• Computers and Concrete
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• v.6 no.3
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• pp.253-268
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• 2009

This study aims to develop a cost-based high-performance concrete (HPC) mix optimization system based on an integrated approach using artificial neural networks (ANNs) and genetic algorithms (GA). ANNs are used to predict the three main properties of HPC, namely workability, strength and durability, which are used to evaluate fitness and constraint violations in the GA process. Multilayer back-propagation neural networks are trained using the results obtained from experiments and previous research. The correlation between concrete components and its properties is established. GA is employed to arrive at an optimal mix proportion of HPC by minimizing its total cost. A system prototype, called High Performance Concrete Mix-Design System using Genetic Algorithm and Neural Networks (HPCGANN), was developed in MATLAB. The architecture of the proposed system consists of three main parts: 1) User interface; 2) ANNs prediction models software; and 3) GA engine software. The validation of the proposed system is carried out by comparing the results obtained from the system with the trial batches. The results indicate that the proposed system can be used to enable the design of HPC mix which corresponds to its required performance. Furthermore, the proposed system takes into account the influence of the fluctuating unit price of materials in order to achieve the lowest cost of concrete, which cannot be easily obtained by traditional methods or trial-and-error techniques.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.3
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• pp.373-380
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• 2018

The small coastal vessel registered in Korea, small coastal vessels with a gross tonnage of 10 tons or less account for 94.6 % and among them, aged vessels over 16 years age indicate 40.6 %. In order to reduce GHG emissions from small coast vessels, discussions are underway to replace aging ships' propulsion units with eco - friendly propulsion facilities, and the electric propulsion ship is emerging as one of the measures. The electric propulsion system using the DFE rectifier, which was applied in the conventional large commercial vessel, was effective in reducing the harmonics and improving the DC output voltage of the DC link stage, but it occupied a large volume and caused an increase in the overall system price. Therefore, in this paper, we propose an electric propulsion system using AFE rectifier with a small volume of system that can be applied to a small coastal vessel. In order to analyze the effectiveness of the overall system, the load profile was applied to obtain accurate and rapid speed tracking performance of the propulsion motor affected by the speed load. In addition, the power factor and total harmonic distortion factor of the voltage and current on the improved power output side are derived through simulation.

• Journal of Biomedical Engineering Research
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• v.30 no.2
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• pp.153-161
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• 2009

Mammogram is one of the important techniques for mass detection, which is the early diagnosis stage of a breast cancer. Especially, the CAD(Computer Aided Diagnosis) using mammogram improves the working performance of radiologists as it offers an effective mass detection. There are two types of CAD systems using mammogram; automatic and semi-automatic CAD systems. However, the automatic segmentation is limited in performance due to the difficulty of obtaining an accurate segmentation since mass occurs in the dense areas of the breast tissue and has smoother boundaries. Semi-automatic CAD systems overcome these limitations, however, they also have problems including high FP (False Positive) rate and a large amount of training data required for training a classifier. The proposed system which overcomes the aforementioned problems to detect mass is composed of the suspected area selection, the level set segmentation and SVM (Support Vector Machine) classification. To assess the efficacy of the system, 60 test images from the FFDM (Full-Field Digital Mammography) are analyzed and compared with the previous semi-automatic system, which uses the ANN classifier. The experimental results of the proposed system indicate higher accuracy of detecting mass in comparison to the previous systems.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1998.10a
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• pp.28-31
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• 1998

This paper describes the differences of the information system's success factors to improve the end-user's performance according to the job characteristics. A modified model of DeLone and McLean's IS success model is proposed with the two added variables of the top management concern and the IS department support. The model is validated using data collected from a field study of 3872 users on 3 Korean companies. ANOVA, correlation analysis, and stepwise regression are used to test research hypotheses. The results of the study indicate the following implications. First the top management concern and the IS department support have the significant relation with the system usage and the user satisfaction. Second, the system quality has an influence on the user satisfaction more than on the system usage. And the information quality has an influence on the system usage more than on the user satisfaction. Third, the system usage has more relations to the user's performance in the logistics function and R&D function. The user satisfaction has more relations to the user's performance in the sales and the A/S function. Therefore information system strategy to increase the user's performance must be differentiated according to job characteristics.

• Journal of the Korean Solar Energy Society
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• v.30 no.4
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• pp.22-28
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• 2010

This study analyzed the performance of passive solar system for office building. A unit model of the passive solar system was proposed in order to predict its performance under varying parameters and Seoul weather date. Steady state heat transfer equations were set up using a energy balanced equations and solved using a inverse matrix method. Numerical simulation program to analyze system was developed by using MATLAB. As the results, the passive solar system performance of office building was determined by the insolation and the outdoor air temperature. Also the passive solar system indicate 6.7~16.2% of annual average efficiency. In the comparison with other systems of the conventional wall, mass wall could reduce the heating loads of 7.1% and trombe wall could reduce heating loads of 11.5%. Through this study, performance of passive solar system for office building was verified by numerical method. Consequently, the passive solar system could operate an important role as the alternative for saving energy consumption of office building, and the additional studies should be made through the experimental method for the commercialization.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.558-569
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• 2007

It is important to obtain real-time data from long-term monitoring of landfills and develop leachate leakage detection system for the integrated management of landfills. A novel real time monitoring system and early leakage detection system was suggested in this study. The suggested monitoring system is composed of two parts; (1) a set of moisture sensors which monitor the areas surrounding the landfill, and (2) a set of moisture and temperature sensors which monitor the landfill inside. For the assessment for landfills stabilization, real-time monitoring system was evaluated in dry and wet cell of pilot-site. In addition, the grid-net electrical conductivity measurement system was also suggested as early leakage detection system. In this study, the field applicability of suggested systems was evaluated through pilot-scale field tests. The results of pilot-scale field model tests indicate that the grid-net electrical conductivity measurement method can be applicable to the detection of landfill leachate at the initial stage of intrusion, and thus has a potential for monitoring leachate leakage at waste landfills.

• Smart Structures and Systems
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• v.25 no.5
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• pp.543-557
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• 2020

This paper presents a series of experimental and numerical investigations on a vertical isolation system with quasi-zero stiffness (QZS) property. The isolation system comprises a linear helical spring and disk spring. The disk spring is designed to provide variable stiffness to the system. Orthogonal static tests with different design parameters are conducted to verify the mathematical and mechanical models of the isolation system. The deviations between theoretical and test results influenced by the design parameters are summarized. Then, the dynamic tests for the systems with different under-load degrees are performed, including the fast sweeping tests, harmonic excitation tests, and half-sine impact tests. The displacement transmissibility, vibration reduction rate, and free vibration response are calculated. Based on the test results, the variation of the transmission rule is evaluated and the damping magnitudes and types are identified. In addition, the relevant numerical time history responses are calculated considering the nonlinear behavior of the system. The results indicate that the QZS isolation system has a satisfactory isolation effect, while a higher damping level can potentially promote the isolation performance in the low-frequency range. It is also proved that the numerical calculation method accurately predicts the transmission character of the isolation system.

• International Journal of Aerospace System Engineering
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• v.2 no.2
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• pp.29-33
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• 2015

The multidisciplinary design optimization (MDO) of a launch vehicle (LV) with a hybrid rocket engine (HRE) was carried out to investigate the ability of an HRE for a single-stage LV. The non-dominated sorting genetic algorithm-II (NSGA-II) was employed to solve two design problems. The design problems were formulated as two-objective cases involving maximization of the downrange distance over the target flight altitude and minimization of the gross weight, for two target altitudes: 50.0 km and 100.0 km. Each objective function was empirically estimated. Several non-dominated solutions were obtained using the NSGA-II for each design problem, and in each case, a trade-off was observed between the two objective functions. The results for the two design problem indicate that economical performance of the LV is limited with the HRE in terms of the maximum downrange distances achievable. The LV geometries determined from the non-dominated solutions were examined.

• The Journal of Society for e-Business Studies
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• v.19 no.1
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• pp.1-14
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• 2014

This paper presents the development of a stock control system of POP system design based on RFID in SCM and its economic efficiency. A stock control system is proposed for 900MHz passive type RFID system. The RFID system is composed of a RFID reader and four antennas to read the tag IDs. A cost estimation model is adapted based on the total product profit by various tag prices. The result of the economic efficiency analysis can indicate any invested model for the automation system which have initial investment should be used. This solution indicates the limit of the break even point according to the input. And it can be concluded that the stock control can be developed by RFID readers and passive tags with directional arrangement of several antennas. Also, the economical evaluation model can be a decision method for company to adapt the new developed system.

• Journal of the Korean Society of Earth Science Education
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• v.3 no.1
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• pp.1-8
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• 2010

The purpose of this study was to analysis the 6th students' conceptions of the nature phenomenon focused on the systematic characteristics. For this study, 12 students of the 6th grades participated in special class for testing their conceptions about the water cycle in the earth system. And we analyzed the outcomes of students' conceptions based on SBF conceptual representation. The results indicate that most of the subjects perceived that the water cycle in earth system wasn't complex system maintaining its existence and functions as a whole through the interaction of its parts but simple system maintaining some actions between atmosphere and hydrosphere, geosphere, biosphere(biological world). And they didn't perceive the characteristics of the water cycle whose all parts must be presented the change of volume between vapor and water, glacier proposing the total hydro-volume are established in the earth system. Based on the results, it was suggested that the main goals of the schools' science education should be to provide students who understand the water cycle system as attaching importance to form with the skills needed to coherent understanding of the essential qualities for the nature phenomenon system.