• 한국정밀공학회지
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• 제28권1호
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• pp.80-88
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• 2011

The dental high-speed air turbine handpiece is one of the most popular devices that have been widely used as the main means of cutting tooth structure and restorative material in dentistry. In consideration of usage and marketability of the dental handpiece, it is obviously worthy of investigating it. The goal of this paper is to establish the relationship between the air turbine speed and the supply route inside the handpiece. To do this, the Computational Fluid Dynamics(CFD) tool, Fine$^{TM}$/Turbo is used and the optimal supply route position is suggested from the simulation results. In addition, as an attempt for domestic product, the reverse engineering process of a high speed dental handpiece by 3D X-Ray CT equipment and wire cutting is presented for the Mark II model in NSK. In doing so, the 3D modeling of the handpiece parts is carried out with CATIA V5, and the interference between parts is examined. Finally, the result of performance test for the prototype produced in this research is presented.

• 한국기계가공학회지
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• 제18권10호
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• pp.99-103
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• 2019

Recently, as the high-precision machinery industry has developed rapidly, peripheral equipment has been developed to improve machining efficiency. Peripheral equipment for machining includes cooling units, housings, oil separators, and much more. Oil, such as cleaning and cutting fluids, is used for machining. When waste oil is reused, the contamination of the workpieces and reduction in machining accuracy are generated by the waste oil, including sludge. Therefore, the development of an oil separator is necessary for efficiently separating oil, water, and sludge. The purpose of this study is to analyze the oil separation efficiency and flow characteristics of a high-speed centrifugal separator according to the rotation velocity and diffusion plate. The oil separation efficiency and flow characteristics were analyzed using hydrodynamic theory and computational fluid dynamics (CFD). The results of this study will be used as basic data for the development of a high-speed centrifugal separator.

• 한국정밀공학회지
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• 제32권5호
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• pp.431-439
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• 2015

One of common challenges in designing modern production machines is realizing high speed motion without sacrificing accuracy. To address this challenge it is necessary to maximize the stiffness of the mechanical structure and the control system with consideration on the main disturbance input, cutting forces. This paper presents analysis technologies for realizing high stiffness in production machines. First, CAE analysis techniques to evaluate the dynamic stiffness of a machine structure and a new method to construct the physical machine model for servo controller simulations are demonstrated. Second, cutting forces generated in milling processes are analyzed to evaluate their effects on the mechatronics system. In the effort to investigate the interaction among the structure, controller, and process, a flexible multi-body dynamics simulation method is implemented on a magnetic bearing stage as an example. The presented technologies can provide better understandings on the mechatronics system and help realizing high stiffness production machines.

• 한국운동역학회지
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• 제19권2호
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• pp.369-377
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• 2009

The purpose of this study was to determine the relationship between different soccer cleat designs and knee joint moments. Twelve physically active males (mean(SD): age: 26.4(6.2)yrs; height: 176.4(4.1)cm; mass: 74.0 (7.4)kg) were recruited Kinematic and force plate data were collected for all subjects during normal running and a $45^{\circ}$ cutting maneuver, called a v-cut. Both motions were performed at $4.0{\pm}0.2\;m/s$ on infilled artificial turf with three pairs of soccer cleats of different sole plate designs, and one pair of neutral running shoes. Inverse dynamics were used to calculate three dimensional knee joint moments, with repeated measures ANOVA and post hoc paired Student's t-test used to determine significance between shoe conditions. Significant differences were found in the extension moments of the knee for running trials, and for external rotation and adduction moments in the v-cutting trials. Knee moments were greater in v-cut than running, and the traditional soccer cleats (Copa Mondial and World Cup) tended to result in greater knee moments than the Nova runner or TRX soccer cleat. Cleat design was found to influence 3-dimensional knee moments in a v-cut maneuver. In the translational traction test, there were significant differences between all conditions. In the rotational traction test, friction with soccer shoes were greater than friction with running shoes. However, no differences were found between soccer shoes. Higher moments may lead to increased loads and stresses on knee joint structures, and thus, greater injury rates.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.49-52
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• 1996

The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surfice. However, as the accuracy requirement gets tighter and desired surface contours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining processprohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normalto the face of the workpice can be filterd through an appropriate admittance transfer function to result in the estimated depth of cut. This can be compared to the desired depth of cut to generate the adjustment cotnrol action in addition to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. Based on the empirical data of the cutting dynamics, simulation results are shown.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.190-196
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• 2014

Exhaust system by reinforcement of environment regulation came to the foe study necessity. And Exhaust system has necessary to increase the engine performance and silence. From this cause, Automobile has significantly considered production expense. this study makes process for checking the characteristics about Exhaust variable valve within muffler. Variable valve might reduce the baffle within muffler, It was possible to remove the front muffler. Therefor, To miniaturize a size of muffler might be increased by performance through cost-cutting effect and controling of back pressure. Because the Study on Variable valve installed within muffler, to measure the real data was hardly resulted one of the assignments. From manufactured conduct device, might measure data one of piece which was up-graded of problem. Considering to these point, stressed pressure distribution has analyzed on cross section, floating characteristics about velocity distribution around variable valve using analysis as computational fluid dynamics of Ansys with completed measurement data.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.417-423
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• 2005

Contractor's opportunistic bidding behavior refers to contractor's deliberate low-bid, which cannot accord with the cost, and expectation for beyond-contractual reward (BCR), the compensation earned through cutting corners or claims after undertaking the construction project. This research applies System Dynamics to develop a model of contractor's pricing with consideration for dimensions of "cost", "market competition", and "BCR". Iterative computer simulations were performed to analyze the effects of contractor's pricing on the market price. The results were then examined by statistical analysis on data collected from 44 highway projects in Taiwan. It is found that the critical force driving the contractors to bid opportunistically is their excessive expectations in BCR under the current environment. Within the price competition mechanism, if the problem of BCR exists, even if the bidding system is further improved, contractors would still prefer opportunistic bidding behavior, and eventually make the whole construction industry operate ineffectively. Therefore, it is crucial to remedy the aforementioned BCR problem by more effective management policy.

• 복식
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• 제52권7호
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• pp.103-121
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• 2002

This study intended to analyze the transition of design of Korean soccer player's uniform according to development of the society and changes in formative elements, and examine features inside them by considering designs of soccer player's uniform by ages ranging from the introduction of soccer up to now. Results of the study are summed up below. First, as a result of analyzing designs of soccer player's uniforms from 1920 to 2002 Korea-Japan WorldCup based on formative elements of the style of dress. \circled1 it is shown that basic shape has been kept but changes in only color. cutting, trimming, logo and symbol have existed. \circled2 Colors of the uniforms have been different according to ages but red, blue and white colors have been used most and sometimes black was employed. so it is known that colors in the Korean national emblem have been all used. \circled3 In the beginning of the uniform there was a limitation in its design due to absence of functional materials but now highly-sensitive textile products and highly-functional textile materials guaranteeing optimal condition and highest activity of a soccer player have been utilized in various ways. \circled4 It is known that symbols modelling the image of Korea have been used in diverse ways but effected much by directions toward images pursued by designers of sponsors. Second, the meanings represented by designs of the uniforms are classified into a degree of symbolizing Korea, tradition, superiority and dynamics. That is to say, \circled1as colors and symbols coming from the emblem have been used in the uniforms. they have symbolized one nation and possessed the meaning representing even Korean national spirit. \circled2As traditional colouring and symbols have been used in the uniforms, they have shown the Korean sense of a beauty. \circled3 Colors, tones and designs overwhelming the mood of play have been used in the uniforms, so that they have played a role in making players of other team flinch mentally and making Korean players gain an advantage over them. \circled4 Thanks to strong symbols or comparative effects of colors. they have shown the dynamics representing power and energy.

• 대기
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• 제33권2호
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• pp.125-154
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• 2023

Since the Korean Meteorological Society was organized in 1963, the climate dynamics fields have been made remarkable progress. Here, we documented the academic developments in the area of climate dynamics performed by members of Korean Meteorological Society, based on studies that have been published mainly in the Journal of Korean Meteorological Society, Atmosphere, and Asia-Pacific Journal of Atmospheric Sciences. In these journals, the fundamental principles of typical ocean-atmosphere climatic phenomena such as El Niño, Madden-Julian Oscillation, Pacific Decadal Oscillation, and Atlantic Multi-decadal Oscillation, their modeling, prediction, and its impact, are being conducted by members of Korean Meteorological Society. Recently, research has been expanded to almost all climatic factors including cryosphere and biosphere, as well as areas from a global perspective, not limited to one region. In addition, research using an artificial intelligence (AI), which can be called a cutting-edge field, has been actively conducted. In this paper, topics including intra-seasonal and Madden-Julian Oscillations, East Asian summer monsoon, El Niño-Southern Oscillation, mid-latitude and polar climate variations and some paleo climate and ecosystem studies, of which driving mechanism, modeling, prediction, and global impact, are particularly documented.

• 한국기계가공학회지
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• 제14권6호
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• pp.1-6
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• 2015

Tool condition monitoring plays one of the most important roles in the improvement of both machining quality and productivity. In this regard, various process signals and monitoring methods have been developed. However, most of the existing studies used cutting force or acoustic emission signals, which posed risks of interference with the machining system in dynamics, fixturing, and machining configuration. In this study, a feed motor current signal is used as a process signal representing process and tool states in tool breakage monitoring based on an adaptive autoregressive model and unsupervised neural network. From the experimental results using various cases of tool breakage, it is shown that the developed system can successfully detect tool breakage before two revolutions of the spindle after tool breakage.