• Membrane Journal
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• v.9 no.3
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• pp.141-150
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• 1999

A novel permeation apparatus was developed which could make the on-line measurements of both flux transient and permeate composition in gas permeation. The measurement by using the per¬meation apparatus was based on the continuous-flow technique. The transient measurement allowed the simultaneous determinations of permeation characteristics, such as, permeability, diffusion and solubility coefficients, and activation energies only with one experiment. The apparatus performance was illustrated by conducting the permeation of pure gases through two glassy polyimides and a rubbery poly (dimethyl¬siloxane) membranes, respectively. A comparison of the permeation characteristics determined from the flux transients was made with the literature values for verifying the confidence and accuracy of the measurement. Also, the analysis of the permeation transients obtained was carried out for the close investigation of the permeation behaviors of gases through membrane.

• Journal of ILASS-Korea
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• v.27 no.4
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• pp.181-187
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• 2022

For carbon neutrality, direct-injection hydrogen engines are attracting attention as a future power source. It is essential to estimate the transient injection rate of hydrogen for the optimization of hydrogen injection in direct injection engines. However, conventional injection rate measurement techniques for liquid fuels based on the injection-induced fuel pressure change in a test section are difficult to be applied to gaseous fuels due to the compressibility of the gas and the sealing issue of the components. In this study, a momentum flux measurement technique is introduced to obtain the transient injection rate of gaseous fuels using a force sensor. The injection rate calculation models associated with the momentum flux measurement technique are presented first. Then, the volumetric injection rates are estimated based on the momentum flux data and the calculation models and compared with those measured by a volumetric flow rate meter. The results showed that the momentum flux measurement can detect the injection start and end timings and the transient and steady regimes of the fuel injection. However, the estimated volumetric injection rates showed a large difference from the measured injection rates. An alternative method is suggested that corrects the estimated injection rate results based on the measured mean volumetric flow rates.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.4
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• pp.376-380
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• 2008

This paper deals with a performance analysis of real-time control systems, which engages DMR(dual modular redundancy) to detect transient errors and checkpointing technique to tolerate transient errors. Transient errors are caused by transient faults and the most significant type of errors in reliable computer systems. Transient faults are assumed to occur according to a Poisson process and to be detected by a dual modular redundant structure. In addition, an equidistant checkpointing strategy is considered. The probability of the successful task completion in a real-time control system where periodic checkpointing operations are performed during the execution of a real-time control task is derived. Numerical examples show how checkpoiniting scheme influences the probability of task completion. In addition, the result of the analysis is compared with the simulation result.

• Journal of Electrical Engineering and Technology
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• v.3 no.4
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• pp.468-475
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• 2008

This paper presents a method for estimating the transient stability status of the power system using radial basis function(RBF) neural network with a fast hybrid training approach. A normalized transient energy margin(${\Delta}V_n$) has been obtained by the potential energy boundary surface(PEBS) method along with a time-domain simulation technique, and is used as an output of the RBF neural network. The RBF neural network is then trained to map the operating conditions of the power system to the ${\Delta}V_n$, which provides a measure of the transient stability of the power system. The proposed approach has been successfully applied to the 10-machine 39-bus New England test system, and the results are given.

• International Journal of Aeronautical and Space Sciences
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• v.1 no.2
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• pp.22-29
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• 2000

A method to simulate the gas turbine transient behavior is developed. The basic principles of the method and main input data required are described. Calculation results are presented in terms of whole operating regime of the engine. The influence of initial parameters such as starting engine power, moment of inertia of the rotor, fuel schedule on performance characteristics of gas turbine during transient operation is shown. In addition, the effect of bleeding air on transient behavior is also considered. For validation of the developed computer code, a comparative analysis with experimental data obtained from a heavy duty gas turbine is made. Calculation results agree well with the experimental data for the range of operating regime studied and proved applicability of the developed technique to initial design stage of control system.

• Biomedical Science Letters
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• v.11 no.2
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• pp.201-209
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• 2005

This study aimed to investigate the cerebroprotective effect of nociceptin on transient focal cerebral ischemia in Sprague-Dawley rats by determining the changes in regional cerebral blood flow (rCBF) and the infarct size. Right middle cerebral artery (MCA) was occluded for 2 hours, and thereafter was followed by reperfusion by an intraluminal monofilament technique. An open cranial window was made on the right parietal bone for determination of continuous changes in rCBF by laser-Doppler flowmetry. The infarct size was morphometrically determined using the 2,3,5-triphenyltetrazolium chloride technique. In normal rats, nociceptin ($0.01\~100\;nmol/kg$, Lv.) increased rCBF and decreased cerebral arterial resistance in a dose-dependent manner. Systemic arterial blood pressure was little affected by nociceptin at the doses of 0.01 and 0.1nmol/kg, but dose-dependently reduced at the doses of 1 nmol/kg or more. In transient cerebral ischemic rats, nociceptin ($0.01\~0.1$ nmol/kg, i.p.) significantly attenuated the postischemic cerebral hyperemia, and progressively increased rCBF. The improving effect of nociceptin on the postischemic rCBF response was markedly blocked by pretreatment with $[Nphe^1]nociceptin(1-13)NH_2$ (1 nmol/kg, i.p.), a selective nociceptin receptor antagonist, but not by naloxone ($3{\mu}mol/kg$, i.p.), a selective opioid receptor antagonist. The cerebral infarct size was significantly reduced by nociceptin ($0.01\~0.1$ nmol/kg) administered i.p. 5 min after MCA occlusion in transient cerebral ischemia of 2-hour MCA occlusion and 22-hour reperfusiion. It is suggested that nociceptin improves the postischemic cerebral hemodynamics and thereby has a cerebroprotective effect in transient focal cerebral ischemia.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.31.4-31
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• 2001

This paper deals with a control technique of eliminating the transient vibration of a waist axis of an articulated robot. This technique is based on a model-based control in order to establish the damping effect on the mechanical part. The control model is composed of reduced-order electrical and mechanical parts. This model estimates a load speed converted to the motor shaft. The difference between the estimated load speed and the motor speed is calculated dynamically and is added to the velocity command to suppress the transient vibration of a waist axis of the arm. This control model is easily obtained from design or experimental data and can be easily integrated into a DSP. This control technique is applied to a waist axis of an articulated robot composed of a harmonic drive ...

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1341-1346
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• 2009

In this paper, the technique to reinforce the durability performance of structure using the sensitivity information for the frame structure is applied. The fatigue life calculation for the frame structure is performed from the quasi-static and transient analysis and the characteristics of two methods are compared for the fatigue analysis. Then the reinforcement technique is applied. First, some design variables related to the locations of fatigue failure is selected. Then sensitivities of fatigue life at fracture points with respect to the variation of design variables are calculated and the vector composed of gaps between the target life and initial life cycles is calculated. If the number of fatigue fracture points is same as the number of design variables, the variations of the design variables are calculated from the linear algebraic equation. If not, the variations of the design variables are calculated from the optimization formulation with the constraints.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.50 no.3
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• pp.101-108
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• 2001

Frequency is an important operating parameter of a power system. Electric power systems sustain transient frequency swings whenever the balance between generation and load does not no longer hold. To cope with this constraints, it requires an accurate and high speedy frequency deviation estimation technique and suitable adjustment to obtain the Power system energy balance. This paper describes a digital signal processing technique for measuring the operating frequency of a power system. The fundamental frequency component of 3-phase signal is first extracted by using an algorithm based on FIR filter. The rate change of the phase angle is used for estimation. To confirm the validity of the proposed algorithm, the simulation studies carried out on a typical 154KV double T/L system by using EMTP software. Some test results are presented in the paper.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.258-270
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• 2020

A new task of using the Jacobian-Free-Newton-Krylov (JFNK) method for the PWR core transient simulations involving neutronics, thermal hydraulics and mechanics is conducted. For the transient scenario of PWR, normally the Picard iteration of the coupled coarse-mesh nodal equations and parallel channel TH equations is performed to get the transient solution. In order to solve the coupled equations faster and more stable, the Newton Krylov (NK) method based on the explicit matrix was studied. However, the NK method is hard to be extended to the cases with more physics phenomenon coupled, thus the JFNK based iteration scheme is developed for the nodal method and parallel-channel TH method. The local gap conductance is sensitive to the gap width and will influence the temperature distribution in the fuel rod significantly. To further consider the local gap conductance during the transient scenario, a 1D mechanics model is coupled into the JFNK scheme to account for the fuel thermal expansion effect. To improve the efficiency, the physics-based precondition and scaling technique are developed for the JFNK iteration. Numerical tests show good convergence behavior of the iterations and demonstrate the influence of the fuel thermal expansion effect during the rod ejection problems.