• Transactions on Electrical and Electronic Materials
• /
• 제18권4호
• /
• pp.207-210
• /
• 2017

The suspension arrangement of insulators provides flexibility and assists in power transmission in transmission lines. The performance of the insulator string is strongly influenced by the environmental conditions to which it is exposed, its shape and the inherent material properties of suspension-type insulators. The suspension-type insulators are mostly made from glass, porcelain and ceramic material due to their high resistivity. Irregularity in charge distribution throughout the porcelain insulator may lead to accelerated aging and electrical breakdown. A very high and steep lightning impulse voltage may also cause breakdown of suspension-type insulators. We investigated various material characteristics such as alumina addition, surface morphology, x-ray diffraction pattern and relative density of suspension porcelain insulators manufactured in 1989 (36,000 lbs.), 1995 (36,000 lbs.) and 2001 (36,000 lbs.) by the KRI Company for use in 154 kV high power transmission lines. We compared the material characteristics of these porcelain insulators with that of the top-of-the-line porcelain insulators (36,000 lbs.) manufactured by the NGK Company in 2000. These suspension-type porcelain insulators were exposed to arc and flashover tests to examine their electrical and mechanical strength. It was noted that alumina addition (17 wt.%) for K-2001 was one of the major contributors to the enhancement of the performance of the porcelain insulators and to their ability to withstand very high current generation during the arc test. The porcelain insulators manufactured during 2001 also showed the highest relative density of 95.8% as compared to the other insulators manufactured in 1989 and 1995 respectively 94.2% and 91.5%. We also discuss reports of various failure modes of suspension-type porcelain insulators.

• Korea-Australia Rheology Journal
• /
• 제12권1호
• /
• pp.55-67
• /
• 2000

In this paper, an experimental study of the rheological behavior of granular flow in a new type of storage silo is presented. The main characteristic of the new design is a hexagonal shape chosen with the objective of minimizing the stresses applied to the stored grains, and to reduce grain damage during the filling and emptying processes. Measurements of stress distribution and flow patterns are shown for a variety of granular materials. Because of the design of the silo, the granular material adopts its natural rest angle at all times eliminating collisional stresses and impacts between grains. A homogeneous, low friction flow is naturally achieved which provides a controlled stress distribution throughout the silo during filling and emptying. Secondary dynamic stresses, which are responsible for wall failure in conventional silos of the vertical type, are completely eliminated. A comparison between the two geometries is presented with data obtained for these silos and a number of granular materials. The discharge pattern inhibits powder formation in the silo and the filling system virtually eliminates unwanted material packing. Finally, notwithstanding the rheological advantages of this new design, the hexagonal cells that constitute the silo have many other advantages, such as the possible use of solar energy to control the humidity inside them. The cell type design allows for versatile storage capabilities and the elevation above the ground provides unlimited transportation facilities during emptying.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 추계학술대회 논문집
• /
• pp.589-592
• /
• 2005

Micro-forming is a suited technology to manufacture very small metallic parts(several $mm{\sim}{\mu}m$). Micro-forming of $Zr_{62}Cu_{17}Ni_{13}Al_8$ bulk metallic glass(BMG) as a candidate material for this developing process are feasible at a relatively low stress in the supercooled liquid state without any crystallization during hot deformation. In this study, micro-formability of a representative bulk metallic glass, $Zr_{62}Cu_{17}Ni_{13}Al_8$, was investigated for micro-forging of U-shape pattern. Micro-formability was estimated by comparing $R_f$ values $(=A_f/A_g)$, where Ag is cross-sectional area of U groove, and $A_f$ the filled area by material. Microforging process was simulated and analyzed by applying finite element method. FEM simulation results should reasonable agreement with the experimental results when the material properties and simulation conditions such as top die speed, remeshing criteria and boundary conditions tightly controlled. The micro-formability of $Zr_{62}Cu_{17}Ni_{13}Al_8$ was increased with increasing load and time in the temperature range of the supercooled liquid state. Also, FEM Simulation using DEFORM was confirmed to be applicable for the micro-forming process simulation.

• Journal of the korean society of oceanography
• /
• 제32권4호
• /
• pp.181-190
• /
• 1997

A large subtidal sand ridge (Jungang Satoe) in Asan Bay, on the west coast of Korea, was studied in order to understand the morphology and sediment transport trend in a macrotidal setting, by means of analyzing sediment samples, current data, side-scan sonographs and seismic profiles. The ridge is about 15 km long and 2-5 km wide, with a relief of about 15 m. It is elongated in the flow direction of flood (SE) and ebb (NW) tidal currents, but asymmetrical in cross section. The western and southwestern side of the ridge is characterized by relatively gentle slopes averaging 0.4$^{\circ}$, whereas on the northeastern side, relatively steep slopes were mapped with 1.6$^{\circ}$ slope angles. Tidal currents associated with the ridge are very strong; maximum surface velo-cities range from neap values of 50 cm/s to spring values of 130 cm/s. The shear velocities during flood and ebb are strong enough to erode and transport sands on the ridge. Sand waves and megaripples (dunes) are the most common bedforms produced by the tidal currents, which show regional differences in shape and size on the ridge. The distribution pattern of these bedforms in-dicates that the flood tidal currents are dominant on the offshore (northwest) side of the ridge, whereas the onsho.e (southeast) side of the ridge is ebb-dominated. The sand transport path as inferred from bedform orientations is directed toward the ridge crest on the flanks, whereas on the crest, it is near-longitudinal to the ridge axis. The convergent, upslope movement of sands on the ridge flanks appears to be important in sand ridge building and maintenance. A significant ridge migration toward the northeast can be suspected on the basis of the ridge morphology, which may cause offshore hazards for navigation.

• 패션비즈니스
• /
• 제12권3호
• /
• pp.99-115
• /
• 2008

International exchange gets active in nations with the increase of Internet use and heading toward digital age. Thus the communication conveying image of nations effectively plays an important role in an international society. Sports events are regarded as important international exchange events and good opportunities for public relations of one's own country and taken as tools of planting good images in other nations. This study surveyed the concept and history of uniform through the documents and previous studies in order to find the aesthetic characteristics of sportswear uniform applying the image of national ensign and investigates the origin and start time in Korea of selected 6 sports items. As a result of finding the expression way of ensign image and drawing the aesthetic characteristics by analyzing the use and variation of ensign colors, the use of colors other than ensign and reflection of ensign form in collected 60 sports uniforms, this study could draw the symbolical beauty, beauty of variation and beauty of brevity. First, symbolical beauty is the aesthetic characteristics expressing uniforms by using the pattern ensign symbolizes and ensign colors themselves or enlarging a part of ensign. Second, beauty of variation is the aesthetic characteristics creating geometrical new patterns in uniform through the distortion and exaggeration of ensign shape, or transforming the colors themselves of ensign. Third, beauty of brevity is the aesthetic characteristics using other colors only as decorative factor while applying the main colors of ensign to the most part of uniform, or unifying the uniforms with only one color of ensign. As a result of survey, the proportion of the symbolical beauty was highest in summer season and beauty of brevity and beauty of variation followed and the proportion of beauty of variation was highest and the symbolical beauty and beauty of brevity followed after that in winter season. This study found the way of expressing image of one's own country in sports uniform through this article, expecting the exact recognition on sports uniform and the diversity of sports uniform design in which the images of the nation are expressed more variously.

• 한국식품과학회지
• /
• 제32권2호
• /
• pp.258-264
• /
• 2000

8품종 변이체 쌀로부터 전분을 분리하여 몇몇 이화학적 특성을 비교하였다. 일반품종 및 저아밀로오스 변이체 쌀 전분입자의 형태는 다변형인데 비해서 shr 및 분질미 전분입자의 형태는 구형을 나타내고 있었다. 남풍 CB243의 호화개시온도 및 호화종료온도가 특히 높았으며, 분질미 및 남풍 EM90의 호화엔탈피가 다른 품종들에 비해서 높았다. 15% $H_2SO_4$에 대한 가수분해도는 shr.이 가장 높았으며, 남풍 CB243이 가장 낮았다. X선 회절도는 8품종 모두 전형적인 A형이었다. 저아밀로오스 유전자가 도입된 품종일수록 glucoamylase에 의한 효소 가수분해도는 증가하고 있었다.

• 패션비즈니스
• /
• 제19권2호
• /
• pp.85-102
• /
• 2015

This study aimed to develop dress torso patterns with both aesthetic and functional qualities that fit for women in their 20s. In order to develop dress torso patterns, wearing tests were done. By collecting drafting methods of the patterns through literature study and the survey of wedding dress manufacturers, four kinds of dress torso patterns were selected. The existing dress torso patterns have no or very small ease in chest, waist, and hip circumferences. As a result of wearing tests of these four existing dress torso patterns, drafting methods of dress torso patterns that have the best satisfied values close to optimum zero were selected; the first and second research dress torso patterns were developed by modifying and supplementing items that had noticeable difference through the Wilcoxon rank sum test with a selected measured value and a best satisfied value of zero; and deduced a drafting method for the final developed dress torso patterns by a wearing test of the second developed dress torso patterns. Distinctive aspects of drafting methods of the final developed dress torso patterns were that ease for each area was given differently by considering a functional quality and a chest circumference instead of a bust circumference was applied to reduce influence by the size of breast in neck and armhole areas, and a back bust level. Back neck breadth was made wider and front neck breadth was made less narrow due to a recent change of age 20s female adults' shoulder and back shape.

• 방사선산업학회지
• /
• 제8권3호
• /
• pp.141-146
• /
• 2014

Nickel (Ni) electroplating was implemented by using a metal Ni powder in order to establish a $^{63}Ni$ plating condition on the PN junction semiconductor needed for production of beta-voltaic battery. PN junction semiconductors with a Ni seed layer of 500 and $1000{\AA}$ were coated with Ni at current density from 10 to $50mA\;cm^{-2}$. The surface roughness and average grain size of Ni deposits were investigated by XRD and SEM techniques. The roughness of Ni deposit was increased as the current density was increased, and decreased as the thickness of Ni seed layer was increased. The results showed that the optimum surface shape was obtained at a current density of $10mA\;cm^{-2}$ in seed layer with thickness of $500{\AA}$, $20mA\;cm^{-2}$ of $1000{\AA}$. Also, pure Ni deposit was well coated on a PN junction semiconductor without any oxide forms. Using the line width of (111) in XRD peak, the average grain size of the Ni thick firm was measured. The results showed that the average grain size was increased as the thickness of seed layer was increased.

• Wind and Structures
• /
• 제17권3호
• /
• pp.317-343
• /
• 2013

When evaluating flutter instability, it is often assumed that incident wind is normal to the longitudinal axis of a bridge and the flutter critical wind speed estimated from this direction is most unfavorable. However, the results obtained in this study via oblique sectional model tests of four typical types of bridge decks show that the lowest flutter critical wind speeds often occur in the yaw wind cases. The four types of bridge decks tested include a flat single-box deck, a flat ${\Pi}$-shaped thin-wall deck, a flat twin side-girder deck, and a truss-stiffened deck with and without a narrow central gap. The yaw wind effect could reduce the critical wind speed by about 6%, 2%, 8%, 7%, respectively, for the above four types of decks within a wind inclination angle range between $-3^{\circ}$ and $3^{\circ}$, and the yaw wind angles corresponding to the minimal critical wind speeds are between $4^{\circ}$ and $15^{\circ}$. It was also found that the flutter critical wind speed varies in an undulate manner with the increase of yaw angle, and the variation pattern is largely dependent on both deck shape and wind inclination angle. Therefore, the cosine rule based on the mean wind decomposition is generally inapplicable to the estimation of flutter critical wind speed of long-span bridges under skew winds. The unfavorable effect of yaw wind on the flutter instability of long-span bridges should be taken into consideration seriously in the future practice, especially for supper-long span bridges in strong wind regions.

• 식물분류학회지
• /
• 제39권2호
• /
• pp.89-99
• /
• 2009

한국산 꿩의다리속 식물의 계통 및 유연관계를 밝히기 위해 39개의 형태 형질을 바탕으로 Maximum parsimony와 Neighbor-joining을 분석하였다. 식물재료는 한국 고유종을 포함해 내군 21분류군과 외군 1분류군이 사용되었다. 좀꿩의다리절과 금꿩의다리절은 각각 100% 부트츠랩 값과 83% 부트츠랩 값으로 단계통군을 형성하였고, 금꿩의다리절은 좀꿩의다리절의 자매군으로 나타났다. 꽃꿩의다리절과 산꿩의다리절은 측계통군을 형성하였다. 그늘꿩의다리를 제외한 산꿩의다리절은 방사상분지로 나타났다. 꿩의다리절과 발톱꿩의다리절은 각각 독립적인 분계군를 형성하였다. 꿩의다리속 식물에서 주요한 형질인 수술의 모양은 곤봉형이 가장 원시적이며, 원시적인 곤봉형에서 봉형, 그리고 실형으로 파생되는 것으로 나타났다. 수술의 형태는 수분방법(충매, 풍매), 개화시 꽃받침의 존재유무 등 꿩의다리속 식물의 꽃 진화에도 관련되어 있다고 판단된다.