• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.121-123
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• 1988

For the high speed drive of induction machine, Thyristor inverter utilizing line and device commutation is proposed. By investigating the load commutation conditions, the possible area of commutation is clearly shown. And from the above results, starting method under the constant slip frequency, is suggested.

• Journal of the Chungcheong Mathematical Society
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• v.7 no.1
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• pp.123-139
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• 1994

In this paper we are concerned with optimal control problems whose costs are quadratic and whose states are governed by linear delay differential equations and general boundary conditions. The basic new idea of this paper is to introduce a new class of linear operators in such a way that the state equation subject to a starting function can be viewed as an inhomogeneous boundary value problem in the new linear operator equation. In this way we avoid the usual semigroup theory treatment to the problem and use only linear operator theory.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.324-326
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• 1999

For induction motors cannot maintain constant speed in various speed conditions, synchronous motors are generally used. But synchronous motor oscillate in shocking load, and it cannot start by itself for the lack of starting torque. In this paper, we analyzed the synchronous induction motor which has both characteristics, and compared the experimental results with FEM analysis.

• Journal of Powder Materials
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• v.11 no.3
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• pp.217-223
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• 2004

Submicron nickel powders were prepared from aqueous solution under hydrothermal condition. The experimental conditions including the types of protective agents, concentration of the solution and the pH were studied in detail. Starting concentration of nickel ion is a dominant factor affecting particle size. It was shown that the subsequent addition of Poly Vinyl Pyrrolidone(PVP) and Sodium Dodecyle Sulfate(SDS) can help to disperse the nickel powder. X-ray diffraction and SEM were employed to characterize the products.

• The Korean Journal of Applied Statistics
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• v.6 no.2
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• pp.319-328
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• 1993

The actual convergence rate of Newton-Raphson iteration method at each step is studied under the regularity conditions for the limiting distribution: The convergence rate of it is accelerated with good starting values. Hence we can decide a number of iterations according to our purposes.

• Proceedings of the KSLP Conference
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• 1998.11a
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• pp.210-210
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• 1998

Vocal fold vibration is essentially the propagation of a mucosal wave, starting from the lower surface of the vocal fold. The mucosal upheaval (MU), where the mucosal wave starts and propagates upward, appears only when the vocal fold vibrates. We investigated the location of the mucosal upheaval in response In variations in vocal fold tension. Vibrations were elicited under three conditions: during bilateral thyroarytenoid (TA) muscle contraction, without TA muscle contraction and during vocal fold lengthening. TA muscle contraction was obtained by direct electrical stimulation of the muscle. The vocal fold was lengthened by cricothyroid (omitted)

• Bulletin of the Korean Chemical Society
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• v.16 no.11
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• pp.1122-1125
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• 1995

Three inherently chiral calix[4]arenes 3-5 were synthesized as racemate starting from the ethylation at 1.3-distal hydroxy groups of calix[4]arene 2 which has two phenyl groups at upper rim in AABB fashion, and then two remaining hydroxy groups were acetylated by treatment with acetyl chloride in the presence of NaH to produce calix[4]arene 4. Treatment of 4 with AlCl3 under Fries rearrangement conditions, only one acetyl group was rearranged to the para-position to afford calix[4]arene 5 with AABC substitution pattern at the upper rim of calix. The structure of chiral calix[4]arenes were confirmed based on NMR and massspectra.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.52-63
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• 1998

In this paper, several improvements to a copy network proposed previously for multicast packet switching are described. The improvements provide a solution to some problems inherent in multicasting. The input fairness problem caused by overf low is solved by a dynamic starting point decider(DSD), which can calculate running sums of copy requests starting from any input port. The starting point is changed adaptively in every time slot based on both the fill level of the input buffers in current time slot and the overflow situations of the previous time slot. Using the fill level of the conventional network. The DSD also provides the function of regulating overall copy requests according to the amount of input traffics. This is an essential function in improving overall throughputs of the copy networks. The throughput of a multicast switch can be improved substantially if partial service of copy request is implemented when overflow occurs. Call-splitting can also be implemented by the DSD in a straightforward manner. The hardware for the DSD is derived with the objective of simple architectures for the high speed operation. Simulation study of the copy network under various traffic conditions is presented to evaluate its performance.

• Journal of Advanced Navigation Technology
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• v.18 no.5
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• pp.501-507
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• 2014

A dynamic system is called positive if any trajectory of the system starting from non-negative initial states remains forever non-negative for non-negative controls. In this paper, new sufficient conditions for asymptotic stability of the interval positive time-varying linear discrete-time systems with time-varying delay in states are considered. The considered time-varying delay time has an interval-like bound which has minimum and maximum delay time. The proposed conditions are established by using a solution bound of the Lyapunov equation and they are expressed by simple inequalities which do not require any complex numerical algorithms. An example is given to illustrate that the new conditions are simple and effective in checking stability for interval positive time-varying discrete systems.

• International Journal of Fluid Machinery and Systems
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• v.10 no.3
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• pp.218-226
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• 2017

Severe radial thrust under off-design operating conditions can be a harmful factor for centrifugal pumps. In the present work, effects of geometry of a double volute casing on the hydrodynamic performance of a centrifugal pump have been investigated focusing on off-design conditions. Three-dimensional steady Reynolds-averaged Navier-Stokes analysis was carried out by using shear stress transport turbulence model. Numerical results for the hydrodynamic performance of the centrifugal pump were validated compared with experimental data. The hydraulic efficiency and radial thrust coefficient were used as performance parameters to evaluate the hydrodynamic characteristics of the centrifugal pump. The cross-sectional area ratio of the volute casing, the expansion coefficient of the rib structure, the distance between the rib starting point and volute entrance, and radius and width of the volute entrance, and length of the rib structure, were selected as geometric parameters. Results of the parametric study show that the performance parameters are significantly affected by the geometric variables and operating conditions. Optimal configurations of the double volute casing based on the design of experiments technique show outstanding performance in terms of the efficiency and radial thrust coefficient.