• Journal of Periodontal and Implant Science
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• v.38 no.4
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• pp.595-602
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• 2008

Purpose: Ti-6Al-4V alloy is widely used as an implant material because of its good biocompatibility and good mechanical property compared with commercial pure titanium. Otherwise, toxicity of aluminum and vanadium in vivo has been reported. Ti-8Ta-3Nb alloy is recently developed in the R&D Center for Ti and Special Alloys and it was reported that this alloy has high mechanical strength, no cytotoxicity and similar biocompatibility to commercial pure titanium, but many studies are needed for its clinical use. In these experiment, we carried out different surface treatment on each Ti-8Ta-3Nb alloy disks, then cultured cell on it and assessed biological response. Materials and Methods: cpTi, Ti-6Al-4V, Ti-8Ta-3Nb alloy disks were prepared and carried out sandblasting and acid etching (SLA) or alkali-heat treatment (AH) on the Ti-8Ta-3Nb alloy disks. We cultured primary rat calvarial cells on each surface and assessed early cell attachment and proliferation by scanning electron microscopy, cell proliferation, alkaline phosphatase activity. Result: The rates of cell proliferation on the cpTi, Ti-8Ta-3Nb AH disks were higher than others (p<0.05) and alkaline phosphatase activity was significantly enhanced on the Ti-STa-8Nb AH disks(p<0.05). Conclusion: Most favorable cell response was shown on the Ti-8Ta-3Nb AH surfaces. It is supposed that alkali-heat treatment of the Ti-8Ta-3Nb alloy could be induced earlier bone healing and osseointegration than smooth surface.

• Journal of the Korean Electrochemical Society
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• v.6 no.2
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• pp.113-118
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• 2003

Processible polyaniline (PAM) dispersions consisting of polyaniline micro-particles, cyclohexanone, and a polymeric surfactant were prepared in a micro-milling machine with various mixing conditions. The electrochemical properties of the dispersion film coated on Pt electrode were investigated by cyclic voltammetry (CV). The electrochemistry of the PAM dispersion coatings was basically similar to a pure PAM coating based on the results of CV. The results of polarization measurements and open circuit potential measurements carried out in $3\;wt.\%$ NaCI solution showed increase in corrosion potential when the PANI dispersion coatings applied on steel surface. Variation of open circuit potential $(OCP,\;V_{OC})$ of the dispersion coating/steel electrodes was observed, which differed with milling conditions. The results demonstrated practical use of the conducting polymer dispersion as a coating material for corrosion prevention of steel.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.4
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• pp.515-520
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• 2010

The response of broiler chicks to intubation of nutrients (starch, casein, soybean oil or their combinations) into the crop immediately after hatch was evaluated for performance, intestinal development, meat yield and immune competence up to 35 d of age. A control group with no access to feed and two test groups fed either inert material (sawdust) or starter diet for the initial 24 h after hatch were compared with nutrient intubated groups (n = 7). A total of 300 broiler chicks were equally distributed to 10 dietary groups with 6 replicates of 5 chicks each. After 24 h of hatch, all groups were fed ad libitum the starter (0-21 d) and finisher diets (22-35 d). Results indicated that post-hatch intubation of starch into the crop significantly (p${\leq}$0.05) improved body weight (at 14 and 35 d of age), readyto-cook meat yields, weights of breast muscle and small intestine segments, cell-mediated immune response, ND titers and weight of bursa compared to chicks starved or fed sawdust during the initial 24 h after hatch. However, chicks with access to feed immediately after hatch or intubation of starch, soybean oil, starch+casein, starch+soybean oil or starch+casein+soybean oil exhibited similar positive effects. Intubation of casein either alone or in combination with soybean oil was superior to the starved or sawdust fed groups, but inferior to other groups for all the parameters studied. It was concluded from the study that intubation of starch individually or in combination with casein and/or soybean oil effectively circumvented the negative effects of post-hatch starvation for 24 h. Among the nutrients intubated, carbohydrate (starch) was better utilized by the chicks than protein (casein) or fat during the initial post-hatch period.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.3
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• pp.31-39
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• 2008

Until now, there are many technologies to improve studying ability using e-learning system. In most of e-learning system, learners are studying through the lecture materials and studying problems. The studying ability and intention, however, can be improved through the shared materials and discussion. In this case, learning materials are shared by the learners' discussion and shared materials through the board Internet and MSN. Such data was not classified by learners; it was not easy for the learners to search related valuable information. Therefore, it was not helping to learning. The technologies of most text mining extract summary data from the collection of document or classify into similar document from the complex document. In this paper, we implemented e-learning system for learners to improve learning abilities and especially, applied text mining technology to classify learning material for helping learners.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.451-456
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• 2015

This study aimed to evaluate of the hardened properties (mortar consistency, setting time, absorption properties, drying shrinkage, and bond strength) of the basalt powder sludge mortar recycling a basalt powder sludge occurred during the manufacture process of basalt stone as a replacing material for the sea-sand used to cement filling compound for surface preparation. The hardened mortar made of the basalt powder sludge showed an enhanced performance or similar with the properties of normal mortar used to cement filling compound for surface preparation. But, the drying shrinkage was increased more than a normal cement mortar in the hardened mortar made of the basalt powder sludge since curing 8 - 9days. And the bond strength is low in the hardened mortar used the basalt powder sludge. On the whole, properties of the hardened mortar used the basalt powder sludge correspond to the required minimum quality criterion in the KS F 4716 'cement filling compound for surface preparation'.

• Journal of the Korea Institute of Building Construction
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• v.10 no.4
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• pp.3-9
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• 2010

Fire resistance and material properties of high-strength concrete (W/B 21.5%, 28.5%) with OPC, BS and FA were tested in this study. Main factors of the test consisted of fiber mixing ratio and W/B. Two types of fiber (NY, PP) mixed with the same weight were used for the test. The fiber mixing ratios were 0%, 0.05%, 0.1%, and 0.2% of the concrete weight. After performing the test, Under the W/B level of 21.5% and 28.5%, the spalling was effectively resisted by using the high strength concrete with fiber mixing ratios of 0.05%~0.1%. Compressive strength, flowability and air content are similar those of the fiberless high-strength concrete with the same W/B.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1908-1918
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• 1991

Fatigue tests have been carried out to measure the degradation of the residual strength and the fatigue life in carbon/epoxy (0/45/90/-45)$_{2s}$ composite materials. Theoretical predictions of residual strength and fatigue life were compared with experimental results. Distribution characteristics were studied using the probability of failure based on the cumulative distribution function and median rand. The static ultimate strength of carbon/epoxy composites used herein is observed to be relatively higher than that of existing similar composites ; while fatigue life is shorter due to the brittleness of matrix. The fatigue life obtained in these experiments is shorter than that estimated by residual strength degradation model when the stress level above 0.6 For the stress level of 0.6, the experimental value was abruptly increased. The cumulative distribution function for the static ultimate strength is well correlated to that for the strength converted from the measured fatigue life. Also, the predicted distribution of residual strength shows good agreement with the experimental results. Therefore, it is proven that the residual strength degradation model is reasonable.e.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.808-815
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• 2007

The optical performance of the mirror fur satellite camera is highly dependent on the adhesive properties between the mirror and its support. Therefore, in order to design a mirror with high optical performance, the mechanical properties of adhesives should be well defined. In this research, the mechanical properties of three kinds of space adhesives are studied. In case of the materials which show nearly incompressible behavior such as space adhesives, it is important to measure shear modulus which governs deviatoric stress components. Also the experiment should be performed in circumstances similar to real manufacturing process of mirror, because extra factors such as size effects, the adhesion effects of primer and reactions between adhesive and primer affect the properties of adhesive regions. In this research shear moduli of the adhesives are determined by using a single lap adhesively bonded joint. For the shear tests, several temperatures have been selected from $-20^{\circ}C$ to $55^{\circ}C$ which is operating temperature range of the adhesive. In the case of linear behavior materials, shear moduli are calculated through a linear curve fitting. Shear stress-strain relation is obtained by using an exponential curve fitting for material which shows non-linear behavior. The shear modulus of each adhesive is expressed as a function of temperature. Characteristics and adaptability of the adhesives are discussed regarding their temperature sensitivity.

• Journal of Mushroom
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• v.16 no.2
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• pp.70-73
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• 2018

To determine the optimum amount of spent oyster mushroom substrate (SOMS) for use in cultivation of Lentinula edodes, the chemical properties of the substrate and culture conditions of Lentinula edodes were investigated. Replacing 20-50% of a sawdust substrate with SOMS yielded a C/N ratio of 62-76. In case of substrates containing SOMS, the total nitrogen and phenolic contents of were higher, whereas fructose and organic acid contents were lower than those of the control substrate. Cultivation tests showed that the 3-cycle yield of 20% SOMS treatment was 286.7 g, similar to that of the control, while 50% SOMS treatment significantly decreased the yield. In conclusion, development of oak mushroom substrate using SOMS would recycle waste products and decrease material costs.

• Applied Chemistry for Engineering
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• v.29 no.3
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• pp.303-306
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• 2018

Methyl 4-formylbenzoate (MFB), a by-product of the DMT production process, which has been disposed, was used as a starting material for the synthesis of six new fluorescent whitening agent's candidates with 4,4'-di((E)-styryl)-1,1'-biphenyl skeleton attached with an aromatic ester, the same as that of the commercial product family. All candidates were synthesized by the reaction of MFB, and its derivatives with tetraethyl biphenyl-4,4'-diylbis(methylene)diphosphonate using Wittig-Horner reaction. UV spectra for all candidates were recorded and the data were used for calculating the molar absorptivity in order to confirm the usability as a fluorescent whitening agent. All of them showed overall molar extinction coefficients (log ${\varepsilon}$ 4.59~5.00) similar to those of conventional commercial products (log ${\varepsilon}$ 4.85). In particular, compounds 16 and 17 having a dimethoxyphenyl group exhibited a molar extinction coefficient superior to those of conventional commercial products, and thus a field testing for commercialization will be conducted.