• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.1
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• pp.94-100
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• 2002

The effects of periodic fuel supply on the nonpremixed flame stability and soot formation were experimentally studied. A solenoid valve was used to control the period of fuel supply. The laser induced incandescence technique was used to visualize cool: volume fraction profile. The flame base shape was changed significantly by the fuel supply period and partially by the fuel flowrates. The portion of bluish flame near the flame base became larger as the period increased. When the period was long, two flames coexisted within one period. It seemed that the characteristic of flame stability were repeated with 4.68m change of fuel supply line length. The soot mass measurements and soot volume fraction measurements revealed that the maximum suppression of soot by the perioic fuel supply was approximately 75% , which occurred when the occurred when the fuel supply period was relatively long.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.418-421
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• 2009

Renewable energy or green energy is a hot issue in theses days. Since wind resource can be endlessly supplied by nature, researchers and common people are interested in study how to use that resource at home or company. Especially, many architects have tried to integrate wind power generator for a part of building. So in this paper, three buildings installed wind power turbine are targed to CFD analysis and these buildings are Bahrain trade center, Discovery tower, and Pearl river tower. Bahrain trade center is the first builidng installed real wind turbine, Discovery tower is constructing at Texas, and Pearl river tower is designed and proved by china researchers. These buildings have very different type of wind power turbine and each turbine has different conditions for best power generation. Therefor this paper will focus on characteristic shape of buildings, wind power turbine type, and expected purpose of construction. Moreover, CFD analysis will show wind flow pattern and wind speed while wind is passing through wind turbine of three tall buildings. CFD analysis for three buildings make comparison the wind flow patterns with experimental result.

• Laser Solutions
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• v.13 no.2
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• pp.1-5
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• 2010

A high speed laser texturing method that relies on laser scanner conditions, to form pattern shapes with micro-narrow surface detail such as dotted line features is demonstrated and analyzed. For example, this method may be used to piston ring and gear part for automotive. Data on friction characteristics of two laser patterns employed for STD61 steel will be shown. Comparison of pattern depths obtained by repetition overlapping process with laser scanner to the results on friction coefficient will be provide. It will be shown that friction characteristic in dotted line patterns can significantly depend upon interaction with the lubrication and laser pattern conditions. Laser pattern processing into a shallow depth provides only slight improvement in friction, while work into a deep shape indicates a significant improvement.

• Tunnel and Underground Space
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• v.8 no.2
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• pp.146-156
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• 1998

Nemerical algorithms were developed to analyze the behavior of the double lining as well as ground mass separately or simultaneously. A lining interface element was especially developed, verified and applied to the study on the coupled interaction of shotcrete and the concrete lining. It could be known fro parameter studys on double lining support systems that as the contact surface between shotcrete and concrete lining was rougher, the more decreased bearing capacity against the cracking of the system. If the thickness of the shotcrete increased, the bearing capacity of the double lining also increased linearly with the thickness. If the thickness of the concrete lining increased, the bearing capacity of the double lining had the relationship of the characteristic S-shape of a sigmoid function with the thickness. When the thickness increased over a given value, it was not useful to increase more the thickness because bearing capacity had no remarkable change. It could be concluded that the behavior of the shotcrete and concrete lining was generally reversed before and after the ratio of horizontal to vertical earth preassure of 1.0 and 0.5 respectively. Therefore, we could guess that the movement which two shotcrete and concrete lining deflect toward each other around the crown caused a friction between two linings and thus this disadvantageous effect could contribute to reducing the bearing capacity against the cracking.

• The Korean Journal of Applied Statistics
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• v.29 no.5
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• pp.823-833
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• 2016

The lifetime is a key characteristic of product quality. It is best to obtain the lifetime data of all samples, but they are often censored due to time or expense limitations. In this paper, we propose a binomial cumulative sum (CUSUM) chart to monitor the mean of type I right-censored Weibull lifetime data, for a xed value of the Weibull shape parameter. We compare the performance of the proposed binomial CUSUM chart with CUSUM charts studied previously using the steady-state average run length (ARL). The results show that the performance of the binomial CUSUM chart is better when the censoring rate is high and/or the sample size is small.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.254-259
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• 2007

Dent resistance is an important characteristic to avoid damage on automotive outer panels. From a practical point of view, dents can be caused in a number of ways. Considering doors as an example, denting can occur from stone impacts or from the careless opening of an adjacently parked vehicle door. Denting can occur where the door surface is smooth and may not have sufficient curvature to resist dent. These exterior body parts are designed to improve dent resistance using a combination of work hardening and bake hardening. In brief, dent is affected by the shape of the parts and the material properties such as yield strength, strain and thickness. In this work, forming of door outer panel is investigated by Taguchi method. Main parameters are yield strength, thickness, blank size, blank holding force and so on. For the given value of design parameters, forming analysis of the eighteen cases are carried out according to L18 orthogonal array. After comparing the performance by simple conversion of simulation results into dent resistance, the final suggestion of the forming parameters is verified for the optimal improvement of dent resistance.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.276-278
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• 2007

Many processes have been introduced to join PE pipes, but most of these methods have lots of disadvantages such as costs and lack of reliability, etc. Recently due to the benefits of cost, safety and reliability, the but welding has been paid much attention to join PE pipes. In case of butt welding, the heat plate which is used to melt PE pipes is the most critical equipment. In this study, after designed secondary developed heat plate of new shape, the PE double wall pipes were but-welding by using the developed heat plate and secondary developed heat plate and comparison of weld-zones and tensile test were performed. As results of tensile test, tensile strengths using secondary developed heat plate were measured higher $1.17{\sim}1.5$ than using developed heat plate.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.1
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• pp.3-9
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• 2009

This paper presents the reduction of acoustic noise generated by electromagnetic force in an induction motor of the electrical forklift. After summarizing the electromagnetic excitation forces due to the interaction between the stator/rotor slot permeance and the stator winding magnetomotive force, the effects of the electromagnetic force on the noise and vibration of an induction motor are analyzed. In order to experimentally identify the noise sources of the motor, the signal analyses for noise and vibration are performed by using waterfall plots of noise and vibration spectrums. It is found that severe noise and vibration are caused by the electromagnetic force when the mode number of the excitation shape for a stator is low. Furthermore, it is verified that the motor noise is amplified if the excitation frequency of the electromagnetic force coincides with one of the natural frequencies of the stator. It is experimentally demonstrated that this severe noise can be considerably reduced by structure modifications. Finally, some design guidelines are suggested to develop an induction motor with a low level of noise.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.2
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• pp.163-170
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• 2015

Recently LED fish-attracting lamps have been more widely used in fisheries as low-cost and high-efficiency fishing gear, and development of long-life high-efficiency lamps is required through the design of LED packages to optimize heat resistance. This study developed an improved LED fish-attracting lamp with excellent heat performance, which was verified using a numerical model. Heat-resistance design factors such as the heat-radiation fin shape, PCB type, and LED chip count were investigated and optimized. Comparison with a commercial 180-W LED fishing lamp showed that the increase in initial temperature was 40% higher than that of the surrounding LED chip because of design errors in contact thermal resistance. The 250-W LED lamp developed in this study has a characteristic with thermal rising in linearly stable according to the heat source. In addition, luminance efficiency was improved by 20-65% by using flow-visualization simulation. A decrease of 45% in total power consumption with a fuel-cost reduction of over 55% can be expected when using these optimized heat release design factors.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.6
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• pp.368-374
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• 2009

Nickel titanium shape memory alloys (NiTi) have been investigated for applications in the biomedical industry. However, little is known about the influences of surface modifications on the propertise of these alloys. The effect of electropolishing and heat treatments was found to exhibit significant surface roughness. Change of phase was B2, r-phase and B19' by heat treatments. In this study, effect of the electropolishing conditions on surface roughness is investigated in Ni-Ti alloys (Nitinol). Variation in phases with heat treatment temperature is investigated for a Ni-Ti alloy by X-ray diffraction and DSC. Characteristic of the microstructure have been observed by SEM. Surface roughness have been measured by AFM. The results clearly show that significant different in surface property to heat treated at $500^{\circ}C$ (R-phase). $TiO_2$ phases preciritated all of the specimens. It is not good effect of surface roughness because made to surface relief. The surface roughness appears to be important in the property of Ni-Ti alloys for biomedical applications.