• ETRI Journal
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• v.45 no.1
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• pp.45-59
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• 2023

In this paper, to optimize the average delay and power allocation (PA) for system users, we propose a resource scheduling scheme for wireless networks based on Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) according to the first fifth-generation standards. For delay minimization, we solve a throughput maximization problem that considers CPOFDM systems with carrier aggregation (CA). Regarding PA, we consider an approach that involves maximizing goodput using an effective signal-to-noise ratio. An algorithm for jointly solving delay minimization through computation of required user rates and optimizing the power allocated to users is proposed to compose the resource allocation approach. In wireless network simulations, we consider a scenario with the following capabilities: CA, 256-Quadrature Amplitude Modulation, millimeter waves above 6 GHz, and a radio frame structure with 120 KHz spacing between the subcarriers. The performance of the proposed resource allocation algorithm is evaluated and compared with those of other algorithms from the literature using computational simulations in terms of various Quality of Service parameters, such as the throughput, delay, fairness index, and loss rate.

• Journal of Intelligence and Information Systems
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• v.18 no.1
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• pp.59-69
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• 2012

As exhibition industry, which is a part of 17 new growth engines of the government, is related to other industries such as tourism, transportation and financial industries. So it has a significant ripple effect on other industries. Exhibition is a knowledge-intensive, eco-friendly and high value-added Industry. Over 13,000 exhibitions are held every year around the world which contributes to getting foreign currency. Exhibition industry is closely related with culture and tourism and could be utilized as local and national development strategies and improve national brand image as well. Many countries try various efforts to invigorate exhibition industry by arranging related laws and support system. In Korea, more than 200 exhibitions are being held every year, but only 2~3 exhibitions are hosted with over 400 exhibitors and except these exhibitions most exhibitions have few foreign exhibitors. The main reason of weakness of domestic trade show is that there are no agencies managing exhibitionrelated statistics and there is no specific and reliable evaluation. This might cause impossibility of providing buyer or seller with reliable data, poor growth of exhibitions in terms of quality and thus service quality of trade shows cannot be improved. Hosting a lot of visitors (Public/Buyer/Exhibitor) is very crucial to the development of domestic exhibition industry. In order to attract many visitors, service quality of exhibition and visitor's satisfaction should be enhanced. For this purpose, a variety of real-time customized services through digital media and the services for creating new customers and retaining existing customers should be provided. In addition, by providing visitors with personalized information services they could manage their time and space efficiently avoiding the complexity of exhibition space. Exhibition industry can have competitiveness and industrial foundation through building up exhibition-related statistics, creating new information and enhancing research ability. Therefore, this paper deals with customized service with visitor's smart-phone at the exhibition space and designing mobile framework which enables exhibition devices to interact with other devices. Mobile server framework is composed of three different systems; multi-server interaction, server, client, display device. By making knowledge pool of exhibition environment, the accumulated data for each visitor can be provided as personalized service. In addition, based on the reaction of visitors each of all information is utilized as customized information and so the cyclic chain structure is designed. Multiple interaction server is designed to have functions of event handling, interaction process between exhibition device and visitor's smart-phone and data management. Client is an application processed by visitor's smart-phone and could be driven on a variety of platforms. Client functions as interface representing customized service for individual visitors and event input and output for simultaneous participation. Exhibition device consists of display system to show visitors contents and information, interaction input-output system to receive event from visitors and input toward action and finally the control system to connect above two systems. The proposed mobile framework in this paper provides individual visitors with customized and active services using their information profile and advanced Knowledge. In addition, user participation service is suggested as well by using interaction connection system between server, client, and exhibition devices. Suggested mobile framework is a technology which could be applied to culture industry such as performance, show and exhibition. Thus, this builds up the foundation to improve visitor's participation in exhibition and bring about development of exhibition industry by raising visitor's interest.

• Journal of the Korean Society for Railway
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• v.20 no.1
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• pp.64-75
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• 2017

The role of a track subgrade is to provide bearing capacity and distribute load transferred to lower foundation soils. Track subgrade soils are usually compacted by heavy mechanical machines in the field, such that sometimes they are attributed to progressive residual settlement during the service after construction completion of the railway track. The progressive residual settlement generated in the upper part of a track subgrade is mostly non-recoverable plastic deformation, which causes unstable conditions such as track irregularity. Nonetheless, up to now no design code for allowable residual settlement of subgrade in a railway trackbed has been proposed based on mechanical testing, such as repetitive triaxial testing. At this time, to check the DOC or stiffness of the soil, field test criteria for compacted track subgrade are composed of data from RPBT and field compaction testing. However, the field test criteria do not provide critical design values obtained from mechanical test results that can offer correct information about allowable permanent deformation. In this study, a test procedure is proposed for permanent deformation of compacted subgrade soil that is used usually in railway trackbed in the laboratory using repetitive triaxial testing. To develop the test procedure, an FEA was performed to obtain the shear stress ratio (${\tau}/{\tau}_f$) and the confining stress (${\sigma}_3$) on the top of the subgrade. Comprehensive repetitive triaxial tests were performed using the proposed test procedure on several field subgrade soils obtained in construction sites of railway trackbeds. A permanent deformation model was proposed using the test results for the railway track.

• Journal of Energy Engineering
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• v.20 no.2
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• pp.90-95
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• 2011

This study was conducted to judge requalification of cylinders by assessing composite flaws such as scratches, cuts, and gouges damaging on the composite of Type III cylinders for compressed natural gas vehicles. As a result of the flaw tolerance test, all specimens have satisfied with minimum requirement cycles according to damage levels based on ISO 19078 and cyclic performance for pressure showed beyond twenty thousands in damage level 1 and 2, and did eighteen thousands to twenty-one thousands in damage level 3. Eight of twelve specimens failed the test due to composite flaws and the rest of the cylinders failed regardless of flaws. The results of Finite Element Method followed by the computer simulation indicated that the stress of 79.5 MPa calculated on the flaw model of $1.25\;mm{\times}200\;mm$ and the stress of 66.6 MPa on the non-flaw model when the service pressure applied to inside of cylinder. The difference between the models is about 19.37%. We concluded that this difference influences fatigue life and this flaw model is a critical value affecting cyclic performance of cylinders.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.71-77
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• 2019

Recently, most of the pile foundations have been applied as a method to transfer the heavy load of the structure to the ground with high bearing capacity. In this study, the pile-cap behavior between foundation and hollow-head precast reinforced concrete(HPC) pile reinforced with longitudinal rebar and filling concrete was experimentally evaluated depending on the cyclic load and reinforcement ratio. As the drift ratio increases, it was found that the cracks pattern and fracture behavior of two types of pile-cap specimens according to the reinforcement ratio were evaluated to be similar. As the reinforcement ratio increases by 1.77 times, the BS-H25 specimen increases the maximum load by 1.47 times compared to the BS-H19 specimen. However, the ductility ratio of positive and negative was decreased by 76% and 70% respectively. After the yielding of the pile-cap reinforcing rebars, the positive and negative stiffness of the all specimens were decreased by a range from 66% to 71% and a range from 54% to 57% respectively, and the average stiffness of BS-H25 specimen is 13% higher than that of BS-H19 specimen. The cumulative dissipated energy capacity of BS-H19 and BS-H25 specimen under ultimate load state is 5.5 times and 6.6 times higher than that of service load state.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2139-2146
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• 2023

During reactor operation, the divertor must withstand unprecedented simultaneous high heat fluxes and high-energy neutron irradiation. The extremely severe service environment of the divertor imposes a huge challenge to the bonding quality of divertor joints, i.e., the joints must withstand thermal, mechanical and neutron loads, as well as cyclic mode of operation. In this paper, potassium-doped tungsten (KW) is selected as the plasma facing material (PFM), oxygen-free copper (OFC) as the interlayer, oxide dispersion strengthened copper (ODS-Cu) alloy as the heat sink material, and reduced activation ferritic/martensitic (RAFM) steel as the structural material. In this study, a vacuum brazing technology is proposed and optimized to bond Cu and ODS-Cu alloy with the silver-free brazing material CuSnTi. The most appropriate brazing parameters are a brazing temperature of 940 ℃ and a holding time of 15 min. High-quality bonding interfaces have been successfully obtained by vacuum brazing technology, and the average shear strength of the as-obtained KW/Cu and ODS-Cu alloy joints is ~268 MPa. And a fabrication route for manufacturing the flat-type divertor target based on brazing technology is set. For evaluating the reliability of the fabrication technologies under the reactor relevant condition, the high heat flux test at 20 MW/m² for the as-manufactured flat-type KW/Cu/ODS-Cu/RAFM mockup is carried out by using the Electron-beam Material testing Scenario (EMS-60) with water cooling. This paper reports the improved vacuum brazing technology to connect Cu to ODS-Cu alloy and summarizes the production route, high heat flux (HHF) test, the pre and post non-destructive examination, and the surface results of the flat-type KW/Cu/ODS-Cu/RAFM mockup after the HHF test. The test results demonstrate that the mockup manufactured according to the fabrication route still have structural and interfacial integrity under cyclic high heat loads.

• Korean Journal of Materials Research
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• v.3 no.6
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• pp.624-631
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• 1993

The composites in the system aluminium titanate-mullite were synthesized by stepwise alkoxide hydrolysis of tetraethylorthosilicate, Si(OCLH5), and titaniumtetraethoxide, $Ti(OC_{2}H_{5})_4$ in $Al_{2}O_{3}$ ethanolic colloidal solution. All particles produced by sol-gel-process were amorphous, monodispesed and had a narrow particle size distribution. Sintered bodies at $1600 ^{\circ}C$ for 2h were subjected to prolonged durability tests-on the one hand annealing at the critical decomposition temperature of $1100 ^{\circ}C$ for lOOh and on the other cyclic thermal shock between 750 and $1400 ^{\circ}C$ for 100h. The best thermal durability was achieved by a composition containing 70 and 80 vol% aluminium titanate, which showed little change in microstructure and thermal expansion cycles during the tests. The microstructural degradation of samples studied using scanning electron microscopy, X-ray diffraction, and dilatometry, was presented here. The study was conducted in order to predict the service life of aluminium titanate-mullite ceramics formed by this processing route.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11A
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• pp.861-869
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• 2011

In this paper, we propose coordinated scheduling and beamforming based on limited feedback to overcome the effects of inter-cell interference in multi-cell environment. The goal of this study is to improve a performance of cell-edge area significantly affected by the inter-cell interference and also to guarantee a performance of the entire system. Existing coordinated scheduling and beamforming based on the perfect channel state information generates an overhead for the channel state information feedback and exchange at the users and base stations, respectively. In this study, first we propose a novel codebook to obtain a null space of an interference channel efficiently which can be used to reduce the inter-cell interference. Using the proposed codebook, we propose coordinated scheduling and beamforming to improve the performance of cell-edge area and the entire system. Through the proportional fair scheduling, the performance of the proposed technique is shown as improvement of channel capacity for users located cell-edge area and entire system.

• The Plant Pathology Journal
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• v.26 no.2
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• pp.170-177
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• 2010

Bacillus licheniformis N1, previously developed as a biofungicide formulation N1E to control gray mold disease of plants, was investigated to study the bacterial traits that may be involved in its biological control activity. Two N1E based formulations, bacterial cell based formulation PN1E and culture supernatant based formulation SN1E, were evaluated for disease control activity against gray mold disease of tomato and strawberry plants. Neither PN1E nor SN1E was as effective as the original formulation N1E. Fractionation of antifungal compounds from the bacterial culture supernatant of B. licheniformis N1 indicated that two different cyclic lipopeptides were responsible for the antimicrobial activity of the N1 strain. These two purified compounds were identified as iturin A and surfactin by HPLC and LCMS. The purified lipopeptides were evaluated for plant disease control activity against seven plant diseases. Crude extracts and purified compounds applied at 500 ${\mu}g/ml$ concentration controlled tomato gray mold, tomato late blight and pepper anthracnose effectively with over 70% disease control value. While iturin showed broad spectrum activity against all tested plant diseases, the control activity by surfactin was limited to tomato gray mold, tomato late blight, and pepper anthracnose. Although antifungal compounds from B. licheniformis N1 exhibited disease control activity, our results suggested that bacterial cells present in the N1E formulation also contribute to the disease control activity together with the antifungal compounds.

• Journal of Ocean Engineering and Technology
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• v.17 no.2
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• pp.34-39
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• 2003

Recent deepwater offshore structures in the Gulf of Mexico utilize butt welded tubular joints. Application of a welded tubular joint includes tendons, production risers, and steel catenary risers. Fatigue life assessment of these joints becomes more critical, as the structures to which they are attached are allowed to undergo cyclic and sometimes large displacements around an anchored position. Estimation of the fatigue behavior of these tubular members in the design stage is generally condrcted by using S-N curves, as specified in the codeds and standards. Applying the stress concentration factor of the welded structure to the S-N approach often results in a very conservative assessment, because the stress field acting on the tubular has a non-uniform distribution through the thickness. Fatigue life analysis using fracture mechanics has been applied in the design of the catenary risers. This technology enables the engineer to establish proper requirements on weld quality and inspection acceptance criteria to assure satisfactory structural integrity during its design life. It also provides guidance on proper design curves and a methodology for accounting for the effects of non-uniform stress distribution through the wall thickness. Still, there is inconsistency when designing tubular joints using a conventional S-N approach and when specifying weld flaw acceptance criteria using fracture mechanics approach. This study developed fatigue curves that are consistent with both the S-N approach and the fracture mechanics approach. Accounting for non-uniform stress distribution and threshold stress intensity factor were key parameters in relating both approaches. A series of S-N curves, generated from the fracture mechanics approach, were compared to the existing S-N curves. For flat plate butt joint, the S-N curve generated from fracture mechanics matches with the IIW class 100 curve when initial crack depth was 0.5 mm (0.02 ). The new curves for tubular joint agree very well with the experimental results. The comparison also indicated the degree of conservatism built into the API X design curve.