• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.122-129
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• 1998

A field experiment was performed to analyze the properties of SFRS(steel fiber reinforced shotcrete) against WMRS(wire mesh reinforced shotcrete) with some experimental parameters. The parameters were reinforcing methods(steel fiber and wire mesh), steel fiber contents(0.5%, 0.75%, and 1.0%), silica fume contents(0.0% and 10.0%), spraying thicknesses of layer(10㎝, 8㎝, and 6㎝), and spraying parts(side wall, shoulder, and crown). According to the analyzed results, the mechanical properties of SFRS such as compressive strength, flexural strength, and load-carrying capacity after cracks were improved. And the economic evaluation was also performed on the basis of the required thickness of the layer and other researcher's results for rebound ratios. From the results of this tests, it is found that the traditional WMRS may be substituted by the SFRS in the viewpoint of the economic evaluation as well as the mechanical properties. In additions, the silica fume, even if it is very expensive, can significantly improve the mechanical properties of the shotcrete regardless of mixing with or without the steel fiber.

• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.152-157
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• 2018

The degradation and damage of the components for ballasted track could be caused a serious problem for railway safety. Therefore, the integrity evaluation of ballasted track condition is important to ensure and predict that the track safety and track maintenance. Various track components such as rail pad, ballast, sleeper, and rail that are widely used in Republic of Korea and represent a range of physical properties have been selected for this research. In this study, the experimental modal analysis was performed by the non-destructive testing. Modal test results were obtained from the field test and used to assess the condition of the track components. From the field test, the system of ballasted track was found to be simplified as a two-degree-of-freedom(2DOF) dynamic system. The condition of track component was found to directly affect the dynamic response of ballasted tracks. As the results, the dynamic properties of the track component was depend on the track condition and was distributed more roughly and over a wider range than its initial design values. Further, the methodology presented in this study is possible to determine experimentally the fundamental track parameters which are required in the numerical analysis, and also are useful for the safety assessment of track condition.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.20 no.2
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• pp.119-130
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• 2010

Pulmonary toxicity of talc containing tremolite asbestos (TCT) has been studied in term sequential in Sprague-Dawely rats. UICC chrysotile(average diameter 0.03${\mu}m$, average length 2.93${\mu}m$) was applied as the positive control. TCT was analyzed for its physicochemical properties by transmission electron microscope equipped with energy dispersive X-ray spectrometer(TEM-EDS). The effects of 2mg TCT(talc average diameter 9.7${\pm}$8.4${\mu}m$; tremolite average diameter 1.6${\pm}$1.6${\mu}m$, average length 10.8${\pm}$7.0${\mu}m$) on pathological changes were evaluated after 1, 8 weeks instilled into rat lungs. 2mg Chrysotile continuously affected lung pathological changes. Inflammation and granuloma response broke out from 1 week after instilled with chrysotile and the pathological examination further showed increased legions of lung after 8 weeks. But TCT did not showed lung pathological changes. The biopersistence of TCT and chrysotile was evaluated by TEM- EDS. Whereas chrysotile continuously have retained to 8 weeks instilled into rat lungs, talc of TCT showed statistically significant decrease of diameter from 1 weeks and statistically significant change in Si atomic % compositions at 8 weeks instilled into rat lungs. Physicochemical properties of tremolite of TCT were not affected until 8 weeks instilled into rat lungs. This study showed that the durability of TCT in the lungs is much weaker than chrysotile.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.920-924
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• 2012

This study was performed to estimate total contents of arsenic (As) by stepwise multiple-regression analysis using chemical properties and extractable contents of metal in paddy soil adjacent to abandoned mines. The soil was collected from paddies near abandoned mines. Soil pH, electrical conductively (EC), organic mater (OM), available phosphorus ($P_2O_5$), and exchangeable cations (Ca, K, Mg, Na) were measured. Total contents of As and extractable contents of metals were analyzed by ICP-OES. From stepwise analysis, it was showed that the contents of extractable As, available phosphorus, extractable Cu, exchangeable K, exchangeable Na, and organic mater significantly influenced the total contents of As in soil (p<0.001). The multiple linear regression models have been established as Log (Total-As) = 0.741 + 0.716 Log (extractable-As) - 0.734 Log (avail-$P_2O_5$) + 0.334 Log (extractable-Cu) + 0.186 Log (exchangeable-K) - 0.593 Log (exchangeable-Na) + 0.558 Log (OM). The estimated value in total contents of As was significantly correlated with the measured value in soil ($R^2$=0.84196, p<0.0001). This predictive model for estimating total As contents in paddy soil will be properly applied to the numerous datasets which were surveyed with extractable heavy metal contents based on Soil Environmental Conservation Act before 2010.

• Journal of Dairy Science and Biotechnology
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• v.38 no.3
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• pp.146-153
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• 2020

Recently, hyaluronic acid, which is the most popular among various biomaterials, has been used in osteoarthritis treatment, eye surgery, and wound healing. This study was carried out to determine the physicochemical and organoleptic properties of kefir containing various concentrations of hyaluronic acid. The pH value of hyaluronic-acid-containing kefir ranged from 3.58 to 3.46. Moreover, for hyaluronic-acid-containing kefir, the score of taste ranged from 4.75 to 4.0, the flavor ranged from 4.0 to 3.38, the color ranged from 4.38 to 4.0, the texture ranged from 4.38 to 3.75, and the overall acceptability ranged from 4.59 to 3.72. Overall, the organoleptic properties of hyaluronic-acid-containing kefir were better than those of the control. Because this is the first study involving hyaluronic acid and kefir, the results are valuable. The addition of hyaluronic acid did not significantly affect the physicochemical and organoleptic properties of kefir. Therefore, the commercial availability of various hyaluronic-acid-added dairy food products must be investigated.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.2
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• pp.238-245
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• 2014

Objectives: It was known that workers in synthetic leather company are mainly co-exposed to dimethylformamide(DMF) with methyl ethyl ketone(MEK) or toluene(TOL) instead of a single dimethylformamide. This study was examined to the physico-chemical properties in single DMF and binary mixture DMF with MEK or TOL. Materials: Physico-chemical properties were measured by Korean and American Standard Test Methods. Results: Boiling point, specific gravity and flash point in single DMF were significantly higher than binary mixture DMF with MEK or TOL and such difference was dependent on the mixing ratio of MEK and TOL, and low explosion limit in binary mixture DMF with TOL was only significantly lower than single DMF. However, Reid vapor pressure had significantly higher in binary mixture DMF with MEK or TOL compared with single DMF. Conclusions: Our results demonstrate that the binary mixture DMF with MEK or TOL synergistically increases volatilization of DMF. It was concluded that the interaction between DMF and MEK and/or TOL might play a key role in the volatilization process of DMF under environmental conditions of workplace.

• Geomechanics and Engineering
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• v.22 no.5
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• pp.385-396
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• 2020

A uniaxial compression test was performed to analyse the mechanical properties and macroscale and mesoscale failure mechanisms of sandstone with pyrite concretions. The effect of the pyrite concretions on the evolution of macroscale cracks in the sandstone was further investigated through numerical simulations with Particle Flow Code in 2D (PFC2D). The results revealed that pyrite concretions substantially influence the mechanical properties and macroscale and mesoscale failure characteristics of sandstone. During the initial loading stage, significant stress concentrations occurred around the edges of the pyrite concretion accompanied by the preferential generation of cracks. Meanwhile, the events and cumulative energy counts of the acoustic emission (AE) signal increased rapidly because of friction sliding between the concretion and sandstone matrix. As the axial stress increased, the degree of the stress concentration remained relatively unchanged around the edges of the concretions. The cracks continued growing rapidly around the edges of the concretions and gradually expanded toward the centre of the sample. During this stage, the AE events and cumulative energy counts increased quite slowly. As the axial stress approached the peak strength of the sandstone, the cracks that developed around the edges of the concretion started to merge with cracks that propagated at the top-left and bottom-right corners of the sample. This crack evolution ultimately resulted in the shear failure of the sandstone sample around the edges of the pyrite concretions.

• Journal of the Korean Society of Safety
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• v.31 no.5
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• pp.42-48
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• 2016

The usage of the correct combustion properties of the treated substance for the safety of the process is critical. For the safe handling of n-nonane being used in various ways in the chemical industry, the flash point and the autoignition temperature(AIT) of n-nonane was experimented. And, the explosion limit of n-nonane was calculated by using the flash point obtained in the experiment. The flash points of n-nonane by using the Setaflash and Pensky-Martens closed-cup testers measured $31^{\circ}C$ and $34^{\circ}C$, respectively. The flash points of n-nonane by using the Tag and Cleveland open cup testers are measured $37^{\circ}C$ and $42^{\circ}C$. The AIT of n-nonane by ASTM 659E tester was measured as $210^{\circ}C$. The lower explosion limit by the measured flash point $31^{\circ}C$ was calculated as 0.87 vol%. And the upper explosion limit by the measured upper flash point $53^{\circ}C$ was calculated as 2.78 vol%. It was possible to predict lower explosion limit by using the experimental flash point or flash point in the literature.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.649-654
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• 2005

Shallow slope failures in residual soil during periods of prolonged infiltration are common over the world. One of the key factors that dominate slope stability is hydrological response associated with infiltration. Hence, the soil-water profile during rainfall infiltration into unsaturated soil must me examined to evaluate slope stability. However, the hydraulic response of unsaturated soil is complicated by inherent uncertainties of the soil hydraulic properties. This study presents a methodology for assessing the effects of parameter uncertainty of hydraulic properties on the response of a analytical infiltration model using first-order reliability method. The unsaturated soil properties are considered as uncertain variables with means, standard deviations, and marginal probability distributions. Sensitivities of the probabilistic outcome to the basic uncertainties in the input random variables are provided through importance factors.

• Journal of Dairy Science and Biotechnology
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• v.38 no.2
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• pp.59-69
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• 2020

This study was conducted to evaluate the chemical and organoleptic properties of some dairy products supplemented with different concentrations of propolis (0%, 0.5%, 1.0%, 1.5%, and 2.0%). There was no significant difference between pH values of the treated and control groups. All samples were tested using 20 evaluators divided in five categories. Compared to the control, the best organoleptic test results were obtained for market milk, yoghurt, and Kefir supplemented with 0.5% propolis. Statistical difference was observed in the taste, flavor, color, texture, and overall acceptability of market milk, yoghurt, and Kefir between the treated and control groups (p<0.05). However, as propolis has a strong aromatic flavor, it should be supplemented in small amounts, so as not to affect the organoleptic properties of the product. In conclusion, this study provides useful information for the development of functional dairy products using propolis.