• Journal of Digital Contents Society
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• v.7 no.4
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• pp.279-285
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• 2006

In this paper, we have considered the performance improvement of Multi-Carrier DS-CDMA system using hybrid SC/MRC-Lc/L diversity receiving technique over multipath fading environment and compared with that of a Wideband DS-CDMA system. In the result, the PBI has caused a performance deterioration over partial bandwidth in Multi-Carrier DS-CDMA system. Also, Multi-Carrier DS-CDMA system using Hybrid SC/MRC-Lc/L diversity received can determined the complexity and the performance vs the expenses for the system that select the number of input branches.

• International Journal of Computer Science & Network Security
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• v.22 no.6
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• pp.203-211
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• 2022

Multi-objective optimization problems (MOPs) arise in many real-world applications. MOPs involve two or more objectives with the aim to be optimized. With these problems improvement of one objective may led to deterioration of another. The primary goal of most multi-objective evolutionary algorithms (MOEA) is to generate a set of solutions for approximating the whole or part of the Pareto optimal front, which could provide decision makers a good insight to the problem. Over the last decades or so, several different and remarkable multi-objective evolutionary algorithms, have been developed with successful applications. However, MOEAs are still in their infancy. The objective of this research is to study how to use and apply machine learning (ML) to improve evolutionary multi-objective optimization (EMO). The EMO method is the multi-objective evolutionary algorithm based on decomposition (MOEA/D). The MOEA/D has become one of the most widely used algorithmic frameworks in the area of multi-objective evolutionary computation and won has won an international algorithm contest.

• Steel and Composite Structures
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• v.27 no.2
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• pp.229-242
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• 2018

High strength steel is widely used in industrial applications to improve the load-bearing capacity and reduce the overall weight and cost. To take advantage of the benefits of this type of steel in construction, an innovative hybrid fabricated member consisting of high strength steel tubes welded to mild steel plates has recently been developed. Component-scale uniaxial and multiaxial cyclic experiments have been conducted with simultaneous constant or varying axial compression loads using a multi-axial substructure testing facility. The structural interaction of high strength steel tubes with mild steel plates is investigated in terms of member capacity, strength and stiffness deterioration and the development of plastic hinges. The deterioration parameters of hybrid specimens are calibrated and compared against those of conventional steel specimens. Effect of varying axial force and loading direction on the hysteretic deterioration model, failure modes and axial shortening is also studied. Plate and tube elements in hybrid members interact such that the high strength steel is kept within its ultimate strain range to prevent sudden fracture due to its low ultimate to yield strain ratio while the ductile performance of plate governs the global failure mechanism. High strength material also significantly reduces the axial shortening in columns which prevents undesirable frame deformations.

• Journal of Environmental Impact Assessment
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• v.18 no.6
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• pp.367-376
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• 2009

This paper proposes an application methodology of AHP(Analytic Hierarchy Process) based decision making theory for improvement priority by assessment of various risk factors affecting on deterioration of water supply systems, as major social infrastructure. AHP method is organized with three level of hierarchy which is introduced for multi-criteria decision making in this study. In the first level, assessment outputs are calculated by AHP for each affecting factor. In the second level, criteria are estimated by using assessment results with respect to structural and environmental factors. Consequently, ranking decision is performed in the third level. In order to present the effectiveness, a proposed method is compared with FCP(Fuzzy Composite Programming) for decision making. Since the results of the proposed method show better performance with consistent results, it can be applied as an efficient information for the determination for improvement priority of the study infrastructure.

• Journal of Korean Neurosurgical Society
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• v.61 no.2
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• pp.224-232
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• 2018

Objective : Cervical ossification of the posterior longitudinal ligament (OPLL) can be treated via anterior or posterior approach, or both. The optimal approach depends on the characteristics of OPLL and cervical curvature. Although most patients can be successfully treated by a single surgery with the proper approach, renewed or newly developed neurological deterioration often requires repeat surgery. Methods : Twenty-seven patients with renewed or newly developed neurological deterioration requiring salvage surgery for multi-segment cervical OPLL were enrolled. Ten patients (group AP) underwent anterior approach, and 17 patients (group PA) underwent posterior approach at the initial surgery. Clinical and radiological data from initial and repeat surgeries were obtained and analyzed retrospectively. Results : The intervals between the initial and repeat surgeries were $102.80{\pm}60.08months$ (group AP) and $61.00{\pm}8.16months$ (group PA) (p<0.05). In group AP, the main OPLL lesions were removed during the initial surgery. There was a tendency that the site of main OPLL lesions causing renewed or newly developed neurological deterioration were different from that of the initial surgery (8/10, p<0.05). Repeat surgery was performed for progressed OPLL lesions at another segment as the main pathology. In group PA, the main OPLL lesions at the initial surgery continued as the main pathology for repeat surgery. Progression of kyphosis in the cervical curvature (Cobb's angle on C2-7 and segmental angle on the main OPLL lesion) was noted between the initial and repeat surgeries. Group PA showed more kyphotic cervical curvature compared to group AP at the time of repeat surgery (p<0.05). Conclusion : The reasons for repeat surgery depend on the type of initial surgery. The main factors leading to repeat surgery are progression of remnant OPLL at a different segment in group AP and kyphotic change of the cervical curvature in group PA.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.2
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• pp.183-193
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• 2010

Well planned rehabilitation order of pipes is essential for efficient maintenance and management of Water Distribution Systems. In this study, not only deterioration rate of pipes but also structural and nonstructural failure which causes abnormal condition of WDS is considered to determine rehabilitation order. Probabilistic Neural Network is used for calculating deterioration rate at present and the importance of pipes is computed under structural and nonstructural failure by using Pipe by Pipe Failure Analysis and Effect Index. Utopian Approach, one of the Multi-Criteria Decision Making methods, is used for assessment of final rehabilitation order based on distance measure between utopian point and alternative one. Developed model in this study shows that it gives more reliable results than existing methods considering hydraulic relative importance does in application to real networks. In this point, the newly developed model, which gives advantages over existing models, can make a credible decision and simple application.

• Earthquakes and Structures
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• v.3 no.5
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• pp.649-673
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• 2012

Recent studies have highlighted the importance of accounting for aging and deterioration of bridges when estimating their seismic vulnerability. Effects of structural degradation of multiple bridge components, variations in bridge geometry, and comparison of different environmental exposure conditions have traditionally been ignored in the development of seismic fragility curves for aging concrete highway bridges. This study focuses on the degradation of multiple bridge components of a geometrically varying bridge class, as opposed to a single bridge sample, to arrive at time-dependent seismic bridge fragility curves. The effects of different exposure conditions are also explored to assess the impact of severity of the environment on bridge seismic vulnerability. The proposed methodology is demonstrated on a representative class of aging multi-span reinforced concrete girder bridges typical of the Central and Southeastern United States. The results reveal the importance of considering multiple deterioration mechanisms, including the significance of degrading elastomeric bearings along with the corroding reinforced concrete columns, in fragility modeling of aging bridge classes. Additionally, assessment of the relative severity of exposure to marine atmospheric, marine sea-splash and deicing salts, and shows 5%, 9% and 44% reduction, respectively, in the median value bridge fragility for the complete damage state relative to the as-built pristine structure.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1265-1270
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• 2018

One of the ways to improve the stability of power facilities used in power systems is to use power surge arresters and to protect against transient overvoltages and surges in normal operation. Also it is important to reduce the impact of lightning strikes because lightning can create overvoltage in the grid of the wind turbine and affect power quality. So This paper analyzes the effects of overvoltage and adjacent turbines due to single strike and multi strike to ground impedance changes when the surge arrester is deteriorated in a wind power farm.

• Journal of the Korean housing association
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• v.17 no.2
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• pp.19-26
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• 2006

Building would be deteriorated with time elapse, influenced by its geographic situation, climate and other environmental conditions. In addition, the systematic maintenance could be provided to keep the resident a recent living condition. The existing breakdown maintenance will be changed into the preventive maintenance. The preventive maintenance is required to get the repair time, the repair scope and frequency. In this paper, it aimed at providing the repair time range over the building components, utilizing the relation between the determination curve and the performance recovery through repair. Results of this study are as follows : First, the forecast of the repair time over the building components could be calculated and equalized with the deterioration and performance degree. Second, the repair time range of building components would be provided into five categories and 3rd repair time. Results of this study will set up the long-term repair plan of building, and finally keep an housing condition comfortable.

• Computers and Concrete
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• v.4 no.3
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• pp.243-257
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• 2007

A novel method for recognition, characterization, and quantification of deterioration in bridge components and laboratory concrete samples is presented in this paper. The proposed scheme is based on grey level co-occurrence matrix texture analysis using Haar's discrete wavelet transform on concrete imagery. Each image is described by a subset of band-filtered images containing wavelet coefficients, and then reconstructed images are employed in characterizing the texture, using grey level co-occurrence matrices, of the different types and degrees of damage: map-cracking, spalling and steel corrosion. A comparative study was conducted to evaluate the efficiency of the supervised maximum likelihood and unsupervised K-means classification techniques, in order to classify and quantify the deterioration and its extent. Experimental results show both methods are relatively effective in characterizing and quantifying damage; however, the supervised technique produced more accurate results, with overall classification accuracies ranging from 76.8% to 79.1%.