• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.386-389
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• 1999

Effect of high voltage screening was examined on mechanical strength of titania ceramics with two different surface roughness. Roughly finished sample showed degraded mechanical strength meaning that the introduced flaw played the role of starting point of mechanical fracture. On such sample, electrically weak parts were eliminated by applying a screening field. Mechanical strength measurement on survived parts revealed that after screening the Weibull plots bended to become a convex curve while plots at high strength region were almost the same. This result means that relatively low mechanical strength parts were eliminated by the electrical method. As a result the Weibull modulus calculated from all the data increased, demonstrating the effect of high voltage screening on titania ceramics containing fracture controlling surface flaws. Roles of the surface flaw such as a common weak spot for both failures are disscussed in relation to the electric field concentration similar to that of mechanical stress.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1057-1062
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• 2000

The purpose of this study is to practice the method which can estimate 28-days strength of concrete in advance. This method is made for reliant quality control. Based on existing experiment, concrete that flyash added and normal concrete are placed into wall structure, and it is examined the difference between experiment use concrete and field use concrete. The result of this study are as follows : 1) Core test specimen have 10% lower strength to standard curing specimen. 2) At 28-days accelerated strength by microwave, average 35% in normal concrete, average 23% in flyash added concrete. 3) At coefficient of determination between compressive strength and accelerated strength, 0.84 in normal concrete core, 0.86 in standard curing normal concrete, 0.86 in flyash added concrete, 0.90 in standard curing flyash added concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.28-29
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• 2013

When concrete was hardened, it should had considered a crack to make internal stress by hydration heat. For control of crack, admixture was use to change cement because hydration heat was effect to cement. High strength mass concrete had much hydration heat with high volume of cement. It was necessary to reduce hydration heat in construction method. In this study, it evaluates hydration heat, compressive strength of transfer concrete girder regard to field construction type such as separation, whole etc. Also, we test compressive strength of concrete with core and mold specimen.

• Bulletin of the Korean Chemical Society
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• v.16 no.7
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• pp.613-619
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• 1995

The influence of carrier solutions on particle retention was studied by varying surfactants and ionic strength in flow field-flow fractionation. Experiments were made with five different submicron polystyrene latex standards at three different types of surfactants and seven different ionic strengths. Departures in particle retention from the general theory were observed. At low ionic strength, it is shown that migrating sample zone is clearly lifted away from the ideal equilibrium height and that the repulsive interaction dominates between the particle and the channel wall. As ionic strength increases up to a certain level, particle retention becomes closer to the general theory. Further increase in ionic strength is shown to prolong the retention. An optimum regime of ionic strength is also suggested with the proper choice of surfactants.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.1
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• pp.85-91
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• 2021

With the social atmosphere of respect for human life and the increasing interest in safety of field workers, research and development is underway in various ways to transform direct live method into indirect live method in the field of distribution. As part of this measure, it was necessary to convert electric pole and complex facilities work from machining power distribution to indirect live operation, and install a straight connecting sleeve that connects cut wires for by-pass method, but it failed to meet the tensile strength standard when constructing a sleeve constructed by direct method. In this paper, the design factors were derived based on the case of overseas similar sleeves and the tensile strength evaluation of each variable was performed, based on the analysis of these test results, the method for securing tensile strength of straight-line access sleeves for indirect running was presented.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.41-42
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• 2023

The physical performance of high-strength concrete deteriorates when exposed to high temperatures such as fire. In particular, in the case of ultra-high-strength concrete, there is a high possibility of explosion due to internal water pressure and thermal expansion due to the tight internal structure. In this paper, a fire resistance certification test was conducted for field application of ultra-high-strength fire-resistant concrete, and the fire resistance performance (temperature rise of main rebar) was compared according to the structural concrete cover thickness. As a result, when the covering thickness was 40 mm, three structures did not meet the certification standards, and when the covering thickness was 50 mm, all structures met the fire resistance certification standards.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.216-218
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• 2001

This paper deals with the control of magnetic field around the down conductor of lightning protection systems. The magnetic field strength in the vicinity of down conductor is shown to drop off rapidly with distance from the down conductor and is reversely proportional to the number of down conductor. Also the magnetic field strength is decreased in the structures as the down conductor is installed with the symmetrical arrangement, and it is zero at the center of symmetry. The magnetic field strengths for the symmetrical arrangement of two down conductors are less than one half compared with that for a down conductor. A proper arrangement of down conductor can reduce or cancel the magnetic field in a restricted place where information-oriented and computerized facilities are densely installed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.262-262
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• 2013

In surface chemistry area, many scientists studied the electrochemical reaction by changing work-function of metal; however, these methods had the weakness that it did not create the electric field. Unlike earlier studies, our capacitor-method makes a strong electric field in ice film. This electric field was induced by soft landing $Cs^+$ ions on ice film, and the strength was measured by the vibrational Stark shift of acetonitrile. In our system, the electric field strength is $10^9$ V/m and it is almost same in the electrochemical cell. This capacitor model provides new method to investigate the electrochemical reaction in vacuum system.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.47-49
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• 2002

At present, the trend of magnetic field strength in MRI system is dramatically changing. In early 70, the only low field (<0.5T) was developed. It was technically difficult to develop the high field system. At that time, people believed that the fine MR imaging could not be obtained in the high field MR system due to the magnetic susceptibility effect. However, 1.5T system was evolved at the end of 80, and used for clinical usage. Thus, it was proved that the signal to noise ratio (SNR) could be greatly contribute to enhance the image quality. And, the results of functional MRI and MR spectroscopy could be improved in the higher field MR system. So, 8T system was eventually developed in Ohio State University Hospital at the end of 90. Therefore, there is no doubt that the system with the ultra high magnetic field strength will be developed near future in 21 century.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.6
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• pp.539-543
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• 2011

Recently, to reduce the noise and vibration levels of ships, high skewed marine propellers with thinner thickness are adopted widely, however, such propeller design trend causes to reduce the strength of blades. Propeller blades are rotating continuously in irregular wake field of ships. So, it is necessary to examine the strength of them precisely including from a viewpoint of fatigue strength. In present paper, the fatigue strength of propeller blades was investigated. Firstly, fatigue tests for Al Bronze, the representative propeller material, were carried out. The S-N curve was obtained for the assessment of the fatigue crack initiation life. And the material properties C, m for the fatigue crack propagation analysis based on the Paris' equation were derived. For the 2nd stage, the structural responses of propeller blades in irregular ship wake field was carried out using the finite element analysis code. And the fatigue strength of propeller blades were considered based on the calculated stress levels and material characteristics for fatigue strength.