• 한국소음진동공학회논문집
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• 제20권10호
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• pp.983-990
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• 2010

Reduction of acoustic loads of space launch vehicles can be achieved by acoustic absorbers satisfying strict cleanness requirements. This limited the use of general porous materials and requires non-porous sound absorbers. Micro-perforated panel absorbers(MPPA) is one of promising sound absorbers satisfying the cleanness requirement for launch vehicles. However, its applicability was limited to low sound pressure levels according to the acoustic impedance model of micro-perforated panels. In this paper the applicability of micro-perforated panel absorbers at high incident sound pressure was investigated in experimental ways. The absorption characteristics of a micro-perforated panel absorber was simulated according to its design variables, e.g., minute hole diameters and aperture ratios. It was shown that optimal design can be readily done by using proposed design charts. Experiments were conducted to measure acoustic properties of the designed micro-perforated panel absorbers. The results showed that acoustic resistance increases rapidly as incident sound pressure level does but change of acoustic reactance can be neglected in a practical point of view. This caused the decrease of peak value of absorption coefficient at high incident sound pressure level, but the amount of reduction can be accepted in practice. The major advantage of the micro-perforated panel absorber(wide absorption bandwidth) was still kept at high sound pressure level.

• 한국지반공학회논문집
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• 제37권5호
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• pp.33-46
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• 2021

2016년 발생한 국내 계기 계측 사상 최대 규모의 경주지진과 2017년 팔레트구조 건축물의 기둥이 파괴되는 등 국내 최대 지진피해가 발생한 포항지진 이후, 국내 모든 시설물에 대한 내진설계기준이 개정되고 있으며 특히, 포항지진 피해사례 조사 도중 미국, 일본, 뉴질랜드 등 주로 강진지역 국가에서 발생하는 액상화 피해가 발견되어 이에 대한 설계기준의 보완도 심도있게 진행되고 있다. 이 연구에서는 최근 개정된 항만 및 어항시설 내진설계기준에서의 액상화 평가방법을 고찰하고 액상화 평가절차에 새롭게 인용된 액상화 가능성 지수(LPI)를 중심으로 적용성 검토를 수행하였다. 이때, 액상화 발생가능한 모래지반을 다양하게 조성하고 이에 대한 케이스별 LPI 값을 산정 비교하였다. 또한, 실제 22개소 항만의 지반자료를 이용하여 지진시 지반응답해석에 기초한 액상화 평가의 수행과 함께 22개소의 LPI 값들을 비교 검토하였다.

• Current Photovoltaic Research
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• 제10권2호
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• pp.56-61
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• 2022

Recently, the expansion of the domestic solar market due to the promotion of eco-friendly and alternative energy-related policies is promising, and it is expected to lead the high-efficiency/high-power module market based on M10 or larger cells to reduce LCOE, 540-560W, M12 based on M10 cells Compared to the existing technology with an output of 650-700W based on cells, it is necessary to secure competitiveness through the development of modules with 600W based on M10 cells and 750W based on M12 cells. For the development of high efficiency/high-power n-type bifacial, it is necessary to secure a lightweight technology and structure due to the increase in weight of the glass to glass module according to the large area of the module. Since the mechanical strength characteristics according to the large area and high weight of the module are very important, design values such as a frame of a new structure that can withstand the mechanical load of the Mechanical Load Test and the location of the mounting hole are required. In this study, a structural analysis design model was introduced to secure mechanical reliability according to the enlargement of the module area, and the design model was verified through the mechanical load test of the actual product. It can be used as a design model to secure the mechanical reliability required for PV modules by variables such as module area, frame shape, and the location and quantity of mounting holes of the structural analysis model verified. A relationship of output drop can be obtained.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.523-534
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• 2010

A hybrid system of soil-nailing and compression anchor is proposed in this paper; the system is composed of an anchor bar (installed at the tip) with two PC strands and a steel bar. After drilling a hole, installing proposed hybrid systems, and filling the hole with grouting material, prestress is applied to the anchor bar to restrict the deformation at the head and/or to prevent shallow slope failures. However, since the elongation rate of PC strand is much larger than that of steel bar, yield at the steel bar will occur much earlier than the PC strand. It means that the yield load of the hybrid system will be overestimated if we simply add yield loads of the two - anchor bar and PC strands. It might be needed to try to match the yielding time of the two materials by applying the prestress to the anchor bar. It means that the main purpose of applying prestress to the anchor bar should be two-fold: to restrict the deformation at the nail head; and more importantly, to maximize the design load of the hybrid system by utilizing load transfer mechanism that transfers the prestress applied at the tip to the head through anchor bar. In order to study the load transfer mechanism in a systematic way, in-situ pullout tests were performed with the following conditions: soil-nailing only; hybrid system with the variation of prestress stresses from 0kN to 196kN. It was found that the prestress applied to the anchor system will induce the compressive stress to the steel bar; it will result in decrease in the slope of load-displacement curve of the steel bar. Then, the elongation at which the steel bar will reach yield stress might become similar to that of PC strands. By taking advantage of prestress to match elongations at yield, the pullout design load of the hybrid system can be increased up to twice that of the soil-nailing system.

• 한국강구조학회 논문집
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• 제22권3호
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• pp.271-280
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• 2010

본 연구에서는 국내 건축 구조용 강재인 SN490 강재를 사용하여 실물 크기의 H형강 보와 기둥으로 구성된 모멘트저항골조의 외부 T자형 용접모멘트접합부를 대상으로 실험을 계획하였다. 실험변수를 용접접근공형상, 접합부 이음 방식, RBS(Reduced Beam section)로 하여 9개의 시험체를 제작하였고, 반복재하 실물대 실험을 수행하였다. 실험에 따른 각 시험체의 파괴형태 및 모멘트-층간변위 관계, 변형률 분포를 나타내었으며, 재료인장 실험을 통하여 실험에 사용된 시험체의 전소성모멘트를 구한 다음 특수모멘트 접합부에 해당하는 시험체를 분류하였다. 각 시험체의 모멘트-층간변위 곡선을 골격곡선과 바우싱거곡선으로 분리하여 내력상승률, 소성배율, 에너지 소산량 등을 나타내었으며 이를 가지고 각 시험체의 소성변형능력을 평가하였다. 실험결과 용접접근공이 제거된 시험체가 기존 용접접근공형상을 가지는 시험체에 비하여 우수한 내진성능을 나타내었고, 보 웨브를 용접과 볼트를 병행하고 전단탭을 전체에 걸쳐 보강 용접한 시험체가 가장 우수한 내진성능을 나타내었다.

• 동의생리병리학회지
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• 제21권2호
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• pp.554-560
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• 2007

This study was aimed to identify the effect of abdominal moxibustion on premenstrual syndrome and dysmenorrhea in university students. The data were collected by using questionnaires from April 25, 2005 to June 20, 2005. The subjects were university students from in the Pusan metropolitan area who had complained of menstrual discomfort. Thirteen students were assigned to the experimental group and fourteen students to the control group. The research design of this study was a nonequivalent control group pretest-posttest design. In the research method pretest were conducted through measurement based on scores of general character, menstrual character, premenstrual syndrome and dysmenorrhea in the experimental group and the control group. Experimentation was conducted by abdominal moxibustion being applied on the kwan-won hole and Ki-hae hole for 25 minutes at a time, three times a week, form the ending of one menstrual cycle to the beginning of the next menstrual cycle were in the experimental group. After treatment was finished, post tests conducted through measurement based on scores of premenstrual syndrome and dysmenorrhea in the experimental group. The control group conducted a point of same time and same measurement with the experimental group. The instruments used in this study MDQ(Menstual Distress Questionnaire) developed by moos(1968) and the VAS(Visual Analogue Scale) developed by Cline(1992). The data were analysed by SPSS/ win 12.0 program with ${\chi}$2-test and t-test to verify identification among subjects' general characteristics and menstrual characteristics. Hypothesis verification was analysed with t-test. The results of the study are as follows: The hypothesis, 'the experimental group who received abdominal moxibustion will decrease premenstrual symptoms more than the control group', was supported (t= -2.121, p=.022). The hypothesis, 'the experimental group who received adbominal moxibustion will decrease dysmenorrhea compared to the control group', was supported (t=-4.424, p=.001). As a result of this study, abdominal moxibustion will be used as a nursing aide to improve and prevent menstrual discomfort of university students who have premenstrual syndrome and dysmenorrhea.

• 한국산학기술학회논문지
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• 제10권9호
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• pp.2402-2408
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• 2009

고장력볼트를 이용한 강부재의 체결에서 모재 및 덮개판의 과대공으로 인한 단면결손이 체결부에서 내하력의 저하가 우려되어 정적 인장시험을 실시하였다. 인장시험을 통하여 구해진 체결부의 파단시 최대하중을 단면결손율 및 설계강도와 비교하여 체결부의 내하력 변화를 파악하였다. 이에 따르면 단면결손율이 클수록 강도저하율이 컸으며 특히, 모재의 단면결손이 덮개판의 단면결손보다 강도저하에 대한 영향이 훨씬 큰 것으로 나타났다. 모재 및 덮개판을 과대공으로 제작한 고장력볼트 체결부는 표준공의 경우보다 내하성능이 다소 저하되었지만 파단시의 최대인장강도는 설계파단강도보다 15%이상 크게 나타났다. 본 연구에서는 과대공으로 제작된 고장력볼트 체결부에서 내하력저하에 미치는 영향이 미미하므로 강부재의 체결시공에 있어 과대공의 허용은 경제성과 효율성의 고취에 기여할 수 있을 것으로 판단되었다.

• 한국지진공학회논문집
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• 제2권4호
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• pp.115-122
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• 1998

고력볼트로서 슬립이 발생치 않도록 설계된 철골모멘트골조의 보 이음부의 내진거동을 반복재하 실물대 실험을 통하여 평가하였다. 예상과는 달리 모메트 접합부가 극한 소성강도에 도달하기 훨씬 이전에 보 이음부의 슬립이 발생하였다 실험을 통하여 관측된 마찰계수는 규준 공칭값의 50-60%에 불과하였다. 그러나 보 플랜지의 열영향부가 파단에 이르기 까지 슬립 이후의 지압거동을 통하여 증가되는 반복하중을 성공적으로 모멘트접합부로 전달하였다. 즉 반복하중 하에서도 보 이음부의 슬립이 곧바로 구조적 일체성의 상실로 이어지지는 않음이 관측되었다 볼토구멍을 공제한 보 플랜지 유효단면적의 전강도에 기준한 전통적 보 이음부 설계법에 의할 경우 모멘트 접합부의 소성강도 발현 이전에 보 이음부의 슬립발생 가능성이 높다 본 연구에서는 역량설계 개념에 기초하여 강진 작용시의 보 이음부의 설계와 관련한 추가 고려사항을 제안하였다.

• 복식문화연구
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• 제20권5호
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• pp.621-634
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• 2012

With comparative analysis of running-type brassieres on the market about suitability for middle-aged women, this study is to provide basic data of running-type brassieres' pattern which is highly suitable. In the pursuit of this purpose, this study carried out wearing experiment targeting 3 middle-aged women with normal body shape which is 85B of chest circumference. The result is as follows. The significant difference was recognized in the breast. The products were rated in order of C>A>B>D, E, F, G>H by the observers, and C>B>D>A>F>E=G>H by the subjects. The significant difference was recognized in the armhole area. The products were ranked in the order of C, D>B, G, E>A, F, H by the observes and D, C>B>G>F>A>H by the subjects. The significant difference was also recognized in 6 categories(14~19) for the torso. According to the overall average values, the products were rated in the order of B, C, D>A, D, F, G by the observers and B=D>C>H>F>G>A>E by the subjects. The overall evaluation exhibited the significant difference. The products were ranked in the order of D>C>E>B>H>A>G>F by both observers and subjects. Therefore it was confirmed that the product D was appropriate in general. To conclude of comparative analysis about 8 kinds of running-type brassieres on the market, the average values of the product C and D in all categories had high marks for each category. The product C was comfortable and capable of covering the breast well, however, a gap was formed in outside-up part. The product D, made from lacy fabric, was very comfortable and well-fitted but there was inconsistency between the mold-cup and the breast shape.

• 대한기계학회논문집B
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• 제23권8호
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• pp.1048-1062
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• 1999

A numerical method and experiments for the aerodynamic design of high performance two-stage axial flow fans was carried out. A vortex ring element method used for the aerodynamic analysis of the propellers was extended to the fan-duct system. Fan Performance and velocity profiles at the fan inlet and outlet are compared with experimental data for the validations of numerical method. Performance test was done based on KS B 6311(testing methods for turbo-fans and blowers). The velocity profile was obtained using a 5-hole pitot tube by the non-nulling method. The two stage axial flow fan configurations for the optimal operation conditions were set by using the experimental results for the single rotating axial flow fan and the single stage axial flow fan. The single rotating axial flow fan showed relatively low efficiency due to the swirl velocities behind rotor exit which produced pressure losses. In contrast, the single stage and the two-stage axial flow fans showed performance improvements due to the swirl velocity reduction by the stator. The peak efficiency of the two stage axial flow fan was improved by 21% and 6%, compared to the single rotating axial flow fan and the single stage axial flow fan, respectively.