• 한국안전학회지
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• 제33권6호
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• pp.22-27
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• 2018

Fire fighters are exposed to the risk of many accidents during fire suppression, especially near the high voltage circuit. In order to prevent and analyze the electric shock accidents, measurement of water resistance is crucial. However, this has been one of the overlooked research areas and it has been very difficult to measure the mixed up resistance components separately. In this paper, we measured a total resistance of apparatus and regarded it as a serial resistance of contact resistance and length dependant resistance. Measuring the resistance by varying the length of water stream, the variable resistance and fixed contact resistance appear, which are used to calculate the both components of resistances. In addition, the resistance of fire hose can be calculated from the parallel circuit which is formed by grounding the fire hose with the resistance of water stream. Results show that we can successfully measure the resistance per unit length of water stream and fire hose, thereby proving that this method is a facile way to measure water and fire hose resistance. However, many experiments are still required to obtain the precise contact resistance of ground under various condition and the resistance between the human body and fire hose.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.307-312
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• 1997

The sea water resistance of cement and concrete must be compared when it used for construction in the ocean. The sea water resistance of the concrete specimens using three types of cements such as ordinary Portland cement, sulfate resistance Portland cement, blastfurnace slag cement were studied. In this study, an accelerated test for access sea water resistance by subjecting the concrete specimens to repeated cycles of concentrated sea water immersion and hot wind drying was employed. This study proved that sulfate resistance Portland cement had higher resistance for sea water.

• The International Journal of Costume Culture
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• 제4권3호
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• pp.241-248
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• 2001

Re water resistance of shell fabrics intended for we in outdoor apparel was measured using three different standard test methods, ASTM D 751, hydrostatic resistance, procedure A(Mullen test -- with and without a fabric support) and Procedure B (Hydrostatic head test). A database of information on their water resistance performance was created. The data collected with different methods were correlated and the advantages and disadvantages of each method were compared. The Mullen test with a support appears to give higher and more favorable water resistance values on shell fabrics preventing fabric rupture during the test. The hydrostatic head test gave lower hydrostatic pressure values than those measured on the two Mullen tests. The Mullen test is recommended for testing the water resistance of fabrics that high a relatively high water resistance because the Mullen tester applies a wide range of pressure. The hydrostatic head test is recommended for testing the fabrics that have relatively low water resistance. The area of the fabric sample that is in contact with the water is smaller in the Mullen test, so higher pressure levels can be reached and more samples should probably be tested to get a representative value for each fabric types. Furthermore, the hydrostatic head test was deemed more repeatable than the Mullen tests in his study.

• 한국응용과학기술학회지
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• 제22권3호
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• pp.289-297
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• 2005

In order to improve resistant properties of water-borne acrylic pressure sensitive adhesives(PSAs) for automobiles, this study was carried out. Removable PSAs for automobiles were synthesized by emulsion polymerization of monomers, n-butyl acrylate(BA), n-butyl methacrylate(BMA), acrylonitrile(AN), acrylic acid(AA) and 2-hydroxyethyl methacrylate(2-HEMA), and AA and 2-HEMA could act as functional monomers for crosslink. Emulsion polymerization was carried out in a semi-batch type reactor. Water resistance, heat resistance, acid resistance, alkali resistance and smoke resistance were examined. As a result, water resistance increased with the amount of BMA, however, the effect of BMA content on the water resistance was insignificant at a range of over 14 wt%. The water resistance also increased with the amount of functional monomers, AA and 2-HEMA. The prepared PSAs satisfied all the standard for automobiles except heat resistance. However, the heat resistance comes nearly up to the standard. Also, acid resistance, alkali resistance and smoke resistance of the prepared PSAs satisfied with the standard.

• 대한가정학회지
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• 제20권3호
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• pp.19-24
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• 1982

This study was carried out to investigate the relationship between the water resistance and the air permeability. The results are as follows; 1. In case of the water proofing fabrics, We cannot find that there is any relationship between the water resistance and the air permeability according to the kinds of finishing, while in case of the water repellent finished fabries, we can find that there is a correlationship between them, especially the hydrostatic pressure and the air permeability are found to have negative correlation. 2. In case of the water proofing fabrics, the relationship between the water resistance and the air permeability is not affected by the thickness of the fabrics. On the other hand, in case of the water repellent finished fabrics, the relationship between them is affected by the thickness of the fabrics. Especially, the relationship between the hydrostatic pressure and the air permeability as well as the relationship between the water repellency and the air permeability is effect much by the thickness of the fabrics, too. 3. In case of the water proofing fabrics, the relationship between the water resistance and the air permeability is not affected by fabric count. On the otherhand, in case of the water repellent finished fabrics, the relationship between them is affected by the fabric count. Especially, the relationship between hydrostatic pressure and the air permeability, and the relationship between the water proof and the air permeability are affected much by fabric count.

• 대한조선학회논문집
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• 제41권2호
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• pp.1-11
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• 2004

In this paper, the resistance characteristics of high-speed ship are studied in the region of shallow water condition. For the purpose of this research, model tests in a ship model basin are carried out with an equipment for the satisfaction of shallow water condition, and the computions of wave resistance characteristics and the flow simulations around a ship hull are performed by Michell's thin ship theory and a finite difference method based on MAC scheme, respectively. The calculation results for the resistance and flow characteristics of a ship hull are compared with those from the model tests in deep and shallow water conditions. From the comparison results, it is known that the variation of wave pattern around a ship hull caused by shallow water condition has the most influence to the resistance characteristics of a high-speed ship advancing on shallow water.

• 한국조경학회지
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• 제35권3호
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• pp.105-113
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• 2007

This study was conducted to analyze the effects of environmental factors such as soil moisture, light intensity, temperature and humidity on changes in cambial electrical resistance. To improve data quality, cambial electrical resistance was continuously measured at fixed points by using a data logger isolated from alternating current. The relationship between environmental factors and changes in cambial electrical resistance was also analyzed. The results are as follows: 1. Cambial electrical resistance is highly correlated to the temperature of the measured area(r=-0.934). Therefore, temperature compensation is needed to analyze the effects of other environmental factors on cambial electrical resistance changes. 2. If temperature is compensated for, the change of cambial electrical resistance is highly correlated to water vapor pressure(r=-0.836). 3. If temperature and humidity are compensated for, the change of cambial electrical resistance is highly correlated to intensity of light(r=-0.738). 4. Diurnal deviation of soil water potential is not more significantly related than the change of cambial electrical resistance. However, in the long-term, soil water potential and cambial electrical resistance are highly correlated(r=-0.831). This indicates that soil moisture significantly influences the long-term change of cambial electrical resistance.

• Korea Journal of Cosmetic Science
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• 제2권1호
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• pp.21-31
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• 2020

The aim of this study is to develop a sunscreen stick formulation technology with excellent water resistance and washability. Consumers' needs for sunscreen products are diversifying. Water resistance and ease of washing are both important factors in sunscreen products. However, it is difficult to develop a sunscreen formulation that satisfies these two factors at the same time, because these two elements are in conflict. Fatty acid has a hydrophobic property against the water with low or neutral pH, but when it contacts with soapy water which has high pH, saponification occurs and the fatty acids become surfactants and can be dispersed in the water. Using the reaction characteristics of fatty acids, we can make sunscreen that is highly resistant to water or sweat, but is only selectively removed from soapy water. We found that the sunscreen stick containing fatty acids had better water resistance and washability than the sunscreen sticks without fatty acid. The sunscreen stick containing fatty acids showed a tendency to improve water resistance by scattering ultraviolet rays of long wavelength area by forming insoluble precipitation with divalent ions in tap water after immersion. In addition, an increase in the fatty acid content tended to also increase the ease of cleaning the sunscreen stick. Solid fatty acid was advantageous in improving water resistance than liquid fatty acid, but there was no difference between solid fatty acids and liquid fatty acid in washability. When it comes to stability, the sunscreen stick using liquid fatty acids maintained a high hardness and melting point, and showed no sweating. Based on this study, it is possible to develop an easy washable sunscreen stick formulation technology that has excellent water resistance but is selectively removed only in soapy water.

• 한국안전학회지
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• 제5권3호
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• pp.3-7
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• 1990

This study is conducted to experiment on the performance test for 20 types of Filter-integrated Half-masks which could not only protect workers exposed to dusty environment, but also improve workability. Results and conclusions are as follows ： 1) Respirators that removal efficiency of aerosols is 95 percent or more are 11 kinds(55%), and those who are 99.9 percent or more are 4 kinds(20%). Respirators that inhalation resistance is 4 mm in water or less are 13 kinds(65%), and those who are 6 mm in water or less are 17 kinds(85%). Respirators that efficiency of cumulative inhalation resistance is 100 percent or less are 11 kinds(55%) . 2) Respirators that resistance of moisture inhalation is 6 mm in water or less are 11 kinds(55%). and those who are 10 mm in water or less are 13 kinds(65cio), Respira'tors that ratio of removal efficiency for aerosols between dry and wet conditions is 95 percent or more are 9 kinds(45%). 3) Respirators which are not only 95 percent or more for removal efficiency of aersosls and 6 mm in water or less for inhalation resistance, but also 200 percent or less for efficiency of cumulative inhalation resistance, are 8 kinds(40％). Respirators which are not only 99.9 percent or more for removal efficiency and 6 mm in water or less for inhalation resistance, but also 100 percent or less for efficiency of cumulative inhalation resistance, are 3 kinds(15%). Respirators which are not only 95 percent or more for removal efficiency of aerosols and 6 mm in water or less for inhalation resistance, but also 200 percent or less for efficiency of cumulative inhalation resistance and 10 mm in water or less for resistance of moisture inhalation, are 6 kinds(30％) . 4) As standard rrlodel of artificial human head which would be perhaps different from the true one Is used to experiment fitness test, leakage rate is shown to be more or less high. However, artificial human head shall be accurately examined and follow-up studt. would be conducted in the future.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.867-875
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• 2014

Planing crafts were specifically designed to achieve relatively high speeds on the water. When a planing craft is running at high speed, dynamic pressure on the bottom makes the boat rise on the surface of the water. This reduces the area of the sinking surface of the boat to increase air resistance. Air resistance means the resistance that occurs when the hull and deck house over the surface of the water come in contact with the air current. In this paper, we carried out a CFD numerical analysis to find optimal deck houses that decreased air-resistance on the water when planing crafts are running at high speed. We finally developed the deck house shape of high-speed planing crafts that optimally decreased air resistance.