• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1042-1049
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• 2014

In Military MicroWave communication, the distance of link, availability, transmission capacity is the important point in order to design the circuit. Currently, operated by fixed modulation, in the future it will be evolved to the modulation techniques enabled to increase the transmission capacity. It would be hard to consistently guarantee the transmission quality of the high-availability because the occurrence probability of fading increase in terms of the link distance for the case of the long distance. In the case of the modulation techniques for the transmission of high-capacity, as the distance is long, a falling-off in the fade margin from the link budget analysis cause the decrease in the availability. It is difficult to provide QoS guaranteed connection. In this paper, we propose the performance improvement technique of transmission by the variable allocation of the bandwidth and the higher priority transmission technique using setting the ratio of the higher priority capacity in association with the distance of link. Also we suggest the alternative of the calculation for channel transmission capacity to design the circuit.

• Steel and Composite Structures
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• v.43 no.4
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• pp.447-456
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• 2022

Recent experimental studies showed that deep steel I-shaped profiles classified as high ductility class sections in seismic design international codes exhibit low deformation capacity when subjected to cyclic loading. This paper presents an innovative retrofit solution to increase the rotation capacity of beams using bonded carbon fiber reinforced polymers (CFRP) patches validated with advanced finite element analysis. This investigation focuses on the flexural cyclic behaviour of I-shaped hot rolled steel deep section used as beams in moment-resisting frames (MRF) retrofitted with CFRP patches on the web. The main goal of this CFRP reinforcement is to increase the rotation capacity of the member without increasing the overstrength in order to avoid compromising the strong column-weak beam condition in MRF. A finite element model that simulates the cyclic plasticity behavior of the steel and the damage in the adhesive layer is developed. The damage is modelled using the cohesive zone modelling (CZM) technique that is able to capture the crack initiation and propagation. Details on the modelling techniques including the mesh sensitivity near the fracture zone are presented. The effectiveness of the retrofit solution depends strongly on the selection of the appropriate adhesive. Different adhesive types are investigated where the CZM parameters are calibrated from high fidelity fracture mechanics tests that are thoroughly validated in the literature. This includes a rigid adhesive commonly found in the construction industry and two tough adhesives used in the automotive industry. The results revealed that the CFRP patch can increase the rotation capacity of a steel member considerably when using tough adhesives.

• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.385-397
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• 2023

This study presents an experiment and analysis to compare the seismic behavior of full-scale reinforced concrete beam-column joint strengthened by prestressed steel strips, externally bonded steel plate, and CFRP sheets. For experimental investigation, five specimens, including one joint without any retrofitting, one joint retrofitted by externally bonded steel plate, one joint retrofitted by CFRP sheets, and two joints retrofitted by prestressed steel strips, were tested under cyclic-reserve loading. The failure mode, strain response, shear deformation, hysteresis behavior, energy dissipation capacity, stiffness degradation and damage indexes of all specimens were analyzed according to experimental study. It was found that prestressed steel strips, steel plate and CFRP sheets improved shear resistance, energy dissipation capacity, stiffness degradation behavior and reduced the shear deformation of the joint core area, as well as changed the failure pattern of the specimen, which led to the failure mode changed from the combination of flexural failure of beams and shear failure of joints core to the flexural failure of beams. In addition, the beam-column joint retrofitted by steel plate exhibited a high bearing capacity, energy consumption capacity and low damage index compared with the joint strengthened by prestressed steel strip, and the prestressed steel strips reinforced joint showed a high strength, energy dissipation capacity and low shear deformation, stirrups strains and damage index compared to the CFRP reinforced joint, which indicated that the frame joints strengthened with steel plate exhibited the most excellent seismic behavior, followed by the prestressed steel strips.

• Journal of the Korea Society of Computer and Information
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• v.6 no.1
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• pp.74-81
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• 2001

In this paper. the architecture of a high-speed ATM router using ATM switch is studied and the performance of the high-speed ATM router is analyzed through simulation. The high-speed ATM router using ATM switch is able to reduce the load of router and the processing time of a packet in the router. The size of router buffers has been studied through simulation processes for the analysis of performance capacity in due course of making changes in routing time(RT), which is the performance capacity parameters of high-speed ATM routers, flow table size(FS), flow live time(FT) and input circuit efficiencies. The result of this study can be used as the source material for analyzing the suitability of equipment in upgrading networks and applying high-speed ATM routers by using ATM switches.

• Journal of Korea Multimedia Society
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• v.13 no.7
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• pp.1088-1094
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• 2010

Image authentication algorithms have to discriminate forged contents in the various critical fields of military, medical services, digital documents. They must ensure perceptual invisibility and fragility against malicious attacks. It is desirable that watermarking algorithms support sufficient insertion capacity and blind feature. And, high reliable algorithms that can eliminate false-positive and false-negative errors are needed in the watermark extraction process. In this paper, we control coefficients of high frequency band in a DCT domain and compensate brightness histogram for high reliability. As a result, we found that the proposed algorithm guarantee various requirements such as perceptual invisibility with high PSNR values, fragility, high reliability and blind feature. In addition, experiment results show that the proposed algorithm can be used steganographic applications by sufficient capacity of watermark.

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.430-436
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• 2020

Lithium thionyl chloride (Li/SOCl₂) batteries exhibit the highest energy densities seen in commercially available primary batteries because of their high operating voltages and discharge capacities. They are widely used in various extreme environments; however, they show signs of degradation at high discharge currents. The discharge performance of Li/SOCl₂ is considered to be greatly dependent on the carbon materials used in the cathode. Therefore, suitable carbon materials must be chosen to improve discharge performances. In this work, we investigated the discharge properties of Li/SOCl₂ batteries in which the cathodes contained various ratios of acetylene black (AB) and multi-walled carbon nanotubes (MWCNTs) at high discharge currents. It was confirmed that the MWCNTs were effectively dispersed in the mixed AB/MWCNT cathodes. Moreover, the discharge capacity and operating voltage improved at high discharge currents in these mixed cathodes when compared with pure AB cathodes. It was found that the mesopores present in the cathodes have a strong impact on the discharge capacity, while the macropores present on the cathode surface influence the discharge properties at high discharge rates in Li/SOCl₂ batteries. These results indicate that the ratio of mesopores and macropores in the cathode is key to improving the discharge performance of Li/SOCl₂ batteries, as is the dispersion of the MWCNTs.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.1
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• pp.51-56
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• 1999

This paper presents a new transient overvoltage blocking device (TOBD) for info-communication facilities with low power and high frequency bandwidth. Conventional protection devices have some problems such as low frequency bandwidth, low energy capacity and high remnant voltage. In order to improve these limitations, thehybrid type TOBD, which consists of a gas tube, avalanche diodes and junction typefield effect transistors (JFETs), was designed and fabricated. The TOBD differs from the conventional protection devices in configuration, and JFETs were used as an active non-linear element and a high speed switching diode with low capacitance limits high current. Therefore the avalanche dilde with low energy capacity are protected fromthe high current, and the TOBD has a very small input capacitance. From the performance test using combination surge generator, which can produce $1.2/50\mus\;4.2kV_{max}\; 8/20\mus\; 2.1kA_{max}$, it is confirmed that proposed TOBD has an excellent protection performance in tight clamping voltage and limiting current characteristics.

• Asian Journal of Innovation and Policy
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• v.7 no.1
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• pp.103-130
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• 2018

It is generally understood that clusters are the promoters of innovation and therefore, the attention of researchers has been increasingly to discern the factors driving innovation among the firms in a cluster, especially in a high-tech cluster. In this study, we identify the variables capturing the nature of a firm that possibly impact the absorptive capacity of a firm and subsequently ascertain their impact on the degree of interactions between a firm, and other firms and associated institutions within and outside a cluster, respectively. Furthermore, we probe the influence of these interactions as a whole on firm-level innovation. The study was carried out in the context of Bengaluru, which houses the densely interconnected network of innovation-intensive high-tech manufacturing firms forming a high-tech manufacturing cluster. Data were drawn from 101 high-tech manufacturing firms belonging to electronics, machine tools, electrical and pharmaceutical industries. Based on the cluster analysis and subsequent graphical analysis on each of the three profiled clusters, it was found that size and origin of a firm have significant impact on the degree of firm's interactions. In turn, higher dynamism of firms in terms of degree of interactions led to higher innovation performance.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_2
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• pp.491-499
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• 2021

Batteries are widely used for energy storage, such as ESS(Energy Storage System), electric vehicles, electric aircraft, and electric powered ships. Among them, a submarine uses a high power battery for an energy storage. When the battery of a submarine is discharged, a diesel generator generates AC power, and then AC/DC power converter change AC power to DC power for charging the battery. Therefore, in order to lower the current capacity of the diesel generator, it is necessary to use an AC/DC converter with a high input power factor. And, a power converter with a large power capacity must have high stability because it can lead to a major accident when a failure occurs. However, the control algorithm using the traditional PI controller is difficult to satisfy stability and dynamic characteristics. In this paper, we design the high power AC/DC converter with high input power factor for battery charging systems. And, we propose a stable control algorithm. The validity of the proposed method is verified through simulation and experiments.

• Steel and Composite Structures
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• v.48 no.5
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• pp.599-610
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• 2023

To avoid debonding failure, a novel type of hybrid anchorage (HA) is proposed in this study that uses a slotted plate to lock the ends of the fiber-reinforced polymer (FRP) sheet in addition to the usual bonding over the substrate of the strengthened member. An experimental investigation was performed on three groups of RC beams, which differed from one another in either concrete strength or steel reinforcement ratio. The test results indicate that the end self-locking of the CFRP sheet can improve the failure ductility, ultimate capacity of the beams and its utilization ratio. Although intermediate debonding occurred in all the strengthened beams, it was not a fatal mode of failure for the three specimens with end anchorage. Among them, FRP rupture occurred in the beam with higher concrete strength and lower steel reinforcement ratio, whereas the other two failed by concrete crushing. The beam strengthened by HA obtained a relatively high percentage of increase in ultimate capacity when the rebar ratio or concrete strength decreased. The expressions in the literature were inspected to calculate the critical loads at intermediate debonding, FRP rupturing and concrete crushing after debonding for the strengthened beam. Then, the necessity of further research is addressed.