• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.54 no.2
• /
• pp.181-187
• /
• 2018

In order for the probe to perform ocean exploration and survey research, it is necessary to adjust the position of the ship as desired by dynamic positioning system. The dynamic positioning system of T/S NARA is applied to K-POS dynamic positioning system of Kongsberg, which makes maintaining the ship's position, changing position and heading control possible. T/S NARA is not capable of dynamic positioning if one or more propulsive forces are lost with DP Level One. However, it is predicted that dynamic positioning can be achieved even at the time of missing one thrust in a good sea condition. Therefore, we want to analyze the effect of each propulsion on the performance of dynamic position system. When one of the bow thruster and azimuth thrusters lost their propulsion, maintaining the ship's position, changing position and heading control performance were compared and analyzed. If the situation occurred disable from using the bow thruster, they can not maintain ship's position. Azimuth thruster was influential for the ship's position control and bow thruster was influential in heading control. The excellent dynamic positioning performance can be achieved, considering the propulsion power that will have a impact on each situation in the future.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.5
• /
• pp.31-36
• /
• 2015

As one of the most promising propulsive systems in the future, the dual-mode scramjet engine has drawn the attention of many researches. Detailed flow features concerned with the isolator play an important role in the dual-mode scramjet system. The 2D numerical method has been used for the dual-mode scramjet with wind tunnel. To validate the ability of the numerical model, numerical results have been compared with the experimental results. Overall pressure distributions show quite good match with the experimental results. Back pressure has been studied for maximum pressure rising. According to the results, pressure distribution of supersonic inlet section is not influenced by back pressure. The shock train is pushed towards upstream as the back pressure increases. The maximum value of back pressure without inlet unstart goes up rapidly and then keeps constant when the isolator length increases. The optimal length of isolator section ($L/H_{th}$) is 8.7 in this model.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.7 no.2
• /
• pp.45-53
• /
• 2012

A policy of entrepreneurship support increases recently. A policy of entrepreneurship support provide from infra to direct support in various. Quantity scale increase but quality levels are inadequate. In this paper, we provide an overview of the role of Graduate school of Entrepreneurial management on the development of entrepreneurship in Korea. This study aims exploratory research that the role of graduate school of entrepreneurial management in the diffusion of entrepreneurship and entrepreneurship culture. This study review the support of entrepreneurship structure(youth entrepreneurship, domestic support of entrepreneurship system, abroad support of entrepreneurship system) and the propulsive strategy(the business of SOE, 4th Generation Business Incubator, organizational structure of entrepreneurship business center, contents of entrepreneurship education).

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.6
• /
• pp.788-793
• /
• 2012

This study was focused on the estimations of air pollutants, such as PM(Particulate matters), SOx(Sulfur Oxides), $CO_2$(Carbon diOxides) and NOx(Nitrogen Oxides), from a diesel propulsion engine installed on a naval vessel. Legislative and regulatory actions for exhaust emissions from ships are being strengthened in international communities and national governments to protect human health and the environment. In this context, various technologies have been developed from all of the nations of the world to meet strict standards. These regulations are based on commercial ship applications and according to size, but are not suitable for military naval vessels, which have much different engine operating conditions and hull architectures. Additionally, there is no international emission control system for military ships. Emission factors have been updated for commercial ship types from work at various research institutes; however, it is difficult to develop emission factors for military vessels because of their characteristics. In this paper, exhaust emissions from diesel engines installed on naval vessels under steady navigation condition were estimated with emission inventory methodology applied to ocean going vessels using fuel-based methods and fuel sulfur content analysis.

• Journal of computational fluids engineering
• /
• v.21 no.3
• /
• pp.15-23
• /
• 2016

In the present study, two phase flows around a projectile vertically launched from an underwater platform have been numerically investigated by using a three dimensional multi-phase RANS flow solver based on pseudo-compressibility and a homogeneous mixture model on unstructured meshes. The relative motion between the platform and projectile was described by six degrees of freedom equations of motion with Euler angles and a chimera technique. The propulsive power of the projectile was modeled as the fluid force acting on the lower surface of the body by the compressed air emitted from the underwater platform. Various flow conditions were considered to analyze the fluid-dynamics motion parameters of the projectile. The water level of platform and the current speed around the projectile were the main parametric variables. The numerical calculations were conducted up to 0.75sec in physical time scale. The dynamics tendency of the projectile was almost identical with respect to the water level variation due to the constant buoyancy term. The moving speed of the projectile along the vertical axis inside the platform decreased when the current speed increased. This is because the inflow from outside of the platform impeded development of the compressed air emitted from the floor surface of the launch platform. As a result, the fluid force acting on the lower surface of the projectile decreased, and injection time of the projectile from the platform was delayed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.12
• /
• pp.1435-1440
• /
• 2014

The effects of the specimen size and temperature on the compressive strength of ATJ graphite were investigated. Compressive tests were conducted in accordance with ASTM C 965 at room temperature, $700^{\circ}C$ and $900^{\circ}C$. Three types of cylindrical specimen at room temperature were used in uniaxial tests, where the diameter-to - length ratios were one to two for the ASTM standard specimen, one to one for the Type I specimen, and one to 0.5 for the Type II specimen. Two kinds of cylindrical specimens, with and without antioxidant coating, were tested at elevated temperature. The Compressive strength of the expanded specimens(Type I, II) were slightly higher than that of standard specimen at room temperature. The compressive strength of a specimen with antioxidant coating increased as the temperature increased to $900^{\circ}C$. In contrast, that of the non-coated specimen decreases sharply due to the oxidation of the specimen.

• Journal of Navigation and Port Research
• /
• v.33 no.6
• /
• pp.437-442
• /
• 2009

The PID controller type autopilot is applied to support shipmaneuvering for course-keeping and heading control. A control constants of autopilot system should be evaluated by promoting energy loss (fuel consumption) from the view point of economic efficiency of the ship. This paper is obtained control constants of autopilot system from the RCGA pursued the minimum energy loss. In addition, the controller which is designed involves a constrained optimization problem. The performance of the proposed method is demonstrated through a set of simulation.

• Journal of Navigation and Port Research
• /
• v.38 no.6
• /
• pp.585-591
• /
• 2014

The primary objective of the current work is to predict speed performance of the medium patrol boat over $F_N=0.5$ employing experimental materials based on the CFD before model tests. In other words, the predicted brake powers according to ship speeds are assessed satisfying the main engine capacity. The subject ships are selected the two different stern hull forms. The flow computation are conducted considering free surface and dynamic trim using a commercial CFD code(STAR-CCM+). The resistances of the bare-hull are obtained from CFD. Wave patterns, pressures and limiting streamlines on the hull and velocity distribution in the propeller plane for the two hull forms are compared using CFD. The effective powers of the object ships are assessed based on CFD. Resistance increase according to the attached appendages and quasi-propulsive efficiency are employed the experimental datas. Speed performance prediction method concerning high speed vessels like a medium patrol boat is developed employing CFD and experimental data.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.7
• /
• pp.574-579
• /
• 2016

Grid systems used in previous studies were determined to be valid only if the length between the perpendiculars in a model ship was in the range of 6-8 m, and the maximum dynamic trim angle was smaller than $1^{\circ}$. The application of the grid system to a small fishing boat can create numerical instability because the dynamic trim of small boats is generally larger than $3^{\circ}$, and their Froude numbers are in the range of 0.3-0.8. In the present study, resistances of a small fishing boat were stably obtained by reducing the length between the center of buoyancy and the inlet boundary of the numerical domain, and by refining grid cells vertically in a region that would be swept by a free surface. The effective power of the small fishing boat was predicted based on the ITTC-1978 two-dimensional analysis. By using the results of previous towing tank tests, the coefficient of quasi-propulsive efficiency and the brake horsepower at a design draft were calculated.

• Health Policy and Management
• /
• v.23 no.4
• /
• pp.415-426
• /
• 2013

Background: This study was aim to identify the specific words and to develop the scale for the public health center (PHC) image. Methods: We collected 824 words from the previous studies and by open questions and reduced them by 77 words, then which were rated properly by 355 citizens of Seoul. We examined explanatory factor analysis for 69 words, and examined content validity test and confirmatory factor analysis (CFA) for the image structures (4 factors and 16 words). And then we developed the image questionnaire using them through council. We conducted a survey and retested the PHC image scales as the measuring tool targeting 2,000 persons, and compared the inexperience and experience persons for PHC usage. Results: The image structures were consisted of 4 factors and 16 words such as 'trustworthiness' (warm, exemplary, faithful, service-mindedness, beneficial to health), 'fairness' (honesty, clear, consistent, ruled), 'development possibility' (changing, goal-directed, developmental, propulsive), and 'flexibility' (not authoritative, not perfunctory, not rigid) in total. Cronbach's ${\alpha}$ values of all factors were above 0.7. As a result of CFA, model fit indexes yielded satisfactory results (root mean square error of approximation [RMSEA] 0.049, goodness of fit index [GFI] 0.937, and adjusted goodness of fit index [AGFI] 0.912). According to the result of retest for measuring tool by using other samples, Cronbach's ${\alpha}$ values were above 0.8, and model fit indexes yielded satisfactory results (RMSEA 0.059, GFI 0.952, AGFI 0.933). RMSEAs of the inexperiences and the experiences were each 0.59, 0.68. Conclusion: A reliable, valid, and generalizable scale was created for PHC image.