• 한국전기전자재료학회논문지
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• 제36권3호
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• pp.280-285
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• 2023

A breakdown voltage and breakdown electric field of the transformer insulating oil of liquid dielectric were studied in uniform electric field and non-uniform electric field and the transformer insulating oil was observed by the process reached breakdown. Insulation performance evaluation of the liquid dielectric was evaluated at the electrode spacing of 2.5 mm under the conditions of domestic and international standards (KS C IEC 60156), so a comparative review was conducted at the electrode spacing of 2.5 mm. When the electrode spacing is 2.5 mm, the average breakdown voltage is 38.5 kV for sphere-sphere electrodes, 26.6 kV for plate-plate electrodes, 22.9 kV for needle-needle electrodes, and 24.3 kV for sphere-needle electrodes. 23.7 kV for the sphere-plate electrode, and 20.7 kV for the needle-plate electrode. From these results, it can be seen that the average value of the breakdown voltage at the electrode spacing of 2.5 mm, in ascending order, is sphere-sphere, plate-plate, sphere-needle, sphere-plate, needle-needle and needle-plate. It was found that the breakdown voltage of the unequal field was lower than that of the equal field.

• 한국농공학회논문집
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• 제60권6호
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• pp.111-119
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• 2018

The air-void is known to be one of the influencing factors for estimating long-term performance of asphalt concrete. Most of all, confirming air void or density of pavement layer is important for quality control of field compaction level of asphalt concrete pavement. In this study, a non-nuclear type non-destructive density gage (NDDG) was used to estimate compacted air-voids of asphalt pavement as a non-destructive test method. Asphalt concrete slab specimens were prepared using 6 types of asphalt mixes in laboratory (lab) for lab NDDG test. Four different base structure materials were used to find out if there were any differences due to the type of base structure materials. The actual air-voids and NDDG air-voids were measured from 6 asphalt concrete slabs. Four sections of field asphalt pavements were tested using the NDDG, and actual air voids were also measured from field cores taken from the site where the NDDG air-void was measured. From lab and field experimental tests, it was found that the air-voids obtained by NDDG were not the same as the actual air-voids measured from the asphalt concrete specimen. However, it was possible to estimate air voids based on the relationship obtained from regression analysis between actual and NDDG air voids. The predicted air-voids based on the NDDG air-voids obtained from 50mm depth were found to be reliable levels with $R^2{\fallingdotseq}0.9$. Therefore, it was concluded that the air-voids obtained from NDDG could be used to estimate actual air-voids in the field asphalt pavement with a relatively high coefficient of determination.

• 수산해양교육연구
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• 제25권4호
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• pp.937-957
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• 2013

This study was conducted for the purpose of developing the UCC project teaching and learning model based on the rationale which are applicable effectively in the field of university education. Firstly, we have designed the rationale based on the research of documents and preceding researches about teaching method models. Secondly, we have developed the UCC project teaching and learning model. the UCC project teaching and learning model based on the rationale was assessed by the professional formative evaluation group and tested in the field of university education in advance and thereafter. It was finally rectified and supplemented. Particularly, any corrections were to be made repeatedly in the stage of developing of the UCC project. And also, during the assessment and arrangement process, it was designed for the study participants to feel a sense of achievement as learners who combine knowledge and attitudes toward participants'subjects of the curriculum and professional vocational skills by performing the nursing science training scene which could happen in the field. Thirdly, the final version of the UCC project teaching and learning model was verified in its effectiveness by being applied in the field of the nursing science education in the $2^{nd}$ step. As a result, we noticed that learners diverse abilities were improved through systemic process and performing elements such as teaching plan which was needed for designing the UCC project in the field, making storyboard and skills for making video contents. We hope that the UCC project teaching and learning model in this study will be used by the students for designing, developing and utilizing educational UCCs which are necessary in industrial fields and it will contribute for training university students as professionals having the practical skills in the field.

• 한국소음진동공학회논문집
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• 제23권3호
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• pp.274-281
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• 2013

Field measurement method of heavy/soft impact sound pressure level which is regulated in JIS and ISO has been using in Korea, Japan and Canada. It is reported that heavy/soft impact sound pressure level was varied by the sound field condition of receiving room such as sound absorption power and room volume. In this study, it is checked that heavy/soft impact sound pressure level was affected by the receiving sound field condition. Rubber ball and bang machine sound pressure level was measured in the vertically connected reverberation chamber. In oder to check the effect of receiving sound field on heavy/soft impact sound pressure, sound absorption power was changed with polyester sound absorption blankets with air space and glass wool. The reverberation time at 1 kHz band was changed from 10 s to 0.2 s by sound absorption material. Rubber ball sound pressure level measured without sound absorption material was 58 dB in $L_{i,Fmax,AW}$, but the level was 46 dB with sound absorption treatment. From this result, it is confirmed that sound field correction method is needed in the heavy/soft impact sound pressure level measurement method using bang machine and rubber ball.

• 한국도로학회논문집
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• 제19권2호
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• pp.67-74
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• 2017

PURPOSES : The objective of this study is to ascertain the curing period of cementless cold central plant recycled asphalt base-layer, using mechanical analyses and specimen quality tests on the field. METHODS : Cold central plant recycled asphalt base-layer mixture was produced in the plant from reclaimed asphalt, natural aggregate, filler for the cold mix, and the modified emulsion AP using asphalt mix design and plant mix design. In order to examine the applicability of the curing period during the field test, the international standards for the possibility of core extraction and the degree of compaction and LFWD deflection were analyzed. Moreover, Marshall stability test, porosity test, and indirect tensile strength test were performed on the specimens of asphalt mix and plant mix design. RESULTS : The plant production process and compaction method of cementless cold central plant recycled asphalt base-layer were established, and the applicability of the optical moisture content for producing the mixture was verified through the field test. In addition, it was determined that the core extraction method of the conventional international curing standard was insufficient to ensure performance, and the LFWD test demonstrated that the deflection converges after a two-day curing. However, the back-calculation analysis reveals that a three-day curing is satisfactory, resulting in a general level of performance of dense asphalt base-layer. Moreover, from the result of the specimen quality test of the asphalt mix design and plant mix design according to the curing period, it was determined that the qualities satisfied both domestic and international standards, after a two-day curing. However, it was determined that the strength and stiffness after three-day curing are higher than those after a two-day curing by approximately 3.5 % and 20 %, respectively. CONCLUSIONS:A three-day curing period is proposed for the cementless cold central plant recycled asphalt base-layer; this curing period can be demonstrated to retain the modulus of asphalt-base layer in the field and ensure stable quality characteristics.

• 한국도로학회논문집
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• 제19권2호
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• pp.103-112
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• 2017

PURPOSES : In this study, field performance evaluation of crack treatment of pavement and the feasibility of surface treatment of pavement are presented. The performance and cost of preventive maintenance methods have been previously verified, and the methods are being used in many developed countries and cities. However, the performance and cost of the system have not been verified in domestic, field applications. Therefore, in order to improve performance, the field performance is evaluated, and a reasonable cost is proposed. METHODS : Visual Inspection was conducted to evaluate the field application and performance of the preventive maintenance method. In addition, the PCI index was calculated from the results of visual inspection of the application area of the surface treatment method, and the performance life of each method was predicted. For the economic evaluation, life cycle cost analysis was performed using the life cycle cost analysis program. RESULTS :In order to evaluate and quantify the field performance of crack repair material, the residue condition of the pavement surface after crack treatment, rather than the performance of the material, is evaluated. In addition, the crack resistance and performance life of surface treatment methods are evaluated. The cost of currently available treatment methods are compared to the common pavement cut and overlay method, and it is determined that the preventive method is not economical based on life cycle cost analysis. CONCLUSIONS :Because of the characteristics of cracking, it is necessary to conduct the evaluation of currently applied methods and the analysis of the cause of damage, by visual inspection. Moreover, in order to evaluate the performance and economic suitability of the currently applied surface treatment methods, it is necessary to acquire information on application sections by monitoring their long-term conditions and performance.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 추계학술대회
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• pp.202-206
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• 1996

An experimental study of the characteristics of the repulsiveytype magnetic bearing using high Tc superconductor is presented. In field cooling superconductor has the position-stability due to a flux pinning effect and the strong damping due to hysterisis, while in zero field cooling it has the only strong repulsive force due to Meissner effect. Lift force in superconducting levitation has a hysterisis characteristics, and it is the dissipation of energy, the mechanism of damping. As the relative linear velocity between a magnet and a superconductor increases, the area of the hysterisis loop becomes smaller. It means the decrease of damping. In field cooling, the static stiffness is very nonlinear in smaller than initial gap, but almost linear in larger than initial gap.

• 한국IT서비스학회지
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• 제13권2호
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• pp.71-82
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• 2014

Exhibitions are important sales promotional method commonly used by the marketer of industrial products. Exhibition utilized as a means of effective marketing tools, company's interest and demand is rising. Especially in recent years, visitors' activity within the exhibition space can be monitored in real time by applying near-field sensing technology such as RFID, NFC, RQ code. Exhibition organizers are also applying the near-field sensing technology in order to attract the participating companies and visitors. With the introduction of near-field sensing technology, the exhibition has been a lot of changes occur in the exhibition environment. However absence of performance indicators to measure new exhibition environment which adopt ubiquitous technology, still the exhibition performance is not properly measured. In this study, we use the Delphi technique with the performance indicators based on previous research, and propose performance indicators for measuring achievement of exhibition in the smart-exhibition environment.

• 한국군사과학기술학회지
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• 제4권2호
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• pp.17-29
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• 2001

In this paper, we designed the hybrid path generation method which is named CAPM(Continuous path generation method based on artificial Potential field) that is able to be used in the obstacles environment. This CAPM was designed so that it puts together two obstacle avoidance algorithm-the continuous path generation method(CPGM) and the artificial potential field method(APFM). Here, the CAPM generate the safety path using continuous path curvature. But, this method has demerits when used in obstacles environment in which are closely located. Another method which is named the APFM generates the path with the artificial potential field in the obstacles environment. But, It has local minima in certain places and unnecessarily calculates the path in which obstacles are not located. So, the CAPM was designed for autonomous underwater vehicle(AUV) obstacle avoidance. As the result of simulation, it was confirmed that the CAPM can be applied to a safe path generation for AUV.

• 대한전기학회논문지
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• 제36권6호
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• pp.424-429
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• 1987

It has been observed that the reduction rate of the inversion layer carrier mobility due to the increase of the longitudinal electric field(drain to source direction) decreases as the transverse electric field increases. The effects of this physicar phenomenon to the I-V characteristics of the short channel NMOSFET are studied. It is shown that these effects increase the drain Current in the saturatio region, which agrees with the genarally observed decrepancy between the experimental I-V charateristics and the I-V modeling which dose not include this physical phenomenon. Also it is shown that this effect becomes more important when the device channel length decreases and the device operates in the high electric field range.