• 한국음향학회지
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• 제19권7호
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• pp.59-65
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• 2000

본 논문은 음성진단이나 치료를 위한 기초연구로서, 인체의 진동신호를 측정하여 그 특성을 분석한 것이다. 가진신호는 외부적인 힘이 아닌 자신의 음성이며, 진동과 공진 특성이 강한 모음 '아', '에', '이', '오', '우'를 적용하여 실험하였다. 실험장치로는 마이크로폰과 가속도계 그리고 증폭기를 이용하였으며 컴퓨터에 측정 데이터를 저장하였다. 마이크로폰으로 음성신호를 저장하면서 동시에 가속도계를 이용하여 인체 각 부위에서의 진동신호를 측정하였으며 측정 위치는 머리, 목, 몸체를 일정한 간격으로 나누어 총 63개의 위치로 정하였다. 진동 신호의 측정 위치와 횟수는 사용 목적에 따라 충분히 가변적일 수 있다. 진동 분석을 위한 파라미터는 진동 신호의 크기, 위상, 기본 진동수, 결집음폭대이며, 코히어런스 함수를 이용하여 인체의 진동신호와 음성과의 상관성을 알아보았다. 실험결과, 인체의 위치에 따라 독특한 특징들이 있음을 확인하였으며, 그 결과를 제시하였다.

• 소음진동
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• 제7권2호
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• pp.231-238
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• 1997

진동하는 구조물의 평면 진동장을 측정하기 위해, 자동화된 스캐닝 레이저 도플러 진동 측정기를 개발하고 이의 성능을 시험하였다. 광섬유를 사용하여 레이저 탐침이 진동체 표면을 따라 움직일 수 있도록 하였으며, 시스템의 자동화를 이루기 위한 알고리즘을 고안하였다. 시스템의 자동화과정은, 레이저 탐침이 진동체 표면을 따라 움직이도록 하며, 표면의 각 측정 점마다 두 레이저 광선들의 초점을 맞추고, 진동 신호 데이터를 얻고 저장하는 모든 과정을 포함한다. 따라서 이 자동화 과정을 이용하여 구조물의 표면 진동장을 측정할 수 있도록 하였다. 이 진동 측정기의 성능을 시험하기 위하여, 연속신호로 가진되는 압전 원통 셸의 진동과 펄스 신호에 의해 가진되는 평판의 진동을 측정하였다. 측정결과로부터, 구조물의 평면 진동장을 측정하고 표면을 따라 전파되는 탄성파들을 분리해내기 위하여, 이 자동화된 스캐닝 레이저 도플러 진동 측정기가 유용한 측정 도구가 될 수 있음을 보였다.

• Structural Engineering and Mechanics
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• 제30권1호
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• pp.1-20
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• 2008

The dynamic characteristics of the passive, semi-active, and active tuned-liquidcolumn dampers (or TLCDs) are studied in this paper. The design of the latter two are based on the first one. A water-head difference (or simply named as water head in this paper) of a passive TLCD is pre-set to form the so-called semi-active one in this paper. The pre-set of water head is released at a proper time instant during an earthquake excitation in order to enhance the vibration reduction of a structure. Two propellers are installed along a shaft inside and at the center of a passive TLCD to form an active one. These two propellers are driven by a servo-motor controlled by a computer to provide the control force. The seismic responses of a five-story shear building with a passive, semiactive, and active TLCDs are computed for demonstration and discussion. The responses of this building with a tuned mass damper (or TMD) are also included for comparison. The small-scale shaking-table experiments of a pendulum-like system with a passive or active TLCD to harmonic and seismic excitations are conducted for verification.

• Earthquakes and Structures
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• 제16권6호
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• pp.727-741
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• 2019

A reinforced concrete water tank is a typical functional liquid storage structure and cracks are the greatest threat to the liquid storage structure. Tanks are readily cracked due to seismic activity, thereby leading to the leakage of the stored liquid and a loss of function. In order to study the effect of cracks on liquid storage tanks, self-healing and leakage tests for bending cracks and through cracks in the walls of a reinforced concrete water tank were conducted. Material performance tests were also performed. The self-healing performance of bending cracks in a lentic environment and through cracks in a lotic environment were tested, thereby the self-healing width of bending micro-cracks in the lentic environment in the short term were determined. The through cracks had the capacity for self-healing in the lotic environment was found. The leakage characteristics of the bending cracks and through cracks were tested with the actual water head on the crack. The effects on liquid leakage of the width of bending cracks, the depth of the compression zone, and the acting head were determined. The relationships between the leakage rate and time with the height of the water head were analyzed. Based on the tests, the relationships between the crack characteristics and self-healing as well as the leakage were obtained. Thereby the references for water tank structure design and grading earthquake damage were provided.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.930-931
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• 2011

As the upsurge in oil prices and global warming, Energy saving is needed to overall industry. If The head of Intake gate screen is high. The pumping process involves a loss of energy and results in high emissions of greenhouse gases. Therefore, blockages in intake gate should be free. Another advantage of cleaning is stabilizing pumping system. Because vibration and cavitation decreases when loss of head is low.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.100-105
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• 1994

In this paper, we discuss a method for design of an ambulance stretcher which call decrease blood pressure fluctuation caused by ambulance acceleration. Recently, a lot of stretchers which can isolate the vertical vibration to reduce body resonances (4-10 Hz) have been used during ambulance transport. However, we have found that blood pressure of a patient laying in the stretcher fluctuates when the ambulance accelerates or decelerates. Since the enforced change of the blood pressure may deteriorate the patent's condition, a stretcher to cancel head-to-foot acceleration and to decrease the blood pressure variation (BPV) is expected for safe transport. We propose a method to design a stretcher which is tilted according to an adequate angle to cancel head-to-foot acceleration by gravity when the ambulance accelerates or decelerates. A control method of the stretcher is constructed by means of simulation analysis using acceleration data measured during ambulance transport. It is confirmed that the active controlled stretcher proposed has good performance for the BPV reduction.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.471-474
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• 2001

Recently, due to demands of faster speed and extra features for the chip mounters, there has been ever-demanding needs for the basic technology. Until four or five years ago, chip mounters placing 0.3sec/chip were considered to be in the high speed category, but since then it has become a borderline for categorizing high speed machines capable of placing 0.1sec/chip. In this study, in order to analyze the vibration of head generated by the dynamic behavior of x-frame, FEM model is composed and modal analysis is performed to identify the dynamic characteristics of the structure. Those results are compared with the modal test in order to verify the model. In this paper, Several other factors, such as definition of dynamic accuracy, static accuracy and tolerance of the axis settling range, that might affect the dynamic behavior the head are discussed.

• 정보저장시스템학회논문집
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• 제1권1호
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• pp.23-28
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• 2005

This paper investigates the effects of disk thickness and Pemto slider on PES(position error signal) for high TPI(track per inch) drives above 150kTPI at early stage of their development. In order to reduce the disk flutter which becomes a dominant contributor to the TMR, the thicker disks with both 63 and 69mi1 have been used. Also, PES of a Pemto slider with thinner thickness than Pico slider has been estimated to decrease the conversion factor of disk motion in axial direction to head off-track motion. A frequency-domain PES estimation and prediction tool has been developed via measurement of disk flutter and HSA(head stack assembly) forced vibration. It has been validated by the measured PES in drive level. Based on the model and measurement of disk flutter, PES of a drive with the thicker disk and Pemto slider is predicted and their impact is investigated.

• 항공우주기술
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• 제10권1호
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• pp.122-128
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• 2011

액체로켓엔진용 산화제펌프의 수류시험을 상온에서 실시하였다. 수력성능시험 결과, 펌프의 양정 계수는 회전수가 커질수록 약간 감소하였고, 효율은 회전수가 커질수록 증가하였다. 흡입성능시험 결과, 유량비 92% 이하의 낮은 유량비에서 흡입성능이 떨어지는 것으로 나타났다. 또한, 시험 중 측정한 고주파 신호를 이용하여 펌프의 진동 특성을 분석하였다.

• Geomechanics and Engineering
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• 제16권6호
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• pp.609-618
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• 2018

A new mechanical model for predicting the vibration of a pipe pile embedded in longitudinally layered visco-elastic media with radial inhomogeneity is proposed by extending Novak's plain-strain model and complex stiffness method to consider viscous-type damping. The analytical solutions for the dynamic impedance, the velocity admittance and the reflected signal of wave velocity at the pile head are also derived and subsequently verified by comparison with existing solutions. An extensive parametric analysis is further performed to examine the effects of shear modulus, viscous damping coefficient, coefficient of disturbance degree, weakening or strengthening range of surrounding soil and longitudinal soft or hard interbedded layer on the velocity admittance and the reflected signal of wave velocity at the pile head. It is demonstrated that the proposed model and the obtained solutions provide extensive possibilities for practical application compared with previous related studies.