• Smart Structures and Systems
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• v.18 no.3
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• pp.569-584
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• 2016

This paper presents a method for stochastic modelling of fatigue crack growth and optimising inspection and maintenance strategy for the structural members of steel bridges. The fatigue crack evolution is considered as a stochastic process with uncertainties, and the Gamma process is adopted to simulate the propagation of fatigue crack in steel bridge members. From the stochastic modelling for fatigue crack growth, the probability of failure caused by fatigue is predicted over the service life of steel bridge members. The remaining fatigue life of steel bridge members is determined by comparing the fatigue crack length with its predetermined threshold. Furthermore, the probability of detection is adopted to consider the uncertainties in detecting fatigue crack by using existing damage detection techniques. A multi-objective optimisation problem is proposed and solved by a genetic algorithm to determine the optimised inspection and maintenance strategy for the fatigue affected steel bridge members. The optimised strategy is achieved by minimizing the life-cycle cost, including the inspection, maintenance and failure costs, and maximizing the service life after necessary intervention. The number of intervention during the service life is also taken into account to investigate the relationship between the service life and the cost for maintenance. The results from numerical examples show that the proposed method can provide a useful approach for cost-effective inspection and maintenance strategy for fatigue affected steel bridges.

• Structural Engineering and Mechanics
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• v.63 no.6
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• pp.703-712
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• 2017

The composite blades of offshore wind turbines accumulate structural damage such as fatigue cracking due to harsh operation environments during their service time, leading to premature structural failures. This paper investigates various fatigue crack models for reproducing crack development in composite blades and proposes a stochastic approach to predict fatigue crack evolution and to analyse failure probability for the composite blades. Three typical fatigue models for the propagation of fatigue cracks, i.e., Miner model, Paris model and Reifsnider model, are discussed to reproduce the fatigue crack evolution in composite blades subjected to cyclical loadings. The lifetime probability of fatigue failure of the composite blades is estimated by stochastic deterioration modelling such as gamma process. Based on time-dependent reliability analysis and lifecycle cost analysis, an optimised maintenance policy is determined to make the optimal decision for the composite blades during the service time. A numerical example is employed to investigate the effectiveness of predicting fatigue crack growth, estimating the probability of fatigue failure and evaluating an optimal maintenance policy. The results from the numerical study show that the stochastic gamma process together with the proper fatigue models can provide a useful tool for remaining useful life predictions and optimum maintenance strategies of the composite blades of offshore wind turbines.

• East Asian mathematical journal
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• v.36 no.2
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• pp.147-172
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• 2020

The purpose of this study is to provide to understand correctly for teachers and pre-service teachers who have the wrong conception of mathematical modeling. We present the differences modeling problems and general application problems to identify between general application and modeling problems. We propose the entire process from modeling tasks development to solve the problems of mathematical modeling. Additionally, the entire process of the possible solutions was concluded for the presented modeling problems. We proposed what students and teachers should perform at each stage of each phase of the modeling cycle. The concrete tasks were suggested for teachers and students at each phase of modeling cycles, with the specific role of the teacher in the overall process for students' modeling activities.

• The Mathematical Education
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• v.30 no.1
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• pp.1-19
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• 1991

This study intends to provide some desirable suggestions for the development of application oriented mathematics curriculum. More specific objects of this study is: 1. To identify the meaning of application and modelling in mathematics curriculm. 2. To illuminate the historical background of and trends in application and modelling in the mathematics curricula. 3. To consider the reasons for including application and modelling in the mathematics curriculum. 4. To find out some implication for developing application oriented mathematics curriculum. The meaning of application and modelling is clarified as follows: If an arbitrary area of extra-mathematical reality is submitted to any kind of treatment which invovles mathematical concepts, methods, results, topics, we shall speak of the process of applying mathemtaics to that area. For the result of the process we shall use the term an application of mathematics. Certain objects, relations between them, and structures belonging to the area under consideration are selected and translated into mathemtaical objects, relation and structures, which are said to represent the original ones. Now, the concept of mathematical model is defined as the collection of mathematical objcets, . relations, structures, and so on, irrespective of what area is being represented by the model and how. And the full process of constructing a mathematical model of a given area is called as modelling, or model-building. During the last few decades an enormous extension of the use of mathemtaics in other disciplines has occurred. Nowadays the concept of a mathematical model is often used and interest has turned to the dynamic interaction between the real world and mathematics, to the process translating a real situation into a mathematical model and vice versa. The continued growing importance of mathematics in everyday practice has not been reflected to the same extent in the teaching and learning of mathematics in school. In particular the world-wide 'New Maths Movement' of the 19608 actually caused a reduction of the importance of application and modelling in mathematics teaching. Eventually, in the 1970s, there was a reaction to the excessive formallism of 'New Maths', and a return in many countries to the importance of application and connections to the reality in mathematics teaching. However, the main emphasis was put on mathematical models. Applicaton and modelling should be part of the mathematics curriculum in order to: 1. Convince students, who lacks visible relevance to their present and future lives, that mathematical activities are worthwhile, and motivate their studies. 2. Assist the acqusition and understanding of mathematical ideas, concepts, methods, theories and provide illustrations and interpretations of them. 3. Prepare students for being able to practice application and modelling as private individuals or as citizens, at present or in the future. 4. Foster in students the ability to utilise mathematics in complex situations. Of these four reasons the first is rather defensive, serving to protect or strengthen the position of mathematics, whereas the last three imply a positive interest in application and modelling for their own sake or for their capacity to improve mathematics teaching. Suggestions, recomendations and implications for developing application oriented mathematics curriculum were made as follows: 1. Many applications and modelling case studies suitable for various levels should be investigated and published for the teacher. 2. Mathematics education both for general and vocational students should encompass application and modelling activities, of a constructive as well as analytical and critical nature. 3. Application and modelling activities should. be introduced in mathematics curriculum through the interdisciplinary integrated approach. 4. What are the central ideas of, and what are less-important topics of application-oriented curriculum should be studied and selected. 5. For any mathematics teacher, application and modelling should form part of pre- and in-service education.

• Journal of Digital Convergence
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• v.12 no.1
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• pp.149-161
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• 2014

According to the economic advancement, the position of service industry in GDP has increased. Development of service industry has solved the employment issue and derived the activation of the internal market. It has contributed to demand creation in health care, education, and culture, enhancing competition of the manufacturing industry and entire economic development. By the development of information communication technologies, improvement of the quality of life from those, and changes in the competitive environment, customers, from businesses and public agencies, or the customer's needs are increasing. In these circumstances, companies are operating non-face-to-face contact call center for the purpose to communicate with customers, handle customer complaints, attract and retain new customers. In this study, to improve the performance of the non-face-to-face contact call center, this study tried to derive the call center's 'Service Process Modeling' and future policy assignment by analyzing the problem from the research of the service and process summary, performance evaluation, call center evaluation and etc.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.10
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• pp.774-781
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• 1991

A communication network protocol among programable devices built-i manufacturing field, MAP (Manufacturing Automation Protocol), has to provide the job transfer service carrying out a lot of jobs distributively, and the MMS( manufacturing message specification) defines the above application layer protocol. In this paper user software required in job transfer was implemented. So as to provide each service with compatibility and extension, each module was designed according to the functions. A method is selected in double-assigning their domain and program applicable even in complex process, which loads and proceeds several programs sequentially. In order to confirm the logical validity of the designed protocol, local applying test is accomplished for the application layer of response station. Modelling the job flow process, each serice module is verified with the I/O primitives.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.1
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• pp.375-383
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• 2021

The justice issue in the service recovery process has become an interesting topic especially in rural banks in Indonesia. There are two types of justice issues in handling the complaint process; distributive and informational. This study aims to analyze the effect of distributive and informational justice on complaint handling satisfaction. This study also examines the mediating role of positive and negative emotions on the effect of justice in post-merger rural banks. This research employs a survey by distributing a questionnaire to 238 customers who have complained to one of the post-merger rural banks in West Java and Yogyakarta. This study uses the structural equation modelling (SEM) method by WarpPLS software. The results reveal that distributive and informational justice have a positive effect on positive and negative emotions, while informational justice does not affect positive and negative emotions. Distributive and informational justice directly affect satisfaction over complaint handling. On the other hand, positive and negative emotions affect satisfaction over complaint handling. The findings of this study suggest that positive emotion also mediates the distributive justice effect on satisfaction over complaint. Lastly, positive and negative emotions do not mediate the informational justice effect on satisfaction over complaint handling at post-merger rural banks in West Java and Yogyakarta, Indonesia.

• Structural Monitoring and Maintenance
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• v.2 no.2
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• pp.133-143
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• 2015

Civil engineering infrastructure is aging and requires cost-effective maintenance strategies to enable infrastructure systems operate reliably and sustainably. This paper presents an approach for determining risk-cost balanced repair strategy of corrosion damaged reinforced concrete structures with consideration of uncertainty in structural resistance deterioration. On the basis of analytical models of cover concrete cracking evolution and bond strength degradation due to reinforcement corrosion, the effect of reinforcement corrosion on residual load carrying capacity of corroded reinforced concrete structures is investigated. A stochastic deterioration model based on gamma process is adopted to evaluate the probability of failure of structural bearing capacity over the lifetime. Optimal repair planning and maintenance strategies during the service life are determined by balancing the cost for maintenance and the risk of structural failure. The method proposed in this study is then demonstrated by numerical investigations for a concrete structure subjected to reinforcement corrosion. The obtained results show that the proposed method can provide a risk cost optimised repair schedule during the service life of corroded concrete structures.

• Computers and Concrete
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• v.25 no.1
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• pp.67-73
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• 2020

Traditionally used analytical approach to predict the fatigue failure of reinforced concrete (RC) structure is generally conservative and has certain limitations. The nonlinear finite element method (FEM) offers less expensive solution for fatigue analysis with sufficient accuracy. However, the conventional implicit dynamic analysis is very expensive for high level computation. Whereas, an explicit dynamic analysis approach offers a computationally operative modelling to predict true responses of a structural element under periodic loading and might be perfectly matched to accomplish long life fatigue computations. Hence, this study simulates the fatigue behaviour of RC beams with finite element (FE) assemblage presenting a simplified explicit dynamic numerical solution to show computer aided fatigue behaviour of RC beam. A commercial FEM package, ABAQUS has been chosen for this complex modelling. The concrete has been modelled as a 8-node solid element providing competent compression hardening and tension stiffening. The steel reinforcements are simulated as two-node truss elements comprising elasto-plastic stress-strain behaviour. All the possible nonlinearities are duly incorporated. Time domain analysis has been adopted through an automatic Newmark-β time incremental technique. The program consists of twelve RC beams to visualize the real behaviour during fatigue process and to obtain the reliability of the study. Both the numerical and experimental results indicate a redistribution of stresses along the time and damage accumulation of beam which severely affect the serviceability and ultimate capacity of RC beam. The output of the FEM analysis demonstrates good match with the experimental consequences which affirm the efficacy of the computer aided model. The controlled fatigue damage evolution at service fatigue load limits makes the FE model an efficient tool in predicting high cycle fatigue behaviour of RC structures.

• ETRI Journal
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• v.5 no.2
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• pp.3-8
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• 1983

This paper derives the Markov model to calculate the reliability of the Digital Switching System being developed by KETRI. Using the failure states extracted from the system in the course of the modelling, we calculated the reliability of both the service grade and the function of the system. Especially, by including the repair rate into the model, we took optimum advantage of theMarkov process and solved the difficulties in the calculation by reducing the number of states of the system.