• Journal of Ship and Ocean Technology
• /
• 제4권4호
• /
• pp.34-44
• /
• 2000

This paper deals with the sea trial results of a fast craft with the hybrid supported type hul form. waterjet propulsion system and motion control system. The hybrid-type container ship operable in the sea with a wave height of y6 m, a speed of 50 knots and a payload of 1,500 tons were designed. A 1/8 scale 10 m- long test craft was constructed and tested in open seas. The hydrodynamic performance such as speed, turning, motion control in waves and waterjet thrush was analyzed.

• Nuclear Engineering and Technology
• /
• 제55권3호
• /
• pp.1118-1124
• /
• 2023

Experimental study on the fluidelastic instability (FEI) of a curved tube bundle in single phase downward cross flow is investigated for the design qualification and analysis input preparation of helical coiled steam generator tubing. A 6×9 normal square curved tube array with equal and different vertical/horizontal pitch-to-diameter ratio was under-tested up to 6 m/s in term of gap flow velocity to measure the critical velocity for FEI. The critical velocity for FEI was measured at the turning point from the vibration amplitude plot along the gap flow velocity. Our test results were compared with straight tube results and published data in the design guideline. The applicability of the current design guidelines to a curved tube bundle is also assessed. We found that introducing frequency difference in a curved tube array increases the critical velocity for fluidelastic instability.

• 한국정밀공학회지
• /
• 제11권5호
• /
• pp.124-133
• /
• 1994

Many of non-contact measuring systems are used to estimate surface characteristics owing to their advantages of high speed and undanaged test. In this paper, a new measuring system is proposed to acquire image from CCD camera through back light illumination. Lowpass filter is very useful in view of noise removal and optimum binary image can be made through histogram equalization which is one of the histogram technique to maximize brightness intensity between workpiece and background. Laplacian operator is used to detect workpiece edge from binary image. In case of image treatment applying Laplacian operator, surface roughness is calculated by introducing conversion coefficient for coordinate of pixel which edge is composed of. In summary, the work is concerned with the development of a new technique for roughness measurement by the image processing in turning.

• 한국자동차공학회논문집
• /
• 제22권6호
• /
• pp.113-119
• /
• 2014

For the robust design of Motor Driven Power Steering (MDPS) systems, it is important to consider energy efficiency from every aspect such as system configuration and current flow, etc. If design optimization is not considered, it has many problems on a vehicle. For example, when evaluating steering test, particularly the Catch-up test which turning the steering wheel left or right quickly, steering effort should be increased rapidly. Also a vehicle might have poor fuel efficiency. In this study, it is calculated energy consumption for each component of the steering system and analyzed factors of energy consumption. As a result, this paper redefines a method to estimate steering input torque using characteristics of vehicle electric components and then conducts an analysis of contribution for the Catch-up.

• 전자공학회논문지
• /
• 제49권11호
• /
• pp.103-109
• /
• 2012

논문에서는 천해역에서 운용가능한 소형의 자율무인잠수정 "BOTO"의 개발과 실해역 자율주행 성능시험에 관한 내용을 다룬다. BOTO의 개발을 위해 6자유도 운동방정식을 이용하여 시뮬레이션을 수행하였으며, 시뮬레이션 결과를 바탕으로 소형 자율무인잠수정을 개발하였다. 시뮬레이션에 사용되는 운동모델의 계수와 주행성능을 확인하기 위해 회류수조에서 저항계수 측정 시험도 수행하였다. 운동모델을 기반으로 무인잠수정의 선회반경 시뮬레이션과 수평면에서의 경로추종을 위한 알고리즘을 적용하여 시뮬레이션을 수행하였고, 설계된 제어기를 이용하여 실해역 자율주행시험을 수행하였다. 실해역 자율주행시험은 선회반경 측정시험과 경로점 추종시험을 실시하였으며, 실해역에서 목표 경로점을 잘 추종하는 것을 확인하였다.

• Geomechanics and Engineering
• /
• 제20권5호
• /
• pp.411-420
• /
• 2020

Numbers fitting-curve equations have been proposed to predict soil-water retention curve (SWRC) whose parameters have no definitude physical meaning. And these methods with precondition of measuring SWRC data is time-consuming. A simplified directly method to estimate SWRC without parameters obtained by fitting-curve is proposed. Firstly, the total SWRC can be discretized into linear segments respectively. Every segment can be represented by linear formulation and every turning point can be determined by the pore-size distribution (PSD) of Mercury Intrusion Porosimetry (MIP) tests. The pore diameters governing the air-entry condition (AEC) and residual condition (RC) can be determined by the PSDs of MIP test. The PSD changes significantly during drying in SWR test, so the determination of AEC and RC should use the PSD under corresponding suction conditions. Every parameter in proposed equations can be determined directly by PSD without curve-fitting procedure and has definitude physical meaning. The proposed equations give a good estimation of both unimodal and bimodal SWRCs.

• 한국항해항만학회지
• /
• 제36권9호
• /
• pp.707-714
• /
• 2012

Recently, tug boats are widely used for towing a barge which transports building materials, a large block of a ship, offshore crane, and so on. In order to simulate the dynamics of the coupled towing system correctly, the dynamics of the towline should be well modeled. In this paper, the towline was modeled as the multiple finite elements, and each element was assumed as a rigid cylinder which moves in five degrees of freedom except roll. The external tension and its moment acting on each element of the towline were modeled depending on the position vector's direction. Tugboat's motion was simulated in six degrees of freedom where wave and current effects were included, and towed barge was assumed to move in the horizontal plane only. In order to confirm the mathematical models of the coupled towing systems, standard maneuvering trials such as course changing maneuver, turning circle test and zig-zag test were simulated. In addition, the same trials were simulated when the external disturbances like wave and current exist. As the result, it is supposed that the results might be qualitatively reasonable.

• 대한조선학회논문집
• /
• 제51권2호
• /
• pp.154-161
• /
• 2014

Naval ships have hull appendages which are more exposed to the outside because of its small block coefficient compared with commercial ships. These exposed hull appendages like skeg, strut and shaft line affect the maneuverability of a ship. The effect of hull appendages has considered at initial design stage to estimate more accurate maneuverability. In this paper, sensitivity analysis is used to analyze the effect on maneuverability by hull appendages. 3 DOF maneuvering equations based on Mathematical Modelling Group (MMG) model are used and propeller & rudder model are modified to reflect the characteristics of twin propeller & twin rudder. Numerical maneuvering simulations (Turning test, Zig-zag test) for benchmark naval vessel, David Taylor Model Basin (DTMB) 5415 are performed. In every simulation, it is calculated that stability indices and maneuverability characteristics (Tactical Dia., Advance, 1st Overshoot, Time of complete cycle) with respect to the parameters (area times lift coefficient slope, attachment location) of hull appendages. As a result, two regression formulas are established. One is the relation of maneuverability characteristics and stability indices and the other is the relation of stability indices and hull appendages.

• 대한조선학회논문집
• /
• 제43권2호
• /
• pp.171-176
• /
• 2006

To improve ship's maneuverability high lift rudders like as Schilling rudder, flap rudder etc. were used. To predict the maneuverability of a ship with flap rudder HPMM tests are carried out. To analyze the test results modular model is used. To use modular model the forces of flap rudder must be measured separately from the hull forces. The flap rudder is made as independent system from the hull. To investigate the simulation results of modular model the tests results are analyzed by whole ship model, and simulated. The compared results of simulation show a good agreement except turning test. The reason is the different analysis result of flap rudder drag forces. From the present study it is possible to analyze HPMM tests of a ship with flap rudder by modular model.

• 전기학회논문지
• /
• 제61권5호
• /
• pp.711-716
• /
• 2012

To assess the insulation deterioration of stator windings, diagnostic and AC breakdown tests were performed on the eleven high voltage (HV) motors rated at 6kV. After completing the diagnostic tests, the AC overvoltage test was performed by gradually increasing the voltage applied to the stator windings until electrical insulation failure occurred, to obtain the breakdown voltage. Stator winding of motors 1, 3, and 8 failed at above rated voltage at 14 kV, 13.8kV, and 16.4kV, respectively. The breakdown voltage of three motors was higher than expected for good quality windings in 6kV motors. Based on deterioration evaluation criteria, the stator winding insulation of eleven HV motors are confirmed to be in good condition. The turning point of the current, $P_{i2}$, in the AC current vs. voltage characteristics occurred between 5kV and 6kV, and the breakdown voltage was low between 13.8kV and 16.4kV. There was a strong correlation between the breakdown voltage and various electrical characteristics in diagnostic tests including Pi2.