• Journal of the Society of Cosmetic Scientists of Korea
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• v.23 no.3
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• pp.134-146
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• 1997

Consumers have recently preferred to purchase extensive UV intercepting products, which are waterproof and free from side effects on skin. Testing Cytoroxicity in SR method, cell survivial ratio of UV-B interceptors decreased above 0.08W/V%, and so did that of UV-A interceptors above 0.06W/V%. Also, Patch-test of inorganic UV interceptors resulted in no skin irritation even below 10.0 and 11.25. UV interceptors in the sunlight showed yellowish discoloration in 5 to 14 days. In absorption curves, UV-B was most suitable for Octyl methoxycinnamate and UV-A for Butyl methoxy dibenzoylmethane. Fro this reason, Nylonpoly UVA/UVB the material of OMC and BMDM coated with Nylon & polyethylene, was used as the organic UV interceptor. And zinc oxide and titanium dioxide was used as inorganic UV ibterceptors. The appropriate mixture ratio of ZnO and TiO2 was 6 to 4.6% of ZnO, 4% of TiO2 and 5% of Nylonpoly UVA/UVB were all combined with our sunscreen cream. The SPF value of in-vivo applied to a guinea pig was 34.9 and that of in-vivo was 38.5. Cyclomerhicone and dimerthicone were used in water-in-Silicone system. Ceryl diverhicone and sorbitan sesquioleate were used as emulsifiers and MgSO4, 7H2O, Mg-stearate/Mg-Al-stearate copolymer as emulsification stabilizers. In practical application, each SPF duration of O/W type and W/S type containing sunscreen cream of the same content showed that W/S type of sunscreen cream was 5 times as durable as the other. This product is fit for using in swimming, climbing or skiing. This research is to minimize skin trouble used by UV interceptors and to make one with proper softness, skin safety and UV intercepting efficiency.

• Explosives and Blasting
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• v.26 no.2
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• pp.29-37
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• 2008

In general, the size of tunnel cross section in construction site is $50{\sim}200m^2$. But, electric cable tunnel, telecommunication cable tunnel, mine tunnel. Waterproof tunnel have small cross section less than $20m^2$. There are so many problem at small sectional tunnel: restriction of equipment, dead pressure by precompression, loss of efficiency, increase of work time. Especially, explosives remainder by precompression of previous detonation is serious problem. To find its measures of dead pressure (explosives remainder), the following series of progress have been conducted: (1) survey of previous study (2) investigate causes of dead pressure (3) set up of its measures (4) application and appraisal at tunnel site. The measures, change of cut pattern, hole space over 40cm, adjustment of delay time, are proved by experimental results.

• Korean Journal of Ecology and Environment
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• v.47 no.3
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• pp.225-231
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• 2014

Discharge measurement during flood season is very difficult. Microwave water surface current meter (MWSCM) can measures river surface velocities easily without contacting water. This study introduces its improved version, MWSCM for general use. The existing version of MWSCM is for floods so that its applicable period in a year is short. It has been improved to extend its applicability in a year. The range of measurable velocity for MWSCM for general use is extended so it can be applied during normal flows as well as high flows. MWSCM for general use can measure the velocity range of $0.03{\sim}20.0ms^{-1}$, whereas MWSCM for floods can measure the velocity range of $0.5{\sim}10.0ms^{-1}$. To make such innovation of MWSCM for general use, the applied microwave frequency of MWSCM was changed from 10 GHz to 24 GHz. Waveguide slot array antenna has been designed with the new development of the circuit of transmitting and receiving part. Improvement requests on the existing MWSCM for floods - weight lightening, measured velocity stabilization, self-test, low power consumption, and waterproof and dampproof - from the users of it have been reflected for the development of the new version of MWSCM.

• Journal of the Korean GEO-environmental Society
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• v.17 no.12
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• pp.45-54
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• 2016

In this study, the construction method of new underground continuos impervious wall that the bentonite slurry keeps the stability of excavated trench and the mixture of cement and bentonite plays a role as a constituent of impervious wall in the trench. The merit of homogeneity of the method so called as a cement-bentonite slurry wall enables to accurately make an estimation of hydraulic conductivity of the walls compared with that by other general grouting methods and to verify their waterproof efficiency without difficulty at the design stage. The use of cement-bentonite slurry walls for the containment of groundwater flow has also proven a cost-effective impervious wall technology by employing the simple combination of construction equipments and easy and fast construction procedures. The engineering characteristics of cement-bentonite impervious wall obtained by carrying out the laboratory experiments under various conditions. This study reveals the effect of variation of constituent materials and their mixing methods (Water-Cement-Bentonite) on the engineering characteristics of a composition. Also, this study makes some recommendations on the optimum mixing ratio and mixing sequence for the best quality at the site. That is the most important factors to estimate the construction cost and design of the technique. The comparison is lastly made to evaluate the effect of ordinary Portland and blast furnace slag cement as a bonding material on the behavior of impervious walls.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.212-219
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• 2015

This study focuses evaluating the efficiency and performance evaluation of composite type sheet-membrane waterproofing method that utilizes a separation behavior inducement system designed to resolve the chronic problems of disintegration and damage of overlap areas of waterproofing layers. As the result of the test, the tensile strength value was at 13.8N/mm and elongation rate at 587% for the separation behavior inducement type specimen, and the compared specimens had 14.2N/mm for tensile strength and 335% for elongation rate. For the separation behavior adhesion method specimen, when tensile stress or displacement occurred, the Zero-Span tension occurrence did not follow, which resulted in that the bottom sheet layer and the top membrane layer did not simultaneously becoming damaged. When undergoing the top and bottom layers were separated through separation behavior due to lack of flexibility, the bottom layer began to damage at the primary stage, and with the allowed boundary the upper membrane layer began to display flexibility and showed continuous displaced resulting in secondary phase damaging.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.465-481
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• 2022

Rock grouting is important to improve the waterproof efficiency and mechanical strength of rock medium with joint for utilizing the underground rock space such as tunnel. The grouting materials typically has been used the cement materials, which represent Bingham fluid model. This model can express the relationship of viscosity and yield strength. In addition, it is dependent with elapsed time. The grouting injection performance can be deteriorated with an increase of viscosity and yield strength in the grouting process if the time dependence is ignored. Therefore, in this study, the characteristics of viscosity and yield strength were investigated according to water-cement ratio and time dependence in the laboratory test. Numerical simulation was carried out to investigate the grouting performance according to the time dependence of characteristics in terms of the viscosity model. Given the results, the grouting injected distance and cumulative grout volume were significantly decreased when the time dependence of grouting material was considered. This study, considering the characteristics according to the time dependence of viscosity and yield strength, will be meaningful to the design of grouting injection in field applications.