• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.179-188
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• 2001

The objective of this paper is to design and implement sliding mode control scheme for an actuation system using BLDC motor. Since the dynamic characteristics of this system with unknown disturbance and parameter variations are very complicated and highly nonlinear, the conventional linear control approaches may not guarantee satisfactory control performances. In order to improve the dynamic performances of this system, a model following sliding mode control(MFSMC) with perturbation estimation approach is designed and implemented. It eliminates the conventional requirements for the knowledge of uncertainty upper boundary. The effectiveness of this control approach is verified by comparison with a PID control through a series of simulation and experimental studies.

• Journal of information and communication convergence engineering
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• v.9 no.2
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• pp.172-176
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• 2011

In the Gen-2 Q-algorithm, the values of weight C, which is the parameter for incrementing or decrementing the slot-count size, are not optimized in the standard. However, the standard suggests that the reader uses small values of C when the slot-count is large and larger values of C when the slot-count is small. In this case, if the reader selects an inappropriate weight, there are a lot of empty or collided slots. As a result, the performance will be declined because the frame size does not converge to the optimal point quickly during the query round. In this paper, we propose a scheme to select the weight based on the slot-count size of current query round. Through various computer simulations, it is demonstrated that the proposed scheme achieves more stable performances than Gen-2 Q-algorithm.

• Bulletin of the Korean Mathematical Society
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• v.29 no.1
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• pp.15-24
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• 1992

The purpose of this paper is to parameterize range-equivalence classes of all eigenmaps of flat 3-tori $T^{3}$= $R^{3}$.LAMBDA., .LAMBDA.= $c_{1}$ $e_{1}$ + $c_{2}$ $e_{2}$ + $c_{3}$ $e_{3}$, into the standard unit spheres. In this paper, we classify $A_{ 0 \lambda}$( $T^{3}$)(cf..cint.1) which is contained in $A_{\lambda}$( $T^{3}$), are belonging to $A_{ 0 \lambda}$( $T^{3}$). Moreover, as an application, we show that the only minimally imbedded flat torus into ( $S^{5}$ , can) which is contained in $A_{ 0 \lambda}$( $T^{3}$) is the generalized Clifford torus.rd torus.

• Journal of the Korean Mathematical Society
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• v.55 no.2
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• pp.313-326
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• 2018

The paper studies some new ${\mathbb{C}}^n$-generalizations of Bergman type operators introduced by Shields and Williams depending on a normal pair of weight functions. We find the values of parameter ${\beta}$ for which these operators are bounded on mixed norm spaces L(p, q, ${\beta}$) over the unit ball in ${\mathbb{C}}^n$. Moreover, these operators are bounded projections as well, and the images of L(p, q, ${\beta}$) under the projections are found.

• Proceedings of the KIEE Conference
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• 2006.05a
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• pp.66-70
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• 2006

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, il requires an accurate and high speedy frequency deviation estimation technique and suitable adjustment to obtain the power system energy balance. This paper describes the design, computational aspects and implementation of an iterative technique for measuring power system. 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 154[KV] double T/L system by using EMTP software. Some test results are presented in the paper.

• Computers and Concrete
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• v.8 no.3
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• pp.243-278
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• 2011

The paper presents simulations of the Brazilian test using two numerical models. Both models are regularized in order to obtain results independent of discretization. The first one, called gradient damage, is refined by additional averaging equation which contains gradient terms and an internal length scale as localization limiter. In the second one, called viscoplastic consistency model, the yield function depends on the viscoplastic strain rate. In this model regularization properties are governed by the assumed strain rate. The two models are implemented in the FEAP finite element package and compared in this paper. Parameter studies of the split test are performed in order to point out the features of each model.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1871-1876
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• 2005

In this paper, We present a new nonlinear adaptive control law using a disturbance accommodating control (DAC) observer for a Japanese automatic landing flight experiment vehicle called ALFLEX. A future spaceplane must have ability to deal with greater fluctuations in the stability and control derivatives of flight dynamics, because its flight region is much wider than that of conventional aircraft. In our previous studies, digital adaptive flight control systems have been developed based on a linear-parameter-varying (LPV) model depending on dynamic pressure, and obtained good simulation results. However, under previous control laws, it is difficult to accommodate uncertainties represented by disturbance and nonlinearity, and to design a stable flight control system. Therefore, in this study, we attempted to design a nonlinear adaptive control law using the DAC Observer and inverse dynamic methods. A good tracking property of the obtained system was confirmed in numerical simulation.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.49-54
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• 1998

The growth of diamond films in plasma enhanced chemical vapor deposition(PECVD) processes requires high substrate temperatures and gas pressures, as well as high-power excitation of the gas source. Thus determining the substrate temperature in this severe environment is a challenge. The issue is a critical one since substrate temperature is a key parameter for understanding and optimizing diamond film growth. The precise Si substrate temperature calibration based on rapid-scanning spectroscopic ellipsometry have been developed and utilized. Using the true temperature of the top 200 ${\AA}$ of the Si substrate under diamond growth conditions, real time spectroellipsometry (RTSE) has been performed during the nucleation and growth of nanocrystallind thin films prepared by PECVD. RTSE shows that a significant volume fraction of nondiamond(or{{{{ {sp }^{2 } -bonded}}}}) carbon forms during thin film coalescence and is trapped near the substrate interface between ∼300 ${\AA}$ diamond nuclei.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.74-80
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• 2001

The estimation of recurrence interval for fault activity and earthquake is an important input parameter for seismic hazard assessment. In this study, the methods of recurrences interval estimation were reviewed and tentative calculation was performed for age dating data which have uncertainty. Age dating data come from previous studies of Ulsan fault system which is a well developed lineament in the southeastern part of korean Peninsula. Age dating for fault gouges, parent rocks, Quaternary sediments and veins were carried out by several researchers through various methods. Recurrence interval for fault activity was estimated on the basis of the age dating data of minor fault gouge and sediments during past 3Ma. The estimated recurrence interval was about 430-500 ka. Exact estimation of recurrence interval for fault activity need to compile more geological data and fault characteristics such as fault length, amount of displacement, slip rate and accurate fault movement age. In the future, the methods and results of fault recurrence interval estimation should be considered for establishing the criteria for domestic active fault definition.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.180-189
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• 2001

In this study, recently developed unscented Kalman filter (UKF) technique is studied for identification of nonlinear structural dynamic systems as an alternative to the extended Kalman filter (EKF). The EKF, which was originally developed as a state estimator for nonlinear systems, has been frequently employed for parameter identification by introducing the state vector augmented with the unknown parameters to be identified. However, the EKF has several drawbacks such as biased estimations and erroneous estimations especially for highly nonlinear dynamic systems due to its crude linearization scheme. To overcome the weak points of the EKF, the UKF was recently developed as a state estimator. Numerical simulation studies have been carried out on nonlinear SDOF system and nonlinear MDOF system. The results from a series of numerical simulations indicate that the UKF is superior to the EKF in the system identification of nonlinear dynamic systems especially highly nonlinear systems.