• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.993-1001
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• 2006

In this paper, a method of accurate position control using a pneumatic cylinder driving apparatus is presented. To overcome the effect of friction force and transmission line, low friction type cylinder applied externally pressurized air bearing structure is used and two control valves attached both side of the cylinder directly. To compensate nonlinear characteristics of control valves, linearized control input derived from the relation between control input and effective area of control valve, and dither signal are applied to the valve. The controller applied to the pneumatic cylinder driving apparatus is composed of a state feedback controller and a disturbance observer. Experimental results show that the effectiveness of the proposed method and position control error of $5{\mu}m$ accuracy could be obtained easily.

• 한국태양에너지학회 논문집
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• 제34권4호
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• pp.39-44
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• 2014

The elemental composition of electro-deposited black Cr solar selective coatings before and after heating in air by using secondary ion mass spectrometry (SIMS) was investigated for optical property analysis. In addition, black Cr selective coating exposed by solar radiation for 5 months was compared with heated sample. SIMS investigation shows that $OH^+$ bearing ions were related to a near surface region of CrOH and CrO compound. The optical degradation of this coating after heating at $500^{\circ}C$ reveals that diffusion of the Cu and Ni elements in substrate material, the chemical interactions adjacent to the interface, and the interface width broadening.

• Journal of Mechanical Science and Technology
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• 제15권3호
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• pp.281-290
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• 2001

Particle contamination has been an ongoing problem affecting the reliability of the magnetic hard disk drives. Especially the recent use of MR head requires much tighter control of particle contamination due to thermal asperity (TA) phenomenon. In this study, the effects of slider air bearing surface design of TA reduction capability were investigated by manufacturing two types of sliders. Numerical methods were used to simulate the motion of particles in the head/media interface. Experiments were conducted to verify the results predicted by the numerical simulation. Drives were built and exposed to particle contamination using a particle injection chamber, which turned out to be a very simple and reliable particle generation method over conventional aerosol technique. Then the number of TA generated in the drives was recorded and compared. Also the contacts between slider and particles were investigated by acoustic emission study. It was found that a new ABS design, which has aerodynamic U-shaped rail and central flow passage, was beneficial in reducing the particle contamination on the slider.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.37-44
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• 2004

This paper presents an approach to optimally design the air bearing surface (ABS) of the head slider by using the approximation methods. The reduced basis concept is used to reduce the number of design variables. In the numerical calculation, the progressive quadratic response surface modeling (PQRSM) is used to handle the non-smooth and discontinuous cost function. A multi-criteria optimization problem is formulated to enhance the flying performances over the entire recording band during the steady state and track seek operations. The optimal solutions of the sliders, whose target flying heights are 12 nm and 9 nm, are automatically obtained. The flying heights during the steady state operation become closer to the target values and the flying height variations during the track seek operation are smaller than those for the initial one. The pitch and roll angles are also kept within suitable ranges over the recording band.

• 한국생산제조학회지
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• 제25권6호
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• pp.452-457
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• 2016

Single screw compressors are widely used in the fields of air/gas compression, refrigeration, and chemical fluid transportation systems. A single-screw compressor is composed of a screw rotor and two gate rotors located at both sides. This simple construction enables low rotational speed of the rotor, efficient compression with low noise, low vibration, and long bearing life. Despite these merits, the design method of single-screw compressors is not well known. To accelerate the industrial application of single-screw compressors, a design method using coordinate transformation is presented in this paper, and a tool trajectory is established for machining. Finally, the screw rotor, which is machined using the proposed method, is presented.

• 오토저널
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• 제10권3호
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• pp.31-37
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• 1988

A phase different method to evaluate the instrument error of roundness measuring instrument and the form error of specimens for the calibration of the instrument is used. An instrument with a rotary table supported by an air bearing was calibrated by using the standard balls as a standard. The calibration was carried out repeatedly by setting the same ball in 12 phase angles(per 30.deg.) on the table and by recording their roundness errors with a magnification of 100,000 times. As a result of data analysis of all the observations, readout at each of 144 orientations(per 2.5.deg.) from recorded data file, the error of performance of the instrument and the specimens are separated. In the particular instrument used in the present experiment, the error of the instrument was determined with the accuracy of 0.0164 (.mu.m) and the form error of the specimens was determined with the accuracy of 0.0264,0.0172(.mu.m), respectively. If the instrument was calibrated by using the above specimens, then the accuracy of the measurement of roundness error can be improved to about 0.017 (.mu.m).

• 한국가축번식학회지
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• 제10권1호
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• pp.42-48
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• 1986

These experiments were carried out to develop new techniques identifying XX-bearing embryos prior to implantation by immunological method. Antiserum to histocompatibility-Y(H-Y) antigen was prepared in adult SD(sprague-dawley) female rat by repeated immunization of newbone testis supernatant from males of the same strain. ELISA test was used to identify the H-Y antibody of antiserum. Total 124 mouse embryos (8-cell stage) were treated with H-Y antiserum and complement in BSA free Ho, pp. and Pitt's medium and cultured under the gas phase of 5% CO2 in air at 37$^{\circ}C$ for 24 to 48 hrs. The morphological characteristics of embryos treated were observed under the phase-contrast micro scope. The results obtained in these experiments were summarized as follows: 1. Optimal Density of H-Y antibody were a, pp.ared to be 0.27-0.47 by ELISA test. 2. Of total 124 embryos treated with H-Y antiserum and complement 69(55.6%) embryos developed to blastocyst and 55(44.4%) destroyed or arrested.

• 한국가축번식학회지
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• 제10권1호
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• pp.36-41
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• 1986

These experiments were carried out to obtain basic information necessary for sexing embryos by chromosomal analysis. To observe metaphase chromosomes, all embryos developed to blastocysts were cultured in Ho, pp. & Pitts' medium containing 0.001% Colcemid under the gas phase of 5% CO2 in air at 37$^{\circ}C$ for 2 hours. The sex chromosome of mouse embryos shown normal development after culture in medium containing H-Y antiserum (10%, v/v) and complement (20%, v/v) also was confimed by chromosomal analysis. The results obtained in these experiments were summarized as follows: 1. Among 89 mouse blastocysts, the number of embryos identified to have XX and XY chromosome was 22(25%) and 25(28%), respectively and 42(47%) embryos were not identified. 2. Of total 40 mouse balstocysts cultured in medium containing H-Y antiserum and complement, 23(58%) embryos which were able to be discriminated their sex chromosomes were identified to be XX bearing embryos. 3. Sex chromosomes of a number of embryos subjected to chromosomal analysis were not identified. This result may be due to absence or poor quality of metaphase spreads.

• 한국정밀공학회지
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• 제31권6호
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• pp.491-495
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• 2014

We developed a compact high-precision slot-die coating machine for thin-film deposition on a flexible substrate. For smooth and precise coating, air-bearing and linear motor system were employed to minimize velocity ripple. The gap control mechanism is specially designed to have repeatability of gap between nozzle and substrate under 1 ${\mu}m$. Due to extremely precise gap control, the machine can coat thin-films down to 50 nm with $200mm{\times}100mm$ size. A thin film of Ag nano-particle ink is coated for demonstration.

• International Journal of Aeronautical and Space Sciences
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• 제3권1호
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• pp.50-60
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• 2002

A new co-evolutionary algorithm, of which the convergence speed is accelerated by neural networks, is proposed and verified in this paper. To reduce computational load required for co-evolutionary optimization processes, the cost function and constraint information is stored in the neural networks, and the extra offspring group, whose cost is computed by the neural networks, is generated. It increases the offspring population size without overloading computational effort; therefore, the convergence speed is accelerated. The proposed algorithm is applied to attitude control design of flexible satellites, and it is verified by computer simulations and experiments using a torque-free air bearing system.