• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1297-1300
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• 2008

A conventional linear accelerator system requires a flat-topped pulse with less than ${\pm}$ 0.5% ripple to meet the beam energy spread requirements and to improve pulse efficiency of RF systems. A pulse transformer is one of main determinants on the output pulse voltage shape. The pulse transformer was investigated and analyzed with the pulse response characteristics using a simplified equivalent circuit model. The damping factor ${\sigma}$ must be >0.86 to limit the overshoot to less than 0.5% during the flat-top phase. The low leakage inductance and distributed capacitance are often limiting factors to obtain a fast rise time. These parameters are largely controlled by the physical geometry and winding configuration of the transformer. A rise time can be improved by reducing the number of turns, but it produces larger pulse droop and requires a larger core size. By tradeoffs among these parameters, the high-voltage pulse transformer with a pulse width of 10 ${\mu}s$, a rise time of 0.84 ${\mu}s$, and a pulse droop of 2.9% has been designed and fabricated to drive a klystron which has an output voltage of 284 kV, 30-MW peak and 60-kW average RF output power. This paper describes design optimization of a high-voltage pulse transformer for high-power pulsed applications. The experimental results were analyzed and compared with the design. The design and optimal tuning parameter of the system was identified using the model simulation.

• Geomechanics and Engineering
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• v.22 no.4
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• pp.319-328
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• 2020

This paper investigates the effect of the width of failure and tension crack (TC) on the stability of cohesive-frictional soil slopes in three dimensions. Working analytically, the slip surface and the tension crack are considered to have spheroid and cylindrical shape respectively, although the case of tension crack having planar, vertical surface is also discussed; the latter was found to return higher safety factor values. Because at the initiation of a purely rotational slide along a spheroid surface no shear forces develop inside the failure mass, the rigid body concept is conveniently used; in this respect, the validity of the rigid body concept is discussed, whilst it is supported by comparison examples. Stability tables are given for fully drained and fully saturated slopes without TC, with non-filled TC as well as with fully-filled TC. Among the main findings is that, the width of failure corresponding to the minimum safety factor value is not always infinite, but it is affected by the triggering factor for failure (e.g., water acting as pore pressures and/or as hydrostatic force in the TC). More specifically, it was found that, when a slope is near its limit equilibrium and under the influence of a triggering factor, the minimum safety factor value corresponds to a near spherical failure mechanism, even if the triggering factor (e.g., pore-water pressures) acts uniformly along the third dimension. Moreover, it was found that, the effect of tension crack is much greater when the stability of slopes is studied in three dimensions; indeed, safety factor values comparable to the 2D case are obtained.

• Advances in Computational Design
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• v.3 no.3
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• pp.269-288
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• 2018

180 different 2D numerical analyses have been carried out to estimate the factor of safety (FOS) for rooted slopes. Four different types of vegetated coverage and a variety of slope geometry considering three types of soil have been evaluated in this study. The highly influenced parameters on the slope's FOS are determined. They have been chosen as the input parameters for developing a new practical relationship to estimate the FOS with an emphasis on the roots effects. The dependency of sliding mode and shape considering the soil and roots-type has been evaluated by using the numerical finite element model. It is observed that the inclination and height of the slope and the coverage type are the most important effective factors in FOS. While the soil strength parameters and its physical properties would be considered as the second major group that affects the FOS. Achieved results from the developed relationship have shown the acceptable estimation for the roots slope. The extracted R square from the proposed relationship considering nonlinear estimation has been achieved up to 0.85. As a further cross check, the achieved R square from a multi-layer neural network has also been observed to be around 0.92. The numerical verification considering different scenarios has been done in the current evaluation.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.2 s.40
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• pp.67-75
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• 2007

There are a number of risks in constructing tunnel-structures. Therefore, the precise and rapid observation about inside deformation of the tunnel is required to prevent these risks from occurring and to secure safety. But currently, the real situation is that the crown settlement, cavity deformation and ground surface settlement rely upon the universal mensuration which uses total station or various kinds of measuring instruments. Recently, according to improvement and progress of measuring technology, three-dimensional laser scanning is used as the method to provide data for maintaining structures. It solves the reliability problem of measuring method for the transformational volume of existing structures, provides data that enables to judge visually by three-dimensioning the shape change of structures and makes it possible to deliberate speedy countermeasure. And it can also be efficiently used in the structure maintenance and field measurement.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.1-6
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• 2010

This study presents the practical design modification to improve the retracting performance of the pyro-typed high power pretensioner. 3 components of the pretensioner are redesigned and the usefulness of the design modification is verified by the experiment. During the pretensioning process, the gas blast generated from the gunpowder is transferred to the rack-pinion gear through the manifold. The rack-pinion gear is connected with the spool where the webbing is rolled up. According to the rotation of the pinion, the spool is turned and the webbing is winded. To help the gas blast flow well, the shape of the inner cross section of the manifold is changed. The spur gear design program is developed and used to find the best combination of the rack-pinion gear pair to increase the power transmission efficiency. The pinion guide is installed on the spool to prevent the vibration of the pinion. As a result of the experiment, the amount of the web retraction length is increased when every single design modification is applied. Therefore, the retracting performance of the pretensioner is considered to be improved if the presented design modifications are applied.

• Transactions of Materials Processing
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• v.29 no.5
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• pp.257-264
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• 2020

This paper is concerned with the influence of the plastic property of the rivet on the numerical prediction of the Self-Piercing Rivet (SPR) Joining. In order to predict the plastic property of the rivet, a ring compression specimen was directly fabricated from the rivet used for the mechanical joining of dissimilar materials, and the FE analysis together with the ring compression test was iteratively carried out by changing the plastic property of the rivet. For reliable FE analysis, a friction coefficient was estimated based on a friction calibration curve, measuring the reductions in inner diameter and height of the ring specimen after the compression test. From each simulation result, the force-displacement curves were then compared from each other so as to obtain the rivet plastic property that shows good agreement with the experimental result. The SPR joining between GA590 1.0t and Al5052 2.0t was conducted, and the numerical prediction was performed with the use of the plastic property evaluated based on the inverse analysis and the one referred from Mori et al. [11]. Comparison of the experiment and the numerical predictions in terms of the interlock and bottom thickness revealed that the reliable evaluation of the plastic property of the rivet is necessary for the trustworthy numerical prediction of the SPR joining.

• Korean journal of food and cookery science
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• v.21 no.4 s.88
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• pp.514-527
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• 2005

The purposes of this study were firstly to optimize the recipe for iced cookies by cooking with five different ingredient levels of $Jinuni\;bean(X_1),\;butter(X_2)\;&\;sugar(X_3)$ and secondly to analyze the chemical and sensory test results by using RSM(Response Surface Methodology). As a result of this test, water activity decreased with increasing contents of butter or sugar, while hydrophilic browning decreased independently with increasing sugar content. There was a positive correlation(p<.001) between specific gravity and hardness, although the result was not uniform due to the interaction of each factor. There was a negative correlation(p<.001) between the spread ratio and gravity or hardness, and it tended to increase with increasing each content. Color value L and color value a had positive correlation (p<.001) and the value tended to decrease with increasing the quantity of Jinuni bean. Generally, the strength of the cookies showed a saddle point at the peak of the 3d graph. As a result of sensory evaluation, the color was sensitive to the contents of sugar and Jinuni bean, the texture was sensitive to the contents of butter and sugar, and the taste and overall quality were sensitive to all three factors. Color had a positive correlation(p<.05) with the taste, texture and overall quality. There were high positive correlations(p<.001) between the taste, texture and overall quality. The preference data showed an up-swollen, parabolic shape in the center of the 34 graph, which enabled the optimum value to be determined and the optimum mixture ratio which fulfilled all sensory items was Jinuni bean 93g, butter 188.5g and sugar 155g, indicating a substitution of flour by $44\%$.

• Parasites, Hosts and Diseases
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• v.27 no.3
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• pp.213-216
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• 1989

Seven cases of Diphyllcbothrium latum infection were proved by collection of worms after prasiquantel treatment between October, 1986 and July, 1987. The patients were all males aged 20~44 years residing in Seoul or Ulungdo, Kyungpook Province. All of them had the history of eating several kinds of raw marine fishes, and they had never been to abroad. One of them exporienced abdominal pain and 6 experienced natural discharge of a chain of worm segments, but none revealed any sign of anemia, Total 12 worms (1~3/patient) were collected after praiiquantel treatment. The worms were 85~423 cm in length, and revealed the characteristic rosette-shape uterus in their gravid proglottides. The average egg size varied $61.0~65.3{\times}41.7~46.1{\;}{\mu\textrm{m}}$. The eggs were yellowish. brown, and ovoid to elliptical. Including the present 7 cases, the total number of human D. latum infections proven by worms in Korea becomes 28 cases.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.1
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• pp.99-106
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• 2013

DME (Di-Methyl Ether) is synthetic product that is produced through dehydration of methanol or a direct synthesis from syngas. And it is able to save fossil fuel and reduce pollutants of emission such as PM and $CO_2$. In spite of its advantages it is difficult to design DME fuelled engine system because DME fuel may cause to severely generate cavitation and corrosion in fuel delivery system due to physical properties of DME. Therefore, in this study three-dimensional internal flow characteristics with consideration of cavitation were predicted in the DME injector using diesel and DME fuel. Moving grid technique was employed to describe needle motion and 1-D hydraulic simulation of injector was also simulated to obtain transient needle motion profiles. The results of simulation show that cavitations was generated at the inlet of nozzle near high velocity region both diesel and DME. And mass flow rate of DME is reduced by 4.73% compared to that of diesel at maximum valve lift because cavitation region of DME is much more larger. To increase flow rate of DME injector, internal flow simulation has been conducted to investigate the nozzle hole inner R-cut effect. The flow rates of diesel and DME increase as R-cut increases, and flow coefficient of DME fuel injector was increased by 6.3% on average compared with diesel fuelled injector. Finally, optimum shape of DME injector nozzle is suggested through the comparison of flow coefficient with variation of nozzle hole inner R-cut.

• Journal of the Korean Society of Food Culture
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• v.20 no.5
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• pp.516-524
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• 2005

This study was conducted to develop a functional cookie with the addition of a sweet pumpkin powder on a cookie shape, that showed high preference level to all age group and that was very easily to store because of low moisture content, by substituting partially a sweet pumpkin powder for reducing content of wheat flour. This study has produced the sensory optimal composite recipe by making iced cookies, respectively, with each 5 level of Sweet pumpkin powder($X_{1}$), sugar($X_{2}$), butter($X_{3}$), by C.C.D(Central Composite Design) and conducting sensory evaluation and instrumental analysis by means of RSM(Response Surface Methodology). Sensory items showed very significant values in color, appearance, flavor, overall quality(p<0.05), texture(p<0.01), and instrumental analysis showed significant values in lightness, redness(p<0.01), yellowness, spread ratio, hardness(p<0.05). Also sensory optimal ratio of Sweet pumpkin cookie was calculated as sweet pumpkin powder 81.8g, sugar 116.6g, butter 210.7g, and it was revealed that the factors of influencing cookie aptitude were in order of Sweet pumpkin powder, butter, sugar.