• Journal of Power System Engineering
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• v.3 no.4
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• pp.57-62
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• 1999

The microaccelerometer using a tunnelling current effect concept has the potential of high performance, although it requires slightly complex signal-processing circuit for servo-system. The paddle of micro accelerometer is pulled to have the gap width of about 2nm which almost allows the flow tunnelling current. This paper demonstrates at capacitor of microaccelerometer the use of the coupled thermo-electric analysis for voltage, current, heat flux and Joule heating then tunnelling current flows. Two electrodes are applied to the microaccelerometer producing a unform difference of temperature gradient and electric potential between the paddle and the substrate.

• Structural Engineering and Mechanics
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• v.52 no.6
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• pp.1257-1271
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• 2014

The hydraulic deterioration of the drainage system in tunnel linings is one of the main factors governing long-term lining-ground interactions during the lifetime of tunnels. Thus, in the design procedure of a tunnel below the groundwater table, the possible detrimental effects associated with the hydraulic deterioration should be addressed. Hydraulic deterioration in double-lined tunnels can occur because of reasons such as clogging of the drainage layer and drain-pipe blockings. In this study, the coupled mechanical and hydraulic interactions between linings due to drain-pipe blockings are investigated using the finite-element method. A double-lined structural model incorporating hydraulic behavior is developed to represent the coupled structural and hydraulic behavior between the linings and drainage system. It is found that hydraulic deterioration hinders flow into the tunnel, causing asymmetric development of pore-water pressure and consequent detrimental effects to the secondary lining.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.494-498
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• 1996

Three fuzzy input space partitoining methods, which are grid, tree, and scatter method, are mainly used until now. These partition methods represent good performance in the modeling of the linear system and nonlinear system with independent modeling variables. But in the case of the nonlinear system with the coupled modeling variables, there should be many fuzzy rules for acquiring the exact fuzzy model. In this paper, it shows that the fuzzy model is acquired using transformed modeling vector by linear transformation of the modeling vector.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.106-113
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• 2009

A 6-DOF precision stage was developed based on parallel kinematics structure with flexure hinges to eliminate backlash, stick-slip and friction and to minimize parasitic motion coupled with motions in the other-axis directions. For the stage, lever linkage mechanism was devised to reduce the height of system for the enhancement of horizontal stiffness. Frequency response comparison between experimental results and mathematical model extracted from dynamics of the stage was performed to identify the system parameters such as spring constants and damping coefficients of actuation modules, which cannot be calculated accurately by analytic methods owing to their complicated structures. This newly developed precision stage and its identified model will be very useful for precision positioning and control because of its high accuracy and non-coupled movement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1648-1653
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• 2000

Theoretical analysis of noise reduction by a membrane-duct system is presented. When acoustic waves propagate in the membrane-duct, the part of membrane is also excited and its motion is coupled with interior medium. For an infinite plane membrane-duct system, a simple coupled governing equation is derived and solved. One of the characteristics of dispersion relation is that evanescent waves occur below critical frequency. Attaching damping materials to the membrane may improve the absorption efficiency of acoustic energy. The results show that the membrane-duct system can be applied to diminish and absorb low frequency noise in duct instead of passive muffler, such as simple expansion chamber or absorption material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.220-226
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• 2002

A general solution method is presented to obtain the unbalance response orbit from the finite element based equations of motion of a gear-coupled two-shaft rotor-bearing system. Particularly, are proposed the analytical solutions of major and minor axis radii of the orbit. The method has been applied to analyze the unbalance response of a 800 refrigeration-ton turbo-chiller rotor-bearing system, having a bull-pinion speed increasing gear. The bumps of unbalance responses have been observed at the first torsional natural frequency due to the coupling of lateral and torsional dynamics by the gear meshing. Further, the proposed analytical solutions have been validated with results obtained by a full numerical approach.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.499-506
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• 2003

The design cycle associated with large engineering systems requires an initial decomposition of the complex system into design processes which are coupled through the transference of output data. Some of these design processes may be grouped into iterative subcycles. In analyzing or optimizing such a coupled system, it is essential to determine the best order of the processes within these subcycles to reduce design cycle time and cost. This is accomplished by decomposing large multidisciplinary problems into several sub design structure matrices (DSMs) and processing them in parallel This paper proposes a new method for parallel decomposition of multidisciplinary problems to improve design efficiency by using the multi-objective genetic algorithm and two sample test cases are presented to show the effect of the suggested decomposition method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.662-668
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• 1997

Since the structural impedance is much greater than that of medium in the most cases, we often assume that the structure is rigid and that the structural vibration is independent of medium, i.e. we usually calculate the vibration of the structure first, and then obtain the radiation sound from it. This assumption is no longer satisfied when the structural stiffness is small or the fluid impedance is comparable to it. This situation often happens in underwater acoustics. Although many researchers have studied about structural-fluid coupling, we have difficulties in solving the problem analytically. Therefore the numerical method using powerful computation leads us to obtain the various coupling problem. To understand the physical coupling phenomena, visualization of sound field by a geometrically simple system(plate-cavity coupled system) is performed experimentally. Acoustic holographic method is used to estimate sound field.

• International Journal of Aerospace System Engineering
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• v.6 no.2
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• pp.1-10
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• 2019

In this paper, the probabilistic free vibration analysis of a geometrically coupled cantilever wing with uncertain material properties is carried out using stochastic finite element (SFEM) based on first order perturbation technique. Here, both stiffness and damping of the system are considered as random parameters. The bending and torsional rigidities are assumed as spatially varying second order Gaussian random fields and represented by Karhunen Loeve (K-L) expansion. Here, the expected value, standard deviation, and probability distribution of random natural frequencies and damping ratios are computed. The results obtained from the present approach are also compared with Monte Carlo simulations (MCS). The results show that the uncertain bending rigidity has more influence on the damping ratio and frequency of modes 1 and 3 while uncertain torsional rigidity has more influence on the damping ratio and frequency of modes 2 and 3.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2572-2580
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• 2020

Emerging gamma ray detection applications that utilize neutron-based interrogation result in the prompt emission of high-energy (>2 MeV) gamma-rays. Rapid imaging is enabled by scintillators that possess high density, high atomic number, and excellent energy resolution. In this paper, we evaluate the bright (50,000 photons/MeV) oxide scintillator, cerium-doped Gd₂Al₂Ga₃O₁₂ (GAGG(Ce)). A silicon photomultiplier (SiPM) array is coupled to a GAGG(Ce) scintillator array (12 × 12 pixels) and integrated into a coded-aperture based gamma-ray imaging system. A resistor-based symmetric charge division circuit was used reduce the multiplicity of the analog outputs from 144 to 4. The developed system exhibits 9.1%, 8.3%, and 8.0% FWHM energy resolutions at 511 keV, 662 keV, and 1173.2 keV, respectively. In addition, a pixel-identification resolution of 602 ㎛ FWHM was obtained from the GAGG(Ce) scintillator array.