• Transactions of the Society of Information Storage Systems
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• v.1 no.2
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• pp.169-174
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• 2005

Current information storage devices read/write data on the rotating disk. The axial vibration of a rotating disk should be suppressed for the successful operation of the device. Information storage devices widely used in these days adopt relatively thick disk which is stiff enough to suppress axial vibration under allowable limit. However, the thickness of the disk is going to be thinner and thinner as the small form factor of the devices is getting preferred by the consumer. In this study, a stabilizer system, which is composed with 8 air bearings, is proposed for suppressing the axial vibration of a $95{\mu}m$ thick PC disk in a non-contacting manner. The performance of the stabilizer system is simulated by numerical computation and then confirmed its results through a series of experiment. A thin and flexible disk has various vibration modes when it rotates in high speed. The stabilizer system generates positive as well as negative pressure due to the rotation of flexible disk so that the force due to the pressure distribution pushes and pulls rotating disk in a non-contacting manner. The balance between positive and negative pressure forces can be obtained by adjusting the area and the slope of the air bearing surface. The axial vibration of the flexible disk of 120mm diameter is suppressed successfully from over $1000{\mu}m$ to $30{\mu}m$ peak-to-peak value at the rotational speed of 5,000rpm.

• Health Policy and Management
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• v.15 no.3
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• pp.40-59
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• 2005

The objective of this paper is to examine what impact the newly introduced Purchasing Price Reimbursement System, where insurance drugs are reimbursed at the prices as they were purchased by medical care providers under the maximum allowable cap, has upon the health insurer's financing situation. The impact of the Purchasing Price Reimbursement System is considered to be confined mainly to the inpatient department among three drug reimbursement fields such as inpatient department, out-patient department and pharmacy. Hypothesis was set and tested in this study for each of three components of inpatient drug reimbursement in health insurance, i.e. average price level, composition of drugs and their overall volume. Drug price level calculated in this study from 403 selected reimbursement drugs according to the Laspayres methodology revealed faster decline under the new Purchasing Price Reimbursement System than previously by $1.53\%$ on the annual average basis. However, additional 1.4 percent financial burden in the ratio of the total inpatient reimbursement was owed by the health insurer. This was analysed to be a combined result of both 2.0-3.1 percent of reduced reimbursement due to drug price decline and 3.4-4.5 percent of additional reimbursement due to drug volume increase. These results suggest that recalling the Purchasing Price Reimbursement System would not have so much impact upon the health insurer's financial situation given that the current compulsory separation between doctor's prescribing and pharmacist's dispensing is irrevocable.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.9-20
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• 2015

The demand of renewable energy is expected to grow in the long run in spite of current stable lower oil prices. Energy consumption for heating in horticulture greenhouse is large and affects the profits of the farms. This study analyzed the availability of biomass in rural area and proposed the strategies for utilizing the biomass for greenhouse heating. Data reveal the annual average fuel consumption in greenhouses is about 78 TOE/ha. Considering biomass resource in rural areas, agricultural residues are not sufficient to meet the biomass demand from greenhouses. Therefore it is recommended to secure further biomass including wild herbaceous biomass and woody biomass from forest. Based on the conditions of biomass gasification equipment investment and fuel prices, maximum allowable price of biomass turned out about 100,000 KRW/t to be competitive to kerosine. Biomass supply chain should be established for facilitating biomass trading between biomass consumers and biomass producers such as farmers who provide crop residues. An online trading system is an example of the system where consumers who utilize biomass make payments to suppliers and get the information about the biomass. Intermediate collection storages are required to store biomass from distributed sources. Operation of biomass heating systems in demonstration greenhouses is necessary to get information to refine and further develop commercial biomass heating systems. Relatively large greenhouses are desirable to have biomass heating systems for economic viability. The location of the greenhouse farms should be selected within the area where enough biomass resources are available for feeding the biomass facility.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.112-118
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• 2015

These days, there are lots of skyscrapers being constructed in downtown areas. However, it requires columns which have a way heavier load. and far more extensive cross sections of column as well. Therefore, it is hard to lay the foundation in downtown areas. This being the case, composite columns such as CFT column are primarily being used. However, CFT column is occurred of difficult beam-column connection development and lower performance since CFT column is closed cross-section. Especially, the result of the study concerning development of connection details with CFT column and exterior diaphragms are very low in current state. In this study, through developing CFT column-H shape steel beam applicating Y shape plate, set width and depth of Y shape plate which affect structural performance of connection details applicating Y shape plate as main variables, and evaluate structural performance through experiments. And also, design Y shape plate used at experiments as setting allowable stress for tension suggested at design criteria lower than axial force of tension side flange connected Y shape plate, through shape of destruction, verify the structural safety and performance of Y shape plate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.9
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• pp.873-882
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• 2013

The effective way of estimation and analysis of EMI(Electromagnetic Interference) in Wireless Power Transfer System operating at 13.56 MHz is proposed. In this paper methodology of driving magnetic field strength and electric loop current of two antennas which are in free space and on PEC plane using image theory and duality is proposed. Perfect electric conductor(PEC) is planar, infinite in extent, and perfectly conducting plane. And we will refer it as PEC plane. A equivalent circuit model is used to analyze. Using this theoretical analysis, we can derive maximum magnetic field strength of the far-field region numerically using measured data of near-field maximum magnetic field strength. The experimental results using commercial numerical simulation tool are in agreement with the theoretical results. Also, using the derivation of maximum magnetic field strength in the far-field region, we can easily estimate the maximum allowable power dissipation that meets EMI regulations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.543-549
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• 2014

The deflection of reinforced concrete members can be highly variable, due to uncertainties in the characteristics of the concrete. However, current standards do not take this problem into account, instead recommending only the minimum thickness and maximum allowable deflections based on empirical data. This paper is aimed at evaluation deflection variabilities by applying a probabilistic analysis model to a finite element analysis model. To evaluate the variabilities of deflections, a Monte Carlo simulation, which incorporated the eight parameters related to concrete, reinforcement, member size, and tension stiffening. The results showed that lager spans were more sensitive to the deflection due to loads and that as the applied live loads were increases and the slab thickness were decreased, the deflection variability increased.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.6
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• pp.41-52
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• 2007

Earthquake time-history analyses have been carried out for a buried gas pipeline of X65 which is of popular use in Korea. Parameters included are shape of a buried gas pipeline, soil characteristics, single and multiple earthquake input ground motions and burial depths. Predicted response of strain and relative displacement are then compared with allowable strain and displacement capacity calculated by Guidelines for the Seismic Design of Buried Gas Pipelines, KOGAS. Comparative studies show that strains are in general affected by the burial depths together with change of soil conditions. Regarding the relative displacement, while axial relative displacement is not influenced by the burial depths, transverse relative displacement is affected by both burial depths as well as soil conditions. In all, the current study is encouraged to give a useful information for healthy earthquake evaluation of a buried pipeline.

• Computational Structural Engineering
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• v.9 no.2
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• pp.143-151
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• 1996

The optimal design for Electro-magnetic Launcher (EML : Rail Gun) considering structural and electrical constraints are presented. For the structure of EML under high pulsed currency, the cross section is minimized subject to maximum stress of each element(rail, side wall, ceramic, and steel) within allowable stress and preload limits. The electrical constraint is the effective ceramic thickness which prevents the eddy current effect reducing the performance of EML. The stress analysis and optimization procedure of 90mm EML is conducted with ANSYS Code. The optimal design under preload is reduced to 53% of area compared with optimal design without preload. In case of rail with arc angle .theta.=45.deg., the performance of EML is the best among the other rail arc angles. The optimal design for rail with arc angle .theta.=45.deg., results in the reduction of 9% of area and 10.4% of deformation compared with Fahrenthold's design. The optimal preload 59.8MPa is much lower than Fahrenthold's design(186MPa). The results show that the optimal design of EML meets the design requirements.

• Aerospace Engineering and Technology
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• v.10 no.2
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• pp.20-28
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• 2011

The electro-optical payload of a low-earth orbit satellite is thermally decoupled with the bus, which supports a payload for a mission operation. The payload has a cooling unit of FPA(Focal Plane Assembly) which has a thermal behavior increasing its temperature instantly during an operation in order to dissipate a waste heat into the space. The FPA cooling unit should include a radiator and heatpipes with a sufficient performance in worst hot condition, and a heater design to maintain its temperature above a minimum allowable temperature in the worst cold condition. In this paper, we analyzed the thermal requirements and the heater design constraints from the thermal analysis results for the current thermal design of the FPA cooling unit and the design elements of the better heater design were found.

• Journal of Communications and Networks
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• v.15 no.1
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• pp.77-86
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• 2013

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the single-channel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution.We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.