• Journal of Industrial Technology
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• v.5
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• pp.37-46
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• 1985

Recently-used structural reliability models are studied, and the usage and characteristics of each method are discussed. Although the First-Order Second Moment method may be efficient in structural reliability analysis, it has limitations which the limit state equation is linear and all the variables are normal. In that point, the Advanced Second-Moment(ASM) method have many good results, but computation of iterative method are trublesome. The results of ASM method similar to Variance Reduction Techniques(VRT), which is one of the Monte Carlo simulation methods. As a results, it is concluded that ASM method and VRT method are most efficient one.

• Journal of Biosystems Engineering
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• v.22 no.2
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• pp.247-255
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• 1997

This study was conducted to develop regression models predicting sugar and acid contents in intact fruits nondestructively by using the second derivative of absorbance spectrum measured with a spectrophotometer wavelength range of 400nm to 2, 400nm. The correlation analysis was made in wavelength range of 600nm to 1, 100nm and 600nm to 2, 400nm respectively, in order to examine the feasibility of using a real time spectrophotometer, which covers the former range, in predicting sugar and acid contents. The second derivative data of the spectrum were obtained by varying smoothing size and derivative size of the original absorbance spectrum. SAS statistical package program was used for the regression analysis. The sugar contents of Fuji apple, Shingo pear md Yumyung peach could be predicted with SEPs of 0.40, 1.17 and 0.77 respectively, in the spectrum range of 600 to 1, 100nm. The highest correlation coefficient of the titratible acidity of apple was -0.45 at 2, 346nm and regression models indicated determination coefficient less than 0.47.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.301-308
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• 2001

The problem of predicting crack propagation in anisotropic solids which is a subject of considerable practical importance is examined. The effect of the second term in the asymptotic expansion of the crack tip stress field on the direction of initial crack extension is made explicitly. We employ the normal stress ratio theory to determine values for the direction of initial crack extension. The theoretical analysis is performed for the wide range of the anisotropic material properties. It is shown that the use of second order term in the series expansion is essential for the accurate determination of crack growth direction in anisotropic solids.

• English Language & Literature Teaching
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• v.17 no.3
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• pp.309-326
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• 2011

This study examines the relationship between second language use outside of class and oral proficiency development. It first identifies out-of-class activities of international graduate students in the U.S. and the average time spent speaking English in those out-of-class activities. Interviews and student self-measurements of time spent speaking English each day were used to investigate the types and quantities of out-of-class activities. In addition, two sets of student oral proficiency test scores were collected. Correlation analysis is used to find out the relationship of the variables between the most salient out-of-class activities and oral proficiency gains. The findings indicate that second language use outside of class is important for international graduate students to improve their oral proficiency. This is especially true with regularized interaction such as talking at work and the average time spent speaking in English a day outside of class. This study suggests that learners of English in an ESL environment should be encouraged to take part in out-of-class activities in addition to English use in the classroom in order for them to improve their oral proficiency.

• Korea-Australia Rheology Journal
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• v.11 no.3
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• pp.225-232
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• 1999

This study presents 1-dimensional simple model for sheet casting or rectangular fiber spinning process. In order to achieve this goal, we introduce the concept of force flux balance at the die exit, which assigns for the extensional flow outside the die the initial condition containing the information of shear flow history inside the die. With the Leonov constitutive equation that predicts non-vanishing second normal stress difference in shear flow, we are able to describe the anisotropic swelling behavior of the extrudate at least qualitatively. In other words, the negative value of the second normal stress difference causes thickness swelling much higher than width of extrudate. This result implies the importance of choosing the rheological model in the analysis of polymer processing operations, since the constitutive equation with the vanishing second normal stress difference is shown to exhibit the characteristic of isotropic swelling, that is, the thickness swell ratio always equal to the ratio in width direction.

• 전기의세계
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• v.14 no.2
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• pp.14-24
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• 1965

The characteristics of servo-multipliers and its accuracies are analyzed. From the analysis a low cost high accuracy four quadrant servo-multiplier with first derivative output feedback is built. The multiplier servomechanism has a second order system response with a damping ratio of 0.8 and computing bandwidth of 4 cycles per second, and its tracking accuracy at low speed of 0.5 volt per second is 0.9 per cent of maximum output voltage and static accuracy is better than 0.6 per cent. Method of testing this multiplier and the results are also described. The test on the characteristics of the multiplier shows that the results agree with theoretical values satisfactorily, and justifies the use of the servo-multiplier for slow type analog computers.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.11
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• pp.668-674
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• 2003

The electric marketplace is in the midst of major changes designed to promote competition. No longer vertically integrated with guaranteed customers and suppliers, electric generators and distributors will have to compete to sell and buy electricity. Unit commitment (UC) in such a competitive environment is not the same as the traditional one anymore. The objective of UC is not to minimize production cost as before but to find the solution that produces a maximum profit for a generation firm. This paper presents a hi-level formulation that decomposes the UC game into a generation-decision game (first level game) and a state(on/off)-decision game (second level game). Derivation that the first-level game has a pure Cournot Nash equilibrium(NE) helps to solve the second-level game. In case of having a mixed NE in the second-level game, this paper chooses a pure strategy having maximum probability in the mixed strategy in order to obviate the probabilistic on/off state which may be infeasible. Simulation results shows that proposed method gives the adequate UC solutions corresponding to a NE.

• Structural Engineering and Mechanics
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• v.24 no.2
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• pp.247-268
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• 2006

The parts of pile, above the soil and embedded in the soil are called the first region and second region, respectively. The forth order differential equations of both region for critical buckling load of partially embedded pile with shear deformation are obtained using the small-displacement theory and Winkler hypothesis. It is assumed that the behavior of material of the pile is linear-elastic and that axial force along the pile length and modulus of subgrade reaction for the second region to be constant. Shear effect is included in the differential equations by considering shear deformation in the second derivative of the elastic curve function. Critical buckling loads of the pile are calculated for by differential transform method (DTM) and analytical method, results are given in tables and variation of critical buckling loads corresponding to relative stiffness of the pile are presented in graphs.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.324-330
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• 2012

Dual bell nozzle is one of the most promising choices among the altitude adaptation nozzles. This facilitates having a forced, steady and symmetrical separation at lower altitudes and a controlled flow separation at the wall inflection point which prevents the generation of dangerous side loads. In order to ensure the attached flow in the second bell, a clear understanding of the flow transition is required. Hence the motivation of our study is to arrive at an optimum profile for the second bell, which allows a sudden and controlled transition. In this work, we designed the first bell using the conventional MoC and the second bell using an inverse MoC, imposing a pressure gradient constraint. A CFD analysis is also carried out. It is found that the separation point is near the inflection point within one fourth of the extension length or it is near the exit.

• Structural Engineering and Mechanics
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• v.4 no.2
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• pp.177-190
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• 1996

A method to numerically evaluate the behaviour of single span beams, prestressed with external tendons and symmetrically loaded is presented. This algorithm, based on the Finite Difference Method, includes second order effects and large displacements in an attempt to more fully understand the behaviour of the beam up to collapse. The numerical technique discussed is particularly appropriate for the analysis of R.C. and P.C. beams rehabilitated or strengthened by means of external prestressing but it is reliable for the analysis of new beams as well.