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지열 발전을 위한 HFC-245fa 유기 랭킨 사이클의 성능해석
백영진(YoungJin Baik),김민성(Minsung Kim),장기창(KiChang Chang),윤형기(HyungKee Yoon),이영수(YoungSoo Lee),나호상(HoSang Ra) 한국지열·수열에너지학회 2009 한국지열에너지학회논문집 Vol.5 No.1
In this study, an ORC (Organic Rankine Cycle) is investigated for a low-temperature geothermal power generation by a simulation method. A steady-state simulation model is developed to analyze cycle's performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump are modelled by an isentropic efficiency. Simulations were carried out for the given heat source and sink inlet temperatures, and given flow rate that is based on the typical power plant thermal-capacitance-rate ratio. HFC-245fa is considered as a working fluid of the cycle. Simulation results, at the given secondary working fluids conditions, show that even though the power can be presented by both the evaporating temperature and the turbine inlet superheat, it depends on the evaporating temperature primarily.
A wet-tolerant adhesive patch inspired by protuberances in suction cups of octopi
Baik, Sangyul,Kim, Da Wan,Park, Youngjin,Lee, Tae-Jin,Ho Bhang, Suk,Pang, Changhyun Nature Publishing Group 2017 Nature Vol. No.
<P>Adhesion strategies that rely on mechanical interlocking or molecular attractions between surfaces can suffer when coming into contact with liquids(1,2). Thus far, artificial wet and dry adhesives have included hierarchical mushroom-shaped or porous structures that allow suction or capillarity(3-6), supramolecular structures comprising nanoparticles(7), and chemistry-based attractants that use various protein polyelectrolytes(8-10). However, it is challenging to develop adhesives that are simple to make and also perform well- and repeatedly-under both wet and dry conditions, while avoiding non-chemical contamination on the adhered surfaces(11). Here we present an artificial, biologically inspired, reversible wet/dry adhesion system that is based on the dome-like protuberances found in the suction cups of octopi. To mimic the architecture of these protuberances(12-14), we use a simple, solution-based, air-trap technique that involves fabricating a patterned structure as a polymeric master, and using it to produce a reversed architecture, without any sophisticated chemical syntheses or surface modifications. The micrometre-scale domes in our artificial adhesive enhance the suction stress. This octopus-inspired system exhibits strong, reversible, highly repeatable adhesion to silicon wafers, glass, and rough skin surfaces under various conditions (dry, moist, under water and under oil). To demonstrate a potential application, we also used our adhesive to transport a large silicon wafer in air and under water without any resulting surface contamination.</P>
전단응력 하에서 에멀젼 상 변이의 실시간 측정을 위한 전기 유변학적 연구
백승재 ( Seung Jae Baik ),이영진 ( Youngjin Lee ),남윤정 ( Yoon Sung Nam ),김진한 ( Chin Han Kim ),김한곤 ( Han Kon Kim ),강학희 ( Hak Hee Kang ) 대한화장품학회 2004 대한화장품학회지 Vol.30 No.1
본 연구는 다양한 종류의 에멀젼에 전단응력을 가하며 그때 일어나는 에멀젼의 상 변이를 전기, 유변학적 특징을 통해 실시간으로 측정해보는 것이다. 전기 전도도의 변화는 자체 제작한 JELLI<sup>TM</sup> (Joint Electro-rheometer for Liquid-Liquid Inversion) 칩을 이용하였으며, 동시에 유변물성측정장치(rheometer)를 이용하여 유변물성의 변화를 측정하였다. JELLI<sup>TM</sup> 칩과 인조 피부를 유변물성측정장치 사이에 장착하고 그 사이에 다양한 종류의 에멀젼을 얇게 발라준 후, 일정한 전단응력을 주며 시간에 따른 저항과 전도값의 변화를 측정하였다. O/W 제형의 경우 시간에 따라 저항값이 커지는 경향을 보였으며 저항값은 내부 상이 많을 수록 더 급격한 변화를 나타냈다. 이때의 점도 변화를 보면, 저항값의 변화가 클수록 점도의 변화도 큼을 볼 수 있었다. 이것은 내부 상의 파괴로 인해 외부의 힘에 저항하는 힘이 약해졌기 때문이라고 예상된다. 이런 결과를 이용하여 전단응력에 의한 에멀젼 상 변이 특성과 정도를 실시간, 정량적 비교할 수 있었다. 정량적 비교할 수 있었다. To know what happens to the internal structure of emulsions under high shear flow is very important for cosmetic product development because it is highly relevant to the physical degradation of emulsions during the application upon the skin. Here, in order to investigate the response of emulsions against the external shear forces, we designed a new device, JELLI<sup>TM</sup> (Joint Electro-rheometer for Liquid-Liquid Inversion) chip, for the measurement of electrical and rheological properties of emulsions under shear flow. By using this device, we examined the real-time changes in conductivities of oil-in-water (O/W) and water-in-oil (W/O) emulsions on the artificial skin during large deformation under shear flow. In this study, O/W and W/O emulsions having various volumes were prepared. After emulsions were homogeneously applied on the artificial skin, the electrical resistance and viscosity changes were monitored under steady shear flow. In case of O/W emulsions, the resistance increased as a function of time. The resistance showed more dramatic increase as the increase of the internal oil phase. It was also found that the viscosity change was proportional to the resistance variation. This phenomenon might be caused by decreased resisting forces against the shear flow because of the breakdown of the internal phase.
2단 압축 수열원 열펌프 시스템의 부분부하 운전특성에 관한 연구
이영수(YoungSoo Lee),백영진(YoungJin Baik) 한국지열·수열에너지학회 2009 한국지열에너지학회논문집 Vol.5 No.1
The river water heat source heat pump has the advantage in the performance compared to air source heat pump. In this study, an experimental study on a 2-stage heat pump, which is designed to utilize a river water heat source, were carried out. Generally, a heat pump is designed for maximum capacity rate, but it actually operates at part load condition in most cases. Therefore, an information on the part-load characteristic is very important in view of the system overall performance. In this study, part-load performance tests of a R134a 2-stage compression heat pump were carried out over the river water and supply heating water temperature changes.
Detection of Ions and Radicals Using Single Walled Carbon Nanotubes
Sehun Jung,Seunghyun Baik,Jaeboong Choi,Jongchul Lee,Seunghyun Hong,Youngjin Kim 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.I
Single-walled carbon-nanotube (SWNT) sensors, fabricated by using alternative current dielectrophoresis, were used to detect decomposed ions and radicals in plasma. In this work, we monitored the electrical conductance of the SWNT sensors in argon (Ar) and sulfur hexafluoride (SF$_6$) plasma. Ar and SF$_6$ were decomposed in plasma status. The electrical conductance of the SWNT arrays in Ar plasma increased due to an electronic interaction between SWNT and oxidative decomposed ions. In contrast, the nanotube arrays in SF$_6$ plasma exhibited a drastic decrease in conductance due to the fluorination of the SWNT by decomposed radicals, rather than charge transfer by decomposed ions. These results demonstrate that electronic detection of the decomposed ions and radicals is possible with SWNT sensors.
박성룡(SeongRyong Park),백영진(YoungJin Baik),장기창(KiChang Chang),나호상(Hosang Rha),Huaizhang Tian 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The utilization of unused energy is important because it can afford to offer a chance to increase energy efficiency of a heat pump system. Especially the waste energy recovery by heat pump can be easily utilized in industrial field for processing water supply system. In this article, the efficient way to make a high temperature water by using the waste water as heat source. This article concerns such a cycle that its system making up has the features: a two-stage compression, a two stage expansion and two desorbers, each of which being located after an expansion valve. By comparisons of the performance with those of common two-stage compression and single expansion CAHP systems for four heating cases, the simulation studies showed that the new system has superior performance, under the working conditions of lower compressor outlet temperature and lower maximum system pressure, which is very important for the components of the system to be operated safely. And the performance can be improved further by optimum displacements of the compressors chosen. The simulations also demonstrated how changes of the sink temperature glide, maximum pressure and the performance of the system were adjusted by the circulation rate and the ammonia concentration for a given heat.
Single-walled carbon nanotube sensors for monitoring partial discharge induced dissociation of SF6.
Jung, Sehun,Choi, Jaeboong,Kim, Youngjin,Lee, Jongchul,Chang, Yongmoo,Baik, Seunghyun American Scientific Publishers 2009 Journal of nanoscience and nanotechnology Vol.9 No.12
<P>We proposed to use a miniature single-walled carbon nanotube (SWNT) sensor, fabricated by alternating current dielectrophoresis, to detect dissociated and oxidized sulfur hexafluoride (SF6) gas species generated by partial discharge (PD) activity in a concealed chamber such as gas-insulated switchgear (GIS). The SWNT sensor did not react with pure SF6 gas but sensitively responded to the dissociated and oxidized SF6 species. Also, the SWNT sensor could be regenerated by purging with fresh air since the transduction was based on the physisorption of analytes. Therefore, the SWNT sensor is a promising device for the detection of the dissociated and oxidized SF6 species and for the monitoring of the PD activity inside GIS.</P>
오영석(Youngseok Oh),서대우(Daewoo Suh),김영진(Youngjin Kim),최재붕(Jaeboong Choi),백승현(Seunghyun Baik) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Conductive polymers, prepared by mixing electrically conductive fillers with a suitable polymeric formulation, are widely used in applications such as interconnecting materials for high density electronic packaging. However, resins of conductive pastes used as binders and vehicles are generally nonconductive, so that they may prevent the electrical contact between conductive fillers and reduce electron transmission. In this study, we improved conductivity of silver paste by the incorporation of cabon nanotubes. It is important to achieve homogeneous dispersion of CNTs to act as reinforcements efficiently in matrix. We carried out acid treatment on nanotubes for their homogeneous dispersion in silver/conducting polymer matrix. The dispersion states of nanotubes were characterized by raman spectra and filed emission scanning electron microscope. The electrical resistivity of CNTs incorporated silver paste was also measured by 4-point probe method.