• Journal of Korea Technology Innovation Society
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• v.12 no.2
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• pp.388-412
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• 2009

This study analyzed the important factors in service quality for public usage of national R&D facilities and equipments, and, using those factors, performed the importance-performance analysis for several national R&D programs in order to examine what service quality factors should be concentrically improved in each programs. Additionally, the in-depth interview with program managers and R&D facility experts was performed to realize the managerial issues subject to the characteristics of programs regarding the national R&D public facility management. As the results, this study made some political suggestions such as the reformation of promoter's role regarding the formulation of the government policy to support those programs. For example, it is more suitable for colleges as the subject of programs to be invested for self-research purpose rather than public usage, for independent corporation to be centered on the more general and common production fields, and for the government R&D agencies on the leading and special technical fields.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.2
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• pp.16-23
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• 2006

This paper presents a novel single-stage high frequency resonant inverter link type DC-DC converter using zero voltage switching with high power-factor. The proposed topology is integrated half-bridge boost rectifier as power factor corrector(PFC) and half-bridge high frequency resonant converter into a single-stage. The input stage of the half-bridge boost rectifier works in discontinuous conduction mode(DCM) with constant duty cycle and variable switching frequency. So that a boost converter makes the line current follow naturally the sinusoidal line voltage waveform. Simulation results have demonstrated the feasibility of the proposed high frequency resonant converter. Characteristics values based on characteristics analysis through circuit analysis is given as basis data in design procedure. Also, experimental results are presented to verify theoretical discussion. This proposed inverter will be able to be practically used as a power supply in various fields as induction heating applications, fluorescent lamp and DC-DC converter etc.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.640-647
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• 2018

Many harbor structures have been constructed, and some structures are now under construction in Korea, which is a peninsular state and a logistics hub in Northeast Asia. Expansions and extensions of existing harbors are also being planned to meet increasing natural disaster threats. Wave-dissipation concrete blocks are recycled or discarded based on the personal experience of engineers only, and there are no safety checks or criteria. To check the safety of used blocks, material evaluations were done by visual inspection of blocks on the ground and under water and from 20 non-destructive measurements of the rebound hardness test and 3 concrete core samples. Wave-dissipation blocks are sometimes fully or partially damaged in the process of transferring and mounting them or during construction. Therefore, a safety check is essential for recycling blocks with an evaluation of materials while considering the construction phases. To do this, a block was modeled with a 3D finite element method using ADINA, and impact analyses were done according to the transfer, mounting, and construction phases. From the results of the impact analyses and material evaluation, the safety checks and reasonable evaluation of used blocks were examined, and detailed construction methods are proposed. The methods are expected to maximize the reuse of used wave-dissipation blocks from an economical point of view.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.6
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• pp.723-731
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• 2020

The design of offshore plants should reflect the various requirements of the owner and the classification society. For a topside module mounted on an of shore structure, the design process is very demanding because of the large spatial constraints and the many requirements related to marine environmental conditions and safety such as the movement of the structure. In this study, the load acting on the hydraulic power unit, which is one of the main equipment in the topside module, was calculated according to the DNVGL rule; the structural safety was evaluated according to each load condition and the structural reliability of the developed product was improved. For structural analysis, MSC software was used, and structural analysis was performed under five load conditions to review structural safety for various movements. The results show that the maximum stress occurred during pitching toward the stern (Load Case 5). The stress level was approximately 85 % of the allowable stress, and the maximum deformation was approximately 5 % of the allowable value. The structural safety was confirmed, and no intermember interference occurred.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.557-562
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• 2018

Unlike live ammunition which has killing power due to the use of high explosives, training ammunition has only the limited explosive effect needed for training purposes, so the risk of accidents is lowered. Because training ammunition is used in large quantities during military drills, the problem of environmental pollution occurs. As most of the waste is left out in the training field, using bio-degradable polymers such as Polylactic Acid (PLA) can provide a solution to these environmental issues. However, bio-degradable polymers such as PLA usually have poor thermal and mechanical properties compared with other general purpose polymers, so they need to be improved before they can be used for military purposes. In this study, Talc is added to the PLA used for the parts of Training Grenades to improve some of their properties and the changes of their thermal and mechanical properties were verified. In the case of the 1 wt.% ~ 5 wt.% PLA/Talc blends, the thermal properties were improved in proportion to the content of Talc, but the best mechanical properties were observed for the 1 wt.% and 3 wt.% PLA/Talc blends.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.714-721
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• 2018

In this study, we investigate a design technology intended to radically increase the buckling strength of vertically curved panels. Recent studies proposed a buckling strength formula which properly reflects the effect on the local plate buckling strength of flat plates when they are stiffened by closed section ribs. Herein, we attempted to quantitatively evaluate this effect on curved panels and to reveal the correlations with the design parameters. The commercial finite element software, ABAQUS, was used to build a three dimensional numerical model and numerical parametric studies were conducted to evaluate the variation of the buckling strength. In the case of flat panels, the local buckling strength of stiffened curved panels increases proportionally with increasing rotational stiffness of the closed-section ribs. After attaining a limiting value, an obvious tendency was found that the local buckling strength of the stiffened curved panel would converge towards a fixed value when the panels are supported along both sides. The parametric studies performed using the influential design parameters confirmed that the estimated partially-restrained curved panel strength is well correlated with the proposed formula.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.367-373
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• 2017

The O2O service is an efficient way to operate based on systematic connection of the offline and online states. At present, education, health checkups, and exposure management of radiation workers are separated from offline and online at nuclear-related workplaces. Therefore, we developed a radiation workers management program at the workplace and tried to link online and offline states. After applying the program to the local network, we developed a written employee management system as a computer program and applied it to radiation workers and radiation safety managers at a university hospital in Daejeon using a questionnaire. As a result of the survey, the results of this program can enhance the awareness of safety management and work convenience. There is also a demand for radiation closed workers as well as radiation relative workers. It will be necessary to collect opinions regarding the characteristics of each workplace for the generalization of the radiation workers management program. As a result, real-time radiation safety management and work improvement can be expected through network connections between the workplace, supervisory authority, and related organizations in the future. If a circle structure is formed using the employee management program, development of radiation safety management can be expected.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.9
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• pp.459-466
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• 2007

TCP/IP processing imposes a heavy load on the host CPU when it is processed by the host CPU on a very high-speed network. Recently the TCP/IP Offload Engine (TOE), which processes TCP/IP on a network adapter instead of the host CPU, has become an attractive solution to reduce the load in the host CPU. There have been two approaches to implement TOE. One is the software TOE in which TCP/IP is processed by an embedded processor and the other is the hardware TOE in which TCP/IP is processed by a dedicated ASIC. The software TOE has poor performance and the hardware TOE is neither flexible nor expandable enough to add new features. In this paper we designed and implemented a hybrid TOE architecture, in which TCP/IP is processed by cooperation of hardware and software, based on an FPGA that has two embedded processor cores. The hybrid TOE can have high performance by processing time-critical operations such as making and processing data packets in hardware. The software based on the embedded Linux performs operations that are not time-critical such as connection establishment, flow control and congestions, thus the hybrid TOE can have enough flexibility and expandability. To improve the performance of the hybrid TOE, we developed a hardware-based transmission/reception accelerator that processes important operations such as creating data packets. In the experiments the hybrid TOE shows the minimum latency of about $19{\mu}s$. The CPU utilization of the hybrid TOE is below 6 % and the maximum bandwidth of the hybrid TOE is about 675 Mbps.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.697-703
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• 2017

This paper examines the flexure behavior of FRP-concrete composite structure that can replace conventional reinforced concrete structure types. In order to investigate the structural performance and behavioral characteristics in numerical analysis means, ABAQUS, a general purpose finite element analysis program, was utilized for nonlinear finite element analysis, and the various variables and their influences were analyzed and compared with experimental results to suggest values optimized to this composite structure. The concrete damage plasticity model and Euro code for concrete were used. In the implicit finite element analysis, the convergence was ambiguous when geometrical and material nonlinearity were large, so the explicit finite element analysis used in this study was deemed to be appropriate. From the comparison with the experiment about concrete damaged plasticity model, 20mm for the mesh size, $30^{\circ}$ for the dilation angle, $100Nmm/mm^2$ for the value of fracture energy, 0.667 for Kc value, and the consideration of damage parameter were suggested believed to be appropriate. The numerical model suggested in this study was able to imitate the ultimate load and cracking pattern very well; therefore, it is expected to be utilized in research of various new material composite structures.

• The Journal of the Acoustical Society of Korea
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• v.18 no.5
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• pp.68-77
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• 1999

The paper looked into the effects of the spectral properties (waveform) of the high intensity focused ultrasound on suppression of the ultrasonic cavitation. Three different types of ultrasound were considered in the study, which were sinusoidal (1 MHz, 5 MPa), frequency modulated (from 1 MHz to 6 MHz for 10 ㎲, 5 MPa), asymmetrically shocked (fundamental frequency 1 MHz, peak positive pressure 12 MPa, peak negative pressure -4 MPa). The temporal response of an air bubble in water initially 1 ㎛ in radius to each type of the ultrasound was predicted using Gilmore bubble dynamic model and Church's rectified gas diffusion equation. It was shown that the radially pulsating amplitude of the bubble was greatly reduced for the frequency modulated wave and was little decreased for the shock wave, compared to the case that the bubble was exposed to the sinusoidal wave. It is interesting that the bubble response to the frequency modulated wave remains similar when the frequency component of the modulated ultrasound is beyond the bubble resonant frequency 3 MHz. This implies that, although the ultrasound is modulated up to 3MHz rather than up to the present 6 MHz, it is likely to produce similar cavitation suppression effects. In practice, it means that a typical narrow band ultrasonic transducer can be taken to generate an appropriate frequency modulated ultrasound to reduce cavitation activity. The present study indicates that ultrasonic cavitation may be suppressed to some extent by a proper spectral modification of high intensity ultrasound.