• Tunnel and Underground Space
• /
• v.12 no.3
• /
• pp.189-197
• /
• 2002

In recent years, the probabilistic analysis has been used in rock slope engineering. This is because uncertainty is pervasive in rock slope engineering and most geometric and geotechnical parameters of discontinuity and rock masses are involved with uncertainty. Whilst the traditional deterministic analysis method fails to properly deal with uncertainty, the probabilistic analysis has advantages quantifying the uncertainty in parameters. As a probabilistic analysis method, the Monte Carlo simulation has been used commonly. However, the Monte Carlo simulation requires many repeated calculations and therefore, needs much effort and time to calculate the probability of failure. In contrast, the point estimate method involves a simple calculation with moments for random variables. In this study the probability of failure in rock slope is evaluated by the point estimate method and the results are compared to the probability of failure obtained by Monte Carlo simulation method.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.1
• /
• pp.241-251
• /
• 1991

The present simulation model relies on a new approach of the heavy particle motion in a turbulent flow considering the time and space correlation to the Lagrangian point of view. The turbulent field is, here, assumed that its characteristic scales are random and follow a Poisson's distribution. Using this model, we have computed the trajectory of each particle, that is, its velocity and position at each time in order to study the dispersion of particles in a grid turbulent flow. The computed results have been compared to the corresponding experimental data. Due to the complex mechanism of turbulence and the theoretically and experimentally lacking information, we had to make some assumptions for simplifying the situation, but we have found the good agreement between simulated and measured results. In particular, the application of the present method on the Lagrangian correlation of particle provides an interesting alternative to the usual computational methods.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.4 no.4
• /
• pp.9-19
• /
• 2008

In this paper, it is studied anti-collision algorithm based on the transmission protocol for RFID baseband system of the lSO/IEC 18000-6 Type-C regulation and designed the baseband part of RFID reader system using FPGA. To compensate this weak point of the slot random aloha algorithm which must have a long time to be dumped before deciding an appropriate slot size according to the number of surrounding tag, we suggested how to apply Bit By Bit algorithm to be able to recognize the tag when the tag is clashing. The design of the baseband part in the RFID reader system is accomplish by use of the ISE9.1i and I made an experiment on it targeting Spartan2. Construction verification is measured each block through Logic Analyzer and I can verify it has no error. I also compared and analyzed the performance between proposed algorithm and past algorithm and verified the improvement of performance.

• Journal of the Korean Ceramic Society
• /
• v.42 no.5 s.276
• /
• pp.326-332
• /
• 2005

Phase transformation effects on mechanical properties of $Ge_2Sb_2Te_5$, which is a promising candidate material for Phase Change Random Access Memory (PRAM), were studied. $Ge_2Sb_2Te_5$ thin films, which was thermally annealed with different conditions, were analyzed using XRD, AFM, 4-point probe method and reflectance measurement. As the temperature and the dwelling time increased, crystallity and grain size increased, which enhanced elastic modulus and hardness. Furthermore, N2 doping, which was used for better electrical properties, was proved to decrease elastic modulus and hardness of $Ge_2Sb_2Te_5$.

• Journal of Environmental Science International
• /
• v.7 no.4
• /
• pp.511-522
• /
• 1998

The two-stage numerical model was used to study the relation between three-dimensional local wind seal area for Korean peninsula. The first stave is three dimensional time-dependent local wind model which elves the wind field and vertical diffusion coefncient. The second stage is advection/duusion model which uses the results of the first stage as input data. First, wand fields on Korean peninsula for none synoptic scale wand showed typical land and sea breeze circulation, and the emitted particles were transported by sea breeze for daytime, emissions return to sea by land breeze for nighttime.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.18 no.1
• /
• pp.91-98
• /
• 2023

With the increasing flood damage by frequently localized heavy rains, flood prediction research are being conducted to prevent flooding damage in advance. In this paper, we present a machine-learning scheme for developing a flooding depth and location prediction model using real-time rainfall data. This scheme proposes a dataset configuration method using the data as input, which can robustly configure various rainfall distribution patterns and train the model with less memory. These data are composed of two: valid total data and valid local. The one data that has a significant effect on flooding predicted the flooding location well but tended to have different values for predicting specific rainfall patterns. The other data that means the flood area partially affects flooding refers to valid local data. The valid local data was well learned for the fixed point method, but the flooding location was not accurately indicated for the arbitrary point method. Through this study, it is expected that a lot of damage can be prevented by predicting the depth and location of flooding in a real-time manner.

• Journal of the Korean Society of Safety
• /
• v.7 no.2
• /
• pp.71-79
• /
• 1992

This paper presents a least-square algorithms of lattice structures and their use for adaptive prediction of time series generated from the dynamic system. As the view point of adaptive prediction, a new method of Identification of dynamic characteristics by means of estimating the parameters of linear auto regressive model is proposed. The fast convergence of adaptive lattice algorithms is seen to be due to the orthogonalization and decoupling properties of the lattice. The superiority of the least-square lattice is verified by computer simulation, then predictor coefficients are computed from the linear sequential time data. For the application to the dynamic characteristic analysis of unknown system, the transfer function of ideal system represented in frquency domain and the estimated one obtained by predicted coefficients are compared. Using the proposed method, the damping ratio and the natural frequency of a dynamic structure subjected to random excitations can be estimated. It is expected that this method will be widely applicable to other technical dynamic problem in which estimation of damping ratio and fundamental vibration modes are required.

• Ocean Systems Engineering
• /
• v.4 no.1
• /
• pp.63-82
• /
• 2014

Declutching control is applied to a hemispherical wave energy converter with direct linear electric Power-Take-Off systems oscillating in heave direction in both regular and irregular waves. The direct linear Power-Take-Off system can be simplified as a mechanical spring and damper system. Time domain model is applied to dynamics of the hemispherical wave energy converter in both regular and irregular waves. And state space model is used to replace the convolution term in time domain equation of the heave oscillation of the converter due to its inconvenience in analyzing the controlled motion of the converters. The declutching control strategy is conducted by optimal command theory based on Pontryagin's maximum principle to gain the controlled optimum sequence of Power-Take-Off forces. The results show that the wave energy converter with declutching control captures more energy than that without control and the former's amplitude and velocity is relatively larger. However, the amplification ratio of the absorbed power by declutching control is only slightly larger than 1. This may indicate that declutching control method may be inapplicable for oscillating wave energy converters with direct linear Power-Take-Off systems in real random sea state, considering the error of prediction of the wave excitation force.

• Korean Journal of Acupuncture
• /
• v.32 no.3
• /
• pp.130-135
• /
• 2015

Objectives : This study is to investigate stimulation effects of acupoints at differential meridian along arm and leg on the physiological phenomenon of heartbeats. Methods : 8 subjects were participated in this study. The experiments were performed in Resting session(Rs), Insertion session(Is), Stimulation session1(Ss1), Stimulation session2(Ss2), Stimulation session3(Ss3) sequence. Time of each session and the interval between each session was 30 seconds all. Acupuncture was performed manually on PC3 or LR8 at random with a two-day interval. stand deviation of N-N interval(SDNN) was measured for each session. Results : At PC3, SDNN increased in Ss1, Ss2, and Ss3 compared to Rs but at LR8, there was little change between Ss1, Ss2, Ss3 and Rs. Post-hoc analysis revealed that mean value of SDNN significantly increased in Ss1 compared with Baseline at PC3, while there was little change at LR8. When LR8 and PC3 were compared at each time point, there was a significant difference only in Ss1. Conclusions : Our results indicate that there is a correlation between specific physiological functions and acupoints.

• Communications for Statistical Applications and Methods
• /
• v.30 no.1
• /
• pp.95-107
• /
• 2023

Purpose: The statistical analysis of point processes on linear networks is a recent area of research that studies processes of events happening randomly in space (or space-time) but with locations limited to reside on a linear network. For example, traffic accidents happen at random places that are limited to lying on a network of streets. This paper applies techniques developed for point processes on linear networks and the tools available in the R-package spatstat to estimate the intensity of traffic accidents in Leon County, Florida. Methods: The intensity of accidents on the linear network of streets is estimated using log-linear Poisson models which incorporate cubic basis spline (B-spline) terms which are functions of the x and y coordinates. The splines used equally-spaced knots. Ten different models are fit to the data using a variety of covariates. The models are compared with each other using an analysis of deviance for nested models. Results: We found all covariates contributed significantly to the model. AIC and BIC were used to select 9 as the number of knots. Additionally, covariates have different effects such as increasing the speed limit would decrease traffic accident intensity by 0.9794 but increasing the number of lanes would result in an increase in the intensity of traffic accidents by 1.086. Conclusion: Our analysis shows that if other conditions are held fixed, the number of accidents actually decreases on roads with higher speed limits. The software we currently use allows our models to contain only spatial covariates and does not permit the use of temporal or space-time covariates. We would like to extend our models to include such covariates which would allow us to include weather conditions or the presence of special events (football games or concerts) as covariates.