• 한국재료학회지
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• 제2권2호
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• pp.85-94
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• 1992

Plasma 용사된 단열피복에 내재하는 기공의 크기, 형상 및 분포는 피복층 자체의 물성에 지대한 영향을 미치므로 이를 용사변수에 따라 조사하였다. MgO 안정화 지르코니아 피복시 도입되는 기공은 미세기공 외에 각각 생성기구가 다른 조대한 기공 즉 구형과 불규칙한 기공, 그리고 crack으로 구성되었다. 용사거리에 따라 기공의 생성과정과 특성이 변하였으며 Plasma 전류 및 가스 유량의 증가에 의해서 기공도는 감소하는 경향을 보였다. Plasma 가스가 $N_2$인 경우가 Ar보다 더 높은기공도를 보였고 전체적으로 단열피복의 기공도는 10~18%였다. Scratch test로 측정된 단열피복층의 상대적인 경도는 기공도와 높은 상관관계를 보였다.

• Journal of Pharmaceutical Investigation
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• 제24권3호
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• pp.155-165
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• 1994

Some mucoadhesive polymers such as hydroxypropylcelluose (HPC) and carbopol-934 (CP) have been employed for the preparation of mucoadhesive polymeric systems, and their physical properties including mucoadhesion, swelling, and drug release were evaluated. A new simple experimental technique that can quantitatively measure the bioadhesive properties of various polymeric systems has been developed by the methods of detachment force test. As the polymeric systems, the discs of freeze-dried HPC/CP solid dispersions were prepared. The mucosa used in these tests were upper, middle, and lower parts of small intestine of male rats weighing $300{\sim}350\;g$. Detachment forces were increased as the mole fraction of CP increased in discs of HPC/CP solid dispersions. In the points of intestinal site dependence of mucoadhesion, the solid dispersions revealed non-specific mucoadhesion to the intestine. Swelling and drug release characteristics of mucoadhesive polymeric systems were studied extensively to find out the feasibility for the oral controlled delivery systems. Swelling ratio, expressed as the final height/initial height, has been determined in various pH buffer solutions. Hydrochlorothiazide (HCT) was employed as a model drug for release study. Apparent swelling and drug release rate constants, $K_s$ and $K_r$ respectively, were obtained from the square-root time plot of either swelling ratio or released amount of drug, particularly for the time periods before reaching the equilibrium. As a result, the swelling ratio of HPC/CP solid dispersions was increased as the weight percentage of CP increased. Similarly, the release of HCT from the solid dispersions was dependent on pH changes and CP contents, resulted in the slower release of HCT with the increases of pH and CP contents.

• 한국재난정보학회 논문집
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• 제11권2호
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• pp.263-267
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• 2015

본 연구는 국가 주요에너지 시설에 대한 보안진단결과를 분석하여 국가주요 에너지 시설의 보안향상방안을 제안하고자 한다. 대부분의 대상시설은 보안인력, 보안시스템, 울타리, 초소 등에 대한 외형적 보안요소는 적절하게 구축되어 있으나 이러한 보안요소 운용에 대한 인식수준 및 효율성은 낮은 것으로 분석되었다. 보안인력 수요산출의 불균형, 보안시스템 운용에 대한 기본지식 부족, CCTV 운용에 있어 과도한 Pan/Tilt/Zoom 기능 적용으로 인한 사각감시지역 발생, 카메라 위치의 부적절, 모니터 감시효율 저하, 그리고 자체 방호능력과 무관하게 작성된 보안계획서 등 미흡한 점이 있는 것으로 나타났다. 이러한 문제점을 보완하기 위해서 보안관리자의 전문성 제고가 우선되어야 하며, 선발 시 전문성 고려가 없기 때문에 보안관리자를 위한 전문 교육과정 신설이 필요하다. 그리고 보안업무 표준화를 통해 방호업무의 일관성을 유지하고 자체적인 보안진단의 기본 도구로 활용함으로써 보안수준을 향상시킬 수 있을 것으로 보인다.

• 환경생물
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• 제20권4호
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• pp.277-286
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• 2002

An increase in the overall biological effect under the combined action of ionizing radiation with another inactivating agent can be explained in two ways. One is the supposition that synergism may attribute to a reduced cellular capacity of damn-ge repair after the combined action. The other is the hypothesis that synergism may be related to an additional lethal or potentially lethal damage that arises from the interaction of sublesions induced by both agents. These sublesions ave considered to be in-effective when each agent is applied separately. Based on this hypothesis, a simple mathematical model was established. The model can predict the greatest value of the synergistic effect, and the dependence of synergy on the intensity of agents applied, as well. This paper deals with the model validation and the peculiarity of simultaneous action of various factors with radiation on biological systems such as bacteriophage, bacterial spores, yeast and mammalian cells. The common rules of the synergism aye as follows. (1) For any constant rate of exposure, the synergy can be observed only within a certain temperature range. The temperature range which synergistically increases the effects of radiation is shifted to the lower temperature fer thermosensitive objects. Inside this range, there is a specific temperature that maximizes the synergistic effect. (2) A decrease in the exposure rate results in a decrease of this specific temperature to achieve the greatest synergy and vice versa. For a constant temperature at which the irradiation occurs, synergy can be observed within a certain dose rate range. Inside this range an optimal intensity of the physical agent may be indicated, which maximizes the synergy. As the exposure temperature reduces, the optimal intensity decreases and vice versa. (3) The recovery rate after combined action is decelerated due to an increased number of irreversible damages. The probability of recovery is independent of the exposure temperature for yeast cells irradiated with ionizing or UV radiation. Chemical inhibitors of cell recovery act through the formation of irreversible damage but not via damaging the recovery process itself.

• 천문학회보
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• 제36권2호
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• pp.99-99
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• 2011

A statistical study of coronal hole merging and splitting has been performed through Solar Cycle 23. The NOAA/SESC solar synoptic maps are examined to identify inarguably clear events of coronal hole merging and splitting. The numbers of merging events and splitting events are more or less comparable regardless of the phase in the solar cycle. The number of both events, however, definitely shows the phase dependence in the solar cycle. It apparently has a minimum at the solar minimum whereas its maximum is located in the declining phase of the sunspot activity, about a year after the second peak in Solar Cycle 23. There are more events of merging and splitting in the descending phase than in the ascending phase. Interestingly, no event is found at the local minimum between the two peaks of the sunspot activity. This trend can be compared with the variation of the average magnetic field strength and the radial field component in the solar wind through the solar cycle. In Ulysses observations, both of these quantities have a minimum at the solar minimum while their maximum is located in the descending phase, a while after the second peak of the sunspot activity. At the local minimum between the two peaks in the solar cycle, the field strength and the radial component both have a shallow local minimum or an inflection point. At the moment, the physical reason for these resembling tendencies is difficult to understand with existing theories. Seeing that merging and splitting of coronal holes are possible by passage of opposite polarity magnetic structures, we may suggest that the energizing activities in the solar surface such as motions of flux tubes are not exactly in phase with sunspot generation, but are more active some time after the sunspot maximum.

• 사상체질의학회지
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• 제24권3호
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• pp.60-68
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• 2012

Objectives Sasang Constitution (SC) is determined by various physical and psychological attributes. Recently, skin properties have been used effectively to describe SC types in clinics. In this paper, we investigated the constitution dependence of skin elasticity and skin perspiration by using quantitative measurement devices. Methods The skin elasticity of forearm and the skin perspiration of forehead and philtrum were measured in 223 elderly female subjects. To determine the subject's constitution, we adopted the classification results from a newly developed diagnostic tool. For the clarity of constitution, we excluded low-scored subjects in their SC classification. Results & Conclusions As a result, the elasticity hysteresis of forearm (EHFa) of Taeum-in group was significantly less than the EHFa of Soeum-in group. Soeum-in group has high perspiration difference between philtrum and forehead (Diff.PhFh) compared to Taeum-in group in a significance level of .05. Taeum-in and Soeum-in group were significantly classified by EHFa and Diff.PhFh using a Support Vector Machine.

• 천문학회보
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• 제41권1호
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• pp.31.4-32
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• 2016

Observing the solar atmosphere with ground-based telescopes in the near-infrared has a number of advantages when compared to classical measurements in visible wavelengths. One of them comes from the magnetic sensitivity of spectral lines, which varies as ${\lambda}_g$, where g is the effective $Land{\acute{e}}$ factor of the transition. This wavelength dependence makes the near-infrared range adequate to study subtle spatial or temporal variations of the magnetic field. Spectral lines, such as the photospheric Fe I $1.5648{\mu}m$ spectral line, with a $Land{\acute{e}}$ factor g=3, have often been used in the past for this type of studies. To study the chromosphere, the Ca II IR triplet and the He I $1.0830{\mu}m$ triplet are the most often observed lines. The latter has the additional advantage that the photospheric Si I $1.0827{\mu}m$ is close enough so that photosphere and chromosphere can be simultaneously recorded with a single detector in a spectrograph. The instrument TIP (Tenerife Infrared Polarimeter) has been continuously operating since 1999 at the 70-cm German VTT of the Observatorio del Teide and has been recently moved to the 1.5-m German GREGOR. During all this time, results have been obtained concerning the nature of the weak photospheric magnetic field of the quiet sun, magneto-acoustic wave propagation, evolution with the cycle of sunspot magnetic fields, photospheric and chromospheric magnetic field in emerging regions, magnetic field in chromospheric structures such as filaments, prominences, flares, and spicules, etc. In this talk, I will review the main results obtained after all these observations and mention the main challenges for the future. With its novel polarization-free design and a complete suite of instruments aimed at simultaneous (imaging and spectroscopic) observations of the solar photosphere and chromosphere, the EST (European Solar Telescope) will represent a major world-wide infrastructure to understand the physical nature of all these phenomena.

• 보건교육건강증진학회지
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• 제26권4호
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• pp.49-62
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• 2009

Objectives: Few studies have focused on health behaviors and health status among teachers even though these are one of principles and values of WHO's Health Promoting Schools. In this study, we described health behaviors and health status among teachers and explored the differences of these by personal and school characteristics. Methods: A stratified and random cluster sampling design was used to obtain a cross-sectional sample. A total of 59 elementary, middle and high schools in Seoul and Gyeonggi areas were included in which 333 teachers (males 40.6%, females 59.4%) participated in this survey. Chi-square tests were conducted with SPSS 17.1. Results: Overall, health behaviors and health status among teachers were better than the general public according to Korea National Health and Nutrition Examination Survey. Male and middle/high school teachers had higher prevalence of alcohol dependence and of driving under the influence of alcohol. Also, their rate of wearing seat belts were lower compare to female. In other hand, female, health and nutrition teachers, rural school teachers had lower prevalence of meeting recommended levels of physical activity. Underweight were more prevalent to them in contrast to male with higher prevalence of obesity. In addition, teachers of health promoting schools were not likely to ride on a car with a drunk driver. They also have a lower prevalence of skipping breakfast and have higher positive perception of health for themselves. Conclusion: Teachers' health should be given higher concerns as a key component of school based health promotion. Gender and age specific programs should be considered to develop health promoting programs for them.

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권2호
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• pp.134-142
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• 2010

A comparative study on the trade-off between the drive current and the total gate capacitance in double-gate (DG) and triple-gate (TG) FinFETs is performed by using 3-D device simulation. As the first result, we found that the optimum ratio of the hardmask oxide thickness ($T_{mask}$) to the sidewall oxide thickness ($T_{ox}$) is $T_{mask}/T_{ox}$=10/2 nm for the minimum logic delay ($\tau$) while $T_{mask}/T_{ox}$=5/1~2 nm for the maximum intrinsic gate capacitance coupling ratio (ICR) with the fixed channel length ($L_G$) and the fin width ($W_{fin}$) under the short channel effect criterion. It means that the TG FinFET is not under the optimal condition in terms of the circuit performance. Second, under optimized $T_{mask}/T_{ox}$, the propagation delay ($\tau$) decreases with the increasing fin height $H_{fin}$. It means that the FinFET-based logic circuit operation goes into the drive current-dominant regime rather than the input gate load capacitance-dominant regime as $H_{fin}$ increases. In the end, the sensitivity of $\Delta\tau/{\Delta}H_{fin}$ or ${{\Delta}I_{ON}}'/{\Delta}H_{fin}$ decreases as $L_G/W_{fin}$ is scaled-down. However, $W_{fin}$ should be carefully designed especially in circuits that are strongly influenced by the self-capacitance or a physical layout because the scaling of $W_{fin}$ is followed by the increase of the self-capacitance portion in the total load capacitance.

• Smart Structures and Systems
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• 제17권1호
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• pp.73-89
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• 2016

The stress dependence of ultrasonic wave velocity is known as the acoustoelastic effect. This effect is useful for stress monitoring if the acoustoelastic coefficient of a subject medium is known. The acoustoelastic coefficients of metallic materials such as steel have been studied widely. However, the acoustoelastic coefficient of concrete has not been well understood yet. Basic constituents of concrete are water, cement, and aggregates. The mix proportion of those constituents greatly affects many mechanical and physical properties of concrete and so does the acoustoelastic coefficient of concrete. In this study, influence of the water-cement ratio (w/c ratio) and the fine-coarse aggregates ratio (fa/ta ratio) on the acoustoelastic coefficient of concrete was investigated. The w/c and the fa/ta ratios are important parameters in mix design and affect wave behaviors in concrete. Load-controlled uni-axial compression tests were performed on concrete specimens. Ultrasonic wave measurements were also performed during the compression tests. The stretching coda wave interferometry method was used to obtain the relative velocity change of ultrasonic waves with respect to the stress level of the specimens. From the experimental results, it was found that the w/c ratio greatly affects the acoustoelastic coefficient while the fa/ta ratio does not. The acoustoelastic coefficient increased from $0.003073MPa^{-1}$ to $0.005553MPa^{-1}$ when the w/c ratio was increased from 0.4 to 0.5. On the other hand, the acoustoelastic coefficient changed in small from $0.003606MPa^{-1}$ to $0.003801MPa^{-1}$ when the fa/ta ratio was increased from 0.3 to 0.5. Finally, it was also found that the relative velocity change has a linear relationship with the stress level of concrete.