Many piping systems installed in the power plant are directly related to the safety and operation of the plant. Various dampers have been applied to the piping system to reduce the damage caused by earthquakes. In order to reduce the vibration of the piping system, this study developed a steel coil damper (SCD) with a straightforward structure but excellent damping performance. SCD reduces the vibration of the objective structure by hysteretic damping. The new SCD damper can be applied to high-temperature environments since it consists of steel members. The paper introduces a design method for the elastoplastic coil spring, which is the critical element of SCD. The practical applicability of the design procedure was validated by comparing the nonlinear force-displacement curves calculated by design equations with the results obtained from nonlinear finite element analysis and repeated loading test. It was found that the designed SCD’s have a damping ratio higher than 25%. In addition, this study performed a set of seismic tests using a shaking table with an existing piping system to verify the vibration control capacity on the piping system by SCD. Test results prove that the SCD can effectively control the displacement vibration of the piping system up to 80%.

기계 장비의 진동 데이터는 필연적으로 노이즈를 포함하고 있다. 이러한 노이즈는 기계 장비의 유지보수를 진행하는데 악영향 을 끼친다. 그에 따라 데이터의 노이즈를 얼마나 효과적으로 제거해주냐에 따라 학습 모델의 성능을 좌우한다. 본 논문에서는 시계열 데 이터를 전처리 함에 있어 특성추출 과정을 포함하지 않는 Denoising Auto Encoder 기법을 활용하여 데이터의 노이즈를 제거했다. 또한 기계 신호 처리에 널리 사용되는 Wavelet Transform과 성능 비교를 진행했다. 성능비교는 고장 탐지율을 계산하여 진행했으며 보다 정확한 비교 를 위해 분류 성능 평가기준 중 하나인 F-1 Score를 계산하여 성능 비교를 진행했다. 고장을 탐지하는 과정에서는 One-Class SVM 기법을 활용하여 고장 데이터를 탐지했다. 성능 비교 결과 고장 진단율과 오차율 측면에서 Denoising Auto Encoder 기법이 Wavelet Transform 기법 에 비해 보다 좋은 성능을 나타냈다.

부공력감쇠는 풍직각방향의 와류공진을 예측하는데 있어서 매우 중요한 요소이다. 부공력감쇠는 진동유발하중 또는 피드백 하중을 구성하는 주요인자로 와류진동이 급격히 발현되는 현상을 설명하는 도구이기도 하다. 본 연구에서는 공력감쇠의 수학적 모델 을 제시하고 와류유발하중모델과 함께 와류진동을 예측하는 프러세스를 제안한다. 직사각형단면에 대한 공기력진동실험을 수행하여, 계측된 가속도로부터 공력감쇠와 와류유발하중을 추정하고 이에 기반하여 공력감쇠모델과 와류유발하중모델을 구축하는 과정을 다룬 다. 최종적으로 공력감쇠모델과 와류유발하중 모델에 대한 재해석을 통하여 가속도응답을 구하고 계측된 가속도와 비교하여 모델의 진동예측성능을 평가한다. 본 연구에서 제안된 와류하중모델의 진동예측성능을 평가한 결과 안정적이며, 신뢰도가 높은 와류진동예측 이 가능함을 알 수 있었다.

This study indirectly measures the vibration value corresponding to the abnormal vibration generated by the small engine for light aircraft to which the dual carburetor is applied by the pressure difference from each carburetor. It relates to a system for outputting a warning to a pilot, comprising two pressure gauges for measuring the pressure from each carburetor and a warning signal output unit for outputting a warning signal corresponding to the pressure difference measured by the two pressure gauges do.

PURPOSES : The purpose of this study is to identify the dynamic behavior of a cement concrete paving machine (paver) by measuring its response using accelerometers. This is because the dynamic behavior of pavers affects the quality of data from various applications of IoT sensors, such as laser, ultrasonic, optical sensors and so on. Therefore, it is believed that the understanding of dynamic behaviors can contribute to the effective use of various IoT sensors for the acquisition of real-time quality control data in pavement construction. METHODS : Dynamic signals are obtained using accelerometer sensors to identify the dynamic characteristics of paving machines. The main parameters for acquiring dynamic signals are the status of the machine’s operating or standby conditions, and available locations for attaching various IoT sensors. Time domain data are logged at a particular sampling speed using a low-pass filter, subsequently, they are converted to digital data, which are analyzed on three rectangular axes. In addition frequency analysis is conducted on the measured data for identifying the peak frequencies, via FFT (Fast-Fourier-Transform) using MATLAB. RESULTS : The magnitude of the x-directional vibration is higher than that of any other direction under the paver’s operating or standby condition. However, signals from the smoother beam show that the z-directional vibration is more significant in the operating status. It means that the primary vibration depends on the location. Furthermore, the peak frequencies are quite various depending on the status of a paver and its sensing location. CONCLUSIONS : The magnitude of machine vibration and peak frequencies at each status or location are identified from time- and frequency-domain data. When using IoT sensors for quality control or monitoring pavements in construction, the dynamic characteristics of a paver should be considered to mitigate the interference of signals from the paver body or its elements.

최근 유기농산물에 대한 선호가 증가하고 있다. 유기농산물 생산에 있어 물리적 제초는 필수적이다. 하지만, 국내 밭 제초작업 기계화율은 60% 미만으로 낮으며, 농촌 인구의 고령화·여성화로 소형 제초기의 개발이 필요하다. 또한, 제초기의 경우 사용자가 반복적 진동에 노출되기 때문에 이를 절감할 수 있는 노력이 필요하나, 이에 대한 연구는 미흡한 실정이다. 따라서, 본 연구에서는 여성·고령 농업인도 사용하기 편리한 전동 배부식 중경제초기를 개발하는 데 있어 수평 회전식 원판에 부착된 제초날의 형상(원형, 삼각형, 일자형) 및 폭(15, 20, 25mm)에 따른 제초성능 및 ISO5349-1에 따라 손에 전달되는 진동을 분석하였다. 제초율은 원형 제초날에서 90.4~96.4%로 가장 높게 나타났으며, 진동 또한 원형 제초날을 사용하였을 때 사용자의 10%가 수지백증이 발병하는데 걸리는 시간이 20년 내외로 삼각형 및 일자형 제초날을 사용했을 때 보다 200% 가량 증가하는 것으로 나타났다. 따라서, 원형 제초날을 사용하였을 때 진동을 감소시킬 수 있으며, 불필요한 반력을 줄여 높은 제초효과를 볼 수 있을 것으로 판단된다.

Friction damping is often used as a vibration isolation medium to protect large objects from vibration. In this paper, it is modeled and analyzed a basis-excited nonlinear vibration system with friction damping using the SCPA method, which is one of the averaging methods. The displacement transmissibility and the stability of the steady state response were analyzed seperately for the linear and the non-linear spring systems. The critical frequency at which the relative motion starts was obtained as a function of the friction ratio, and the characteristics of the displacement transmissibility according to the change of the design parameters were investigated. In the case of the nonlinear spring system, the displacement transmissibilities were divided into three types and the motion characteristics were considered. In particular, there was a peculiarity that the displacement transmissibilty curve was separated at specific parameter values.

Speaker is the converting device which change electric energy to sound energy, and we can easily see the speaker. They are widely used to home and car audio unit, home and industrial alarm device. Sometimes, the alarm sounds cause the environmental noise. Therefore it is important to design the appropriate speaker according to the installed device and position. In order to study the vibration and sound characteristics, the curvature of the cone paper is changed. Finite element method is used to compute the vibration characteristics and mode. Indoor and Vehicle teats are carried out to investigate the non-linear characteristics and the sound characteristics for some car speakers.

As the frequency of seismic disasters in Korea has increased rapidly since 2016, interest in systematic maintenance and crisis response technologies for structures has been increasing. A data-based leading management system of Lifeline facilities is important for rapid disaster response. In particular, the water supply network, one of the major Lifeline facilities, must be operated by a systematic maintenance and emergency response system for stable water supply. As one of the methods for this, the importance of the structural health monitoring(SHM) technology has emerged as the recent continuous development of sensor and signal processing technology. Among the various types of SHM, because all machines generate vibration, research and application on the efficiency of a vibration-based SHM are expanding. This paper reviews a vibration-based pipeline SHM system for seismic disaster response of water supply pipelines including types of vibration sensors, the current status of vibration signal processing technology and domestic major research on structural pipeline health monitoring, additionally with application plan for existing pipeline operation system.

In this study, algorithms for analyzing the torsion of buildings under earthquake excitation are developed. The algorithm and formulations to account for the torsional angle are verified by analyzing the seismic acceleration time history data. The method was applied to the reference buildings to examine their operation and usability. The reference application demonstrated that the noise-canceling scheme successfully overcame various obstacles in the field measurements. The developed method is expected to be used as a tool to support a loss assessment system for determining the direction and priority of disaster response in the event of an earthquake.

Nuclear power plants in Korea were designed and evaluated based on the NRC's Regulatory Guide 1.60, a design response spectrum for nuclear power plants. However, it can be seen that the seismic motion characteristics are different when analyzing the Gyeongju earthquake and the Pohang earthquake that has recently occurred in Korea. Compared to the design response spectrum, seismic motion characteristics in Korea have a larger spectral acceleration in the high-frequency region. Therefore, in the case of equipment with a high natural frequency installed in a nuclear power plant, seismic performance may be reduced by reflecting the characteristics of domestic seismic motions. The failure modes of the equipment are typically structural failure and functional failure, with an anchorage failure being a representative type of structural failure. In this study, comparative analyses were performed to decide whether to consider the inelastic behavior of the anchorage or not. As a result, it was confirmed that the seismic performance of the anchorages could be increased by considering the inelastic behavior of an anchorage.

In this study, we proposed a method to measure and analyze the vibration problem in cargo pipes during the sea trial for 80K LPG vessel. Pipe vibration was identified as resonance with the propeller 1st order component, which is one of the main excitation forces in the normal continuous rating (NCR). In order to avoid resonance in the NCR, a reinforcement method was established through finite element method (FEM) analysis. In the future, the advance application of cargo pipe reinforcement is expected to be useful for reducing the vibration of the cargo pipes in ships whose order and specification are similar to those of the vessel used in this study.

이 논문은 드럼 세트를 구성하는 악기들 중 스네어 드럼에 사용되는 진동제어장치의 크기와 질량의 변화에 따라 음량과 음색 및 엔벨로프가 어떻게 변화되는지에 대해 연구하였다. 스네어 드럼을 사용하여 연주하는 드럼 연주자 및 음향 엔지니어들에게 진동제어장치의 변화에 따라 도출되는 소리의 특성을 제공하여 표현하고 싶은 스네어 음색을 구사할 수 있는 정보를 제공하는 목적을 가지고 있으며 스네어 드럼의 음색을 구사하는 능력이 향상된다는 것은 음악의 장르와 스타일에 따라 연주자 및 음향 엔지니어의 표현 능력이 향상될 수 있는 긍정적 영향을 끼칠 수 있다. 실험 결과 진동제어장치를 사용하여 면적과 질량의 변화를 준 환경에서 라우드 니스의 변화는 발생하지 않았으며, 주파수 응답의 변화는 미미한 수준이었고, 엔벨로프의 길 이에서는 큰 변화가 발생하였다. 실험과정에서 실제로 듣는 청감상의 스네어 드럼 음색 변화는 매우 크게 나타났으며 특히 질량보다는 면적의 변화에 따른 실험환경에서 큰 음색 변화가 있었다. 결과적으로 진동제어장치는 실질적으로 엔벨로프에만 관여하며, 스네어 드럼은 엔벨 로프의 길이가 짧아 엔벨로프의 앞부분에서 발생하는 음색이 더 중요하다는 일부 인식과 달 리, 엔벨로프의 뒷부분도 인간이 지각하는 음색에 큰 영향을 준다는 연구들이 도출되었다.

A theoretical model has been studied to describe the sound radiation analysis for structure vibration noise of tire under the action of random moving line forces. When a tire is analyzed, it had been modeled as curved beams with distributed springs and dashpots that represent the radial, tangential stiffness and damping of tire, respectively. The reaction due to fluid loading on the vibratory response of the curved beam is taken into account. The curved beam is assumed to occupy the plane y=0 and to be axially infinite. The curved beam material and elastic foundation are assumed to be lossless Bernoulli-Euler beam theory including a tension force(T), damping coefficient (C) and stiffness of foundation(κ2) will be employed. The expression for sound power is integrated numerically and the results examined as a function of Mach number(M), wave-number ratio(γ) and stiffness factor(ψ). The experimental investigation for structure vibration noise of vehicle tire under the action of random moving line forces has been made. Based on the STSF(Spatial Transformation of Sound Field) techniques, the sound power and sound radiation are measured. Results strongly suggest that operation condition in the tire material properties and design factors of the tire govern the sound power and sound radiation characteristics.