• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.31-38
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• 2009

The selection of the support system is an important design parameter in design and construction of the tunnel using the new Australian tunnel method. It is a common practice to select the support based on the rock mass grade, in which the rock mass is classified into five rock groups. The method is applicable if the characteristics of the rock mass are uniform in the direction of tunnel excavation. However, such case is seldom encountered in practice and not applicable when the properties vary along the longitudinal direction. This study performs comprehensive three dimensional finite difference analyses to investigate the ground deformation pattern for cases in which the rock mass properties change in the direction of the tunnel axis. The numerically calculated displacements at the tunnel crown show that the displacement is highly dependent on the stiffness contrast of the rock masses. The results strongly indicate the need to select the support type $0.5{\sim}1.0D$ before the rock mass boundary. The paper proposes a new guideline for selecting the support type based the results of the analyses.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.541-548
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• 2009

A theoretical prediction model of fiber bridging curve was established based on the assumption that fibers are uniformly distributed on the crack surface. However, the distance between fibers and their orientation with respect to crack surface can greatly affect the prediction of fiber bridging curve. Since, the shape of fiber bridging curve is a critical factor for predicting the tensile stress-strain relationship of ECC, it is expected that the assumption of uniform distribution of fiber may cause a significant error when predicting the tensile behavior of ECC. To overcome this shortcoming, a new prediction method of stress-strain relation of ECC is proposed based on the modified fiber bridging curve. Only effective fibers are taken into account considering the effects of their orientation and distance between them. Moreover, the approach for formulating the tensile stress-strain relation is discussed, where a procedure is presented for obtaining important parameters, such as the first crack strength, the peak stress, the displacement at peak stress, tensile strain capacity, and the crack spacing. Subsequent uniaxial tensile tests were performed to validate the proposed method. It was found that the predicted stress-strain relations obtained based on the proposed modified fiber bridging curve exhibited a good agreement with experimental results.

• Journal of Periodontal and Implant Science
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• v.42 no.2
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• pp.59-63
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• 2012

Purpose: This study evaluated the surface characteristics and bond strength produced using a novel technique for coating hydroxyapatite (HA) onto titanium implants. Methods: HA was coated on the titanium implant surface using a super-high-speed (SHS) blasting method with highly purified HA. The coating was performed at a low temperature, unlike conventional HA coating methods. Coating thickness was measured. The novel HA-coated disc was fabricated. X-ray diffraction analysis was performed directly on the disc to evaluate crystallinity. Four novel HA-coated discs and four resorbable blast medium (RBM) discs were prepared. Their surface roughnesses and areas were measured. Five puretitanium, RBM-treated, and novel HA-coated discs were prepared. Contact angle was measured. Two-way analysis of variance and the post-hoc Scheffe's test were used to analyze differences between the groups, with those with a probability of P<0.05 considered to be statistically significant. To evaluate exfoliation of the coating layer, 7 sites on the mandibles from 7 mongrel dogs were used. Other sites were used for another research project. In total, seven novel HA-coated implants were placed 2 months after extraction of premolars according to the manufacturer's instructions. The dogs were sacrificed 8 weeks after implant surgery. Implants were removed using a ratchet driver. The surface of the retrieved implants was evaluated microscopically. Results: A uniform HA coating layer was formed on the titanium implants with no deformation of the RBM titanium surface microtexture when an SHS blasting method was used. Conclusions: These HA-coated implants exhibited increased roughness, crystallinity, and wettability when compared with RBM implants.

• Journal of Korean Society of Steel Construction
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• v.21 no.1
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• pp.37-44
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• 2009

A truss deck system that has replaced the slab form conventional method has become widely used in the construction of reinforced concrete structures as well as steel structures. The current commercial products, however, have some problems. The discontinuity between the lattice wires on the joint of the bottom wire induces vierendeel behavior, which increases the deflection of the system. In this research, a new truss deck system with continuous lattice wires on the level of the bottom wire was developed to reduce the system's vierendeel behavior and to improve its deformation capacity. To investigate the system's structural behavior, an experimental test and an analysis were performed. The main parameters of the test and analysis were the longitudinal shape and spacing of the lattices. To simulate the loading condition in the construction field, uniform construction loads were directly applied on the deck plates of the analysis model and the test specimens. The results of such analysis and test revealed that the longitudinal shape of the lattice wires is a major factor affecting the structural behavior of a steel wire truss deck. Thus, continuous lattice wires could result in decreased vierendeel behavior in the steel wire truss deck. It was also found that the truss deck system with lattices spaced longer than in the conventional products could be effectively used without increasing the member stresses.

• Journal of Food Hygiene and Safety
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• v.33 no.4
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• pp.272-279
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• 2018

The high pressure processing (HPP) is a technology which can preserve the quality of foods, such as the fresh taste, incense, texture, vitamin content, and so on, by minimizing the heating process. It does so by applying an instantaneous and uniform pressure that is the same as the water pressure that is 60 km deep in the sea. HPP is a technology that can inhibit food poisoning and spoilage caused by microorganisms and is currently an actively studied area. In this study, we investigated the effects of a high pressure treatment (0, 4, 6 min) on sliced ham, which is a typical meat product, at 600 MP a were tested for their effect on freshness. Moisture contents varied from 48 to 69%, salinity varied from 1.07 to 1.11%, and the pH decreased from 6.4~6.5 to 6.1~5.15. However, there was no difference between the control and treatment groups. General bacteria stored at $20^{\circ}C$ after hyper-pressure treatment were found to have no significant microorganisms in all groups until 4 weeks. but exceeded $10^5$ in control group and HPP 6 min treatment group from 5 weeks, At week 7, it was found to exceed $10^6$. The results indicate it was not possible to ingest food in the 4-and 6 minute treatment groups. Coliform was not observed in all groups despite observing for a total of 7 weeks at $20^{\circ}C$ weight test. VBN, a method used to determine the protein freshness of meat, showed a VBN value of less than 1 mg% until the fourth week and a value of 1 to 2 mg% after 5 weeks. The TBA was used as an index of the degree of fat acidosis in the meat tissues. The results showed it was below 0.18 mgMA / kg until the end of 7 weeks; this value was within the range for fresh meat, and there was no difference in treatment group. In this experiment, deformation of the packaging material did not occur and no swelling occurred due to the generation of gas. It is believed that the basic preservation effect was achieved only by blocking with the air due to the close contact of the packaging material.

• Korean Journal of Weed Science
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• v.9 no.1
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• pp.56-68
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• 1989

aA series of experiments were conducted to investigate the effect of plant growth regulator treatments on the growth and lateral root formation in soybean sprouts in order to establish the effective method of producing root-less or short-rooted soybean sprouts with larger diameter in the hypocotyl. Major results can be summarized as follows. 1. Soybean sprouts showed fairly uniform elongation rate from 3 to g days after imbibition with daily increase of 3.8cm. The speed of elongation of hypocotyl was reduced whereas that of root accelerated 7 days after imbibition. Lateral roots began to emerge fairly evenly from 5 to 9 days after imbibition with a daily increase of 4.4. 2. Auxins(IAA, IBA, NAA, 2,4-D) inhibited hypocotyl elongation and formation of lateral roots and increased hypocotyl diameter without influencing root length and hook diameter at higher concentrations. The dry weight of cotyledon was increased significantly as compared to that of hypocotyl and root. Among the tested auxins, 2, 4-D was the most effective. 3. BA and 4PU-30 significantly reduced elongation of hypocotyl and root and resulted in the biggest diameter of hypocotyl when treated at higher concentrations. The lowest effective concentration of BA to prevent the formation of larval gal roots was 12.5ppm. The formation of lateral roots could be completely prevented by BA and 4PU-30 treatment but kinetin, zeatin, zeatin riboside resulted in many lateral roots and increased thickness of soybean sprouts with little influence. Cotyledon deformation was found in soybean sprouts treated by 4PU-30. 4. 2, 4-D was the most effective for increasing the hypocotyl diameter while 4PU-30 was the most effective for reducing no. of lateral roots. 5. It can be concluded that among the plant growth regulators tested, BA was effective in reducing root length and increasing hypocotyl diameter. BA 12.5 ppm or 15 ppm may thus be the more practical for production of soybean sprouts. 6. ABA showed no significant effect of growth parameter, however ABA 25 ppm inhibited only no of lateral roots with little influence on the growth of seedling. 7. Ethephon inhibited the elongation of hypocotyl and root and increased hypocotyl diameter at higher concentrations. 8. The combined effect of cytokinins and ethephon was very similar to result of BA treatment alone. As the ethephon concentration increased, hypocotyl diameter and dry weight of cotyledon tended to increase.