• International Journal of Highway Engineering
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• v.17 no.3
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• pp.27-33
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• 2015

PURPOSES : To ensure appropriate RCC properties with sufficient strength development and workability, it is necessary to secure a proper level of consistency. It is also necessary to secure maximum dry density, which is an important factor for increasing the interaction of aggregate interlocking, leading to an augmentation of RCC strength. On the other hand, the dry density of RCC can be changed owing to the compaction conditions, water content, and particle size distribution. A Proctor test and a modified Proctor test were used for determining the optimum water content needed to achieve maximum dry density with different amounts of compaction energy. A Vebe test, on the other hand, was used for checking the level of consistency, which is important for producing a workable mixture. METHODS : To confirm the degree of compaction at various particle sizes, RCC mixtures with different sand/aggregate ratios were evaluated. The Proctor test and modified Proctor test were applied to these mixtures to check the effect of the aggregate gradation and compaction energy on the maximum dry density and optimum water content. During each test, three specimens were produced for all types of water content under each aggregate gradation. A compaction curve and the optimum water content and maximum dry density for each aggregate gradation were then obtained for both tests. The range of water content for the appropriate consistency of each aggregate gradation was determined through a Vebe test. The optimum water content was then evaluated based on this range. RESULTS : The compaction test results show that the modified Proctor test provides a higher maximum dry density and lower optimum water content compared with the standard Proctor test. For the modified Proctor test, two cases of aggregate gradation (s/a = 30% and 70%) had the optimum water contents outside of the appropriate water content range. For the standard Proctor test, on the other hand, none of aggregate gradations provided the optimum water content within the desired range. CONCLUSIONS : The modified Proctor test should be used for an RCC mixture design because it can provide adequacy between maximum dry density and consistency. Moreover, the compaction roller has become highly developed for higher compaction energy.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.10
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• pp.136-142
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• 2010

In this paper, we changed $SF_6$ insulation gases used already in the GIB(Gas Insulated Bus, gas insulated busbar) of switching appliances of power grid 170[kV] GIS(Gas Insulated Switchgear, Gas Insulated Switchgear) with green insulation dry air gases and studied dielectric breakdown voltage characteristics by the AC voltage withstand test. Withstand test AC voltage applied to the standard KEPCO's 170[kV] GIB with dry air insulation and and the equivalent of dry air and $SF_6$ gas were examined. Breakdown voltage of dry air, using an expression of the experiments were calculated and AC Withstand criterion of dry air insulation for the AC voltage test was derived. Using the criterion, dry air gases can be used instead of the $SF_6$ gas was confirmed in the factory acceptance test at 170[kV] GIB.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.111-120
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• 2006

Opening size of 3 types of geotextile were tested using dry and wet sieving methods to evaluate characteristics of test methods and to compare the test results. Judging from test results, dry sieving method is a poor test, having many problems causing many errors but a simple-quick test. Wet sieving method is a very specific test avoiding many of the problems of dry sieving such as electrostatic charges, trapping in the geotextiles and so on. However, one of wet sieving tests, KSK ISO12956, takes long time to complete a test and is too strict to handle loss of granular material. Generally, opening size of a geotextile by wet sieving test is smaller than that of dry sieving test. Especially, opening size by KSF 2126 which is one of wet sieving test but disused at present anymore is similar or smaller than that by KSK ISO12956 method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.804-808
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• 2010

In this paper, we studied the dielectric breakdown voltage characteristics by the AC withstand voltage test on using green insulation dry air instead of $SF_6$ insulation gas used in the GIB (gas insulated bus) of 362 kV GIS (gas insulated switchgear). The AC withstand voltage test applied to the standard KEPCO's 362 kV GIB with dry air insulation, and the equivalence of dielectric breakdown voltage for dry air and $SF_6$ gas were examined, and the empirical formulas of dielectric breakdown voltage for dry air were calculated, and the criterion of AC withstand voltage test for dry air insulation was derived. Using the criterion, dry air can be used instead of $SF_6$ gas for 362 kV GIB in the factory acceptance test was confirmed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3988-3997
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• 2010

Shotcrete was a mortar or concrete that is pneumatically projected at high velocity onto a subject. It has been applied for tunneling, underground big-spaces, slope stabilization. Shotcrete is increasing use in structure repair. The dry-mix shotcrete require a smaller equipment, easy maintenance, possible of very-earlystrength materials than wet-mix shotcrete, which make this process attractive and economic for structural repairs. It is common practice core compressive strength to the dry-mix shotcrete quality control. This test is very difficult estimating eraly-strength of Very-Early-Strength Dry-Mix Shotcrete. The purpose of this research was to analyze the correlation of test results among cube test, core test, pullout test and maturity. The correlationship analysis of test results among cube test, core test, pullout test and maturity showed more than 90%.

• Journal of the Korean Geotechnical Society
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• v.23 no.2
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• pp.19-27
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• 2007

Dry and wet test methods established by Korean industrial standards to estimate opening size of 3 types of geotextile which are widely used for filter of plastic drain board in Korea are performed to evaluate characteristics of the test methods and to compare the test results. Judging from test results, dry method is a relatively poor test, having lots of problems causing many errors but a simple-quick test. Wet method is a very specific test avoiding many of the problems of dry method such as electrostatic charges, trapping in the geotextiles and so on. However, one of wet test methods, KS K ISO 12956, takes long time to complete a test and is too strict to handle loss of granular material. Generally, opening size of a geotextile by wet test method is smaller than that of dry test method. Especially, opening size by KS F 2126 which is called hydrodynamic method but at present is not used anymore is similar to or smaller than that by KS K ISO 12956 method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.521-522
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• 2010

• Structural Engineering and Mechanics
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• v.65 no.2
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• pp.203-211
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• 2018

This paper introduces the development process of NCC(New Concrete Cutting) system and analyzes first verification test. Based on the first verification test results, some problems of NCC system have been newly modified. We carry out the second verification test. We tried to verify cutting performance and dust control efficiency of NCC system through the cutting test of concrete bridge piers. In particular, this verification test strives to solve the problem of concrete dust, which is the biggest problem of dry cutting method. The remaining dust problems in cutting section tried to solve through this verification test. This verification test of the NCC system shows that the dust problem of dry cutting method is closely controlled and solved. In conclusion, the proposed NCC method is superior to the dry cutting method in all aspects, including cutting performance, dust vacuum efficiency and cooling effect. The proposed NCC system is believed to be able to provide eco-friendly cutting technology to various industries, such as the removal of the SOC structures and the dismantling of nuclear plants, which have recently become a hot issue in the field of concrete cutting.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.2
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• pp.161-164
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• 2001

The purpose of our study was stability of tear film for Korean. In the 1970s, the major problem for the contact lens practitioner was the management of contact lens parameters. In the 1980s, oxygen permeability was the main problem in contact lens practice: now it is dry eyes. To appropriately fit the patient with contact lenses it is imperative to know in advance if the patient has a marginal dry eye. Based on the initial diagnosis appropriate care can be taken to minimize problems with the result that the patient can successfully wear contact lenses. A well known test for dry eyes is Schirmer test which has shown to be useful for diagnosing Sjogren syndrome. Biomicroscopy can often unmask numerous problems. The classical test for marginal dry eye is measuring the tear break up time(TBUT). A dry eye problem with contact lenses is often caused by the lid. If an incomplete blink is responsible for the dry eye it is possible to change the situation by blinking exercises. The result of these test, mean value of age was 22.8, mean value of blink rate was 19 times/min, mean value of Schirmer test was 25 mm/5 min, mean value of TBUT was 7.1 sec.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.357-364
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• 1999

The purpose of this study is to analysis the grain distribution and compaction characteristics of structural backfill with reclaimed soil. Five(5) reclaimed soil samples which passed #200 sieve have been used in the test. The study showed that the maximum dry density and the bearing value rate turned out to be becoming smaller when the more the quantity passed #200 sieve, the smaller the soil grain. The maximum dry density value calculated from the compaction md relative density test showed wet method > compaction method > dry method. The correlation coefficient between Rc and Dr based on the grain distribution and the compaction characteristics showed that the maximum dry density value by the wet method is little higher than the compaction method and dry method.