• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1272-1275
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• 2007

The HDD (hard disk drive) using Load/Unload (L/UL) technology includes the benefits which are increased areal density, reduced power consumption and improved shock resistance than those of contact-start-stop (CSS). Dynamic L/UL has been widely used in portable hard disk drive and will become the key technology for developing the small form factor hard disk drive. Main design objectives of the L/UL mechanisms are no slider-disk contact or no media damage even with contact during L/UL, and a smooth and short load and unload process. In this paper, we focus on state matrix, pitch static attitude (PSA), roll static attitude (RSA), loading/unloading contour (LC/ULC), impact force and contact. Stability of slider is mainly determined by PSA and RSA. State matrix by PSA and RSA is also important indicator. Therefore we analyze state matrix of SFF HDD suspension through the LC/ULC.

• 로봇학회논문지
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• 제15권1호
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• pp.39-47
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• 2020

This paper presents a control and operation system for a remotely operated vehicle (ROV). The ROV used in the study was equipped with a manipulator and is being developed for underwater exploration and autonomous underwater working. Precision position and attitude control ability is essential for underwater operation using a manipulator. For propulsion, the ROV is equipped with eight thrusters, the number of those are more than six degrees-of-freedom. Four of them are in charge of surge, sway, and yaw motion, and the other four are responsible for heave, roll, and pitch motion. Therefore, it is more efficient to integrate the management of the thrusters rather than control them individually. In this paper, a thrust allocation method for thruster management is presented, and the design of a feedback controller using sensor data is described. The software for the ROV operation consists of a robot operating system that can efficiently process data between multiple hardware platforms. Through experimental analysis, the validity of the control system performance was verified.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.276-279
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• 2000

When high temperature superconducting tapes is fabricated using the PIT (Powder In Tube) method, the length of HTS tapes is increased more than 500 ${\sim}$ 1,000 times of initial powder packed billet. On mechanical processing, heterogeneous properties between the ceramic superconducting core and Ag/Ag alloy sheath occur the non-uniformity deformation as like sausaging that deteriorate the critical current properties of HTS tapes. In this study, we investigated the workability of Bi-2223/Ag/Ag alloy sheath tapes fabricated by the PIT method involving a number of different mechanical processes, multi drawing and rolling. In order to obtain the high critical current density and high uniformity of Bi-2223/Ag sheath tapes, the influences of powder packing density, drawing die angle and rolling parameters were studied. We found that the roll diameter is an important variable in the rolling process, as critical current of tapes rolled using 250 mm rolls was higher than that using 150 mm rolls.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.379-387
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• 2004

A novel flatness sensing system which is called the Flatness Sensing Inter-stand Looper(FlatSIL) system is suggested and a self-tuning PI control system using the FlatSIL is designed for improving the flatness of hot strip in finishing mill processes. The FlatSIL system measures the tension along the direction of the strip width by using segmented rolls, and the tension profile is approximated through the tension of each segmented roll. The flatness control system is operated by using the tension profile. The proposed flatness control system as far as the tension profile-measuring device works for the full strip length during the strip rolling in finishing mills. The generalized minimum variance self-tuning (GMV S-T) PI control method is applied to control the flatness of hot strip which has a design parameter as weighting factor for updating the PI gains. Optimizing the design parameter in the GMV S-T PI controller, the Robbins-Monro algorithm is used. It is shown by the computer simulation and experiment that the proposed GMV S-T PI flatness control system has better performance than the fixed PI flatness control system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.437-438
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• 2006

Generally, the vertical roll process is used to achieve extensive width reduction in hot strip mill. However, it is difficult to avoid the defects such as dog-bone and seam-defect. The sizing press has been developed in response to the defects mentioned above. Especially, this study is carried out to investigate the deformation of slab by two-step sizing press. The deformation behavior in the width sizing process is more favorable than that in conventional vertical rolling edger. The objective of this study is to determine the optimal anvil shape parameters in the sizing press with two-step die from the viewpoint of edge-seam length. In general, the edge-seam defect occurs parallel to the rolling direction at both edges in horizontal rolling process after sizing press. The optimal combination of the parameters is determined by FE-simulation and Artificial Neural Network (ANN). The slab deformation in sizing press with convex anvil is analyzed by FE-simulation. The most suitable profile of the anvil is also discussed fur the improvement of trimming loss because of the side seam defect by FE-simulation and ANN.

• 한국입자에어로졸학회지
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• 제9권4호
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• pp.261-269
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• 2013

The chemical mechanical polishing (CMP) process is widely used in semiconductor manufacturing process for planarization of various materials and structures. Point-of-use (POU) filters are used in most of the CMP processes in order to reduce the unwanted micro-scratches which may result in defects. The performance of the POU filter is depends on type and size of the abrasives used during cleaning process. For this reason, there is a need to evaluate POU filters for their filtration efficiency (FE) with different types of abrasives. In this study, we developed filter test system to evaluate the FE of POU using ceria and silica abrasives (slurry). The POU filter is roll type capsule filter with retention size of 0.2 ${\mu}m$. Two POU filters of different make are evaluated for FE. We observed that both POU filters show similar filtration efficiency for silica and ceria slurry. Results reveal that the ceria slurry and the colloidal silica particle are removed not only by mechanical way but also hydrodynamic and electrostatic interaction way.

• 한국주조공학회지
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• 제20권2호
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• pp.122-128
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• 2000

Strip casting process is a new technology that makes a near net shape thin strip directly from molten metal. With this process, a large amount of energy and casting cost could be decreased from the abbreviation of reheating and/or hot rolling process. Ductile cast iron which has spheroidal graphite in the matrix is the most commercial and industrial material, because of its supreme strength, toughness, and wear resistance etc. But it cannot be produced to the thin strip owing to difficulty in rolling of ductile cast iron. In this study, ductile cast iron strips are produced by the twin roll strip caster, with different chemical compositions of C, Si, and Mn contents. And then heat-treated, microstructures and mechanical properties are examined. The microstructures of as-cast strip are that of white cast iron which consists of the mixture of cementite and pearlite, but the equiaxed crystal zone of the pearlite or segregation zone of cementite exists in the center region of the strip thickness, which cannot be observed in the rapidly solidified metallic mold cast specimens. This structure is supposed to be formed from the thermal distribution of strip and the rolling force. Comparing with the structures of each strips after heat treatment, increasing Si content makes smaller spheroidal graphite and more compact in the matrix, furthermore the less of Mn content makes the ferrite matrix be obtained clearer and easier. As a result of the tensile test of graphitization heat-treated strips, the yield strengths are about 250 MPa, the tensile strengths are about $430{\sim}500$ MPa, and the elongations are about $10{\sim}13%$. In the case of the strip which has the smaller and more compact spheroidal graphite in the ferrite matrix, the higher tensile strength and better drawability could be obtained.

• 대한조선학회논문집
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• 제39권2호
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• pp.69-80
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• 2002

선박의 곡외판은 냉간가공과 열간가공(선상가열) 과정을 거쳐 제작된다. 선상가열의 자동화 및 기계화에 대한 연구가 다양하게 수행되어 오고 있다. 특히 가열조건과 잔류 변형 사이의 관계규명은 자동화 및 기계화를 위한 주요 요소로 생각된다. 본 연구는 그러한 관계를 규명하기 위하여 일련의 체계적인 과정을 제시하고 관계식을 제안하였다. 선상가열에 의한 변형은 3차원 열탄소성 변형현상으로 정식화될 수 있으며, 열탄소성 변형현상을 유한요소해석을 이용하여 다양한 가열조건에 대한 수치해석을 수행하였다. 유한요소법의 유용성을 검증하기 위하여 실험을 수행하였고 그 유용성을 확인하였다 변형관계식에 사용된 입력변수는 차원해석을 통하여 선정하였다. 유한요소법을 이용하여 얻어진 결과를 활용하여 선상가열에 의한 변형관계식을 추정하기 위하여 다변수해석과 다차원 보관과정을 예시하였다. 일련의 과정을 통하여 본 연구는 선상가열의 가열조건과 잔류 변형 사이의 관계식을 선정하기 위한 방법을 제안하였다.

• Journal of the Korean Institute of Landscape Architecture International Edition
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• 제1호
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• pp.167-175
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• 2001

After World War II, Japan experienced a great political and social shift, which brought a concern of emerging public landscape in urban development. This paper analyses the management of the aesthetic intentions in urban design effort. We reviewed the development of various public installation of artworks concerning urban landscape aesthetics through its administrative process in chronological order. The monuments during the first decade marked a shift in emphasis from the militarism of the pre-war and wartime period to one of peace. However, some of the monuments and sculptures are not immune to controversy. This became an issue that could no be ignored by public officials whose responsibility was to place the sculptures while maintaining sensitivity to public opinion. As public administrators began to consider the possibility that sculptures may contribute to improving public amenities, the contextual concepts were basically ignored. Some of the programs in 1970s began to show more respect to the context, while other programs in this period expressed more interest in educational aspects of sculptures in the public spaces. Urban development projects also seek to introduce artworks integrated to their urban design concepts in 1990s. Generally, the administrators responsible for these programs were rarely trained in any relative field study other than public administration. Installing sculptures tended to be considered as part of public works projects on the level of urban planning and construction. The general public is basically removed from participating in the critical decisions that actually impact their lives in relation to the artworks. In conclusion, public art in japan has unique social and historic background both in its advantages and disadvantages. Issues pertaining to art in public spaces have evolved over the decades as the term "sculpture pollution" began to appear by the mid 1990s. most of the problems originated in either the lack of monumentality, contextual consideration, quality, or public participation. From another point of view, these programs played great roll in the development of modern Japanese sculpture and patronizing process, and the creation of new urban landscape with aesthetic value. In this sense, they must be considered as successful and noteworthy examples of cultural administration and urban design policy.

• 드라이브 ㆍ 컨트롤
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• 제15권3호
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• pp.21-28
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• 2018

We propose a tension controller based on a time-delay estimation (TDE) technique for a winding machine. Firstly, we perform the necessary calculations to derive a mathematical model of the winding machine. In this sense, it is revealed that the roll radius of the winding machine is characteristically seen to be increasing or decreasing during the winding process. That being said, it is noted that the parameters of the winding machine are coupled and constantly changing during this process. Understandably then, it is noted that the model is shown to be nonlinear and time-varying. Secondly, we propose the way to apply the TDE based controller which is the so-called Time-delay Control (TDC). The TDC utilizes the time-delayed information intentionally to compensate the nonlinear and time-varying characteristics. As we have seen, the proposed controller consists of two parts: one is a TDE component, and the other is an error dynamics component which is defined by a user. In a computer simulation based on the Matlab/Simulink program, the proposed controller is compared with a conventional PID controller, which is widely used in the tension control of the winding machine. The proposed controller reduces the incidence of overshoot and steady-state error in the tension control, as compared to the conventional PID controller.