• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.135-143
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• 2006

This study evaluated the fatigue resistance characteristics of hot-mix recycled asphalt mixtures which were prepared by a new blending method. Since the binder of RAP shows higher viscosity without being rejuvenated in the ordinary recycled mixture, this new(modified) blending method was developed for obtaining more uniform level of binder viscosity in the recycled mixture. Cold-planned RAP was collected and mix design was performed using 15% RAP content for two virgin aggregate, gneiss and granite. Penetration grade of 60-80 asphalt was used in mixing recycled mixture together with a polymer modifier, LDPE. Indirect tensile fatigue tests were carried out to evaluate characteristics of fatigue resistance of performance of recycled asphalt mixtures. The recycled mixtures with LDPE 6% showed higher repeated loading fatigue life. Fatigue life ratio of new(N) mixing method mixtures was approximately 0.6-0.7 before aging and 0.8-1.0 after aging treatment of ordinary(O) mixing method mixture. This means the N mixture becomes stronger with aging process increase. If further aging is treated, N mixture may be showing stronger resistance than O mixture.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.189-198
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• 2008

Generally, UFF A(Ultra Fine Fly Ash) has merit that advances a greater concrete workability and activates a greater pozzolanic reaction than common fly ash due to its ultra fine particle size. These properties enhance concrete durability by reducing permeability and increasing resistance of alkali silica reaction(ASR) and sulfate attack, etc. Due to these reasons, UFFA can be used in a rapid setting concrete. The purpose of this study is to develop and evaluate the rapid setting concrete with UFF A as a repair material for early-opening-to-traffic. In previous studies, if only UFFA is added to the rapid setting concrete mixture, pozzolanic reaction doesn't happen actively. Therefore, in this study, the chemical and physical tests were performed for rapid setting concrete with UFFA including calcium hydroxide and the activity of pozzolanic reaction was evaluated. Finally, the effectiveness of this mixture on enhancing concrete durability was investigated. As results, adding UFF A decreased the water/cement ratio of concrete, and compensated the reduced portion of the early strength of concrete. Also, rapid setting concrete with UFFA including calcium hydroxide activated a greater pozzolanic reaction than normal-UFF A concrete. As calcium hydroxide increases, electrical indication of concrete's ability to resist chloride ion penetration is promoted significantly.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.1041-1047
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• 1997

The influence of $\omega$-phenylalkylammonium salt on the critical micelle concentration (CMC) of SDS has been examined using the electric conductivity method. CMC of SDS exhibited the tendency to decrease with the length of alkyl group of additives. The effect of temperature on CMC of SDS in additive solutions has been observed in the range of $18^{\circ}C-50^{\circ}C$. The free energy(${\Delta}G_m^{\circ}$) for the micellization of SDS is negative and the entropy(${\Delta}S_m^{\circ}$) is a large positive value. The enthalpy(ΔHm0is positive in low temperature($18^{\circ}C$) and negative in high temperature($>25^{\circ}C$). In the prensence of organic additives, the micellization of SDS was considered as a spontaneous process and to involve a phase transition. The values of ΔGm0has shown the tendency to increase but the values of ${\Delta}S_m^{\circ}$ and ${\Delta}H_m^{\circ}$ to decrease with the length of alklyl group of additive salts. The changes in ${\Delta}\kappa$(difference of specific conductivity) with increasing mole ratio of additives in the mixed solutions indicated the formation of mixed micelles between SDS and additives. The effect of the length of alkyl chain on the micellization of SDS demonstrated the penetration of organic additives into the palisade layer of the SDS micelle.

• Restorative Dentistry and Endodontics
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• v.14 no.2
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• pp.38-48
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• 1989

The purpose of this study was to investigate the proper consistency of root canal sealer needed in obtaining an efficient canal obturation in injection-thermoplasticized low-temperature ($70^{\circ}C$) gutta-percha method. The sealer was made by incorporating zinc oxide powder into $0.5m{\ell}$ of eugenol and then the $0.5m{\ell}$ of mixture slurry was placed between two flat glass plates. The consistency was determined by measuring the degree of spread of the slurry at loading the 120gm of weight from the top plate. The sealer was prepared according to P/L ratio corresponding to the acquired consistency of 65.45mm, 46.80mm, 28.95mm and 22.60mm. The distal roots were obtained by cutting off from 125 extracted human lower molars and the root canals were prepared by using step-back method. The prepared canals were coated with the sealers on their walls and obturated by using the injection-thermoplasticized low-temperature ($70^{\circ}C$) gutta-percha method. All specimens were immersed in 2% methylene blue dye solution for 48 hours at $37^{\circ}C$. Calipers was used to measured the dye penetration into the root canals from apical constrictions. The results were as follows : The canals obturated without sealer showed significantly more leakage than the canals obturated with sealer. Within the consistency from 65.45mm to 22.60mm, the sealer of 65.45mm appeared significantly better than that of 28.95mm and 22.60mm in the canals obturated by injection-thermoplasticized gutta-percha method, and better than that of 46.80mm without statistical significance.

• Clean Technology
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• v.10 no.2
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• pp.61-72
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• 2004

In this study, aqueous/semi-aqueous cleaning agents which consist of organic solvent, surfactant, cosurfactant, and water were developed by changing formulation parameters such as organic solvent type and contents, surfactant type and contents, and cosurfactant/surfactant(A/S) ratio, etc.. And physical properties and flux removal of the formulated cleaning agents have been evaluated. Also, the performance of oil-water separation from the rinse water contaminated during the cleaning process was evaluated for its recycling. The formulated cleaning agents in this work expected to have good penetration because of their low viscosity and low surface tension values of 30.2~32.5 dyne/cm. The flux removal with the terpene type cleaning agent was higher than that with hydrocarbon type cleaning agent and two commercial products (CPA(commercial product A), CPB(commercial product B)). And the performance of oil-water separation by gravity settling from the rinse water contaminated with formulated cleaning agent and soils was shown to be very good. The cleaning agents developed in this work were applied to surface mounting technology(SMT) cleaning process for manufacturing electronic parts at L electronic company. As a result, the newly developed cleaning agents showed two times better cleaning speed for removal of solder cream than the conventional ond containing ethanol and IPA(isopropyl alcohol). In addition, malodor and VOC problems generated by the previous organic cleaning agents have been solved in the manufacturing field through introduction of the non-volatile and environmental-friendly cleaning agents to the field.

• Korean Journal of Agricultural Science
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• v.4 no.1
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• pp.26-33
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• 1977

We have studied the responce of nitrogen on the newly bred varieties, Yusin and Milyang #23, and the effects of defoliation at maturing stage on the rate of ripened grains under different nitrogen levels. The results obtained are summarized as follows : 1. Milyang #23 as well as Tongil was found to be highly nitrogen responsive variety and showed good grain maturing percentage. The number of grain per unit area affected the total yield under the high levels of nitrogen application. The variety, Yusin, was less responsive to nitrogen and had also less leaf area than other varieties under the high level of nitrogen application. Yusin also seemed to have low maturing percentage due to unbalanced ratio between photosynthetic area and size of storage. 2. The low internodes and leaf blade of Yusin and Milyang #15 were grown too much under high levels of nitrogen and these caused more lodging and less light penetration in pant canopy. 3. The effects of defoliation at maturing stage on yield was high under the high levels of nitrogen application, especially when defoliation was done early stage of maturing. The effects of defoliation appeared to be greates in Tongil than in Milyang #15.

• Conservation Science in Museum
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• v.6
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• pp.55-66
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• 2005

Three types of epoxy resins (Epo-Tek 301, Araldite 103, and Araldite 106) and three types of pigments (bunche, pastel, and conté), which are materials for porcelain restoration, were selected as examination materials. The tone change, porosity, and sedimental resulting from the mixtures of varying ratios of these three materials were observed. Samples were also made from the mixture of Epo-teck 301, four kinds of white pigments, and six types of fillers and subjected to ultraviolet ray penetration for 200 hours to observe the oxidation of the epoxy resins. The result showed that the chemical composition of pastel drastically changed when mixed with Epo-tek 301. Although bunche and conté displayed clear colors, those of conté were less clear when it was mixed with other substances. Adding a small amount of Epo-tek 301 tended to be driven into the corner, whereas mixing a large amount caused saturation and boiling. On the other hand, AW 106 did not display clear colors owing to its high viscosity; when mixed in large amounts, however, the clarity of colors improved. For AY 103, a similar standard of color clarity was maintained regardless of the mixture ratio. The following was ranked according to the level of porosity: [Pastel>bunche≒conté]. In terms of sedimentary, however, [bunche>conté>Pastel], [Epo-tek 301> AY 103> AW 106]. The result of measuring the degree of yellowing revealed that titanium, pastel, silicon dioxide, and kaolin tended to turn yellow, whereas bunche, conté, diatomaceous earth, and calcium hydroxide tended to resist yellowing.

• The Korean Journal of Pesticide Science
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• v.15 no.4
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• pp.507-528
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• 2011

Agricultural workers who mix/loads and spray pesticide in fields expose to pesticide through dermal and inhalation routes. In such situation, exposed amount should be measured quantitatively for reasonable risk assessment. Patch, gloves, socks and mask will be good materials for monitoring for dermal exposure while personal air monitor equipped with solid adsorbent and air pump will be a tool for inhalation exposure. For extrapolation of absorbed amount in dermal exposure matrices and of trapped amount in solid sorbent to total deraml or inhalation exposure, Korean standard body surface area and respiration rate were proposed in substitution of EPA data. Important exposure factors such as clothing and skin penetration ratio of dermal and inhalation exposure were suggested based on Spraying time for exposure monitoring must be long enough that the amount of pesticide to get absorbed/trapped in exposure matrices results in reasonable analytical value. In domestic case for the both of speed sprayer and power spray machine, spraying time of 20~40 minutes (0.1~0.2 ha) will be reasonable per single replicate before extrapolating to 4 hours a day with triplicates experiment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.92-100
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• 2015

The aim of this study is to evaluate the fracture characteristics of ductile fiber reinforced cement based composites with 1.5 volume ratio of polyvinyl alcohol and steel fiber by high velocity impact of steel projectile. We used gunpowder impact facility to evaluate the fracture characteristics of ductile fiber reinforced cement based composites by collision of steel projectile, and the impact velocity was from about 150 to 1,000m/s. The results of evaluation on the fracture characteristics of ductile fiber reinforced cement based composites were penetration grade, which is the kinetic energy more than three times of no-fiber reinforced specimen (Plain). In addition, ductile fiber reinforced cement based composites did not occurred critical damage other than the debris. In the case of mass loss, Plain specimen was proportional to kinetic energy of steel projectile, while ductile fiber reinforced cement based composites was not significantly affected by kinetic energy of steel projectile. In particular, this tendency had a close relationship with the fracture characteristics of back side of specimens, and the scabbing inhibiting efficiency of PVA specimen was higher than S specimen. In the results of verifying relationship between front and back side calculated by local damage, scabbing occurred at the region close to the back side in the ductile fiber reinforced cement based composites unlike Plain specimen. Thus, in this study, we examined principal fracture behaviors of ductile fiber reinforced cement based composites under collision of steel projectile, and verified that impact resistance performance was improved as compared to Plain specimen.

• Journal of the Korean Society of Food Science and Nutrition
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• v.11 no.4
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• pp.17-24
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• 1982

Optimum moisture content of about 60% of cooked rice was obtained by soaking the fully steamed rice with 35% moisture conture content in ambient water temperature$(24^{\circ}C)$ for one hour. Two different levels of package vacuum was used in packing this cooked rice in retort pouch, and the effect of the levels of package vacuum on the texture of the cooked rice in the pouch during thermal process was investigated: Higher sterilization value (Fo value) and steeper slope (fh value) on the heating curve of the thermal process was obtained with the higher package vacuum product. The j value of the heating curves of cooked rice packed in retort pouch was ranged between 0.80 and 1.18 without respect to the levels of the package vacuum and the process temperature. Although in respective of the ratio of the stickiness to the hardness (-H/H) the product with higher package vacuum showed better result, the shape of most of the rice grain in the vacuum vacuum pouch was deformed and Jumped mass of inferior quality than the one in the lower vacuum package.