• International Journal of Naval Architecture and Ocean Engineering
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• 제8권3호
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• pp.277-300
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• 2016

The motion of a floating body and the free surface flow are the most important design considerations for ships and offshore platforms. In the present research, a numerical method is developed to simulate the motion of a floating body and the free surface using a fixed rectilinear grid system. The governing equations are the continuity equation and Naviere-Stokes equations. The boundary of a moving body is defined by the interaction points of the body surface and the centerline of a grid. To simulate the free surface the Modified Marker-Density method is implemented. Ships advancing in regular waves, the interaction of waves by a fixed circular cylinder array and the response amplitude operators of an offshore platform are simulated and the results are compared with published research data to check the applicability. The numerical method developed in this research gives results good enough for application to the initial design stage.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.111-112
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• 2000

The breakdown characteristics of surface discharge investigated experimentally agree well with the analytic results of previous reports [1-3] in various electrode geometries. Additionally, we find that the electrode geometry effects on the firing voltage can be understood with the ionization probability relating to the number of priming particles. We have also observed the shape of surface discharge and the surface striations in the gap geometry with the pressure, the applied voltage, and the driving frequency.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권3호
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• pp.610-625
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• 2015

In this paper the wave run-up around a circular column in regular waves is numerically calculated to investigate the applicability of the Modified Marker-Density (MMD) method to prediction of wave run-up around an offshore platform. The MMD method is one of the methods to define the highly nonlinear free surface. The governing equations are the Navier-Stokes equations and the continuity equation which are computed in Cartesian grid system. To validate incident waves generated by numerical simulation, those are compared with the solutions of the Stokes $5^{th}$ order wave theory. The wave run-up simulations are performed varying the steepness and period of incident waves as referred experimental data. The numerical results are compared to the experimental data and the results show good agreements.

• 한국어병학회지
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• 제24권3호
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• pp.205-211
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• 2011

충북 청원군 병천천에서 채집된 시료 중 붕어 5마리에서 모두 거머리가 관찰되었고, 잉어는 10마리 중 5마리에서 거머리의 기생이 확인되었다. 잉어에서의 거머리 기생은 국내에서 처음으로 확인되었다. 붕어 아가미는 거머리의 흡혈로 인하여 새엽 상피세포의 증가, 새판에 존재하는 모세혈관의 확장, 새판 일부분과 새엽이 소실, 새판 상피세포들은 수종변성(hydrophic degeneration), 울혈, 새판 및 새엽 상피세포의 증식 등이 관찰되었다. SEM으로 관찰한 결과 새판이 인접하는 새판과 점진적으로 융합되어, 결국은 새엽 하나가 원통모양으로 변형되었다. 또한, 붕어 아가미 새엽의 자유면에 존재하는 미세융기의 부분적인 파괴가 관찰되었다. 새엽 상피층이 파괴된 부분에는 연골기질이 외부로 노출되었고, 그 주변에는 다수의 혈구들이 산재하고 있었다. L. sinensis의 18S rRNA 분석은 형태학적 분류와 일치하지 않았다.

• Journal of Biosystems Engineering
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• 제26권2호
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• pp.147-154
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• 2001

In Korea and Japan, dried oak mushrooms are classified into 12 to 16 different categories based on its external visual quality. And grading used to be done manually by the human expert and is limited to the randomly sampled oak mushrooms. Visual features of dried oak mushrooms dominate its quality and are distributed over both sides of the gill and the cap. The 2nd prototype computer vision based automatic grading and sorting system for dried oak mushrooms was developed based on the 1st prototype. Sorting function was improved and overall system for grading was simplified to one stage grading instead of two stage grading by inspecting both front and back sides of mushrooms. Neuro-net based side(gill or cap) recognition algorithm of the fed mushroom was adopted. Grading was performed with both images of gill and cap using neural network. A real time simultaneous discharge algorithm, which is good for objects randomly fed individually and for multi-objects located along a series of discharge buckets, was developed and implemented to the controller and the performance was verified. Two hundreds samples chosen from 10 samples per 20 grade categories were used to verify the performance of each unit such as feeding, reversing, grading, and discharging unites. Test results showed that success rates of one-line feeding, reversing, grading, and discharging functions were 93%, 95%, 94%, and 99% respectively. The developed prototype revealed successful performance such as the approximate sorting capability of 3,600 mushrooms/hr per each line i.e. average 1sec/mushroom. Considering processing time of approximate 0.2 sec for grading, it was desired to reduce time to reverse a mushroom to acquire the reversed surface image.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1997년도 제12회 학술발표회 논문개요집
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• pp.154-154
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• 1997

• Journal of Ship and Ocean Technology
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• 제8권2호
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• pp.61-69
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• 2004

Unsteady nonlinear wave motions on the free surface over a plane beach of constant slope are numerically simulated using a finite difference method in rectangular grid system. Two-dimensional Navier-Stokes equations and the continuity equation are used for the computations. Irregular leg lengths and stars are employed near the boundaries of body and free surface to satisfy the boundary conditions. Also, the free surface which consists of markers or segments is determined every time step with the satisfaction of kinematic and dynamic free surface conditions. Moreover, marker-density method is also adopted to allow plunging jets impinging on the free surface. The second-order Stokes wave theory is employed for the generation of waves on the inflow boundary. For the simulation of wave breaking phenomena, the computations are carried out with the plane beach of constant slope in surf zone. The results are compared with other existing experimental results. Agreement between the experimental data and the computation results is good.

• Composites Research
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• 제26권1호
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• pp.42-47
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• 2013

본 연구에서는 공기역학적 또는 열 전달에 유리한 형상인 딤플을 복합재료 제품의 표면에 다수 형성하는 경제적이고도 효과적인 성형방법을 개발하였다. 금형을 이용하여 제품의 표면에 다수의 딤플을 형성시키려면 몰드의 표면에 볼록한 반구형상을 가공하여야 하는데 이렇게 하려면 높은 금형 제작비가 소요된다. 본 연구에서는 다수의 원형 구멍이 뚫린 판재를 이용하여, 이의 표면에 복합재료 스킨을 입히면서 외부에서 압력을 가하여 딤플 형상이 표면에 자연스럽게 형성되도록 하는 방법을 개발하였다. 표면에 다수의 딤플을 갖는 복합재료는 공기저항을 줄이거나 방열효과가 필요한 고속 경기용 자동차의 외장 등으로 널리 응용 될 수 있을 것으로 사료된다.

• 한국환경보건학회지
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• 제28권5호
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• pp.102-105
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• 2002

2001년 9월 19일부터 동년 10월 3일까지 Hartfield Marine Science Center Aquarium에서 구입한 볼락류 Sebastes melanops 7마리의 아가미에 부착한 단생 흡충류를 조사하였다. 파악기와 정소 수를 근거로 한 불락류(S. melanops)의 단생 흡충류는 Microcotyle sebastis였다.M. sebastis의 감염률은 42.9%이었고 감염강도는 1-11(평균 2.0)을 나타내었다. 단생 흡충류의 감염부위는 주로 감염어 아가미의 제 2차와 제 3차 새변이었다. 따라서, 아가미의 제 2차와 제 3차 새변 표면은 M. sebastis의 분포에 영향을 끼치고 있음을 알 수 있었다.

• 수산해양기술연구
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• 제46권1호
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• pp.10-19
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• 2010

As a series of studies about improvement of yellow croaker drift gill net fishing gear and development of the labor saving fishing system, this study analyzed the behavior characteristics of fishing gear, which does use three types of different sinker materials in the field tests. The result of maritime performance test indicated that the fishing gear which used the lead reached the maximum depth and bio ceramics hauled to the surface of water the fastest. The correlation between the sinking time (St) and depth (Dsl, Dsc, Dsb) of maritime performance test can be shown such experimental equations as Dsl=2.70St - 0.75, Dsc = 2.38St - 1.15, Dsb = 1.77St - 4.00. The correlation between the hauling time (Ht) and depth (Dhl, Dhc, Dhb) of maritime performance test can be shown such experimental equations as and Dhl = 7.88Ht + 35.48, Dhc = 7.80Ht + 40.01, Dhb = 7.95Ht + 36.44.