• 천문학회지
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• 제29권spc1호
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• pp.219-221
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• 1996

The x-ray pulsar GX 1+4 was observed by us in four balloon- borne experiments carried out from Hyderabad, India during 1991-1995 period with a hard x-ray telescope. The x-ray telescope consists of two collimated large area xenon-filled proportional counters with an effective area of $2400 cm^2$, a field of view of $5^{\circ}{\times}5^{\circ}$ and sensitive in the energy band of 20 - 100 keV. The pulsar was detected in bright state in two of the four experiments and x-ray pulsations with 120 second period were detected clearly. Pulsation period, rate of change of period with time, pulse fraction, pulse profile and energy spectra of the source were determined from these studies. During March 1995 observation, the x-ray pulse of GX 1+4 was found to be double-peaked compared to a single-peak pulse profile detected in December 1993. Details of these results are presented and their interpretation discussed in terms of the current accretion models of x-ray binaries.

• Journal of Biosystems Engineering
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• 제26권3호
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• pp.263-270
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• 2001

This study was conducted in order to develop wind-water heating system where frictional heat is creased between the rotor and working fluid when they are rotating in the cylindrical heat generator. The wind-water heating system is composed of rotor, stator, working fluid, motor, inverter and heat generation tank. Instead of wind turbine, we have used an electrical motor of 30㎾ to rotate the rotor in this system. Two working fluids and six levels of rotor rpm were tested to quantify heat amounts generated by the system. Generally, as motor rpm goes up heat amount increases that we have expected. At the same rpm, viscous fluid showed up better performance than the water, generating more heat by 10$\^{C}$ difference. The greatest heat amount of 31,500kJ/h was obtained when the system constantly drained out the hot water of at the flow rate of 500ℓ/h. Power consumption rate of the motor was measured by thee phase electric power meter where the largest power consumption rate was 14㎾ when motor rpm was 600 and gained heat was 31,500kJ/h, that indicated total thermal efficiency of the wind power water heating system was 62%.

• Natural Product Sciences
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• 제25권1호
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• pp.49-58
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• 2019

Eleven steroid hormones (SHs: androstene-3,17-dione, estrone, ${\beta}$-estradiol, ${\alpha}$-estradiol, testosterone, dehydroepiandrosterone, $17{\acute{a}}$-hydroxyprogesterone, medroxyprogesterone, megestrol acetate, progesterone, and androsterone) were detected from New Zealand deer (Cervus elaphus var. scoticus) velvet antler (NZA, 鹿茸 ). A method for the quantification of eleven SHs was established by using ultraperformance liquid chromatography (UPLC)-MS/MS. The linearities ($R^2$ > 0.991), limits of quantification (LOQ values, 0.3 ng/mL to 23.1 ng/mL), intraday and interday precisions (relative standard deviation: RSD < 2.43%), and recovery rates (97.3% to 104.6%) for all eleven SHs were determined. In addition, a method for the quantification of three 7-oxycholesterols (7-O-CSs: 7-ketocholesterol, $7{\alpha}$-hydroxycholesterol, and $7{\beta}$-hydroxycholesterol) in the NZA was established by using an HPLC-photodiode array (PDA) method. The linearities ($R^2$ > 0.999), LOQ values (30 ng/mL to 350 ng/mL), intraday and interday precisions (RSD < 1.93%), and recovery rates (97.2% to 103.5%) for the three 7-O-CSs were determined. These quantitative methods are accurate, precise, and reproducible. As a result, it is suggested that the five steroid compounds of androstene-3,17-dione, androsterone, 7-ketocholesterol, $7{\alpha}$-hydroxycholesterol, and $7{\beta}$-hydroxycholesterol could be marker steroids of NZA. These methods can be applied to quantify or standardize the marker steroids present in NZA.

• 대한전자공학회논문지TC
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• 제45권8호
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• pp.28-34
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• 2008

MRI(magnetic resonance imaging)의 신호검출기로 활용 가능한 간단한 형태의 자기장 검출기를 제안하였다. 제안된 검출기는 SRR(split ring resonator)이라고 하는 음의 투자율을 구현하는데 최초 사용되었던 일종의 LC 공진회로와 간단한 루프안테나를 유도성 결합시킨 것으로 기존의 MRI 신호검출기에 비해 단순한 구성으로 유사한 감도를 가질 수 있음을 확인하였다.

• 한국습지학회지
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• 제15권4호
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• pp.519-527
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• 2013

환경부는 국가습지의 체계적인 조사 관리를 강화하고 지속가능한 국가습지의 보전과 이용을 위해서 "제2차 습지보전기본계획"을 수립하였다. 이 계획은 습지보전법 제5조의 규정에 따른 중기계획으로 계획의 범위는 시간적으로는 2013년부터 2017년까지 5개년계획이며 공간적으로는 습지보전법에 규정되어 있는 내륙습지와 연안습지를 포함한 전국의 습지를 대상으로 한다. "제2차 습지보전기본계획"은 제1차 습지보전기본 이행성과평가에 따라 국가습지의 지속가능한 보전 정책 방향을 설정하여, 습지조사 체계 개선과 습지 기초자료 강화를 통해 국가습지정책 수립과 집행에 과학적 기반을 마련하고, 국가습지의 보전과 관리체계 강화를 통한 습지 생태계건강성 확보와 생물다양성 보전, 인식증진 확대와 교육 홍보 여건 다변화 등을 통해 습지의 현명한 이용 활성화를 목적으로 한다. 제2차 기본계획의 주요 추진 내용은 습지보전법 전면 개정, 전국내륙습지 모니터링 제도 신설, 국가습지인벤토리 강화, 사전예방적 습지관리를 위한 '생태자연도 반영', 습지건강성 회복을 위한 '습지복원 관리' 제도정비, 지역과 상생하는 습지의 '현명한 이용'체계화 등이다. 본 기본계획에 따라 향후 5년간 환경부가 습지보전을 위한 기본계획을 수립하여 이를 이행할 예정이므로 습지에 관련한 업무를 수행하는 관계자들에게 이를 소개 하고자 한다.

• Architectural research
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• 제12권1호
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• pp.39-47
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• 2010

This paper describes a topology optimization technique which can maximize the fundamental frequency of the structures. The fundamental frequency maximization is achieved by means of the minimization of modal strain energy as an inverse problem so that the strain energy based resizing algorithm is directly used in this study. The strain energy to be minimized is therefore employed as the objective function and the initial volume of structures is used as the constraint function. Multi-frequency problem is considered by the introduction of the weight which is used to combine several target modal strain energy terms into one scalar objective function. Several numerical examples are presented to investigate the performance of the proposed topology optimization technique. From numerical tests, it is found to be that the proposed optimization technique is extremely effective to maximize the fundamental frequency of structure and can successfully consider the multi-frequency problems in the topology optimization process.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1438-1445
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• 2008

The purpose of this study is to evaluate the fundamental frequency of the dam by the various methods using real microearthquake records which were measured on 'H' dam site and to compare each results. In this study, the fundamental frequency was evaluated by the frequency analysis of the microearthquake records which were measured on the dam crest, by the evaluation of acceleration amplification ratio between the foundation and the crest of dam, and by the evaluation of acceleration response spectrum ratio between the foundation and the crest of dam, respectively. Among these methods, it was found that the method by the evaluation of acceleration response spectrum ratio between the foundation and the crest of dam was the most effective method. But, if the simple engineering judgement can be considered, it was thought that the all three methods could reasonably evaluate the fundamental frequency of the dam.

• 대한수학교육학회지:수학교육학연구
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• 제9권1호
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• pp.217-228
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• 1999

The fundamental theorem of calculus is the most 'fundamental' content in teaching calculus. Since the aim of teaching the theorem goes beyond simple application of it, it is difficult to teach it meaningfully. Hence, for the meaningful teaching of the fundamental theorem of calculus, this article seeks to find the educational implication of the fundamental theorem of calculus through reviewing the genetic history of it. A genetic history of the fundamental theorem of calculus can be divided into the following five phases: 1. The deductive discovery of the fundamental theorem of calculus 2. Galileo's Law of falling body and the idea of the fundamental theorem of calculus 3. The discovery of the fundamental theorem of calculus and Barrow's proof 4. Newton's mensuration 5. the development of calculus in 19th century and the fundamental theorem of calculus The developmental phases of the fundamental theorem of calculus discussed above provides the three educational implications. first, we can rediscover this theorem through deductive methods and get the ideas of it in relation to kinetic problems. Second, the developmental phases of the fundamental theorem of calculus shows that the value of this theorem lies in the harmony of its theoretical beauty and practicality. Third, Newton's dynamic image of this theorem can be a typical way of understanding the theorem. We have different aims of teaching the fundamental theorem of calculus, according to which the teaching methods can be adopted. But it is self-evident that the simple application of the theorem is just a part of teaching the fundamental theorem of calculus. Hence we must try to put the educational implications reviewed above into practice.

• ETRI Journal
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• 제32권2호
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• pp.339-341
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• 2010

The fundamental transverse mode lasing of a hybrid laser diode is a prerequisite for efficient coupling to a single-mode silicon waveguide, which is necessary for a wavelength-division multiplexing silicon interconnection. We investigate the lasing mode profile for a hybrid laser diode consisting of silicon slab and InP/InGaAsP deep ridge waveguides. When the thickness of the top silicon is 220 nm, the fundamental transverse mode is lasing in spite of the wide waveguide width of $3.7{\mu}m$. The threshold current is 40 mA, and the maximum output power is 5 mW under CW current operation. In the case of a thick top silicon layer (1 ${\mu}m$), the higher modes are lasing. There is no significant difference in the thermal resistance of the two devices.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.52-54
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• 1994

To demonstrate the applicability of super-conductors to electric power machines, the authors made and tested a small single-phase superconducting transformer. The aim of the study was to determine the fundamental properties of superconducting trans former. Therefore the superconducting transformer has a simple structure, i.e. the high voltage to low one ratio is 2:1 and the iron core is immersed in liquid helium. Fundamental characteristics are obtained through no-load and short-circuit tests. In this paper, the experimental results are described.