• International Journal of Fluid Machinery and Systems
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• 제9권4호
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• pp.325-331
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• 2016

A bathtub vortex above the outlet of a rotating barrel is simulated. By analyzing the Ekman layer theory, it can be found that the main flow circulation is inversely proportional to the thickness of Ekman layer. The thicker the Ekman boundary layer, the weaker the rotational strength and the shorter of the length of gas core is. According to this law, models of barriers with rods of different heights are established. The reduction of air-core length in this air entrainment vortex and weakening the strength of rotation field were achieved.

• 한국수자원학회논문집
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• 제52권4호
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• pp.235-243
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• 2019

급격한 기상변화로 인한 극한 강우와 집중폭우의 발생빈도 증가로 기존 수방시설의 한계 용량을 초과해 도심지 침수피해가 빈번하게 발생하고 있다. 최근 도시화 추세가 급격하게 빨라지면서 수방시설 등 사회기반시설에 대한 지하공간 개발의 필요성이 증가하고 있으며, 지하공간을 활용한 지하방수로와 지하저류지 기술이 급부상하고 있다. 본 연구에서는 지하유입시설의 대표적 형상인 접선식 유입구와 나선식 유입구에 대한 공기 배출효과를 분석하기 위해 유입유량 변화에 따른 수직갱 내부 공기공동(air-core)의 형상 크기를 계측했다. 나선식 유입구의 경우, 저유량 유입조건에서 와류 유도 효과를 개선하기 위해 유입부 바닥면에 계단형 다단식 구조를 도입했다. 수직갱 내부 공기공동의 전체적인 평균 단면적의 경우, 다단식 나선 유입구가 접선식 유입구보다 10% 정도 크게 나타나 고유량 유입조건에서 높은 공기 배출 효과와 유입효율을 나타냈다. 접선식 유입구의 경우, 유입구가 가지는 고유 성능을 유지할 수 있는 최대 유량 조건을 초과하면서 공기 배출 효과가 감소하기 시작했다. 또한, 실험에서 사용된 접선식 유입구와 다단식 나선 유입구 모형에 활용 가능한 기초자료를 제공하기 위해 수직갱 내부 위치에 따른 공기공동 단면적에 대한 실험식(empirical formula)을 제시했다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.678-681
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• 2000

Contactless battery charger with a "더" type core is proposed in this paper. The proposed take-apart transformer maintain a high coupling coefficient in spite of air gap. The ZV-ZCS method is used for the efficiency and stable opeation of the system.he system.

• Structural Engineering and Mechanics
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• 제32권2호
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• pp.351-370
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• 2009

This paper presents a computational study for the structural response of blast loaded metallic sandwich panels, with the emphasis placed on their failure behaviours. The fully-clamped panels are square, and the honeycomb core and skins are made of the same aluminium alloy. A material model considering strain and strain rate hardening effects is used and the blast load is idealised as either a uniform or localised pressure over a short duration. The deformation/failure procedure and modes of the sandwich panels are identified and analysed. In the uniform loading condition, the effect of core density and face-sheets thicknesses is analysed. Likewise, the influence of pulse shape on the failure modes is investigated by deriving a pressure-impulse (P-I) diagram. For localised loading, a comparative study is carried out to assess the blast resistant behaviours of three types of structures: sandwich panel with honeycomb core, two face-sheets with air core and monolithic plate, in terms of their permanent deflections and damage degrees. The finding of this research provides a valuable insight into the engineering design of sandwich constructions against air blast loads.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 박판성형기술의 진보
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• pp.199-230
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• 1994

The blanking sequence of refrigerator and air-conditioner compressor-motor-core has been determined by trial and error. To improve such problem, 2d-analysis using ANSYS to verify the deformation state has been done firstly. And 3d-analysis following up the real process has been done. Additionally, verified the 3-d analysis result using S/W LS-DYNA.

• Journal of Advanced Marine Engineering and Technology
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• 제27권7호
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• pp.879-888
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• 2003

Swirling air flow in a horizontal round tube was experimentally studied for its visualization. The present investigation deals with swirl angle, flow visualization studies and accompanying vortex core behavior by using oil smoke and a hot wire anemometer for Re = 40,000 and 50000 at X/D = 41, 59 and 71. In the swirl air flow, a vortex core was formed at high swirl intensity along the test tube. The swirl angle and the vortex core depended on the swirl intensity along the test tube. The results of swirl angles measured by flow visualization and hot wire reasonably agree with those of previous studies.

• The Journal of Advanced Prosthodontics
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• 제5권4호
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• pp.382-387
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• 2013

PURPOSE. Although several surface treatments have been recently investigated both under in vitro and in vivo conditions, controversy still exists regarding the selection of the most appropriate zirconia surface pre-treatment. The purpose of this study was to evaluate the effect of alumina (Al) and aluminium nitride (AlN) coating on the shear bond strength of adhesive resin cement to zirconia core. MATERIALS AND METHODS. Fifty zirconia core discs were divided into 5 groups; air particle abrasion with 50 ${\mu}m$ aluminum oxide particles ($Al_2O_3$), polishing + Al coating, polishing + AlN coating, air particle abrasion with 50 ${\mu}m$ $Al_2O_3$ + Al coating and air particle abrasion with 50 ${\mu}m$ $Al_2O_3$ + AlN coating. Composite resin discs were cemented to each of specimens. Shear bond strength (MPa) was measured using a universal testing machine. The effects of the surface preparations on each specimen were examined with scanning electron microscope (SEM). Data were statistically analyzed by one-way ANOVA (${\alpha}$=.05). RESULTS. The highest bond strengths were obtained by air abrasion with 50 ${\mu}m$ $Al_2O_3$, the lowest bond strengths were obtained in polishing + Al coating group (P<.05). CONCLUSION. Al and AlN coatings using the reactive magnetron sputtering technique were found to be ineffective to increase the bond strength of adhesive resin cement to zirconia core.

• 한국산업융합학회 논문집
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• 제17권3호
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• pp.103-112
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• 2014

BY the Transformers and reactors, the input electrical energy is converted into magnetic energy. At the end through the magnetic energy was passed at the output parameter. Specially At the flyback transformer or a reactor airgap were designed to contain more magnetic energy. But that work is very difficult for the optimal design. It is that Contradictions are between the length of the Air-gap, Winding inductance, DC bias. As to e Several conflicting conditions in order to determine the optimum Air-gap has a lot of experience and trial & error is necessary. The approach proposed in this paper, the auxiliary winding on the core attached to part of primary core, that by applying a DC voltage has a dramatic effect like Core with designed Air-gap. This inventiveness and advantage is to regulate arbitrarily the Saturation Flux Quantity by the input signal to secondary winding. Accordingly obtained the biggest effect is that increasing limits of the saturation current destined by the material and shape of the conventional core. In other words, that can decreas the size of the transformer and reactor, While maintaining the current saturation capacity. This paper, prove its effect as using the local flux saturation in transformers and reactors for research by the computer program using the finite element method (FEM) simulation, followed by actual experiment to verify

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권5호
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• pp.165-170
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• 2003

This paper presents development of solid core suspension disc insulators (cap and cap suspension disc insulator) for replacing cap and pin suspension disc insulators in overhead transmission and distribution lines which expose to lightning discharges. By this means the punctured problem caused by steep front surge voltage created by lightning discharge on the lines can be solved. The solid core suspension insulator was designed and constructed based on the dimensions of conventional suspension disc insulators (cap and pin insulators). The insulators are made of alumina porcelain. The electrical and mechanical characteristics of the solid core suspension insulators were carried out. The puncture test was performed in the air by applying steep front impulse voltage with amplitude about 2.5 per unit of 50% flashover (CFO) of the insulator unit at negative standard lightning impulse $1.2/50\;\mu\textrm{s}$ with steepness up to $9200\;kV/\mu\textrm{s}$. The testing results show that solid core suspension disc insulators are not punctured eventhough the steepness of the steep front impulse voltage was increased up to $9200\;kV/\mu\textrm{s}$.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권3호
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• pp.165-171
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• 2000

This paper proposes a technique to design of air-core type Linear DC Motor(LDM) by using Equivalent Magnetizing Current(EMC) method and has performed its dynamic analysis. The magnetic flux density differ in accordance with airgap position due to difference of mechanical and magnetic air gap length and the coil shape has an influence on the thrust. Therefore, the analysis of magnetic field due to the magnets is carried out by EMC. The phenomena according to the various coil various coil shape under the same Magneto Motive Force(MMF) has been analyzed and its result is applied to the design process. The appropriateness of the proposed technique is confirmed by Finite Element Method(FEM) and its dynamic analysis is carried out from the coupling of the electrical circuit equation and mechanical kinetic equation.