• 대한방사선기술학회지:방사선기술과학
• /
• 제46권3호
• /
• pp.219-229
• /
• 2023

In this study, basic characteristics such as reproducibility, linearity, and directionality of RPL glass dosimeters were evaluated to improve the reliability of dose evaluation through RPL glass dosimeters, and uncertainty elements such as sensitivity by glass element and magazine slot sensitivity were evaluated. Using a mathematical model to calibrate the measured values of the RPL glass dosimeter, the measurement uncertainty was calculated assuming an example. As a result of the characteristic evaluation, the RPL glass dosimeter showed excellent performance with a standard deviation of ±1% (1 SD) for the reproducibility of the reading process, a coefficient of determination for linearity of 0.99997. And the read-out of the RPL glass dosimeter are affected by the circular rotation direction of the glass dosimeter during irradiation, fading according to the period after irradiation, the number of laser pulses of the reader, and response degradation due to repeated reading, it is judged that measurement uncertainty can be reduced by irradiation and reading in consideration of these factors. In addition, it was confirmed that the dose should be determined by calculating the correction factors for the sensitivity of each element and, the sensitivity of each reading magazine slot. It is believed that the reliability of dosimetry using glass dosimeters can be improved by using a mathematical model for correction of glass dosimeter readings and calculating measurement uncertainty.

• Composites Research
• /
• 제33권6호
• /
• pp.360-364
• /
• 2020

차량의 경량화를 위해 기존의 스틸로 제작된 카울크로스멤버를 마그네슘, 플라스틱으로 연구개발이 진행되었으나, 차량 장착상태의 성능적인 문제로 적용이 어려운 실정이다. 최근 부품양산에 가장 적합한 경량화 부품으로 복합소재 인서트 사출 카울크로스멤버에 대한 연구를 진행하고 있다. 이는 알루미늄 바에 복합소재 브라켓 부품을 인서트 사출하는 제조 공정으로 차량의 장착 상태를 고려할 때, 두 부품의 체결상태가 중요한 요소 중에 하나이다. 본 연구에서는, PA6-GF60 복합소재에 알루미늄 바를 인서트 사출하기 위한 연구로 알루미늄 바의 접합강도가 중요한 요소 중에 하나이다. 이를 위한 연구방법으로 알루미늄 바에 접착제를 분사하는 방식과 널링처리를 한 경우에 대해, 카울크로스멤버의 알루미늄 바와 복합재료 사출부품 형상간의 부분 파트별로 횡방향과 회전방향에 대한 접합강도를 분석 연구하였다.

• 한국주조공학회지
• /
• 제12권3호
• /
• pp.220-229
• /
• 1992

The degree of purification and the macrostructure of high purity aluminium were studied through the alternate stirring method in order to improve the nonuniformity of solute concentration in the unidirectional stirring method. The $2^3$ factorial design was done to examine the effects of experimental factors more qualitatively. In the relatively low stirring speed of 1500 rpm with alternate stirring mode, the uniform solute profile and refined grain structure were obtained due to strong washing effect and turbulent fluid flow. It was induced by the transition of the momentum boundary layer by alternation of the stirrer. It was concluded from this study that the alternate stirring mode was more effective to obtain the uniformity of solute even in the stirring speed of 1500 rpm. But the degree of purification decreased below the critical alternating period. When 2N(99.8wt.%) aluminium was used as the starting material the morphology of solid-liquid showed the cellular shape and the columnar grains were inclined to the direction of rotation. This inclined grain growth resulted from the difference of relative velocities of solid and liquid. The inclined angle was increased as the stirring speed increased and solidification proceeded. In the case of 4N aluminium, there was no inclined grain growth and it was confirmed from the macrostructure and SEM work that the morphology of solid-liquid interface was planar. From the factorial design, it was found that the alternate stirring mode showed poorer purification effect than that of unidirectional stirring mode at low speed(500 rpm). In addition, the factor that had the most significant effect on the degree of purification was the stirring speed.

• International Journal of Fluid Machinery and Systems
• /
• 제6권4호
• /
• pp.200-205
• /
• 2013

In order to investigate the characteristics of unsteady flow in a mixed flow pump guide vane under the small flow conditions, several indicator points in a mixed flow pump guide vane was set, the three-dimensional unsteady turbulence numerical value of the mixed flow pump which is in the whole flow field will be calculated by means of the large eddy simulation (LES), sub-grid scale model and sliding mesh technology. The experimental results suggest that the large eddy simulation can estimate the positive slope characteristic of head & capacity curve. And the calculation results show that the pressure fluctuation coefficients of the middle section in guide vane inlet will decrease firstly and then increase. In guide vane outlet, the pressure fluctuation coefficients of section will be approximately axially symmetrical distribution. The pressure fluctuation minimum of section in guide vane inlet is above the middle location of the guide vane suction surface, and the pressure fluctuation minimum of section in which located the middle and outlet of guide vane. When it is under the small flow operating condition, the eddy scale of guide vane is larger, and the pressure fluctuation of the channel in guide vane being cyclical fluctuations obviously which leads to the area of eddy expanding to the whole channel from the suction side. The middle of the guide vane suction surface of the minimum amplitude pressure fluctuation to which the vortex core of eddy scale whose direction of fluid's rotation is the same to impeller in the guide vane adhere.

• Earthquakes and Structures
• /
• 제14권5호
• /
• pp.467-476
• /
• 2018

The seismic vulnerability of skewed bridges had been observed in many past earthquakes. Researchers have found that the in-plane rotation of the girders was one of the main reasons for the vulnerability of these types of bridges. To date, not many experimental works have been done on this topic, especially those including pounding between adjacent structures. In this study, shake table tests were performed on a bridge-abutment system consisting of a straight, $30^{\circ}$, and $45^{\circ}$ bridge with and without considering pounding. Skewed bridges with the same fundamental frequency and those having the same girder mass as the straight bridge were studied. Under the loadings considered, skewed bridges with the same frequency as the straight tend to have smaller responses than those with the same mass. The average maximum bending moment developed in the piers of the $30^{\circ}$ bridge with the same mass as that of the straight when pounding was not considered was 1.6 times larger than when the frequencies were the same. It was also found that the NZTA recommendations for the seat lengths of skewed bridges could severely underestimate the relative displacements of these types of bridges in the transverse direction, especially when pounding occurs. In the worst case, the average transverse displacement of the $45^{\circ}$ bridge was about 2.6 times the longitudinal displacement of the straight, which was greatly over the limit suggested by the NZTA of 1.25 times.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2005년도 ICCAS
• /
• pp.631-637
• /
• 2005

This paper presents a stiffness analysis method for a low-DOF parallel manipulator, which takes into account of elastic deformations of joints and links. A low-DOF parallel manipulator is defined as a spatial parallel manipulator which has less than six degrees of freedom. Differently from the case of a 6-DOF parallel manipulator, the serial chains in a low-DOF parallel manipulator are subject to constraint forces as well as actuation forces. The reaction forces due to actuations and constraints in each limb can be determined by making use of the theory of reciprocal screws. It is shown that the stiffness model of an F-DOF parallel manipulator consists of F springs related to the reciprocal screws of actuations and 6-F springs related to the reciprocal screws of constraints, which connect the moving platform to the fixed base in parallel. The $6{times}6$ stiffness matrix is derived, which is the sum of the stiffness matrices of actuations and constraints. The six spring constants can be precisely determined by modeling the compliance of joints and links in a serial chain as follows; the link can be considered as an Euler beam and the stiffness matrix of rotational or prismatic joint can be modeled as a $6{times}6$ diagonal matrix, where one diagonal element about the rotation axis or along the sliding direction is zero. By summing the elastic deformations in joints and links, the compliance matrix of a serial chain is obtained. Finally, applying the reciprocal screws to the compliance matrix of a serial chain, the compliance values of springs can be determined. As an example of explaining the procedure, the stiffness of the Tricept parallel manipulator has been analyzed.

• 폴리머
• /
• 제35권4호
• /
• pp.350-355
• /
• 2011

고분자의 주사슬에 광반응을 할 수 있는 phenyldiacryloyl 그룹을 가지고, 곁사슬에 액정분자와 비슷한 메조겐인 biphenyl을 에테르 결합을 통해서 도입된 가용성 광반응성 폴리아미드를 합성하였다. 합성된 폴리아미드 고분자는 0.65 dL/g의 대수점도를 가지며, 일반적인 코팅 방법으로 여러 기질의 표면에 잘 도포되는 성질을 보였다. 광반응성 폴리아미드 고분자의 화학 구조는 $^1H$ NMR과 Fourier transform infrared(FTIR) spectroscopy를 이용해서 확인하였다. 합성된 고분자의 유리전이온도는 $150^{\circ}C$까지 관측되지 않았으며, 열분해 온도는 $280^{\circ}C$로 관측되어, 열안정성이 높음을 확인하였다. 합성된 폴리아미드 고분자 박막을 비편광된 자외선을 노광시켜 노광하는 에너지에 따른 변화를 조사했을 때, 좋은 광반응성을 보였다. 광반응성 폴리아미드를 이용하여 선편광된 자외선을 노광하여 제작한 액정 셀 내에서, 액정분자들은 노광된 선편광 자외선의 electric vector 방향의 수직으로 배향되는 것이 관측되었으며, 이러한 현상은 선편광 자외선의 노광량에는 무관함을 보였다. 액정 셀 내에서 액정분자들의 pretilt angle은 선편광된 자외선의 노광량에 따라 약간의 차이를 보이며 $0.2^{\circ}$에서 $0.5^{\circ}$사이의 값을 보였다.

• 제어로봇시스템학회논문지
• /
• 제13권4호
• /
• pp.320-328
• /
• 2007

This paper presents a stiffness modeling of a low-DOF parallel robot, which takes into account of elastic deformations of joints and links, A low-DOF parallel robot is defined as a spatial parallel robot which has less than six degrees of freedom. Differently from serial chains in a full 6-DOF parallel robot, some of those in a low-DOF parallel robot may be subject to constraint forces as well as actuation forces. The reaction forces due to actuations and constraints in each serial chain can be determined by making use of the theory of reciprocal screws. It is shown that the stiffness of an F-DOF parallel robot can be modeled such that the moving platform is supported by 6 springs related to the reciprocal screws of actuations (F) and constraints (6-F). A general $6{\times}6$ stiffness matrix is derived, which is the sum of the stiffness matrices of actuations and constraints, The compliance of each spring can be precisely determined by modeling the compliance of joints and links in a serial chain as follows; a link is modeled as an Euler beam and the compliance matrix of rotational or prismatic joint is modeled as a $6{\times}6$ diagonal matrix, where one diagonal element about the rotation axis or along the sliding direction is infinite. By summing joint and link compliance matrices with respect to a reference frame and applying unit reciprocal screw to the resulting compliance matrix of a serial chain, the compliance of a spring is determined by the resulting infinitesimal displacement. In order to illustrate this methodology, the stiffness of a Tricept parallel robot has been analyzed. Finally, a numerical example of the optimal design to maximize stiffness in a specified box-shape workspace is presented.

• 대한소아치과학회지
• /
• 제32권2호
• /
• pp.224-228
• /
• 2005

유치의 치수 감염을 적절히 치료하지 않으면 영구 계승치의 저형성이나 저석회화 같은 법랑질 형성부전, 치배의 위치변화, 맹출 부진이나 맹출 정지 같은 많은 합병증을 초래할 수 있다. 이 중에서도 계승 영구치배의 위치변화는 선행 유치의 변성된 치수로 인한 위치변화가 가장 많다. 본 증례는 조선대학교 치과병원 소아치과에 내원한 환아 중 유전치의 치근단 병소로 인해 계승영구전치 치배의 위치변화가 초래된 것으로 사료되어 유치 치료의 중요성을 문헌고찰과 함께 보고하는 바이다.

• 한국기계가공학회지
• /
• 제10권3호
• /
• pp.1-6
• /
• 2011

This study focused on the localization of swivel type tube couplers, which all depend on imports. In this study, a computer application analysis was performed using a finite element method as a preliminary study. In the major developments related to the objective of this study, the air brake system produced by car makers represents a different in the installation point of an air tank according to the type of cars or in the length and direction of its hoses and that leads to cause lots of problems. For solving such problems, the design of the major elements in a swivel type tube coupler was analyzed using a finite element method, and its validity was also verified. In the process that verifies the validity of this study, it was necessary to investigate how much external force affects the desorption of the tube support, which is the most important element in swivel type tube couplers. For achieving the investigation, a pressure test was implemented for the tube support according to the Federal Motor Vehicle Safety Standards(FMVSS). In the results of the pressure test, all samples satisfied the FMVSS. In addition, several tests were implemented by installing the sample of the developed swivel type tube coupler to an actual vehicle. In particular, rotation tests with various angles were applied by welding the swivel type coupler to an air tank through an argon welding process. In the results of the installing test for an actual vehicle, it was verified that the designed structure was determined as a structure that is able to endure the eccentric torque and deformation pressure applied to several directions that are the major problems in such fixed type tube couplers. Therefore, in the comparison of the performance of the developed product with the product of PARKER, it was possible to verify that the localized swivel type tube coupler developed in this study shows more excellent than that of the existing products by PARKER.