• Structural Engineering and Mechanics
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• v.52 no.2
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• pp.351-368
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• 2014

This study presents a hunting search based optimum design algorithm for engineering optimization problems. Hunting search algorithm is an optimum design method inspired by group hunting of animals such as wolves, lions, and dolphins. Each of these hunters employs hunting in a different way. However, they are common in that all of them search for a prey in a group. Hunters encircle the prey and the ring of siege is tightened gradually until it is caught. Hunting search algorithm is employed for the automation of optimum design process, during which the design variables are selected for the minimum objective function value controlled by the design restrictions. Three different examples, namely welded beam, cellular beam and moment resisting steel frame are selected as numerical design problems and solved for the optimum solution. Each example differs in the following ways: Unlike welded beam design problem having continuous design variables, steel frame and cellular beam design problems include discrete design variables. Moreover, while the cellular beam is designed under the provisions of BS 5960, LRFD-AISC (Load and Resistant Factor Design-American Institute of Steel Construction) is considered for the formulation of moment resisting steel frame. Levy Flights is adapted to the simple hunting search algorithm for better search. For comparison, same design examples are also solved by using some other well-known search methods in the literature. Results reveal that hunting search shows good performance in finding optimum solutions for each design problem.

• Structural Engineering and Mechanics
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• v.11 no.3
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• pp.237-258
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• 2001

Structural identification via modal analysis in structural mechanics is gaining popularity in recent years, despite conceptual difficulties connected with its use. This paper is devoted to illustrate both the capabilities and the indeterminacy characterizing structural identification problems even in quite simple instances, as well as the cautions that should be accordingly adopted. In particular, we discuss an application of an identification technique of variational type, based on the measurement of eigenfrequencies and mode shapes, to a steel frame with friction joints under various assembling conditions. Experience has suggested, so as to restrict the indeterminacy frequently affecting identification issues, having resort to all the a priori acknowledged information on the system, to the symmetry and presence of structural elements with equal stiffness, to mention one example, and mindfully selecting the parameters to be identified. In addition, considering that the identification techniques have a local character and correspond to the updating of a preliminary model of the structure, it is important that the analytical model on the first attempt should be adequately accurate. Secondly, it has proved determinant to cross the results of the dynamic identification with tests of other typology, for instance, static tests, so as to fully understand the structural behavior and avoid the indeterminacy due to the nonuniqueness of the inverse problem.

• Structural Engineering and Mechanics
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• v.75 no.3
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• pp.389-399
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• 2020

An infill wall made of high-performance fiber-reinforced cementitious composites (HPFRCC) was utilized in this study to strengthen the reinforced concrete (RC) frame structures that had not been designed for seismic loads. The seismic performance of the RC frame structures strengthened by the HPFRCC infill walls was investigated through the experimental tests, and the test results showed that they have improved strength and deformation capabilities compared to that strengthened by the RC infill wall. A simple numerical modeling method, called the modified longitudinal and diagonal line element model (LDLEM), was introduced to consider the seismic strengthening effect of the infill walls, in which a section aggregator approach was also utilized to reflect the effect of shear in the column members of the RC frames. The proposed model showed accurate estimations on the strength, stiffness, and failure modes of the test specimens strengthened by the infill walls with and without fibers.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.565-575
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• 1998

This study presents overall process for designing and constructing a prestressed frame overpass using temporary piers. For the purpose of automating the design process, this study presents a computer program. According to the effective span(20m, 25m, 30m, 35m, 40m, 45m), this study performed parametric analysis and eventually presented appropriate cross section and compared this cross section with that of the existing simple steel overpass in girder height and quantify of the steel. $26{\sim}48%$ for gilder height and $25{\sim}34%$ for quantify of the steel are reduced as the result of study for span length $20{\sim}45m$. As long as the span length. the reduction rate was large.

• Journal of Intelligence and Information Systems
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• v.5 no.1
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• pp.13-34
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• 1999

Building a knowledge base effectively has been an important research area in the expert systems field. A variety of approaches have been studied including rules, semantic networks, and frames to represent the knowledge base for expert systems. As the size and complexity of the knowledge base get larger and more complicated, the integration of knowledge based with database technology cecomes more important to process the large amount of data. However, relational database management systems show many limitations in handing the complicated human knowledge due to its simple two dimensional table structure. In this paper, we propose Object-Oriented Knowledge Store (OOKS), a knowledge base model on the basis of a frame sturcture using an object-oriented database. In the proposed model, managing rules for inferencing and facts about objects in one uniform structure, knowledge and data can be tightly coupled and the performance of reasoning can be improved. For building a knowledge base, a knowledge script file representing rules and facts is used and the script file is transferred into a frame structure in database systems. Specifically, designing a frame structure in the database model as it is, it can facilitate management and utilization of knowledge in expert systems. To test the appropriateness of the proposed knowledge base model, a prototype system has been developed using a commercial ODBMS called ObjectStore and C++ programming language.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.3
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• pp.350-359
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• 2017

This paper presents a new holistic development approach for the carbon continuous-fiber composite frame of an automotive sunroof assembly. The original steel frame has been designed to get higher bending stiffness with its corrugated cross-sectional shape. The new approach uses the prepregs of a fast cure epoxy and PCM manufacturing processing. For higher productivity, the new frames feature a very simple plat cross sectional shape but achieve high bending stiffness through the laminate design. The sandwich structure with a PET foam core was presented. The frames were made of carbon UD laminae covered single carbon fabric on the outer surfaces. The fabrics provide torsional stiffness and also hold the carbon UD fibers floating in the low viscous epoxy resin of prepregs at the curing temperature during processing. The final product yields approximately 18 % savings in weight compared with the original.

• Steel and Composite Structures
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• v.15 no.4
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• pp.357-377
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• 2013

In order to study the degradation and damage behaviors of steel frame welded connections, two series of tests in references with different connection constructions were carried out subjected to various cyclic loading patterns. Hysteretic curves, degradation and damage behaviours and fatigue properties of specimens were firstly studied. Typical failure modes and probable damage reasons were discussed. Then, various damage index models with variables of dissipative energy, cumulative displacement and combined energy and displacement were summarized and applied for all experimental specimens. The damage developing curves of ten damage index models for each connection were obtained. Finally, the predicted and evaluated capacities of damage index models were compared in order to describe the degraded performance and failure modes. The characteristics of each damage index model were discussed in depth, and then their distributive laws were summarized. The tests and analysis results showed that the loading histories significantly affected the distributive shapes of damage index models. Different models had their own ranges of application. The selected parameters of damage index models had great effect on the developing trends of damage curves. The model with only displacement variable was recommended because of a more simple form and no integral calculation, which was easier to be formulated and embedded in application programs.

• Journal of Power Electronics
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• v.17 no.1
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• pp.181-189
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• 2017

The three-phase four-leg voltage-source inverter topology is an interesting option for the three-phase four-wire system. With an additional leg, this topology can achieve superior performance under unbalanced and nonlinear load conditions. However, because of the low bandwidth of conventional controllers in high-power inverter applications, the system cannot guarantee a balanced output voltage under the unbalanced load condition. Most of the methods proposed to solve this problem mainly use the multiple synchronous frame method, which requires several controllers and a large amount of computation because of frame transformation. This study proposes a simple hybrid controller that combines proportional-integral (PI) and resonant controllers in the synchronous frame synchronized with the positive-sequence component of the output voltage of the three-phase four-leg inverter. The design procedure for the controller and the theoretical analysis are presented. The performance of the proposed method is verified by the experimental results and compared with that of the conventional PI controller.

• Journal of Communications and Networks
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• v.12 no.6
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• pp.582-591
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• 2010

Probabilistic modeling and analysis of correlation metrics have been receiving considerable interest for a long period of time because they can be used to evaluate the performance of communication receivers, including satellite broadcasting receivers. Although differential correlators have a simple structure and practical importance over channels with severe frequency offsets, closedform expressions for the output distribution of differential correlators do not exist. In this paper, we present detection error probability expressions for frame synchronization using differential correlation, and demonstrate their accuracy over channel parameters of practical interest. The derived formulas are presented in terms of the Marcum Q-function, and do not involve numerical integration, unlike the formulas derived in some previous studies. We first determine the distributions and error probabilities for single-span differential correlation metric, and then extend the result to multispan differential correlation metric with certain approximations. The results can be used for the performance analysis of various detection strategies that utilize the differential correlation structure.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.806-811
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• 2006

In RFID system, when multiple tags respond simultaneously, a collision can occur. A method that solves this collision is referred to as anti-collision algorithm. Among the existing anti-collision algorithms, SFSA, though simple, has a disadvantage that when the number of tags is variable, the system performance degrades because of the fixed frame size. This paper proposes a new anti-collision algorithm called DFSA which determines the optimal frame size using the number of collided slots at every frame. According to the simulation results, the tag identification time of the proposed algorithm is faster than that of SFSA.