• Journal of Power Electronics
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• v.5 no.4
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• pp.312-318
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• 2005

This paper presents a compensator for reduction of the reactive lateral current in multiple autonomously controlled uninterruptible power supplies (UPS) connected in parallel. This compensator acts directly on the control equation for voltage amplitude and it provides an improved current distribution especially in the case of parallel connection of UPSs with different output power ratings. Observations show that the original control equation for output voltage amplitude is efficient for voltage regulation but it causes great variation of voltage levels. A compensator with the same structure is added to counterbalance the variation caused by the original control equation. Simulations show promising results with the employment of the proposed compensator. Our simulations are confirmed by experimental results using three UPSs with different output ratings and voltage limiters ($1\%$) connected in parallel under various conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.1
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• pp.1-10
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• 2004

This paper presents a navigation garde capacitive microaccelerometer, whose low-noise high-resolution detection capability is achieved by a new electrode design based on a high-amplitude anti-phase sense voltage. We reduce the mechanical noise of the microaccelerometer to the level of 5.5$\mu\textrm{g}$/(equation omitted) by increasing the proof-mass based on deep RIE process of an SOI wafer. We reduce the electrical noise as low as 0.6$\mu\textrm{g}$/(equation omitted) by using an anti-phase high-amplitude square-wave sense voltage of 19V. The nonlinearity problem caused by the high-amplitude sense voltage is solved by a new electrode design of branched finger type. Combined use of the branched finger electrode and high-amplitude sense voltage generates self force-balancing effects, resulting in an 140％ increase of the bandwidth from 726㎐ to 1,734㎐. For a fixed sense voltage of 10V, the total noise is measured as 2.6$\mu\textrm{g}$/(equation omitted) at the air pressure of 3.9torr, which is the 51％ of the total noise of 5.1$\mu\textrm{g}$/(equation omitted) at the atmospheric pressure. From the excitation test using 1g, 10㎐ sinusoidal acceleration, the signal-to-noise ratio of the fabricated microaccelerometer is measured as 105㏈, which is equivalent to the noise level of 5.7$\mu\textrm{g}$/(equation omitted). The sensitivity and linearity of the branched finger capacitive microaccelerometer are measured as 0.638V/g and 0.044％, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.931-937
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• 2003

The principle of the superconducting vortex flow transistor (SVFT) is based on control of the Abrikosov vortex flowing along a channel. The induced voltage is controlled by a bias current and a control current, instead of external magnetic field. The device is composed of parallel weak links with a nearby current control line. We explained the process to get an I-V characteristic equation and described the method to induce the external and internal magnetic field by the Biot-Savarts law in this paper. The equation can be used to predict the I-V curves for fabricated device. From the equation we demonstrated that the current-voltage characteristics were changed with input parameters. I-V characteristics were simulated to analyze a SVFT with multi-channel by a computer program.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.2
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• pp.93-99
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• 2001

A new type geometric and mathematical network reduction model is introduced. Large-scale network is analyzed with analytic approach. The graph has many nodes, branches and loops. Circuit equation are obtained from these elements and connection rule. In this paper, the analytic relation between voltage source has a mutual different graphic property. Node-reduction procedure is achieved with this circuit property. Consequently voltage source value is included into the adjacent node-analyzing equation. A resultant model equations are reduced as much as voltage source number. Matrix rank is (n-1-k), where n, k is node and voltage source number. The reduction procedure is described and verified with geometric principle and circuit theory. Matrix type circuit equation can be composed with this technique. The last results shall be calculated by using computer.

• Journal of IKEEE
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• v.22 no.3
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• pp.716-722
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• 2018

This paper presents a voltage angle control strategy for surface permanent magnet synchronous motor (SPMSM) drives used in low-cost applications, wherein a current vector control is not employed. In the proposed method, the current vector control scheme, which requires high precision phase-current sensing units and a fast calculation capability of a motor drive controller, is replaced with the voltage angle controller. The proposed voltage angle controller calculates a d-axis voltage command to make the d-axis current zero by using a simple equation obtained from the voltage equation of SPMSM. The proposed method shows performance similar to the current vector controlled SPMSM drive during steady-states and its structure is very simple and thus it can be easily implemented with a low-cost microcontroller. The effectiveness of the proposed method is verified through simulations and experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.372-377
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• 2013

This paper have presented the breakdown voltage for double gate(DG) MOSFET. The analytical solution of Poisson's equation and Fulop's breakdown condition have been used to analyze for breakdown voltage. The double gate(DG) MOSFET has the advantage to reduce the short channel effects as improving the current controllability of gate. But we need the study for the breakdown voltage of DGMOSFET since the decrease of the breakdown voltage is unavoidable. To approximate with experimental values, we have used the Gaussian function as charge distribution for Poisson's equation, and the change of breakdown voltage has been observed for device geometry. Since this potential model has been verified in the previous papers, we have used this model to analyze the breakdown voltage. As a result to observe the breakdown voltage, the smaller channel length and the higher doping concentration become, the smaller the breakdown voltage becomes. Also we have observed the change of the breakdown voltage for gate oxide thickness and channel thickness.

• Journal of information and communication convergence engineering
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• v.7 no.1
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• pp.57-61
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• 2009

This paper has presented the subthreshold current model of FinFET using the potential variation in the doped channel based on the analytical solution of three dimensional Poisson's equation. The model has been verified by the comparison with the data from 3D numerical device simulator. The variation of subthreshold current with front and back gate bias has been studied. The variation of subthreshold swing and threshold voltage with front and back gate bias has been investigated.

• ETRI Journal
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• v.31 no.1
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• pp.42-50
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• 2009

A new method for simulating voltage and current distributions in transmission lines is described. It gives the time domain solution of the terminal voltage and current as well as their line distributions. This is achieved by treating voltage and current distributions as distributed state variables (DSVs) and turning the transmission line equation into an ordinary differential equation. Thus the transmission line is treated like other lumped dynamic components, such as capacitors. Using backward differentiation formulae for time discretization, the DSV transmission line component is converted to a simple time domain companion model, from which its local truncation error can be derived. As the voltage and current distributions get more complicated with time, a new piecewise exponential with controllable accuracy is invented. A segmentation algorithm is also devised so that the line is dynamically bisected to guarantee that the total piecewise exponential error is a small fraction of the local truncation error. Using this approach, the user can see the line voltage and current at any point and time freely without explicitly segmenting the line before starting the simulation.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.2
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• pp.110-115
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• 2000

The electromechanical reciprocity identity is introduced to relate the voltage at the terminals of a transducer to the acoustic wavefields scattered from the specimen. The voltage at the terminals of the transducer is expressed as an integral equation in terms of the displacement and stress of the incident and scattered waves on the closed surface enclosing the scatterer. The equation is used to relate the voltage at the terminals of an acoustic microscope's transducer to the acoustic wavefields at the interface between the specimen and the coupling fluid. The voltage calculated using the integral equation is compared with the experimental result.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.3
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• pp.173-181
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• 2005

A new two dimensional (2-D) model for the potential distribution of fully depleted short-channel ion-implanted silicon MESFET's has been presented in this paper. The solution of the 2-D Poisson's equation has been considered as the superposition of the solutions of 1-D Poisson's equation in the lateral direction and the 2-D homogeneous Laplace equation with suitable boundary conditions. The minimum bottom potential at the interface of the depletion region due to the metal-semiconductor junction at the Schottky gate and depletion region due to the substrate-channel junction has been used to investigate the drain-induced barrier lowering (DIBL) and its effects on the threshold voltage of the device. Numerical results have been presented for the potential distribution and threshold voltage for different parameters such as the channel length, drain-source voltage, and implanted-dose and silicon film thickness.