• Journal of Integrative Natural Science
• /
• v.10 no.4
• /
• pp.249-257
• /
• 2017

The main focus when developing software is to improve the reliability and stability of a software system. We are enjoying a very comfortable life thanks to modern civilization, however, comfort is not guaranteed to us. Once software systems are introduced, the software systems used in the field environments are the same as or close to those used in the development-testing environment; however, the systems may be used in many different locations. Development of software system is a difficult and complex process. Generally, existing software reliability models are applied to software testing data and then used to make predictions on the software failures and reliability in the field. In this paper, we present an improved exponential NHPP software reliability model in different development environments, and examine the goodness-of-fit of improved exponential model and other model based on two datasets. The results show that the proposed model fits significantly better than other NHPP software reliability model.

• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.1
• /
• pp.58-69
• /
• 2014

This paper proposes a method for predicting maximum friction coefficients and optimal slip ratios as optimal control parameters for traction control or slip control of autonomous mobile robots on rough terrain. This paper focuses on strength of ground surface which indicates different characteristics depending on material types on surface. Strength of various material types can be estimated by Willoughby sinkage model and by a developed testbed which can measure forces, velocities, and displacements generated by wheel-terrain interaction. Estimated strength is collaborated on building improved Brixius model with friction-slip data from experiments with the testbed over sand and grass material. Improved Brixius model covers widespread material types in outdoor environments on predicting friction-slip characteristics depending on strength of ground surface. Thus, a prediction model for obtaining optimal control parameters is derived by partial differentiation of the improved Brixius model with respect to slip. This prediction model can be applied to autonomous mobile robots and finally gives secure maneuverability on rough terrain. Proposed method is verified by various experiments under similar conditions with the ones for real outdoor robots.

• Journal of Wetlands Research
• /
• v.13 no.1
• /
• pp.13-23
• /
• 2011

In this study, Mike11 will be used as the numerical model where a data assimilation method will be applied to it. This paper aims to gain an insight and understanding of data assimilation in flood forecasting models. It will start with a general discussion of data assimilation, followed by a description of the methodology and discussion of the statistical error forecast model used, which in this case is the linear regression. This error forecast model is applied to the water level forecast simulated by MIKE11 to produced improved forecast and validated against real measurements. It is found that there exists a phase error in the improved forecasts. Hence, 2 general formula are used to account for this phase error and they have shown improvement to the accuracy of the forecasts, where one improved the immediate forecast of up to 5 hours while the other improved the estimation of the peak discharge.

• Journal of Industrial Technology
• /
• v.25 no.A
• /
• pp.67-73
• /
• 2005

In this research, centrifuge model experiments and numerical approach of finite element method to analyze experimental results were performed to investigate the behavior of improved ground with sand compaction piles. One of typical clay minerals, kaolinite powder, were prepared for soft ground in model tests. Jumunjin standard sand was used to sand compaction pile installed in the soft soil. In order to investigate the characteristics of mechanical behavior of sand compaction piles with low replacement ratios, centrifuge model experiments with the replacement ratio of 40%, changing the width of improved area with respect to testing results the width of surcharge loads, were carried out to obtain of bearing capacity, characteristics of load-settlement, vertical stresses acting on the sand pile and the soft soil failure mechanism in improved ground.

• Journal of Multimedia Information System
• /
• v.5 no.4
• /
• pp.221-228
• /
• 2018

Skin-color information is not sufficient for palmprint segmentation in complex scenes, including mobile environments. Traditional active shape model (ASM) combines gray information and shape information, but its performance is not good in complex scenes. An improved ASM method is developed for palmprint segmentation, in which Perux method normalizes the shape of the palm. Then the shape model of the palm is calculated with principal component analysis. Finally, the color likelihood degree is used to replace the gray information for target fitting. The improved ASM method reduces the complexity, while improves the accuracy and robustness.

• Journal of Mechanical Science and Technology
• /
• v.20 no.9
• /
• pp.1399-1409
• /
• 2006

An improved friction model was proposed with consideration of the effect of the sliding speed, the contact pressure and the temperature, and it was implemented into a user subroutine of a commercial FEM code, ABAQUS/Explicit. Then, a smooth tire was simulated for free rolling, driving, braking and cornering situations using the improved friction model and the Coulomb friction model, and the effect of the friction models on the slip, the frictional energy distribution and the cornering force and moment was analyzed. For the free rolling, the driving and the braking situations, the improved friction model and the Coulomb friction model resulted in similar profiles of the slip and the frictional energy distributions although the magnitudes were different. The slips obtained from the simulations were in a good correlation with experimental data. For the cornering situation, the Coulomb friction model with the coefficient of friction of 1 or 2 resulted in lower or higher cornering forces and moments than experimental data. In addition, in contrast to experimental data it did not result in a maximum cornering force and a decrease of the cornering moment for the increase of the speed. However, the improved friction model resulted in similar cornering forces and moments to experimental data, and it resulted in a maximum cornering force and a decrease of the cornering moment for the increase of the speed, showing a good correlation with experimental data.

• Journal of the Korea Society for Simulation
• /
• v.25 no.3
• /
• pp.41-51
• /
• 2016

In this study, we propose an improved Floor Field Model(FFM) that considers the physical characteristics of pedestrians, i.e., body size, shape, and posture. Also we analyse limits of FFM and features of improved model compared with existing evacuation simulation models. FFM is a typical microscopic pedestrian model using CA, but it does not reflect the physical characteristics of pedestrians. Because of this, FFM is difficult to modeling phenomena such as collision, friction between pedestrians. As a result, FFM calculates a very short evacuation time when compared with the other models. We performed a computational experiment to compare improved model with other models such as FFM, Simulex, Pathfinder in an actual campus building. We carried out a comparison of evacuation aspect according to the change in number of evacuees. Also we compared evacuation aspect by exit. Finally, we confirmed that improved model reflects physical phenomena which were not reflected in FFM. Especially, experimental results were very similar to the Simulex.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.8
• /
• pp.64-70
• /
• 1995

A new DC drain-current model of GaAs MESFET with improved accuracy is proposed in this paper. The proposed model includes the decrease of current slope according to gate voltages. It is possible to represent a transconductance compression using the proposed model. It shows improved transconductance and output resistance in accuracy from the forward biased gate region to near the cutoff region. The wquaer error of saturation current is decreased by 46% compared with Statz model. The proposed model can be useful for the simulation of large-signal operation and harmonic distortion.

• 유체기계공업학회:학술대회논문집
• /
• 2002.12a
• /
• pp.111-115
• /
• 2002

The objective of this work is to develop improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan by investigating the validity of various slip factor models. Both steady and unsteady three-dimensional CFD analyses were performed with a commercial code tn validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the presented model takes into account the effect of blade curvature. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peaktotal pressure coefficient.

• Journal of Mechanical Science and Technology
• /
• v.18 no.2
• /
• pp.302-312
• /
• 2004

This work developed improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan. Both steady and unsteady three-dimensional CFD analyses were performed to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the present model takes into account the effect of blade curvature. The correction method is provided to predict mass-averaged absolute circumferential velocity at the exit of impeller by taking account of blockage effects induced by the large-scale backflow near the front plate and flow separation within blade passage. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient.