• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.179-184
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• 2018

To lessen oxygen concentrations in a wafer through modifying the length of graphite heaters, we investigated the influence of relative distance from heater to quartz crucible on temperature profile of hot-zone in Czochralski silicon-crystal growth by simulation. In particular, ATC temperature and power profiles as a function of different ingot body positions were investigated for five different heater designs; (a) typical side heater (SH), (b) short side heater-up (SSH-up), (c) short side heater-low (SSH-low), (d) bottom heater without side heater (Only-BH), and (e) side heater with bottom heater (SH + BH). It was confirmed that lower short side heater exhibited the highest ATC temperature, which was attributed to the longest distance from triple point to heater center. In addition, for the viewpoint of energy efficiency, it was observed that the typical side heater showed the lowest power because it heated more area of quartz crucible than that of others. This result provides the possibility to predict the feed-forward delta temperature profile as a function of various heater designs.

• Journal of Haehwa Medicine
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• v.12 no.1
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• pp.103-121
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• 2003

Human being can't live without nature, then the changes of nature affect human body. It means that human body has corresponding changes to the KI(vital energy) of nature. There is a stream of changes in human body which circulate mysteriously and punctually by the laws of nature. If this stream of changes fits into human's life style, it would be most effective. It has a certain mode continuously. So if a person has a habit fitting into it, he will get the healthiest body. Then the researcher tries to explain the changes in human body by the time, mainly focused on within 24 hours. it is showing not only the oriental view, but also the western's. The researcher can find the coincidence as followings. At In-Si(3-5 am), the body function and the body temperature get to the bottom, therefore it's good for him to wake up and to run the vital energy. At Sa-Si(9-11 am), the patience on pain anxiety and the psychic concentration get to the top, he'd better start the work. At O-Si(11am-1pm), the heart energy has a vital move, then the blood concentration of Hb(hemoglobin) gets to the top. At Mi-Si(1-3 pm), the muscle strength, the squeeze, and the breathing rate increase. The reflex nerve sensitivity gets to the top. Creativity, observation, and working efficiency go high, so it's time to work hard. At Hae-Si(9pm-1am), the body function falls, sleeping is needed. At Chuck-Si(1-3 am), the cell spontaneity gets to the top, immune lymphocyte moves actively, and the blood concentration of growth hormone gets to the top. These are liver's work. In west, there has been active studies on how to reduce the side effect by using a person's bio-rhythm based on the 'time treatment', and how to reorganize the bio-rhythm by using the machine and the age resistance based on the 'bio-watch'. Though the 'time treatment' means something, the artificial resistance on bio-rhythm seems to give bad effects to human body. If a person lives by regimen of oriental medicine, he will maintain the healthiest body. Regimen is that human body follows the laws of nature, and moves its mysterious, Punctual and periodical changes.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.802-807
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• 1995

The electrochromic properties of vacuum deposited V$_2$O$_{5}$ thin films as a function of crystallinity and film thickness have been systematically investigated. The as-deposited films have slightly yellow appearance. V$_2$O$_{5}$ films deposited at higher substrate temperature(>14$0^{\circ}C$) are found to be crystalline while those deposited at low substrate temperature are amorphous. The optical modulation on lithium ion injection indicates that V$_2$O$_{5}$ films exhibit anodic coloration in the 300~500 nm wavelength range and cathodic coloration in the 500~1100nm wavelength range independent of crystallinity and film thickness. The optical band gap energy of crystalline and amorphous Li$_{x}$ VV$_2$O$_{5}$ films shifts to higher energies by 0.17 eV and 0.75 eV, respectively, with increasing lithium ion injection up to x=0.6. The coloration efficiency of amorphous Li$_{x}$ V$_2$O$_{5}$ exhibits very little dependence on film thickness and lithium ion injection amounts in the near-infrared while it increases significantly with increasing film thickness and decreasing lithium ion injection amounts in the blue and near-UV due to the shift in absorption edge below around 500nm. However, the coloration efficiency of crystalline Li$_{x}$ V$_2$O$_{5}$is relatively independent of film thickness and lithium ion injection in the 300~1100 nm wavelength range.

• Journal of Astronomy and Space Sciences
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• v.35 no.3
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• pp.201-210
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• 2018

The characterization of detectors installed in space- and ground-based instruments is important to evaluate the system performance. We report the development of a detector performance test system for astronomical applications using the Andor iKon M CCD camera. The performance test system consists of a light source, monochromator, integrating sphere, and power meters. We adopted the Czerny-Tuner monochromator with three ruled gratings and one mirror, which covers a spectral range of 200-9,000 nm with a spectral resolution of ~1 nm in the visible region. Various detector characteristics, such as the quantum efficiency, sensitivity, and noise, can be measured in wide wavelength ranges from the visible to mid-infrared regions. We evaluated the Korea Astronomy and Space Science Institute (KASI) detector performance test system by using the performance verification of the Andor iKon-M CCD camera. The test procedure includes measurements of the conversion gain ($2.86e^-/ADU$), full well capacity ($130K\;e^-$), nonlinearity, and pixel defects. We also estimated the read noise, dark current, and quantum efficiency as a function of the temperature. The lowest measured read noise is $12e^-$. The dark current at 223 K was determined to be $7e^-/s/pix$ and its doubling temperature is $5.3^{\circ}C{\pm}0.2^{\circ}C$ at an activation energy of 0.6 eV. The maximum quantum efficiency at 223 K was estimated to be $93%{\pm}2%$. We proved that the quantum efficiency is sensitive to the operating temperature. It varies up to 5 % in the visible region, while the variation increases to 30 % in the near-infrared region. Based on the comparison of our results with the test report by the vendor, we conclude that our performance test results are consistent with those from the vendor considering the test environment. We also confirmed that the KASI detector performance test system is reliable and our measurement method and analysis are accurate.

• Progress in Medical Physics
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• v.23 no.3
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• pp.154-161
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• 2012

Digital Radiography (DR) has rapidly developed in megavoltage X-ray imaging (MVI). Thus, a very simple and general quality assurance (QA) method is required. The purpose of this study was to evaluate the modulation transfer function (MTF), the noise power spectrum (NPS) and the detective quantum efficiency (DQE) for MVI using general QA method and computed radiography (CR) device. We used tungsten edge block with $19{\times}10{\times}1cm^3$ thickness and 6MV energy. For detector, CR-IP (image plate), CR-IP-lead, the CR-IP-back (lanex TM fast back screen), CR-IP-front (lanex TM fast front screen) were used and pre-sampling MTF was calculated. The MTF of CR-IP-front showed the highest value with 1.10 lp/mm although the CR-IP showed the only 0.70 lp/mm. The best NPS was observed in CR-IP front screen. According to the increase in spatial frequency, our results showed that DQE was approximately 1.0 cycles/mm. The present study demonstrates that the QA method with our home-made edge block can be used to evaluate MTF, NPS and DQE for MVI.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.387-394
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• 2013

Hydrogen-compressed natural gas (HCNG) blend has attracted attention as a fuel that can reduce $CO_2$ emissions because it has low carbon content and burns efficiently. An increase in the compression ratio of HCNG engines was considered as one of the methods to improve their efficiency and reduce $CO_2$ emissions. However, a high combustion rate and flame temperature cause abnormal combustion such as pre-ignition or knocks, which in turn can cause damage to the engine components and decrease the engine power. In this study, the performance and knock characteristics with a change in the compression ratio of an HCNG engine were analyzed. The combustion characteristics of HCNG fuel were evaluated as a function of the excess air ratio using a conventional CNG engine. The effects of the compression ratio on the engine performance were evaluated through the same experimental procedures.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.2
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• pp.33-38
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• 2010

Recently, photovoltaic generator system is widely extended by energy policy of the government. Add to this, high efficiency of photocell power generation is steady needed to sun tracking method. However sun tracking method is not widely extended by insufficiency of tracking technology. As method of solving this problem, this paper applied sunlight sensor and neural network control algorithm for maximum power tracking of sun photocell. Sun tracking sensor consists of one upright square pole and form light sensor of east, west, south, north on flat board. Sun tracking dual axes control is operated respectively by two motor. Motor control input is calculated by neural network control algorithm. The function of proposed control method is verified by sun tracking experiment of photocell generation. The sun tracking method of this paper is increased 32[%] efficiency more than fixed method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.258-264
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• 2018

This paper presents application of a differential search (DS) meta-heuristic optimization algorithm for optimal operation of a micro grid system. The DS algorithm simulates the Brownian-like random-walk movement used by an organism to migrate. The micro grid system consists of a wind turbine, a diesel generator, a fuel cell, and a photovoltaic system. The wind turbine generator is modeled by considering the characteristics of variable output. Optimization is aimed at minimizing the cost function of the system, including fuel costs and maximizing fuel efficiency to generate electric power. The simulation was applied to a micro grid system only. This study applies the DS algorithm with excellence and efficiency in terms of coding simplicity, fast convergence speed, and accuracy in the optimal operation of micro grids based on renewable energy resources, and we compared its optimum value to other algorithms to prove its superiority.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.3
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• pp.15-34
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• 2004

Diverse benefits such as reduction of fresh water consumption and effluent discharge, efficient use of raw materials and energy savings can be obtained by papermaking system closure. Closure of papermaking processes, however, causes many problems including reduction of the efficiency of additives, decrease of retention and dewatering, felt plugging, poor Paper quality, generation of slime and odor, poor vacuum efficiency, etc, and it has been recognized that accumulation of Inorganic and organic substances in the process white water is the prime cause of these problems. Therefore, technological developments for preventing accumulation of these detrimental substances are urgently required for Implementing papermaking system closure. Understanding of the accumulation phenomena of the inorganic and organic substances in the papermaking process white water is prerequisite for papermaking system closure. In this study a process simulation method was used to analyze the accumulation phenomena of anionic starch In the process white water as the closure level of a fine paper making process is increased. A pilot paper machine was used as a model process. Starch adsorption and desorption models were developed based on the concept of starch adsorption ratio, which was not considered in previous studies. Steady state simulation studies were carried out based on this model using a commercial simulator. In steady state simulation, the variation of dissolved starch concentration in each process unit was monitored as a function of white water usage for wire shower. The result of the steady state simulation showed that dissolved starch concentration and its increase ratio in Process units increased as white water usage ratio for wire shower increased.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.7
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• pp.112-124
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• 1989

In order to evaluate imaging performance of newly developed digital radiography system which requires scanning time as short as 0.7 sec and patient exposure as low as 3 mR, we have investigated its imaging and physical properties such as sensitivity characteristic, scatter fraction, detective quantum efficiency, modulation transfer function, and contrast detail diagram. The results show that the digital radiography system has linear sensitivity to the incident energy, and superior contrast resolving power with less X-ray exposure than conventional film-screen system. These performances are resulted from excellent scatter rejection capability and high detective quantum efficiency of digital radiography system.