• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.258-259
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• 2000

Quantum Well Disordering (QWD) has drawn a considerable attention in recent years$^{(1-3)}$ due to its wide applicability to optoelectronic devices. QWD allows modification of the shape of QW in selected regions, hence it modifies the subband energies in conduction and valance bands$^{(4)}$ . This leads to changes in optical properties such as band gap, absorption coefficient and refractive index. Thus such disordering in selected areas enables monolithic integration of various optoelectronic devices such as lasers, EA/EO modulators, waveguides and optical amplifiers. In this paper, we investigate the quantum well disordering effects on photoluminescence spectra by using experimental measurements and theoretical analysis$^{(5)}$ . (omitted)

• 한국생산제조학회지
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• 제6권3호
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• pp.82-88
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• 1997

This paper derives the generalized stiffness to find dynamic characteristics and its derivatives of a continuous system. And a new sensitivity analysis method is presented by using the amount of change of generalized stiffness and vibrational mode caused by the variation of stiffness. In this paper, to get or detect appropriate results, cantilever beam and stepped beam and stepped beam are used. Deviations of sensitivity coefficient, natural frequency, and vibrational mode are calculated as result, and compared with the theoretical exact values.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.644-651
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• 2001

The purpose of this study is to develop the improvement method of MOV(Motor Operated Valve) operability without major modification or change of MOV which needs a great expense and manpower. We studied valve stem lubrication, stem packing thrust and actuator control switch which could give an major effect to MOV operability, and found the some consequences. First, the stem/stem-nut friction coefficient and stem factor is significantly effected by stem lubrication state. Second, the measured packing thrust value is appeared higer than the design value for tested valves and the preparation of optimal value selection criteria is needed. Finally, optimization of MOV control switch is another major factor for MOV operability and structual integrity.

• Communications for Statistical Applications and Methods
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• 제8권1호
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• pp.159-171
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• 2001

Shapiro and Wilk (1972) developed a test for exponentiality with origin and scale unknown. The procedure consists of comparing the generalized least squares estimate of scale with the estimate of scale given by the sample variance. However the test statistic is inconsistent ; that is, the power of the test will not approach 1 as the sample size increases. Hence we give a test based on the ratio of two asymptotically efficient estimates of scale. We also have conducted a power study to compare the test procedures, using Monte Carlo samples from a wide range of alternatives. It is found that the suggested statistics have higher power for the alternatives with the coefficient of variation greater that or equal to 1.

• KSTLE International Journal
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• 제9권1_2호
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• pp.10-12
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• 2008

Silicon micro-patterns were fabricated on Si (100) wafers using photolithography and DRIE (Deep Reactive Ion Etching) fabrication techniques. The patterned shapes included micro-pillars and micro-channels. After the fabrication of the patterns, the patterned surfaces were chemically modified by coating Z-DOL (perfluoropolyether, PFPE) thin films. The surfaces were then evaluated for their micro-friction behavior in comparison with those of bare Si (100) flat, Z-DOL coated Si (100) flat and uncoated Si patterns. Experimental results showed that the chemically treated (Z-DOL coated) patterned surfaces exhibited the lowest values of coefficient of friction when compared to the rest of the test materials. The results indicate that a combination of both the topographical and chemical modification is very effective in reducing the friction property. Combined surface treatments such as these could be useful for tribological applications in miniaturized devices such as Micro/Nano-Electro-Mechanical-Systems (MEMS/NEMS).

• 소음진동
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• 제7권5호
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• pp.797-801
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• 1997

This paper raises issues in testing the absorption coefficients of sound-absorptive samples using the standing wave apparatus according to the Korean standard of KS F 2814. The standard code does not consider any effect of air-damping which is significant in testing relatively low sound-absorptive samples. This limitation has been shown to yield much variation of sound absorption coefficients for recent samples tests whose coefficients are less than 10%. An improved method of calculating the sound absorption coefficients is proposed in this work and its effectiveness in real test is also illustrated. Finally, the guideline for the modification of our national standard code KS F 2814 is proposed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.368-370
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• 2001

There are various shapes such as square, rectangular, L, and T type in the grounding systems of substations. IEEE St-d suggests the formula considering the characteristics of the various grounding systems but the final value can not be taken, and them the analysis of complicated computer program for obtaining the more accurate value is needed. In his paper, by using CDEGS(Current, Distribution, Electromagnetic and Soil Structure Analysis) the estimated functions derives form the modification coefficient for each of various types above mentioned. The mesh voltage expected can be obtained without the conventional expensive program using compensating methods that multiply IEEE formula by the estimated function.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1546-1548
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• 1997

We investigated microhardness, friction, wear and wettability of polyimide for finding out the influence of ion implantation on surface properties. For increasing doses microhardness increased. A reduction of the friction coefficient was most cases correlated with a reduction of wear. The contact angles of water for $B^+$, $N^+$ implanted polyimide decreased from $76^{\circ}$ to zero, as the fluences increased energy of 50, 200 keV.

• 전자공학회논문지B
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• 제31B권12호
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• pp.35-44
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• 1994

In this paper, we propose a new modification method of the look-up table in self-organizing fuzzy control using look-up table. This method has the property that look-up table is modified to have fast response property. Its principle is that the controller forces the trajectory to go into the fast respose region which the error change amount is larger than the error at initial time whenever the reference or disturbance change. Also we introduce the variable learning speed coefficient which is proportional to distance from switching curve. And to demonstrate the applicability of the proposed method, we had simulation study for some examples and esecuted pole balance experiments with inverted pendulum.

• Geomechanics and Engineering
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• 제7권4호
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• pp.431-458
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• 2014

Construction of a new cavern close to an existing cavern will result in a modification of the state of stresses in a zone around the existing cavern as interaction between the twin caverns takes place. Extensive plane strain finite difference analyses were carried out to examine the deformations induced by excavation of underground twin caverns. From the numerical results, a fairly simple nonparametric regression algorithm known as multivariate adaptive regression splines (MARS) has been used to relate the maximum key point displacement and the percent strain to various parameters including the rock quality, the cavern geometry and the in situ stress. Probabilistic assessments on the serviceability limit state of twin caverns can be performed using the First-order reliability spreadsheet method (FORM) based on the built MARS model. Parametric studies indicate that the probability of failure $P_f$ increases as the coefficient of variation of Q increases, and $P_f$ decreases with the widening of the pillar.