• Journal of the Korean Institute of Educational Facilities
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• v.16 no.4
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• pp.71-78
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• 2009

After the introduction of the 7th revision of curriculum, educational facilities have been requested to change to face new curriculums and have been planned. But, it is actual condition that researches of curriculum and facilities seem to be insufficient. This research will re-establish in an angle of space-syntax based on existed research for home-base area of variation type in high school according to the 7th curriculum. And the each specific character of home-base area representing each type and strong / weak points of area structure of each home-base will be analyzed. And analysis result with the model of variation type in high school visit the on-the-spot inspection result which leads and comparison and with his interview back it leads and currently there is the objective to the evaluation the variation type in high school home-base which is planned regarding the suitable in real use. Each case to the school I visited the scene, not all high schools applied the 7th curriculum courses. Therefore, it is also home-base space capabilities were not being properly utilize. According to 7th curriculum, one of Hall-type home-base and Room-type home-base can be suitable when integration is higher. However, the way the current operational training, it is the best that Distributed-type home-base needs to be included in each curriculum block.

• Laser Solutions
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• v.2 no.3
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• pp.42-51
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• 1999

This research was conducted as a fundamental study to apply tailored blank welding technique into automotive production process. The materials used in this study were 2.0mm thickness low carbon steel sheets and 1.2mm Zn-coated low carbon steel sheets. To ensure the reproducibility and to consider various factors, experiments were. conducted by applying Taguchi experimental method with 6 factors. Every welding process was repeated 3 times to offset the effect of uncontrolled factors. Elongation and LDH(Limited Dome Height)were measured to evaluate formability of specimens and Optical microscopy, XRD, SEM, and EDS analysis were performed to observe the microstructures and to determine the solidification mode in the weld. The elongation of specimen welded with optimum condition was 83% of base metal, and LDH was 84% of base metal. In case of laser treated specimen where Zn coating was removed, elongation was 85% of base metal, and LDH was 85% of base metal. In fusion zone, phases were consisted of quasi-polygonal ferrite, banitic ferrite, and martensite.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.97-104
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• 2014

Automobile trunk latches enable trunks to be opened and closed by a latch mechanism, which can be selectively positioned between a locked condition and an open condition. To maintain structural and electronic performance of the trunk latch, the latch needs to endure impact load that occurs in its open and close motion, and a dynamic mechanism needs to be electronically controled by a contact switch connected with a small DC motor. A base plate, which is the most important component relating to the structural safety, commonly uses a high stiffness material SAPH440-P with high manufacturing cost. In this paper, through structural analysis and optimization, production cost is significantly reduced by replacing SAPH440-P used in some region of the base plate with engineering plastic PBT GF 20%. The optimized contact switch reduces difference between distributed pressures of its two legs, which leads to improve the electronic performance of the trunk latch.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.112-122
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• 1996

In order to monitior machine tool condition and diagnose alarm states due to electrical and mechanical faults, and expert system using diagnostic parameters of NC machine tools was developed. A model-based knowledge base was constructed via searching and comparing procedures of diagnostic parameters and state parameters of the machine tool. Diagnostic monitoring results generate through a successive type inference engine were graphically displayed on the screen of the console. The validity and reliability of the expert system was rcrified on a vertical machining center equipped with FANUC OMC through a series of experiments.

• Tribology and Lubricants
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• v.17 no.2
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• pp.146-152
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• 2001

Environmentally adapted synthetic base oils of polyalkylene glycols (PAGs) and polyol esters (POEs) show a high polarity because of their functional groups containing oxygen atom. The lubricating performance of these polar base oils was investigated by using a four-ball tribometer under boundary lubrication condition. Four polyalkylene glycols and five polyol ester base oils were used as sample base oils of high polarity. A mineral oil (MO) and alkylnaphthalene (AN) were used as low polarity base oils. Tricrecylphosphate (TCP) was added to all the base oils, in the range of 10 mmol/L-2000 mmol/L, as an antiwear additive. All the TCP-for-mutated base oils showed optimum concentration characteristics for minimizing wear. The order of optimum concentration of all the base oils was in a good accordance with the order of relative stability of TCP in base oils. The interaction model on solvation between additive and different polar base oils can expect the stability order of TCP. Thus, the model on solvation can explain well the order of optimum concentration of all the base oils, by using the effect of polarity (dielectric constant, $\varepsilon$) and molecular size (molecular weight, MW) of them on stability of TCP in polar base oils. Finally, a good correlation of the optimum concentration for all the base oils was obtained when it was arranged as a function of C∝(M $W_{Base Oil}$/M $W_{TCP}$)$^{-2}$.71/.($\varepsilon$$_{Base Oil}$)$^{3.38}$ by these two parameters.s..

• Journal of Industrial Technology
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• v.26 no.B
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• pp.29-34
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• 2006

A convective, radiating rectangular fin is analysed by using the one dimensional analytic method. Instead of constant fin base temperature, heat conduction from the inner wall to the fin base is considered as the fin base boundary condition. Radiation heat transfer is approximately linearized. For different fin tip length, temperature profile along the normalized fin position is shown. The fin tip length for 98% of the maximum heat loss with the variations of fin base length and radiation characteristic number is listed. The maximum heat loss is presented as a function of the fin base length, radiation characteristic number and Biot number.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.1
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• pp.63-69
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• 2006

This study deals with the friction welding of A2024- T6 to A6061- T6; The friction time was variable conditions under the conditions of spindle revolution of 2000rpm, friction pressure of 50MPa, upset pressure of 100MPa, and upset time of 5.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied, of friction weld, and so the results were as follows. 1. When the friction time was 1.5seconds under the conditions, the maximum tensile strength of the friction weld happened to be 292MPa, which is $94.2\%$ of the base material's tensile strength(310MPa). At the same condition, the maximum shear strength was 2l2MPa, which is equivalent to $103\%$ of the base material's shear strength (205MPa). 2. At the same condition, the maximum vickers hardness was Hv 146 at A2024- T6 nearby weld interface, which is higher Hv3 than condition of the friction time 0.5seconds, and the maximum vickers hardness was Hvl20 from weld interface of A6061-T6, which is higher Hv28 then base material's. 3. The results of microstructure analysis show that the structures of two base materials have fractionized and rearranged along a column due to heating and axial force during friction, which has affected in raising hardness and tensile strength.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.4
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• pp.303-312
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• 1999

An investigation of the CrMoV rotor steel weldment which experienced by cyclic thermal aging heat treatment and as-received condition was performed. This evaluation was carried out to confirm whether this type of weldment is appropriate for the service environment in terms of microstructural examinations, microhardness measurements and tensile tests. The cyclic thermal aging heat treatment, containing continuous heating and cooling thermal cycle was programmed to simulate the real rotor service condition. The heat treatment was performed for 40 cycles(5920hrs). The results indicated that the weldment was composed of 4 different regions such as heat affected zone of the base metal, butter weld(initial weld), full thickness weld(final weld) and the base metal. The double welding process was applied to eliminate the susceptibility of reheat cracking at heat affected zone of base metal. The grain refinement at the HAZ due to the welding process could reduce the possibility of cracking susceptibility, but its tensile properties was appeared to be low due to the weld metal in as-received condition. The benefit effect, grain refinement was extended with carbides coarsening during the cyclic thermal aging heat treatment. However the poor mechanical properties of the weldment was more degraded as undergoing the heat treatment.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.4
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• pp.15-26
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• 2013

In recent years, river maintenance projects using natural methods have been continuously implemented in urban areas and methods emphasizing ecology are being developed and constructed in revetment areas. However, there is insufficient technical review on the hydraulic stability of those revetment methods during the event of flood. Therefore, a hydraulic analysis is necessary for the stream where revetments are applied. This study was conducted to develop an objective test method for the hydraulic stability of green revetment media. For this purpose, hydraulic model tests were performed for the green base materials for revetments. Tests were conducted using experimental devices for the hydraulic model which were installed to simulate the rapid current during the flood. Loss of soil by the hydraulic condition was compared and analyzed with that of dry green revetment media, and the evaluations were made on the corrosion resistance, tractive force, and contractile force. Test results showed that green revetment media had higher corrosion resistance in non-vegetation condition compared to dry green revetment media, and the loss of base materials by the rooting of vegetation showed significant reduction by the vegetation. In addition, results of the allowable tractive force of the base material indicated it is relatively stable in vegetation condition but scouring can occur in non-vegetation condition. Therefore, the development of vegetation in revetment areas is anticipated to be effective for the stability of revetment areas by reducing external forces interacting with the corrosion resistance and stream bank. The green revetment media in expected to contribute to the stability of revetment areas.

• International Journal of Automotive Technology
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• v.3 no.1
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• pp.41-46
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• 2002

Effect of secondary air injection (SAI) on hydrocarbon reduction has been investigated in a single cylinder Sl engine operating at cold-steady/cold-start conditions. The hydrocarbon emission and exhaust gas temperature with and without catalytic converter were compared with continuous and synchronized SAIs, which injected secondary air intermittently into exhaust port. Effects of SAI location, SAI pressure, SAI timing, and location of catalytic converter have been investigated and the results are compared for both SAls with base condition. At cold-steady condition, the rate of HC reduction increased as the location of SAI was closer to the exhaust valve for both synchronized and continuous SAls. The emission of HC decreased with increasing exhaust-A/F when it was rich, and was relatively insensitive when it was lean. The timing of SAI in synchronized SAI had significant effect on HC reduction and exhaust gas temperature and the synchronized SAI was found to be more effective in HC reduction and exhaust gas temperature compared to the continuous SAI . At cold-start condition, when the catalytic converter was located 20 cm downstream from the exhaust port exit, the catalytic converter warm-up period for both SAls decreased by about 50%, and the accumulated hydrocarbon emission during the first 120 s decreased about by 56% and 22% with the synchronized and continuous SAIs, respectively, compared to that of the base condition.