전자기 벡터장 시각화를 위한 Mathematica 시뮬레이션

최용대,윤희중,Choi, Yong-Dae,Yun, Hee-Joong 한국진공학회 2012 Applied Science and Convergence Technology Vol.21 No.2

전자기장을 포함한 대부분의 물리학적 시스템이 벡터 미분 연산자들로 기술되며 또한 벡터연산을 통하여 계산된다. 그러므로 이들 벡터장들이 유전 및 자성물질 시스템들과 상호작용할 때 물리적 체계를 기술하고 계산하려면 정확한 전자기 벡터장의 지식체계를 이해할 필요가 있다. 그런데 이들 대부분 추상적 개념들을 직관적으로 이해하기에는 쉽지 않기 때문에 이들 추상적 개념의 시각화 표현 작업은 오늘날 지식정보화 수행과정에서 매우 중요한 과제의 하나다. 우리는 전자기학 체계를 구성하는 가장 기본적인 벡터장: $\vec{E}=-\vec{\nabla}_{\varphi}$, $\vec{D}={\epsilon}\vec{E}$, $\vec{\nabla}{\times}\vec{A}$, $\vec{B}={\mu}\vec{H}$, $\vec{B}={\mu}_0(\vec{\nabla}_{\varphi}{^*}+\vec{M})$들의 가시화 시뮬레이션을 Mathematica 프로그램으로 작성하여 추상적인 전자기벡터장의 시각화 모델을 제시하였다. 이 시뮬레이션을 전자기 벡터장의 물리학적 지식체계를 탐구해 가는 기본 플랫폼으로 활용할 수 있다. Visualization of the electromagnetic vector fields are presented and examined with Mathematica. Vector fields may be used to represent a great of many physical quantities in various area of physics, including electromagnetism with vector differential operators. Because they deal with abstract, three-dimensional fields that are some times very difficult to visualize, electromagnetism can be conceptually rather difficult. Visual representation of such an abstract vector fields is invaluable to student or researchers working in this field and also helps teaching electromagnetism to physics or engineering students. Mathematica provides a wider range of graphical tools including plot of vector fields and vector analysis, which can be applied to visualization of electromagnetic system. We have visualized the most fundamental concepts of the electromagnetic vector $\vec{E}=-\vec{\nabla}_{\varphi}$, $\vec{D}={\epsilon}\vec{E}$, $\vec{\nabla}{\times}\vec{A}$, $\vec{B}={\mu}\vec{H}$, $\vec{B}={\mu}_0(\vec{H}+\vec{M})$, which are confirmed with vector calculations and valid graphically with some presentations.

시간속성과 주기(週期)에 따른 경기(經氣).오유혈(五兪穴) 변화에 대한 연구

최용대,김병수,강정수,Choi, Yong-Dae,Kim, Byoung-Soo,Kang, Jung-Soo 대전대학교 한의학연구소 2010 한의학연구소 논문집 Vol.19 No.1

In Neijing("內經"), it explains heaven, earth, four seasons(天地四時) take part in human's birth, it gives influence on life support, and have organic relationship between body and movement of sun and earth(日月運行) of heaven and earth. Human body and the natural world corresponds, so the time changes in the natural world give immediate influence to human body, and correspond changes happen inside human body. This has no exception in qi of human(人氣), meridians, the viscera and organs(臟腑) and so on. In time, there are many kinds of cycles such as year, month, 10 days and a day. Yin and yang and the five elements in each cycle shows changes of prosperity and decay and transformation. In a year, there are spring, summer, late summer, fall and winter which are each included to wood, fire, earth, metal and water. Spring and summer belong to yang(陽), and fall and winter belong to yin(陰). A day can be divided into the crowing of the cook, dawn, noon, and twilight. After midnight yin falls and yang rises(陰盡陽生), and after noon yang falls and yin rises(陽盡陰生). Ups and downs of the qi and blood and human body change with time and the region of whereabout is different. In one month, when the moon is full qi of blood rises and when the moon comes down qi of blood falls. The qi of meridian(經氣) has a periodical changes with regular movement in meridian. This is a result of continuing movement of meridian and the nutrient(營) and the defense(衛) in human body, stars correspond with ups, and correspond with flow of water of meridian(經水) with downs. In a day the twelve meridians(十二經脈) in hour of yin(hours 3~5), it starts with qi and blood of lung meridian(手太陰肺經) prosperous, each qi and blood of meridian prosperous in order. In eight extra meridians(奇經八脈), Bideungpalbup(飛騰八法) per 5 days, Younggoopalbup(靈龜八法) per 60 days qi of pulse(脈氣) changes correspond. The qi and blood of five meridian points(五兪穴) is 5 days, so.

배드민턴 라켓용 Sheath/core 복합구조 String의 제조 및 특성

최용대,박영미,Choi, Yong-Dae,Park, Young-Mi 한국섬유공학회 2015 한국섬유공학회지 Vol.52 No.5

This paper presents a method of preparing a high-strength sheath/core complex badminton string and examines its playability and durability performance. From repeated experiments at the laboratory scale, it was determined that the tensile characteristics of sheath/core complex strings are better than those of widely used general strings. The key process of braiding, in which the string is prepared by twisting sheath multifilament around the core of a 3-ply monofilament, and the time required for applying a thin layer of coating, have decisive effects on the physical properties. The yarn diameter was found to be optimal when the string was coated three times and the structure of the sheath/core was composed of multifilament 1890d/monofilament 100d. SEM identified an increase in the inner thickness of the sheath/core string with braiding and coating. To conclude, Sample D displayed high tenacity, tensile extension, and tensile strength, which can affect durability, while its tensile modulus was the lowest (54.13 g/tex), which is indicative of good playability.

시간속성과 주기(週期)에 따른 경기(經氣) · 오수혈(五兪穴) 변화에 대한 연구

최용대 ( Yong Dae Choi ),김병수 ( Byoung Soo Kim ),강정수 ( Jung Soo Kang ) 대전대학교 한의학연구소 2010 혜화의학회지 Vol.19 No.1

In Neijing(『內經』), it explains heaven, earth, four seasons(天地四時) take part in human`s birth, it gives influence on life support, and have organic relationship between body and movement of sun and earth(日月運行) of heaven and earth. Human body and the natural world corresponds, so the time changes in the natural world give immediate influence to human body, and correspond changes happen inside human body. This has no exception in qi of human(人氣), meridians, the viscera and organs(臟腑) and so on. In time, there are many kinds of cycles such as year, month, 10 days and a day. Yin and yang and the five elements in each cycle shows changes of prosperity and decay and transformation. In a year, there are spring, summer, late summer, fall and winter which are each included to wood, fire, earth, metal and water. Spring and summer belong to yang(陽), and fall and winter belong to yin(陰). A day can be divided into the crowing of the cook, dawn, noon, and twilight. After midnight yin falls and yang rises(陰盡陽生), and after noon yang falls and yin rises(陰盡陽生). Ups and downs of the qi and blood and human body change with time and the region of whereabout is different. In one month, when the moon is full qi of blood rises and when the moon comes down qi of blood falls. The qi of meridian(經氣) has a periodical changes with regular movement in meridian. This is a result of continuing movement of meridian and the nutrient(營) and the defense(衛) in human body, stars correspond with ups, and correspond with flow of water of meridian(經水) with downs. In a day the twelve meridians(十二經脈) in hour of yin(hours 3~5), it starts with qi and blood of lung meridian(手太陰肺經) prosperous, each qi and blood of meridian prosperous in order. In eight extra meridians(奇經八脈), Bideungpalbup(飛騰八法) per 5 days, Younggoopalbup(靈龜八法) per 60 days qi of pulse(脈氣) changes correspond. The qi and blood of five meridian points(五兪穴) is 5 days, so.

HWE에 의하여 성장된 CdS : In 박막의 전기광학적 특성과 그 응용

최용대(Yong Dae Choi),윤희중(Hee Joong Yun),김진배(Jin Bae Kim),이완호(Wan Ho Lee),신영진(Yeong Jin Shin),양동의(Dong Ik Yang) 한국진공학회(ASCT) 1992 Applied Science and Convergence Technology Vol.1 No.3

HWE(Hot-Wall Epitaxy) 방법에 의하여 pyrex 유리기판 위에 CdS 다결정 박막을 성장하였다. X-선 회절실험 결과 CdS 박막은 육방정이었는데 (0002)면보다 (1013)면이 강하게 성장됨을 알 수 있었다. 전자현미경으로 표면을 분석한 결과 입자의 크기는 기판의 온도가 480℃, 증발원의 온도가 610℃일 때 1~1.5 ㎛로서 가장 컸다. 박막의 표면저항은 4-point probe로서 측정한 결과 10^(-8)Ω/□이상이었다.<br/> 성장된 CdS 다결정 박막의 photoluminescence을 20 K에서 측정하였는데 bound exciton, donor-acceptor pair에 의한 발광이 관측되었다. Spectral response의 peak는 505 ㎚이었다. CdS 다결정 박막의 표면저항을 줄이기 위하여 여러 가지 온도에서 Indium을 확산시켰다. 그 결과 표면저항은 ~×10¹에서 ~×10³Ω/□ 정도 감소되었다. 500℃ 에 In을 1시간 확산시켰을 때 표면저항은 1300Ω/□이었다. 이 때 CdS : In의 운반자 농도는 1.2×10^(18)㎝-³, 이동도는 1.8㎝-²/V-sec. 비저항은 1.3×10^(-2)Ω-㎝이었다. CdS : In의 photoluminescence는 20 K에서 Gaussian curve를 보여 주었으며 peak의 위치는 510 ㎚이었다. CdS : In 박막의 spectral response의 peak는 상온에서 500 ㎚이다. CdS : In 광전도 cell의 sensitivity γ=0.77이고, 최대 허용소비전력은 p=120㎽, 100 lux에서 rise time은 8 msec, decay time은 6 msec이다. CdS polycrystalline thin films are grown on the pyrex plates by HWE(hot-wall epitaxy). The analysis of X-ray diffraction patterns shows that the crystal structures are hexagonal. Diffraction line by (0002) and (1013) are mainly observed. The grain size of CdS polycrystalline thin films grown at the temperature 480℃ of the substrate and at the temperature 610℃ of the source is 1~1.5 ㎛, and the thickness of the films is 1 ㎛. The sheet resistivity of the thin films is over 10^8Ω/□.<br/> Photoluminescence of the CdS polycrystalline thin films are measured at 20K. The emissions due to bound exciton (I₁I₂ line) and donor-acceptor pair are observed. The peak of the spectral response is located at the wavelength of 505 ㎚. Indium is diffused on CdS polycrystalline thin films to reduce the sheet resistivity at the various condition. As a result of it, the sheet resistivity is reduced from ~×10¹ to ~×10³Ω/□. When Indium is diffused on CdS thin films at 500℃ for an hour, the sheet resistivity of their thin films is 1300Ω/□. CdS : In films have carrier concentration 1.2×10^(18)㎝-³, mobility 1.8㎝-²/V-sec and resistivity 1.3×10^(-2)Ω-㎝ at room temperature.<br/> The profiles of photoluminescence spectra of CdS : In films show Gaussian type curves at 20K, the maximum peak is located at the wavelength of 510 ㎚. The peaks of the spectral responses is located at the wavelength of 500 ㎚ at room temperature. The sensitivities γ of the best CdS photoconductive cells have 0.77, and its maximum allowable dissipated power 120 ㎽. Its rise time has 6 msec, and its decay time 20 msec.

HWE법에 의한 CdS 단결정 박막의 성장

양동익(Dong Ik Yang),최용대(Yong Dae Choi),김진배(Jin Bae Kim) 한국진공학회(ASCT) 1992 Applied Science and Convergence Technology Vol.1 No.3

본 연구에서는 HWE 방법에 의하여 GaAs(100) 기판위에 입방정의 단결정 박막을 성장하였다. 성장된 CdS 단결정 박막의 결정구조와 방향을 ECP(electron channeling pattern)로 결정하였다. CdS 박막의 (400)면이 기판과 평행하게 성장됨을 알았다. CdS 박막의 photoluminescence를 20K에서 측정하였는데, free exciton, bound exciton 및 donor-acceptor pair에 의한 발광이 관측되었다. CdS singlecrystalline thin films of zinc blende type are grown on GaAs (100) substrate by semi-closed hot wall epitaxy (HWE) method, and the electro-optical characteristics of films are investigated. The crystal structure and orientation of as-grown CdS thin film are determined by electron channeling pattern. We observed (400) plane of the films grow parallel to substrate surface. Photoluminescence of the CdS films are measured at 20 K. The emissions due to free exciton. bound exciton. and donor-acceptor pair are observed.

E - Beam 증착기법에 의해 성장된 CdS1-xSex 발광소자의 특성연구

양동익(Dong-Ik Yang),박성문(Sung-Mun Park),라경숙(Kyung-Suk La),최용대(Yong-Dae Choi) 한국진공학회(ASCT) 1994 Applied Science and Convergence Technology Vol.3 No.1

본 연구는 CdS, CdSe 분말을 불순물, flux와 혼합하여 질소분위기에서 소결한 후 전자 빔으로 증착하여 적절한 조건에서 열처리 하였다. 이 박막의 결정구조를 X-ray 회절 실험을 통하여 조사하고, 제작된 CdS_(1-x)Se_x 발광 소자의 전기적 특성은 Hall 효과 측정을 이용하고, 광학적 특성은 광발광 및 광전류 스펙트럼, 감도, 최대 허용소비전력, 응답시간 등을 분석하여, 발광소자로서의 기능을 검토하였다. We report the crystal growth and the electro-optical properties of CdS_(1-x)Se_x luminescent films. The CdS_(1-x)Se_x films were grown by electron beam evaporation technique in a high vacuum. X-ray diffraction pattern has been used to examine the structure of the films. The electrical and optical properties of these photoconductive devices have been studied by Hall effect measurments; PL spectra, PC spectra, sensitivity, maximum allowable power dissipation and response time.

Hot - wall epitaxy에 의한 Zn - chalcogenide 에피층의 성장 및 구조적 특성

유영문(Young-Moon Yu),남성운(Sungun Nam),이종광(Jongkwang Rhee),오병성(Byungsung O),이기선(Ki-Seon Lee),최용대(Yong Dae Choi),이종원(J. W. Lee) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.4(1)

열벽적층성장법으로 ZnS 및 ZnTe 단결정 박막을 GaAs(100)와 GaP(100) 기판에 성장하였다. 성장한 박막의 방향성 및 결정성을 알아보기 위하여 X-ray 회절과 이중 결정 요동 곡선(DCRC)을 측정하였다. 성장한 박막은 (100) 방향의 zinc-blende 구조를 갖는 단결정임을 알았다. ZnTe 단결정 박막은 93 arcsec의 아주 좋은 DCRC 반치폭 값을 얻었고 ZnS 단결정 박막도 매우 양호한 결과를 얻었다. 두께에 따른 DCRC 반치폭의 변화로부터 단결정 박막 내에 남아있는 스트레인은 격자부정합에 의한 영향뿐만 아니라 열팽창계수 차이에 의한 것도 있음을 알았다. ZnS and ZnTe epilayers were grown on GaAs(100) and GaP(100) substrates by hot-wall epitaxy. X-ray diffraction revealed that the epilayers have zinc-blende structure and were grown in (100) direction. The small values of the full width at half maximum (FWHM) of double crystal rocking curve (DCRC) showed high quality of the epilayers. From the thickness dependence of the FWHM of DCRC, the strain remaining in films is found to be due to the thermal expansion difference as well as due to the lattice mismatch.

나노 결정립 Fe - Al - O 산화막의 미세구조 변화에 따른 연자기적 특성 분석

이영우(Young-woo Lee),박범찬(Bum-chan Park),김종오(Chong Oh Kim),문지현(Ji-hyun Moon),최용대(Yong-dae Choi) 한국자기학회 2004 韓國磁氣學會誌 Vol.14 No.2

We investigated the soft magnetic properties of nanocrystalline Fe-Al-O film as etching the oxide film with ion beam etching method. It is thought that the grain size of Fe-Al-O film increases as the thickness decreases. The coercivity and squareness increase with decreasing thickness. The surface curvature of AFM images increases when the etching experiment proceeds. This phenomena could be due to the grain growth which occurs during sputtering. This grain growth could be assisted by the the plasma energy during sputtering. Therefore proper thickness should be searched to acquire the good soft magnetic properties for the nanocrystalline film material. Good soft magnetic properties of Fe-Al-O film was acquired at the thickness of more than 900 ㎚.

GaAs(100) 기판에 대한 열에칭이 ZnTe 에피층에 미치는 영향

남성운(Sungun Nam),윤영문(Young-Moon Yu),오병성(Byungsung O),이기선(Ki-Seon Lee),최용대(Yong Dae Choi),정호용(Ho-Yong Chung) 한국진공학회(ASCT) 1998 Applied Science and Convergence Technology Vol.7 No.4

기판에 대한 열에칭이 에피층에 미치는 영향을 조사하기 위하여 ZnTe 에피층을 hot wall epitaxy (HWE)에 의하여 기판 온도 450~630℃에서 GaAs(100) 기판위에 성장하여 에피층에 대한 이중 결정 요동 곡선(DCRC)과 광발광(PL)을 측정하였다. ZnTe 에피층의 DCRC의 반치폭은 GaAs 기판의 열에칭 온도가 510℃와 590℃일 때 가장 작았다. 그러나 550℃ 근처에서 반치폭 값들은 표면 원자들의 재구성에 의하여 증가하였다. 그리고 490℃ 이하의 열에칭 온도에서는 산화막에 의하여 반치폭은 증가하였고, 또 610℃ 이상에서는 표면 결함에 의하여 증가하였다. PL로부터 가벼운 양공 자유엑시톤 X_(1s, lh)과 2차 공명 라만선의 반치폭은 550℃ 근처에서 증가하였다. 열에칭 온도가 증가함에 따라 Y-band의 세기와 GaAs 위의 산화막에 관련된 산소에 속박된 자유엑시톤(OBE) 피크의 세기는 일반적으로 감소하였다. 이러한 실험적인 결과로부터 GaAs 기판의 열에칭은 ZnTe 에피층에 영향을 주는 것으로 확인되었다. To investigate an influence of the thermal preheating for the substrates exerted on the heteroepilayers, the ZnTe epilayers are grown on the GaAs (100) at the substrate temperature of 450~630℃ by hot wall epitaxy (HWE). For this purpose, double crystal rocking curve (DCRC) and photoluminescence (PL) are measured. The full widths at half maximum of DCRC are the smallest in the ZnTe epilayers grown on the GaAs thermally etched at around both 510℃ and 590℃. However, at around 550℃ they increase due to the reconstruction of the atoms in the surface. And they increase due to the oxide layer at below 490℃ and due to the surface defects at above 610℃. From PL analysis, the full widths at half maximum of the light hole exciton X_(1s, lh) and of the second-order Raman line increase at around 550℃. With the increasing preheating temperature, the intensities of Y-bands and of the oxygen bound exciton (OBE) peak related to an oxide layer on the GaAs surface generally decrease. From these experimental results, it′s confirmed that the GaAs substrate thermally etched influences the ZnTe epilayers.