• ETRI Journal
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• 제41권6호
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• pp.811-819
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• 2019

We propose a substrate with high thermal conductivity, manufactured by the low-temperature co-fired ceramic (LTCC) multilayer circuit process technology, as a new DC/DC converter platform for power electronics applications. We compare the reliability and power conversion efficiency of a converter using the LTCC substrate with the one using a conventional printed circuit board (PCB) substrate, to demonstrate the superior characteristics of the LTCC substrates. The power conversion efficiencies of the LTCC- and PCB-based synchronous buck converters are 95.5% and 94.5%, respectively, while those of nonsynchronous buck converters are 92.5% and 91.3%, respectively, at an output power of 100 W. To verify the reliability of the LTCC-based converter, two types of tests were conducted. Storage temperature tests were conducted at -20 ℃ and 85 ℃ for 100 h each. The variation in efficiency after the tests was less than 0.3%. A working temperature test was conducted for 60 min, and the temperature of the converter was saturated at 58.2 ℃ without a decrease in efficiency. These results demonstrate the applicability of LTCC as a substrate for power conversion systems.

• 대한기계학회논문집B
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• 제20권1호
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• pp.266-274
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• 1996

An experimental work was conducted to investigate the characteristics of the onset of flooding in vertical annuli with a direct injection mode using air and water. The onset of flooding was determined by means of pressure drop measurement while the air velocity was increased gradually under fixed liquid flow rates. Data of the onset of flooding were collected for various combinations of the tube size and the nozzle number. A theoretical analysis of the onset of flooding was also performed based on an envelope theory. The result shows that the onset of flooding in small-scale annuli can be predicted relatively well by the theory. A modified Wallis parameter was used to investigate the scaling effect of flooding phenomena in the annuli, indicating a relatively reasonable result. The number of nozzle has no effect on the flooding velocity when liquid was injected through 2, 3, 4 and 6 nozzles but the initiation of flooding was significantly expedited when 12 nozzles were employed for liquid injection.

• 한국환경복원기술학회지
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• 제15권1호
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• pp.35-51
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• 2012

The vascular plants in Bukhansan Dulegil, Jingwan-dong Wetland and Bukhan-dong Cheolgeoji were listed 432 taxa (8.9% of all 4,881 taxa of vascular plants); 95 families, 274 genera, 345 species, 2 subspecies, 69 varieties and 16 forms. Divided into woody plants were 145 taxa (33.6%) and herbaceous plants were 287 taxa (66.4%). The Bukhansan Dulegil were listed (Myeongsang-gil 159 taxa, Huingureum-gil 227 taxa, Wooyiryeong-gil 216 taxa, Banghakdong-gil 139 taxa, Boru-gil 199 taxa), Jingwan-dong Wetland were listed 147 taxa and Bukhan-dong Cheolgeoji were listed 129 taxa. Based on the list of rare plants by Korea Forest Service and Korea National Arboretum were Viola albida Palibin (Violaceae), Iris minutiaurea Makino (Iridaceae) and Korea National Arboretum were endemic plants, Philadelphus schrenkii Rupr. var. schrenkii (Saxifragaceae), Weigela subsessilis L.H. Bailey (Caprifoliaceae). Based on the list of floristic regional indicator plants by Korean Ministry of Environment were total 22 taxa; Wisteria floribunda DC. for. floribunda in class IV, 3 taxa (Betula davurica Pall., Mukdenia rossii Koidz., Glechoma grandis Kuprian., etc.) in class III, 5 taxa (Acer triflorum Kom., Viola orientalis W. Becker, Heloniopsis koreana Fuse & Al., etc.) in class II and 13 taxa (Camptosorus sibiricus Rupr., Clematis patens C. Morren & Decne., Cirsium pendulum Fisch. ex DC., etc.) in class I. Based on the list of naturalized plants, 16 families, 35 genera, 37 species, 3 varieties, 1 form, total 41 taxa (Rumex crispus L., Abutilon theophrasti Medicus, Panicum dichotomiflorum Michx. etc.), naturalization rate was 9.5% of all 432 taxa of vascular plants and urbanization index was 13.3% of all 309 taxa of naturalized plants. Ecosystem disturbing wild plants were 5 taxa; Rumex acetocella L., Ambrosia artemisiifolia L., Ambrosia trifida L. var. trifida, Eupatorium rugosum Houtt., Aster pilosus Willd.

• 한국의류학회지
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• 제25권8호
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• pp.1524-1535
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• 2001

The purpose of this study was to establish a sizing system according to size and dimension whereby manufactured pants can be classified and develop men’s formal pants pattern based on the analysis of ready-made and educational pants pattern. The first, we surveyed the sizing and the basic pants patterns of the men’s ready-made wear companies, Secondly, through the survey data of the domestic men’ready-mad clothing industry, we proposed a new sizing system. Lastly, after compared three different types of ready-mad pants manufactured according to their patterns and an additional type of pants made after the educational pattern, the new men’s basic pants pattern were developed. The findings were as follows: 1. Survey of the domestic ready-mad garment industry showed that each company classified its own manufactured goods according to its own sizing system: moreover, they each used its own unique patterns which appeared to be resulted from a combination of two factors : the experience of a patterner and foreign know-how technology. 2. New sizing system was developed with 12 steps from size 74-88 to size 96-106 based on the high frequencies of the companies’3. New basic patterns for men’s formal pants were developed: Inseam length = 80cm, crotch line = H/4+4.6cm, pants ham = 23.5cm as basic lines and front waist girth =W/4+9.1cm as drafting line. 4. the superiority of the new basic patterns were been demonstrated by a high approval rate of the subjects who participated in testing.

• International Journal of Automotive Technology
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• 제6권2호
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• pp.183-190
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• 2005

During normal operating conditions, a motor vehicle is constantly subjected to a variety of forces, which can adversely affect its straight-ahead motion performance. These forces can originate both from external sources such as wind and road and from on-board sources such as tires, suspension, and chassis configuration. One of the effects of these disturbances is the phenomenon of vehicle lateral-drift during straight-ahead motion. This paper examines the effects of road crown, tires, and suspension on vehicle straight-ahead motion. The results of experimental studies into the effects of these on-board and external disturbances are extremely sensitive to small changes in test conditions and are therefore difficult to guarantee repeatability. This study was therefore conducted by means of computer simulation using a full vehicle model. The purpose of this paper is to gain further understanding of the straight-ahead maneuver from simulation results, some aspects of which may not be obtainable from experimental study. This paper also aims to clarify some of the disputable arguments on the theories of vehicle straight-ahead motion found in the literature. Tire residual aligning torque, road crown angle, scrub radius and caster angle in suspension geometry, were selected as the study variables. The effects of these variables on straight-ahead motion were evaluated from the straight-ahead motion simulation results during a 100m run in free control mode. Examination of vehicle behavior during straight-ahead motion under a fixed control mode was also carried out in order to evaluate the validity of several disputable arguments on vehicle pull theory, found in the literature. Finally, qualitative comparisons between the simulation results and the test results were made to support the validity of the simulation results.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.27-27
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• 2010

최근에 고유가와 지구온난화로 인하여 에너지가 향후 인류의 50년을 좌우할 가장 큰 문제로 대두되고 있어서 지구의 모든 에너지의 근원인 태양광을 이용하는 태양광 발전은 무한한 청정 에너지로 각광받고 있다. 빛을 흡수하여 전기에너지로 변환하는 태양전지는 풍력, 수소연료전지, 조력, 바이오에탄올 등의 신재생에너지 기술 중에서 상품성은 가장 뛰어나지만 발전단가가 가장 높은 것이 단점이다. 태양광 발전단가를 줄여서 기존의 화석에너지를 이용한 발전단가와 견줄 수 있는 그리드 패러티(grid parity)를 달성하려면 태양전지 모듈의 고효율화와 동시에 저가화가 반드시 이루어져야 한다. 현재 태양광 모듈 시장의 90%는 효율이 12-16% 정도로 높은 단결정(single crystalline or monocrystalline) 실리콘이나 다결정(polycrystalline or multicrystalline) 실리콘 등의 벌크(bulk)형 결정질 실리콘 모듈이 차지하고 있으나 원재료인 실리콘 웨이퍼의 제조단가의 50%를 차지하고 있어서 저가화가 어렵다. 반면, 원료가스를 분해하여 대면적 기판에 증착하는 박막(thin-film) 실리콘 태양전지의 경우는 차세대 태양전지로 각광받고 있다. 박막 실리콘 모듈은 매우 적은 실리콘 원재료를 소비한다. 단결정이나 다결정 실리콘 웨이퍼의 두께가 $180-250\;{\mu}m$ 정도인 것에 비해서 박막 실리콘의 두께는 $0.3-3\;{\mu}m$ 수준이다. 더불어, 유리, 플라스틱 등의 저가 기판에 저온 대면적 증착이 가능하여 저가양산화에 유리하다. 박막 실리콘 모듈은 벌크형 실리콘 모듈(-0.5%/K) 대비 낮은 온도계수[비정질 실리콘(amorphous silicon; a-Si:H)의 경우 -0.2%/K]와 빛의 세기가 약한 산란광에서도 동작하여 평균발전시간이 증가하므로 외부환경에서 우수한 발전성능을 보이고 있다. 태양전지 모듈은 상온에서의 안정화 효율을 기준으로 가격이 책정되어($/$W_p$) 판매되기 때문에 벌크형 실리콘 모듈에 비해서 박막 실리콘 모듈은 가격대 성능비가 우수하다. 따라서 박막 실리콘 모듈은 벌크형 결정 실리콘 모듈의 대안으로 떠오르고 있으며, 레이저 기술을 이용하여 수려한 투광형 건물일체형(building integrated photovoltaic; BIPV) 모듈을 제작할 수 있는 장점도 있다. 이러한 장점에도 불구하고 기존의 양산화된 단일접합 비정질 실리콘 태양광 모듈은 효율이 6-7%로 낮아서 설치면적 및 설치 모듈의 증가가 성장의 걸림돌이 되고 있다. 박막 실리콘 태양전지의 고효율화를 도모하기 위해서 적층형 탄뎀셀로 양산 트렌드가 변화하고 있다. 이에 적층형 박막 실리콘 태양전지 효율의 한계 및 돌파구에 대해서 논의한다.

• Smart Structures and Systems
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• 제24권4호
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• pp.541-552
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• 2019

Construction development and greenhouse gas emissions have globally required a strategic management to take some steps to stain and maintain the environment. Nowadays, recycled aggregates, in particular ceramic waste, have been widely used in concrete structures due to the economic and environmentally friendly solution, requiring the knowledge of recycled concrete. Also, one of the materials used as a substitute for concrete cement is wollastonite mineral to decrease carbon dioxide (CO2) from the cement production process by reducing the concrete consumption in concrete. The purpose of this study is to investigate the effect of wollastonite on the mechanical properties and durability of conventional composite concrete, containing recycled aggregates such as compressive strength, tensile strength (Brazilian test), and durability to acidic environment. On the other hand, in order to determine the strength and durability of the concrete, 5 mixing designs including different wollastonite values and recovered aggregates including constant values have been compared to the water - cement ratio (w/c) constant in all designs. The experimental results have shown that design 5 (containing 40% wollastonite) shows only 6.1% decrease in compressive strength and 4.9% decrease in tensile strength compared to the control plane. Consequently, the use of wollastonite powder to the manufacturing of conventional structural concrete containing recycled ceramic aggregates, in addition to improving some of the properties of concrete are environmentally friendly solutions, providing natural recycling of materials.

• ALGAE
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• 제36권2호
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• pp.137-146
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• 2021

Intertidal macroalgae are regularly exposed to hypo- or hypersaline conditions which are stressful. However, red algae in New Zealand are generally poorly studied in terms of salinity tolerance. Consequently, two native (Bostrychia arbuscula W. H. Harvey [Ceramiales], Champia novae-zelandiae [J. D. Hooker & Harvey] Harvey [Rhodymeniales]) and one introduced red algal taxon (Schizymenia spp. J. Agardh [Nemastomatales]) were exposed for 5 days in a controlled salt stress experiment to investigate photosynthetic activity and osmotic acclimation. The photosynthetic activity of B. arbuscula was not affected by salinity, as reflected in an almost unchanged maximum quantum yield (F_v/F_m). In contrast, the F_v/F_m of C. novae-zelandiae and Schizymenia spp. strongly decreased under hypo- and hypersaline conditions. Treatment with different salinities led to an increase of the total organic osmolyte concentrations with rising salt stress in B. arbuscula and Schizymenia spp. In C. novae-zelandiae the highest organic osmolyte concentrations were recorded at S_A 38, followed by declining amounts with further hypersaline exposure. In B. arbuscula, sorbitol was the main organic osmolyte, while the other taxa contained floridoside. The data presented indicate that all three red algal species conspicuously differ in their salt tolerance. The upper intertidal B. arbuscula exhibited a wide salinity tolerance as reflected by unaffected photosynthetic parameters and strong sorbitol accumulation under increasing salinities, and hence can be characterized as euryhaline. In contrast, the introduced Schizymenia spp. and native C. novae-zelandiae, which preferentially occur in the mid-intertidal, showed a narrower salinity tolerance. The species-specific responses reflect their respective vertical positions in the intertidal zone.

• 한국광물학회지
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• 제27권1호
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• pp.17-30
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• 2014

폐콘크리트 처리 시 발생하는 시멘트 미분은 $CO_2$ 포집을 위한 광물탄산화 재료로 활용할 수 있다. 이번 연구에서는 폐콘크리트를 활용한 $CO_2$ 포집을 위한 기초연구로 수화시멘트의 수성탄산화 방안과 탄산염광물 형성 특성에 대한 자료를 확보하고자 하였다. 실험을 위해 물 : 시멘트 비를 6 : 4로 하여 28일간 수중 경화하여 시멘트 풀을 제작하고, 첨가제(NaCl과 $MgCl_2$)를 활용한 용출실험과 두 종류의 수성탄산화(직접수성탄산화와 간접수성탄산화)실험을 수행하였다. 용출실험 결과, $Ca^{2+}$ 이온의 용출은 시험된 최대 농도에서 보다 0.1 M NaCl과 0.5 M $MgCl_2$에서 최대로 나타났으며, $MgCl_2$는 NaCl에 비해 10배 이상의 $Ca^{2+}$ 이온을 용출력을 보였다. 미분(< 0.15 mm)의 시멘트 풀은 직접수성탄산화에 의해 1시간 이내에 탄산화에 의해 포트랜다이트가 거의 모두 탄산염 광물로 변화하고, CSH(calcium silicate hydrate)의 분해에 의한 탄산화도 진행되는 것으로 나타났다. 그러나 직접수성탄산화에는 NaCl과 $MgCl_2$와 같은 첨가제가 크게 효율적이지 못하였다. NaCl과 $MgCl_2$를 첨가제로 사용한 용출액에 대한 간접수성탄산화로 100% 순수한 방해석을 생성되었다. $MgCl_2$에 의한 용출액의 경우 탄산화를 위해 알칼리용액 의한 pH의 조절이 필요하였으며, $Mg^{2+}$ 이온의 영향으로 탄산화가 느리게 진행되었다. 수성탄산화 방법과 첨가제의 종류가 생성되는 탄산칼슘광물의 종류와 결정도 영향을 미치는 것으로 나타났다.

• 한국식품영양학회지
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• 제29권5호
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• pp.618-627
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• 2016

쌀음료베이스 개발을 위한 품종별 가공용 쌀의 기초자료 확보를 위해 국내산 쌀 7종(삼광, 일품, 설갱, 안다, 다산1호, 고아미4호, 단미)과 수입쌀 3종(미국쌀, 중국쌀, 태국쌀)을 대상으로 수화, 호화 및 당화 관련 특성을 살펴보았다. 품종별쌀의 수분함량은 11.88~15.26% 범위로 나타났으며, 수분흡수율은 안다, 미국쌀이 가장 높게 나타났다. 수분결합력은 태국쌀이 가장 높았으며, 단미, 고아미4호 및 설갱은 낮은 수분결합력을 나타내었다. 용해도는 10종의 시료 중 단미가 월등히 높은 26.6%를 나타내었으며, 팽윤력은 설갱, 안다, 미국쌀이 유의적으로 높은 수준을 나타냈다(p<0.05). 품종별 쌀가루의 아밀로오스 함량은 고아미4호와 태국쌀이 가장 높은 반면, 단미가 가장 낮았다. RVA를 측정한 결과, 호화온도는 단미와 고아미4호가 각각 $91.6^{\circ}C$와 $78.5^{\circ}C$로 가장 높았고, 그 외 품종은 $68.0{\sim}71.1^{\circ}C$로 나타났다. 최고점도와 최종점도는 다산1호가 가장 높았고, 단미가 가장 낮게 나타났다. 치반점도는 일품과 미국쌀이 낮게 나타나, 노화가 더디게 진행될 것으로 예상되었다. 한편, 쌀, 수침처리 쌀, 건식쌀가루, 습식쌀가루로 가공용 쌀 전처리를 달리하고, 수침시 흡수되는 수분량을 고려하여 물을 첨가하고, 고온용 ${\alpha}$-amylase 처리 후 당화특성을 비교하였다. 당화액의 pH는 일품을 제외한 모든 품종에서 습식쌀가루가 유의적으로 높게 나타났다(p<0.05). 가용성 고형분 함량은 대부분 수침처리한 것보다 수침처리하지 않는 것, 쌀보다는 쌀가루의 효소처리가 더 효과적으로 높게 나타났다. 환원당 함량은 전처리 방법에 따라 수침처리하지 않는 것보다 수침처리한 것, 쌀보다는 쌀가루가 유의적으로 더 높게 나타났다(p<0.05). 색도는 L값의 경우 고아미4호를 제외한 대부분 품종에서 쌀보다 수침처리한 쌀이 낮은 값을 보였다. a값은 수침처리하지 않는 쌀과 습식쌀가루에서 낮은 값을 보였으며, b값은 쌀보다 수침처리한 쌀, 건식쌀가루보다 습식쌀가루가 품종에 따라 다소 차이가 있는 것으로 나타났다(p<0.05). 이러한 연구결과를 종합해 보면, 쌀을 원료로 한 음료베이스 개발을 위해서는 원료곡의 호화, 액화 및 당화에 영향을 주는 여러 가지 인자와 품종별 특성을 고려한 접근이 이루어져야 할 것이다.