• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.909-916
• /
• 2013

Concrete containing lightly burnt MgO has long term expansibility. It also could compensate for the thermal shrinkage of mass concrete, because the hydration of MgO proceeds at a slow pace to long-term age. Thus, lightly burnt MgO has been applied to the construction of mass concrete such as dams. Recently, the expansion characteristics of MgO concrete with fly ash that could be applied to mass concrete for the reduction of hydration heat have been studied and however, limited studies on its durability. This study investigates the long-term durability characteristics of fly ash concrete with lightly burnt MgO. The durability tests on carbonation, freezing-thawing, diffusion of chloride, and resistance to sulfate attack were carried out for MgO concrete with curing for 360 days in submerged condition with different temperature of 20 and $50^{\circ}C$. The results reveal that MgO concrete shows a greater resistance of carbonation, diffusion of chloride, and resistance to sulfate attack. On the other hand the resistance of freezing-thawing was little influenced by MgO powder.

• Journal of the Korean Applied Science and Technology
• /
• v.11 no.2
• /
• pp.69-74
• /
• 1994

Durable softening water repellents for nylon fiber were synthesized, using two compounds: quaternized octadecyl methacrylate-2-diethylaminoethyl methacrylate copolymer as a mother resin of water repellent and quaternized fatty carbamide for improving softness and hydrostatic pressure, of which syntheses were studied in the previous papers. They were blended with waxes and emulsifiers in a variety of ratios and synthesized into water repellent PADWC, and it was nylon taffeta treated with and without textile finishing resin. The synthesized water repellents can be used either or without resin. The optimum curing temperature was 150 to 160$^{\circ}C$ and the optimum concentration was 3 to 5wt%. In the independent and conjunct treatment, the water repellency of nylon taffeta samples have no remarkable changes between initial value and that after three times washing, so these prove that the synthesized compounds are durable water repellent. The water repellency of PADWC-3 and -4 were around 90. Also, comparison of crease recovery and tear strength after repelling treatment showed that the synthesized water repellents have a very high softening effect.

• Fisheries and Aquatic Sciences
• /
• v.3 no.3_4
• /
• pp.200-204
• /
• 2000

To investigate pre-salting conditions in the preparation of salted anchovy from large anchovy, anchovy were salted with various salt concentration and stored at $5^{\circ}C$ and $20^{\circ}C$ for 10 days. Moisture content decreased with the increase of salt and the salinity increased in proportion to salt concentration at $20^{\circ}C$. Total nitrogen decreased slightly as the increase of salt concentration during pre-salting at $20^{\circ}C$. The nitrogenous components such as amino nitrogen and extractable nitrogen were invariable or decreased until 7 days in salt concentration over $25\%$ during pre-salting at $5^{\circ}C$. These results imply that soluble nitrogen with moisture run out of anchovy body in high salt concentration and the hydrolysis was inhibited by salt over $25\%$ at $5^{\circ}C$. VBN content were constant in salt concentration over $25\%$ until 7 days, regardless of curing temperature. The POV were under the influence of salt concentration and temperatures. We concluded that the optimal condition for preparation of salted anchovy were pre-salting with salt over $25\%$ at $5^{\circ}C$ for 7 days.

• Journal of the Korean Society of Tobacco Science
• /
• v.17 no.2
• /
• pp.126-138
• /
• 1995

To investigate the changes of physicochemical properties of leaf tobacco during storage, cured leaves (both flue-cured(KF109) and burley(Burley 21) : 4 grades of leaves) were stored under the natural warehouse condition(room temperature) and processed leaves(both Rue-cured(NC82) and burly(Burley 21) : 6 grades of leaves) were stored at storerooms in tobacco processing plants(flue-cured Cheongju plant ; 2nd, 4th and 5th floor, burley : Kwangju plant ; 2nd floor, Chonju plant : 3rd and 5th floor). Tobacco leaves were sampled and analyzed every 3 months. Total sugar content of flue-cured leaf decreased slightly and the redness degree of leaf increased after 15 months' storage under the natural warehouse conditions. The pH of cured leaves were lowered both flue-cured and burley, and the decreasing rate of pH was large in flue-cured(0.24) as compared with burley(0.14). There was no significant differences of physicochemical properties of processed leaf among storerooms during 15 months' storage. The decreasing rate of processed leaf pH was somewhat large in flue-cured(0.26) as compared with burly (0.20), and in thick leaves as compared with thin leaves. The redness degree of flue-cured leaf increased slightly, while the degree of lightness and yellowness lowered slightly during storage. The lightness degree of burley leaf lowered slightly, too. The ageing process of cured leaf was similar to that of processed leaf, it is considered that the passing days after curing will be more reasonable than the passing days after processing for the establishment of proper ageing period.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.280-280
• /
• 2010

Semiconductor quantum dots are of great interest for both fundamental research and industrial applications due to their unique size dependant properties. The most promising application of colloidal semiconductor nanocrystals (quantum dots or QDs) is probably as emitters in biomedical labeling, LEDs, lasers etc. As compared to II-VI quantum dots, III-V have attracted greater interest owing to their less ionic lattice, larger exciton diameters and reduced toxicity. Among the III-V semiconductor quantum dots, Indium Phosphide (InP) is a popular material due to its bulk band gap of 1.35 (eV) which is responsible for the photoluminescence emission wavelength ranging from blue to near infrared with change in size of QDs. Nevertheless, in recent years, the exact type of collective properties that arise when semiconductor quantum dots (QDs) are assembled into two- or three-dimensional arrays has drawn much interest. The term "uantum dot solids" is used to indicate three-dimensional assemblies of semiconductor QDs. The optoelectronic properties of the quantum dot solids are known to depend on the electronic structure of the individual quantum dot building blocks and on their electronic interactions. This paper reports an efficient and rapid method to produce highly luminescent and monodisperse quantum dots solution and solid through fabrication of InP thin films. By varying the molar concentration of Indium to Ligand, QDs of different size were prepared. The absorption and emission behaviors were also studied. Similar measurements were also performed on InP quantum dot solid by fabricating InP thin films. The optical properties of the thin films are measured at different curing temperatures which show a blue shift with increase in temperature. The dielectric properties of the thin films were also investigated by Capacitance-voltage(C-V) measurements in a metal-insulator-semiconductor (MIS) device.

• The Journal of the Korean Society for Microbiology
• /
• v.21 no.1
• /
• pp.33-45
• /
• 1986

On hundred and forty stains of shigella cultures isolated from the twelve hygiene laboratories of cities and provincial general hospital laboratories in 1983 were tested for their resistance to thirteen antimicrobial drugs and their R-plasmid transfer. Antimicrobial drugs were used amikacin, ampicillin, cephalothin, chloramphenicol, gentamicin, kanamycin, nalidixic acid, rifampicin, streptamycin, tetracycline, tobramycin, cefoperazone and piperacillin. All strains were resistant to one or more of thirteen antimicrobial drugs but 94.3% were susceptible to amikacin, gentamicin and tobramycin of total isolated. The most strains commonly found resistance was to chloramphenicol (94%) followed by streptamycin (93%), tetracyline (92%) piperacillin (90%) ampicillin (83%), cefoperazone (42%), nalidixic acid (14%), cephalothin (17%), rifampicin (22%) and kanamycin (6%), sixty percent of strains among 140 were resistance to ampicillin, chloramphenicol, streptomycin, tetracycline at the same time. The transfer of drug resistance by conjugation was tested and ninety four strains (94.3%) were resistant to one or more drugs were found to transfer their drug resistance of E. coli. percentage of transfer frequency by conjugation was one strains (54%), the transfer frequency of drug resistance varied by donor strains and recipients, but not by selecting drugs. Resistance to nalidixic acid was not transferred by conjugation to recipients. Percentage of plasmid curing after the treatment of acriflavine, acridine orange was about 8%. Among strains cured two strains were tested compare original strains with them in biochemical properties in arginine dihydrolase and arabinose fermentation reaction. It was found to growth curves of No.2 shigella flexneri, serotype 1b, and its derivatives cured with acriflavine in $M{\ddot{u}}ller$ Hinton broth medium (pH 7.4, $38^{\circ}C$) by temperature Gradient Biophoto Recorder TN-1120 (Tokyo, Japan).

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2006.05a
• /
• pp.35-38
• /
• 2006

This study investigated fundamental properties of lightweight foamed concrete using cement kiln dust (CKD) and both fly ash(FA) and stability agent. Test results showed that concrete incorporating more amounts of admixture decreased slump flow and it caused increase of superplasiticizer in order to secure the fluidity performance. In addition concrete adding stability agent showed stable flow state, resisting segregation of materials and decreasing bleeding capacity. Sinking depth of concrete incorporating 20% of CKD and adding 0.002% of stability agent was indicated at 0mm. For the properties of hardened concrete. compressive strength of concrete incorporating CKD declined due to a lower appearance density, compared with other specimens. The difference of that was not very significant and the value of ail specimen was higher than KS range. Moreover strength of concrete incorporating CKD was even higher at curing temperature $5^{\circ}C$. Tensile strength ratio of concrete incorporating CKD was indicated between 0.50 to 0.59, which is higher value than control concrete. Heat conductivity of concrete incorporating FA was under the KS range while concrete incorporating 20% of CKD was satisfied in KS. Concrete adding stability agent improved insulation performance due to the lower heat conductivity. In conclusion, it is possible that concrete incorporating 20% of CKD and adding 0.002% of stability agent can secure high quality of lightweight foamed concrete.

• Journal of the Korean Ceramic Society
• /
• v.45 no.11
• /
• pp.734-738
• /
• 2008

Ettringite$(3CaO{\cdot}Al_2O_3{\cdot}3CaSO_4{\cdot}32H_2O)$, one of the hydrated phase of Portland cement is usually formed in the early stage of hydration by the reaction of tricalciumaluminate$(C_3A)$ and gypsum. The rapid and strong crystal growth of separated rod-shaped ettringite have been utilized for the preparation of special cements of rapid setting, high strength and non-shrinking properties. The ettringite also has been noticed as a promising materials for the immobilization of various waste ions because of its unique crystal structure which has abundant channels and exchangeable ionic compounds. In this study, the formation and growth behavior of the ettringite was investigated in the system $C_3A-CaSO_4-H_2O$ using $C_3A$ clinker and gypsum to obtain a microporous body for waste ion immobilization. Ettringite was revealed to form by the dissolution-precipitation mechanism and the bulk body was by the entangled growth of rod-shaped ettringite crystals. The hardened body was composed of nearly pure rod-shaped ettringite interlocked each other with adequate mechanical strength. The homogeneity of structure, pore size, specific surface area and porosity of the hardened body were influenced by reaction temperature, water/powder ratio and the curing time. The hardened body prepared with water/powder ratio of 1 at $24^{\circ}C$ for one day showed excellent morphological properties for the purposed materials.

• Polymer(Korea)
• /
• v.35 no.2
• /
• pp.136-140
• /
• 2011

The plasma resistances of nitrile curable perfluoro elastomer (NT PFE) and peroxide curable PFE (PO PFE) after exposing to $NF_3$ and $O_2$ remote plasmas were investigated by analyzing weight loss and morphology of O-ring made of PFE. The compounds were designed following the typical formulations of O-ring/seal which were applied in semiconductor and LCD production site. They were blended by an open roll mill, and then, O-ring was finally made by hot press molding and oven curing. The weight loss was calculated and morphology was observed for each atmosphere and temperature by a digital weighing machine and SEM. As results, it was confirmed the weight loss and related morphology were meaningfully different according to the cure type of PFE, filler system, and the species of remote plasma.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.10
• /
• pp.2227-2232
• /
• 2009

Novel polythiol materials of urethane lens series for plastic optical lens were synthesized from polyol materials via thioisouronium of thiourea with c-HCl in refluxing aqueous solution, in which polythiol material was carried out from hydrolysis of thioisouronium by ammonia water. Their structure properties were identified by EA, EI-MS, FT-IR, $^1H\;and\;^{13}C$ NMR spectroscopies and TGA. Their ophthalmic lenses as polythiourethane material were prepared by thermal curing to an injected glass mold using the evenly solutions of diisocyanates series (TDI, XDI, HDI or IPDI) with polythiols. Polythiourethane shows that the strong stretching mode for SH group of polythiol disappeared in FT-IR spectra after thermosetting polymerization. Thermal deformation starting temperature of ophthalmic lenses was determined by TMA. Ophthalmic lenses made from characteristic polythiol and diisocyanate series have transparency, colorless and good impact strength, in which thermal resistance and impact strength of ophthalmic lenses were influenced by diisocyanate series. Physical properties of ophthalmic lens have contrast thermal resistance with impact strength. The property of thermal resistance and impact strength for respective ophthalmic lenses was examined by TMA and drop ball test.