• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.6
• /
• pp.67-74
• /
• 1995

This paper proposes the step-stress type-I censoring model for analyzing the data of accelerated life test and reducing the time of accelerated life test. In order to obtain the data of accelerated life test, the step-stress accelerated life test was run with voltage stress to CMOS Hex Buffer. The Weibull distribution, the Inverse-power-law model and Maximum likelihood method were used. The iterative procedure using modified-quasi-linearization method is applied to solve the nonlinear equation. The proposed Weibull step-stress type-I censoring model exactly estimases the life time of units, while reducting the time of accelerated life test and the equipments of test.

• Journal of Mechanical Science and Technology
• /
• v.14 no.5
• /
• pp.547-552
• /
• 2000

The objective of this paper is to present a modified fractional step method of keeping a constant mass flow rate in spatially periodic flows, because original fractional step methods do not precisely keep the mass flow rate constant in time. In the modified method, the mean and fluctuating pseudo-pressure gradients are separately obtained at each time step. This method is successfully applied to channel and pipe flows and shown to be suitable for maintaining a constant mass flow rate in time.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.10
• /
• pp.102-108
• /
• 1997

The technology of Semi-Solid Forging (SSF) has been actively developed to fabricate near-net- shape products using light and hardly formable materials. Generally, the SSF process is composed of slug heating, forming, compression holding and ejecting step. After forming step in SSF, the slug is compressed during a certain holding time in order to be completely filled in the die cavity and be accelerated in solidification rate. This paper presents the analysis of temperature, solid fraction and shrinkage at compression holding step for a cylindrical slug, then predicts the solidification time to obtain the final shaped part. Enthalpy-based finite element analysis is performed to solve the heat transfer problem considering phase change in solidification.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.6
• /
• pp.1357-1363
• /
• 1994

A Monte-Carlo simulation model is developed to predict size distribution produced by the coalescence of air bubbles in turbulent shear f1ow. The simulation consists of generating a population of air bubbles into the initial positions at each time step and tracking them by simulating motions and checking collisions. The radial displacement of air bubbles in the simulation model is produced by numerically solving an advective diffusion equation. Longitudinal displacements are generated from the logarithmic flow velovity distribution and the bubble rise velocity. Collision of air bubbles for each time step is detected by a geometric test using their relative positions at the beginning of the time step and relative displacements during the time step. At the end of the time step, the total number of bubbles, their positions, and sizes are updated. The computer program is coded such that minimum storages for sizes and positions of bubbles are required.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.41 no.3
• /
• pp.199-206
• /
• 2005

As the basic study about improvement of yellow croaker drift gill net fishing implement and development of the fishing system, this study drew problem after synthetically analyzing hauling system of yellow croaker drift gill net used in the coast of Chuja Island and tested several characters and analyzed in hauling process with 5 step net hauler model for improving the problem. The analysis results are as follows. When the angle between axises of drum centers was small, it showed the tendency that hauling time was fast. Hauling time was faster when drum was 5 step rather than 3 step. When drum was 5 step, slippery phenomenon was small and hauling was stable. Tension was larger when drum was 5 step rather than 3 step. When drum was 5 step, the range of change of the maximum and minimum value was small and hauling was stable. When drum was 3 step, there was following formula between hauling time ($Ht_3$) and angle between axises of drum centers ($A_g$) $Ht_3$ : ($7.15Hs^{-0.81}$) $A_g^{-0.81}$, when drum was 5 step there was following formula.$Ht_5$ : ($6.45Hs^{-0.75}$) $A_g0.10$, here, Hs is hauling speed. When drum was 3 step and hauling speed was 28cm/sec, tension was $T=0.08A_8^3-1.60A_g^3-0.49A_g+369.56(r=0.99)$, when drum was 5 step, tension was, $T=-0.01A_g^3+1.96A_g^2-34.05A_g+414.58$ (r-0.99), here, T was tension(g).

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.5A
• /
• pp.267-275
• /
• 2003

In UMTS terminal modem uses 3 step search procedure for initial cell search, which comprises 1) slot synchronization, 2) code group identification and frame synchronization, and 3) scrambling-code identification. The performance of initial cell search procedure depends on search parameters like observation time and threshold. The purpose of this paper is to get the optimal observation time and threshold of each step for minimum mean acquisition time. In this paper we induce mean detection time of each step and mean acquisition timefrom the model of 3 step search procedure using state diagram. Also we propose initial cell search algorithm which utilize window search method against initial oscillator error, and select an appropriate observation time and threshold of each step by the analysis of simulation and induced result. It is shown that the mean acquisition time in multipath fading channel can be shorter than 500ms by using the determined observation time and threshold of each step.

• Journal of the East Asian Society of Dietary Life
• /
• v.1 no.2
• /
• pp.115-127
• /
• 1991

Information on brew time for Samhaeju can get from the 26 kinds of classical literature, which deal with Samhaeju. Usually, Samhaeju is brewed on any day of the Boar in January of the lunar calendar. However, any day of the Boar in a year seams to be possible for the brew time. In the first step of the manufacture procedure, nonglutinous and glutinous rice are used with the same propontion. The nonglutious and glutinous rice ratio become higher on the 2nd and the 3rd step than in the 1st step. The amount of water adding to the Samhaeju-base is increased step by step. In the first step, processing type of the cereal is predominantly gruel type, which is followed by rice calce. In the 2nd step, rice cake and doughnut-type rice cake are more common type than gruel type. In the 3rd step, processing type of the cereal in Samhaeju is mostly steamed water-soaked rice. Companing China and Japan with Korea, there is difference in the processing types of the cereal. They use steamed water-soaked rice in any step. Nuruk(fermenter) is added to the cold processed cereal in the first step.

• Proceedings of the KIEE Conference
• /
• 2008.04c
• /
• pp.26-28
• /
• 2008

This paper proposes a method correcting the error which is created inherently by time-step approximation in FEA. For a simple RL linear circuit, the error in time-step analysis is analytically investigated and the correction method is proposed. Then for a practical inductor model, non-linear time-step analysis is performed and the calculation result is corrected by the proposed method. The accuracy of the corrected result is confirmed by comparing the electric input and output power.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.803-808
• /
• 2007

LCCA module enabling to estimate LCC and analyze time-variant reliability index of a plate girder bridge was developed. The developed module was based on the designed data structure following the standardized methodology of ISO/STEP, LCCA module consisted of LCC estimation module, which is composed of six sub modules according to the cost category, and reliability index analysis module, which is composed of time-variant corrosion sub module, time-variant live load sub module, and element reliability analysis sub module, The effectiveness of the developed LCCA module was verified by estimating LCC and analyzing time-variant reliability index of a plate girder bridge on the basis of the constructed test database.

• Structural Engineering and Mechanics
• /
• v.8 no.6
• /
• pp.561-578
• /
• 1999

The response of a reinforced concrete structure to loading is both immediate and time-dependent. Under a sustained load, the deflections caused by creep and shrinkage may be several times their instantaneous values. The paper describes a general finite element procedure, based on the so-called layered model, to analyse reinforced concrete members, and shows in particular how the simple Step by Step Method may be incorporated into this procedure. By invoking the Modified Newton Raphson Method as a solution procedure, the accuracy of the finite element method is verified against independent test results, and then applied to a variety of problems in order to demonstrate its efficacy. The method forms a general method for analysing highly indeterminate concrete structures in the time domain.