• Earthquakes and Structures
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• v.9 no.6
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• pp.1337-1353
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• 2015

Seismic upgrading of existing structures is a technical and social issue aimed at risk reduction. Sustainable design is one of the most important challenges in any structural project. Nowadays, many retrofit strategies are feasible and several traditional and innovative options are available to engineers. Basically, the design strategy can lead to increase structural ductility, strength, or both of them, but also stiffness regulation and supplemental damping are possible strategies to reduce seismic vulnerability. Each design solution has different technical and economical performances. In this paper, four different design solutions are presented for the retrofit of an existing RC frame with poor concrete quality and inadequate reinforcement detailing. The considered solutions are based on FRP wrapping of the existing structural elements or alternatively on new RC shear walls introduction. This paper shows the comparison among the considered design strategies in order to select the suitable solution, which reaches the compromise between the obtained safety level and costs during the life-cycle of the building. Each solution is worked out by considering three different levels of seismic demand. The structural capacity of the considered retrofit solutions is assessed with nonlinear static analysis and the seismic performance is evaluated with the capacity spectrum method.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.11 no.18
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• pp.71-80
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• 1988

Process capability implies the qualitative capability of a process, and it is necessary to specify the process capability by quantification and to evaluate the level with the specified standardizaion. But the process capability index is currently used to evaluate the performance of quality control activity. without considering the characteristics of process structure or the economy of management. Here the researcher would like to redefine process capability and emphasize its index may be used as the measure of managerial assessment and the objective of process quality control in full consideration of the economic aspects of process characteristics. Too little or too much process capability causes a loss of or excess. The proper economic level of process capability varies to each process. The procedure of taking the optimum process capability index is derived from the expected profit function, whereas each method is studied in cases of normal process with one-sided specification and two-sided specification. In addition, the process capability index is presented as a method of quality assurance. And an example is exhibited on wrapping process of 'A' company. The results of this study are summarized at follows. First, though the norminalization of the process capability index is possible by the existing methods, the optimum process capability index can vary to the situation of each process. So, the optimum process capability index which is suggested in this dissertation should be used as the standard to assess process capability. Second, the process capability index can take its effect not just in indicating quality control or managerial records but also in the management of high qualify assurance.

• Structural Engineering and Mechanics
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• v.73 no.1
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• pp.53-64
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• 2020

In different high seismic regions around the world, many non-ductile existing reinforced concrete frame buildings, built without adequate seismic detailing requirements, have been damaged or collapsed after past earthquakes. The assessment and the retrofit of these non-ductile concrete structures is crucial theme of research for all the scientific community of engineers. In particular, a careful assessment of the existing building is fundamental for understanding the failure mechanisms that govern the collapse of the structure or the achievement of the recommended limit states. Based on the seismic assessment, the best retrofit strategy can be designed and applied to the structure. A school building located in Avellino province (Italy) is the case study. The analysis of seismic vulnerability carried out on the mentioned building has highlighted deficiencies in both static and seismic load conditions. The retrofit of the building has been designed based on different retrofit options in order to show the real retrofit design developed from the engineers to achieve the seismic safety of the building. The retrofit costs associated to structural operations are calculated for each case and have been summed up to the costs of the in situ tests. The paper shows a real retrofit design case study in which the best solution is chosen based on the results in terms of structural performance and cost among the different retrofit options.

• Steel and Composite Structures
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• v.30 no.3
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• pp.231-251
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• 2019

In the present study, a numerical and experimental investigation has been carried out on the seismic behavior of RC columns of a bridge which damaged under corrosive environments and retrofitted by various techniques including combined application of CFRP sheets and steel profiles. A novel hybrid retrofitting procedure, including the application of inner steel profiles and outer peripheral CFRP sheets, has been proposed for strengthening purpose. Seven large-scale RC columns of a Girder Bridge have been tested in the laboratory under the influence of simultaneous application of constant axial load and the lateral cyclic displacements. Having verified the finite element modeling, using ABAQUS software, the effects of important parameters such as the corrosion percentage of steel rebars and the number of CFRP layers have been evaluated. Based on the results, retrofitting of RC columns of the bridge with the proposed technique was effective in improving some measures of structural performance such as lateral strength degradation and higher energy absorption capability. However, the displacement ductility was not considerably improved whereas the elastic stiffness of the specimens has been increased.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.7
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• pp.639-647
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• 2009

In this work, wrapping conductors with thin magnetic materials is proposed as a magnetic shielding method. The 0.1 mm thick metal sheets of mu-metal, grain-oriented electrical steel, and non-oriented electrical steel were produced from commercial alloy sheets through cold rolling and followed high temperature annealing. In case of 3-phase electric currents, mu-metal was the best in shielding performance at a B-field magnitude of about 100 ${\mu}T$, whereas silicon steels were better than mu-metal at a B-magnitude over 500 ${\mu}T$. In addition, wrapping with silicon steel(inner) together with mu-metal(outer) resulted in a shielding factor less than 0.1 even at 500 ${\mu}T$. These results are due to changes in hierarchy of magnetic permeabilities of the materials with increasing magnetic field strength. In case of single-phase electric current, B-magnitude outside the magnetic shell was rather increased compared to the unshielded case. This result is explained by vector composition of B-fields near magnetic shielding materials.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.9
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• pp.1-8
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• 2010

A digital phase wrapping modulation (DPM) open-loop polar transmitter can be efficiently applied to a wideband orthogonal frequency division multiplexing (OFDM) communication system by converting in-phase and quadrature signals to envelope and phase signals and then employing the signal mapping process. This mapping process is very similar to quantization in a general communication system, and when taking into account the error that appears during mapping process, one can replace the coordinates rotation digital computer (CORDIC) algorithm in the coordinate conversion part with the Taylor series approximation method. In this paper, we investigate the application of the Taylor series approximation to the cartesian to polar coordinate conversion part of a DPM polar transmitter for wideband OFDM systems. The conventional approach relies on the CORDIC algorithm. To achieve efficient application, we perform computer simulation to measure mean square error (MSE) of the both approaches and find the minimum approximation order for the Taylor series approximation compatible to allowable error of the CORDIC algorithm in terms of hardware design. Furthermore, comparing the processing speeds of the both approaches in the implementation with FPGA reveals that the Taylor series approximation with lower order improves the processing speed in the coordinate conversion part.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.343-350
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• 2016

A secure and effective on-chip bus for detecting and preventing malicious attacks by infected IPs is presented in this paper. Most system inter-connects (on-chip bus) are vulnerable to hardware Trojan (Malware) attack because all data and control signals are routed. A proposed secure bus with modifications in arbitration, address decoding, and wrapping for bus master and slaves is designed using the Advanced High-Performance and Advance Peripheral Bus (AHB and APB Bus). It is implemented with the concept that arbiter checks share of masters and manage infected masters and slaves in every transaction. The proposed hardware is designed with the Xilinx 14.7 ISE and verified using the HBE-SoC-IPD test board equipped with Virtex4 XC4VLX80 FPGA device. The design has a total gate count of 39K at an operating frequency of 313MHz using the $0.13{\mu}m$ TSMC process.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.885-888
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• 2015

A secure and effective on-chip bus for detecting and preventing malicious attacks by infected IPs is presented in this paper. Most system inter-connect (on-chip bus) are vulnerable to hardware Trojan (Malware) attack because all data and control signals are routed. A proposed secure bus with modifications in arbitration, address decoding, and wrapping for bus master and slaves is designed using the Advanced High-Performance and Advance Peripheral Bus (AHB and APB Bus). It is implemented with the concept that arbiter checks share of masters and manage infected masters and slaves in every transaction. The proposed hardware is designed with the Xilinx 14.7 ISE and verified using the HBE-SoC-IPD test board equipped with Virtex4 XC4VLX80 FPGA device. The design has a total gate count of 40K at an operating frequency of 250MHz using the $0.13{\mu}m$ TSMC process.

• Korean Journal of Agricultural Science
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• v.47 no.3
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• pp.485-496
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• 2020

Recent changes in the disaster environment have greatly increased the possibility of internal erosion in deteriorated reservoirs; thus, countermeasure methods are required to enhance the drainage performance of embankments. Sand filters have been mainly used to prevent internal erosion; however, due to the sand depletion and environmental problems, new alternative materials are required to replace the sand in the filter zone. In this study, crushed stone was used instead of sand as a material that could satisfy permeability, material supply, demanding conditions, and economic efficiency. Although crushed stone has excellent drainage performance, it has a clogging phenomenon due to its high permeability. Accordingly, the materials need to be separated with a geotextile wrapping method. Additionally, the 3D numerical analysis and a large model experiment were conducted to evaluate the seepage characteristics and in-site application of the crushed stone filter. As a result, the crushed stone filter showed an excellent dispersion effect by reducing the pore water pressure by about 9.5 times that of the sand filter. In addition, it was shown that the safety factor for piping increased significantly by reducing internal erosion. When comparing the economics and supply and demand conditions of the material, crushed stone was evaluated as an effective method to reduce the internal erosion of embankments at deteriorated reservoirs.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.7-14
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• 2019

The type III vessel, which is used to store high-pressure hydrogen gas, is made by wrapping the vessel's liner with carbon fiber composite materials for strength performance and lightening. The liner seals the internal gas and the composite resists the internal pressure. The properties of the fiber composite material depends on the angle and thickness of the fiber. Thus, engineers should consider these various design variables. However, it significantly increases the design cost due to the trial and error under designing based on experience or experiments. And, for aluminum liners, fatigue loads due to using and charging could give a huge impact on the performance of the structure. However, fatigue failure does not necessarily occur in the position under the highest load in use. Therefore, for hydrogen storage vessel, fatigue evaluation according to design patterns is essential because stress distribution varies depend on composite layer patterns. This study performed an optimization analysis and evaluated a high-pressure hydrogen storage vessel to minimize these trial and error and improve the reliability of the structure, while simultaneously conducting fatigue assessment of all patterns derived from the optimization analysis process. The results of this study are thought to be useful in the strength improvement and life design of composite reinforced high-pressure storage vessels.