• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.3
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• pp.111-119
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• 2010

In this paper the numerical methods of finding out the optimal position of optical phase conjugator (OPC) and the optimal fiber dispersion are proposed, which are able to effectively compensate overall channels in $16{\times}40$ Gbps WDM system. And the compensation characteristics in the system with two induced optimal parameters are compared with those in the system with the currently used mid-span spectral inversion (MSSI) in order to confirm the availability of the proposed methods. It is confirmed that the reception performances are largely improved in the system with the induced optimal parameters than in the system with MSSI through the analyzing the eye opening penalty (EOP) and bit error rate (BER) characteristics. It is also confirmed that two optimal parameters depend on each other, but are less related with the procedural problem about the first optimal value among these parameters.

• Journal of Power Electronics
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• v.19 no.4
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• pp.1054-1067
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• 2019

This paper systematically investigates the influence of device parameters spread on the current distribution of paralleled silicon carbide (SiC) MOSFETs. First, a variation coefficient is introduced and used as the evaluating norm for the parameters spread. Then a sample of 30 SiC MOSFET devices from the same batch of a well-known company is selected and tested under the same conditions as those on datasheet. It is found that there is big difference among parameters spread. Furthermore, comprehensive theoretical and simulation analyses are carried out to study the sensitivity of the current imbalance to variations of the device parameters. Based on the concept of the control variable method, the influence of each device parameter on the steady-state and transient current distributions of paralleled SiC MOSFETs are verified separately by experiments. Finally, some screening suggestions of devices or chips before parallel-connection are provided in terms of different applications and different driver configurations.

• Smart Structures and Systems
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• v.32 no.6
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• pp.383-391
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• 2023

Energy harvesting in trams may become a prevalent source of passive energy generation due to the high density of vibrational energy, and this may help power structural health monitoring systems for the trams. This paper presents a broadband vibrational energy harvesting device design that utilizes a varied frequency from a tram vehicle using a 2 DOF vibrational system combined with electromagnetic energy conversion. This paper will demonstrate stepwise optimization processes to determine mechanical parameters for frequency tuning to adjust to the trams' operational conditions, and electromagnetic parameters for the whole system design to maximize power output. The initial optimization will determine 5 important design parameters in a 2 DOF vibrational system, namely the masses (m₁, m₂ (and spring constants (k₁, k₂, k₃). The second step will use these parameters as initial guesses for the second optimization which will maintain the ratios of these parameters and present electrical parameters to maximize the power output from this system. The obtained values indicated a successful demonstration of design optimization as the average power generated increased from 1.475 mW to 17.44 mW (around 12 times).

• Structural Engineering and Mechanics
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• v.16 no.3
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• pp.327-340
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• 2003

Variations in system parameters due to uncertainties of parameters may result in system performance deterioration and create system internal stability problems. Uncertainties in structural modeling of structures are often considered to ensure that the control system is robust with respect to response errors. So the uncertain concept plays an important role in the analysis and design of the engineering structures. In this paper, the active control of the intelligent structures with the uncertainties is studied and a new method for analyzing the robustness of systems with the uncertainties is presented. Firstly, the system with uncertain parameters is considered as the perturbation of the system with deterministic parameters. Secondly, the feedback control law is designed on the basis of deterministic system. Thirdly, perturbation analysis and robustness analysis of intelligent structures with uncertainties are discussed when the feedback control law is applied to the original system and perturbed system. Combining the convex model of uncertainties with the finite element method, the analysis theory of the robustness of intelligent structures with the uncertainties can be developed. The description and computation of the robustness of intelligent structures with uncertain parameters is obtained. Finally, a numerical example of the application of the present method is given to show the validity of the method.

• The Journal of Korea Robotics Society
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• v.17 no.3
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• pp.288-295
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• 2022

This study shows a system identification method of a balancing loading device for a stair climbing delivery robot. The balancing loading device is designed as a 2-axes gimbal structure and is interpreted as two independent pendulum structures for simplifying. The loading device's properties such as mass, moment of inertia, and position of the center of gravity are changeable for luggage. The system identification process of the loading device is required, and the controller should be optimized for the system in real-time. In this study, the system identification method is based on least squares method to estimate the unknown parameters of the loading device's dynamic equation. It estimates the unknown parameters by calculating them that minimize the error function between the real system's motion and the estimated system's motion. This study improves the accuracy of parameter estimation using a null space solution. The null space solution can produce the correct parameters by adjusting the parameter's relative sizes. The proposed system identification method is verified by the simulation to determine how close the estimated unknown parameters are to the real parameters.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.224-228
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• 2003

The basic Principles and methods of the on-line monitoring of tribology parameters (friction coefficient and wear allowance) and fault diagnosis for the hoist disc brake system were introduced, the method were based on the spring force and oil pressure of the brake system and the hoist kinematics parameters. The experiment on the monitoring and diagnosis of hoist brake system were carried out. The research results showed: the monitoring and diagnosis methods are feasible.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.295-300
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• 2002

In this paper, an intelligent system to determine welding parameters for each pass and welding position in pipeline welding based on one database and FEM model, two BP neural network models and a C-NN model was developed and validated. The preliminary test of the system has indicated that the developed system could determine welding parameters for pipeline welding quickly, from which good weldments can be produced without experienced welding personnel. Experiments using the predicted welding parameters from the developed system proved the feasibility of interface standards and intelligent control technology to increase productivity, improve quality, and reduce the cost of system integration.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.63-68
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• 2016

This research investigates the deployment time of an active hood lift system(AHLS) activated a gunpowder actuator for the passenger vehicle. The deployment time of the system is investigated by changing the principal design parameters of the system. In order to achieve this goal, after introducing the geometric structure and operating principle of the AHLS, the dynamic equations of the system are formulated for deploying motion. Subsequently, using the dynamic equations, the deployment time of the system is determined by changing several geometric design parameters such as location of actuator. It is then identified which design parameters are main factors to affect the deployment time of AHLS.

• International Journal of Korean Welding Society
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• v.2 no.2
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• pp.32-35
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• 2002

In this paper, an intelligent system to determine welding parameters for each pass and welding position in pipeline welding based on one database and FEM model, two BP neural network models and a C-NN model was developed and validated. The preliminary test of the system has indicated that the developed system could determine welding parameters fur pipeline welding quickly, from which good weldments can be produced without experienced welding personnel. Experiments using the predicted welding parameters from the developed system proved the feasibility of interface standards and intelligent control technology to increase productivity, improve quality, and reduce the cost of system integration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1044-1052
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• 2006

In this paper the optimum position of optical phase conjugator (OPC) and the optimal dispersion coefficients of filler sections in WDM system with the conventional mid-span spectral inversion (MSSI) are numerically induced and then applied into $16{\times}40$ Gbps WDM systems with 1,000km non zero - dispersion shifted fiber(NZ-DSF) in order to efficiently compensate for the distorted overall channels. It is confirmed that the compensation extents of overall WDM channels are more improved by applying the induced optimal parameters into WDM system than those in WDM system with the conventional MSSI. So it is expected to alternate with the forming method of the symmetrical distributions of power and local dispersion by applying these optimal parameters into the real WDM system, which generate a serious problem of applying the OPC into multi-channels WDM system if it is not formed. It is also confirmed that two optimal parameters depend on each other, but less related with the finding procedure. And, it will be possible to realize the flexible system design by applying the methods proposed in this paper into the real WDM system with OPC.