• Computers and Concrete
• /
• 제8권4호
• /
• pp.425-443
• /
• 2011

Most previous studies have generally overlooked the contribution of thermal stresses generated within the concrete mass when subjected to microwave heating and reported on pore-pressure as being the dominant cause of surface spalling. Also, the variation in electromagnetic properties of concrete and its effects on the microwave heating process have not been studied in detail. In this paper, finite element modeling is used to examine the simultaneous development of compressive thermal stresses and pore-pressure arising from the microwave heating of concrete. A modified Lambert's Law formulation is proposed to estimate the microwave power dissipation in the concrete mass. Moreover, the effects of frequency and concrete water content on the concrete heating rate and pattern are investigated. Results show high compressive stresses being generated especially in concrete with a high water content when heated by microwaves of higher frequencies. The results also reveal that the water content of concrete plays a crucial role in the microwave heating process.

• Journal of Power Electronics
• /
• 제11권2호
• /
• pp.163-172
• /
• 2011

Oxidation models of a rotor bar and end ring segment in an induction motor are presented to simulate the behavior of an induction machine working with oxidized rotor parts which are modeled as rotor faults in progress. The leakage inductance and resistance of the rotor parts arc different from normal values because of the oxidation process. The impedance variations modify the current density and magnetic flux which pass through the oxidized parts. Consequently, it causes the rotor asymmetry which induces abnormal harmonics in the stator current spectra of the faulty machine. The leakage inductances of the oxidation models are derived by the Ampere's law. Using the proposed oxidation models, the rotor bar and end ring faults in progress can be modeled and simulated with the motor current signature analysis (MCSA). In addition, the oxidation process of the rotor bar and end ring segment can motivate the rotor asymmetry, which is induced by electromagnetic imbalances, and it is one of the major motor faults. Results of simulations and experiments are compared to each other to verify the accuracy of the proposed models. Experiments are achieved using 3.7 kW, 3-phase, and squirrel cage induction motors with a motor drive inverter.

• 한국수자원학회논문집
• /
• 제30권5호
• /
• pp.495-501
• /
• 1997

펌프동력이 기지 값으로 주어져 있을 때, 유량이나 관경을 산정하는 경우 기존의 방법으로는 상당한 반복과정을 거쳐야 된다. 이에 유동훈과 강찬수(1996)는 균일조도 동력경사관인 경우 유량인 관경을 양해법으로 산정하는 식을 개발한 바 있다. 마찰계수 산정을 위한 지수함수식의 이용은 본 양해법 산정식의 개발을 가능하게 하였다. 유동훈(1995a)은 상용관이나 복합면을 가진 관의 마찰계수 산정을 위한 마찰계수 평균법을 제시한 바 있다. 그와 같은 접근방법으로 본고는 마찰계수 평균법을 상용관 마찰계수 산정식에 적용하여 동력경사 상용관의 유량이나 관경을 양해법으로 구할 수 있는 산정식을 개발하였다.

• Nuclear Engineering and Technology
• /
• 제52권12호
• /
• 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.

• Journal of Information Technology Applications and Management
• /
• 제23권4호
• /
• pp.117-125
• /
• 2016

Software reliability in the software development process is an important issue. In infinite failure non-homogeneous Poisson process software reliability models, the failure occurrence rates per fault. can be presented constant, monotonic increasing or monotonic decreasing pattern. In this paper, the reliability software cost model considering decreasing intensity function was studied in the software product testing process. The decreasing intensity function that can be widely used in the field of reliability using power law process, log-linear processes and Musal-Okumoto process were studied and the parameter estimation method was used for maximum likelihood estimation. In this paper, from the software model analysis, we was compared by applying a software failure interval failure data considering the decreasing intensity function The decreasing intensity function model is also efficient in terms of reliability in the arena of the conservative model can be used as an alternating model can be established. From this paper, the software developers have to consider life distribution by preceding information of the software to classify failure modes which can be gifted to support.

• 소성∙가공
• /
• 제18권1호
• /
• pp.26-38
• /
• 2009

It was reported that the semi-solid forming process has many advantages over the conventional forming process, such as a long die life, good mechanical properties and energy savings. It is very important, however, to control liquid segregation to gain mechanical property improvement of materials. During forming process, rheology material has complex characteristics, thixotropic behavior. Also, difference of velocity between solid and liquid in the semi-solid state material makes a liquid segregation and specific stress variation. Therefore, it is difficult for a numerical simulation of the rheology process to be performed. General plastic or fluid dynamic analysis is not suitable for the behavior of rheology material. The behavior and stress of solid particle in the rheology material during forging process is affected by viscosity, temperature and solid fraction. In this study, compression experiments of aluminum alloy were performed under each other tool shape which is rectangle shape(square array), rectangle shape(hexagonal array), and free shape tool. In addition, the dynamics behavior compare with Okano equation to power law model which is viscosity equation.

• 한국소음진동공학회논문집
• /
• 제18권3호
• /
• pp.323-334
• /
• 2008

According to the delivery condition, the breakage of a product occurs when it is delivered to the customers. Therefore product's makers evaluate the durability under the delivery process by accelerated life testing. In order to conduct this accelerated life testing accurately, it is very important to identify the acceleration-factor exactly between on-road and accelerated life test condition. In this paper, the acceleration-factor is identified by applying linear damage summation law, rain-flow cycle counting and Dirlik theory under the conditions of the random vibration. And approximated FEM model of the connecting-pipe to the compressor is developed for fatigue analysis. This model is finally verified by comparing the experiment results to the numerical analysis results.

• Journal of Electrical Engineering and Technology
• /
• 제13권6호
• /
• pp.2187-2195
• /
• 2018

In order to realize the multi-objective control of single-input multi-output nonlinear differential algebraic system (NDAS) and to improve the dynamic characteristics and static accuracy, a design method of nonlinear control with multi-objective feedback (NCMOF) is proposed, the principium of this method to arrange system poles, as well as its nature to coordinate dynamic characteristics and static accuracy of the system are analyzed in detail. Through NCMOF design method, the multi-objective control of the system is transformed into linear space, and then it is effectively controlled under the nonlinear feedback control law, the problem to balance all control objectives caused by less input and more output of the system thus is solved. Applying NCMOF design method to generator excitation system, the nonlinear excitation control law with terminal voltage, active power and rotor speed as objective outputs is designed. Simulation results show that NCMOF can not only improve the dynamic characteristics of generator, but also damp the mechanical oscillation of a generator in transient process. Moreover, NCMOF can control the terminal voltage of the generator to the setting value with no static error under typical disturbances.

• 무역상무연구
• /
• 제14권
• /
• pp.291-321
• /
• 2000

This study investigates the different pattern of trade negotiation between Korea and Japan. For the Korea, it is inevitable to enhance nation's competitiveness position amid the rapidly changed international environment. Especially, Korea's recent experience of IMF credit under economic crisis during 1997-1999 tells us the importance of international trade and trade negotiation. Our main interest is focused on the comparative pattern of both countries with the recognition that the role of the negotiation can not be overemphasized for the Korea. This is because Korea has continuously recorded the huge trade deficits with Japan for the long time. Although we consider the different degrees of products quality, industrial structure, productivity, and national competitiveness of both countries, it is necessarily required to pay special attention on different pattern of negotiation skills and tactics between two countries. In the paper, we suggest some important guidelines for Korea to improve its negotiation technique with Japan. First, valuing human relation between negotiators, rather than negotiating process. Second, preparing for negotiations: the negotiators should try to carve out enough time to prepare for the bargaining. Third, appreciating the power of patience: very essential to effective outputs. Fourth, being a specialist on both countries' culture and avoiding lawyers' intervention for conflict resolution.

• 무역상무연구
• /
• 제47권
• /
• pp.25-48
• /
• 2010

The principle of parties' autonomy is one of general and dominant principles in an international trade contract. When we consider the determinants of negotiation outcomes, the negotiation is affected its result by their culture and custom. A negotiation has extensively been used a lot as a business process. As we negotiate with our clients, we have to check a lot of factors like strategies, their behaviors, culture shock and custom. That why most people have their different life and circumstance. The same words which are used its contract have several meaning. Because the words are influenced by culture and own custom. Also most people abide by their social pattern. Each culture in the world follows its own customs and traditions. Therefore, when we have the negotiation of trade contract, we have to think these factors. Then the negotiation is leaded very successful This dissertation examines the effects of the negotiators' personality and different culture and custom. On the point of a negotiating power, contracting parties are affected a lot by their usage. The culture which is influenced by contracting parties is possible to apply as a key point. So, this study will be analyzed these factors.