• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.7-18
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• 2005

Over the past twenty years, the maintenance system has been developed and its importance has been increased. For the effective maintenance of the urban transit, we have developed the maintenance system based on the concept of RCM(Reliability Centered Maintenance). RCM analysis is a systematic approach to developing a cost-effective maintenance strategy based on the various components's reliability of the system in question. It is performed according to process that includes the following steps; definition of function and functional failures of the systems, construction of RB D(Reliability Block Diagram), performance of FMEA(Failure Modes & Effects Analysis) and calculation of the reliability index. The final process of RCM is to determine appropriate failure maintenance strategies. This paper aims to define the procedure of maintenace based on the concept of RCM for urban transit. The key for a successful maintenance system is an automated scheduling to the maximum extent possible and timely executions. The developed system issues maintenance plan and repair request based on analyzed data and maintenance experience.

• International Journal of Automotive Technology
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• v.2 no.1
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• pp.1-7
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• 2001

This paper presents further investigation into the effect of over-expansion cycle in a spark-ignition engine. On the basis of the results obtained in previous studies, several combinations of late-closing (LC) of intake valve and expansion ratio were tested using a single-cylinder production engine. A large volume of intake capacity was inserted into the intake manifold to simulate multi-cylinder engines. With the large capacity volume, LC can decrease the pumping loss and then increase the mechanical efficiency. Increasing the expansion ratio from 11 to 23.9 with LC application can produce about 13% improvement of thermal efficiency which was suggested to be caused by the increased cycle efficiency. The decrease of compression ratio from 11 to 5.5 gives little effect on the thermal efficiency if the expansion ratio could be kept constant. Thus, the expansion ratio is revealed to be a determining factor for cycle efficiency, while compression ratio is no more important, which suggests the usefulness of controlling the intake charge with intake valve closure timing. These were successfully explained by simple thermodynamic calculation and thus the mechanism could be verified by the estimation.

• Korean Journal of Veterinary Research
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• v.38 no.1
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• pp.201-208
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• 1998

Piglets' diarrhea is one of the major causes of economic loss in Korean swine industry. To prevent this serious and persistant problem, we have developed systemic farm evaluation and analysis program. The program consists of the checklist and the computerized program. The items of the checklist are selected on the basis of various causative factors related with the piglets' diarrhea including sanitational status, nutritional management, or farm environment. The checklist is composed of 30 items including 6 factors on facility, 8 factors on environment, 6 factors on nutrition and 10 factors on sanitation, respectively. Minimum 1 to maximum 10 points was assigned to each item depending on level or status of farm. The scores calculated by sum of points obtained from each item could find out the problems which the farm was confronted with. To investigate the applicability of a program 150 swine farms raising over 500 heads were selected from 7 provinces throughout the country and surveyed. There were significant correlations between the piglets' diarrhea and the scores of the checklist. Based on above results we revised the checklist which consisted of 22 items including 5 factors on facility, 7 factors on environment, 3 factors on nutrition and 7 factors on sanitation. After that we composed a computerized diagram out of each point of an item which showed and indicated weak factors to be improved promptly. Our present study suggested that this newly established swine farm evaluation program would be a very efficient way to find out the problems and support the systemic control program of the piglets' diarrhea for swine farms.

• Korean Medical Education Review
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• v.10 no.2
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• pp.25-44
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• 2008

Objectives: Through using of the strong research method like a Randomized Controlled Trial: RCT, we have to heighten quality of Medical Education study. I'd like to introduce "CONSORT", which stands for Consolidated Standards of Reporting Trials. Contents: Preventive Service Task Force(200l) in USA proposed Levels of evidence for enlarging evidence-based Practice: EBP. And the CONSORT was introduced, which encompasses various initiatives developed by the CONSORT Group to alleviate the problems arising from inadequate reporting of randomized controlled trials (RCTs). the CONSORT has 13 guides like these: 1. How participants were allocated to interventions 2. Scientific background and explanation of rationale 3. Eligibility criteria for participants. The settings and locations where the data were collected. 4. Precise details of the interventions intended for each group and how and when they were actually administered 5. Specific objectives and hypotheses 6. Clearly defined primary and secondary outcome measures, When applicable. any methods to enhance the quality of measurements (e.g., multiple observations, training of assessors) 7. How sample size was determined. When applicable, explanation of any interim analyses and stopping rules 8. Method used to generate the random allocation sequence, Details of any restriction [of randomization] 9. Method used to implement the random allocation sequence 10. Who generated the allocation sequence, who enrolled participants. and who assigned participants to their groups 11. Whether or not participants, those administering the interventions, and those assessing the outcomes were blinded to group assignment. If done, how the success of blinding was evaluated 12. Statistical methods used to compare groups for primary outcome(s), Methods for additional analyses, such as subgroup analyses and adjusted analyses 13. Flow of participants through each stage (a diagram is strongly recommended) Specifically, for each group report the numbers of participants randomly assigned. receiving intended treatment, completing the study protocol. and analyzed for the primary outcome. Results and Conclusion: Randomized Controlled Trial: RCT guided of CONSORT will contribute to do stronger evidence-based medical studies.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.3
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• pp.171-180
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• 2010

Analysis on the temporal variation of the stratification is carried out by using the continuous water temperature and salinity data observed in the coastal monitoring buoy in Mikawa Bay, Japan. The main analysis results are as follows. The stratification pattern have an obvious and dominant 1-year period variation and the occurrence frequency (days) are exponentially decreased as the stratification intensity (SI) defined as the density difference between surface and bottom layers linearly increases. The frequency distribution function of the SI is presumably close to the log-normal function type or exponential function type. From the water temperature and salinity scatter diagram analysis, the line and loop type patterns are shown in the bottom and surface layers, respectively. In addition, the analysis of the SI estimation show that the error bound in case of using the weekly-monitoring data is about 4.45 times greater than that in case of using the continuous (daily) monitoring data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.7
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• pp.691-696
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• 2004

The electronic state and chemical bonding of $\beta$-MnO$_2$ with transition metal dopants were theoretically investigated by DV-X$_{\alpha}$ (the discrete variational X$_{\alpha}$) method, which is a sort of the first principles molecular orbital method using the Hartree-Fock-Slater approximation. The calculations were performed with a $_Mn_{14}$ MO$_{56}$ )$^{-52}$ (M = transition metals) cluster model. The electron energy level, the density of states (DOS), the overlap population, the charge density distribution, and the net charges, were calculated. The energy level diagram of MnO$_2$ shows the different band structure and electron occupancy between the up spin states and down spin states. The dopant levels decrease between the conduction band and the valence band with the increase of the atomic number of dopants. The covalency of chemical bonding was shown to increase and ionicity decreased in increasing the atomic number of dopants. Calculated results were discussed on the basis of the interaction between transition metal 3d and oxygen 2p orbital. In conclusion it is expected that when the transition metals are added to MnO$_2$ the band gap decreases and the electronic conductivity increases with the increase of the atomic number of dopants. the atomic number of dopants.

• Journal of the Korean institute of surface engineering
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• v.46 no.5
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• pp.181-186
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• 2013

We performed plasma spraying for 2001 (Bi:Cu = 2:1), 0212 (Sr:Ca:Cu = 2:1:2) oxide powders. $Bi_2Sr_2CaCu_2Ox$ (2212) superconductor has been prepared by PMP-AT (partial melting process-annealing treatment). The 2212 phase is synthesized between Sr-Ca-Cu oxide coating layer (0212) and Bi-Cu oxide coating layer (2001) by movement of partial melted Bi on 2001 layer and the diffusion reaction (Cu, Sr, Ca) after PMP-AT. There are two different coating layers on joining process. The one is ABAB coating layers and the other is BAAB coating layers by arrangement of 2001 (A), 0212 (B) layers. We performed heat treatment these two different coating layers processes under same PMP-AT conditions. We obtained Bi-2212 superconducting layers at each experimental condition, and the result of MPMS, the critical temperature was showed about 78 K. But the microstructure images and result of EDS as each experimental variable were showed about the qualitatively different Bi-2212 superconducting phases. We also deduced the generation mechanism of Bi-2212 superconducting layer as a result of these experimental data, microstruc ture images, EDS data and phase diagram.

• Journal of the Korean Applied Science and Technology
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• v.14 no.3
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• pp.23-28
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• 1997

The phase diagram for the surfactant mixture system of N-dodecanocyl-N-methyl amido polyolcarboxyl alkyl ether(DGC)/N-dodecanocyl-N-alkyl glucamine(DG)/water was studied usingpolarized microscopy, differential scanning calorimetry(DSC) and rheological measurements respectively. Using polarized microscopy, the textures of liquid crystal phases obtained at various surfactantconcentrations were investigated as a function of surfactant concentration and temperature, and phasetransitions between anisotropic liquid crystal phases and isotropic liquid phase were examined usingDSC measurements. Viscoelastic properties of surfactant solutions determined between hexagonal andlamellar liquid crystal phase by rheological measurements were approximately consistent with the resultsobtained by polarized microscopy and DSC. In the study for the phase of DGC/DG(5:5 mol ratio)/water system. It could be found that the hexagonal liquid crystal phase appeared at 25${\sim}$60wt％ ofsurfactant, the cubic liquid crystal phase at 50${\sim}$65wt％ and the lamellar crystal phase at above 70wt％.

• Korean Journal of Construction Engineering and Management
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• v.9 no.3
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• pp.126-135
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• 2008

The purpose of this study is to develop the efficient information system for managing owner's requirement(O/R) throughout the design phases. In order to derive an improvement, current status of O/R management both in domestic and foreign design company has been analyzed. Through the literature reviews and interviews with experts, the Information on design process and detailed activities were investigated. Based on the basic research, inputs, outputs and participants were defined and information flow diagram was drawn. O/R's were categorized according to comprehensive interviews with specialists, and a prototype system was suggested. Conducting systematized O/R management will improve the confidence of owners' role on design, reduce re-work in design tasks, and finally elevate design quality.

• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.33-41
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• 2018

Soil internal erosion is a phenomenon in which fines attached to the solid skeleton are detached by fluid flow, and this continuous fine migration weakens the hydro-mechanical characteristics of the ground structure. This paper proposed governing equations for fine migration in pore spaces and its related scheme for the numerical analysis. Phase diagram for fine particles includes three different states: detached fines in the liquid phase ($c_e$), attached fines in the solid phase (${\sigma}_a$), and pore-clogged fines in the solid phase (${\sigma}_s$). Numerical formulations for finite element method are developed based on the hydraulic governing equations of pore fluid and fine migration. This study proposed a method of estimating model parameters for fine detachment, attachment, and clogging from 1D erosion experiments. And it proposed an analytical formula for hydraulic permeability function considering fine clogging. Numerical analysis of the previous erosion test developed the numerical scheme and verified the adequacy of fine migration models.