• Kyungpook Mathematical Journal
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• v.58 no.2
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• pp.271-289
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• 2018

Let 0 < q < ${\infty}$. In this study, we introduce the spaces ${\mathcal{BV}}_q$ and ${\mathcal{LS}}_q$ of q-bounded variation double sequences and q-summable double series as the domain of four-dimensional backward difference matrix ${\Delta}$ and summation matrix S in the space ${\mathcal{L}}_q$ of absolutely q-summable double sequences, respectively. Also, we determine their ${\alpha}$- and ${\beta}-duals$ and give the characterizations of some classes of four-dimensional matrix transformations in the case 0 < q ${\leq}$ 1.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1276-1282
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• 2003

The SMT(Surface Mount Type) ferrite bead used to reduce the influx of power bus noise is modeled with parallel capacitor(C), series resistor(R) and series inductor(L). The simple equivalent circuit modeling doesn't agree with the measurement result. In this paper, we proposed the accurate equivalent circuit model of the ferrite bead at wide frequency range(50 MHz∼3 GHz) and analyzed the noise effect to the high speed IC(Integrate Circuit) with ferrite bead or not.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2085-2087
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• 1998

This paper presents the design method of a dimming electronic ballast for fluorescent lamps using a frequency control IC, and investigates the effects of circuit variables on its dimming characteristics. It is shown that effective dimming is possible with IC IR2151 for frequency control, and this leads to a feasible design of more smaller and cheaper dimming ballast. Five ballasts different in the values of the series inductance and capactance are designed, and their dimming characteristics are compared. As the result, the dimming range becomes more broader as the series inductance gets smaller and the capacitance larger. Thus appropriate selection of the values of L and C should be made according to the types of application site.

• Structural Engineering and Mechanics
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• v.13 no.5
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• pp.491-504
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• 2002

Recently we formulated a 2D hybrid stress element from the 3D Hellinger-Reissner principle for the analysis of thick bodies that are symmetric to the thickness direction. Polynomials have typically been used for all the displacement and stress fields. Although the element predicted the dominant stress and all displacement fields accurately, its prediction of the out-of-plane shear stresses was affected by the very high order terms used in the polynomials. This paper describes an improved formulation of the 2D element using Fourier series expansion for the out-of-plane displacement and stress fields. Numerical results illustrate that its predictions have markedly improved.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1037-1038
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• 2006

The increasing demand of PM parts for automobile and aerospace applications has caused a strong development of the aluminium based metal matrix composites (MMCs).Aluminium alloys are one of most widely used materials as matrix in MMCs, both in research and development as well as in industrial applications. In the present work, the influence of the ceramic reinforcement addition to a 2xxx series aluminium alloy is studied. Several percentages of TiCN have been added to the Al-Cu alloy using PM techniques, in order to analyze its influence on the liquid phase sintering process and on the final properties of the material.

• Structural Engineering and Mechanics
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• v.23 no.5
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• pp.563-577
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• 2006

This study involves a series of experiments on the buckling strength of eccentrically compressed cold-formed stainless steel square hollow-section columns. The principal parameters in this study are slenderness ratios ($L_k/r$ = 30, 50, 70) and magnitude of eccentricity e (0, 25, 50, 75, 100 mm) on the symmetrical end-moment. The objectives of this paper are to obtain the buckling loads by conducting a series of experiments and to compare the behavior of the eccentrically compressed cold-formed stainless steel square hollow-section columns with the results of the analysis. The ultimate buckling strength of the square-section members were determined with the use of a numerical method in accordance with the bending moment-axial force (M-P) interaction curves. The behavior of each specimen was displayed in the form of a moment-radian (M-${\theta}$) relationship. The numerically obtained ultimate-buckling interaction curves of the beam columns coincided with the results of the experiments.

• International Journal of Automotive Technology
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• v.7 no.1
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• pp.91-99
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• 2006

The diesel Auxiliary Power Unit (APU) for vehicle applications is a complex nonlinear system. For the purpose of this paper presents a dynamic average model of the whole system in an entirely physical way, which accounts for the non-ideal behavior of the diode rectifier, the nonlinear phenomena of generator-rectifier set in an elegant way, and also the dynamics of the dc load and diesel engine. Simulation results show the accuracy of the model. Based on the average model, a simple PI control scheme is proposed for the multivariable system, which includes the steps of model linearization, separate PI controller design with robust tuning rules, stability verification of the overall system by considering it as an uncertain one. Finally it is tested on a detailed switching model and good performances are shown for both set-point following and disturbance rejection.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.916-920
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• 1993

In this paper, the current characteristics of the system composed of R.L.C. load and series bridge inverter is investigated through the results of computer simulation and experiment to look for the good properties of A.C. motor driven by the above inverter. The time schedule of conventional bridge inverter and the parameters such as resistance and damping coefficient of load is changed for good results. It is possible to get the load current of similar sine wave under various conditions.

• Elastomers and Composites
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• v.30 no.3
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• pp.207-217
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• 1995

The reinforcement of Inorganic filler silica treated with LBR-MDI In SBR vulcanizates were Investigated. The inorganic filler silica treated with MDI on unmodified surface and that of silica treated by MDI was retreated with LBR. The charateristics of vulcanization, physical properties, surface properites and dynamic properties were investigated after mixing those silica with SBR and unmodified silica with SBR. Rheometric studies of the vulcanization showed that S-series has fast scorch $time(t_{10})$ and an optimum cure $time(t_{90})$ in the SBR compounds. And it was turned out that SBR vulcanizates compounded with LBR treated silica was better than any other componnds in hardness, tensile strenght, 100 300% modula and elongation. We could confirm that urea bonding is formed from IR spectrum. We concluded that L-series shows the best reinforcement effect in SBR vulcanizates.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.171-173
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• 2019

In this paper, 10kV solid-state pulsed power modulator with high repetition rate is described. The modulator is based on a Marx generator that charges capacitors in parallel and discharges them in series. Twelve IGBTs and capacitors are connected in series to generate output voltages up to 10kV at a repetition rate of 100kHz. The volume of the modulator is 26.1 liters, and its maximum average output power is 10kW. Therefore, the compact design is achieved with a high power density of 380 W/L. Finally, it is confirmed that the pulsed power modulator can operate stably through the experiment results at 10kV 100kHz condition.