• Computational Structural Engineering
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• v.9 no.4
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• pp.117-126
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• 1996

Damage detection methods using structural tests can be divided into two methods, i.e., static and dynamic. The static methods which use the stiffness properties of the structure are simpler than the dynamic methods. However, static approaches are very sensitive to the displacement measurement noises and modeling errors. The dynamic methods also have limitations in acquiring the natural frequencies and mode shapes of the high frequencies. In this study, a method for the structural damage assessment using sensitivity matrices is developed, in which the drawbacks of the static and dynamic methods can be compensated. Based on the measurement data for the static displacements and dynamic modal properties, the damage locations and the degree of damage are determined using the presented sensitivity matrix method. The efficiency of the proposed method has been examined through numerical simulation studies on truss type structures.

• Journal of the Korean School Mathematics Society
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• v.15 no.1
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• pp.53-80
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• 2012

This study was designed to find the characteristics of mathematical errors and discourse in simultaneous equations and inequalities for migrant students from North Korea. 5 sample students participated, who attended in an alternative school for the migrant students from North Korea at the study in Seoul, Korea. A total of 8 lesson units were performed as an extra curriculum activity once a week during the 1st semester, 2011. The results indicated that students showed technical errors, encoding errors, misunderstood symbols, misinterpreted language, and misunderstood Chines characters of Koreans and the discourse levels improved from the zero level to the third level, but the scenes of the third level did not constantly happen. Nevertheless, the components of discourse, explanation & justification, were activated and as a result, evaluation & elaboration increased in ERE pattern on communication.

• Journal of Korean Society of Transportation
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• v.24 no.2 s.88
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• pp.169-178
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• 2006

Traffic assignment has been used both for predicting travel demands and for evaluating the tools for alleviating congestion on road network in advance. Some assignment models have been proposed such as equivalent mathematical minimization method, variational inequality problem, nonlinear complementary problem and fixed point method, in following the principle of Wardrop (1952) that no driver can not Improve his travel cost by unilaterally changing his route. Recently Jin(2005a) presented a traffic assignment model based on dynamic process. This paper proposes a solution algorithm for the model of Jin and assesses the performances. Compared to the Frank-Wolfe method, which has been wildly used for solving the existing assignment models, the proposed algorithm is expected to be more efficient because it does not need to evaluate the objective function. Two numerical examples are used for assessing the algorithm, and they show that the algorithm converges to user equilibrium of Wardrop.

• Journal of Elementary Mathematics Education in Korea
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• v.17 no.2
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• pp.207-223
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• 2013

Teachers unfold a series of timeless mathematical symbols such as 5+2=7 in time by verbalizing the symbols in classrooms. A number sentence 5+2=7 is read in Korean as '5 더하기 2는(five plus two) 7과(seven) 같다(equals). Unlike in English, 5+2 and 7 are read first before the equal sign in Korean. This sequence of reading in Korean conflicts with the conventional linguistic sequence of writing from left to right. Ways of resolving the discrepancy between reading and writing sequences can make a difference students' understanding of the equal sign. Students would be in danger of perceiving the equal sign as an operational symbol, if a teacher resolves the discrepancy by subordinating reading sequence to linguistic convention of writing. This way of resolving results in the undesired phenomenon of changing the reading expressions in Korean elementary math textbook which represent relational notion of the equal sign into other reading expressions that represent operational notion of it. For understanding of relational notion of the equal sign, the discrepancy should be resolved by changing writing sequence in accordance with reading sequence. In addition, teaching of verbalizing the equal sign should be integrated with teaching of verbalizing inequality signs.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.3
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• pp.183-190
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• 2002

This paper describes the synthesis of robust and non-fragile H$\infty$ state feedback controllers for linear varying systems with affine parameter uncertainties, and static state feedback controller with structured uncertainty. The sufficient condition of controller existence, the design method of robust and non-fragile H$\infty$ static state feedback controller, and the set of controllers which satisfies non-fragility are presented. The obtained condition can be rewritten as parameterized Linear Matrix Inequalities(PLMls), that is, LMIs whose coefficients are functions of a parameter confined to a compact set. However, in contrast to LMIs, PLMIs feasibility problems involve infinitely many LMIs hence are inherently difficult to solve numerically. Therefore PLMls are transformed into standard LMI problems using relaxation techniques relying on separated convexity concepts. We show that the resulting controller guarantees the asymptotic stability and disturbance attenuation of the closed loop system in spite of controller gain variations within a degree.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.159-169
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• 2010

A multiphysics model analysis including moisture transport, heat transfer and solid mechanics and experiments on the normal and light weight concrete were carried out in order to study the effect of preabsorbed water in the light weight aggregates on the drying and shrinkage characteristics of concrete. Consequently, with fixed water-cement ratio, loss of water content of normal and light weight concrete were compared and the results showed that the lightweight concrete lost less moist than the normal concrete in early age and long term which was by moist supply effect. Accordingly, shrinkage strain size and distribution of lightweight concrete were decreased, and shrinkage reducing effect was efficient in early age with water cement ratio 0.3 and in both early age, and long term with water cement ratio 0.5. The comparison of analysis results and exaperimental results indicate that characteristic values of moisture transport and the relation humidity and shrinkage strain from this study are resonable for application for other differential shrinkage analysis in lightweight concrete.

• Journal of the Korean GEO-environmental Society
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• v.13 no.4
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• pp.77-91
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• 2012

Recently, construction of housing sites, complexes, roads, ports and airports is increasing for high-intensity use of the country and balanced development between regions. Presently, constructions are being conducted at soft ground. Consequently, engineering problems as long-term settlement of the ground, differential settlement, local structural damage have been reported consistently at construction site. In particular, long-term subsidence of the ground as various constructions and loads by the load will necessarily occur in the soft ground of west-south coast and inland coast. Therefore, in this study, regional proper analysis methods of the Hyperbole method, Hosino method, $\sqrt{S}$ method, Asaoka method etc as existing long-term settlement prediction methods have been examined and a study on new prediction method was conducted through deduction of a generalized equation. Correlation coefficients of soil properties and construction conditions has been analyzed and a matching coefficient of long-term settlement characteristics has been deducted. Comparison and analysis of monitoring data and numerical analysis results of 16 local area have been conducted.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.5
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• pp.549-554
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• 2012

In this paper, we consider the optimal fuzzy filter of nonlinear discrete-time with estimation error variance constraint. First, the Takagi and Sugeno(T-S) fuzzy model is employed to approximate the nonlinear system. Next, the error state is mean square bounded, and the steady state variance of the estimation error of each state is not more than the individual predefined value. It is shown that, the addressed problem can be carried out by solving linear matrix inequality(LMI) and some algebraic quadratic matrix inequalities. Finally, some examples are provided to illustrate the design procedure and expected performance through simulations.

• Journal of the Korean Geosynthetics Society
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• v.10 no.1
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• pp.1-8
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• 2011

The problems like a deterioration of loading bearing capacity, an exaggeration of settlement and lateral deformation are able to be generated, meanwhile structures are built in soft ground. Top-Base method is belonged to a rigidity mat foundation method which is used to surface treatment of soft ground. This method makes an effect to increase the bearing capacity of foundation using friction force, and prevent the differential settlement. Further more, the In-Situ Top-Base method has advantages in the phase of economic effect by reduction of the construction cost and offers an expediency on construction comparing with precast products. This paper presents the way of the estimation of bearing capacity for In-Situ Top-Base method through field plate load test in soft ground. It utilizes the results to a future design by analyzing the properties in the existing study and designs through these analysis and calculating the top-base method's reasonable range.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.2
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• pp.99-105
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• 1991

This study was carried out to provide basic data to be necessary for the selection of an energy recovery process based on the characteristics of municipal solid wastes(MSW). The samples were collected at Kangdong-Ku in Seoul and conducted ultimate and proximate analyses. Laboratory scale anaerobic digesters were operated to determine the non biodegradable fractions of the wastes. The results indicated that carbon and hydrogen contents, and lower heating values could be calculated from the volatile contents of MSW by the following equations : C = 0.57 VS, H =0.084 VS, and HL=49.5 VS-(6-0.045VS) W. Nonbiodegradable fractions were respectively 58.9% of volatile matters and 77.7% of MSW. Incineration and refuse derived fuel(RDF) processes appeared to be the most efficient processes in terms of weight reduction and energy recovery, But determining the energy recovery processes, the fluctuations of heating values of MSW throughout a year and available landfill site and secondary pollution should be considered.