• 한국해양공학회지
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• 제21권5호
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• pp.18-24
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• 2007

The environmental value of coastal vegetation has been widely recognized. Coastal vegetation such as reed forests and seaweed performs several useful functions, including maintaining water quality, supporting fish (and, thus, fisheries), protecting beaches and land from wave attack, stabilizing sea beds and providing scenic value. However, studies on the physical and numerical process of wave propagation, sediment transport and bathymetric change are few and far between compared to those on the hydrodynamic roles of coastal vegetation. In general, vegetation flourishing along the coastal areas attenuates the incident waves through momentum exchange between stagnated water mass in the vegetated area and rapid mass in the un-vegetated area. This study develops a numerical model for describing the wave attenuation and sediment transport in a wave channel in a vegetation area. By comparing these results, the effects of vegetation properties, wave properties and model parameters are clarified.

• Computers and Concrete
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• 제21권4호
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• pp.419-429
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• 2018

Climate changes, such as increasing of $CO_2$ concentration and global warming, will impact on the carbonation service life of concrete structures. Moreover, slag blended concrete has a lower carbonation resistance than control concrete. This study presents a probabilistic numerical procedure for evaluating the impact of climate change on carbonation service life of slag blended concrete. This numerical procedure considers both corrosion initiation period and corrosion propagation period. First, in corrosion initiation period, by using an integrated hydration-carbonation model, the amount of carbonatable substances, porosity, and carbonation depth are calculated. The probability of corrosion initiation is determined through Monte Carlo method. Second, in corrosion propagation period, a probabilistic model is proposed to calculate the critical corrosion degree at surface cracking, the probability of surface cracking, and service life. Third, based on the service life in corrosion initiation period and corrosion propagation period, the whole service life is calculated. The analysis shows that for concrete structures with 50 years service life, after considering climate changes, the service life reduces about 7%.

• 한국CDE학회논문집
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• 제13권4호
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• pp.243-254
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• 2008

As modular production becoming increasingly widespread in globalized manufacturing industries, sub modules or parts of the final product are being provided by many suppliers. Some part suppliers design their own products for themselves. In some cases, part suppliers provide the same type of product to multiple OEM companies. Because all part suppliers and OEM companies typically cannot use the same CAD system, engineering change in the CAD model of one company cannot be directly propagated to related CAD models of other companies. Even if two companies use the same CAD system, it may be difficult to share their CAD model owing to corporate security policy. In this paper, a neutral reference model that consists of a neutral skeleton model and an external reference data model is proposed as a new medium for the sharing and propagation of engineering change information among collaborating companies.

• 한국자동차공학회논문집
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• 제9권1호
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• pp.45-56
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• 2001

A constant volume combustion chamber is employed to investigate the initial flame kernel development and flame propagation of gasoline-air mixtures with various ignition systems, ignition energy and spark plug electrodes. To do this research, four ignition systems are designed and manufactured, and the ignition energy is controlled by varying the dwell time. Several kinds of spark plugs are also made to analyze the effects of electrodes on flame kernel development. The velocity of flame propagation is measured by the laser deflection method. The output laser beam from He-Ne laser is divided into three parallel beams by a beam splitter. The splitted beams pass through the combustion chamber. They are deflected when contacted with flame front, and the voltage signals from photodiodes change due to deflection. The results show that higher ignition energy raises the flame propagation speed especially under the fuel lean operation. The wider electrode gap, smaller electrode diameter and sharper electrode tip make the speed of the initial flame propagation faster. The speed of the initial flame propagation is affected by electrode material as well. Electrode material with lower melting temperature help the initial flame propagation.

• 한국광학회지
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• 제6권4호
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• pp.345-351
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• 1995

유한한 폭을 갖는 배경에서 기본 어두운 공간솔리톤의 진행특성을 실험적으로 연구하여 전산시늉한 결과와 비교하였다. 실험적으로 빔의 세기가 증가함에 따라 어두운 솔리톤의 폭이 감소하고 배경의 폭은 증가함을 확인하였고 무한한 폭의 배경을 가정한 솔리톤 상수로부터 구한 굴절율의 변화량은 Z-스캔 방법으로 구한 굴절율의 변화량보다 작았다. 유한한 폭을 갖는 배경에 놓인 기본 어두운 솔리톤의 진행을 전산시늉하여 진행거리에 따른 배경의 첨두세기, 어두운 솔리톤의 폭 그리고 솔리톤 상수의 변화를 연구하였다. 유한한 크기의 배경에서 솔리톤상수의 변화를 고려하여 구한 굴절율의 변화량은 Z-스캔 방법으로 구한 굴절율의 변화량과 일치하였다.

• 한국해양공학회지
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• 제5권2호
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• pp.58-66
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• 1991

Not only difference of fatigue crack growth and propagation behavior resulted from the grain size, the hardness ratio and volume fraction in M.E.F. dual phase steel composed of martensite in hard phase and ferrite in soft phase, but also the effects of the plastic constraint were investigated by fracture mechanics and microstructural method. The main results obtained are as follows: 1) The fatigue endurance of M.E.F. steel increases with decreasing the grain size, increasing the ratio of hardness and volume fraction. 2) The initiation of slip and crack occures faster as the stress level goes higher. These phenomena result from the plastic constraint effect of the second phase. 3) The crack propagation rate in the constant stress level is faster as the grain size gets larger, the ratio of hardness lower and volume fraction smaller.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.311-314
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• 2007

The experimental method of measuring dynamic properties of structures was presented. The method is based on the flexural wave propagation characteristics. Using the method, change in structural dynamic properties due to damage is measured. The crack has much more significant impact on the strain energy than the inertial effects. From this, the sensitivity of the dynamic stiffness on the crack location is estimated by calculating the strain energy. When the wave propagates, the strain and kinetic energies shows cyclic changed over space. The crack that occurred at locations where the wave energy is in the form of the potential energy affected most significantly the wave propagation characteristics. The effects of crack location on the wave propagation were used to determine the crack location.

• Journal of the Optical Society of Korea
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• 제10권4호
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• pp.162-168
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• 2006

The variation of global coherence on propagation plane by plane is examined in the framework of coherent mode representation. It is explained through concrete examples that the global coherence may in general be enhanced, may be reduced, or may not change. When the mode functions form a complete set and the corresponding eigenvalues are in nitely degenerate, there necessarily develops a certain amount of global coherence on propagation, which is the essence of van Cittert-Zernike theorem. The propagation generates a certain pattern of the eigenvalue spectrum from the initial flat one and this is shown to be related to the non-unitarity of the propagation kernel.

• 한국공작기계학회논문집
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• 제11권2호
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• pp.43-49
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• 2002

SB41 material is welded automatically and is investigated some effects of the welding residual stress in the growth and propagation of fatigue crack, so as to study the fatigue behaviour in the welding residual stress field. The summarized results are as follows; 1) In case of the load amplitude is constant, as the stress ratio is changing to 0.1, 0.33 and 0.5 the propagation life is constant but the growth life decreases. And than, when maximum load or minimum load is constant as the stress ratio increases the growth life and propagation life. 2) It was shown that fatigue crack propagation ratio da/dN was almost constant regardless of the stress ratio change at constant load amplitude and that the larger stress ratio, the slower was the fatigue crack propagation ratio. 3) The opening ratio U is influenced by $K_max$ but it isn't only the function of $K_max$ because data range is very large. 4) The fatigue life of the specimens on tensile compressive residual stress field was decreased and increased respectably more than that of the base metal.

• 한국CDE학회논문집
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• 제8권2호
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• pp.90-100
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• 2003

Engineering change (EC) objects are the data structure and related operations that can support applications for EC procedures or processes. Their functionalities include controlling management data, specifying related product structure, and archiving a history of product structure changes for EC management. In this paper we introduce a systematic approach to support the propagation of changes between different product structure views using the history of structure changes in EC objects. The change propagations supported by EC objects enable designers to maintain the consistency of multiple product structure views for engineering, manufacturing or even customer support applications. This paper also includes EC examples and experimental implementations for the proposed EC objects.