• Applied Biological Chemistry
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• 제41권6호
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• pp.431-436
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• 1998

통전가열(ohmic heating)을 사과주스의 가열 살균에 적용해보기 위하여 가열기 형태와 전압, 파형, 주파수 등 전기적 요소가 사과주스 모델용액의 통전가열 속도에 미치는 영향을 알아보았다. 100 VAC, 60 Hz의 상용전류를 이용한 통전가열시 컬럼형 가열기에서 전극간의 간격이 29, 22, 17 mm로 줄어듬에 따른 모델용액의 가열속도는 $7.8,\;21.0,\;47.4^{\circ}C/min$으로 크게 증가하였으며 또한 전극의 수를 병렬로 1, 2, 3쌍으로 증가시킬 시에도 $29.2,\;49.8,\;74.6^{\circ}C/min$으로 비례적으로 증가하여 전극의 간격이 작을수록, 전극의 표면적이 증가할수록 가열속도는 크게 빨라지는 것으로 나타났다. $60\;Hz{\sim}60\;kHz$ 범위의 주파수 변화에 따른 가열속도 차이는 나타나지 않았으며 파형에 따른 가열속도는 positive saw tooth wave를 제외하고 변화가 거의 없었다. 전압을 40에서 100 VAC로 높임에 따라 가열속도는 $9.5^{\circ}C/min$에서 $83^{\circ}C/min$로 크게 증가하여 전압과 가열속도는 정비례 관계가 있음을 알 수 있었다. 통전가열과 상업적 살균방법으로 제조한 사과주스 간에는 이화학적 특성의 차이가 없었다.

• 한국초전도ㆍ저온공학회논문지
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• 제17권3호
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• pp.37-40
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• 2015

Recently, the electrical insulation design for electrical apparatuses is important to cope with the tendency of high voltage. The degradation characteristics of a superconducting coil due to an electrical breakdown should be considered to design a high voltage superconducting coil. In this paper, the degradation characteristics of 2G high temperature superconducting (HTS) wires are studied with respect to electrical breakdown tests. To analyze the dependency of the degradation characteristics of 2G HTS wires, the electrical breakdown tests are performed with AC(alternating current) and DC(direct current) voltage. All tests are performed by applying various magnitudes of AC and DC breakdown voltages. To verify the degradation characteristics of 2G HTS wires, the tests are performed with various 2G HTS wires with respect to stabilizer materials. The degradation characteristics of 2G HTS wires, such as Ic(critical current) and index number are measured by performing electrical breakdown tests. It is found that the characteristics such as Ic and index number can be degraded by an electrical breakdown. Moreover, it is concluded that the degradation characteristics of 2G HTS wires are affected by the stabilizer material and applied voltages. The cross-sectional view of 2G HTS wires is observed by using a scanning electron microscope (SEM). As results, it is found that the degradation characteristics of 2G HTS wires are concerned with hardness and electrical conductivity of stabilizer layers.

• 한국가정과교육학회지
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• 제7권2호
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• pp.1-18
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• 1995

The purpose of this study was to investigate the teachers’attitudes toward the middle and high school student uniform. The questionnaire included independent variables about teacher themselves and school surroundings, and questions about teachers’attitudes toward school uniform. The participants were 316 middle and high school teachers in Chonbuk province. Means, standard deviations, frequencies, and percentages were calculated. ANOVA test was used for differences and scheffe-test was followed. The results were: 1. Teachers were content with “Students in uniform are upright and look more studentlkie.”“It’s easy to supervise students outdoors.”, and “There’s few efficiencies in coping with the temperature alternating.”, “Students in uniform hardly can reveal their originality.”and “It’s inconvenient for the students to be dynamic in uniform.” 2. Teachers in high schools and in private schools showed more positive attitudes toward uniform. And the male teachers, teachers graduated from general college, married teachers, and teachers who have a career of more than 20 years showed more positive attitudes toward uniform. More variables concerned about teacher themselves showed more significant differences than those about school surroundings. 3. Most of teachers showed positive attitudes toward uniform. The rank order of the reasons for the teacher’s positive attitudes were “Students in uniform are upright and look more studentlike.”, “It’s easy to supervise students outdoors.”, and “There’s no noticible distinction between the rich and the poor students.”The rank order of the reason for the teachers’negative at titudes were “Student in uniform could hardly reveal their originality.”, “It’s inconvenient for the student to be dynamic in uniform.”, and ”As they have to get the street clothes besides, economic burden becomes double in reality.”4. More than half of the teachers who are working at schools with uniform showed positive attitudes toward uniform. The rank order of reasons for the teachers’positive attitudes were “Students in uniform are upright and look more studentlike.”,“It’s easy to supervise students outdoors.”and “Economic burden could be decreased.”“The rank order of the reasons for the negative attitudes were “It’s inconvenient for the student to be dynamic in uniform.”, “Students in uniform could hardly reveal their originality.”, and “Students cannot feel free in mind with uniform.”5. Teachers overall showed positive attitudes toward uniform whether they work ar schools with uniform or without it.

• 천문학회지
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• 제51권1호
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• pp.5-16
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• 2018

We investigate the escape of $Ly{\beta}$ from emission nebulae with a significant population of excited hydrogen atoms in the level n = 2, rendering them optically thick in $H{\alpha}$. The transfer of $Ly{\beta}$ line photons in these optically thick regions is complicated by the presence of another scattering channel leading to re-emission of $H{\alpha}$, alternating their identities between $Ly{\beta}$ and $H{\alpha}$. In this work, we develop a Monte Carlo code to simulate the transfer of $Ly{\beta}$ line photons incorporating the scattering channel into $H{\alpha}$. Both $H{\alpha}$ and $Ly{\beta}$ lines are formed through diffusion in frequency space, where a line photon enters the wing regime after a fairly large number of resonance scatterings with hydrogen atoms. Various line profiles of $H{\alpha}$ and $Ly{\beta}$ emergent from our model nebulae are presented. It is argued that the electron temperature is a critical parameter which controls the flux ratio of emergent $Ly{\beta}$ and $H{\alpha}$. Specifically for $T\;=\;3{\times}10^4\;K$ and $H{\alpha}$ line center optical depth $\tau{\alpha}\;=\;10$, the number flux ratio of emergent $Ly{\beta}$ and $H{\alpha}$ is ~ 49 percent, which is quite significant. We propose that the leaking $Ly{\beta}$ can be an interesting source for the formation of $H{\alpha}$ wings observed in many symbiotic stars and active galactic nuclei. Similar broad $H{\alpha}$ wings are also expected in $Ly{\alpha}$ emitting halos found in the early universe, which can be potentially probed by the James Webb Telescope in the future.

• 한국재료학회지
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• 제12권4호
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• pp.296-303
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• 2002

For potential application to quantum mechanical devices, nano-composite thin films, consisting of GaAs quantum dots dispersed in SiO$_2$ glass matrix, were fabricated and studied in terms of structural, chemical, and optical properties. In order to form crystalline GaAs quantum dots at room temperature, uniformly dispersed in $SiO_2$matrix, the composite films were made to consist of alternating layers of GaAs and $SiO_2$in the manner of a superlattice using RF magnetron sputter deposition. Among different film samples, nominal thickness of an individual GaAs layer was varied with a total GaAs volume fraction fixed. From images of High Resolution Transmission Electron Microscopy (HRTEM), the formation of GaAs quantum dots on SiO$_2$was shown to depend on GaAs nominal thickness. GaAs deposits were crystalline and GaAs compound-like chemically according to HRTEM and XPS analysis, respectively. From measurement of optical absorbance using a spectrophotometer, absorption edges were determined and compared among composite films of varying GaAs nominal thicknesses. A progressively larger shift of absorption edge was noticed toward a blue wavelength with decreasing GaAs nominal thickness, i.e. quantum dots size. Band gaps of the composite films were also determined from Tauc plots as well as from PL measurements, displaying a linear decrease with increasing GaAs nominal thickness.

• 대한화학회지
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• 제27권4호
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• pp.287-293
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• 1983

자유라디칼 개시제에 의한 디에틸 ${\alpha}$-페닐비닐 인산(DEPVP)과 아크릴로니트릴(AN) 및 말레산 무수물(MAnh)의 혼성중합 연구를 행하였다. 개시제로는 과산화벤조일을 사용하였으며 중합온도는 $70^{\circ}C$이었다. 단위체 반응성비는$ r_1(AN) = 0.77, r_2(DEPVP) = 0.002 $이었으며, 이 값으로 부터 DEPVP의 Alfrey-Price 상수 Q=0.012, e=-1.35를 얻었다. 이와 대조적으로 DEPVP와 MAnh와의 자유라디칼 혼성중합은 과산화 벤조일을 개시제로 사용하여 $70^{\circ}C$에서 클로로포름 용액중에서 행한 결과 초기 단위체의 농도비에 무관하게 1 : 1 교대 혼성 중합체를 형성하였으며, 두 단위체의 몰비가 MAnh / DEPVP = 7 / 3일때 중합속도가 최대였다. 핵자기 공명 분광법으로 구한 DEPVP와 MAnh의 전하이동 착물의 평형상수는 $21^{\circ}C$ 클로로포름 용액에서 0.085 l/mol이었다. 혼성 중합체중 DEPVP의 함량이 증가함에 따라 AN/DEPVP 쌍에서는 환산점성도가 감소함을 보였고 MAnh/DEPVP쌍에서는 변화가 별로 없었다

• 폴리머
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• 제33권3호
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• pp.248-253
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• 2009

의료용으로 적용될 수 있는 새로운 재료를 제조하기 위하여 폴리카프로락톤(PCL)과 양친성 구조를 갖는 폴리(에틸렌 글리콜)(PEG)이 그래프트된 PCL을 이용하여 생분해성 블렌드를 제조하였다. 제조된 블렌드는 PCL을 기본으로 하고 여기에 그래프트 공중합체의 함량을 변화시키며 열적 그리고 결정화 특성을 관찰하였다. 그래프트 공중합체의 함량 변화에 따라 결정화 온도의 변화 및 결정화 속도가 변화하였고 이를 통해 그래프트 공중합체가 PCL의 결정화 거동에 영향을 미침을 확인하였다. 이는 광학현미경을 통한 결정의 교대 소광 밴드의 관찰을 통하여서도 확인할 수 있었다. 약물방출시스템과 같은 의료용 응용을 고려하여 블렌드 필름의 흡수거동과 단백질 흡착에 대한 특성도 평가하였다.

• 천문학회보
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• 제41권1호
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• pp.45.1-45.1
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• 2016

Spatially rotating magnetic fields have been observed in the solar wind and in the Earth's magnetopause as well as in reversed field pinch (RFP) devices. Such field configurations have a similarity with extended current layers having a spatially varying plasma pressure instead of the spatially varying guide field. It is thus expected that magnetic reconnection may take place in a rotating magnetic field no less than in an extended current layer. We have investigated the spontaneous evolution of a collisionless plasma system embedding a rotating magnetic field with a two-and-a-half-dimensional electromagnetic particle-in-cell (PIC) simulation. In magnetohydrodynamics, magnetic flux can be decreased by diffusion in O-lines. In kinetic physics, however, an asymmetry of the velocity distribution function can generate new magnetic flux near O- and X-lines, hence a dynamo effect. We have found that a magnetic-flux-reducing diffusion phase and a magnetic-flux-increasing dynamo phase are alternating with a certain period. The temperature of the system also varies with the same period, showing a similarity to sawtooth oscillations in tokamaks. We have shown that a modified theory of sawtooth oscillations can explain the periodic behavior observed in the simulation. A strong guide field distorts the current layer as was observed in laboratory experiments. This distortion is smoothed out as magnetic islands fade away by the O-line diffusion, but is soon strengthened by the growth of magnetic islands. These processes are all repeating with a fixed period. Our results suggest that a rotating magnetic field configuration continuously undergoes deformation and relaxation in a short time-scale although it might look rather steady in a long-term view.

• 대한지리학회지
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• 제33권3호
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• pp.377-394
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• 1998

화분분석이나 연륜분석 같은 전통적인 고기후 연구 방법론이 이용되기 어려운 육상 환경하에서. 토양내 자성 특성은 제4기 기후 연구의 수단중 가장 좋은 수단 중 하나가 되었다. 본 연구에서는 미국 중부 평원지역에서 제4기말 위스컨신 빙하기와 흘로세에 퇴적된 고토양/뢰스 층에서 자성변수들의 층서에 따른 대자율과 잔류자기의 특성을 연구하였다. 고토양에는 자성물질 집적이 많고. 잔류자기의 특성도 토양화의 영향으로 크기가 작은 2차 자성광물의 존재를 보이는데 비하여, 빙하기의 풍화정도가 약한 뢰스에서는 집적량이 적고 입자가 큰 1차 광물이 많은 것으로 나타났다. 자성변수들은 기후에 민감한 것으로 알려진 다른 생물학적 지표들과의 높은 상관관계를 통해 기후변화를 잘 반영하는 것으로 나타났다.

• 한국자기학회지
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• 제10권1호
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• pp.11-15
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• 2000

수분사법으로 제조된 13Cr-1.5Nb-Fe 합금분말을 수소분위기 하에서 환원처리 하였다. 분말특성이 조사된 환원분말을 이용하여 자기코아를 제작한 후 약 $10^{-5}$Torr의 진공분위기에서 소결하였다. 자기코아의 교류자기특성을 조사하기 위하여 투자율과 자기손실을 조사하였다. 환원분말의 입도분포는 약 70$\mu\textrm{m}$에서 50% vol.을 나타내며, 포화자화 값은 약160 emu/g이었다. 10ton/$\textrm{cm}^2$ 성형압력, 1,20$0^{\circ}C$ 소결온도에서 제작된 자기코아의 교류투자율은 주파수, f=1 kHz, 인가자장, H$_{a}$ =5 Oe에서 400이다. 또한 동조건에서 제작된 자기코아의 교류자기이력손실은 유도자화, B$_{m}$ =80G에서 0.12mW/cc이다.