• Journal of Information Display
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• 제13권4호
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• pp.139-143
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• 2012

In this study, optical simulation was used to compare three optical structures that could be applied to the typical organic light-emitting diode to increase the outcoupling efficiency. These were spherical scattering particles (treated as Mie scatterers) embedded in the glass substrate, microlenses formed on the glass substrate, and a diffusing layer (DL) with a Gaussian scattering distribution function inserted between the indium tin oxide (ITO) and the glass substrate. It was found that the application of microlens array and that of scattering particles in the glass substrate exhibited similar enhancements in the outcoupling efficiency when the density and the refractive index of the scattering particles were optimized. The DL located at the interface between the glass and the ITO further enhanced the efficiency because it could further extract the trapped light in the waveguide mode. The appropriate combination of these three structures increased the outcoupling efficiency to about 42%, which is much greater than the typical values of 15-20% when there is no optical structure for light extraction.

• 대한기계학회논문집B
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• 제34권11호
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• pp.1005-1013
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• 2010

본 연구는 HCCI 엔진의 운전조건을 고려한 혼합연료의 감압비등 분무제어방법을 평가하기 위하여 수행하였다. 2상영역이 존재하는 혼합연료는 고비점성분의 증발촉진과 함께 연료분무의 급격한 증발을 유도할 수 있는 감압비등분무를 이용함으로써 저온 및 저밀도장에서 혼합기형성과정의 제어가 가능하다. HCCI 엔진은 이러한 분위기조건에서 연료를 조기분사하기 때문에 착화성이 높은 경유와 휘발성이 높은 가솔린성분으로 함유한 혼합연료의 감압비등현상을 이용함으로써 액체연료의 분열, 미립화와 같은 물리적 제어 및 착화연소에 의한 화학적 제어를 실현할 수 있다. 본 연구는 혼합연료의 성분과 몰분율을 주요변수로 설정하여 정적용기 내에 분사된 연료분무의 감압비등현상을 슐리렌 화상 및 Mie 산란광을 촬영한 후, 화상처리과정을 통하여 이루어졌다. 그 결과로 감압비등현상은 비교적 저온 및 저밀도장에서 분무구조가 크게 변화함을 알 수 있었으며, 조기 연료분사시기에서 감압비등분무를 이용한 혼합기형성을 제어함으로써 HCCI 연소에 적용이 가능할 것으로 분석하였다.

• Journal of Astronomy and Space Sciences
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• 제19권2호
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• pp.123-132
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• 2002

다목적 실용위성 1호는 고도 685km, $98^{\circ}$의 궤도 경사각를 가지며, 탑재된 이온층 측정 센서(Ionospheric Measurement Sensor)로 전자 온도와 전자 밀도를 측정하였다. 이 관측 자료로부터 22:50LT인 밤 시간에 $+60^{\circ}~-60^{\circ}$의 저위도 지역에서 자기적으로 안정한 상태(Kp <4)의 계절별 전자 밀도와 전자 온도의 분포를 구하였다. 관측 결과, 전자 온도와 전자 밀도의 분포는 계절과 경도에 따라 변화를 나타냈다. 대체로 전자 밀도는 자기 적도 부근에서 높아지고, 전자 온도는 낮아지는 경향을 보였다. 봄, 가을에는 전자 밀도와 온도 모두 자기 적도를 중심으로 대칭적으로 분포하였다. 그러나 여름에는 전체적으로 북반구 쪽으로 이동하여 전자 밀도의 극대점과 전자 온도의 극소점이 자기 적도 북쪽에 위치하였고, 겨울에는 이와 반대의 변화를 나타냈다. 또한, 각 계절에서 경도에 따라서도 전자 온도와 밀도 분포의 차이를 보였다. 이러한 차이가 생기는 원인은 경도와 계절에 따라 달라지는 F층의 중성 바람이 이온층 플라즈마에 영향을 주는 것에 의해 설명될 수 있다. 이 관측에서 얻은 전자온도와 밀도의 분포는 IRI95모델을 이용해 구한 분포와 차이를 보였다.

• 대한기계학회논문집B
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• 제23권9호
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• pp.1139-1150
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• 1999

The evolution of silica aggregate particles in coflow diffusion flames has been studied experimentally using light scattering and thermophoretic sampling techniques. The measurements of scattering cross section from $90^{\circ}$ light scattering have been utilized to calculate the aggregate number density and volume fraction using with combination of measuring the particle size and morphology through the localized sampling and a TEM image analysis. Aggregate or particle number densities and volume fractions were calculated using Rayleigh-Debye-Gans and Mie theory for fractal aggregates and spherical particles, respectively. Of particular interests are the effects of flame temperature on the evolution of silica aggregate particles. As the flow rate of $H_2$ increases, the primary particle diameters of silica aggregates have been first decreased, but, further increase of $H_2$ flow rate causes the diameter of primary particles to increase and for sufficiently larger flow rates, the fractal aggregates finally become spherical particles. The variation of primary particle size along the upward jet centerline and the effect of burner configuration have also been studied.

• 한국분무공학회지
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• 제19권4호
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• pp.188-196
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• 2014

The spray and combustion characteristics of n-dodecane fuel were investigated in a CVCC (constant volume combustion chamber). The selection of ambient conditions for the spray followed ECN (engine combustion network) guidelines, which simulates the ambient condition of diesel engines at start of fuel injection. ECN is a collaboration network whose main objective is to establish an internet library of well-documented experiments that are appropriate for model validation and the advancement of scientific understanding of combustion at conditions specific to engines. Therefore repeatability of the experiments with high accuracy was important. The ambient temperature was varied from 750 to 930 K while the density was fixed at around $23kg/m^3$. The injection pressure of the fuel was varied from 500 to 1500 bar. The spray was injected in both non-reacting ($O_2$ concentration of 0%) and reacting conditions ($O_2$ concentration of 15%) to examine the spray and the combustion characteristics. Direct imaging with Mie Scattering was used to obtain the liquid penetration length. Shadowgraph was implemented to observe vapor length and lift-off length at non-reacting and reacting conditions, respectively. Pressure data was analyzed to determine the ignition delay with respect to the spray and ambient conditions.

• Journal of Ecology and Environment
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• 제29권4호
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• pp.389-398
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• 2006

To examine sediment characteristics and find anthropogenic effects on riverine wetland ecosystems, paleoecological study was carried out at Bam islands in Seoul. Three hundred cm deep sediment cores were retrieved and dated with the lamination analysis method until 36 cm depth (1986). Sediments were divided into three zones based on the depth profiles of physico-chemical variables: below 160 cm depth (before 1968), between 160 and 40cm depths and above 40cm depth (after 1986). Physico-chemical characteristics were very variable between 160 and 40cm depths and this indicates unstable sedimentation environment. Even though heavy metal concentrations were relatively low, Cd and As contents have increased continuously. Dry mass accumulation rates during $1968{\sim}1986\;and\;1987{\sim}2003$ were 140 and $21\;kg\;m^{-2}\;yr^{-1}$, respectively. This was related to flooding intensity and duration. Bulk density, water content, loss on ignition, N, C, C/N ratio were very similar to other river delta but Ca, Na and K contents were 2 to 4 times higher than others. Heavy metal contents except Pb were lower or similar to those in other studied marshes in Korea. Heavy metal and Mg contents were correlated with each other and this suggests that the source of heavy metals be parent rock. From $^{13}C$ dating dates of organic materials in sediment, it is suggested that organic matter originated from the watershed and flooding intensity in the watershed might be responsible for the source of sediments. This study provides reference data for the comparison of sediment characteristics at islands in river and for the management of Bam islands.

• Preventive Nutrition and Food Science
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• 제2권3호
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• pp.214-218
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• 1997

The purpose of this study was to investigate the potential hypolipidemic effect of job's tears diet with the controlled intake of fiber in streptozotocin induced diabetic rats. Forty eight rats were fed either control diet or experimental diets (Raw, milled job's tears(RMJ); Raw, whole grain job's tears(RWJ);Steamed, milled job's tears(SMJ);Roasted, milled job's tears(OMJ)) for 3 weeks. The levels of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), free fatty acid(FFA) and triglyceride (TG) in plasma, liver and skeletal muscle were compared. Compared to diabetic control group, the level of plasma TC was lower in OMJ an SMJ fed rats, and was not different from that in RMJ and RWJ fed rats. The level of LDL-C was significantly lower in RMJ, OMJ and SMJ fed rats. For plasma HDL-C levels, no difference was observed among all group. Plasma FFA level significantly lower in RMJ, SMJ and RWJ fed rats, Plasma TG a levels of all job's ears fed groups were 50∼70% lower and liver TG levels of all job's tears fed groups were 70∼80% lower than those fo diabetic control group. For muscle TG, no differences were seen among all groups. These results suggest that steamed job's tears and roasted job's tears could have the potentaila on improving lipid profile fo diabetes in clinical setting and the different cooking methods of job's tears might affect the lipid profile of the diabetic rats.

• 대한가정학회지
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• 제43권12호
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• pp.61-78
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• 2005

This study was peformed to assess the relationships among bone mineral density(BMD), nutrient intake and lifestyle factors in postmenopausal women. A trained nutritionist examined the interviewed usual dietary intake and physical activity of 85 subjects in Chungnam with a questionnaire interview, and BMDs of the lumbar spines($L_2-L_4$), femoral necks(FN), ward's triangles(WT) and trochanters(TR) were measured by dual energy X-ray absorptiometry (DEXA). The BMDs(T-score) of $L_2-L_4$, FN, and WT were $0.996g/cm^2(-1.601),\;0.697g/cm^2(-1.697)$, and $0.793g/cm^2(-1.512)$, respectively, which were assessed as osteopenia by T-score,. and TR was normal at $0.718g/cm^2(-0.675)$. Subjects included 85 in Chungnam were divided into three groups according to the BMD measurement of the $L_2-L_4$ and FN assessed by T-score. The percentages of the osteoporosis, osteopenia, and normal groups were $32.9\%,\;42.4\%$ and $24.7\%$ respectively. The average age was significantly the highest of the osteoporosis group than in the other two osteopenia or normal groups(P<0.001). Among lifestyle factors, the BMD of lifestyles was significantly related with exercise but it was not significant with medication., salt. intake, bone fracture, coffee consumption, drinking and smoking. The nutrient intake of the subjects was most nutrient intake adequate to the Korean RDA level for most nutrients excepting energy intakes and calcium. The BMD of lumbar spines $L_2-L_4$ showed significant positive association with the intake of most nutrients except carbohydrate, especially in the normal group. The Higher BMD levels were found for those with high intake of protein and vitamin B1. The BMDs of $L_2-L_4$, and FN were positively correlated with showed energy expenditure, exercise, miscellaneous activity, per weekend and week(P<0.05) in normal group but that was showed negatively correlated in the osteopenia group. Therefore, this study confirmed that one of the most effective ways to minimize bone less in postmenopausal women is to maintain an adequate intake of calcium and other nutrients and regular physical activity.

• 대한기계학회논문집B
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• 제23권9호
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• pp.1151-1162
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• 1999

The effects of radial heat and $H_2O$ diffusion on the evolution of silica particles in coflow diffusion flames have been studied experimentally. The evolution of silica aggregate particles in coflow diffusion flames has been measured experimentally using light scattering and thermophoretic sampling techniques. The measurements of scattering cross section from $90^{\circ}$ light scattering have been utilized to calculate the aggregate number density and volume fraction using with combination of measuring the particle size and morphology through the localized sampling and a TEM image analysis. Aggregate or particle number densities and volume fractions were calculated using Rayleigh-Debye-Gans and Mie theory for fractal aggregates and spherical particles, respectively. Flame temperatures and volumetric differential scattering cross sections have been measured for different flame conditions such as inert gas species, $H_2$ flow rates, and burner injection configurations to examine the relation between the formation of particles and radial $H_2O$ diffusion. The comparisons of oxidation and flame hydrolysis have also been made for various $H_2$ flow rates using $N_2$ or $O_2$ as a carrier gas. Results indicate that the role of oxidation becomes dominant as both carrier gas($O_2$) and $H_2$ flow rates increases since the radial heat diffusion precedes $H_2O$ diffusion in coflow flames used in this study. The effect of carrier gas flow rates on the evolution of silica particles have also been studied. When using $N_2$ as a carrier gas, the particle volume fraction has a maximum at a certain carrier gas flow rate and as the flow rate is further increased, the hydrolysis reaction Is delayed and the spherical particles finally evolves into fractal aggregates due to decreased flame temperature and residence time.

• Journal of Nutrition and Health
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• 제31권5호
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• pp.921-926
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• 1998

The purpose of this study was to investigate the potential hypolipidemic effect of adlay extract in streptozotocin-induced diabetic rats. Fifty six rats were fed either a control diet or adlay extract diets of : Methanol 1%(Ml%) ; Methanol 2%(M2%) ; Methanol 4%(M4%) ; Chloroform-Methanol 1%(CMl%) ; Chloroform-Methanol 2%(CM2%) ; Chloroform-Methanol 4%(CM4%) for 3 weeks. The amount of extracts added was 1%, 2% or 4% by diet weight respectively. The levels of glucose, total cholesterol(TC), high-density-lipoprotein cholesterol (HDL-C), free-fatty acid(FFA) and triglyceride(TG) in plasma, liver and skeletal muscle were compared. Among diabetic rats, there were no significant differences in the plasma level of glucose and TC regardless of a different extraction procedure or different amount of extracts added. While the plasma 7G level tended to increase with times passed in diabetic control group, was not increased with times passed in CM groups and was significantly lower in CM groups at 3rd week. Compared to the diabetic control group, the levels of FFA tended to be lower in all M groups and were not different in all CM groups. The levels of HDL-cholesterol were not different in all M groups and were significantly lower in all CM groups than diabetic control group. Compared to diabetic control group, liver triglyceride level was lower in M4% group and no significant difference was seen in Ml%, M2% and all CM groups. Muscle triglyceride level tended to be lower in Ml%, M2% and CM2% group and significantly was lower in M4% and CM4% group. Thus, it can be suggested that a CM extract of adllay could have a potential hypotriglyceridemic effect on diabetic subjects. (Korean J Nutrition 31(5) : 921∼926, 1998)