• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1777-1783
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• 2020

As a part of R&D work for the high intensity proton linac of China Accelerator Driven Sub-critical System project, a superconducting half-wave cavity with a frequency of 162.5 MHz and an optimal beta of 0.15 (HWR015) has been developed at Institute of Modern Physics (IMP), Chinese Academy of Sciences. In this paper, the design and test results will be described in detail. We introduced a new stiffening strategy for the HWR cavity, the simulation results show that the cavity has much lower frequency sensitivity coefficient (df/dp), Lorentz force detuning coefficient (KL), and can achieve more stable mechanical properties. The performance of the HWR cavity operated in cryostat will be also reported.

• 마이크로전자및패키징학회지
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• 제12권3호
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• pp.267-274
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• 2005

This paper presents the fabrication of surface acoustic wave (SAW)-based pressure sensor for long-term stable mechanical compression force measurement. SAW pressure sensor has many attractive features for practical pressure measurement: no battery requirement, wireless pressure detection especially at hazardous environments, and easy other functionality integrations such as temperature, humidity, and RFID. A $41^{\circ}$ YX $LiNbO_3$ piezoelectric substrate was used because of its high SAW propagation velocity and large values of electromechanical coupling factors $K^2$. A silicon substrate with $\~200{\mu}m$ deep cavity was bonded to the diaphragm with epoxy, in which gold was covered all over the inner cavity in order to confine electromagnetic energy inside the sensor, and provide good isolation of the device from its environment. The reflection coefficient $S_{11}$ was measured using network analyzer. High S/N ratio, sharp reflected peaks, and clear separation between the peaks were observed. As a mechanical compression force was applied to the diaphragm from top with extremely sharp object, the diaphragm was bended, resulting in the phase shifts of the reflected peaks. The phase shifts were modulated depending on the amount of applied mechanical compression force. The measured $S_{11}$ results showed a good agreement with simulated results obtained from equivalent admittance circuit modeling.

• Journal of Biosystems Engineering
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• 제37권3호
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• pp.155-165
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• 2012

This study was performed to offer the data for design of the seedling bed transfer equipment to make the automation of working process in a plant factory. The seedling bed transfer equipment pushing the seedling bed with bearing wheels on the rail for interconnecting each working process by a pneumatic cylinder was made and examined. The examined transfer force to push the seedling bed with a weight of 178.9 N by the pneumatic cylinder with length of 60 cm and section area of 5 $cm^2$ was measured by experiments. The examined transfer forces was compared with theoretical ones calculated by the theoretical formula derived from dynamic system analysis according to the number of the seedling bed and pushing speed of the pneumatic cylinder head at no load. The transfer function of the equipment with the input variable as the pushing speed $V_{h0}$(m/s) and the output variable as the transfer force f(t)(N) was represented as $F(s)=(V_{h0}/k)(s+B/M)/(s(s^2+Bs/M+1/(kM))$ where M(kg), k(m/N) and B(Ns/m) are the mass of the bed, the compression coefficient of the pneumatic cylinder and the dynamic friction coefficient between the seedling bed and the rail, respectively. The examined transfer force curves and the theoretical ones were represented similar wave forms as to use the theoretical formular to design the device for the seedling bed transfer. The condition of no vibration of the transfer force curve was $kB^2>4M$. The condition of transferring the bed by the repeatable impact and vibration force according to difference of transfer distance of the pneumatic cylinder head from that of the bed was as $Ce^{-\frac{3{\pi}D}{2\omega}}<-1$, where ${\omega}=\sqrt{\frac{1}{kM}-\frac{B^2}{4M^2}}$, $C=\{\frac{\frac{B}{2M}-\frac{1}{kB}}{\omega}\}$, $D=\frac{B}{2M}$. The examined mean peak transfer force represented 4 times of the stead state transfer force. Therefore it seemed that the transfer force of the pneumatic cylinder required for design of the push device was 4Bv where v is the pushing speed.

• 한국전산구조공학회논문집
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• 제17권2호
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• pp.183-192
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• 2004

본 논문에서는 수직으로 시추된 해양 파일에 대한 새로운 동적 해석절차가 제안되고 전형적 설계문제에 의하여 검증된다. 해수에 잠긴 파일의 구조는 물론 해양파도와 조류에 의한 힘도 유한요소법에 의해서 정식화되고 모델링된다. 유한요소 방정식에 적합한 파력을 구하기 위해서 여러 가지 파도이론 가운데서도 Airy의 파도이론이 시험되고 선정되었다. 조류의 후방와류에 기인한 횡방향 양력은 Strouhal 진동수와 적절한 양력계수를 가진 간단한 조화함수에 기초한다 파일에 대한 고유진동수 해석과 주파수 응답해석은 정식화 결과를 NASTRAN에 입력하여 계산되었다. 여기서 제안된 절차에 의해 얻어진 동적 변위와 응력의 결과는 기본설계해석 단계로서 해양파일의 파력과 조류 양력에 의한 동적거동을 구할 수 있으며 설계에 응용될 수 있음을 보여준다

• 한국산학기술학회논문지
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• 제21권1호
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• pp.409-416
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• 2020

전세계적으로 다양한 규모의 지진이 계속하여 발생하고 있으므로 원자로용 격납구조가 구조적인 건전성을 유지하기 위해서는 내진성능의 확보가 필수적이다. 따라서 소형 원자로용 모듈화 격납구조의 경우에도 내진성능의 분석이 필요하다. 본 연구에서는 소형 원자로용 모듈화 격납구조의 내진성능 분석을 위해 콘크리트 모듈 간 접촉면과 긴장재를 반영한 유한요소 모델을 작성하여 고유진동해석과 지진해석을 수행한다. 이를 통해 입력지진파에 의한 모듈화 격납구조의 변위, 응력 및 연결부 접촉면 갭 크기의 변화특성을 분석한다. 그리고 긴장력, 연결부 접촉면 마찰계수 및 입력지진파의 변화가 내진성능에 미치는 영향을 분석한다. 비교를 위해 일체화 격납구조의 내진성능도 분석한다. 긴장재의 긴장력과 모듈 연결부 접촉면의 마찰력에 의한 합성효과로 모듈화 격납구조는 발생 가능성이 가장 높은 1, 2차 고유모드에서 일체화 격납구조와 유사한 횡방향 동적거동을 한다. 긴장재의 긴장력과 연결부 접촉면의 마찰력에 의한 합성효과가 충분히 발휘될 경우, 연결부를 갖는 모듈화 격납구조에서도 일정수준 이상의 내진성능이 확보된다. 연결부 접촉면 재질을 마찰계수가 더 큰 재료로 바꿀 경우 추가적인 내진성능 향상이 기대된다.

• 한국해안·해양공학회논문집
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• 제31권2호
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• pp.73-87
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• 2019

파랑의 작용에 의해 유사가 이동되어 연안의 침식 퇴적이 일어나지만 상당히 비선형적이고 비정상적인 과정이므로, 파랑과 침식 퇴적의 상관성을 밝히고 예측하기는 쉽지 않다. 본 연구는 동해안에서 비디오 모니터링으로 얻은 5개 지점의 해빈폭 자료와 인근의 3개 지점의 파랑 모니터링 자료를 연계하여 상관성을 분석하였다. 전체 자료에 대한 상관분석에서는 유의미한 상관성이 없었지만, 기간 및 파랑 조건에 따른 상관분석에서는 주목할 만한 결과들이 제시되었다. 파고의 비초과확률이 약 99% 이상인 경우에는 주기와 해빈폭 변화 사이에 강한 음의 상관성이 있었으며, 주기의 비초과확률이 약 99% 이상인 경우에는 파고와 해빈폭 변화 사이에 강한 음의 상관성이 있었다. 주파향이 해안선 직각 방향과 인접한 경우, 주파향으로 입사하는 파랑에 대해 해빈폭이 확연히 감소하였다. 해빈폭과 파랑 사이에 뚜렷한 계절적 상관성이 나타나지는 않았으나, 태풍과 같은 특정 사건의 영향을 크게 받는 것으로 나타났다. 이러한 연구 결과의 실제 현장 적용을 위해서는 이와 같은 조건에 따른 상관 분석을 상세히 하여 해빈폭 변화 경향의 기준이 되는 파랑에 대해 더욱 정확한 정보를 얻을 필요가 있다.

• 대한조선학회논문집
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• 제51권2호
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• pp.122-129
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• 2014

Identification of the whipping response out of the combined wave-vibration response of a flexible sea going vessel is one of the most interesting research topic from ship designer's point of view. In order to achieve this goal, a novel methodology based on the wavelet cross-correlation technique was proposed in this paper. The cross-correlation of the wavelet power spectrum averaged across the frequency axis was introduced to check the similarity between the combined wave-vibration response and impulse response. The calculated cross-correlation of the wavelet power spectrum was normalized by the auto-correlation of the each spectrum with zero time lag, eventually providing the cross-correlation coefficient that stays between 0 and 1, precisely indicating the existence of the impulse response buried in the combined wave-vibration response. Additionally, the weight function was introduced while calculating the cross-correlation of the two spectrums in order to filter out the signal of lower frequency so that the accuracy of the similarity check becomes as high as possible. The validity of the proposed methodology was checked through the application to the artificially generated ideal combined wave-vibration signal, together with the more realistic signal obtained by running 3D hydroelasticity program WISH-Flex. The correspondence of the identified whipping instances between the results, one from the proposed method and the other from the calculated slamming modal force, was excellent.

• 대한조선학회지
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• 제14권3호
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• pp.13-22
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• 1977

The hydrodynamic forces acting on a forced oscillating 2-dimensional cylinder on a free surface of a fluid of a finite depth are calculated by distributing singularities on the immersed body surface. And the Haskind-Newman relation in a fluid of a finite depth is derived. The wave exciting force of the cylinder to an oscillation is also calculated by using the above relation. The method is applied to a circular cylinder swaying in a water of finite depth, and then, to a rectangular cylinder heaving, swaying, and rolling. The results of above cases give a good agreement with those by earlier investigators such as Bai, Keil, and Yeung. Also, this method is applied to a Lewis form cylinder with a half beam-to-draft ratio of 1.0 and a sectional area coefficient of 0.941, and to a bulbous section cylinder which is hard to represent by a mapping function. The results reveal that the hydrodynamic forces in heave increase as the depth of a water decrease, but in sway or roll, the tendency of the hydrodynamic forces is difficult to say in a few words. The exciting force to heave for a bulbous section cylinder becomes zero at two frequencies. The added mass moment of inertia for roll is seemed to mainly depend on the sectional shape than the water depth.

• 수산해양기술연구
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• 제52권4호
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• pp.299-307
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• 2016

This study aims to investigate effects of the length of the buoy and sand bag line on the loss of webfoot octopus pot. A numerical modeling and simulation was carried out to analyze the process that the pot gear affected by wave using the mass spring model. Through the simulation, tensions of sand bag line under various condition were investigated by length of buoy and sand bag line. The drag force and coefficient k of an artificial shell used in the webfoot octopus pot was obtained from an experiment in a circular water channel, and the coefficient k was applied to the simulation. To verify the accuracy of the simulation model, a simple test was conducted into measuring a rope tension of a hanging shell under flow. Then, the test result was compared with the simulation. The lengths of the buoy line in the simulation were 1.12, 1.41, 1.80, 2.23, 2.69, and 3.17 times of water depth. The lengths of sand bag line were 10, 20, 30, and 40 meters, and conditions of water depth were 8, 15, 22 meters. 4 meter height and 8 second period of wave were applied to all simulations. As a results, the tension of the sand bag line was decreased as the buoy and sand bag line were increased. The minimum tension of the sand bag line was appeared in conditions that the length of the buoy line is twice of water depth and the sand bag line length is over 40 meters (except in case of depth 8 meters.).

• 대한조선학회지
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• 제13권1호
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• pp.11-16
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• 1976

The effect of the bow shape on the ship motion response in longitudinal regular waves of water of finite depth is investigated by employing the strip theory. The two-dimensional hydrodynamic forces(added mass and damping) were calculated by close-fit method for water of finite depth. The models for investigation are U and V bow ship forms of block coefficient 0.8 with constant after body which were used by Yourkov [2] and recently by Kim [3] for their deep water investigations. The following results are obtained by the present numerical experiments. (1) It is confirmed that the damping coefficient of the V-bow ship is greater than that of U-bow ship and in consquence the amplitude of heave and pitch of V-bow ship is smaller than that of U-bow ship among longitudinal regular head waves in water of finite depth (2) The merit of the V-bow ship on the motion damping is more significant in heave than in pitch, and is decreasing with the shallowness of water depth. (3) The change of bow form gives little effect on the wave exciting force and moment compared with the motion responce.