• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.64-74
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• 2018

Small high-resolution Earth observation satellites require precise optical alignment at the submicron level. However, misalignments can occur due to the influence of external factors during the launch and operation despite the sufficient alignment processes that take place before the launch. Thus, satellites need to realign their optical elements in orbit in what is known as a refocusing process to compensate for any misalignments. Refocusing algorithms developed for satellites have only considered de-space, which is the most sensitive factor with respect to image quality. However, the existing algorithms can cause correction error when inner and external forces generate tilt amount in an optical system. The present work suggests an improved online refocusing algorithm by considering the tilting effect for application in the case of a de-spaced and tilted optical system. In addition, the algorithm is considered to be efficient in terms of time and cost because it is designed to be used as an online method that does not require ground communication.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1904-1908
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• 2008

본 연구에서는 해안가 암반대수층에서 전기전도도의 수직적인 변화를 관측하여 조석에 의한 해수와 담수 전이대의 특성을 파악하였다. 연구지역은 부경대학교 대연캠퍼스 주변 해안대수층이며, 응회질퇴적암과 안산암 및 안산암질 화산각력암 등이 분포한다. 연구에 이용된 지하수 관측공 (PK1공)은 부경대학교 대연캠퍼스 내 기숙사 동측에 위치하고 있다. 지하수공의 개발심도는 지표 면하 120 m, 케이싱은 지표면하 19 m까지 설치되어 있으며, 내경은 0.2 m로서 해안가에서 180 m 정도 이격되어 있다. 해안대수층 내 해수와 담수 전이대를 파악하기 위하여 관측공 내에 TLC Meter(Model 107, Solinst)를 삽입하여 전기전도도의 수직적인 변화를 지하수공 내 심도 50 m 까지 측정하였다. 전기전도도의 수직적인 관측은 썰물(low tide)일 때, 썰물에서 밀물(high tide)로 될 때 및 밀물일 때로 나누어 총 3회 수행되었다. 전체적인 전기전도도의 분포는 썰물일 때 $630{\sim}47300{\mu}S/cm$, 썰물에서 밀물로 되는 시기에는 $672{\sim}61900{\mu}S/cm$ 및 밀물일 때는 $678{\sim}67900{\mu}S/cm$로 나타났으며, 따라서 밀물일 때가 썰물일 때보다 전기전도도의 농도가 높은 것으로 나타났다. 해수와 담수 전이대의 분포는 썰물일 때 약 $20{\sim}50\;m$, 밀물일 때 약 $20{\sim}38\;m$ 정도로 나타났으며, 이는 밀물 시 해수의 침투로 인해 전이대 하부구간의 농도가 상승하였기 때문이다. 해수와 담수 전이대의 구간을 세분화하여 분석하기 위해, 담수가 우세한 전이대, 주 전이대 및 해수가 우세한 전이대 구간으로 구분하였다. 담수가 우세한 전이대는 썰물과 밀물일 때 모두 지표면하 $20.0{\sim}25.5\;m$ 구간이었으며, 주 전이대에서는 지표면하 $25.5{\sim}25.7\;m$ 정도로 나타났다. 그러나, 해수가 우세한 전이대에서는 썰물일 때 지표면하 $25.7{\sim}50.0\;m$ 구간, 밀물일 때는 지표면하 $25.7{\sim}38.0\;m$ 로서 전이대의 폭이 19 m 정도의 차이를 보였다. 본 연구를 통해 해안가 암반대수층에서 해수와 담수의 전이대는 조석에 의해 영향으로 인해, 썰물 시의 전이대가 밀물에 비해 그 폭이 더욱적음을 확인할 수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.183-190
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• 2010

We propose an eFuse one-time programmable (OTP) memory cell based on a logic process, which is programmable by an external program voltage. For the conventional eFuse OTP memory cell, a program datum is provided with the SL (Source Line) connected to the anode of the eFuse going through a voltage drop of the SL driving circuit. In contrast, the gate of the NMOS program transistor is provided with a program datum and the anode of the eFuse with an external program voltage (FSOURCE) of 3.8V without any voltage drop for the newly proposed eFuse cell. The FSOURCE voltage of the proposed cell keeps either 0V or the floating state at read mode. We propose a clamp circuit for being biased to 0V when the voltage of FSOURCE is in the floating state. In addition, we propose a VPP switching circuit switching between the logic VDD (=1.8V) and the FSOURCE voltage. The layout size of the designed eFuse OTP memory IP with Dongbu HiTek's $0.15{\mu}m$ generic process is $359.92{\times}90.98{\mu}m^2$.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.4
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• pp.33-39
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• 2009

A microlens array (MLA) was developed based on the wet-etched quartz substrate and coating of UV adhesive on the substrate for maskless lithography application. The developed MLA has the focal length of ${\sim}45\;{\mu}m$ and the spot size of ${\sim}1\;{\mu}m$. The spot size of the focused beam passing through the MLA was detected by CCD camera, and its intensity was monitored by beam profiler. Uniform spots with nearly identical intensities were observed on the focal plane when a beam passes through the fabricated MLA. The focal length was varied depending on thickness of the coated UV adhesive. The thicker the thickness of the UV adhesive was, the shorter the focal length of the MLA was. With a general mask aligner, UV beam focusing was tested onto photoresist (PR). The beams were well focused onto PR when UV passes through the MLA. Depending on the variable distances from the MLA, beam sizes onto PR were controlled. Even at high temperature for a long time, the performances of the MLA were not changed.

• Journal of The Korean Association For Science Education
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• v.18 no.1
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• pp.71-82
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• 1998

The main purpose of Iowa Chautauqua Program(ICP) and Iowa-Scope, Sequence. and Coordination (Iowa-SS&C) was to educate K-12 science teachers so that they could teach science in a human context using the constructivist strategies. The major task for the participating teachers to perform was to develop modules with the emphasis on STS and constructivist approach. which were supposed to be taught in the respective classrooms. Teachers worked together for two weeks for the development of modules during the summer, and attempted the modules with their students. The participating teachers met regularly during the autumn semester to share and reflect their experiences and obtain additional information on science education reform and its implications. During the winter break. the teachers improved and extended the STS modules. The Iowa Chautauqua Program and Iowa-SS&C had two important implications for Korean science education. First, they made the most of the resources they had in order to provide the practicing teachers with recent research findings on the nature of science. science learning and teaching, that is. the constructivist approach. Second, they emphasized both cooperation of teachers and long-term training to realize the reform in school science education.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.152-159
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• 2016

This paper describes an offset and 1/f noise cancellation technique based hall sensor signal processor. The hall sensor outputs a hall voltage from the input magnetic field, which direction is orthogonal to hall plate. The two major elements to complete the hall sensor operation are: the one is a hall sensor to generate hall voltage from input magentic field, and the other one is a hall signal process system to cancel the offset and 1/f noise of hall signal. The proposed hall sensor splits the hall signal and unwanted signals(i.e. offset and 1/f noise) using a spinning current biasing technique and chopper stabilizer. The hall signal converted to 100 kHz and unwanted signals stay around DC frequency pass through chopper stabilizer. The unwanted signals are bloked by highpass filter which, 60 kHz cut off freqyency. Therefore only pure hall signal is enter the ADC(analog to dogital converter) for digitalize. The hall signal and unwanted signal at the output of an amplifer and highpass filter, which increase the power level of hall signal and cancel the unwanted signals are -53.9 dBm @ 100 kHz and -101.3 dBm @ 10 kHz. The ADC output of hall sensor signal process system has -5.0 dBm hall signal at 100 kHz frequency and -55.0 dBm unwanted signals at 10 kHz frequency.

• Journal of the Korean Geotechnical Society
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• v.29 no.3
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• pp.51-60
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• 2013

The slime, deposited in the bored pile due to falling soil particle, reduces the bearing capacity of bored pile and thus the stability of construction also decreases. The weight pendulum and iron have been used for estimating the slime thickness based on the subjective judgment and thus the previous method has a limitation of reliability. The objective of this paper is to suggest the method for estimating the slime thickness by using characteristics of electrical resistivity as scientific method. The temperature-compensation resistivity probe (TRP), which has a conical shape and the diameter of 35.7mm, is applied to the measurement of the electrical resistivity in the borehole during penetration. The field tests are carried out for estimating the slime thickness in the application site of bored pile. The slime thickness is calculated through the difference between excavation depth of borehole and measured data. Furthermore, the laboratory tests are also conducted for investigating effects of casing, time elapsing and relative density by using the specimen of slime. The laboratory test supporting the suggested method is reasonable for determining the slime depth. The paper suggests that the electrical resistivity method may be a useful method for detecting slime thickness and the method is expected to be applicable to various sites of bored piles.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.4
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• pp.592-599
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• 2002

Objective : The purpose of this study was to evaluate the effects of several light curing methods and several adhesives on the microleakage of composite resin restorations in primary teeth. Materials and methods : In 150 extracted human primary anterior teeth, O-shaped cavities were prepared in the labial surface ; the cavity diameter and depth were 1.6mm. The cavities were filled with light-activated composite resin, Compoglass. Four kinds of adhesives were used. Each filling materials were polymerized with three light cure methods. The restorations were polished using Sof-Lex discs(3M Co., USA). The samples were thermocycled 1,000 times between $5^{\circ}C$ and $55^{\circ}C$ with a 1-minute dwell time. Then, they were immersed in a 2% methylene blue solution(pH 7) for 12hours. Subsequently they were sectioned labio-lingually through the center of the restoration with a diamond saw at low speed with a water coolant, and evaluated by stereomicroscopy. Microleakage analyses were done, using scores from 0 to 4. Results : Results showed the least microleakage in Compoglass group(P<0.05). There were less microleakage in SBMP group among the adhesive groups, but no significant difference was observed(P>0.05). And there were no significant differences among the groups depending on curing methods(P>0.05).

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.632-638
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• 2014

Nowadays, as part of an effort to increase the efficiency of propulsion shafting system, the revolution of the main diesel engine in CMCR(Contract Maximum Continuous Rating) is reduced whereas the stiffness of hull structure supporting the main diesel engine is relatively flexible. However, vibration problems related with resonant response of main diesel engine are increasing although top bracing is installed between the main diesel engine and the hull structures to increase natural frequency of engine body above CMCR to avoid resonant phenomenon. In this study, the dynamic characteristic of top bracing is reviewed by analyzing measuring results of general cargo ships which apply the hydraulic type instead of the friction type to control the natural frequency and the vibration of the engine body. Moreover, considering the vibration characteristic of the engine body and the hydraulic type of the top bracing by varying the number of top bracing, authors suggest the more effective way to control the vibration of the engine body despite of lower stiffness of the hull structure than in the past when the hydraulic type of top bracing is used.

• Journal of Sensor Science and Technology
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• v.9 no.6
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• pp.404-415
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• 2000

This paper describes several performances and nondestructive inspection for deterioration due to forest fires in overhead transmission lines. After discussing corrosion mechanism such as atmospheric and galvanic corrosion for aged ACSR conductors and its detection for them are presented. Through impedance analysis of a solenoid coil, it is shown that the eddy current sensor may be available to inspect severe fault or local corrosion. As the solenoid coil changes its impedance when the test conductor is inserted into the coil, it can be possible to measure deterioration degree caused by forest fires. Tensile strength, extension rate and sensor impedance are tested for some samples degraded by artificial fire. As increasing blazed period to some extent, the strength of aluminum strand begins to be reduced remarkably, while galvanized steel strand holds the similar strength to the initial value, despite of appearing a little loss of zinc layer. In general, it is shown that the sensor impedance would be increased while the tension load of conductor is reduced and the extension rate is contrarily increased. Therefore, the sensor output could exhibit the changes of mechanical performances, and would be used to detect such deterioration caused by forest fire in ACSR conductors built on the ridge of mountains. Finally, it was verified that the solenoid coil could be applicable to obtain any crucial inform for serious deterioration due to forest fires.