• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.63-69
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• 2012

Recently, the cement industries brought very severe environment problems such as resource depletion and global warming with massive carbon dioxide during its production. The number of cases using industrial by-products such as the ground granulated blast furnace slag (GGBFS) in concrete mixtures is increasing to resolve the environmental issue. GGBFS is mainly used in the range between 20 to 50% to replace cement, but nowadays lots of researches are carried out to develop the alkali-activated slag (AAS) concrete with no cement. In this study, the early age properties of alkali activated slag (AAS) mortar are investigated to obtain the fundamental data for AAS concrete application to structural members. The experimental variables were the water-binder ratios of 0.3, 0.4, and 0.5 and NaOH as the alkali activator of 4%, 8%, and 12% by the mass of GGBFS, and compressive strength, flow, setting time, and ultrasonic pulse velocity of AAS mortars were measured and analyzed. It is found from the test results that as the normal concrete the lower W/B, the higher compressive strength. However, superplasticizer has to be used for producing high strength AAS concrete because the workability of AAS mortar are significantly lowered.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.688-696
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• 1999

Changes in quality during frozen storage of meat with thermal equalized freezing and various freezing methods were investigated. When beef were frozen at freezing rate of $0.39{\sim}0.66\;cm/h$, average diameter of ice crystal were about $30{\sim}50\;{\mu}m$ and showed broken tissues or irregular cracks. At freezing velocity of $1.14{\sim}2.26\;cm/h$, ice crystals of about $10{\sim}30\;{\mu}m$ was formed mainly inside or between fiber and slight destruction of tissues was occurred. The average diameter (D) of the ice crystals were related to the characteristic freezing time $(t_c)$ by the equation: $D({\mu}m)=4.089+26.88logt_c\;(r^2=0.913)$. Beef with still-air freezing showed higher drip loss than methods of immersion and thermal equalized freezing. Also, drip loss of pork was relatively lower than beef and showed highest value to 7.39% during storage on 40 days at air-blast freezing method. No apparent change of pH during storage of frozen beef and pork by freezing methods were detected. However, least changes for sample with thermal equalized freezing was found compare to sample with still-air and air blast freezing in VBN and TBA value. The fluctuation of frozen storage temperature did not cause noticeable changes on pH and water content. However, drip loss, VBN and TBA values were increased slowly as frequency of fluctuation increased.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.3
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• pp.147-154
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• 2014

In the context of an increasing need for safety in concrete structures under blast and impact loading condition, the behavior of concrete under high strain rate condition has been an important issue. Since concrete subjected to impact loading associated with high strain rate shows quite different material behavior from that in the static state, several material models are proposed and used to describe the high strain rate behavior under blast and impact loading. In the process of modelling high strain rate conditions with these material models, mesh dependency in the used finite element(FE) is the key problem because simulation results under high strain-rate condition are quite sensitive to applied FE mesh size. This paper introduces an criterion which can minimize the mesh-dependency of simulation results on the basis of the fracture energy concept, and HJC(Holmquist Johnson Cook) model is examined to trace sensitivity to the used FE mesh size. To coincide with the purpose of the perforation simulation with a concrete plate under a projectile(bullet), the residual velocities of projectile after perforation are compared. The analytical results show that the variation of residual velocity with the used FE mesh size is quite reduced and accuracy of simulation results are improved by applying a unique failure strain value determined according to the proposed criterion.

• Explosives and Blasting
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• v.9 no.1
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• pp.3-13
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• 1991

The cautious blasting works had been used with emulsion explosion electric M/S delay caps. Drill depth was from 3m to 6m with Crawler Drill ${\phi}70mm$ on the calcalious sand stone (soft -modelate -semi hard Rock). The total numbers of test blast were 88. Scale distance were induced 15.52-60.32. It was applied to propagation Law in blasting vibration as follows. Propagtion Law in Blasting Vibration $V=K(\frac{D}{W^b})^n$ were V : Peak partical velocity(cm/sec) D : Distance between explosion and recording sites(m) W : Maximum charge per delay-period of eight milliseconds or more (kg) K : Ground transmission constant, empirically determind on the Rocks, Explosive and drilling pattern ets. b : Charge exponents n : Reduced exponents where the quantity $\frac{D}{W^b}$ is known as the scale distance. Above equation is worked by the U.S Bureau of Mines to determine peak particle velocity. The propagation Law can be catagorized in three groups. Cubic root Scaling charge per delay Square root Scaling of charge per delay Site-specific Scaling of charge Per delay Plots of peak particle velocity versus distoance were made on log-log coordinates. The data are grouped by test and P.P.V. The linear grouping of the data permits their representation by an equation of the form ; $V=K(\frac{D}{W^{\frac{1}{3}})^{-n}$ The value of K(41 or 124) and n(1.41 or 1.66) were determined for each set of data by the method of least squores. Statistical tests showed that a common slope, n, could be used for all data of a given components. Charge and reduction exponents carried out by multiple regressional analysis. It's divided into under loom over loom distance because the frequency is verified by the distance from blast site. Empirical equation of cautious blasting vibration is as follows. Over 30m ------- under l00m ${\cdots\cdots\cdots}{\;}41(D/sqrt[2]{W})^{-1.41}{\;}{\cdots\cdots\cdots\cdots\cdots}{\;}A$ Over 100m ${\cdots\cdots\cdots\cdots\cdots}{\;}121(D/sqrt[3]{W})^{-1.66}{\;}{\cdots\cdots\cdots\cdots\cdots}{\;}B$ where ; V is peak particle velocity In cm / sec D is distance in m and W, maximLlm charge weight per day in kg K value on the above equation has to be more specified for further understaring about the effect of explosives, Rock strength. And Drilling pattern on the vibration levels, it is necessary to carry out more tests.

• Explosives and Blasting
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• v.17 no.2
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• pp.36-44
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• 1999

A study was made on the design of the prediction model concerning blasting vibration in a constraction site, Namgu, Daegu City. The geology in this area consists of hornfels of shale and mud underlain by quartize, of which the main strike of the geological structure is NW direction. Measurements were carried out on the top of the wall concrete water storage tank, which is burried in the ground earth. The attenuation due to the vertical wall of the concrete structure may be experted because of spherical divergency at the bottom corner of the wall by the Huygens principle. For design of blasting prediction model, thus among scaled distance(SD) may be preferable to use in the regression model, since they represents most likely the average ground condition. Judging from the regression results, the cube root method may be more suitable for this area. The SD values for the maximum allowable vibration velocity of 0.5 cm/s, in this area are 22.5, 28.0 and 30.6 for the significance level of 50%, 95% and 99%, respectively.

• Explosives and Blasting
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• v.30 no.1
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• pp.9-16
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• 2012

With the deterioration and functional loss of structures, there is an increasing demand for demolition and various demolition technologies have been developed. In case of a large-scale concrete foundation, application of some mechanical demolition techniques is limited because of the structural characteristics, and explosive demolition or explosive demolition combined with mechanical demolition is applied recently due to the effect to the surrounding environment by the ground vibration. In this study, we compared peak particle velocity of ground vibration depending on average fragment size in case of explosive demolition design for large-scale concrete foundation using the relation among specific charge, charge constant and transmitting medium constant as well as the relation between average concrete fragment size and specific charge.

• Bulletin of the Korean Space Science Society
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• 2006.10a
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• pp.177-180
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• 2006

We observed $2.1218{\mu}m$ $H_2$ 1-0 S(1) emission from H II region A, which is located just next to Sgr A East and one of the nearest star forming regions to the Gatactic center. Cooled Grating Spectrometer 4 (CGS4) at the 3.8 m United Kingdom Infrared Telescope (UKIRT) was used with aa echelle grating at a velocity resolution of ${\sim}$ 18km s^{-1}$ and an angular resolution of ${\sim}$ 2 arcsec. Comparing the distributions and kinematics of the observed $H_2$ emission with radio continuum and $NH_3$ emission, we find no evidence that this H II region is interacting with Sgr A East. This conclusion supports that the star formation in this region has not been stimulated by the blast wave of Sgr A East.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.229-241
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• 2008

In order to investigate stabilization effect on As-contaminated soils treated by zero-valent iron(ZVI) and industrial by-products, batch tests and column tests were carried out with As-contaminated soils collected from farmland around the abandoned mine site. In batch tests, ZVI and industrial by-products(blast furnace slag, steel refining slag and oyster shell powder) were used as treatment materials to reduce As. Industrial by-products were mixed with As-contaminated soils, in the ratio of 1%, 3%, 5% and 7% on the weight base of dried soil. After incubation, all samples showed the reduction of As concentration and it was expected that ZVI and steel refining slag were effective treatment materials to remove As among treatment materials used in batch test. In column tests, columns were made by acrylic with the dimension of diameter=10cm, height=100cm, thickness=1cm and these columns were filled with untreated soils and treated soils mixed with ZVI and steel refining slag(mixing ratio=3%). Distilled water was discharged into the columns with the velocity of 1 pore-volume/day. During test, pH, EC, Eh and As concentration were measured in the regular term(1 pore-volume). As a result, ZVI and steel refining slag were shown 93%, 62% reduction of As concentration respectively by comparison with untreated soils. Therefore, if ZVI and steel refining slag are used as treatment materials in As-contaminated soils, it is expected that the As concentration in soils is reduced effectively.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.3
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• pp.251-260
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• 2003

Tunnel blasting has been performed with V-cut to investigate the characteristics. Blasting vibrations were measured at two directions, the proceed direction and side direction. Propagation characteristics were determined by regression analysis; square root scaled distance and cube root scaled distance with maximum charge per delay of the blast. Testing result, The cross point was 62m in the allowable vibration velocity of 3mm/sec and 46m in 5mm/sec. Also, vibration level with measuring point was highest and decayed fastest, adapting to cube root scaled distance, for the proceed direction on ground.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.6
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• pp.839-848
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• 2015

This study examined the optimal salting drying method and processing conditions (salt concentration, curing time, dry temperature, and drying time) for preparing salted semi-dried common gray mullet (SSD-CGM) Mugil cephalus based on the moisture content, salinity, and overall acceptance using response surface methodology (RSM). The moisture content, salinity, and overall acceptance of SSD-CGM prepared with different salting methods revealed that dry salting was the optimal salting method for preparing high-quality SSD-CGM. The optimal drying method for preparing high-quality SSD-CGM based on the drying velocity and sensory color was hot air-blast drying. The results of the RSM program indicated that the optimal independent variables ($X_1$, salt concentration; $X_2$, curing time; $X_3$, dry temperature; $X_4$, drying time) based on the dependent variables ($Y_1$, moisture content; $Y_2$, salinity; $Y_3$, overall acceptance) for high-quality SSD-CGM were 5.6% for $X_1$, 2.7 h for $X_2$, $47.0^{\circ}C$ for $X_3$, and 8.5 h for $X_4$ for uncoded values. The predicted values of $Y_1$, $Y_2$, and $Y_3$ for SSD-CGM prepared under optimal conditions were 54.4%, 4.2%, and 6.3, respectively, while the experimental values were $55.2{\pm}1.0%$, $4.1{\pm}0.3%$ and $6.7{\pm}0.8$. The actual and predicted values did not differ.