• Korean Journal of Optics and Photonics
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• v.6 no.2
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• pp.148-155
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• 1995

The low loss single-mode $Al_{0.042}Ga_{0.958}As/GaAs/Al_{0.042}Ga_{0.958}As$ strip-loaded waveguides had been designed using an effective index method and fabricated using a MOCVD technique and chemical wet etching method. The propagation loss and facet reflectivity were measured by the Fabry-Perot resonance method and sequential cleaving experiment at $1.31{\mu}m$ wavelength. As a result, the propagation loss is as low as 0.62 dB/cm and the facet refiectivity(R) equals to 0.299 for straight waveguides with width $ w=4.1{\mu}m$..

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.385-388
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• 2008

Recycled fine aggregate has low quality because it contains large amount of old mortar. So, its usage is limited to a lower value-add, such as the roadbed material etc. Also, alkaline water occurred from treatment process of the waste concrete is becoming the cause of environmental problem. Accordingly, this study is to develop on the high quality recycled fine aggregate produced by low speed wet abraser using sulphuric. We investigated the properties of compressive strength of the mortar which was manufactured using recycled fine aggregate containing calcined gypsum produced by earlier mentioned process. Test results indicate that concrete using recycled fine aggregate containing calcined gypsum is higher compressive strength than concrete using other sands.

• Applied Biological Chemistry
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• v.29 no.1
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• pp.90-95
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• 1986

A comparative study of chemical characteristics, efficacy and relative merits of extruded and coated granules, containing fungicide and insecticide, was conducted under laboratory and field conditions. Probenzole (3-allyloxy-1,2-benzisothiazole 1,1-dioxide) and carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methyl carbamate) were chosen as toxicants for rice blast(Pyricularia oryzae) and brown planthopper (Nilaparvata lugens) control, respectively. Stability of active ingredients in coated granule was superior to the extruded one under accelerated temperature. Active ingredient dissolution of coated one into distilled water showed slow release pattern. Pesticide residues in rice (Oryzae sativa, Chucheongbyeo) shoot applied with extruded one at the dosage of 3kg/10a retained higher levels than those with coated one on two days after application, while the residue levels were a reversed tendency on eight days after application. Efficacy on rice blast exhibited minute differences between the granules, on the other hand efficacy on brown planthopper by coated one was of higher rank than that by extruded one. Production cost of the combined pesticide granule by coating method could be cut down by 6% as compared to extrusion method.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.257.1-257.1
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• 2015

Cu(In,Ga)Se2 (CIGS) 박막 태양 전지에서 buffer layer는 CIGS 흡수층과 TCO 사이의 밴드갭 차이에 대한 문제점과 lattice mismatch를 해결하기 위해 필수적이다. 흔히 buffer layer 물질로는 CdS가 가장 많이 사용되고 있으나 Cd의 독성에 관한 문제가 야기되고 있다. 따라서 ZnS(O, OH) buffer layer가 친환경 물질로 기존의 CdS 버퍼 층의 대체 물질로 각광 받고 있으며, 단파장 범위에서 높은 투과율로 인해 wide band gap의 Chalcopyrite 태양 전지에 응용되는 buffer layer로 많은 연구가 이루어지고 있다. 또한 buffer layer를 최적화 하여 carrier lifetime과 양자 효율이 증가시킬 수 있는 특성을 가지고 있다. 이 연구에서는 Cu(In,Ga)Se2 (CIGS) 박막에 화학습식공정 (CBD) 방법을 이용하여 최적화된 ZnS(O, OH)의 증착 조건을 찾고, 고품질의 buffer layer를 제조하기 위한 실험에 초점을 맞췄다. 또한, buffer layer의 막질을 개선하고 균일한 막을 제조하기 위해 processing parameters인 시약의 농도, 제조 시간 및 온도 등의 다양한 변화를 통해 실험을 진행하였다. 그 후 최적화된 ZnS(O, OH) buffer layer의 특성 분석을 위해 X-ray diffraction(XRD), photoluminescence (PL), scanning electron microscope (SEM) and GD-OES을 이용하였고, 이를 통해 제조된 CIGS 박막 태양전지는 light induced current-voltage (LIV) and external quantum efficiency (EQE)를 통해 특성 분석을 실시 하였다. 결과적으로, 제조된 ZnS(O, OH) buffer layer의 $ZnSO4{\cdot}7H2O$의 농도는 0.16 M, Thiourea는 0.5 M, NH4OH는 7.5 M, 그리고 반응 온도는 77.5 oC의 조건 하에 CIGS 기판 위에 균일하고 균열이 없는 ZnS(O, OH) 박막을 제조하였으며 이때 제조된 태양전지의 소자 특성은 Voc = 0.478 V, Jsc = 35.79 mA/cm2, FF = 47.77%, ${\eta}=8,18 %$이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.31-31
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• 2000

Al2O3는 높은 화학적, 열적 안정성으로 인하여 미세전자 산업에서 절연막이나 광전자소자의 재료로써 널리 이용되고 있다. 특히, 사파이어는 고위도의 LED, 청색 LD의 재료인 GaN 계열의 III-Nitride 물질을 성장시킬 때 필요한 기판으로 보편적으로 사용되고 있다. 이러한 GaN계열의 광소자 제조에서 사파이어 기판을 적용시 지적되는 문제점들 중의 하나는 소자제조 후 사파이어의 결정 구조 및 높은 경도에 의해 나타나는 cutting 및 backside의 기계적 연마가 어렵다는 것이다. 최근에는 이온빔 식각이나 이온 주입 후 화학적 습식 시각, reactive ion etching을 통한 사파이어의 건식 식각이 소자 분리 및 backside 공정을 우해 연구되고 있다. 그러나 이러한 방법을 이용한 사파이어의 식각속도는 일반적으로 15nm/min 보다 작다. 높은 식각율과 식각후 표면의 작은 거칠기를 수반한 사파이어의 플라즈마 식각은 소자 제조 공정시 소자의 isolation 및 lapping 후 연마 공정에 이용할 수 있다. 본 연구에서는 평판 유도결합형 플라즈마를 이용하여 Cl2/BCL3/Ar 의 가스조합, inductive power, bias voltage, 압력, 기판온도의 다양한 공정 변수를 통하여 (0001) 사파이어의 식각특성을 연구하였다. 사파이어의 식각속도는 inductive power, bias voltage, 그리고 기판 온도가 증가할수록 증가하였으며 Cl2에 BCl3를 50%이하로 첨가할 때 BCl3 첨가량이 증가할수록 식각속도 및 식각마스크(photoresist)와의 식각선택비가 증가하는 것을 관찰하였다. 또한, Cl3:BCl3=1:1의 조건에 따라 Ar 첨가에 따른 식각속도 및 표면 거칠기를 관찰하였다. 본 연구의 최적 식각조건인 40%Cl2/40%BCl3/20%Ar, 600W의 inductive power, -300V의 bias voltage, 30mTorr의 압력, 기판온도 7$0^{\circ}C$에서 270nm/min의 사파이어 식각속도를 얻을수 있었다. 그리고 이러한 식각조건에서 표면의 거치기를 줄일수 있었다. 사파이어 식각은 보편적인 사파이어 lapping 공정시 수반되어 형성된 표면의 거치기를 줄이기 위한 마지막 공정에 응용될수 있다. 사파이어의 식각시 나타나는 식각 부산물은 플라즈마 진단방비인 optical emission spectroscopy (OES)를 통하여 관찰하였고, 식각시 사파이어의 표면성분비 변화 및 표면의 화학적 결합은 X-ray photoelectron spectroscopy(XPS)를 사용하여 측정하였다. 시각 전, 후의 표면의 거칠기를 scanning electron microscopy(SEM)을 통하여 관찰하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.135-139
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• 2014

The hydride vapor phase epitaxy (HVPE) grown GaN samples to precisely measure the surface characteristics was applied to a molten KOH/NaOH wet chemical etching. The etching rate by molten KOH/NaOH wet chemical etching method was slower than that by conventional etching methods, such as phosphoric and sulfuric acid etching, which may be due to the formation of insoluble coating layer. Therefore, the molten KOH/NaOH wet chemical etching is a better efficient method for the evaluation of etch pits density. The grown GaN single crystals were characterized by using X-ray diffraction (XRD) and X-ray rocking curve (XRC). The etching characteristics and surface morphologies were studied by scanning electron microscopy (SEM). From etching results, the optimum etching condition that the etch pits were well independently separated in space and clearly showed their shape, was $410^{\circ}C$ and 25 min. The etch pits density obtained by molten KOH/NaOH wet chemical etching under optimum etching condition was around $2.45{\times}10^6cm^{-2}$, which is commercially an available materials.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.485-488
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• 2008

Recycled fine aggregate has low quality because it contains large amount of old mortar. So, its usage is limited to a lower value-add, such as the roadbed material etc. Also, alkaline water occurred from treatment process of the waste concrete is becoming the cause of environmental problem. Accordingly, this study is to develop on the high quality recycled fine aggregate produced by low speed wet abraser using sulphuric. We investigated the properties of compressive strength of the mortar which was manufactured using recycled fine aggregate containing calcined gypsum produced by earlier mentioned process. Test results indicate that mortar using recycled fine aggregate containing calcined gypsum has lowest compressive strength. It seems that low compressive strength is closely associated with the expansion of the specimen by excessive formation of ettringite.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.599-599
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• 2012

태양광 발전은 태양광의 입사각과 셀 단면이 이루는각도에 따라 출력특성이 변화된다. 따라서 태양의 위치에 따른 출력특성이 바뀌며 이에 의해 발전가능 시간이 변화된다. 더욱이 건재 일체형(BIPV)의 경우 설치 방향을 조절 할 수 없으므로 입사각에 따른 출력특성이 더욱 중요하다. 이와 따라 결정질 태양전지의 입사각에 따른 광학 특성 변화는 태양전지 표면에 형성되는 Texture의 영향을 받는다. 일반적으로 습식 texturing 방법으로는 화학적인 반응을 이용한 WET 공정, 그리고 건식 texturing 방법으로는 플라즈마를 이용한 reactive ion etching (RIE) 공정이 사용된다. 본 연구에서는 RIE, WET 공정을 사용하여 만든 texturing 구조의 결정질 태양전지를 SEM 장비를 이용하여 표면의 형상을 분석하고, 광 입사각에 따른 양자효율의 특성에 대하여 분석하였다.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.9-19
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• 2020

Transferring of functional nanofilms onto target substrates is a cornerstone to developing nanofilm-based nextgeneration applications. In this work, we provide a brief review of recent advances on nanofilm transfer methods by categorizing them into the following three methods: wet-etching transfer, electrochemical delamination, and mechanical transfer. Furthermore, the mechanical transfer method, which is regarded as a promising technology owing to its facile, substrate recyclable, and widely applicable process, is overviewed by focusing on fracture mechanics approaches. Finally, the perspectives and challenges for future development of the mechanical transfer method are discussed.

• Journal of Animal Science and Technology
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• v.47 no.4
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• pp.513-524
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• 2005

This study was conducted to introduce recycling procedures of food waste(FW) as feed according to the dehydration, semi-dehydration fermentation and liquid fermentation methods through the on-site survey of companies related, to trace physico-chemical components and nutritional losses depending upon the processing stage for each method and finally to suggest more desirable methodology for the efficient utilization of FW as animal feed. For the dehydration method, dewatering of FW alone reduced(P<0.05) moisture(approximately 10%) and ether extract contents and increased(P<0.05) fiber contents. Dewatering and subsequent dehydration of FW decreased(P<0.05) contents of ether extract, limiting amino acids such as lysine, methionine and histidine, pepsin digestibility of protein by half, and NaCl content by 40%, increased(P<0.05) contents of fiber, crude ash, Ca and P, and did not alter(P>0.05) pH. The semi-dehydration fermentation method of FW did not affect(P>0.05) the chemical components, pepsin digestibility of protein, pH and NaCl content. For the liquid fermentation method, pasteurization and fermentation of FW decreased(P<0.05) contents of dry matter, ether extract, crude fiber, lysine and NaCl; however, it did not affect(P>0.05) other chemical components, pepsin digestibility of protein and pH. Among the processing methods, nutrient losses were highest for the dehydration method(25% of metabolizable energy loss, 12% of organic matter loss) and little for the semi-dehydration and liquid fermentation methods. The on-site survey of companies related revealed that the existence of foreign materials in FW products were problematic for all the three companies surveyed, thus it was necessary to develop a more efficient screener. Before feeding FW-containing diets to pigs, high quality of protein and energy feedstuffs needed to be fortified for the dehydration method. For the semi-dehydration fermentation method, the scientific diet formulation technology was required at the initial mixing stage. For the liquid fermentation method, possibly most energetic and proteinaceous feeds needed to be supplemented for the normal animal growth.