• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.484.2-484.2
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• 2014

There are many efforts to improving the power conversion efficiencies (PCEs) of dye-sensitized solar cells (DSCs). Although DSCs have a low production cost, their low PCE and low thermal stability have limited commercial applications. This study describes the preparation of a novel multifunctional polymer gel electrolyte in which a cross-linking polymerization reaction is used to encapsulate $TiO_2$ nanoparticles toward improving the power conversion efficiency and long-term stability of a quasi-solid state DSC. A series of liquid junction dye-sensitized solar cells (DSCs) was fabricated based on polymer membrane encapsulated dye-sensitized $TiO_2$ nanoparticles, prepared using a surface-induced cross-linking polymerization reaction, to investigate the dependence of the solar cell performance on the encapsulating membrane layer thickness. The ion conductivity decreased as the membrane thickness increased; however, the long term-stability of the devices improved with increasing membrane thickness. Nanoparticles encapsulated in a thick membrane (ca. 37 nm), obtained using a 90 min polymerization time, exhibited excellent pore filling among $TiO_2$ particles. This nanoparticle layer was used to fabricate a thin-layered, quasi-solid state DSC. The thick membrane prevented short-circuit paths from forming between the counter and the $TiO_2$ electrode, thereby reducing the minimum necessary electrode separation distance. The quasi-solid state DSC yielded a high power conversion efficiency (7.6/8.1%) and excellent stability during heating at $65^{\circ}C$ over 30 days. These performance characteristics were superior to those obtained from a conventional DSC (7.5/3.5%) prepared using a $TiO_2$ active layer with the same thickness. The reduced electrode separation distance shortened the charge transport pathways, which compensated for the reduced ion conductivity in the polymer gel electrolyte. Excellent pore filling on the $TiO_2$ particles minimized the exposure of the dye to the liquid and reduced dye detachment.

• Tribology and Lubricants
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• 제40권2호
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• pp.61-66
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• 2024

Micro-plastics are synthetic high-differentiation chemicals of less than 5mm in size, and are deposited not only on the sea surface but also on the coast. If these micro-plastics are not properly separated from the sand, they can threaten marine ecosystems. Thus, in the present study, we aimed to apply cyclone separator to the micro-plastic retrieval in order to predict the movement of particles according to the formation of the cyclone separator by applying the centrifugal force of the particle in accordance with the rotational movement of the air. The cyclone separator has three shapes, the first one is a typical interconnected cyclone separator. The second is the horn form, except for the cylinder in a regular cyclone separator, and the third is a form that increases the horn's height twice in the second. The numerical analysis simulation of the Cyclone separator used the Fluent software package. The output speed of the Cyclone separator was 5 to 13m/s at 1m/s intervals. The simulated particles include sand, Styrofoam, PET, PP, and PU. Sand particles are assigned a fixed diameter of 2mm, while other particles have a diameter of 3mm. As a result of the analysis, the first form was not separated from plastic. The Styrofoam separation efficiency in the second showed its highest efficiency at 72.7% at 7m/s, and the efficiency decreased after 12m/s as the sand particles were mixed into the plastic attachment location. In the third form, the separation efficiency of Styrofoam at 12m/s was highest at 67.9%.

• 자원환경지질
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• 제52권1호
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• pp.1-12
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• 2019

금속 폐기물과 TPH(total petroleum hydrocarbon: 석유계 총탄화수소)로 복합 오염된 토양을 정화하기 위하여 자력선별법을 연계한 토양세척 배치실험을 실시하였다. 오염토양의 아연과 TPH 농도는 각각 1743.3 mg/kg과 3558.9 mg/kg으로 심하게 오염되어 있었으며, 아연, 납, 구리, TPH 항목들이 '2지역 토양오염우려기준'(정화목표)을 초과하였다. 중금속 제거를 위해 1차 산세척을 실시하였으나 납과 아연은 산세척 후에도 '2지역 토양오염우려기준'을 초과하였으며, 2차 연속 세척에 의해서 아연과 납의 제거효율은 각각 8 %와 5 % 증가에 그쳐, 정화목표에 도달하지 못하였다. 오염토양의 중금속 초기농도를 줄이고 세척 효과를 높이기 위하여 세척 전 미세입자(직경 < 0.075 mm)를 선별하였으며, 오염토양의 4.1 %가 분리되었다. 미세입자 선별만으로 오염토양의 초기 아연과 납 농도는 1256. 3 mg/kg(27.9 % 감소)과 325.8 mg/kg(56.3 % 감소)으로 감소하였으나, 미세입자 선별 후 오염토양을 1차 세척한 결과 아연 농도가 '2지역 토양오염우려기준'보다 높게 나타나, 이를 만족시킬 수 있는 추가 제거방법이 필요하였다. 본 토양이 무분별한 금속폐기물 투기에 의해 오염되었다는 사실로부터, 미세입자 선별의 대안으로 자력선별법을 적용하였으며, 토양의 16.4 %가 자력선별에 의해 제거되었다. 자력선별 후 오염토양의 아연과 납 농도는 637.2 mg/kg (63.4 % 감소)과 139.6 mg/kg (81.5 % 감소)로 감소하여, 1회 토양세척과 미세입자 선별에 의한 중금속 제거 효과보다 높았다. 자력선별 후 오염토양을 산용액으로 1차 세척한 결과, 오염토양 내 모든 중금속과 TPH농도가 '2지역 토양오염우려기준'이하로 낮게 유지되어, 본 오염토양과 같이 금속폐기물을 많이 함유하고 있는 토양의 경우 자력선별법을 연계한 토양세척에 의해 중금속과 TPH를 동시에 효과적으로 제거할 수 있는 것으로 나타났다.

• 상하수도학회지
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• 제16권6호
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• pp.655-662
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• 2002

Separation characteristics of inorganic particles occurred during heavy rainwater were investigated in DAF (dissolved air flotation) process. In order to remove the inorganic particles effectively, the collision and flotation efficiencies were examined from a hydrodynamic point of view. Generally, the collision efficiency increased with floc size under the variation of fluid dynamic conditions including inertial force. However, more precise model should be required to analysis the collision efficiency expressed both the physical properties for inorganic particles and hydrodynamic conditions for a reactor.

• 전기학회논문지
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• 제67권6호
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• pp.724-729
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• 2018

This paper presented an evaluation method for the efficiency uncertainty of an inverter-fed three-phase induction motor using FEM. The motor efficiency in the FEM is calculated by the IEC 60034-2-3 as in the actual test. In the process of evaluating the efficiency uncertainty, the difference between the finite element method and the actual test is the method of calculating the type-A / B standard uncertainty of the input quantity to estimate the efficiency and each losses. For the input quantities which can confirm the instantaneous values with respect to time, the type-A standard uncertainty in the FEM is calculated from the RMS values or average values having separate periods in the steady state. And, the type-B standard uncertainty in the finite element method is assumed to be zero. Also, this paper compared and analyzed the efficiency uncertainty evaluated by the proposed method and the efficiency uncertainty through the actual test.

• 한국전산유체공학회지
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• 제8권2호
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• pp.24-32
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• 2003

In this work, we propose a new idea of flapping airfoil design for optimal aerodynamic performance from detailed computational investigations of flow physics. Generally, flapping motion which is combined with pitching and plunging motion of airfoil, leads to complex flow features such as leading edge separation and vortex street. As it is well known, the mechanism of thrust generation of flapping airfoil is based on inverse Karman-vortex street. This vortex street induces jet-like flow field at the rear region of trailing edge and then generates thrust. The leading edge separation vortex can also play an important role with its aerodynamic performances. The flapping airfoil introduces an alternative propulsive way instead of the current inefficient propulsive system such as a propeller in the low Reynolds number flow. Thrust coefficient and propulsive efficiency are the two major parameters in the design of flapping airfoil as propulsive system. Through numerous computations, we found the specific physical flow phenomenon which governed the aerodynamic characteristics in flapping airfoil. Based on this physical insight, we could come up with a new kind of airfoil of tadpole-shaped and more enhanced aerodynamic performance.

• 오토저널
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• 제3권2호
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• pp.18-26
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• 1981

The purpose of this paper is to study the possibility of practical use of gasoline-methanol mixed fuel as an alternative fuel of gasoline engines in the light of engine performances and harmful exhaust emissions as well as mixings and separations of the mixed fuels. When the methanol of 99.8% purity is mixed with super or regular gasoline available on the market today, the experimental results obtained without modifying carburetor in this study are as follows; 1.The separation ratio depends upon the gasoline-methanol mixing ratio only, regardless of fuel temperature and fuel additives for preventing separation of phase. 2.The critical absorption ratio is affected by the gasoline-methanol mixing ratio, its temperature and the quantity of fuel additives. 3.Concerning the distillation temperature, the initial point of all sorts of fuels is almost same,but 10% point and 35-60% point of mixed fuels are lower than those of gasoline only. 4.In case of throttle valve opening set, engine output using the mixed fuels is decreased compared to gasoline, but thermal efficiency is increased as a consequence of decreasing specific energy consumption. 5.In case of fixed load test, thermal efficiency is increased at low engine speed even under low part-load as well as under comparatively high part-load including full load. 6.CO and NOx emissions are reduced remarkably with the mixed fuels.

• 한국콘텐츠학회논문지
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• 제9권10호
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• pp.444-450
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• 2009

본 연구는 폐 활성슬러지를 이용하여 $Pb^2+$와 $Cr^2+$의 생체흡착속도 및 평형을 도출하였으며, 가압부상법이 이용하여 A/S 비에 따른 폐슬러지의 분리효율을 비교하였다. 흡착량 및 접촉시간은 흡착평형과 동역학 모델식을 이용하여 모사하였다. 폐 활성슬러지상에서 $Pb^2+$와 $Cr^2+$의 흡착평형은 Langmuir와 Redlich-Peterson식에 의해 잘 예측될 수 있었다. 흡착속도는 유사 1차 반응식보다는 유사 2차 반응식에 의해 더 잘 예측되었다. 가압부상법을 이용한 폐 활성슬러지의 분리효율은 90%이상 유지하는 것이 가능하였다.

• 멤브레인
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• 제26권1호
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• pp.14-25
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• 2016

분리막 시스템은 기존의 분리공정과 비교하여 우수한 효율과 낮은 가격으로 인하여 빠르게 성장하고 있다. 분리막 공정은 분리막, 모듈, 그리고 기계적 요소로 구성되어 있으며 향상된 효율을 얻기 위하여 분리막 공정에 사용되는 소재의 요구사항 또한 증가가 되고 있다. 분리막 모듈은 분리막 시스템의 핵심 요소 중 하나로써 최근 들어 복합 소재들이 스테인레스강 모듈과 비교하여 우수한 물성과 낮은 가격으로 인해 분리막 하우징에 적용되어 왔다. 본 리뷰에서는 다양한 종류의 유리섬유와 이를 이용한 복합소재들에 대하여 정리하였으며 분리막 시스템에 적용을 위한 잠재성에 대하여 논의하였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권6호
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• pp.357-361
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• 2002

Continuous production of lactic acid from glucose by Lactobacillus rhamnosus with cell recycling using an acoustic cell settler was carried out. The performance of the system, such as the concentration of cell and product were compared with the control experiment without recycling. The acoustic settler showed cell separation efficiency of 67% during the continuous operation and the cell concentration in the fermentor with recycle exceeded that of the control by 29%. Com-pared with the control, tactic acid production was increased by 40%, while glucose consumption was only increased by 8%. The higher value of lactic acid production to substrate consumption (Yp/s, product yield coefficient) achieved by cell recycling is interpreted to indicate that the recycled cell mass consumes less substrate to produce the same amount of product than the control Within system environmental changes due to the longer mean cell residence time induced the cells maintaining the metabolic pathways to produce Less by-Product but more product, lactic acid.