투 저항성, 내화학성 등의 성능시험을 실시하였다. 시험결과, 유동성과 조기강도 발현이 가능하며, 수축저감을 통하여 균열발생 위험성을 개선시킬 수 있을 것이라 판단되는 배합을 선정하였으며, 선정된 배합은 자기수평모르타르 규격에 만족하는 성능을 확보하는 것으로 확인되었다. 본 연구의 결과를 통하여 우수한 재료성능과 경제성, 시공성을 갖는 고성능, 고유동의 바닥모르타르 시공기술을 확보할 예정이다.