• Tribology and Lubricants
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• 제30권5호
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• pp.291-294
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• 2014

Multiple additives can help improve the performance of generally used lubricants. These additives include MoS2, cadmium, chloride, indium, sulfide, and phosphide, which are harmful to both humans and the environment. Thus, researchers in this industry have been trying to reduce the use of these additives by finding alternatives. Nanodiamonds are one of these candidates. Nanodiamond particles are very hard, chemically stable, and highly heat-conductive. This research involved uniformly dispersing nanodiamond particles in marine engine oils via a matrix synthesis method at various concentrations (0, 0.1, 0.3, 0.5, and 1.0 wt). Friction and wear tests involved constant loads on ball-on-disk specimens, where the ball was AISI 51200 steel, the disk was AISI 1020 steel, and the sliding speed was 0.217 m/s. The lowest wear occurred at a suitable concentration of nanodiamonds (0.3 wt). However, excessive amounts of nanodiamonds caused them to act as abrasive debris because of their hardness, which increased the wear amount. The friction coefficient decreased as the nanodiamond concentration increased because their octagonal, almost spherical shape caused them to act as rolling contact elements between two surfaces.

• 농촌의학ㆍ지역보건
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• 제31권1호
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• pp.63-79
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• 2006

Korea's self-sufficient food ratio on a quantity basis remained a low 27.6 per cent for cereals in year 2004. Even the public auction of imported rice from the United States kicked off a couple of days ago to allow foreign rice to be sold directly to consumers on the Korea market for the first time. Therefore the safety of imported food must be a great concern of Korean consumers. All imported agricultural products are supposed to be quarantined for controlling the insect and inspected for the potent risk like residual pesticides, aflatoxin, sulfur dioxide and genetically modified. agricultural products. The 12 percent of agricultural products contained the insects detected by National Plant Quarantine was fumigated with methyl bromide or aluminum phosphide and entered the custom. The most large portion of violated agricultural products (24 cases in 2004) inspected by Korea Food and Drug Administration was dried herbal medicinal foods contaminated by sulfur dioxide which must be treated when they were dried in China. The second factor made the imported agricultural products to be criminals (19 cases in 2004) was residual pesticides. Genetically modified agricultural products like soybean and corn are under control by labelling in Korea. Genetically modified soybean and corn have been used for oil expression mostly. It is the time to set up realistic risk assessment system for our consumer with the pouring imported agricultural products.

• 한국전기전자재료학회논문지
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• 제11권1호
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• pp.12-17
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• 1998

The heteroepitaxial growth of InP and GaInAs on GaAs substrates has been studied by using a new combination of source materials: ethyldimethylindium (EDMIn) and trimethylgallium (TMGa) as group III sources, and tertiarybutylarsine (TBAs) and tertiarybutylphosphine (TBP) as group V sources. Device quality InP heteroepitaxial layers were obtained by using a two-step growth process under atmospheric pressure, involving a growth of an initial nucleation layer at low temperature followed by high temperature annealing and the deposition of epitaxial layer at a growth temperature. The continuity and thickness of nucleation layer were important parameters. The InP layers deposited at 500$^{\circ}$- 55$0^{\circ}C$ are all n-type, and the electron concentration decreases with decreasing TBP/EDMIn molar ratio. The excellent optical quality was revealed by the 4.4 K photoluminescence (PL) measurement with the full width at half maximum (FWHM) of 4.94 meV. Epitaxial Ga\ulcorner\ulcorner\ulcornerIn\ulcorner\ulcorner\ulcornerAs layers have been deposited on GaAs substrates at 500$^{\circ}$ - 55$0^{\circ}C$ by using InP buffer layers. The composition of GaInAs was determined by optical absorption measurements.

• 한국진공학회지
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• 제12권4호
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• pp.251-256
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• 2003

분자선에피탁시법을 이용하여 InP(001) 기판위에 성장한 InAlAs 에피층의 특성에 대한 성장온도 (370-$430 ^{\circ}C$)의 효과를 Normalski 현미경, 원자력현미경 (AFM), 광발광 (PL), 이중결정 x-선 회절법 (DCXRD)을 사용하여 분석하였다. InAlAs 에피층의 표면형상, 구조적, 광학적 특성은 370-$400^{\circ}C$에서 성장한 시료에서는 성장온도의 증가로 향상되지만, $430 ^{\circ}C$로 성장한 시료에서는 특성이 나빠졌다. 결과적으로 $400 ^{\circ}C$로 성장한 InAlAs 에피층의 특성이 가장 우수하였다.

• 환경위생공학
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• 제7권2호
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• pp.129-140
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• 1992

Rats and Cockroaches are the most problematic pests of our living environment, Rats generally fall under three categories, namely, the Norway rats, the roof rats and the mouses, Among these three types, the roof rats are increasing rapidly in number and their habitats are spreading quickly in the city area, where as the Norway rats are decreasing both in number and habitat. There are numerous damages that these pests create in our society, The rat induce damages to computers and other information processing equipments, sometimes cause light-out, and other financial losses and other sanitary problems. The cockroaches, apart from inducing serious sanitary problems, is an insect that creates insectophobia. decently, it has been revealed that cockroaches are also the main carriers of allergic diseases. Among the pesticides employed against rats in Korea, Beta - fluoro acetate(1080) was initially used after the National Liberalization. Later, the Korean government imported anticoagulant rodenticide for its control. This was followed by a brief, unsuccessful utilization of Zinc Phosphide. Since the begin of 1980s, with the advent of pest control companies, first generation anticoagulant rodenticide were developed in Korea and recently followed by a widespread use of pesticide that utilizes second generation anticoagulant material, the "Brodifacoum" . Among insecticides employed against cockroaches, "Fenitrothion" "Dusban" "DDVP" "Diazinon" and others have been used. They were gradually being replaced by the use of synthesised pyrethroid insecticides until recently. Today there is a wide spread use of bait poisons, the "hydramethylnon" Nevertheless, full prevention and control can not be realized with the sole use of the pesticides. In the future, hygine and proofing, combined with affective pest management, must be incorporated in order to bring about more satisfactory and fruitful preventive measures.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.280-280
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• 2010

Semiconductor quantum dots are of great interest for both fundamental research and industrial applications due to their unique size dependant properties. The most promising application of colloidal semiconductor nanocrystals (quantum dots or QDs) is probably as emitters in biomedical labeling, LEDs, lasers etc. As compared to II-VI quantum dots, III-V have attracted greater interest owing to their less ionic lattice, larger exciton diameters and reduced toxicity. Among the III-V semiconductor quantum dots, Indium Phosphide (InP) is a popular material due to its bulk band gap of 1.35 (eV) which is responsible for the photoluminescence emission wavelength ranging from blue to near infrared with change in size of QDs. Nevertheless, in recent years, the exact type of collective properties that arise when semiconductor quantum dots (QDs) are assembled into two- or three-dimensional arrays has drawn much interest. The term "uantum dot solids" is used to indicate three-dimensional assemblies of semiconductor QDs. The optoelectronic properties of the quantum dot solids are known to depend on the electronic structure of the individual quantum dot building blocks and on their electronic interactions. This paper reports an efficient and rapid method to produce highly luminescent and monodisperse quantum dots solution and solid through fabrication of InP thin films. By varying the molar concentration of Indium to Ligand, QDs of different size were prepared. The absorption and emission behaviors were also studied. Similar measurements were also performed on InP quantum dot solid by fabricating InP thin films. The optical properties of the thin films are measured at different curing temperatures which show a blue shift with increase in temperature. The dielectric properties of the thin films were also investigated by Capacitance-voltage(C-V) measurements in a metal-insulator-semiconductor (MIS) device.

• ETRI Journal
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• 제43권5호
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• pp.909-915
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• 2021

GaAs on Si grown via metalorganic chemical vapor deposition is demonstrated using various Si substrate thicknesses and three types of dislocation filter layers (DFLs). The bowing was used to measure wafer-scale characteristics. The surface morphology and electron channeling contrast imaging (ECCI) were used to analyze the material quality of GaAs films. Only 3-㎛ bowing was observed using the 725-㎛-thick Si substrate. The bowing shows similar levels among the samples with DFLs, indicating that the Si substrate thickness mostly determines the bowing. According to the surface morphology and ECCI results, the compressive strained indium gallium arsenide/GaAs DFLs show an atomically flat surface with a root mean square value of 1.288 nm and minimum threading dislocation density (TDD) value of 2.4×10⁷ cm^-2. For lattice-matched DFLs, the indium gallium phosphide/GaAs DFLs are more effective in reducing the TDD than aluminum gallium arsenide/GaAs DFLs. Finally, we found that the strained DFLs can block propagate TDD effectively. The strained DFLs on the 725-㎛-thick Si substrate can be used for the large-scale integration of GaAs on Si with less bowing and low TDD.

• 대한금속재료학회지
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• 제48권2호
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• pp.122-132
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• 2010

Higher strength and fracture toughness of reactor pressure vessel steels can be obtained by changing the material specification from that of Mn-Mo-Ni low alloy steel (SA508 Gr.3) to Ni-Mo-Cr low alloy steel (SA508 Gr.4N). However, the operation temperature of the reactor pressure vessel is more than $300^{\circ}C$ and the reactor operates for over 40 years. Therefore, we need to have phase stability in the high temperature range in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel. It is very important to evaluate the temper embrittlement phenomena of SA508 Gr.4N for an RPV application. In this study, we have performed a Charpy impact test and tensile test of SA508 Gr.4N low alloy steel with changing impurity element contents such as Mn and P. And also, the mechanical properties of these low alloy steels after longterm heat treatment ($450^{\circ}C$, 2000hr) are evaluated. Further, evaluation of the temper embrittlement by fracture analysis was carried out. Temper embrittlement occurs in KL4-Ref and KL4-P, which show a decrease of the elongation and a shifting of the transition curve toward high temperature. The reason for the temper embrittlement is the grain boundary segregation of the impurity element P and the alloying element Ni. However, KL4-Ref shows temper embrittlement phenomena despite the same contents of P and Ni compared with SC-KL4. This result may be caused by the Mn contents. In addition, the behavior of embrittlement is not largely affected by the formation of $M_3P$ phosphide or the coarsening of Cr carbides.

• Advances in Energy Research
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• 제8권4호
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• pp.223-231
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• 2022

An ex-situ gravitational fixed bed pyrolysis reactor was used over Al₂O₃ supported Ni₂P based catalyst with various Ni/P molar ratios (0.5-2.0) and constant nickel loading of 5.37 mmol/g Al₂O₃ to determine the hydrodeoxygenation of rubberwood sawdust (RWS) at atmospheric pressure. The 3D catalysts formed were characterized structurally as well as acidic properties were determined by hydrogen-temperature programmed reduction (TPR). The Ni₂P phase formed completely on Al₂O₃ for 1.5 Ni/P ratio, although lesser crystallite sizes of Ni₂P were seen at Ni/P ratios less than 1.5. Additionally, it was shown that when nickel loading level increased, acidity increased and specific surface area dropped, probably because nickel phosphate is not easily converted to Ni₂P. When Ni/P ratio was 1.5, Ni₂P phase fully formed on Al₂O₃. The catalytic activity was explained in terms of impacts of reaction temperature and Ni/P molar ratio. At relatively high temperature of 450℃, the high-value deoxygenated produce was predominantly composed of n-alkanes. Based on the findings, it was suggested that hydrogenolysis, hydrodeoxygenation, dehydration, decarbonylation, and hydrogenation are all part of mechanism underlying hydrotreatment of RWS. In conclusion, the synthesized Ni₂P/ Al₂O₃ catalyst was capable of deoxygenating RWS with ease at atmospheric pressure, primarily resulting in long chained (C₉-C₂₄) hydrocarbons and acetic acid.

• 대한수의학회지
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• 제22권2호
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• pp.221-232
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• 1982

This paper dealt with the pathological and clinical findings on the experimentally induced rodenticide (fluoroacetate, zinc phosphide, thallium sulfate, coumarin) and NaCN poisoning of ruminants (Holstein cattle and/or Korean native goat) for the purpose of the diagnosis in the accidental rodenticide poisoning of cattle. The results observed are summarized as follows: Fluoroacetate poisoning (cattle and goat): in the clinical signs, there were depression, convulsion, dyspnea, groan, grinding of the teeth, vomiting, opisthotonus and post-mortem tympany. In the macroscopical findings, the blood was more or less poor coagulative and dark red, bloody fluid with foam in the trachea, hyperemia and hemorrhage of tracheal mucosa and lung, cloudy swelling and hyperemia of kidney, epicardial hemorrhage(cattle), and hyperemia of abomasum, intestine and brain were observed. In the microscopical findings, there were pulmonary edema and hemorrhage, necrosis of convoluted tubular epithelium and interstitial hemorrhage of kidney, focal coagulative necrosis of myocardium, hemorrhage of pancreas and spleen, dilatation of Virchow-Robin space and hyperemia of brain, and necrosis with desquamation of mucosal epithelia of abomasum and upper small intestine. In the histological lesions of the liver, lobular peripheral hyperemia, centrilobular necrosis and cytoplasmic inclusion bodies of the hetatic cells were observed. The cytoplasmic inclusion body of the hepatic cells was not seen in the affected goat, but hydropic degeneration of the hepatic cells was marked. Zinc phosphide poisoning (cattle and goat): clinically, the affected animals died in recumbent position after ataxia, dyspnea and convulsion. In the macroscopical findings, hyperemia and hemorrhage of lung, cloudy swelling and hyperemia of liver and kidney, hemorrhage of spleen (cattle), and catarrh of abomasum and small intestine were observed. In the microscopical findings, necrosis of the convoluted tubular epithelium and hyperemia of kidney, hemorrhage of spleen, hyperemia of lung, hyperemia or hemorrhage of heart, cloudy. swelling and fatty changes of hepatic cells, dilatation of hepatic central vein, hyperemia of brain, and catarrh of abomasal and small intestinal mucosae were observed. Thallium sulfate poisoning (cattle): in the macroscopical findings dark red color of blood, hyperemia and hemorrhage of lung, bloody fluid with foam in the tracheal mucosa, petechiae of tracheal mucosa, cloudy swelling and hemorrhage of liver, necrotic lesions and hemorrhage of renal cortex and epicardial hemorrhage were observed. In the microscopical findings, severe hemorrhages of the lung, cloudy swelling and necrosis of hepatic cells, hyperemia and hemorrhage of liver, focal coagulative necrosis of mycordium, necrosis of the convoluted tubular epithelium and hyperemia of kidney, hyperemia and hemorrhage of spleen and dilatation of Virchow-Robin apace in brain were observed. Coumarin poisoning (goat): the poisoned animals died in the state of groan and depression. In the macroscopical findings, poor coagulation of blood, hemorrhage of lung, cloudy swelling and severe hemorrhages of liver, cloudy swelling and hemorrhage of kidney, abomasal hemorrhage, catarrh of small intestine, and hyperemia and hemorrhage of the other organs were observed, In the microscopical findings, hyperemia and hemorrhage of lung and kidney, cloudy swelling of the convoluted tubular epithelium of kidney, severe hepatic hyperemia, cloudy swelling and hydropic degeneration of heptatic cell, and hyperemia and hemorrhage of brain and spleen were observed. NaCN poisoning (cattle and goat): clinically, there were convulsion, severe dyspnea, paresis of hind limb, depression and then rigor of four limbs. In the macroscopical findings, bright red color of blood, hyperemia and bright and red tinge of lung cloudy swelling of kidney and liver, and hyperemia of abomasum were observed. In the microscopical findings, cloudy swelling and hydropic degeneration of hepatic cell, hyperemia and edema of lung, necrosis and degeneration of the convoluted tubular epithelium and hemorrhage in kidney, dilatation of Virchow-Robin space of brain and hemorrhage of spleen were observed.