• 공업화학
• /
• 제22권6호
• /
• pp.672-678
• /
• 2011

연구에서는 니켈 함량에 탄소섬유강화 에폭시 기지 복합재료의 전자파 차폐효과에 대해 고찰을 위해 탄소섬유표면에 시간의 변수에 따른 무전해 도금을 실시하였다. 탄소섬유 표면의 특성은 주사전자현미경과 X-선광전자분광법으로 측정하였고 전기적 특성은 4단자법으로 분석을 진행하였다. 복합재료의 전자파 차폐효과는 흡수와 반사 두 가지 방법으로 분석을 진행하였다. 실험 결과로부터 전자파 차폐효과는 탄소섬유 표면에 코팅된 니켈 함량이 증가됨에 따라 순차적으로 증가되는 것이 확인되었으나, 고주파 영역에서는 과량의 니켈 도금이 더 이상의 전자파 차폐효율을 증가시키지 않는 것이 확인되었다. 결론적으로 니켈 함량이 탄소섬유 복합재료의 전자파 차폐효과를 결정하는 요소가 될 수 있다고 판단되나, 특정 주파수마다 최적화된 금속도입 함량에 대한 변수가 있을 수 있다고 판단된다.

• 유통과학연구
• /
• 제12권11호
• /
• pp.45-53
• /
• 2014

Purpose - Goal setting is effective in any domain in which an individual or group has some control over the outcomes. It applies not only to work tasks but also to sports and health, and in various other settings. Its success depends on considering the mediators and moderators determining its efficacy and applicability. This study investigates the individual factors influencing academic goal attainability. Unlike previous studies, we focused on the effect of the relationships between individual traits (passion, tenacity, self-control) and specific motivation (vision, self-efficacy, implementation intentions) with academic goal attainability, rather than the effects of the relationship between commitment and the goal shielding mechanism with goal attainability. Research design, data, and methodology - Data collected through questionnaires were analyzed by the SPSS program. A total of 293 school students, who participated in the TOEIC program, participated in the survey. Slightly more than half were female (male: n=145 vs. female: n=148). We verified nine hypotheses through various statistical methods (reliability analysis, exploratory factor analysis, confirmatory factor analysis, structural equation model for the hypothesis test, bootstrapping test for the mediation test). Results - Data was analyzed in three phases. The first phase involved measurement analysis (i.e., item purification and factor structure confirmation), involving the scales of the three variables of individual traits, three mechanism variables, and goal attainability. The second phase involved estimating the proposed structural relationships among the key constructs (see Figure 1), using the results to test H1 to H9. The final phase involved examining the mediating effects of the three variables (vision, implementation intention, and self-efficacy). The research model shows that the independent variable passion has a significant result with both the mediators-vision and self-efficacy. Further, vision and self-efficacy significantly affect goal attainability. The second variable, self-control, shows a significant effect when mediated by implementation intentions, but the direct relationship between implementation intension and goal attainability shows an insignificant result. However, when further mediated by self-efficacy, it showed a significant effect between self-efficacy and goal attainability. Similarly, the third variable, tenacity, shows an insignificant result when mediated by vision. In contrast, the mediator self-efficacy shows a positive effect between tenacity and goal attainability. Conclusions - This study shows how these individual traits, when mediated with the appropriate motivational factors, resulted significantly in the attainability of academic goals. We may identify several theoretical and practical contributions. Theoretically, we developed a step further in the research into consumer goals and related studies. Future research could examine the effects of different learning goal types and their combinations with performance goals (e.g., learning goals first, then performance goals), different types of goal framing (approach success vs. avoid failure), the relation between goals and cognition (which, by implication, entails all of cognitive psychology), goal hierarchies, and macro goal studies with organizations of different sizes. More studies on the relationship between conscious and subconscious goals would also be valuable.

• 대한방사선기술학회지:방사선기술과학
• /
• 제45권6호
• /
• pp.523-529
• /
• 2022

Gamma spectroscopy analysis is widely used for radioactivity analysis, and various factors are required for radioactivity calculations. Among the factors, K3 for each sample significantly influences the results. The previous methods of correcting the self-absorption effect include a computational simulation method and a method that requires making a CRM(certified reference material) identical to the sample medium. However, the above methods have limitations when used in small institutions because they require specialized program utilization skills or high manufacturing costs and large facilities. The aim of this study is to develop a method that can be easily and rapidly applied to radioactivity analysis. After filling the beaker with water, we placed the radiation source in a uniform position and used the measured value as the benchmark. Next, a correction factor was derived based on the difference in the radiation source count of the benchmark and the identically measured sample. For the radiation source, Eu-152, which emits a broad range of energy within the measurement range of gamma rays, and Cs-134 and Cs-137, which are indicator nuclides in environmental radiation analysis, were used. The sample was selected within the density range of 0.26-2.11 g/cm³, and the correction factor was derived by calculating the count difference of each sample compared to the reference value of water. This study presents a faster and more convenient method than the existing research methods for determining the self-absorption effect correction, which has become increasingly necessary.

• 폴리머
• /
• 제36권6호
• /
• pp.745-755
• /
• 2012

Two types of polymers were tested in this study; poly(ethylene terephthalate) (PET) as a synthetic example and poly(lactic acid) (PLA) as a natural polymer. DSC analyses showed that the use of nanofiller increased the degree of crystallinity ($X_c$) of both PET and PLA polymers, but the effect was more noticeable on PET nanocomposites. The crystallization of PLA and PET nanocomposites occurred at higher temperatures in comparison to neat polymers. According to dynamic mechanical-thermal analysis (DMTA), the damping factor of PET/$TiO_2$ nanoparticles decreased compared to the neat matrix, but for PLA nanocomposites the opposite trend was observed. Results of the mechanical test showed that for both PET and PLA nanocomposites, the most successful toughening effect was observed at 3 wt% loading of $TiO_2$ nanoparticles. SEM micrographs revealed uniform distribution of $TiO_2$ nanoparticles at 1 and 3 wt% loading levels. The results of WAXD spectra explained that the polymorphs of PLA and PET was not affected by $TiO_2$ nanoparticles. UV-visible spectra showed that $TiO_2$ nanocomposite films had high ultraviolet shielding compared to neat polymer, but there was significant reduction in transparency.

• Progress in Superconductivity
• /
• 제9권1호
• /
• pp.50-55
• /
• 2007

We have installed a 61-channel magnetocardiography (MCG) system inside a magnetically shielded room (MSR) with a size of $2.4\;m\;{\times}2.4\;m\;{\times}2.4\;m$. The MCG system consists of 1st-order axial gradiometers containing double relaxation oscillation SQUIDs (DROSs) with pick-up coils of a base line of 70 mm. The MSR holds a shielding factor of 50 at 0.1 Hz and 10000 at 100 Hz, when its door in the middle on a front wall is closed. On opening the MSR door, we have obtained the characteristics of the MCG system with a 2.9 Hz noise generated from an air conditioning unit at 13 m distance off the MSR. In an open-door MSR ($140^{\circ}$ opening), a noise at the center channel increases up to $700\;fT/Hz^{l/2}$ at 2.9 Hz and $1.7\;pT/Hz^{1/2}$ at 60 Hz. MCG signals for a healthy human do not show distortion until the door opens to $45^{\circ}$, but show the effect of noise when the door opens further at $90^{\circ}$ and $140^{\circ}$. With the door opens to $45^{\circ}$, MCG measurement can be performed with ease of door operation and without creating claustrophobia for the patient.

• 한국안전학회지
• /
• 제21권4호
• /
• pp.60-65
• /
• 2006

It is a well known fact that LCD is a central part of the IT industry which is important in the present and the future. But the biggest problem of LCD manufacturing is maintaining a cleaning room environment and administration. Therefore the purpose of this study is to first, prevent the yield depreciation and damage of products, and second, protect the worker ftom accidental electrostatic discharge during LCD manufacture. The soft x-ray ionizer is a type of electrostatic reducer device. It protects against electrostatic discharge in the cleaning room environment and is a necessary environmental factor during LCD production. The positive aspects of the soft x-ray are its shorter time and wider angle of exposure. But the negative aspect of the soft x-ray is its need for several shielding of protection from the harmful x-ray exposure. On this study, the development of the Air Nozzle-type ionizer to amend and refine some problems. For example, examined the electrostatic reduce device of a soft x-ray type and discovered the ion did not go inside well. also workers to be free from danger. An Air Nozzle-type ionizer is comprised of soft x-ray radiation and ionized air production. Air is injected through the nozzle after being ionized from radiation. It supplies air keeping the same pressure into the end foundation of ion production. The soft x-ray is the structure which radiates ionized air through the nozzle (21 holes) having micro holes of the ionizable radiation after ionizing the inside air by the ion production. A worker does not need a cover to protect against x-rays and the Air Nozzle-type ionizer is easy to set up and is more effective at eliminating electrostatic.

• 한국항행학회논문지
• /
• 제19권3호
• /
• pp.230-236
• /
• 2015

본 논문에서는 접지전극이 상호 간섭의 문제가 발생했을 때 파급효과가 큰 차폐시스템의 패넬과 접지전극으로 널리 사용되고 있는 봉상전극, 메쉬전극, 판상전극을 2차원에 점 전류원의 집합체로 가정하여 이에 대한 전극표면전위를 이용하였다. 실험에 사용한 수조모델의 유한성과 축척에 의해 제작된 모델전극의 축척한계를 수조모델의 크기에 대해 실험오차에 따른 중단오차를 최대한 줄이는 수법으로 실험모델전극을 선정하였다. 복수의 접지도체가 동일 접지저항구역 내에 존재할 경우 도체의 형상 및 매설 조건에 따른 간섭효과의 척도로 사용되는 전위간섭계수의 도출 방법을 제시하였다. 또한 실험에 사용한 접지전극의 수치시뮬레이션을 통해 이론의 타당성을 검증하고, 검증된 이론과 모의실험을 통해 본 연구를 구체화 하였다.

• Radiation Oncology Journal
• /
• 제2권2호
• /
• pp.271-280
• /
• 1984

The peripheral dose, defined as the dose outside therapeutic photon fields, which is responsible for the functional damage of the critical organs, fetus, and radiation. induced carcinogenesis, has been investigated for $^{60}Co\;\gamma$ ray and 10 MV Xray. It was measured by silicon diode controlled by semiautomated water phantom without any shielding or with lead plate of HVL thickness put horizontally or vertically to shield stray radiations. Authors could obtain following results. 1. The peripheral dose was larger than $0.7\%$ of central axis maximum dose even at 20cm distance from field margin. That is clinically significant, so it should be reduced. 2. Even for square fields of 10 MV Xray, radial peripheral dose distribution did not coincide with transverse distribution, because of the position of collimator jaws. 3. Between surface and $d_m$, the peripheral dose distributions show a pattern of the dose distribution of electron beams and the maximum doss was approximately proportional to the length of a side of square field. 4. The peripheral doses depended on radiation quality, field size, distance from field margin and depth in water. Distance from field margin was the most important factor. 5. Except for near surface, the peripheral dose from phantom was approximately equal to that from therapy unit. 6. To reduce the surface dose outside fields, therapist should shield stray radiations from therapy unit by lead plate of at least one HVL for 10 MV X-ray and by bolus equivalent to tissue of 0.5cm thickness for $^{60}Co$. 7. To reduce the dose at depth deeper than $d_m$, it is desirable to shield stray radiations from therapy unit by lead.

• Journal of Welding and Joining
• /
• 제16권4호
• /
• pp.39-46
• /
• 1998

$CO_2$ gas shielded arc welding has been characterized with its harsh arc compared to Ar-based shielding gases and with its high level of spattere specially in welding current range of 250~300 amperes. In this range of welding current, the metal transfer mode showed to be changed from short circuit to globular with the increase of welding voltage resulting in so-called the transitional mode in which both modes of transfer appeared together. To characterize the transitional mode, the short circuit events were divided into two groups, i.e. normal short circuit (N.S.C) which has short circuit time $(t_s)$ over 2msec and instantaneous short circuit (I.S.C) of $t_s$$\leq$2msec. The experimental results showed that the number of N.S.C decreased almost linearly with the increase of welding voltage and appeared to be not related with spatter generation rate. However I.S.C became to be pronounced in the transitional condition and its number reached the maximum value at around 29.0 volts. Considering the relation with the spatter generation rate, it was found that the number of I.S.C had a very strong correlation with the spatter generation rate of the transitional condition. It was further demonstrated that spatter generation rate decreased quite linearly with the decrease of I.S.C frequency. It implies that I.S.C is the most important waveform factor controlling the spatter generation of the transitional mode, i.e. in the middle range of welding current. Based on these results, It was discussed that in the transitional mode the basic concept of waveform control for suppressing spatter generation would be different from the one applied for typical short circuit transfer mode of low welding current.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
• /
• pp.101-105
• /
• 2001

고압용 가교 Polyethylene 절연 케이블의 도체와 절연체 사이, 절연체와 외부 차폐층 사이에는 계면에서의 부분방전을 방지하고 전기적 스트레스를 완화할 목적으로 반도전층이 설계되어 있다. 이 반도전층의 성질은 케이블의 품질과 신뢰성에 매우 중요한 관련이 있다. 일반적으로 반도전층은 압출 성형하는데 Base Polymer에 다량의 카본블랙을 혼합하여 도전화 한다. 절연층과 반도전층간 계면의 평활도는 전력 케이블의 수명과 깊은 관계가 있는데 만약 평활도가 좋지 않으면 전기적 Stress 가 증가하여 전선 수명이 짧아진다. 계면 평활도를 나쁘게 하는 주 요인은 계면의 Void, 반도전층의 돌기와 이물, 탄화물 등이다. 반도전 Compound 제조에 있어서 Carbon Black의 선택과 분산성은 전선수명을 결정하는 중요한 요소이다.