• 동력기계공학회지
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• 제21권5호
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• pp.5-12
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• 2017

With the difficulties in increasing the efficiency of conventional crank-driven compressors due to mechanical loss, compressor manufacturers have investigated new kinds of compressor such as a free piston compressor mechanism. This study investigates the energy efficiency of two different types of compressor for a household refrigerator. One is the conventional crank-driven compressor, and the other one is a linear compressor. The energy efficiencies of these compressors are evaluated. Experimental results show that the linear compressor has 10% lower power consumption than the brushless direct-current (BLDC) reciprocating compressor. The linear compressor demonstrates excellent energy efficiency by reducing the friction loss. Furthermore, a motor efficiency exceeding 90% is achieved by using a linear oscillating mechanism with a moving magnet. Additionally, the compressor stroke to piston diameter ratio of the oscillating piston in the linear compressor can be adjusted in order to modulate the cooling capacity of the compressor for improved system efficiency.

• Asian-Australasian Journal of Animal Sciences
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• 제20권4호
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• pp.605-614
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• 2007

Feeding pigs used to be a means of managing domestic resources that may otherwise have been wasted into valuable animal protein. Feeding pigs thus was a form of husbandry. Following recent rapid industrial development, pig rearing has changed from extensive to intensive, but this transformation has been associated with major concerns. The concentration of large amounts of pig manure in small arrears is environmentally hazardous. Moreover, high densities of animals in intensive production systems also impose a health threat for both animals and humans. Furthermore, the use of growth promoters and preventive medicines for higher production efficiencies, such as in-feed antibiotics, also induces microbial resistance thus affects human therapeutics. In addition, consumers are questioning the ethics of treating animals in intensive production systems. Animal welfare, environmental and bio-safe issues are re-shaping the nature of pig production systems. Feeding pigs thus involves not only the consideration of economic traits, but also welfare traits and environmental traits. Thus, a focus on technological feasibility, environmental sustainability and social desirability is essential for successful feeding operations. Feeding pigs now involves multiple projects with different sustainability goals, but goal conflicts exist since no pattern or scenario can fulfill all sustainability goals and the disagreements are complicated by reduced or even no use of in-feed antibiotics. Thus it is difficult to feed pigs in a manner that meets all goals of high quality, safe product, eco- and bio-sustainability, animal welfare and profit. A sustainable pig production system thus requires a prioritization of goals based on understanding among consumers, society and producers and needs to view from both a local and global perspective.

• 한국가축번식학회지
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• 제17권1호
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• pp.43-48
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• 1993

These experiments were carried out to construct mouse testis cDNA library and to to seen H-Y Ag gene. Mouse testis was obtained from BALB/c inbreed mouse that was after-born 1 week. Isolation of mouse testis total RNA was carried out by guanidum/cesium choloride, poly(A+) mRNAs were purified by oligo d(T)-cellulose chromatography method. To investigate protein synthesis activity, in-vitro translation carried out by total RNA and poly(A+) mRNA. The products of in-vitro translation were identified in 12.5% PAGE. Single strand DNA and double strand DNA were synthesized from poly(A+) mRNA and purified using phenol/chloroform/isoamylalcohol. Synthesized cDNA was combined with cohesive Eco RI polylinker, its recombination efficiencies were identified by X-gal and IPTG. In the cDNA library, 1$\times$107 phagemids were screened with 32P labelled probe. Hybridization were carried on $65^{\circ}C$ for 16~20hours. And 1$\times$106 phagemids were screened with rabbit-anti-H-Y. In former, select 5 positive clones, and later, 1 positive clone. Its southern blot analysis showed various size of insert cDNA from 0.7kb to 3kb.

• Elastomers and Composites
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• 제55권3호
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• pp.215-221
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• 2020

Silica/SBR (styrene-butadiene rubber) compounds are the primary constituents of tire treads. Furthermore, the excellent dynamic viscoelastic properties of silica lead to good fuel efficiencies. However, the silanol group on the surface of silica does not mix well with non-polar rubber because of its polarity. This incompatibility causes aggregation due to the occurrence of hydrogen bonding between the hydroxyl groups, thereby reducing the dispersibility of silica. Recently, the wet master batch (WMB) process has been applied to overcome these disadvantages, and research on silica dispersants that can be used in the WMB process has been increasing. In this study, we prepared silica/SBR compounds by using three types of eco-friendly cellulose-based dispersants in the WMB process, namely: cellulose-, sodium carboxymethyl cellulose, and nanocellulose-based dispersants. Subsequently, we compared the vulcanization characteristics, viscoelastic properties, and mechanical properties of the compounds. The silica dispersibility in the rubber compounds was improved with the addition of the nano-cellulose dispersant, resulting in the enhancement of the workability, hardness, tensile strength, and wear resistance of the SBR compound.

• 전력전자학회논문지
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• 제19권1호
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• pp.57-63
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• 2014

In this paper a bidirectional DC-DC converter is proposed for renewable energy systems, eco-friendly vehicles, energy storage systems, uninterruptible power supply(UPS) systems and battery test equipments. The two-stage bidirectional converter employing a fixed-frequency series loaded resonant converter is designed to be capable of operating under zero-current-switching turn on and turn off regardless of voltage and load variation, and hence its magnetic components and EMI filters can be optimized. And efficiencies and volumes of the two-stage bidirectional converters are compared according to configuration of isolated and non-isolated parts and a two-stage topology suitable for low voltage and high current applications is proposed. A 12kW(12V, 1000A) prototype of the proposed converter has been built and tested to verify the validity of the proposed operation.

• 한국분말재료학회지
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• 제28권2호
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• pp.150-163
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• 2021

Interest in eco-friendly materials with high efficiencies is increasing significantly as science and technology undergo a paradigm shift toward environment-friendly and sustainable development. MXenes, a class of two-dimensional inorganic compounds, are generally defined as transition metal carbides or nitrides composed of few-atoms-thick layers with functional groups. Recently MXenes, because of their desirable electrical, thermal, and mechanical properties that emerge from conductive layered structures with tunable surface terminations, have garnered significant attention as promising candidates for energy storage applications (e.g., supercapacitors and electrode materials for Li-ion batteries), water purification, and gas sensors. In this review, we introduce MXenes and describe their properties and research trends by classifying them into two main categories: transition metal carbides and nitrides, including Ti-based MXenes, Mo-based MXenes, and Nb-based MXenes.

• 한국습지학회지
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• 제9권1호
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• pp.69-78
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• 2007

Constructed wetlands and other aquatic systems have been successfully used for waste and wastewater treatment in either temperate or tropical regions. To treat waste or wastewater in a sustainable manner, the integrated eco-engineering designs are explained in this paper with 2 case studies: (i) a combination of vertical-flow constructed wetland (CW) with plant irrigation systemfor fecal sludge management and (ii) integrated CW units with landscaping at full-scale application for domestic wastewater treatment. The pilot-scale study of fecal sludge management employed 3 vertical-flow CW units, each with a dimension of $5{\times}5{\times}0.65m$ (width ${\times}$ length ${\times}$ media depth) and planted with cattails (Typha augustifolia). At the solid loading rate of 250 kg total solids (TS)/$m^2.yr$ and a 6-day percolate impoundment, the CW system could achieve chemical oxygen demand (COD), TS and total Kjeldahl nitrogen (TKN) removal efficiencies in the range of 80 - 96%. The accumulated sludge layers of about 80 - 90 cm was found at the CW bed surface after operating the CW units for 7 years, but no clogging problem has been observed. The CW percolate was applied to 16 irrigation Sunflower plant (Helianthus annuus) plots, each with a dimension of $4.5{\times}4.5m$ ($width{\times}length$). In the study, the CW percolate were fed to the treatment plots at the application rate of 7.5 mm/day but the percolate was mixed with tap water at different ratio of 20%, 80% and 100%. Based on a 1-year data of 3-crop plantation were experimented, the contents of Zn, Mn and Cu in soil of the experimental plots were found to increase with increasing in CW percolate ratios. The highest plant biomass yield and oil content of 1,000 kg/ha and 35%, respectively, were obtained from the plots fed with 20% or 50% of the CW percolate, whereas no accumulation of heavy metals in the plant tissues (i.e. leaves, stems and flowers) of the sunflower is found. In addition to the pilot-scale and field experiments, a case study of the integrated CW systems for wastewater treatment at Phi Phi Island (a Tsunami-hit area), Krabi province, Thailand is illustrated. The $5,200-m^2$ CW systems on Phi Phi Island are not only for treatment of $400m^3/day$ wastewater from hotels, households or other domestic activities, but also incorporating public consultation in the design processes, resulting in introducing the aesthetic landscaping as well as reusing of the treated effluent for irrigating green areas on the Island.

• 전기화학회지
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• 제7권1호
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• pp.38-43
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• 2004

전기화학적으로 이온을 흡착시켜 제거시키는 capacitive deionization(CDI) 공정용 전극으로 탄소에어로젤에 실리카젤이 첨가된 다공성 탄소에어로젤 복합전극을 사유하여 1,000ppm NaCl수용액에서 10회와 100회 동안 싸이클을 변화시켜 탈염과 재생 특성에 대한 충전과 방전 시 시간에 따른 전류변화, 싸이클에 대한 전하량 변화, 그리고 CDI효율을 조사하였다. Paste rolling법으로 제조된 탄소에어로젤 복합전극은 CDI반응진행에 대한 전극 활물질의 탈락이 없이 전극의 성형성이 크게 향상되었고, 전극시트 제조시간을 $50\%$ 이상 단축시킬 수 있었다. 10분동안 충전과 방전으로 10회 싸이클까지의 전하량 결과를 살펴보면, $50wt.\%$의 실리카젤이 첨가된 C복합전극의 평균 충전 전하량이 실리카젤이 첨가되지 않은 A전극에 비해 $3\%$ 증가하였으며, 평균 방전 전하량은 $7\%$증가하였다. 5분동안 충전과 방전으로 100회 싸이클까지 평균 충전 전하량을 보면 $25w1.\%$와 $50wt.\%$의 실리카젤이 첨가된 B복합전극과 C복합전극은 A전극에 비해 각각 $6\%,\;14\%$증가하였으며, 또한 평균 방전 전하량도 각각 $9\%,\;21\%$증가하여 복합전극의 전하량 특성이 매우 우수하였다. 100회 싸이클까지의 CDI효율은 싸이클이 진행되면서 $70\%$ 이상으로 안정하게 유지하였고, 100회 싸이클에서는 B 복합전극이 $72.3\%$, C 복합전극이 $74.0\%$로 A 전극$(63.1\%)$보다 $10\%$이상 우수한 CDI 효율을 나타내었다.

• 한국토양비료학회지
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• 제45권2호
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• pp.317-324
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• 2012

비점오염원 저감을 위해 설치된 주암호 생태습지의 수질정화효율을 평가하기 위하여 시스템별 및 시기별 오염물질의 함량과 처리효율을 조사하였다. 유입원수의 BOD, COD, SS, T-N 및 T-P의 함량은 각각 0.20~0.91, 1.24~8.00, 0.6~8.6, 0.04~2.50 및 $0.001{\sim}0.685mg\;L^{-1}$ 범위로 나타났다. 주암호 생태습지 유입수의 대부분이 현행 오염물질 수질기준을 초과하지 않은 상태로 유입되었지만 비점오염원이 많이 유입되는 특정 시기 (장마철)에는 높은 오염물질 함량을 나타내었다. 시기별로는 전반적으로 여름철에 유입원수의 영양염류의 유입이 다른 시기에 비해 높은 경향이었다. 전반적으로 C 시스템이 오염물질의 처리효율이 가장 높은 경향이었다. A 시스템의 습지들은 대부분 겨풀이 우점하고 있었으며 B 시스템의 습지들은 겨풀과 연꽃이 우점하고 있었다. C 시스템의 습지들은 겨풀, 수련 및 부들이 우점하고 있었다. 주암호 생태습지는 오염물질의 처리능이 전반적으로 안정화 상태에 도달하지 못한 것으로 판단되며, 특히 겨풀 및 물 참새피 등 식물교란종의 습지 내 침투로 인하여 습지의 수질정화효율이 전반적으로 낮았다. 따라서 본 연구결과로부터 조성초기 인공습지는 식생의 발달 여부가 수질의 안정화와 습지의 수생태학적 역할을 증대시키는데 중요한 역할을 하는 것으로 판단된다.

• 공업화학
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• 제31권1호
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• pp.7-12
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• 2020

충북의 북부지역에서 한약재 부산물로서 황기 줄기가 대량 생산되고 있으나, 이러한 부산물들은 특별한 수요처가 없이 밭에 폐기물로 버려지고 있다. 본 연구에서는 이 폐기물을 재활용하고자, 황기 줄기를 사용하여 바이오차를 제조하였다. 이 바이오차를 사용하여 물속에 용해된 카드뮴과 망간 이온의 제거특성을 고찰하였다. 50과 100 mg/L 카드뮴 이온을 처리하기 위하여 흡착 평형 실험이 이루어졌을 때, 카드뮴의 제거효율은 각각 100과 95%를 나타내었다. 또한, 50과 100 mg/L 망간 이온을 제거하기 위하여 5 h의 반응이 이루어졌을 때, 각각 36.1과 37.9 mg/g 최대 흡착량을 얻을 수 있었다. 위의 실험 결과, 카드뮴과 망간 이온의 제거공정에서 황기 줄기 바이오차는 활성탄보다 4배 이상의 흡착량을 나타내었다. 그리고 황기 줄기 바이오차와 활성탄 표면의 화학 구조를 관찰하기 위하여 X-ray photoelectron spectroscopy (XPS)를 분석한 결과, 황기 줄기 바이오차는 활성탄과 비교하여 산소 함량과 O/C의 비율이 각각 2.1과 2.4배 증가함을 알 수 있었다. 또한, 망간 이온의 제거능력을 향상시키기 위하여 온도 변화에 의한 운전이 이루어졌으며, 45 ℃로 4 h에서 흡착 평형에 도달하였으며 50과 100 mg/L 망간 이온은 각각 92, 53%의 제거효율을 나타내었다. 결과적으로 이러한 실험 결과들은 물속에 용해된 카드뮴과 망간 이온을 친환경적이며 경제적으로 처리하는 새로운 제거 기술에 유용하게 사용될 수 있을 것이다.