• Earthquakes and Structures
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• 제22권3호
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• pp.277-287
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• 2022

The ancient underground cities are a collection of self-supporting spaces that have been manually excavated in the soil or rock in the past. Because these structures have a very high cultural value due to their age, the study of their stability under the influence of natural hazards, such as earthquakes, is very important. In this research, while introducing the underground city of Ouyi Nushabad located in the center of Iran as one of the largest man-made underground cities of the old world, the analysis of dynamic stability is performed. For this purpose, the dynamic stress-displacement analysis has been performed through numerical modeling using the finite element software PLAXIS. At this stage, by simulating the Khorgo earthquake as one of the large-scale earthquakes that occurred in Iran, with a magnitude of 6.9 on the Richter scale, dynamic analysis by time history method has been performed on three selected sections of underground spaces. This study shows that the maximum amount of horizontal and vertical dynamic displacement is 12.9 cm and 17.7 cm, respectively, which was obtained in section 2. The comparison of the results shows that by increasing the cross-sectional area of the excavation, especially the distance between the roof and the floor, in addition to increasing the amount of horizontal and vertical dynamic displacement, the obtained maximum acceleration is intensified compared to the mapping acceleration applied to the model floor. Therefore, preventive actions should be taken to stabilize the excavations in order to prevent damage caused by a possible earthquake.

• 한국임상수의학회지
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• 제34권1호
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• pp.1-6
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• 2017

Heartworm disease (HWD) in dogs is a life-threatening mosquito-borne disease resulting in right-sided congestive heart failure and inflammatory pulmonary disease. Due to complications from adulticidal therapy with melarsomine, slow kill protocol either with preventive dose of ivermectin or combined with doxycycline has been proposed for an alternative adultcidal therapy in dogs with HWD. Therefore, this study evaluated the clinical outcome of adultcidal therapy in dogs with class II stage of HWD after treating either American Heartworm Society (AHS) or slow kill protocol for 10 months. Clinical outcome after therapy was evaluated by clinical, radiographic and echocardiographic examination along with hematology before (D0) and after therapy (D300). Although clinical signs associated with HWD were all resolved after therapy in both groups, the infection was not cleared out 67% of dogs treated by slow kill protocol at the end of therapy. Furthermore, pulmonary arterial flow of acceleration time to ejection time ratio (AT/ET) and the right pulmonary artery distensibility index (RPADI) have been firstly used for detecting pulmonary hypertension in this study group. The pulmonary hypertension was more common in dogs with mild clinical signs, although tricuspid and pulmonary regurgitation were not detectable in most dogs in this study. Our study findings suggested that the slow kill protocol might not be efficacious enough to clear out HWD in dogs and more attention on the presence of pulmonary hypertension might be necessary for effective management of HWD in dogs.

• 보존과학회지
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• 제38권4호
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• pp.277-288
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• 2022

'Eve 58-1', the subject of this study is a statue made of plaster and its structural stability was evaluated by utilizing the CAE program in order to prevent the risk of damage arising from impact and vibration that are generated during the packaging and transportation process given its material characteristics. CAE is an abbreviation for Computer Applied Engineering for realization by predicting changes at the time of application of virtual physical energy. It is applied by reflecting the physical property conditions and each boundary condition of plaster, and the digital images of the internal and external structure of the work were acquired through 3D scanning and CT analysis for interpretation by executing finite element modeling. When acceleration is applied to the work in the direction of its own weight, the left-right side and the front-rear side, it was possible to confirm a maximum displacement value of 15.24 mm in the head section of the front-rear side direction that has been tilted by approximately 27° from the Y-axis and the largest stress value of 12.46 MPa was at the left ankle section. The corresponding results confirmed that the left ankle section is the most vulnerable area and the section for which precautions need to be exercised and supplemented at the time of transporting the work by means of objective values.

• 한국철도학회논문집
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• 제16권4호
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• pp.298-304
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• 2013

본 논문은 구조물이 위치한 구간에 대하여 향후 최고시험속도 430km/h 차세대 고속철도 차량 및 고속열차 운영속도의 증속이 이루어지는 구간인 열차하중의 직접적인 영향이 예상되는 구조물 접속부를 대상으로 열차 증속에 따른 구조물의 동적영향을 시스템적으로 거동을 분석하였다. 그리고 열차하중에 의한 동적영향 검토를 수행하여 지중구조물과 인접 토공부의 거동특성을 분석하고 궤도노반의 성능평가 분석, 열차이동하중의 동적영향으로 인한 구조물의 안정성을 평가하기 위해 수치해석을 수행하였다. 분석결과 열차하중에 따른 동적영향은 적지만 연직가속도가 다소 크게 나타나는 것으로 분석되었다.

• 대한토목학회논문집
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• 제42권3호
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• pp.409-415
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• 2022

국내 연결로 가속차로 길이는 13 PS/ton 마력의 화물차를 기준으로 산정되어 연결로를 주행하는 대부분의 차량 성능에 비해 과다하게 산출되어있다. 이로 인해, 대부분의 운전자들은 고속도로로 진입하기 위해 가속차로 전 구간에서 본선으로의 무분별한 진입 경향으로 본선 교통흐름에 영향을 미쳐 이에 대한 개선이 필요하다. 양지, 수석, 용인, 오산 각각IC의 연결로 유입부에서 차량의 속도와 진입률 및 차량별 교통량을 조사하여 VISSIM 시뮬레이션 분석을 통해 교통흐름의 개선정도를 검토하였다. 조사결과 곡선부의 단순화와 본선 교통흐름의 인지가능 시점인 노즈부에서 부터 전체차량의 74.0 %가 연결로 규정속도 이상으로 주행하였고, 가속차로 길이대비 0.8 l 지점까지 88.6 %의 차량이 본선으로 진입하였다. 실측교통량을 기반으로 연결로 유입부를 0.265 l 지점까지 의도적으로 본선으로의 교통진입을 제한하여 시뮬레이션한 결과 본선과 연결로의 흐름을 평균속도 60.1 km/h에서 68.5 km/h까지 개선할 수 있었다.

• 한국정밀공학회지
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• 제18권6호
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• pp.121-126
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• 2001

Currently, potentiometric method has been employed to measure fuel amount for automobile. However, potentiometer could be malfunctioned or damaged due to the additives or dirt in fuel because a variable electric resistor is immersed in fuel. Therefore, a device employing strain sensor is designed and tested to verify the possibility as an alternative of the conventional fuel sender. Existing fuel tank has irregular cross section. Therefore, buoyancy is not increased linearly as fuel amount is increased. We design a floater that can compensate the irregular cross section of fuel tank and make buoyancy to increase linearly with increasing fuel amount. New fuel sender, comprising of strain gages on circular membrane, the above commented floater and the cover to prevent the disturbance due to sudden acceleration and deceleration, is designed and tested to replace current fuel sender. On the other hand, we are developing strain sensor that has strain gage deposited directly on the circular membrane with cantilever beam.

• Structural Engineering and Mechanics
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• 제32권4호
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• pp.517-529
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• 2009

A passive vibration mitigation architecture is proposed to damp transverse vibrations of guyed masts. The scheme is based on a number of pendula attached to the mast and tuned to the vibration modes to be controlled. This scheme differs from the well-known autoparametric pendulum absorber system. The equations of motion of the guyed mast with an arbitrary number of pendula are obtained. The leading bending behaviour of a typical truss mast is described by an equivalent beam model whereas the guys are conveniently modeled as equivalent transverse springs whose stiffness comprises the elastic and geometric stiffness. By assuming a mast with an inertially and elastically isotropic cross-section, a planar model of the guyed mast is investigated. The linearization of the equations of motion of the mast subject to a harmonic distributed force leads to the transfer functions of the structure without the dampers and with the dampers. The transfer functions allow to investigate the mitigation effects of the pendula. By employing one pendulum only, tuned to the frequency of the lowest mode, the effectiveness of the passive vibration potential in reducing the motion and acceleration of the top section of the mast is demonstrated.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.324-333
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• 2014

In this study, physiological status of locomotive engineers were measured through EEG, ECG, EDA, PPG and respiration signals from 6 subjects to evaluate their arousal status during train operating. Existence of tunnels and mechanical vibration of train using 3-axes acceleration sensors were recorded simultaneously and were correlated with operator's physiological status. As the result of the analyzed subjects' physiological signals, mean SCR was increased in the section where more body movement is required. The RR interval was decreased before and after train stop due to the higher level of mental tension. The intensity of beta wave of EEG was found to be higher before and after train stop and tunnel section due to the increased mental arousal and tension. Therefore, it is expected that the outcomes of the physiological signals explored in this study can be utilized as the quantitative assessment methods for the arousal status to be used for sleepiness prevention system for vehicles operators which can greatly contribute to public transportation system safety.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.341-345
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• 1990

This paper presents the three section sliding mode control algorithm based on hysteresis current control add indirect field oriented control method, and applies it to the position control of induction motor. The three section sliding trajectories are defined in such a way that the system responds following a max acceleration line, then a max speed line, and finally a max deceleration line. This control scheme solves the problem of robustness loss during the reaching phase that occurs in conventional VSC strategy, and ensures the stable sliding mode and robustness enhancement throughout an entire response. Also, the PID controller operating in parallel is adopted to eliminate the sliding mode's collapse phenomenon near the origin caused by steady state chattering phenomenon Digital simulation results confirm that the dynamic performance of the system is insensitive to parameter variations and disturbances.

• 한국소음진동공학회논문집
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• 제19권1호
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• pp.35-41
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• 2009

Through the multibody dynamic simulation, the analysis model of the modalohr freight car of the DMT freight car was developed. By using the developed analysis model, the running dynamic characteristics was inquired through the dynamic analysis about the modalohr freight car. As the running speed and the primary suspension were increased, the lateral and vertical vibration accelerations of the car-body and the bogie were also increased. In case of the lateral vibration acceleration of the car-body, however, review should be considered since it can be influenced by the nonlinear characteristic of the primary suspension. The lateral and vertical vibration of the car-body were generated at the frequency of $2{\sim}3\;Hz$ and $7{\sim}8\;Hz$. And the lateral and vertical vibration of the bogie were generated at the frequency of $25{\sim}35\;Hz$ at the low speed section, $40{\sim}50\;Hz$ at the high speed section.