• Title/Summary/Keyword: Marine noise

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Experimental and analytical study on hydroelastic vibration of tank (선박내 접수탱크 진동에 대한 실험/이론적 연구)

  • Kim, Kuk-Su;Cho, H.D.;Kong, Y.M.;Heo, J.H.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.96-100
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    • 2008
  • In this paper, a experimental and theoretical study is carried out on the hydroelastic vibration for a rectangular bottom and side plate of tank. It is assumed that the tank wall is clamped along the plate edges. The fluid velocity potential is used for the simulation of fluid domain and to obtain the added mass due to plate vibration. It is assumed that the fluid is imcompressible and inviscid. Assumed mode method is utilized to the plate model and hydrodynamic force is obtained by the proposed approach. The coupled natural frequencies are obtained from the relationship between kinetic energies of a wall including fluid and the potential energy of the wall. The theoretical result is compared with the three-dimensional finite element method. In order to verify the result, modal test was carried out for bottom/side plate of tank model by using impact hammer. It was found the fundamental natural frequency of bottom plate is lower than that of side plate of tank and theoretical result was in good agreement with that of commercial three-dimensional finite element program.

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Development of Engine Vibration Analysis and Monitoring System(EVAMOS) for Marine Vessels (선박용 엔진 진동 분석 및 모니터링 시스템(EVAMOS) 개발에 관하여)

  • Lee, D.C.;Joo, K.S.;Nam, T.K.;Kim, E.S.;Kim, S.H.
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.2
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    • pp.155-161
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    • 2009
  • Engine builders have separately developed and applied torsional, axial and structural vibration monitoring system on most marine engines. These systems displayed their results for engine or ship operation engineers and were not regularly stored at the hardware of computer. So, the history and trend of various engine and hull vibrations were not supported for preventive maintenance and to protect the failure of these activity or function. The integrated vibration or stress monitoring system(EVAMOS : engine vibration analysis and monitoring system) in marine diesel engine, its accessories and hull structure have been developed by the dynamics laboratory of Mokpo Maritime University during last 3 years. This paper introduces the design conception and ability of commercial software EVAMOS with field data on several actual tests.

Noise Removal of Radar Image Using Image Inpainting (이미지 인페인팅을 활용한 레이다 이미지 노이즈 제거)

  • Jeon, Dongmin;Oh, Sang-jin;Lim, Chaeog;Shin, Sung-chul
    • Journal of the Society of Naval Architects of Korea
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    • v.59 no.2
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    • pp.118-124
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    • 2022
  • Marine environment analysis and ship motion prediction during ship navigation are important technologies for safe and economical operation of autonomous ships. As a marine environment analysis technology, there is a method of analyzing waves by measuring the sea states through images acquired based on radar(radio detection and ranging) signal. However, in the process of deriving marine environment information from radar images, noises generated by external factors are included, limiting the interpretation of the marine environment. Therefore, image processing for noise removal is required. In this study, image inpainting by partial convolutional neural network model is proposed as a method to remove noises and reconstruct radar images.

Analysis of Reducing Tonal Noise of the Gas Turbine Generator in order to Reduce Underwater Radiated Noise of a Naval Vessel (수중방사소음 저감을 위한 함정용 개스터빈 발전기의 순음 저감 분석)

  • Han, Hyung-Suk;Choi, Ki-Yong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.10a
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    • pp.155-162
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    • 2009
  • Because the tonal sound of the underwater noise in a naval vessel can be identified from the sub-marine of the enemy, it should be reduced sufficiently. This kind of the noise usually comes from the structure-borne noise of the onboard machine and transfers to the sea through the hull of the ship. The vibration at the high frequency can be reduced sufficiently with damping material. In this paper, the damping coefficient of the steel plate with damping sheet is evaluated by experiment. Using these evaluated properties, the numerical analysis is performed in order to evaluate how much vibration of the generator can be reduced applying damping sheet on the encloser and base of it.

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Analysis of Reducing Tonal Noise of the Gas Turbine Generator in order to Reduce Underwater Radiated Noise of a Naval Vessel (수중방사소음 저감을 위한 함정용 개스터빈 발전기의 순음 저감 분석)

  • Han, Hyung-Suk;Choi, Ki-Yong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.12
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    • pp.1329-1337
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    • 2009
  • Because the tonal sound of the underwater noise in a naval vessel can be identified from the sub-marine of the enemy, it should be reduced sufficiently. This kind of the noise usually comes from the structure-borne noise of the onboard machine and transfers to the sea through the hull of the ship. The vibration at the high frequency can be reduced sufficiently with damping material. In this paper, the damping coefficient of the steel plate with damping sheet is evaluated by experiment. Using these evaluated properties, the numerical analysis is performed in order to evaluate how much vibration of the generator can be reduced applying damping sheet on the encloser and base of it.

LNA Design Uses Active and Passive Biasing Circuit to Achieve Simultaneous Low Input VSWR and Low Noise (낮은 입력 정재파비와 잡음을 갖는 수동 및 능동 바이어스를 사용한 저잡음증폭기에 관한 연구)

  • Jeon, Joong-Sung
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.8
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    • pp.1263-1268
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    • 2008
  • In this paper, the low noise power amplifier for GaAs FET ATF-10136 is designed and fabricated with active bias circuit and self bias circuit. To supply most suitable voltage and current, active bias circuit is designed. Active biasing offers the advantage that variations in the pinch-off voltage($V_p$) and saturated drain current($I_{DSS}$) will not necessitate a change in either the source or drain resistor value for a given bias condition. The active bias network automatically sets a gate-source voltage($V_{gs}$) for the desired drain voltage and drain current. Using resistive decoupling circuits, a signal at low frequency is dissipated by a resistor. This design method increases the stability of the LNA, suitable for input stage matching and gate source bias. The LNA is fabricated on FR-4 substrate with active and self bias circuit, and integrated in aluminum housing. As a results, the characteristics of the active and self bias circuit LNA implemented more than 13 dB and 14 dB in gain, lower than 1 dB and 1.1 dB in noise figure, 1.7 and 1.8 input VSWR at normalized frequency $1.4{\sim}1.6$, respectively.

Optimum Design of 3-Axis Sensor System for Vibration Measurement Using Piezoresistive type MEMS Sensor (압전저항형 멤스센서를 이용한 진동 측정용 3축 센서 시스템의 최적화 설계)

  • Seo, Sang-Yoon;Bae, Dong-Myung;Lee, Jong-Kyu;Choi, Byeong-Keun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.12
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    • pp.1082-1089
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    • 2013
  • 3-Axis sensor measurement system is needed for measuring ride quality of elevator. But because 3-Axis piezoelectric accelerometer is expensive. We developed 3-Axis sensor system which is suitable for measuring ride quality of elevator using cheap MEMS sensor. There are two types of MEMS sensor that are piezoresistive and capacitive type. The excellence of piezoresistive type in characteristic of frequency response and noise is confirmed compare to capacitive type as a result of this paper's experiment and reference. 3-Axis system using MEMS sensor needs MEMS's proper frequency response characteristic. Additionally noise characteristic of sensor and circuit, stiffness of assembly are needed for deciding frequency range and accuracy of amplitude.