• 한국치위생학회지
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• 제11권4호
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• pp.453-464
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• 2011

Objectives : The purpose of the study is to gain some basic material for the improvement of dental clinics' homepages through a survey investigation, in which college students of Dental Hygiene Departments and Dental Hygienists in Kwangju and Cheollanamdo Province Methods : It conducted the self-reported questionnaire survey on the Recognition Degrees of the Dental Clinics' Homepages from May 26, 2010 to October 19 targeting 240 dental hygienists who are working for dental offices and 638 college students of Dental Hygiene Departments. Results : 1. It was asked whether they have visited dental homepages for the recent one year; 'yes' answers occupied 68.1%, double than 'no' answers. 2. It was asked how much they know services provided in dental homepages; The more respondents correctly answered that there exist all these services like general information service, visitor's book and bulletin board service, reservation service, dental information service, counseling service, and visual service. 3. All the respondents answered that the homepage of each dental clinic is closely related with the image of the clinic : freshmen showed 3.84, sophomore showed 4.03, juniors showed 4.03, and dental hygienists showed 3.88. 4. It was asked how much they know services provided in dental homepages; Are there the homepages for dental hygienists? Many of them answered that IT experts or businesses are managing the homepages in the technical respect(38.4%) and their use and general administration mainly belongs to dental hygienists(46.2%). Conclusions : It is necessary that through the studies of dental hygienists' interest and understanding on dental homepages we have to seek the development orientation of the technical management and the way of using them, and furthermore we have to know the thoughts of patients on dental homepages, who are users of the dental informations, and find the ways of improving medical services which the patients want.

• 대한금속재료학회지
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• 제50권12호
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• pp.931-937
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• 2012

The microstructure of Cu-15 wt%Ag composites fabricated by equal channel angular pressing (ECAP) with intermediate heat treatment at $320^{\circ}C$ was investigated by transmission electron microscopy (TEM) observations. Ag precipitates with a thickness of 20-40 nm were observed in the eutectic region of the Cu-15 wt%Ag composite solution treated at $700^{\circ}C$ before ECAP. The Cu matrix and Ag precipitates had a cube on cube orientation relationship. ECAPed composites exhibited ultrafine-grained microstructures with the shape and distribution dependent on the processing routes. For route A in which the sample was pressed without rotation between each pass, the Cu and Ag grains were elongated along the shear direction and many micro-twins were observed in elongated Cu grains as well as in Ag filaments. The steps were observed on coherent twin boundaries in Cu grains. For route Bc in which the sample was rotated by 90 degrees after each pass, a subgrain structure with misorientation of 2-4 degree by fragmentation of the large Cu grains were observed. For route C in which the sample was rotated by 180 degrees after each pass, the microstructure was similar to that of the route A sample. However, the thickness of the elongated grains along the shear direction was wider than that of the route A sample and the twin density was lower than the route A sample. It was found that more microtwins were formed in ECAPed Cu-15 wt%Ag than in the drawn sample. Grain boundaries were observed in relatively thick and long Ag filaments in Cu-15 wt%Ag ECAPed by route C, indicating the multi-crystalline nature of Ag filaments.

• 한국정보전자통신기술학회논문지
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• 제16권2호
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• pp.109-115
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• 2023

본 논문은 UV(ultraviolet) 처리된 자기 조립 단분자막(fluorinated self-assembled monolayers; FSAM)을 배향막으로 사용한 액정의 배향 특성을 분석하였다. 물리화학적 분석을 사용하여 UV 처리 전후의 ITO(indium-tin-oxide) 유리 기판의 FSAM 특성을 확인하였다. FSAM 표면은 UV 처리에 의해 소수성에서 친수성으로 변화하였다. LC(liquid crystal) 분자는 UV 처리된 FSAM 표면에서 수평방향으로 정렬되었고 선경사각도 90°에서 0°로 변화하였다. UV 처리된 FSAM을 배향막으로 사용하여 제작된 TN(twist nematic) 셀의 전기광학(electro optics; EO) 특성은 기존의 PI(polyimide) 배향막에 비해 응답 시간이 빠른 것을 확인하였다. 이는 UV 처리된 FSAM 이 LCD(liquid crystal display)의 기존 폴리이미드 배향막을 대체할 잠재적인 가능성을 가진다.

• 한국자기학회지
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• 제2권3호
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• pp.263-267
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• 1992

토크마그네토미터를 이용하여 일축이방성이 있는 자성체의 자화와 인가자장의 방향에 따른 보자력을 정확하게 측정하는 새로운 방법을 개발하였다. 자화와 보자력을 측정하기 위해 시편을 자화용이축 방향으로 포화시킨 후, 자화용이축과 이루는 자장의 각도$({\phi})$ 가 $1/2{\pi}$와 ${\pi}+{\delta}$에서 자장(H)를 증가시켜 가며 자장의 변화에 따른 토크$({\tau})$ 곡선들을 얻었다. 자화는 ${\phi}$가 $1/2{\pi}$인 토크곡선에서 ${\tau}/H$를 측정하여 얻을 수 있었고 보자력은 ${\phi}$가 ${\pi}+{\delta}$인 토크곡선에서 ${\tau}$ = 0 이 되는 자장의 세기로부터 구할 수 있었다. 기존의 VSM에 의한 측정과 비교한 결과 2 % 이내에서 일치함을 보였으며, 토크마그네토미터의 고감도로 인해 VSM에 의한 방법보다 정밀한 자화 측정이 가능하였다.

• KIEAE Journal
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• 제10권3호
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• pp.43-50
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• 2010

Natural lighting is directly connected with our mental and physical health. For working or learning effect, the proper natural lighting is required for improving our living conditions. School facilities, especially, are the place where includes students' ordinary activities with learning behaviors during the school years from elementary to high school. This study was carried out for the purpose introducing a basic database in that planning a school by researching on the actual in the natural lighting system of some schools' classroom, estimating, and analyzing through a simulation, which resulted in a method of improving the natural lighting system. As a result of measuring and analyzing Daylight Factor(DF) during the time from 9 am to 3 pm when students are activating in their classroom, generally DF range of the sides near to window and aisle seats zone are not distributed well. Besides, two out of four school which are researched would not reach the standards of the law for school sanitary while rest of the schools meet the standards; Average DF 5% and Minimum DF 2%. And the result of a simulation by RADIANCE program shows the most appropriate DF range when it is applied in variable numbers about an oriehows the- South-east 15, south-east 30, south-east 45, south-west 15, south-west 30, and south-west 45 degrees. When it is applied in the variable numbers about glass transmittance - 60%, 70%, and 80% in condition facing south of a classroom, the result shows that the DF range of 80% transmittance is relatively higher than other glasses in the classroom. Thus, when a school is built, plans for an orientation is necessary for improve of elementary schools' environment with the glass installation which is made for high transmittance and is regarded with the students' activities time.

• 한국초등과학교육학회지:초등과학교육
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• 제33권3호
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• pp.427-438
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• 2014

In this study, we explored the factors related with preference for and participation in science-related activities of elementary school students. We developed a questionnaire to measure the characteristics of students such as motivation toward science learning, science aspiration, family science orientation, parental educational level and occupation, and the degrees of preference and participation of science-related activities. The questionnaire was administered to about 400 fourth graders in Seoul. The results revealed that the students with higher motivation toward science learning and/or science aspiration preferred and participated more in most activities. It was also found that parental educational level and occupation did not make an appreciable difference in preference and participation. The students who perceived their parents to be science-oriented, however, preferred and participated more in most activities. These results may offer practical implications for effective uses of both school and out-of-school science activities in elementary science education.

• Geomechanics and Engineering
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• 제28권2호
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• pp.117-133
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• 2022

Determination of the mechanical behaviour of jointed rock masses has been a challenge for rock engineers for decades. This problem is more pronounced for non-persistent jointed rock masses due to complicated interaction of rock bridges on the overall behaviour. This paper aims to study the effect of a non-persistent joint set configuration on the mechanical behaviour of rock materials under both uniaxial and biaxial compression tests using a discrete element code. The numerical simulation of biaxial compressive strength of rock masses has been challenging in the past due to shortcomings of bonded particle models in reproducing the failure envelope of rock materials. This problem was resolved in this study by employing the flat-joint contact model. The validity of the numerical model was investigated through a comprehensive comparative study against physical uniaxial and biaxial compression experiments. Good agreement was found between numerical and experimental tests in terms of the recorded peak strength and the failure mode in both loading conditions. Studies on the effect of joint orientation on the failure mode showed that four zones of intact, transition to block rotation, block rotation and transition to intact failure occurs when the joint dip angle varies from 0° to 90°. It was found that the applied confining stress can significantly alter the range of these zones. It was observed that the minimum strength occurs at the joint dip angle of around 45 degrees under different confining stresses. It was also found that the joint orientation can alter the post peak behaviour and the lowest brittleness was observed at the block rotation zone.

• 한국광물학회지
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• 제7권1호
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• pp.62-79
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• 1994

앨바이트 (albite) 와 석영, 그리고 미사장석 (microcline)과 앨바이트의 표준 혼합물 시료를 마련하여 이들에 대해 Rietveld refinement 방법을 사용하여 정량분석 및 결정구조분석을 실시하였다. Rietveld refinement 방법을 이용한 정량분석 결과의 표준편차는 앨바이트와 석영의 표준 혼합물 시료의 분석시에는 4 wt %, 미사장석과 앨바이트의 표준 혼합물 시료의 분석시에는 1 wt %인데 이것은 분리된 피크를 이용하는 기존의 XRD 정량분석법의 결과에 비해 훨씬 향상된 것이다. 또한, 정량분석과 동시에 얻어지는 각 구성광물의 단위포상수값도 정확하게 측정되는 것으로 검증되었다. 앨바이트와 석영의 표준 혼합물처럼 서로 다른 결정입자의 배열 특징을 가진 광물로 구성된 시료의 정량분석 결과에는 실제 무게비와 비교할 때 규칙적인 편이현상이 나타난다. 관찰된 결정입자의 배열현상지수(preferred orientation parameter)와 R-값은 결정입자의 특정방향으로의 배열효과가 미치는 영향이 Rietveld refinement 분석시에 완벽하게 계산될 수 없기 때문에 규칙적인 편이가 발생하는 것임을 지시해 준다. Dollase-March 및 Rietveld-Toraya 함수와 같은 결정입자의 배열현상 보정방법은 정확한 단위포상수 (unit-cell parameter)의 측정에는 도움을 주지만 정량분석결과를 향상시키는 데는 한계가 있는 것으로 보인다. 시료중에서 결정입자의 배열현상을 뚜렷히 보이는 광물의 무게비는 실제값보다 약간 크게 측정되는데, 이러한 현상은 결정입자의 외형 때문에 마운트된 시료표면에서 일어나는 효과에 의한 것으로 판단된다. Rietveld refinement 방법은 분말 X-선 회절도형의 피크들을 분리할 필요없이 회절도형전체를 한꺼번에 분석함으로써 피크의 중첩현상을 극복할 수 있고, 기존의 XRD 정량분석법에 비하여 입자의 배열현상의 문제점을 최소화시킬 수 있다. 또한 refinement된 정확한 단위포상수값이 회절도형의 비례상수와 함께 정량화하는 식에 사용되므로, Rietveld refinement를 이용한 정량분석법은 매우 정확한 광물학적 분석결과를 얻을 수 있는 방법으로 판단된다.

• Transactions on Control, Automation and Systems Engineering
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• 제4권1호
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• pp.9-16
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• 2002

In this paper, we intend to demonstrate a new intuitive force-feedback device for advanced VR applications. Force feed-back for the device is tension based and is characterized by 7 degrees of freedom (DOF); 3 DOF for translation, 3 DOF for rotation, and 1 DOF for grasp). The SPIDAR-G (Space Interface Device for Artificial Reality with Grip) will allow users to interact with virtual objects naturally by manipulating two hemispherical grips located in the center of the device frame. We will show how to connect the strings between each vertex of grip and each extremity of the frame in order to achieve force feedback. In addition, methodologies will be discussed for calculating translation, orientation and grasp using the length of 8 strings connected to the motors and encoders on the frame. The SPIDAR-G exhibits smooth force feedback, minimized inertia, no backlash, scalability and safety. Such features are attributed to strategic string arrangement and control that results in stable haptic rendering. The design and control of the SPIDAR-G will be described in detail and the Space Graphic User Interface system based on the proposed SPIDAR-G system will be demonstrated. Experimental results validate the feasibility of the proposed device and reveal its application to virtual reality.

• 한국정밀공학회지
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• 제29권4호
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• pp.441-448
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• 2012

This paper describes the optimal home positioning algorithm of Eclipse-II, a new conceptual parallel mechanism for motion simulator. Eclipse-II is capable of translation and 360 degrees continuous rotation in all directions. In unexpected situations such as emergency stop, riders have to be resituated as soon as possible through a shortest translational and rotational path because the return paths are not unique in view of inverse kinematic solution. Eclipse-II is man riding. Therefore, the home positioning is directly related to the safety of riders. To ensure a least elapsed time, ZYX Euler angle inverse kinematics is applied to find an optimal home orientation. In addition, the subsequent decrease of maximum acceleration and jerk values is achieved by combining the optimal return path function with cubic spline, which consequently reduces delivery force and vibration to riders.