• Journal of Advanced Marine Engineering and Technology
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• v.29 no.7
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• pp.713-721
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• 2005

A marine diesel engine should realize optimal operation efficiency while reducing NOx, PM (Particulate Matters) and other emissions. Fuel injection systems that use electronic control can become an effective means of achieving that objective. However. it still needs some accurate and instant information in order to bring its ability into full potential while sailing on the sea. The important information of them are a shaft torque and continuous combustion pressures of all cylinders. The shaft torque and the propeller thrust described in this paper are measured at an intermediate shaft by using a unique principle that one of two electromagnet coils oscillates a vibrating strip which the length changes with force and the other coil picks up the change of the frequency of the vibrating strip. For further reference, the shaft power meter multiplied the torque by the shaft revolution has already had about 750 sets of sales performance. The research presented in this paper started about ten years ago and is concerned with the development of a combustion pressure sensor that uses the same principle. Recently, the pressure sensor which bears continuous operation has been developed after a hard struggle, that is, the system that consists of a shaft horsepower meter, a propeller thrust meter and a combustion pressure sensor has been completed and has been shown to be reliable. This paper describes the configuration of this system, the material of the combustion pressure sensor, the principle of that, and the improving point of the sensor, and, we finally consider the use of this system.

• Journal of the korean society of oceanography
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• v.38 no.4
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• pp.166-172
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• 2003

Multi­Sensor Core Logger (MSCL) is a useful system for logging the physical properties (compressional wave velocity, wet bulk density, fractional porosity, magnetic susceptibility and/or natural gamma radiation) of marine sediments through scanning of whole cores in a nondestructive fashion. But MSCL has a number of problems that can lead to spurious results depending on the various factors such as core slumping, gas expansion, mechanical stretching, and the thickness variation of core liner and sediment. For the verification of MSCL data, compressional wave velocity, wet bulk density, and porosity were measured on discrete samples by Hamilton Frame and Gravimetric method, respectively. Acoustic impedance was also calculated. Physical property data (velocity, wet bulk density, and impedance) logged by MSCL were slightly larger than those of discrete sample, and porosity is reverse. Average difference between MSCL and discrete sample at both sites is relatively small such as 22­24 m/s in velocity, $0.02­-0.08\;g/\textrm{cm}^3$ in wet bulk density, and 2.5­2.7% in porosity. The values also show systematic variation with sediment depth. A variety of factors are probably responsible for the differences including instrument error, various measurement method, sediment disturbance, and accuracy of calibration. Therefore, MSCL can be effectively used to collect physical property data with high resolution and quality, if the calibration is accurately completed.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.1
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• pp.74-86
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• 2014

The optimization techniques are explored in the direction of arrival (DOA) estimation based on single acoustic pressure gradient vector sensor (APGVS). By analyzing the working principle and measurement errors of the APGVS, acoustic intensity approaches (AI) and the minimum variance distortionless response beamforming approach based on single APGVS (VMVDR) are deduced. The radius to wavelength ratio of the APGVS must be not bigger than 0.1 in the actual application, otherwise its DOA estimation performance will degrade significantly. To improve the robustness and estimation performance of the DOA estimation approaches based on single APGVS, two modified processing approaches based on single APGVS are presented. Simulation and lake trial results indicate that the performance of the modified approaches based on single APGVS are better than AI and VMVDR approaches based on single APGVS when the radius to wavelength ratio is not bigger than 0.1, and the two modified DOA estimation methods have excellent estimation performance when the radius to wavelength ratio is bigger than 0.1.

• Earthquakes and Structures
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• v.21 no.6
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• pp.587-599
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• 2021

The modified-ECOMAC approach to monitor and investigate health of structure in marine platforms was evaluated in this research. The material properties of structure were defined based on the real platform located in Persian Gulf. The nonlinear time-history analyses were undertaken using the marine natural waves. The modified-ECOMAC approach was designed to act as the solution of the best sensor placement according to structural dynamic behavior of structure. This novel method uses nonlinear time-history analysis results as an exact seismic response despite the common COMAC algorithms utilize the eigenvalue responses. The processes of modified-ECOMAC criteria were designed and developed by author of this paper as a toolbox of Matlab. The Results show that utilizing an efficient ECOMAC method in SHM process leads to detecting the critical weak points of sensitive marine platforms to make better decision about them. The statistical results indicate that considering modified ECOMAC based on seismic waves analysis has an acceptable accuracy on identify the sensor location. The average of statistical comparison of COMAC and ECOMAC via modal and integrated analysis, had a high MAE of 0.052 and RSME of 0.057 and small R2 of 0.504, so there is significant difference between them.

• Journal of the Korean Institute of Navigation
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• v.12 no.2
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• pp.33-42
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• 1988

As a basic study for enhancing the sensitivity of the follow-up system of the marine gyrocompass, the geometric characteristics of the deflection sensor were investigated and the theoretical model of it was formulated. The output signal voltage of the deflection sensor was esamined by changing the attitude of gyrosphere against follow-up container. The characteristics of the output are found to be indentical with those of the distance difference versus the relative azimuthal deflection of the gyrosphere against the follow up container. On the base of the theoretical model, some useful points for the design of the deflection sensor are suggested as following : 1. When the difference between semidiamter of gyrophere and that of the follow-up container decreases, the sensitivity of deflection sensor increases. 2. If the semidiameter difference of two spheres is constant, the sensitivity of deflection sensor is proportional to the magnitude of the semidiamter of each sphere. 3. The farther the gyrosphere is deviated from the center of follow-up container, the higher the sensitivity of deflection sensor is. 4. It is recommendable that the value of the datum deflection of the electrodes on the gyrosphere should be within the range between $4^{\circ}$ and $16^{\circ}$deviated from north-south line.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.1
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• pp.191-198
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• 2001

In order to comprise a basic closed-loop control system for hydraulic systems it is necessary to detect the piston rod stroke of a hydraulic cylinder. There are many conventional type sensors which can detect the displacement of cylinders. However, they cannot reveal the original performance normally or they cannot be applied at all where the operating circumstance of cylinders is beyond specifications of sensors. Especially, for the purpose of detecting the strokes of cylinders mounted on heavy equipments, a special exclusive sensor must be used because the operating circumstances of heavy equipments are so severe that general purpose sensors cannot endure such circumstance as shock and a residual vibration induced by rough works. In this paper, an exclusive method for detecting the piston rod stroke for heavy equipments is suggested, which adopts a remote detecting technique using optical fiber sensors. Several experiments using the prototype are executed for verifying the effectiveness of the suggested method and the possibility of the accurate detection of stroke.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.105-109
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• 2000

Micronization of sensor is a trend of the silicon sensor development with regard to a piezoresistive silicon pressure sensor the size of the pressure sensor diaphragm have become smaller year by year and a microaccelerometer with a size less than 200-300${\mu}m$ has been realized. In this paper we study some of the micromachining processes of SOI(silicon on insulator)for the microaccelerometer and their subsequent processes which might affect thermal loads. The finite element method(FEM) has been a standard numerical modeling technique extensively utilized in structural engineering discipline for design of SOI wafers. Successful thermal behaviors analysis and design of the SOI wafers based on the tunneling current concept using SOI wafer depend on the knowledge abut normal mechanical properties of the SCS(single crystal silicon)layer and their control through manufacturing process

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.7
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• pp.778-783
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• 2013

Measurement of liquid level in storage and processing vessels, tanks, wells, reservoirs and hoppers is commonly needed. The several different ways to measure the liquid level of oil or water tank have been provided such as an electrostatic capacity, a supersonic waves and an optical science etc. In the study, we have constructed the stable and efficient measurement system to measure the level of liquid at real-time and to get accurate measurement of the maximum and minimum level of the tank. For this purpose, we suggest double sensing methods by adopting both capacitive and optical sensing. The experimental results, presented in this paper, illustrate the effectiveness of the proposed method under different sensing methods.

• Journal of Fisheries and Marine Sciences Education
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• v.19 no.3
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• pp.510-516
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• 2007

The efficiency of magnetic compass direction sensor and magnetic compass by the laboratory experiment for the apparatus of generating artificial magnetic force and the onboard experiment on the fishing boat of coastal pot at the outside of Pusan Namhang were investigated. The results showed that the bearing angle of magnetic compass direction sensor was coincided with that of magnetic compass. However, the performance of magnetic compasses was unsuitable under the ISO rule by the characteristic experiment of damping curve. Therefore, the use of autopilot system using magnetic compass direction sensor which is based on the magnetic compass needs the sufficient notice.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.8
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• pp.919-926
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• 2006

To move in unknown or uncertain environment, a mobile robot must collect informations from various sensors and use it to construct a representation of the external world. Ultrasonic sensor can provide range data for this purpose in a simple cost-effective way. However conventional ultrasonic sensor system for a mobile robot are not sufficient for environment recognition because of their large beam opening angle, specular reflection. This paper describe on environmental perception algorithm which can solve these problems in case using ultrasonic sensor. The algorithm consist of two parts. One is to solve beam opening angle problem by fusion from multiple ultrasonic sensors. The other is to cope with specular reflection problem in wall line extract, which is based on Hough Transform. Experiments to verify the validity of the proposed algorithm are carried out, and the results are provided at last part in this paper.