• 한국전기전자재료학회논문지
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• 제24권1호
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• pp.70-75
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• 2011

We introduced nanoscale interfacial layers between the PV layer and the cathode in poly (3-hexylthiophene):methanofullerene bulk-heterojunction polymer photovoltaic (PV) cells. The nanoscale double interfacial layers were made of ultrathin poly (oxyethylenetridecylether) surfactant and low-work-function alloy-metal of Al:Li layers. It was found that the nanoscale interfacial layers increase the photovoltaic performance, i.e., increasing short-circuit current density and fill factor with improved device stability. For PV cells with the nanoscale double interfacial layers, an increase in power conversion efficiency of $4.18{\pm}0.24%$ was achieved, compared to that of the control devices ($3.89{\pm}0.08%$) without the double interfacial layers.

• 한국세라믹학회지
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• 제20권1호
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• pp.49-54
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• 1983

The main object of this study is to investigate the effect of Al powder as an additive on the sintering of calcined alumina comparing with that of calcined alumina alone. The degree of Al oxidation is calculated by measuring the weight increase during the firing Water absorption bulk density and compressive strength of the $Al_2O_3+Al$ system at each temperature are compared with those of $Al_2O_4$ alone. The $Al_2O_3+Al$ system shows better physical propeties than Al2O3 alone and it seems by the SEM observation that the fine oxidized Al particles(fine $Al_2O_3$ particles submicron unit) fill the interstices of the original $Al_2O_3$ par-ticles and thus result in the well-close-packed arrangement of the particles.

• Journal of Biosystems Engineering
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• 제11권2호
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• pp.55-65
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• 1986

The resistance to the passage of airflow through various agricultural products is an important consideration in the design of an aeration or drying system. The amount of resistance to airflow varied widely from one kind of grain to another, and depended upon airflow rate, surface texture and shape of the particles, the size and configuration of voids, and foreign and fine material in the grain bed. The airflow rate was the major factor considered on this kind of study in the early stages. But these days, the studies on the resistance to airflow of grain affected by grain moisture content and foreign and fine material have been widely carried out. However the foreign an fine material in the grain bed could not be a major factor on the study in Korea because there were only a few grain process procedure after harvesting it. The objectives of this study were to investigate the effect of moisture content and airflow rate on airflow resistance to grain, and to develop a model to predict the static pressure drop across the grain bed as a function of moisture content and airflow rate. The rough rice varieties, Akibare, Milyang 15 (Japonica types), Samkwang, Backyang (Indica types)and covered barley variety, Olbori, which were harvested in 1985 were used in the experiment after cleaning them. Resistances to airflow of grain were investigated at four levels of moisture content (13-25%, wb.) for ten different airflow rates($0.01-0.15m^3/sm^2$). The results of this study are summarized as follows; 1. Theaverage bulk densities were $585.3kg/m^3$ for rough rice and $691.6kg/m^3$ for barley at the loose fill, and were $648.8kg/m^3$ for rough rice and $758.2kg/m^3$ for barley at the packed fill. The pressure drops at the packed fill beds were approximately 1.4 to 1.8 times higher than those at the loose fill beds. 2. The pressure drops across grain beds deceased with the increase of moisture content and increased with airflow rate. The decreasing rates of pressure drop across grain beds according to the moisture contents at the lower airflow rates were higher than those at the higher airflow rates, and the increasing rates of pressure drop according to the airflow rates at the lower moisture contents were higher those at higher moisture contents. 3. The pressure drop across barley bed were much higher than rough rice beds and the pressure drops across Japonica type rough rice beds were a little higher than Indica type. 4. The mathematical models to predict the pressure drop across grain beds as a function of moisture content and airflow rate were developed from these experiments.

• Korean Chemical Engineering Research
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• 제48권5호
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• pp.654-659
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• 2010

박막형 유기 태양전지의 효율 향상을 위하여 정공 수송층인 CuPc 층에 p형 유기 반도체인 rubrene을 함량 별로 도핑하여 ITO/PEDOT:PSS/CuPc: rubrene/CuPc:C60(blending ratio 1:1)/C60/BCP/Al의 이종접합구조를 가지는 p-i-n형 유기 박막형 태양전지 소자를 제조한 후, 유기 태양전지의 전류 밀도-전압(J-V) 특성, 단락 전류($J_{sc}$), 개방 전압($V_{oc}$), 충진 인자(fill factor:FF), 에너지 전환 효율(${\eta}_e$) 등을 측정하고 계산하여 성능 평가를 수행 하였다. 정공 수송층으로 사용된 CuPc 층에 rubrene을 도핑함으로써 에너지 흡수 스펙트럼에서 흡수 강도가 감소하였다. 그러나 CuPc 보다 큰 밴드갭을 가지며 높은 정공 이동도를 가지는 결정성 rubrene의 도핑에 의해 제조된 p-i-n형 유기 박막 태양전지의 성능은 향상 되는 것으로 확인되었다. 제조된 유기 태양전지의 에너지 전환 효율(${\eta}_e$)은 1.41%로 실리콘 태양전지와 비교해서 아직도 성능 향상을 위한 많은 노력이 필요함을 보여 준다.

• 폴리머
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• 제33권3호
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• pp.191-197
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• 2009

박막형 유기 태양전지의 성능 향상을 위하여 정공 수송층인 CuPc 층에 강한 p형 유기 반도체인 $F_4$-TCNQ을 도핑하여 ITO/PEDOT:PSS/CuPc: $F_4$-TCNQ(5wt%)/CuPc:C60 (blending ratio 1 : 1)/C60/BCP/LiF/Al의 이종 접합 구조를 가지는 P-i-n형 유기 박막형 태양전지 소자를 진공증착 장비를 이용하여 제조한 후, 유기 태양전지의 전류 밀도-전압(J-V) 특성, 단락 전류($J_{sc}$), 개방 전압($V_{oc}$), 충진 인자(fill factor: FF), 에너지 전환 효율(${\eta}_e$) 등을 측정하고 계산하여 성능 굉가를 수행하였다. CuPc 층에 $F_4$-TCNQ을 도핑함으로써 에너지 흡수 스펙트럼에서 흡수강도가 증가하였으며, $F_4$-TCNQ가 도핑된 CuPc 박막에서 $F_4$-TCNQ 유기 분자의 분산성 향상, 박막의 표면 균일성, 주입 전류(injection currents) 향상 효과등에 의해서 제조된 p-i-n형 유기 박막 태양전지의 성능이 향상되는 것으로 확인되었다. 제조된 유기 태양전지의 에너지 전환 효율(${\eta}_e$)은 0.15%로 실리콘 태양전지와 비교해서 아직도 성능 향상을 위한 많은 노력이 필요함을 보여 준다.

• Archives of Plastic Surgery
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• 제36권6호
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• pp.714-719
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• 2009

Purpose: Recurrent ischial pressure sore is troublesome for adequate soft tissue coverage, because usually its pocket has a very large deep space and adjacent donor tissue have been scarred in the previous surgery. However, the conventional reconstructive methods are very difficult to overcome them. Modified gluteus maximus myocutaneous V - Y advancement flap from buttock can be successfully used in these circumstances. Methods: From February 2007 to October 2008, modified gluteus maximus myocutaneous V - Y advancement flaps were perfomed in 10 paraplegic patients with recurrent ischial pressure sore. The myocutaneous flap based on the inferior gluteal artery was designed in V - shaped pattern toward the superolateral aspect of buttock and was elevated from adjacent tissue. Furthermore, when additional muscular bulk was required to obliterate dead space, the flap dissection was extended to the inferolateral aspect which can included the adequate amount of the gluteal muscle. After the advanced flap was located in sore pocket, donor defect was repaired primarily. Results: The patients' mean age was 46.9 and the average follow - up period was 12.4 months. The immediate postoperative course was uneventful. But, two patients were treated through readvancement of previous flap due to wound dehiscence or recurrence after 6 months. The long - term results were satisfied in proper soft tissue bulk and low recurrence rate. Conclusions: The modified gluteus maximus myocutaneous V - Y advancement flap may be a reliable method in reconstruction of recurrent ischial pressure sore, which were surrounded by scarred tissue because of its repetitive surgeries and were required to provide sufficient volume of soft tissue to fill the large pocket.

• Korean Journal of Chemical Engineering
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• 제35권12호
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• pp.2496-2503
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• 2018

The short-term stability of high efficiency polymer : nonfullerene solar cells was investigated by employing a quick (ten cycles) current density-voltage (J-V) cycling method. Polymer : nonfullerene solar cells with initial power conversion efficiency (PCE) of >10% were fabricated using bulk heterojunction (BHJ) films of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5,7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T) and 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6/7-methyl)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-M). One set of the BHJ (PBDB-T : IT-M) films was thermally annealed at $160^{\circ}C$ for 30min, while another set was used without any thermal treatment after spin-coating. The quick J-V scan (cycling) measurement disclosed that the PCE decay was relatively slower for the annealed BHJ layers than the unannealed (as-cast) BHJ layers. As a result, after ten cycles, the annealed BHJ layers delivered higher PCE than the unannealed BHJ layers due to higher and more stable trend in fill factor. The present quick J-V cycling method is simple but expected to be useful for the prediction of short-term stability in organic solar cells.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.69.2-69.2
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• 2010

Recently, bulk hetero-junction cells have been extensively studied by many researchers. Most of these cells were fabricated by spin coater. However, the spin coating process is not favorable to the large-scaled industry because it is not compatible with roll-to-roll process. One of the alternative methods is Doctor blading. In this study, we fabricated large OPV cells having total area of $100cm^2$. The buffer layer was Poly-(3,4-ethylenedioxythiophene) : poly-(styrenesulfonate) aqueous dispersion (PEDOT:PSS) and the active material is poly (3-hexythiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) blend in the solvent of Chlorobenzene. All of the organic layers were coated by dragging the blade with a speed of 5~20 mm/s on the stage with a temperature of $50^{\circ}C$. As-bladed PEDOT:PSS layer was baked at $120^{\circ}C$ for 10 minutes to eliminate the water. The cell structure is patterned ITO substrate/PEDOT:PSS/P3HT:PCBM/LiF/Al. The topmost electrode, LiF/Al, was deposited by thermal evaporation. After depositing electrode, and the cell was annealed at $150^{\circ}C$ for 30 minutes. The measured ISC, VOC, fill factor, and PCE were 2.95 A, 5.86 V, 0.32, and 0.78%, respectively. PCE was quite low but the large active area could be obtained successfully.

• Geomechanics and Engineering
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• 제9권4호
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• pp.447-464
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• 2015

Millions of scrap tires are discarded annually in Turkey. The bulk of which are currently landfilled or stockpiled. These tires consume valuable landfill space or if improperly disposed, create a fire hazard and provide a prolific breeding ground for rats and mosquitoes. Used tires pose both a serious public and environmental health problem which means that economically feasible alternatives for scrap tire disposal must be found. Some of the current uses of scrap tires are tire-derived fuel, creating barrier reefs and as an asphalt additive in the form of crumb rubber. However, there is a much need for the development of additional uses for scrap tires. One development the creation of shreds from scrap tires that are coarse grained, free draining and have a low compacted density thus offering significant advantages for use as lightweight subgrade fill and backfill material. This paper reports a comprehensive laboratory study that was performed to evaluate the use of a shredded tire-sand mixture as a backfill material in trench conditions. A steel frame test tank with glass walls was created to replicate a classical trench section in field conditions. The results of the test demonstrated that shredded tires mixed with sand have a definite potential to be effectively used as backfill material for buried pipe installations.

• Steel and Composite Structures
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• 제37권5호
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• pp.551-569
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• 2020

Vibration of vertically aligned-monolayered-nonuniform nanorods consist of functionally graded materials with elastic supports has not been investigated yet. To fill this gap, the problem is examined using the elasticity theories of Eringen and Gurtin-Murdoch. The geometrical and mechanical properties of the surface layer and the bulk are allowed to vary arbitrarily across the length. The nonlocal-surface energy-based governing equations are established using differential-type and integro-type formulations, and solved by employing the Galerkin method by exploiting admissible modes approach and element-free Galerkin (EFG). Through various comparison studies, the effectiveness of the EFG in capturing both nonlocal-differential/integro-based frequencies is proved. A constructive parametric study is also conducted, and the roles of nanorods' diameter, length, stiffness of both inter-rod's elastic layer and elastic supports, power-law index of both constituent materials and geometry, nonlocal and surface effects on the dominant frequencies are revealed.