• Title/Summary/Keyword: stress reduce

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Curing behavior of Photo-Curable Materials by Photo-Shrinkage Test (광원 경화형 소재의 수축률평가를 통한 광경화 거동 평가)

  • Park, Ji-Won;Bae, Kyung-Yul;Kim, Pan-Seok;Lim, Dong-Hyuk;Kim, Hyun-Joong;Cho, Jin-Ku;Kim, Baek-Jin;Lee, Sang-Hyeup
    • Journal of Adhesion and Interface
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    • v.11 no.2
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    • pp.57-62
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    • 2010
  • Photo-curable material can be crosslinked among molecules by light source such as UV and visible light materials. Material properties are controlled by crosslink reaction. Shrinkage is occured during the curing reaction of material structure. Phenomenon of shrinkage stress occurs inside the product and reduce the stability of the product causes problems. Heat shrink the evaluation of the phenomenon has been formalized. But the evaluation of photo shrink is not enough. In this experiment, real-time contract with shrinkage tester phenomena and analysis degree of shrinkage of the material differences. According to the research, experimental results and theoretical analysis of the results were big differences. Shrinkage, especially for a number of different functional groups that were very different theory. These differences are occurred by the molecular structure different and not enough reaction.

Convergence analysis of determinants affecting on geographic variations in the prevalence of arthritis in Korean women using data mining (데이터마이닝을 이용한 여성 관절염 유병률 소지역 간 변이의 융복합 요인분석)

  • Kim, Yoo-Mi;Kang, Sung-Hong
    • Journal of Digital Convergence
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    • v.13 no.5
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    • pp.277-288
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    • 2015
  • This study aims to identify determinants affecting on geographic variations in the prevalence of arthritis in Korean women using data mining. Data from Korean Community Health Survey 2012 with 249 small districts were analyzed. Socio-demographic, health behavior and status, and morbidity status measures were analyzed using conventional regression model and convergence analysis method such as decision tree for convergence analysis. Rate of workers in agriculture, forestry, and fishing, salaried workers, persons higher than high school graduates, non-treatment of needing care, non-treatment of care because of economic reason, obesity, heavy drunkers, complaining persons of chewing difficulty, persons with experiencing depression, persons with perceiving stress, and persons with diagnosing hypertension and angina pectoris were variation determinants of prevalence of arthritis in 249 small districts and these districts were classified 10 area groups by decision tree model. Our finding suggest that the approach based characteristics by small area groups rather than national wide or individual level would be effective to reduce in variations of prevalence of arthritis.

Analysis of Experiments for 'Measuring the size of Earth in 8th Science Textbooks

  • Chae, Dong-Hyun
    • Journal of The Korean Association For Science Education
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    • v.30 no.7
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    • pp.901-907
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    • 2010
  • The purpose of this study is to analyze methods for measuring the size of the Earth, put forth in 6 different Korean 8th grade science textbooks. The research questions are as follows: 1) Do they adequately map out the experiments for measuring the size of the earth by using the concept of the sun's altitude? 2) Do they reduce the size of the sun like as the Earth is similarly downsized to the globe? 3) Do they suggest the precise experimental conditions for selecting two equal longitudinal spots for measuring the size of the earth? 4) Do they design adequate experiments for exact measurement? 5) Do they offer a proportional expression for seeking the size of globe which is easily understood by students? 6) Do they develop experiments to measure actual size of the earth? Four graduate students and one researcher took part in this study. All conditions were unanimously agreed upon by the participants. The results are as follows. First, one publishing company must include the concept of the sun's altitude to accurately measure the size of the Earth. However, some textbooks fail to mention this. As such, the concept of the sun's altitude must be introduced to accurately measure the size of the Earth. Second, a reduced size globe is used as the actual earth so; the sun should be factored in with a reduced light value. Third, you have to lay a stress on two points at the same longitude. In other words, a shadow located at the same longitude from two randomly selected points. Most textbooks mention two points at the same longitude but two of them design the experiment with a shadow at the same longitude. Fourth, we need a method to precisely measure the angle between a stick and its shadow. The angle between the stick and the tip of its shadow is the sun's altitude difference. Fifth, we need to present more specific proportional expressions for calculating the size of the globe. Only 3 out of the 6 texts employed a proportional expression. Sixth, we need to calculate the size of the earth by accurately presenting the scale of the globe to attain the goal of the experiment. Two of the texts analyzed, designed the experiment for the purpose of calculating the size of the globe. Three of the texts designed their experiments to calculate the radius of globe which is not even relevant to the purpose of experiment.

Characteristics and Physical Property of Tungsten(W) Related Diffusion Barrier Added Impurities (불순물을 주입한 텅스텐(W) 박막의 확산방지 특성과 박막의 물성 특성연구)

  • Kim, Soo-In;Lee, Chang-Woo
    • Journal of the Korean Vacuum Society
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    • v.17 no.6
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    • pp.518-522
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    • 2008
  • The miniaturization of device size and multilevel interlayers have been developed by ULSI circuit devices. These submicron processes cause serious problems in conventional metallization due to the solubility of silicon and metal at the interface, such as an increasing contact resistance in the contact hole and interdiffusion between metal and silicon. Therefore it is necessary to implement a barrier layer between Si and metal. Thus, the size of multilevel interconnection of ULSI devices is critical metallization schemes, and it is necessary reduce the RC time delay for device speed performance. So it is tendency to study the Cu metallization for interconnect of semiconductor processes. However, at the submicron process the interaction between Si and Cu is so strong and detrimental to the electrical performance of Si even at temperatures below $200^{\circ}C$. Thus, we suggest the tungsten-carbon-nitrogen (W-C-N) thin film for Cu diffusion barrier characterized by nano scale indentation system. Nano-indentation system was proposed as an in-situ and nanometer-order local stress analysis technique.

A Study on the Hydration Reaction Model of Expansive Additive of Ettringite-Gypsum Type (에트링가이트-석탄 복합계 팽장재의 수화반응 모델에 관한 연구)

  • Park Sun Gyu;Takahumi Noguchi;Kim Moo-Han
    • Journal of the Korea Concrete Institute
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    • v.17 no.4 s.88
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    • pp.581-586
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    • 2005
  • High-performance concrete (HPC), which is particularly sensitive to self-desiccation, is required to be durable even in severe environmental conditions, i.e. costal area, cold district, etc. However, in recent years, some attention was particularly given to cracking sensitivity of high performance concrete at early age. It has been argued and demonstrated experimentally that such concrete undergoes autogenous shrinkage due to self-desiccation at early age under restrained condition, nd, as a result, internal tensile stress may develop, leading to micro cracking and macro cracking. This shrinkage-introduced crack produces a major serviceability problem for concrete structures. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive additive for reducing the risk of autogenous shrinkage-introduced cracking. However, the research on hydration model of expansion additive has been hardly researched up to now. This paper presents a study of the hydration model of Ettringite-Gypsum type expansive additive. As a result of comparing forecast values with experiment value, proposed model is shown to expressible of hydration of expansive additive.

A Study on the Wearing Condition and Satisfaction of Pesticide Protective Clothing (농약방제복 착용실태 및 만족도에 관한 연구)

  • Oh, Young-Soon;Lee, Kyung-Suk;Chae, Hye-Seon;Kim, Kyung-Ran;Kim, Sung-Woo
    • Journal of the Korea Fashion and Costume Design Association
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    • v.16 no.4
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    • pp.217-228
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    • 2014
  • The purpose of this study is to grasp inconveniences and improvements by examining wearing condition and satisfaction of protective clothing targeting 114 Korean farmers and to suggest basic data for enhancement of pattern and wearing satisfaction of protective clothing by understanding problems of pesticide-proof clothing through comparative analysis on the size of its commercial products. Most of male subjects were in charge of spraying pesticide, whereas female were most likely to play an assistant role to hold the hose of pesticide applicator. Both of female and male subjects were very aware of the harmful effect of pesticide on human body and tried to take off the clothes immediately after spraying it to reduce possible damage caused by pesticide. As a result of examining wearing condition, the farmers avoided wearing protective clothing because that it feels hot, stuffy, and uncomfortable to move. This hesitant response of wearing the clothing was not shown significantly in case of female subjects who play an assistant role for spraying. Although the farmers wore protective equipments such as mask or gloves in a proper way as compared to protective clothing, they seemed to choose alternative way rather than best way to block pesticide completely. The satisfaction regarding to the fitting of protective clothing which the subjects showed low in all items of upper-lower clothes except waistline. It is necessary to improve the functionality such as relief from heat stress and convenience for movement rather than design or economic in protective clothing development. As a result of comparing the size of five kinds of commercial protective clothing, the farmers got confused to choose the product since designation method of size across companies showed a significant difference in an identical clothing size. In addition, the sizing system developed on a basis of a well-built man has become a hindering factor in wearing satisfaction of female farmers.

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Effective PPG Signal Processing Method for Detecting Emotional Stimulus (감성 자극 판단을 위한 효과적인 PPG 신호 처리 방법)

  • Oh, Dong-Gi;Min, Byung-Seok;Kwon, Sung-Oh;Kim, Hyun-Joong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37 no.5C
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    • pp.393-402
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    • 2012
  • In this study, we propose a signal processing algorithm to measure the arousal level of a human subject using a PPG(Photoplethysmography) sensor. From the measured PPG signals, the arousal level is determined by PPI(Pulse to Pulse Interval) and discrete-time signal processing. We ran psychophysical experiments displaying visual stimuli on TV display while measuring PPG signal from a finger, where the nature landscape scenes were used for restorative effect, and the urban environments were used to stimulate the stress. However, the measured PPG signals may include noise due to subject movement and measurement error, which results in incorrect detections. In this paper, to mitigate the noise impact on stimulus detection, we propose a detecting algorithm using digital signal processing methods and statistics of measured signals. A filter is adopted to remove a high frequency noise and adaptively designed taking into account the statistics of the measured PPG signals. Moreover we employ a hysteresis method to reduce the distortion of PPI in decision of emotional. Via experiment, we show that the proposed scheme reduces signal noise and improves stimulus detection.

A Study on the Difference of Response Characteristics according to Description and Expression Method of Procedures (절차서의 기술 및 표현 방법에 따른 작업자 반응특성 차이 연구)

  • Jang, Tong Il;Lee, Yonghee;Oh, Yeon Ju;Lee, Yong Hee
    • Journal of the Korean Society of Safety
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    • v.28 no.1
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    • pp.117-124
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    • 2013
  • Emergency operating procedures(EOPs) of nuclear power plants should be described considering the cognitive capability and limitation of operators and provide appropriate information in the aspect of human factors. Procedures which doesn't consider cognitive characteristics of operators can become causes of human errors. In previous researches, in order to reduce these problems related to the description of EOP, an improvement suggestion for EOP writer's guide has been proposed, which is reflected human factors aspects that should be considered when describing EOPs. The proposed items, however, have a necessity to be validated because it was listed from various documents such as standards and guidelines without any special validation process. For that reason, in this study, a validation process were performed to show that procedures, which are described in compliance with the requirement items proposed in the improved EOP writer's guide, have positive effects in the aspects of human errors and performance comparing with previous procedures. Experiments were performed to compare the performances of two tasks which are described in compliance with each writer's guide of before and after the improvement During each task was performed in experiments, changes of physiological responses such as EEG and ECG were measured to evaluate the cognitive workload and the stress of operators in each task. And also, as the performance, frequencies of errors and cognition speeds of each task were evaluated. In the results of the experiment, the portions of the ${\beta}$ wave decreased in the tasks overall after the improvement. In the case of ECG, change rates of the mean of R-R interval were decreased in the tasks after improvement. In the results of the performance, the cognition and the response time of the tasks after the improvement were predominant with statistical significancies. Error times in the tasks after improvement were decreased or same to the tasks before improvement. Conclusively, it was validated that the procedures were described in compliance with the improved EOP writer's guide had effects on the reduction of human errors and improvement of performance.

Control of Bowing in Free-standing GaN Substrate by Using Selective Etching of N-polar Face (N-polar면의 선택적 에칭 방법을 통한 Free-standing GaN 기판의 Bowing 제어)

  • Gim, Jinwon;Son, Hoki;Lim, Tea-Young;Lee, Mijai;Kim, Jin-Ho;Lee, Young Jin;Jeon, Dae-Woo;Hwang, Jonghee;Lee, Hae-Yong;Yoon, Dae-Ho
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.1
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    • pp.30-34
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    • 2016
  • In this paper, we report that selective etching on N-polar face by EC (electro-chemical)-etching effect on the reduction of bowing and strain of FS (free-standing)-GaN substrates. We applied the EC-etching to concave and convex type of FS-GaN substrates. After the EC-etching for FS-GaN, nano porous structure was formed on N-polar face of concave and convex type of FS-GaN. Consequently, the bowing in the convex type of FS-GaN substrate was decreased but the bowing in the concave type of FS-GaN substrate was increased. Furthermore, the FWHM (full width at half maximum) of (1 0 2) reflection for the convex type of FS-GaN was significantly decreased from 601 to 259 arcsec. In the case, we confirmed that the EC-etching method was very effective to reduce the bowing in the convex type of FS-GaN and the compressive stress in N-polar face of convex type of FS-GaN was fully released by Raman measurement.

The Current Methods of Landslide Monitoring Using Observation Sensors for Geologic Property (지질특성 관측용 센서를 이용한 산사태 모니터링 기법 현황)

  • Chae, Byung-Gon;Song, Young-Suk;Choi, Junghae;Kim, Kyeong-Su
    • Journal of Sensor Science and Technology
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    • v.24 no.5
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    • pp.291-298
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    • 2015
  • There are many landslides occurred by typhoons and intense rainfall during the summer seasons in Korea. To predict a landslide triggering it is important to understand mechanisms and potential areas of landslides by the geological approaches. However, recent climate changes make difficult to predict landslide based on only conventional prediction methods. Therefore, the importance of a real-time monitoring of landslide using various sensors is emphasized in recent. Many researchers have studied monitoring techniques of landslides and suggested several monitoring systems which can be applicable to the natural terrain. Most sensors of landslide monitoring measure slope displacement, hydrogeologic properties of soils and rocks, changes of stress in soil and rock fractures, and rainfall amount and intensity. The measured values of each sensor are transmitted to a monitoring server in real-time. The ultimate goal of landslide monitoring is to warn landslide occurrence in advance and to reduce damages induced by landslides. This study introduces the current situation of landslide monitoring techniques in each country.