• Progress in Medical Physics
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• v.27 no.4
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• pp.272-276
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• 2016

To investigate the optimum x-ray tube design for the dental radiology, factors affecting x-ray beam characteristics such as tungsten target thickness and anode angle were evaluated. Another goal of the study was to addresses the anode heel effect and off-axis spectra for different target angles. MCNPX has been utilized to simulate the diagnostic x-ray tube with the aim of predicting optimum target angle and angular distribution of x-ray intensity around the x-ray target. For simulation of x-ray spectra, MCNPX was run in photon and electron using default values for PHYS:P and PHYS:E cards to enable full electron and photon transport. The x-ray tube consists of an evacuated 1 mm alumina envelope containing a tungsten anode embedded in a copper part. The envelope is encased in lead shield with an opening window. MCNPX simulations were run for x-ray tube potentials of 70 kV. A monoenergetic electron source at the distance of 2 cm from the anode surface was considered. The electron beam diameter was 0.3 mm striking on the focal spot. In this work, the optimum thickness of tungsten target was $3{\mu}m$ for the 70 kV electron potential. To determine the angle with the highest photon intensity per initial electron striking on the target, the x-ray intensity per initial electron was calculated for different tungsten target angles. The optimum anode angle based only on x-ray beam flatness was 35 degree. It should be mentioned that there is a considerable trade-off between anode angle which determines the focal spot size and geometric penumbra. The optimized thickness of a target material was calculated to maximize the x-ray intensity produced from a tungsten target materials for a 70 keV electron energy. Our results also showed that the anode angle has an influencing effect on heel effect and beam intensity across the beam.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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• pp.117-123
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• 2001

In present study a methodology has been developed and applied for the optimum design and performance evaluation of microchannel heat sinks. The optimum design parameters include channel number and fin thickness. For a trial model of 127mm in length, 52.5mm in width, 16mm in height and 2.5mm in base thickness, the optimum channel number and the fin thinckness have been determined to be of 194 and 0.08359mm, respectively in laminar flow region. Performance of the optimally designed microchannel heat sinks has been compared with those having 50% and 150% of the number of channels. The results showed that the 50% and 150% designs increased the pumping power by 200% and 150%, respectively.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.32-37
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• 2011

In car refinishing, the paint film characteristics of clear coat play an important role in appearance quality. Thus, Primarily in this research, the variance of brightness with the change of the thickness of paint film is investigated. Besides, as changing the thickness of paint film, the correlation between surface leveling(which is one of appearance characteristics) is investigated in this research. Throughout this investigation, we come to know that the increase of clear coat paint film thickness leads the improvement of appearance characteristics within specific range of thickness. Furthermore, the fact that too thick paint film does not increase the brightness or appearance characteristic any more is known. The optimum thickness of clear coat film for the best and appearance characteristics is derived from this research and more efficient way of determining optimum thickness of paint film is found. Particularly, haze value and waviness have more influence on vividness than brightness. Throughout all experiments, the appearance characteristics are much better at painted horizontally than vertically. These results are derived due to the facts that to obtain the same paint film thickness at painted vertically with painted horizontally is difficult and the way of vertical painting is different from horizontal painting. Therefore, the improvement of vertical painting and horizontal painting are required.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.2
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• pp.26-30
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• 2016

This paper presented an optimum design of a perpendicular PMDSLSM (Permanent Magnet Double-sided Linear Synchronous Motor) to minimize the detent force. As an optimum method, the response surface method was used and 3D finite element method for the calculation. The design variables of the machine were the primary core width and thickness, and magnet width, thickness and length. Object functions were to minimize the detent force and maximize the thrust of the basic model. The results showed that the thrust force of the optimum design increased from 82.1N to 90.2N and detent force decreased from 15.2N to 2.8N, respectively, compared to the basic model.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.59-66
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• 2000

To investigate the optimum brazing condition, variation of bonded structure and mechanical properties of novel brazed pure Al with bonding condition (brazing temperature, time and Si/flux ratio) was studied. A basic study of the bonding mechanism was also examined. The optimum brazing condition was obtained at $590^{\circ}$ for 2 minutes and the bonded structure showed that it is composed of almost entirely eutectic Al-Si with near eutectic composition. At higher brazing temperature $630^{\circ}$, hypoeutectic Al-Si structure was observed in the bonded area and resulted in erosion of base metal. The thickness of eutectic layer formed in optimum brazing temperature increased linearly with the square root of time, showing a general diffusion controlled process. The ultimate tensile strength of bonded joint brazed at an optimum brazing condition was about 60% of base metal and its fracture surface showed a brittle mode.

• Tribology and Lubricants
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• v.10 no.4
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• pp.33-42
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• 1994

An influence of inlet pressure on the performance of sector-shaped pad thrust bearings is investigated theoretically. The optimum conditions of film thickness or the optimum positions of pivot are found through the evaluation of load capacity for all available conditions of film thickness, under the operating conditions which the thermal and pad deformation effects can be neglected. The bearing performance including the inlet pressure effects is obtained for a wide operating ranges that inertia parameter(Re$^{*}$) is up to unity, and for the various cases of pad extent angle (number of pad) and the three cases of the angle between pads. The results show that the inlet pressure has a large influence on the performance of sector-shaped pad thrust bearings. In the design of sector-shaped pad bearings, due to the inlet pressure, the optimum number of pad is varied with the operating speed and the angle between pads, and the optimum position of pivot is located toward the leading edge along with the operating speed increases.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.111-118
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• 1995

A method of determining an optimum blank shape for the non circular deep drawing process is more investigated and applied to the balnk design for multi-stage deep drawn product. The forming procedure of two-stage deep drawing process is looked over and the method of determining a blank shape is proposed. In experimental research, a optimum blank and a optional rectangular blank were considered and we measured thickness strain distributions. We could predict a strain distribution and compare with a experimental strain distribution. Also, the strain distributions for the blank shapes, optimum and rectangular, were compared.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.634-639
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• 2001

In this paper, we discuss optimum process conditions of Hemispherical Grained Silicon formation for high density DRAM'S capacitor. In optimum process renditions, the phosphorous concentration, storage polysilicon deposition temperature and thickness of hemispherical grain silicon are in the range of 3.0-4.0E19atoms/㎤, 53$0^{\circ}C$ and 40(equation omitted), respectively. in the 64M bit DRAM capacitor using optimum process conditions, limit thickness of nitride is about 65(equation omitted). The results obtained in this study are applicable to process control and HSG-Si formation for high reliability and high density DRAM's capacitor.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1068-1071
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• 2004

We report the techniques to obtain the high uniformity of the phosphor film thickness in the cold cathode fluorescent lamps, which are widely used as a back-light for the liquid crystal display. The thickness variation of the phosphor layer was sensitive to blowing conditions. The optimum conditions were obtained at flow rate of 15 sccm for 30 min at 40 $^{\circ}C$. The optimum and uniform thickness of a phosphor layer gives good luminous output.

• Journal of the Korean Society of Safety
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• v.9 no.1
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• pp.68-75
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• 1994

The cetylpyridium ion-selective electrode were developed by dibenzo-18-crown-6 for auto control of the chemical plants. The effect of content of active material and the membrane thickness on the response characteristics of electrode such as the linear reponse range, the detection limit, and Nemstian slope of the electrod, were studied. The electrode characteristics was better with decreasing the content of active material above the optimum content, but became worse below these. DBP was best as a plasticizer, The effect of the membrane thickness on the electrode characteristics was improved with decreasing the membrane thickness, but below the optimum membrane thickness the electrode exhibited an inverse trend.