• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.315-320
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• 2002

The effects of slag content and polymer-binder ratio on the strength properties of the polymer-modified concretes using ground granulated blast-furnace slag and a styrene-butadiene rubber (SBR) latex are examined. As a result, the compressive, tensile and flexural strengths of the SBR-modified concretes using slag increase with increasing polymer-binder ratio and slag content, and maximized at a slag content of 40 ％. In particular, the SBR-modified concretes with a slag content of 40 ％ provide approximately two times higher tensile and flexural strengths than unmodified concretes. Such high strength development is attributed to the high tensile strength of SBR polymer and the improved bond between cement hydrates and aggregates because of the addition of SBR latex.

• KSBB Journal
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• v.8 no.4
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• pp.320-327
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• 1993

Latex microspheres of styrene/acryl copolymer with acrylamide functional group were used for the stable covalent immobilization of an enzyme applicable for enzymatic synthesis of glycoside. The latex microspheres were coated with polyethyleneimine to establish structural and functional properties relevant to the covalent Immobilization with a high retention of activity. Polythyleneimine-coated microspheres satisfactorily immobilized the invertase for methyl fructoside synthesis, and model reaction were formed into alginate-enclosed microspheres biocatalyst. Using the alginate-enclosed microspheres biocatalyst, the yield of model glycoside was obtained as high as 52.2% at concentration of aqueous 30%(v/v) methanol and 0.291mo1/1 sucrose solution with 2U/ml of activity. The present study showed that the latex microspheres were successfully applied to enzymatic synthesis of glycoside.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.11-12
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• 2014

In this study, fundamental properties of concrete mixed with fiber has been analysed. Compressive strength, tensile strength and plastic shrinkage has been tested to conduct the optimum addition ratio of fiber. Effect to control press concrete's cracking has been tested. The following results could be made as the conclusion. For the flowability, slump decreased about 41-79% when all types of fiber used in the concrete. When the addition ratio of fiber is 1.2%, the slump of concrete decreased about 45%. For the strength properties. all the specimens with different addition ratio of fiber shown higher compressive strength comparing with Plain. Comparing with Plain, cracking decreased when the fiber added. Especially, when NY fiber used in the concrete, the plastic shrinkage did not occurred. In addition, Latex modified concrete(LMC) has improved superior physical and chemical properties. The properties of latex, combined with the low water-cement ratio, produce a concrete that has improved flexural, tensile, and bond strength, lower modulus of elasticity, increased freeze-thaw resistance, and reduced permeability compared to conventional concrete of similar mix design.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.171-182
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• 1998

Vibration-controlled concrete has been developed by using various concrete mixtures, such as latex, rubber powders, plastic resins and polystyrene(styrofoam). As part of the recycling research of obsolete aged tires and plastic materials, various vibration-reducing mixtures are used for 10 concrete panels having above 200 kg/cm$^2$ in uniaxial compressive strength. Plywood box with sand uniformly saturated by the raining device has been used for the analysis of the impact wave, of which data have been transfered by the FFT technique to comparatively investigate damping ratios of 10 concrete panels.According to wave propagation analysis on vibration-controlled concrete for this research, it can be concluded that Latex concrete has relatively larger damping ratios than those for noncontrolled normal concrete in a similar compressive strength

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.4
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• pp.185-195
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• 2001

Latex Modified Concrete(LMC) has been widely used for the pavement of highway bridges over the past 35years around the world since it is more resistant to the intrusion of chloride ions, has higher tensile, compressive, and flexural strength, and has greater freeze-thaw resistance. However, in Korea, it has not been introduced to fields due to higher initial construction cost for its overlay compared with that of conventional pavement materials. Due to durable characteristics, it should be noted that the LMC may be more cost-effective than conventional pavements such as asphalt pavement, when life-cycle cost(LCC) concept is considered. The objective of this study is intended to suggest a practical LCC analysis model for pavement projects and to demonstrate relative cost-effectiveness of the LMC overlays in comparison with conventional pavement techniques. It may be stated that the procedure proposed in this study may be utilized for making optimal decision on cost-effective pavement design.

• Korean Journal of Pharmacognosy
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• v.6 no.1
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• pp.43-47
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• 1975

Attempts were made to determine the characteristics of the morphology of Codonopsis lanceolata $T_{RAUT's}$ root. Its saponin and crude powder were examined by foaming and hemolytic tests and by observing transverse sections: 1) The cork-layer was consisted of multiple cells, and some of the cork cells contained monoclinic prism crystals of calcium oxalates. 2) The vascular bundle was formed of radial arrangement by the preminentic bursting pith and the irregular cambium ring with the abnormal growth. 3) The latex vessel and latex of the cortex were brown-gray or yellowish-brown. The latex vessel and sieve tube were consisted of the independent aggregates which had a number of layers. It had much more independent aggregates than Platycodi Radix. 4) The xylem was less than the phloem portion. The thick-walled vessels which had one to five lines ware more distributed than in Platycodi Radix. 5) The inulin distribution on a piece of section which is dipped in alcohol was observed through out the tissues, but starch grain was not found in it. 6) The duration time of foaming reaction of the crude powder in test tubes was shorter than that of Platycodi Radix. Foaming index of the foaming test of five percent decoctions was 3.33, 7) In the hemolytic test which used 10 percent decoction and one percent saponin solution, hemolytic action was very weak.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.5
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• pp.153-160
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• 2019

The purpose of this study was to investigate the mechanical and durability characteristics of latex-modified concrete using ultra rapid hardening cement : four types of mechanical tests including compressive strength, modulus of elasticity, flexural strength and bond strength were performed; and seven types of durability tests including resistance of concrete to chloride ion penetration, freeze-thaw resistance, scaling resistance, coefficient of thermal expansion, cracking tendency, abrasion resistance and drying shrinkage were performed. Required material performance of each test was determined in accordance with the Korea specification for repair of concrete and pavement repairing materials. The test results satisfied the required material performances, and presented a good mechanical and durability characteristics. In particularly, the materials showed early development of compressive strength, flexural strength and bond strength at 3 and 4 hours after curing. SEM photos were also taken to investigate the micro structures of the materials after chloride ion penetration test.

• Journal of the Korean Society of Physical Medicine
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• v.17 no.3
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• pp.11-21
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• 2022

PURPOSE: This study examined the changes in the handgrip strength, dexterity, and hand function according to the presence or absence of gloves and types of gloves. METHODS: Seventy-six adults in their twenties (male: 24, female: 52, mean age 21.04 years) were the subjects of this study. The handgrip strength, dexterity, and hand function were evaluated with bare hands without gloves, poly gloves, and latex gloves. The handgrip strength was measured using a dynamometer, and three pinch strength tests were performed: tip pinch, lateral pinch, and three-jaw pinch. The hand dexterity was evaluated using the Minnesota manual dexterity test, and the hand function was evaluated using the Jabson-Taylor hand function test. RESULTS: There was no difference in the grip strength depending on whether the gloves were worn. The hand grip, dexterity, and hand function showed significant differences according to the type of glove. Regarding the handgrip, dexterity, and hand function, the latex glove had the best function, and the poly glove had the lowest function. CONCLUSION: There was a difference in dexterity among the hand functions but no difference in grip strength according to the type of glove. The results suggest that the use of latex gloves in daily life be recommended.

• Parasites, Hosts and Diseases
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• v.30 no.2
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• pp.83-90
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• 1992

Sensitivity of anti-Texoplasma antibody (IgG) test by enzyme·linked immunosorbent assay (ELISA) was evaluated in comparison with indirect laten agglutination (ILA) using 2,016 paired human samples of serum and cerebrospinal quid (CSF) . The samples were collected from neurologic patients in Korea with mass lesions in central nervous system(CNS) as revealed by imaging diagnosis(CTIMRI). When the sera were screened for anti-Toxoplasma antibody by ILA, 76 cases (3.8%) were positive (1:32 or higher titers). In the pairs samples of CSF, no positive reactions were observed. When ELISA was performed using PBS extract of Percoll purified tachysoites as antigen, cut-off absorbance was determined as 0.40 for serum and 0.27 for CSF tests. The antibody positive rates by ELISA were 7.0% in serum and 5.6% in CSF Of them, 40 cases(2.0%) showed positive reactions in both serum and CSF, The antibody positive rates were higher in groups older than 40 years, The rates were higher in male(4.7% by ILA, 8.3% by ELISA) than in female(2.2% by ILA, 5.0% by ELISA). The rates in CSF showed no such sex difference. ELISA showed twice higher positive rates when serum was tested, and was sensitive enough to detect specific antibodies in CSF. Etiologic relations between positive antibody tests and CNS lesions remained unknown.

• International Journal of Highway Engineering
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• v.3 no.4 s.10
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• pp.117-126
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• 2001

In this research, evaluation of adhesion in tension property of SBR-modified concrete to ordinary portland cement concrete was conducted with uniaxial direct tensile bond test which was proposed by Kuhlmann. A test set-up was fabricated in order to minimize the eccentric force by introducing a joint which might fully rotate. The main experimental variables were cement-latex ratios, surface preparations and moisture levels. The results obtained were as follows: The LMC specimen at 15% latex-cement ratio increased the adhesion in tension by range of 37% compared to that of conventional cement concrete. This might be due to latex film formed between cement paste and aggregate. The effects of surface preparation on bond of latex modified concrete to conventional concrete were significant at the conditions by sand paper and wire brush. A better bond could be achieved by rough surface rather than smooth. The saturated and surface dry (SSD) condition were considered to be the most appropriate moisture level followed by wet, finally by dry. Thus, a proper surface preparation and moisture level are quite necessity in order to obtain better bonding at LMC overlay.