• Structural Engineering and Mechanics
• /
• v.10 no.2
• /
• pp.139-156
• /
• 2000

This paper concerns the development of a computational model for the damage evolution of engineering materials under dynamic loading. Two models describing the anisotropic damage evolution of a material are presented; the first is based on a power function of the effective equivalent stress and the second on the damage strain energy release rate. The methods for computing the damage accumulated in structural components and their implementation in a finite element programme are presented together with some numerical results. The dynamic response of a damaged structural component and the dynamic behaviour of a damaged material have been studied numerically. This study shows that the frequency spectrum of a damaged structure is down-shifted, while the damping ratio of damaged materials becomes higher, the amplitude of the response significantly increases and the resonance ensuing from the damage growth still occurs in a damaged structure.

• Journal of the Architectural Institute of Korea Planning & Design
• /
• v.35 no.3
• /
• pp.49-58
• /
• 2019

The aged small-sized apartment housing threats the safety and comfort of the residents. It is excluded from the scope of mandatory management under the Article 34 of the "Apartment Housing Management Act". According to various domestic statistics, the number of small-sized apartment housing is 261,203, which is about 66% of the total 396,076 residences in Korea, so it is urgent to formulate a systematic management plan including remodeling. However, support programs for old-aged small-sized apartment housing of the central government and local governments are not enough to solve the problems. This study aims to propose useful policy ideas to promote remodeling for small-sized apartment housing based on the analysis on the housing status in our country. The first suggestion is the diversification of government programs. Second is the development of remodeling industry technology, and third is a complement of the law about the remodeling of small-sized apartment housing.

• Computers and Concrete
• /
• v.8 no.5
• /
• pp.511-524
• /
• 2011

Although concrete is believed to be a durable material, concrete structures have been degraded by severe environmental conditions such as the effects of chloride and chemical, abrasion, and other deterioration processes. Therefore, durability evaluation has been required to ensure the long term serviceability of structures located in chloride exposed environments. Recently, probability-based durability analysis and design have proven to be reliable for the service-life predictions of concrete structures. This approach has been successfully applied to durability estimation and design of concrete structures. However, currently it is difficult to find an appropriate method engineers can use to solve these probability-based diffusion problems. In this paper, computer software has been developed to facilitate probability-based durability analysis and design. This software predict the chloride diffusion using the Monte Carlo simulation method based on Fick's second law, and provides durability analysis and design solutions. A graphic user interface (GUI) is adapted for intuitive and easy use. The developed software is very useful not only for prediction of the service life but for the durability design of the concrete structures exposed to chloride environments.

• Journal of the Korean Society of Combustion
• /
• v.15 no.2
• /
• pp.1-11
• /
• 2010

Power generation systems based on the oxy-coal combustion with carbon dioxide capture and storage (CCS) capability are being proposed and discussed lately. Although a large number of lab scale studies for oxy-coal power plant have been made, studies of pilot scale or commercial scale power plant are not enough. Only a few demonstration projects for oxy-coal power plant are publicized recently. The proposed systems are evolving and various alternatives are to be comparatively evaluated. This paper presents a proposed approach for performance evaluation of a commercial 100 MWe class power plant, which is currently being considered for 'retrofitting' for the demonstration of the concept. The system is configurated based on design and operating conditions with proper assumptions. System components to be included in the discussion are listed. Evaluation criteria in terms of performance are summarized based on the system heat and mass balance and simple performance parameters, such as the fuel to power efficiency and brief introduction of the second law analysis. Also, gas composition is identified for additional analysis to impurities in the system including the purity of oxygen and unwanted gaseous components of nitrogen, argon and oxygen in air separation unit and $CO_2$ processing unit.

• Journal of Engineering Education Research
• /
• v.4 no.2
• /
• pp.45-56
• /
• 2001

This paper is aimed to design for qualification structure and contents of Electronic Commerce Manager which was executed in the second half year of the 2000. To obtain research object. An analysis about e-business law was studied. Also experts of education and related field performed job analysis, on the basis of this study qualification structure and contents of Electronic Commerce Manager was designed and suggestions are proposed for the substantiality and activity. This research is performed through literature review, expert association, interview, and job analysis.

• Macromolecular Research
• /
• v.14 no.5
• /
• pp.491-498
• /
• 2006

The thermal degradation of poly(hexamethylene guanidine) phosphate (PHMG) was studied by dynamic thermogravimetric analysis (TGA) and pyrolysis-GC/MS (p-GC). Thermal degradation of PHMG occurs in three different processes, such as dephosphorylation, sublimation/vaporization of amine compounds and decomposition/ recombination of hydrocarbon residues. The kinetic parameters of each stage were calculated from the Kissinger, Friedman and Flynn-Wall-Ozawa methods. The Chang method was also used for comparison study. To investigate the degradation mechanisms of the three different stages, the Coats-Redfern and the Phadnis-Deshpande methods were employed. The probable degradation mechanism for the first stage was a nucleation and growth mechanism, $A_n$ type. However, a power law and a diffusion mechanism, $D_n$ type, were operated for the second degradation stage, whereas a nucleation and growth mechanism, $A_n$ type, were operated again for the third degradation stage of PHMG. The theoretical weight loss against temperature curves, calculated by the estimated kinetic parameters, well fit the experimental data, thereby confirming the validity of the analysis method used in this work. The life-time predicted from the kinetic equation is a valuable guide for the thermal processing of PHMG.

• Journal of the Korean Society of Safety
• /
• v.22 no.3 s.81
• /
• pp.51-56
• /
• 2007

In recent years, many research works have been carried out in order to obtain a more controlled durability and long-term performance of concrete structures in chloride containing environments. In particular, the development of new procedures for probability-based durability analysis/design has proved to be very valuable. Although there is still a lack of relevant data, this approach has been successfully applied to some new concrete structures. In this paper, the equation used for modelling of the chloride penetration was based on Fick's Second Law of Diffusion in combination with a time dependent diffusion coefficient. The probability analysis of the durability performance was performed by use of a Monte Carlo Simulation. The procedure was applied to an example based on limited data gathered in this country. The influences of each parameter on the durability of concrete structures are studied and some comments for durability design are given. The new procedure may be very useful in designing an important concrete structures in chloride containing environments. Also it may help to predict the service life of concrete structures under a given probability of failure.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.13 no.4
• /
• pp.45-54
• /
• 2009

An exergy analysis is carried out for the regenerative steam-injection gas turbine systems which has a potential of enhanced thermal efficiency and specific power. Using the analysis model in the view of the second law of thermodynamics, the effects of pressure ratio, steam injection ratio, ambient temperature and turbine inlet temperature are investigated on the performance of the system such as exergetic efficiency, heat recovery ratio of heat exchangers, exergy destruction, loss ratios, and on the optimal conditions for maximum exergy efficiency. The results of computation show that the regenerative steam-injection gas turbine system can make a notable enhancement of exergy efficiency and reduce irreversibilities of the system.

• The Korean Journal of Emergency Medical Services
• /
• v.25 no.2
• /
• pp.113-128
• /
• 2021

Purpose: This study sought to analyze perceptions and attitudes regarding patient personal information protection according to the general characteristics of paramedic students and their clinical practice experience. Methods: A total of 215 paramedic students from G university in I metropolitan city and D university in G do were surveyed. Frequency analysis, percentage analysis, and one-way distribution analysis were conducted using the software SPSS version 23.0. Results: First, recognition regarding the operation of laws and systems related to medical law and personal information protection was high among students who had no clinical practice experience, and there were no differences with regard to students' general characteristics. Second, the level of recognition regarding patient personal information protection and exposure did not differ depending on students' general characteristics and clinical practice experience. Conclusion: Based on the results of this study, students' recognition and attitude should be improved by carrying out continuous education on patient personal information protection. Furthermore, more specialized and systematic training related to patient personal information protection should be conducted to nurture appropriately trained paramedic students.

• Nuclear Engineering and Technology
• /
• v.52 no.12
• /
• pp.2928-2938
• /
• 2020

A light water nuclear Reactor has been exergy analyzed, and the rate of irreversible exergy loss and exergy destruction is calculated for each of its components. The ratio of these losses compared to the total input exergy loss is calculated, which shows that most irreversible losses occur in the reactors, turbines, steam generators, respectively, as well as in the downstream operations. The main aim of this paper is to optimize the power plant using an innovative firefly algorithm and then to propose a novel strategy to improve the overall performance of the plant. As shown in the results, the exergy destruction rate of the plant decreased by 1.18% using the firefly method, and the exergy efficiency of the plant reached 29.3% comparing to the operational amount of 28.99%. Also, the results of the firefly optimization process compared to the Genetic algorithm and gravitational search algorithm to study the accuracy of the model for exergy analysis fitness problems in the power plants and the results of this comparison has shown that the results are nearly similar in the mentioned methods. However, the firefly is faster and more accurate in limited iterations.