• Proceedings of the Korean Society of Medical Physics Conference
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• 한국의학물리학회 1999년도 Japanese Journal of Medical Physics
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• pp.278-281
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• 1999

The purpose of this study is to investigate the effect of the scattered x-rays on the subject contrast and image sharpness for various tube voltages. For the purpose, we measured the scatter-to-primary ratio(SPR) for the tube voltages f 50 to 100kV and obtained the tube voltage dependence of the subject contrast of an aluminum plate in a polymethyl methacrylate(PMMA) phantom. Furthermore, the overall modulation transfer functions(MTFs), which consist of MTFs of a screen-film system and scatter FTMs, were obtained for tube voltages of 50 to 100 kV. The subject contrast decreased with the tube voltage due to that the SPR increased with the tube voltage and that the difference in effective linear attenuation coefficients between the object and its surroundings decreased with the tube voltage. The maximum frequency of the overall MTF decreased from about 2 mm$\^$-1/ to 1 mm$\^$-1/ with the tube voltage increasing from 50 to 100 kV.

• Journal of the Institute of Convergence Signal Processing
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• 제9권2호
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• pp.159-163
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• 2008

In this paper, a simplified type of adaptive controller using Nussbaum gain for the control of the spacecrapt with elastic appendages is suggested. This method doesn't need the information of the high frequency components in transfer function. While the pitch angle tracks the desired value by this method, the elastic modes are also stabilized. Only pitch angle and the pitch rate are used for the design of the output feedback controller. Especially all system parameters and the high frequency gain are assumed to be unknown. For design simplicity, a controller is designed by using only the linear part, and it's shown to satisfy the nonlinear system by the simulation with basic explanations. By using the Lyapunov function, the stability of the suggested algorithm is demonstrated, and also the effectiveness of the suggested algorithm is verified by showing the computer simulation results.

• Journal of Welding and Joining
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• 제17권5호
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• pp.98-106
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• 1999

In GMAW, the spatters are generated according to the variation of the arc. Of the arc is stable, Few spatters are generated. But if unstable, too many spatters are generated. So, this means the spatters are dependent on the arc state. The aim of this study is to accurately estimate the arc state. To do this, the generated spatters were captured under the some welding conditions, and the waveforms of the arc voltage and welding current were collected. From the collected signals, the waveform factors and their standard deviations were extracted. Using these factors as input parameters of multi-layer artificial neural network, the learning for the weight of the generated spatters is performed and the estimation results to the real spatter are assessed. Obtained results are as follow: the linear correlation coefficient between the estimated result and the real spatters was 0.9986. And although the average convergence error was set 0.002, the estimated error to the real spatter was within 0.1 gr/min at each welding condition. In the estimation for the weight generated spatters, the result with multi-layer neural network was far better than with multiple regression analysis. Especially, even though under the welding condition which the arc state is unstable (the spatter is generated much more), very excellent estimation performance was shown.

• Journal of the Korean Society for Precision Engineering
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• 제16권6호
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• pp.141-147
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• 1999

Optical disk technology with a laser beam for data recording and retrieval is one of the most promising route for high density information storage in multimedia era. As the storage density and data transfer rates are increased, mechanical issues, mainly noise and vibration, become critical. Rubber materials are extensively used in various machine design application, mainly for vibration/shock/noise control devices. Over the years an enormous effort has been put into developing procedures to provide properties of rubber components with complex shape and under pre-deformed state. In this paper, non-linear large deformations of a rubber mount for optical disk drive were investigated using the finite element method. A tension test of rubber material was performed, to calculate a strain energy function. According to the pre-deformed state, the variation of rubber mount stiffness were calculated and the reliability of numerical results were checked by compared with the measuring the deflection values. Also, the effects of the pre-deformed rubber mount on the system dynamic characteristics were investigated and the relation between the static stiffness variation of rubber mount and the natural frequence variation of system was discussed.

• Journal of Korean Society of Water and Wastewater
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• 제7권2호
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• pp.9-23
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• 1993

Emission of hazardous and volatile organic chemicals from solid waste landfill site was become to important issue because of environmental pollution and health risk by such chemicals. Laboratory batch and continuous experiments were conducted respectively to elucidate isothermal sorption behaviors and transport phenomena(by gas through unsaturated solid waste layer) in wet solid waste-gas system. Source separated and size reduced refuse(bulky waste) and incinerated ash were used after controlling water content, and trichloroethylene(TCE) was chosen among many such chemicals because of it's generality among those man-created pollutants. Isothermal TCE sorption equilibria wet solid waste-gas system can be described in linear equation and partition coefficient in this system can be estimated approximately by the simple equation derived from schematic structure of the system. Transport equation modified by instantaneous equilibrium sorption fraction and kinetic sorption rate(overall mass transfer capacity coefficient) simulated well the column experiment results.

• Journal of Photoscience
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• 제1권2호
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• pp.95-105
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• 1994

Experiments were carried out to investigate whether P, deficiency in detached 25 mM mannose-feeding led to a decline of the photosynthetic electron transport rates through acidification of the thylakoid lumen. With increasing mannose-feeding time, the maximal CO2 exchange rates and the maximal quantum yields of photosynthesis decreased rapidly up to 6 h by 73% then with little decrease up to 12 h. The ATP/ADP ratio declined by 54% 6 h after the treatment and then recovered to the control level at 12 h. However, the NADPH/NADP~ ratio was not significantly altered by mannose treatment. Electron transport rates of thylakoid membranes isolated from 6 h treated leaves did not change, but they decreased by 30% in 12 h treated leaves. The quenching analysis of Chl fluorescence in mannose-treated leaves revealed that both the fraction of reduced plastoquinone and the degree of acidification of thylakoid lumen remained higher than those of the control. The reduction of PSI in mannose fed leaves was inhibited due to acidification of thylakoid lumen (high qE). The reduction of primary quinone acceptor of PSII was inhibited by mannose feeding. Mannose treatment decreased the efficiency of excitation energy capture by PSII. Fo quenching was induced when treated with mannose more than 6 h, and had a reverse linear correlation with (Fv)m/Fm ratio. These results suggest that Pi deficiency in Chinese cabbage leaves reduce photosynthetic electron transport rates by diminishing both PSII function and electron transfer from PSII to PSI through acidification ofthylakoid lumen, which in turn induce the modification of photosynthetic apparatus probably through protein (de)phosphorylation.

• The Korean Journal of Health Service Management
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• 제8권1호
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• pp.113-123
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• 2014

The purpose this study was to investigate the relationship between Upper extremity's function and Activities of Daily Living(ADL) in stroke patients. The participants were 112 stroke patients who underwent occupational therapy. Data were analyzed using descriptive statistics, Pearson's correlation coefficient, and multiple linear regression analysis. The results are as foolows. MFT of both unaffected upper limbs and affected upper limbs were significantly correlated with total MBI score. The all area of MFT on the affected upper limbs were significantly correlated with sub-item of MBI. And finger manipulation area of MFT on the unaffected upper limbs were significantly correlated with sub-item of MBI. Significant factors influencing MBI, both unaffected upper limbs and affected upper limbs total score. Significant factors influencing sub-items of MBI, the function of affected upper limbs by MFT were MBI all sub items exculsive bowel, bladder control and the function of unaffected upper limbs by MFT were personal hygiene, bathing, feeding, toilet, bowel & bladder control, chair/bed transfer of MBI sub items. Above results show that ADL is highly correlated with affected upper limbs and unaffected upper limbs function in the stroke patients.

• Food Science and Biotechnology
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• 제18권2호
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• pp.330-335
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• 2009

The principal objective of this study was to investigate changes in ice dendrite size during the freezing of tuna, in order to formulate a mathematical model of ice dendrite size. The tuna was frozen via a uni-directional heat transfer. Thermogram analysis allowed us to determine the position of the freezing front versus time, which is referred to as the freezing front rate. The morphology of the ice dendrites was assessed via scanning electron microscopy after freeze-drying, and the retained pore size was measured as ice dendrites. We noted that the mean size of ice dendrites increased with the distance to the cooling plate; however, it decreased with reductions in the cooling rate and the cooling temperature. In addition, shorter durations of the freeze-drying process decreased the freezing front rate, resulting in a larger size of the ice dendrite pores that operate as water vapor sublimation channels. According to our results, we could derive a linear regression as an empirical mathematical model equation between the ice dendrite size and the inverse of the freezing front rate.

• Progress in Superconductivity and Cryogenics
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• 제14권3호
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• pp.60-64
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• 2012

In this paper, an investigation of a room temperature active magnetic regenerative refrigerator is carried out. Experimental apparatus includes two active magnetic regenerators containing 186 g of Gd spheres. Four E-type thermocouples are installed inside the Active magnetic regenerator(AMR) to observe the instantaneous temperature variation of AMR. Both warm and cold heat exchangers are designed for large temperature span. The cold heat exchanger, which separates the two AMRs, employs a copper tube with length of 80 mm and diameter of 6.35 mm. In order to minimize dead volume between the warm heat exchanger and AMRs, the warm heat exchangers are located close to the AMRs. The deionized water is used as a heat transfer fluid, and maximum 1.4 T magnetic field is supplied by Halbach array of permanent magnets. The AMR plate, which contains the warm and the cold heat exchangers and the AMRs, has reciprocating motion using a linear actuator and each AMR is alternatively magnetized and demagnetized by a Halbach array of permanent magnet. Since the gap of the Halbach array of permanent magnets is 25 mm and two warm heat exchangers have the motion through it, a compact printed circuit heat exchanger (PCHE) is used as a warm heat exchanger. A maximum no-load temperature span of 26.8 K and a maximum cooling power of 33 W are obtained from the fabricated Active Magnetic Regenerative Refrigerator (AMRR).

• Journal of The Korean Astronomical Society
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• 제41권3호
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• pp.49-58
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• 2008

Resonance doublets including O VI 1032, 1038, NV 1239, 1243 and C IV 1548, 1551 constitute prominent emission lines in symbiotic stars and planetary nebulae. Spectroscopic studies of symbiotic stars and planetary nebulae from UV space telescopes show various line ratios of these doublets deviating from the theoretical ratio of 2:1. Using a Monte Carlo technique, we investigate the collisional de-excitation effect in these emission nebulae. We consider an emission nebula around the hot component of a symbiotic star characterized by the collisional de-excitation probability $p_{coll}\;{\sim}\;10^{-3}\;-\;10^{-4}$ per each resonance scattering, and the line center optical depths for major resonance doublets in the range ${\tau}_0\;{\sim}\;10^2\;-\;10^5$. We find that various line ratios are obtained when the product $p_{coll}{\tau}_0$ is of order unity. Our Monte Carlo calculations show that the flux ratio can be approximately fitted by a linear function of ${\log}{\tau}_0$ when ${\tau}_0p_{coll}\;{\sim}\;1$. It is briefly discussed that this corresponds to the range relevant to the emission nebulae of symbiotic stars.