• 반도체디스플레이기술학회지
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• 제20권1호
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• pp.25-31
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• 2021

The semiconductor and display equipment demands an ultra-fine precision of several nm to several ㎛, and the scale is getting smaller due to the explosive development. The manufacturing process equipment for such products with ultra-fine precision is very sensitive to ultra-small vibrations flowing from the floor, resulting in problems of production defects and yield degradation. The vibration criteria are a standard that regulates the vibration environment of the floor where such precision process equipment will be installed. The BBN vibration criteria defined the allowable vibration velocity level in the frequency domain with a flat and inclined line and presented a rating according to it. However, the actual vibration criteria have appeared with various magnitudes in the frequency domain according to the dynamic characteristics of individual equipment. In this study, the relationship between the relative motion of two major points in the equipment and the vibration magnitude of the floor is presented using the frequency response function of a simple 3-DOF model. It is describing the magnitudes according to the frequency of the floor vibration that guarantees the allowable relative motion and this can be used as the vibration criteria. In order to obtain the vibration criteria experimentally a method of extracting through a modal test was introduced and verified analytically. It provides vulnerable frequency and magnitude to floor vibration in consideration of the dynamic characteristics of individual equipment. And it is possible to know necessary to improve the dynamic characteristics of the equipment, and it can be used to check the vibration compatibility of the place where the equipment will be installed.

• Smart Structures and Systems
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• 제32권1호
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• pp.1-7
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• 2023

In modal analysis, the mode shape reflects the vibration characteristics of the structure, and thus it is widely performed for finite element model updating and structural health monitoring. Generally, the acceleration-based mode shape is suitable to express the characteristics of structures for the translational vibration; however, it is difficult to represent the rotational mode at boundary conditions. A tilt sensor and gyroscope capable of measuring rotational mode are used to analyze the overall behavior of the structure, but extracting its mode shape is the major challenge under the small vibration always. Herein, we conducted a feasibility study on a multi-mode shape estimating approach utilizing a single physical quantity signal. The basic concept of the proposed method is to receive multi-metric dynamic responses from two sensors and obtain mode shapes through bridge loading test with relatively large deformation. In addition, the linear transformation matrix for estimating two mode shapes is derived, and the mode shape based on the gyro sensor data is obtained by acceleration response using ambient vibration. Because the structure's behavior with respect to translational and rotational mode can be confirmed, the proposed method can obtain the total response of the structure considering boundary conditions. To verify the feasibility of the proposed method, we pre-measured dynamic data acquired from five accelerometers and five gyro sensors in a lab-scale test considering bridge structures, and obtained a linear transformation matrix for estimating the multi-mode shapes. In addition, the mode shapes for two physical quantities could be extracted by using only the acceleration data. Finally, the mode shapes estimated by the proposed method were compared with the mode shapes obtained from the two sensors. This study confirmed the applicability of the multi-mode shape estimation approach for accurate damage assessment using multi-dimensional mode shapes of bridge structures, and can be used to evaluate the behavior of structures under ambient vibration.

• 문화기술의 융합
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• 제9권4호
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• pp.537-542
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• 2023

최근 도심지 주변으로 집중되는 신축구조물 및 공동구 확장 등과 같은 인접굴착공사로 인해 운영중인 철도 구조물의 변형이 발생되고 있다. 그러나 대부분 구조물에 대한 구조검토 및 보수보강에 집중되고 있으며 궤도에 대한 검토는 부족한 실정이다. 특히 토공노반 상 자갈궤도의 경우 노반과 도상자갈이 강결된 구조가 아니므로, 미소한 수준의 변형으로도 도상자갈 이완현상이 발생할 수 있다. 이는 침목 지지조건이 불안정한 조건으로 유도될 수 있으므로 충분한 안전성을 확보해야한다. 또한 불안정한 지지조건으로 열차탈선의 위험이 매우 높은 궤도형식이다. 따라서 본 연구에서는 노반 변형에 따른 자갈궤도의 변형특성과 궤도지지성능의 상관관계를 실험 및 해석적으로 입증하고, 자갈궤도의 상태 및 궤도지지강성을 평가할 수 있는 평가기법을 제시하고자 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.258-262
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• 2007

Satellite launch vehicle is exposed to some dynamic environment during its flight. Particularly, the safety of launch vehicle structure is surely verified under vibration environment in low frequency range. Sine sweep test is generally performed to describe this low frequency vibration environment. Dynamic property of vibration fixture is considered to get the correct property of target object. This vibration fixture should really be an extension of the armature in the form of a very rigid structure that can transfer the required force at the required frequency. An optimum fixture would have its lower natural frequency about 50% higher than the highest required forcing frequency in order to avoid fixture resonances during the test. In this study, the vibration mode analysis considering the mass of target object to design the vibration fixture. And the modal test of vibration fixture is performed to conform the design.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.162-169
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• 2009

This paper describes a study on dynamic characteristics analysis and dynamic compliance evaluation of a 5-axis multi-tasking machine tool of ram-head type. Structural dynamics analysis and evaluation are necessary to machine tool design and development to secure good machine tool performance against tough and harsh machining conditions. In this study, natural frequencies and corresponding vibration modes of the machine tool structure were analyzed by using both F.E.M. modal analysis and impulse hammer test. Furthermore, dynamic compliance of the machine tool was analyzed by using F.E.M. and also measured by using a hydraulic exciter test. Both the theoretical analysis and experimental test results showed good agreement with each other.

• Nuclear Engineering and Technology
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• 제42권3호
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• pp.319-328
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• 2010

Bonded tendons have been used in reactor buildings at some operating nuclear power plants in Korea. Assessing prestress force on these bonded tendons has become an important pending problem in efforts to assure continued operation beyond their design life. The System Identification (SI) technique was thus developed to improve upon the existing indirect assessment technique for bonded tendons. As a first step, this study analyzed the sensitivity of the key parameters to prestress force, and then determined the optimal parameters for the SI technique. A total of six scaled post-tensioned concrete beams with bonded tendons were manufactured. In order to investigate the correlation of the natural frequency and the displacement to prestress force, an impact test, a Single Input Multiple Output (SIMO) sine sweep test, and a bending test using an optical fiber sensor and compact displacement transducer were carried out. These tests found that both the natural frequency and the displacement show a good correlation with prestress force and that both parameters are available for the SI technique to predict prestress force. However, displacements by the optical fiber sensor and compact displacement transducer were shown to be more sensitive than the natural frequency to prestress force. Such displacements are more useful than the natural frequency as an input parameter for the SI technique.

• 한국지진공학회논문집
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• 제25권3호
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• pp.93-102
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• 2021

The dynamic characterization of a three-story auxiliary building in a nuclear power plant (NPP) constructed with a monolithic reinforced concrete shear wall is investigated in this study. The shear wall is subjected to a joint-research, round-robin analysis organized by the Korea Atomic Energy Research Institute, South Korea, to predict seismic responses of that auxiliary building in NPP through a shake table test. Five different intensity measures of the base excitation are applied to the shaking table test to get the acceleration responses from the different building locations for one horizontal direction (front-back). Simultaneously to understand the global damage scenario of the structure, a frequency search test is conducted after each excitation. The primary motivation of this study is to develop a nonlinear numerical model considering the multi-layered shell element and compare it with the test result to validate through the modal parameter identification and floor responses. In addition, the acceleration amplification factor is evaluated to judge the dynamic behavior of the shear wall with the existing standard, thus providing theoretical support for engineering practice.

• 방송공학회논문지
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• 제23권3호
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• pp.351-360
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• 2018

인간 감정 인식은 컴퓨터 비전 및 인공 지능 영역에서 지속적인 관심을 받는 연구 주제이다. 본 논문에서는 wild 환경에서 이미지, 얼굴 특징점 및 음성신호로 구성된 multi-modal 신호를 기반으로 여러 신경망을 통해 인간의 감정을 분류하는 방법을 제안한다. 제안 방법은 다음과 같은 특징을 갖는다. 첫째, multi task learning과 비디오의 시공간 특성을 이용한 준 감독 학습을 사용함으로써 영상 기반 네트워크의 학습 성능을 크게 향상시켰다. 둘째, 얼굴의 1 차원 랜드 마크 정보를 2 차원 영상으로 변환하는 모델을 새로 제안하였고, 이를 바탕으로 한 CNN-LSTM 네트워크를 제안하여 감정 인식을 향상시켰다. 셋째, 특정 감정에 오디오 신호가 매우 효과적이라는 관측을 기반으로 특정 감정에 robust한 오디오 심층 학습 메커니즘을 제안한다. 마지막으로 소위 적응적 감정 융합 (emotion adaptive fusion)을 적용하여 여러 네트워크의 시너지 효과를 극대화한다. 제안 네트워크는 기존의 지도 학습과 반 지도학습 네트워크를 적절히 융합하여 감정 분류 성능을 향상시켰다. EmotiW2017 대회에서 주어진 테스트 셋에 대한 5번째 시도에서, 제안 방법은 57.12 %의 분류 정확도를 달성하였다.

• Smart Structures and Systems
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• 제11권5호
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• pp.453-476
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• 2013

DuraMote is a remote sensing system developed for the "NIST TIP project: next generation SCADA for prevention and mitigation of water system infrastructure disaster". It is designed for supervisory control and data acquisition (SCADA) of ruptures in water pipes. Micro-electro mechanical (MEMS) accelerometers, which record the vibration of the pipe wall, are used detect the ruptures. However, the performance of Duramote cannot be verified directly on a water distribution system because it lacks an acceptable recordable level of ambient vibration. Instead, a long-span cable-stayed bridge is an ideal test-bed to validate the accuracy, the reliability, and the robustness of DuraMote because the bridge has an acceptable level of ambient vibration. The acceleration data recorded on the bridge were used to identify the modal properties of the structure and to verify the performance of DuraMote. During the test period, the bridge was subjected to heavy rain, wind, and a typhoon but the system demonstrates its robustness and durability.

• 한국소음진동공학회논문집
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• 제21권12호
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• pp.1192-1198
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• 2011

Design routines of a torsional spring-viscous damper for a 1800 kW four cycle diesel engine-generator system are described. Modal techniques for system normalization and optimal equations for damper design are used to obtain proper design parameters of the damper. A prototype damper is manufactured according to the described design process and its two design parameters, stiffness and damping, are evaluated experimentally by torsional actuator test and free decay test. Experimentally obtained values of stiffness and damping coefficients showed good agreements with the designed values of the prototype damper.