• Journal of the Society of Naval Architects of Korea
• /
• v.47 no.2
• /
• pp.242-247
• /
• 2010

To consider effects of essential parameters of water impact pressure on dynamic structural responses of bow bottom structures, a parametric study for a ship bottom panel is carried out. The idealized pressure time history models were assumed by triangular and rectangular shapes in time domain. The main loading parameters are duration time and peak pressure value maintaining the same impulse value. The structural models for local bottom stiffened panels of a container ship are analysed. The natural frequency analysis and transient dynamic response analysis are performed using MSC/NASTRAN. Added mass effects of contacting water are considered and the pressure distributions are assumed to be uniform in the whole water contacting surface. The effects of loading parameters on the structural responses, especially maximum displacements, are considered. Besides the peak pressure value, effects of duration time correlated with natural frequencies are thought to be the important parameters.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.6
• /
• pp.765-771
• /
• 2019

With the increase in the speed of ships and the size of ocean structures, the importance of flow noise has become increasingly critical in meeting regulatory standards. However, unlike active investigations in aeroacoustics fields for airplanes and trains, which are based on acoustic analogy methods for tonal and broadband frequency noise, only the discrete blade passing frequency noise from propellers is considered in marine fields. In this study, prediction methods for broadband noise in marine propellers and underwater appendages are investigated using FW-H Formulation1B, which can consider the mechanism of primary noise generation of trailing edge noise. The original FW-H Formulation 1B is based on the pressure correlation function tolackitsgeneralityandaccuracy. To overcome these limitations, wall-pressure spectrum models are adopted to improve the generality in fluid mediums. The comparison of the experimental results obtained in air reveals that the proposed model exhibits a higher accuracy within 5 dB. Furthermore, the prediction procedures for broadband noise for hydrofoils are established, and the estimation of broadband noise is conducted based on the results of the computational fluid dynamics.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.23 no.6
• /
• pp.605-612
• /
• 2021

Amid growing global damage due to abnormal weather caused by global warming, the introduction of eco-friendly cars is accelerating to reduce greenhouse gas emissions from internal combustion engines. Accordingly, many studies are being conducted in each country to prepare for the explosion of hydrogen fuel in semi-closed spaces such as tunnels and underground parking lots to ensure the safety of hydrogen-electric vehicles. As a result of predicting the explosion pressure of the hydrogen tank using the equivalent TNT model, it was found to be about 1.12 times and 2.30 times higher at a height of 1.5 meters, respectively, based on the case of 52 liters of hydrogen capacity. A review of the impact on the human body and buildings by converting the predicted maximum explosive pressure into the amount of impact predicted that all predicted values would result in lung damage or severe partial destruction. The predicted degree of damage was applied only by converting the amount of impact caused by the explosion, and considering the additional damage caused by the explosion, it is believed that the actual damage will increase further and safety and disaster prevention measures should be taken.

• Journal of Navigation and Port Research
• /
• v.38 no.4
• /
• pp.335-341
• /
• 2014

Faced with global agenda of greenhouse abatement program including regulations and $CO_2$ emission trading scheme, shipping companies are enforced to a high level of efficiency in fuel consumption. Accordingly shipbuilding companies worldwide are required to develop fuel-efficient ships which otherwise traditionally consume a great amount of fossil fuels. In this dissertation, relevant to the improvement of fuel efficiency for commercial ships, design methodology through the numerical simulations are intensively described. This work consists of derivation of effective hydrodynamic design practice based on the application of longitudinal grooves to effectively improve the pressure distribution around ship hull. The primary objective of the present study is to improve ship resistance performance using longitudinal grooves which originate from long strips on the abdomen of humpback whale. Several groove shapes have been extensively investigated and the proposed shape efficiently controlled the variation of pressure distributions acting on the hull surface.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.7
• /
• pp.50-55
• /
• 2018

The important thing in extrusion technology is the design and production of molds. Appropriate design of the molds is essential for achieving the desired extrusion of molds at the same time to maximize the life of the molds and increase their efficiency. The extrusion temperature and extrusion speed are the main parameters at the time of extrusion. Different extrusion conditions should be added depending on the extrusion ratio, physical properties of the material, and type of extrusion. In this study, the extrusion process of various 6xxx series aluminum cast alloys for high speed train interior or exterior parts were investigated. The extruded die design was performed for the 6063, 6061, 6N01, 6005, 5083 and 6060 alloy profiles and an extrusion test was conducted. In addition, the extrusion conditions, such as extrusion pressure following as the billet temperature, extrusion temperature, and materials change, were analyzed. Although the 6063 aluminum alloy can be extruded at the lowest temperature and pressure, the 6061 alloy can be extruded at the highest temperature and pressure. From these results, the successful extruded products were manufactured from these established conditions.

• The monthly packaging world
• /
• no.8 s.184
• /
• pp.66-69
• /
• 2008

원자재 가격상승과 유가 폭등으로 인해 국내 폴리에스터 업계는 중국 제품에 가격 경쟁력이 밀리는 범용 제품 비중을 줄이고 부가가치가 높은 광학 및 특수용도 제품 비중을 높여나가는 등의 노력에 주력하고 있다. 유가 인상과 단가 하락 압력, 경쟁 격화 등으로 포장재 등에 쓰이는 범용 PET 필름은 물론 확산필름 등 일반 LCD용 광학필름의 수익성이 낮아지면서 수익성이 좋은 분야의 비중을 확대하려는 움직임에 따라 올해 폴리에스터(PET) 필름 업계의 화두는 광학 및 태양전지에의 PET 필름의 적용 및 응용이었다. SKC가 먼저 광학필름의 원자재로 쓰이는 고순도 후막 베이스필름이나 태양전지나 하이브리드 자동차 부품용 필름 분야로 진출을 계획중이며 코오롱도 후막 필름 라인을 1기 증설하고 기존 포장재 라인도 전환키로 했다. 또한 도레이새한도 후막 필름을 주력제품으로 끌어올릴 계획을 갖고 있다. 본 고에서는 PET 필름 및 나일론 필름 수급동향을 살펴보고, 업체별 상황 및 전망을 살펴보도록 한다.

• Water for future
• /
• v.29 no.6
• /
• pp.217-224
• /
• 1996

In this paper, the evaluation of diameter, global velocity, global roughness coefficients of the water distribution pipes are examined by using pressure and flowrate measurements in selected points of the network. The selected pipe network parameters are determined through reformulation of the continuity and energy equation. Additional energy equation is considered to analyze the coefficient matrix. The resulting nonlinear equations are solved by using Newton Raphson method. Three computer models with complex pipe system are used to demonstrate these procedures. The computed results of hydraulic parameters show good agreements with KYPIPE2 flow analysis model.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.04a
• /
• pp.228-233
• /
• 2005

Two-dimensional Stokes flows through a micro channel with a couple of symmetric vertical fins are investigated. At far up- and down-stream from the fins, the plane Poiseuille flow exists in the channel. The slip boundary conditions are applied to take account of the Knudsen number effects. For the analysis, the method of eigen function expansion and collocation method are employed. By the results, the streamline patterns and pressure distributions are shown and the force exerted on the fin and the excess pressure drop due to the fins are determined as functions of the length of the fin and Knudsen number. It may be conjectured that the force and the excess pressure drop are almost independent of the Knudsen number.

• CDE review
• /
• v.17 no.3
• /
• pp.22-25
• /
• 2011

명확히 말하자면, '모두에 딱 들어맞는 한 사이즈는 없다.' 식의 접근은 이상적인 선반 프로젝트에 이용될 수 있다. 성공적인 프로젝트는 요구된 결과에 큰 수의 요소들을 적절히 균형 맞출 수 있는 능력의 프로그래머를 요구한다. 이 낯선 계산들 때문에, 경험이 있는 프로그래머가 가장 상업적으로 성공한 프로젝트를 운영할 수 있다. 현대 CAM 소프트웨어는 경험이 적은 프로그래머가 베테랑과 경쟁에 설 수 있는 짧은 학습 곡선을 가능하게 한다. 이것은 고려해야 할 요소들의 수를 최소화 시킴으로써 가능하다. 수학적인 계산의 툴 방향을 제공하고, 높은 수준의 프로세스를 시뮬레이션 이전에 보장하고, 회전하는 축에 부가되는 압력을 줄여 주고 자재의 부피를 효율적으로 크게 줄여주는 앞선 생각의 공구경로 알고리즘을 이용함을 통해 성공적인 5축 선반 프로젝트는 보다 편리하게 목표에 도달할 수 있도록 해준다.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1994.04a
• /
• pp.59-60
• /
• 1994

도금공업은 주로 금속, 플라스틱 등을 소재로 하는 각종 제품의 표면을 전기적 또는 화학적 방법에 따라 석출된 비철금속질로 피복가공하여 제품의 내식, 장식적 효과 내마모성, 전기특성, 광택성, 열특성등 많은 기능을 부가하는 것을 의미한다. 이러한 도금산업은 각종 유해한 화학물질을 취급하는 관계로 도금폐수도 역시 많은 유독한 화학약품이 포함되어 있어 엄격한 규제가 요구되고 있다. 현재의 도금폐수처리는 대부분 위탁업자에 의해 이루어 지고 있으며, 위탁업자는 웅집침전법에 의한 슬러지화(함수율 80% 이하) 하여 매립되고 있는 실정이다. 이 매립물은 침출수를 방출하여 환경에 새로운 문제를 야기시키고 있다. 이러한 도금폐수 중 유가금속(Zn, Cr, Ni, Cu등)을 membrane을 이용하여 회수하고, 생성되는 물을 도금공정에 다시 투입하므로서 공해가 없는 무공해공정을 설계하는 기초자료를 얻는데 본 연구의 목적이 있다. 본 실험에서는 유가금속 중 Cr을 회수하기 위하여 Cr도금 모델폐수를 이용하여 Cr의 농도, 압력, pH등을 변화시키면서 membrane과 Cr의 상관성을 살펴보았다.