• Journal of the Korean Geotechnical Society
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• v.23 no.7
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• pp.77-86
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• 2007

Installation damage of 3 types of geogrids was evaluated with compaction condition by laboratory tester. This experimental was in accordance with ENV ISO 10722-1. First, soil distribution and water content were conducted. And then we changed cyclic loading time and type of geogrids as a factor of installation damage. The samples are woven, warp-knitted, welded type of 6, 8, 10T. This study aims to give an insight into the relationships between installation damage and cyclic loading time. The result of studies was that strength of the damaged geogrids can be closely correlated with the time of loading cycles. Especially, welded type shows slower slope than two types of geogrids due to coating materials. That means welded type is coated with PP (Polypropylene), but the other two types of geogrids are coated with PVC (Polyvinyl Chloride). To confirm another factor different method was performed. The size of soil was used between 9.5 mm and 23.5 m to compare initial experimental. Cyclic loading compaction is taken 200 times before installation test and the reason is that the reduction factor of this case by installation damage was higher than other compaction loading conditions.

• Korean Journal of Agricultural Science
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• v.6 no.2
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• pp.185-191
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• 1979

Compressive and tensile strengths of commonly being used mortar and mortar specially hardened by adding 1%, 2% and 3% of $CaCl_2$ were compared under the different mixing ratio of mortar and ages to investigate the effect of $CaCl_2$ which is being used as a promotor for coagulation and hardness, on the strength of mortar. The results obtained were as follows: 1. The compressive strength of mortar hardened by addition of $CaCl_2$ was higher than that of commonly being used mortar. The highest compressive strength of mortar was obtained when 2% of $CaCl_2$ were added. 2. The tensile strength of mortar, which was made by adding $CaCl_2$ and aged for seven days, was higher than that of commonly being used mortar. The highest tensile strength of mortar was obtained when 1% of $CaCl_2$ was added and aged for 28 days. And the tensile strength of mortar with 2% of $CaCl_2$ was lower than that of commonly being used mortar. 3. When the amount of $CaCl_2$ added was higher than 3%, the mortar was abruptly hardened and thereby occurred crack was considered lowering strength of mortar. 4. The rich mix was effective for the increasing the compressive and tensile strength before seven days of age and less effective after seven days of age. Therefore, the addition of one to two per cent of $CaCl_2$ would be effective for promoting initial strength of mortar during winter season.

• International Journal of Highway Engineering
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• v.3 no.4 s.10
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• pp.93-103
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• 2001

This study focused on the field applicability evaluation of SB latex-modified concrete (LMC) for concrete bridge deck overlay using mobile mixer. The main experimental factors were water-cement ratio(31, 33, 35 37%), latex contents(0, 5, 10, 15, 20%), and fine aggregate ratio(55, 56, 57, 58%) in order to evaluate the workability, mechanical properties, and durability property of LMC. The slump loss, air content, compressive and flexible strength tests were used to evaluate LMC workability and strength properties. Also, the rapid chloride permeability test was used to evaluate the relative permeability of LMC. As a results, the LMC with enough workability and good quality was produced when it was mixed in field using mobile mixer, satisfying the target compressive strength and flexural strength. The required water-cement ratio of LMC for same workability when mixing with mobile mixer was less than that when mixing in laboratory. Increasing the amount of latex produced concrete with increased flexural strength by mobile mixer. The required cement-water ratios for same initial $19{\pm}3cm$ slump were 37% and 33% at laboratory and mobile mixer, respectively. The mobile mixer was accurately calibrated satisfying the required specification.

• Polymer(Korea)
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• v.26 no.5
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• pp.691-700
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• 2002

Interstitial therapy using biodegradable polymeric device loaded with anticancer agent can deliver the drug to the tumor site at high concentration, resulting in an increase of therapeutic efficacy. 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, carmustine) is most commonly used as chemotherapeutic agent for brain tumors. The design of implantable device is regarded as an important factor lot the efficient delivery of antitumor agent to targeting site. In order to control the release profile of drug, the release pattern of BCNU with the changes of various dimension and additives was investigated. The PLGA wafers containing 3.85, 10, 20 and 30% of BCNU were prepared in various shape (diameter of 3, 5 and 10 mm, thickness of 0.5, 1 and 2 mm) by direct compression method. In vitro drug release profile of BCNU-loaded PLGA wafers could be controlled by changing the dimension of wafers such as initial drug content, weight, diameter, thickness, volume and surface area of wafers, as well as PLGA molecular weight and additives. Drug release from BCNU-loaded PLGA wafers was facilitated with an increase of BCNU-loading amount or presence of poly(N-vinylpyrrolidone)(PVP) or sodium chloride (NaCl). The effects of various geometric factors and additives on the BCNU release pattern were confirmed by the investigation of mass loss and morphology of BCNU-loaded PLGA wafers.

• Applied Biological Chemistry
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• v.19 no.4
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• pp.219-226
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• 1976

To meet the need of protein feed and fine more efficient ways of returning waste to resources, we have carried out the study of the production of yeast for foods and feeds from the corn starch cake. The present study includes the method for acid-hydrolysis, the selection of yeast capable of utilizing hydrolyzate of the corn starch cake, and culture condition of Candida tropicalis under the liquid culture and the semisolid culture. Obtained results were as follows. 1. Hydrochloric acid was more excellent on the hydrolysis of the corn starch cake than sulfuric acid, and the yield of sugar was maximum, 57.2%, when the corn starch cake was hydrolyzed with 1.0% of hydrochloric acid at 2.0kg/cm for 30 minutes. 2. As the acid solution content was increased, more sugar was liberatedfrom the mixture, until the acid solution-substrate ratio reached 10:1. Beyond this point, no further increase was observed. To prepare the cultural medium of semisolid fermentation, a acid solution to substrate ratio of 3:1 appeared to be optimum. 3. Out of 6 yeast strains, Candida tropicalis had excellent growth on the hydrolyzate of the corn starch cake, and optimum temperature and initial pH were $30^{\circ}C$ and 6.0 respectively. 4. Optimum liquid medium of Candida tropicalis is ures 0.3%, potassium phosphate monobasic 0.15g and magnesium sulfate 0.04g in 100ml of the hydrolyzate of the corn starch cake, while optimum semisolid medium is ammonium chloride 0.4g, potassium phosphate monobasic 0.1%, magnesium sulfate 0.04%. 5. Candida tropicalis could assimilate the sugar in the hydrolyzate up to more than 88.75%, and a yield of dry yeast reached 19.13% to the corn starch cake under the liquid culture. 6. Compared to the that of the untreated corn starch cake, the cellulose content of the semisolid fermented cake decreased by 3.76% to 14.7%, whereas dry yeast contents increased by 13.89%.

• Journal of Animal Environmental Science
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• v.11 no.3
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• pp.207-214
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• 2005

To reduce phosphorus and nitrogen from the swine wastewater, magnesium chloride $(MgCl_2)$ was used as a reaction material for both soluble phosphorus (SP) and ammonia-nitrogen (AN). The initial value of SP content were $471mg/\ell$ far aeration test and $515 mg/\ell$ for NaOH addition test, but treatment of $MgCl_2$ reduced SP value to $5mg/\ell$ and $4mg/\ell$. The removal efficiency of $MgCl_2$ for SP showed $99\%$ in both treatment, and the removal efficiency of $MgCl_2$ for AN showed $15\%$ with treatment of aeration and $18\%$ with NaOH. All the experiments were done in a low temperature of 6 to $8^{\circ}C$, suggesting that this methods are possibly able to apply to a cold weather conditions. Moreover, the struvite crystal structure was identified by electronic microscope, implying that $MgCl_2$ is an effective material for removal of SP from swine wastewater In addition to the increased removal rate of the AN in wastewater, both $MgCl_2$ and $KH_2PO_4$ were added. The SP value was reduced by $99\%$ with 2g addition of the phosphate. The SP removal rate by 4g addition of the phosphate was increased only as $15-19\%$, but the quantity of removed SP was higher than that of 2g addition test. The value of AN was not reduced as expected by adding $KH_2PO_4$. The AN removal rate were low as $18\%$ and $15\%$ like as the level of the former test with $MgCl_2$ alone. Therefore, it is needed to examine closely the reaction mechanism f3r reducing both SP and AN simultaneously.