• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1194-1202
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• 2002

A study on the topology optimization of a multi-spectral camera for space-use is presented. The optimization is carried out under self-weight and polishing pressure loading. A multi-spectral camera for space-use experiences degradation of optical image in the space, which can not be detected on the optical test bench on the earth. An optical surface deformation of a primary mirror, which is a principal component of the camera system, is an important factor affecting the optical performance of the whole camera system. In this study, topology optimization of the primary mirror of the camera is presented. As an objective function, a measure of Strehl ratio is used. Total mass of the primary mirror is given as a constraint to the optimization problem. The sensitivities of the objective function and constraint are calculated by direct differentiation method. Optimization procedure is carried out by an optimality criteria method. For the light-weight primary mirror design, a three dimensional model is treated. As a preliminary example, topology optimization considering a self-weight loading is treated. In the second example, the polishing pressure is also included as a loading in the topology optimization of the mirror. Results of the optimized design topology for the mirror with various mass constraints are presented.

• Journal of the Korean Society of Urban Environment
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• v.18 no.4
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• pp.503-509
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• 2018

In this study, a Proton-Transfer Reaction-Time-of-Flight Mass spectrometer (PTR-TOF-MS) was used for the continuous monitoring of Volatile Organic Compounds (VOCs) emitted from semiconductor workplace such as photolithography (PHOTO), flat panel display (FPD), organic light emitting diode (OLED), etching (WET) process. The averaged VOCs mixing ratio in the such workplace, PHOTO was 6.5 ppm, FPH was 6.4 ppm, WET was 2.0 ppm and OLED was 1.3 ppm, respectively. The abundance of VOCs in the workplace were methyl ethyl ketone (MEK) with 2.8 ppm (69%) and acetaldehyde with 0.5 ppm (13.2%). Depending on the semiconductor process characteristics, various VOCs have been observed in the workplace. The VOCs mixing ratio are lower than the workplace regulation standard (TWA), it is necessary to continuously monitor and effectively manage these VOCs.

• BMB Reports
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• v.34 no.6
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• pp.496-501
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• 2001

Lincomycin, an inhibitor of plastid protein synthesis, was found to block the synthesis of apoprotein P700 with a molecular mass of 72 kDa and the assembly of the Chl a-protein of PS I. Synthesis of the polypeptides of 48, 43.5, and 32 kDa of the PS II complex is also suppressed. This process is accompanied by the disappearance of the PS Two reaction center Chl a at 683 nm, and of the PS One reaction center Chl a at 690, 696, and 705 nm on the fourth derivative of the absorption spectra at 77K. Lincomycin does not affect the synthesis of LHC subunits. It increases the content of the two main Chl forms of LHC at 648 nm (Chl b) and 676 nm (Chl a). The low-temperature fluorescence ratio F736/F685 is also increased. However, the effect of cycloheximide (an inhibitor of cytoplasmic protein synthesis) leads to the reduction of polypeptides of the light-harvesting Chl a/b-protein complex in the range of 29.5-22 kDa. Under these conditions, the relative amount of Chl b and the F736/ F685 fluorescence ratio decrease significantly. This is obviously the result of blocking the LHC I and LHC II synthesis. At the same time rifampicin and actinomycin D (inhibitors which block transcription in chloroplast and nuclear genome, respectively) inessentially affect the characteristics of these complexes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.8
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• pp.669-673
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• 2011

The charged particle type display is a kind of the reflectivity type display and shows an image by absorption and reflection of external light source, which has keep an image without additional electric power because of bistability. In this paper, we made a device whose cell gap is $56\;{\mu}m$ and also analyzed driving and memory characteristics by applied driving voltages. As a result, we found that the driving voltage and memory effect depend on q/m(charge to mass ratio) of charged particle. In this case of breakdown voltage, the devices showed degradation of reflectivity and memory effect due to irregular movement of overcharged particles. In addition, contrast ratio of the device varies with memory effect. Thus, we consider that device needs uniform q/m for improvement of electric and optical properties and memory effect.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.319.1-319.1
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• 2016

Recently, the Al-doped ZnO (ZnO:Al) films are intensively used in thin film a-Si solar cell applications due to their high transmittance and good conductivity. The textured ZnO:Al films are used to enhance the light trapping in thin film solar cells. The wet etch process is used to texture ZnO:Al films by dipping in diluted acidic solutions like HCl or HF. During that process the glass substrate could be damaged by the acidic solution and it may be difficult to apply it for the inline mass production process since it has to be done outside the chamber. In this paper we report a new technique to control the surface morphology of RF-sputtered ZnO:Al films. The ZnO:Al films are textured with vaporized HF formed by the mixture of HF and H2SiO3 solution. Even though the surface of textured ZnO:Al films by vapor etching process showed smaller and sharper surface structures compared to that of the films textured by wet etching, the haze value was dramatically improved. We achieved the high haze value of 78% at the wavelength of 540 nm by increasing etching time and HF concentration. The haze value of about 58% was achieved at the wavelength of 800 nm when vapor texturing was used. The ZnO:Al film texture by HCl had haze ratio of about 9.5 % at 800 nm and less than 40 % at 540 nm. In addition to low haze ratio, the texturing by HCl was very difficult to control etching and to keep reproducibility due to its very fast etching speed.

• Journal of Astronomy and Space Sciences
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• v.20 no.1
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• pp.63-82
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• 2003

Using the Schwarzschild's linear programming technique, we obtained the general solutions of the collisionless Bolzmann equation describing the spherical galaxy in dynamical equilibrium. From this calculation we have confirmed the existence of isotropic spherical galaxies obeying a de Vaucouleurs'law which includes a dark halo. The flattening profile of the velocity dispersion curve seen in the elliptical galaxies can be explained as the increase of mass to light ratio in this dark matter. The space density distribution of this dark matter shows that the core radius of the dark matter is smaller than the effective radius of the galaxy.

• Journal of Korean Academy of Nursing
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• v.27 no.3
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• pp.694-704
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• 1997

This study was designed to assess the body fat distribution, and also to investigate the effects of body fat on glucose tolerance and on insulin secretion pattern by body mass index in offspring of parents with NIDDM. The subjects consisted of twenty parents with NIDDM who had been admitted to the Department of Internal Medicine or had been seen in the outpatient clinic at Kangnam St. Mary's Hospital, Catholic University between February to March, 1995. Twenty offspring were randomly selected from forty six offspring of twenty parents with NIDDM. As a control group, twenty healthy people without a family history of diabetes mellitus were matched by sex, age and body mass index(BMI). The results are as follows : 1. Mean fasting serum glucose and insulin levels and insulin / glucose ratio were significantly greater in offspring than in the control subjects with BMI 25kg /㎡ in the offspring and in the BMI<25kg /㎡ control subjects (P<0.05). 2. The total glucose area and insulin area were significantly greater in both the offsping and the control subjects with BMI≥25kg /㎡ than in both the offspring and the control subjects with BMI<25 kg /㎡(P<0.05). 3. Upper body skinfold thickness, Waist hip ratio(WHR), serum levels of total cholesterol and triglyceride(TG), total dietary calorie intake and protein intake in both the offspring and the control subjects with BMI≥25kg /㎡ were greater than those with BMI<25kg /㎡(P<0.05). On the other hand, HDL-cholesterol in both the offspring and the control subjects with BMI≥25kg /㎡ was lower than those with BMI< 25kg /㎡(P<0.05). 4. The major variables influencing the total glucose area were subscapular skinfold thickness and WHR and the major variables influencing the total insulin area were suprailiac skinfold thickness, WHR, TG and free fatty acid. In the light of the results, glucose intolerance and insulin resistance were affected by body mass index, Upper body fat, WHR and lipids(TG, Free fatty acid), it is implied that these are influencing factors on total glucose area and total insulin area. The identification of these factors might provide a useful tool to identify individuals at high risk of diabetes mellitus. Therefore, various nursing intervention programs to reduce obesity could be given to both the offspring of parents with NIDDM and to the obese healthy controls before diabetes mellitus develops.

• Journal of Environmental Science International
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• v.16 no.7
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• pp.785-791
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• 2007

The current study evaluated the technical feasibility of the application of titanium dioxide ($TiO_{2}$) photo-catalytic air cleaners for the disinfection of bioaerosols present in indoor air. The evaluation included both laboratory and field tests and the tests of hydraulic diameter (HD) and lamp type (LT). Disinfection efficiency of photocatalytic oxidation (PCO) technique was estimated by survival ratio of bacteria or fungi calculated from the number of viable cells which form colonies on the nutrient agar plates. It was suggested that the reactor coating with $TiO_{2}$ did not enhance the adsorption of bioaerosols, and that the UV irradiation has certain extent of disinfection efficiency. The disinfection efficiency increased as HD decreased, most likely due to the decrease in the light intensity since the distance of the catalyst from the light source increased when increasing the HD. It was further suggested that the mass transfer effects were not as important as the light intensity effects on the PCO disinfection efficiency of bioaerosols. Germicidal lamp was superior to the black lamp for the disinfection of airborne bacteria and fungi, which is supported by the finding that the disinfection efficiencies were higher when the germicidal lamp was used compared to the black lamp in the laboratory test. These findings, combined with operational attributes such as a low pressure drop across the reactor and ambient temperature operation, can make the PCO reactor a possible tool in the effort to improve indoor bioaerosol levels.

• Resources Recycling
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• v.29 no.1
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• pp.81-88
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• 2020

Recovery of gallium and indium from waste light emitting diodes has been emphasized gradually owing to high content of gallium and indium. This study was established the recovery of gallium (Ga³⁺) and indium (In³⁺) from waste gallium nitride was contained in waste light-emitting diodes. The procedure was divided into the following steps; characteristic analysis, alkaline roasting, and leaching. In characteristic analysis part, the results were used as a theoretical basis for the acid leaching part, and the chemical composition of waste light emitting diodes is 70.32% Ga, 5.31% Si, 2.27% Al and 2.07% In. Secondly, with reduction of non-metallic components by alkaline roasting, gallium nitride was reacted into sodium gallium oxide, in this section, the optimal condition of alkaline roasting is that the furnace was soaked at 900℃ for 3 hours with mixing Na₂CO₃. Next, leaching of waste light emitting diodes was extremely important in the process of recovery of gallium and indium. The result of leaching efficiency was investigated on the optimal condition accounting for the acid agent, concentration of acid, the ratio of liquid and solid, and reaction time. The optimal condition of leaching procedures was carried out for 2.0M of HCl liquid-solid mass ratio of 30 ml/g in 32minutes at 25℃ and about 96.88% Ga and 96.61% In were leached.

• Korean Journal of Materials Research
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• v.29 no.3
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• pp.155-159
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• 2019

Surface plasmon resonance is the resonant oscillation of conduction electrons at the interface between negative and positive permittivity material stimulated by incident light. In particular, when light transmits through the metallic microhole structures, it shows an increased intensity of light. Thus, it is used to increase the efficiency of devices such as LEDs, solar cells, and sensors. There are various methods to make micro-hole structures. In this experiment, micro holes are formed using a wet chemical etching method, which is inexpensive and can be mass processed. The shape of the holes depends on crystal facets, temperature, the concentration of the etchant solution, and etching time. We select a GaAs(100) single crystal wafer in this experiment and satisfactory results are obtained under the ratio of etchant solution with $H_2SO_4:H_2O_2:H_2O=1:5:5$. The morphology of micro holes according to the temperature and time is observed using field emission - scanning electron microscopy (FE-SEM). The etching mechanism at the corners and sidewalls is explained through the configuration of atoms.