• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.220-223
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• 2008

Large curved plate blocks are widely used to construct hull structure in shipbuilding industry. Most curved plates are manufactured by using manual method called as line heating that use deformation caused by residual stress after local heating along a line which is perpendicular to the curvature direction. However, its working environment is poor and its formability is totally dependent on an experienced technician. In view of that, multi-point dieless forming (MDF) technology that use reconfigurable punch arrays instead of one piece die is proposed in this study. The MDF process is based on a concept of equivalent die surface made by numbers of punches which has round tip at the end of it. In this study, numerical simulation for common curvature type such as saddle shape was carried out. In addition, experiments in the plate forming process were also conducted to compare with the numerical results in view of final configuration. Consequently, it was noted that the proposed dieless forming method has considerable feasibility to substitute the new process for conventional manual method.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.238-248
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• 2019

In the high-temperature and high-pressure irradiation environments, the multi-field coupling processes of hydrogen diffusion, hydride precipitation and mechanical deformation in Zircaloy cladding tubes occur. To simulate this hydrogen-induced complex behavior, a multi-field coupling method is developed, with the irradiation hardening effects and hydride-precipitation-induced expansion and hardening effects involved in the mechanical constitutive relation. The out-pile tests for a cracked cladding tube after irradiation are simulated, and the numerical results of the multi-fields at different temperatures are obtained and analyzed. The results indicate that: (1) the hydrostatic stress gradient is the fundamental factor to activate the hydrogen-induced multi-field coupling behavior excluding the temperature gradient; (2) in the local crack-tip region, hydrides will precipitate faster at the considered higher temperatures, which can be fundamentally attributed to the sensitivity of TSSP and hydrogen diffusion coefficient to temperature. The mechanism is partly explained for the enlarged velocity values of delayed hydride cracking (DHC) at high temperatures before crack arrest. This work lays a foundation for the future research on DHC.

• Journal of Mechanical Science and Technology
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• 제17권5호
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• pp.766-775
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• 2003

The intermittent spray characteristics of a multi-hole diesel nozzle with a 2-spring nozzle holder were investigated experimentally. Without changing the total orifice exit area, the hole number of the multi-hole nozzle varied from 3 (d$\_$n/=0.42 mm) to 5 (d$\_$n/=0.32 mm). The time-resolved droplet diameters of the spray including the SMD (Saute. mean diameter) and the AMD (arithmetic mean diameter), injected intormittently from the multi-hole nozzles into still ambient ai., were measured by using a 2-D PDPA (phase Doppler particle analyze.). The 5-hole nozzle spray shows the smaller spray cone angle, the decreased SMD distributions and the small difference between the SMD and the AMD, compared with that of the 3-hole nozzle spray. From the SMD distributions with the radial distance, the spray structure can be classified into the three regions : (a) the inner region showing the high SMD distribution , (b) the mixing flow region where the shea. flow structure would be constructed : and (c) the outer region formed through the disintegration processes of the spray inner region and composed of fine droplets. Through the SMD distributions along the spray centerline, it reveals that the SMD decreases rapidly after showing the maximum value in the vicinity of the nozzle tip. The SMD remains the constant value near the Z/d$\_$n/=166 and 156.3 for the 3-hole and 5-hole nozzles, which illustrate that the disintegration processes of the 5-hole nozzle spray proceed more rapidly than that of the 3-hole nozzle spray.

• Journal of Plant Biotechnology
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• 제34권1호
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• pp.1-6
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• 2007

고추냉이 (Wasabia japonica) 종자로부터 기내 무균상태 하에서 발아된 유묘에서 절취한 shoot-tip을 이용하여 대량증식 방법을 구명하기 위해 MS 기본배지에 BA 농도 및 반고체배지, filter paper bridge, 액체진탕배양 등의 배양방법을 달리하여 multi-shoot을 유도하였다. 1.0 mg/L BA가 들어있는 액체진탕배양에서 2주 동안 배양한 후 반고체배지에서 4주 동안 배양한 방법이 신초 수가 22.8개 그리고 신초의 길이가 3.5cm로 가장 양호한 결과를 보였으며 한 개의 shoot-tip으로부터 약 $5{\sim}11$개의 분할묘를 얻을 수 있었다. 또한 부정근을 유도하고자 여러 가지 농도의 IBA 및 NAA가 함유된 반고체배지에서 9주간 배양한 결과 배양 4주 이후부터 부정근이 출현하기 시작하였다. IBA (0.01 mg/L)가 NAA처리 보다는 부정근 형성에 효과가 있었으나 위의 두 생장조절물질이 전혀 첨가되지 않은 배지가 90.0%의 부정근 형성율을 보이면서 가장 양호한 것으로 나타났다. 잎과 뿌리가 잘 발달된 재분화묘를 원예용상토 (bio-media Co., peatmoss $8{\sim}10%$, coir dust $66{\sim}70%$, zeolite $13{\sim}17%$, vermiculite $3{\sim}7%$, perlite $2{\sim}4%$)에 넣어 2주간 습도를 높게 유지시킨 후 육묘온실에서 순화시킨 결과 모든 개체가 정상적인 형태로 성장하였다.

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1693-1701
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• 2002

The intermittent spray characteristics of a multi-hole and a single-hole diesel nozzle were experimentally investigated. The hole number of the multi-hole nozzle was 5, and the hole diameter of the 5-hole and the single-hole nozzle was the same as d$\_$n/=0.32 ㎜ with the constant hole length to diameter ratio(l$\_$n//d$\_$n/=2.81). The droplet diameters of the spray, including the time-resolved droplet diameter, SMD (Sauter mean diameter) and AMD (arithmetic mean diameter) , injected intermittently from the two nozzles into the still ambient were measured by using a 2-D PDPA (phase Doppler particle analyzer). Through the time-resolved evolutions of the droplet diameter, it was found that the structure of the multi-hole and the single-hole nozzle spray consisted of the three main parts : (a) the leading edge affected by surrounding air. and composed of small droplets; (b) the central part surrounded by the leading edge and mixing flow region and scarcely affected by the resistance of air, (c) the trailing edge formed by the passage of the central part. The SMD decreases gradually with the increase in the radial distance, and the constant value is obtained at the outer region of the radial distance (normalized by hole diameter) of 7-8 and 6 for the 5-hole and single-hole nozzle, respectively. The SMD along the centerline of the spray decrease shapely with the increase in the axial distance after showing the maximum value near the nozzle tip. The SMD remains the constant value near the axial distance(normalized by hole diameter) of 150 and 180 for the 5-hole and the single-hole nozzle, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권10호
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• pp.4903-4929
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• 2018

In this study, a fully automatic pose and expression invariant 3D face alignment algorithm is proposed to handle frontal and profile face images which is based on a two pass course to fine alignment strategy. The first pass of the algorithm coarsely aligns the face images to an intrinsic coordinate system (ICS) through a single 3D rotation and the second pass aligns them at fine level using a minimum nose tip-scanner distance (MNSD) approach. For facial recognition, multi-view faces are synthesized to exploit real 3D information and test the efficacy of the proposed system. Due to optimal separating hyper plane (OSH), Support Vector Machine (SVM) is employed in multi-view face verification (FV) task. In addition, a multi stage unified classifier based face identification (FI) algorithm is employed which combines results from seven base classifiers, two parallel face recognition algorithms and an exponential rank combiner, all in a hierarchical manner. The performance figures of the proposed methodology are corroborated by extensive experiments performed on four benchmark datasets: GavabDB, Bosphorus, UMB-DB and FRGC v2.0. Results show mark improvement in alignment accuracy and recognition rates. Moreover, a computational complexity analysis has been carried out for the proposed algorithm which reveals its superiority in terms of computational efficiency as well.

• Composites Research
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• 제14권1호
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• pp.39-46
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• 2001

본 논문에서는 신경망 제어기를 이용하여 복합재 보의 적응 다중 모드 진동 제어에 관한 실험적 연구를 수행하였다. 신경망 제어기는 계산량이 많기 때문에 실시간 적용에 어려움이 따른다. 본 논문에서는 진동 신호를 모드별로 분리하기 위한 적응 노치 필터를 제안하였다. 연결 강도의 개수가 적어서 계산량이 적은 두 개의 신경망 제어기를 이용하여 각 모드의 제어력을 계산하였다. 끝단 질량의 위치의 차이로 인해 고유 진동수가 다른 두 시편 A, B에 대하여 적응 노치 필터와 신경망 제어기를 이용한 적응 진동 제어를 수행한 결과, 두 경우 모두 효과적으로 진동 제어가 이루어졌다. 이러한 결과로 시스템 파라미터의 변환에 대한 신경망 제어기의 적응 진동 제어 성능을 확인할 수 있다.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.101-108
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• 2007

This paper presents an efficient meshless method for analyzing cracked piezoelectric structures subjected to mechanical and electrical loading. The method employs an element free Galerkin (EFG) formulation and an enriched basic function as well as special shape functions that contain discontinuous derivatives. Based on the moving least squares (MLS) interpolation approach, The EFG method is one of the promising methods for dealing with problems involving progressive crack growth. Since the method is meshless and no element connectivity data are needed, the burdensome remeshing procedure required in the conventional finite element method (FEM) is avoided. The numerical results show that the proposed method yields an accurate near-tip stress field in an infinite piezoelectric plate containing an interior hole. Another example is to study a ceramic multilayer actuator. The proposed model was found to be accurate in the simulation of stress and electric field concentrations due to the abrupt end of an internal electrode.

• 한국IT서비스학회지
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• 제10권2호
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• pp.75-94
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• 2011

The industrial ecosystem around the Internet services has been evolving since the Internet was first introduced. The Net Neutrality issue best represents the process of the evolution and presents an inevitable challenge that the industry should overcome. This paper deals with this structural change with the Two-Sided Market framework and provides a System Dynamics(SD) model to evaluate the economic implications of the net neutrality policy. In particular, our approach analyzes the policy impacts when two competing platforms (network providers) play a role of the platform in a typical two-sided market, which connects Content Providers(CPs) with users. Previous studies show that the indirect network externality between these two markets makes the entire system tip to one platform. When the multi-homing in the CP market is allowed as in our model, however, their argument may lose its validity. To examine the system behavior, conducted here is SD simulations of our model. The simulation results show that co-existence of the competing platforms persists with the network effects over a certain threshold. The net neutrality policy seems to lower the threshold based on our experimental outcomes.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.275-278
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• 2006

A steam turbine is one of propulsion systems of a LNG carrier, which consists of high pressure (HP) and low pressure (LP) turbines. In order to obtain high power, each one has the form of a multi-stage turbine. Especially, the first stage of a HP turbine is Curtis stage and uses partial admission considering the turbine efficiency. The performance of a HP turbine can be predicted by a mean-line analysis method, because the relatively large value of hub-tip ratio makes the three-dimensional losses small. In this study, a performance analysis method is developed for a multi-stage HP turbine using Chen's loss model developed for the transonic steam turbines. To consider the feature of partial admission, different partial admission models are reviewed, This analysis method can be used in partial load conditions as well as full load condition. The calculation results are also compared with the CFD results about some simple cases to check the accuracy of the program. Performance of two HP turbine models are calculated, and the calculation results are compared with the designed data. The comparison shows the qualitative performance analysis result.