• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.11 no.1
• /
• pp.101-116
• /
• 1989

Proplast and Porous Polyethylene which have porous structures as low-modulus polymers have been recently used in maxillofacial plastic and reconstructive surgery. The purpose of this study was to compare the response of adajacent tissue, new bone formation and stability after augmentation by differen methods of subperiosteal graft using proplast and purous polythylene in rabbit mandible. The augmentation procedure was carried out by dividing into two groups, A and B. A group consisted of subperiosteal graft on the cortex, and the other B group was made up only graft following artificial decortication in the mandibular body of rabbit. The experimental animals were sacrificed on the 1st, 2nd, 4th and 8th week after grafting for macroscopic and light microscopic examination. The samples extracted at the 6th postgrafting week were also used for biometric testing and scanning electron microscopic examination. The results obtained from this study were as follows : 1. Macroscopically, infection of graft site, deformation and migration of graft material were not observed in all experimental groups. 2. B group showed more rapid and increased bone formation and the greater stability than A group, and tissue response was similar to each other. 3. In the tissue response, macrophages and cellular infiltrations were observed in Proplast group, but few in PHDPE group. 4. In bone formation of A group, Proplast group showed no bone formation until the 8th week, but PHDPE group showed small quantity of osteoid tissue from the 2nd week and appositional bone growth with new bone formation at the 8th week. 5. In bone formation of B group, both Proplast and PHDPE group showed bone formation, but PHDPE group showed more rapid and larger bone formation. 6. In pattern of bone formation, Proplast group mainly showed appositional bone growth pattern connected with graft site. On the other hand, PHDPE group showed mixed pattern of new bone formation in the pore connective tissue with appositional bone growth from graff site. 7. The maximum mean values of shear stress were serially $111.3gf/mm^{2}$ in PHDPE of B group, $84.8gf/mm^{2}$ in PHDPE of A group, $32.9gf/mm^{2}$ in Proplast B group, and $15.7gf/mm^{2}$ in Proplast of A group. From above results, It was suggested that the capacity of bone formation and stability between bone and graft material were dependent on the pore size and structure of graft material itself, the state of graft site and tissue response.

• Korean Journal of Medicinal Crop Science
• /
• v.10 no.3
• /
• pp.206-211
• /
• 2002

For developing natural presevatives, essential oils of Mentha arvensis L. var. piperascens Malivaud and Agastache rugosa O. Kuntze were analyzed the composition of two oils and experimented on microorganism survival. Main components of Mentha arvensis oil were isomenthol (26.84%) and menthol (25.48%), and those of Agastache rugosa oil were estragole (79.83%) and limonene (4.13%) from GC-MSD analysis. Inhibition activities of Mentha arvensis oil against growth of Escherichia coli O157 : H7 ATCC 43895 and Salmonella typhimurium ATCC 7988 were observed from their clear zone $(9{\sim}14 mm\;&\;9{\sim}13\;mm)$, and that of Agastache rugosa oil were done from the clear zone $(13{\sim}20 mm\;&\;10{\sim}18\;mm)$ by concentration-dependent manner, respectively. In the inhibition test on CFU/ml of the microorganisms, both of the plant essential oils at concentration of 5 and 10 mg showed potent growth inhibition activities from 9 hour of incubation. Analysis using transmission electron microscope on E. coli also showed antimicrobial activities of the oils as deformation of the cell and loss of the intracellular materials.

• Tunnel and Underground Space
• /
• v.14 no.6 s.53
• /
• pp.440-449
• /
• 2004

Rock mass includes natural discontinuities such as joints and faults during its formation. Discontinuities are also referred as planes of weakness because of their weak mechanical characteristics. In the design of underground structures, it is necessary to consider the properties of discontinuities to insure the stability. During the excavation of a tunnel, these discontinuities have to be identified as early as possible so that proper change in excavation method or support design can be made accordingly. The excavation of the tunnel in a stable rock mass causes a 3-dimensional arching effect around the excavation face. It was revealed by previous studies that the existence of a weak zone or a fault zone ahead of tunnel foe induces a typical displacement tendency of convergence. For better understanding of the meaning of influence/trend lines of various displacement components, three-dimensional numerical analyses were conducted while varying deformation moduli, thicknesses and orientations of discontinuities. Numerical results showed that the changes in influence/trend lines of various displacement components were very similar to those by measurements. The discrepancies from the expected values were dependent on the physical properties, thicknesses and orientations of discontinuities.

• Journal of the Korea Concrete Institute
• /
• v.28 no.5
• /
• pp.535-544
• /
• 2016

This paper aims at examining the effects of sustained load and elevated temperature on the time-dependent deformation of a carbon fiber reinforced polymer (CFRP) sheets bonded to concrete as well as the pull-off strength of single-lap shear specimens after the sustained loading period using digital images. Elevated temperature during the sustained loading period resulted in increased slip of the CFRP composites, whereas increased curing time of the polymer resin prior to the sustained loading period resulted in reduced slip. Pull-off tests conducted after sustained loading period showed that the presence of sustained load resulted in increased pull-off strength and interfacial fracture energy. This beneficial effect decreased with increased creep duration. Based on analysis of digital images, results on strain distributions and fracture surfaces indicated that stress relaxation of the epoxy occurred in the 30 mm closest to the loaded end of the CFRP composites during sustained loading, which increased the pull-off strength provided the failure locus remained mostly in the concrete. For longer sustained loading duration, the failure mode of concrete-CFRP bond region can change from a cohesive failure in the concrete to an interfacial failure along the concrete/epoxy interface, which diminished part of the strength increase due to the stress relaxation of the adhesive.

• Journal of the Korean Society for Railway
• /
• v.12 no.1
• /
• pp.31-38
• /
• 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
• /
• v.14 no.6
• /
• pp.892-899
• /
• 2002

Among the methods for enhancement of load-carrying capacity on flexural concrete member, recently, a concept is being investigated which replaces the steel in a conventional reinforced concrete member with a fiber reinforced polymer(FRP) shell. This study focuses on modeling of the structural behavior of concrete surrounded with FRP shells in flexural bending members. A numerical model of fiber cross-sectional analysis is proposed to predict the stress and deformation state of the FRP shell and concrete. The stress-strain relationship of concrete confined by a FRP shell is formulated to be based on the constitutive law of concrete in multi-axial compressive stress state, in assuming that the compression response is dependent on the radial expansion of the concrete. To describe the FRP shell behavior, equivalent orthotropic properties of in-plane behavior from classical lamination theory are used. The present model is validated to compare with the experiments of 4-point bending tests of FRP shell concrete beam, and has well predicted the moment-curvature relationships of the members, axial and hoop strains in the section, and the enhancement of confinement effect in concrete surrounded by FRP shell.

• Journal of the Ergonomics Society of Korea
• /
• v.34 no.4
• /
• pp.313-326
• /
• 2015

Objective: The objective of this research is to quantitatively analyze muscle activities of arm and shoulder, according to direction in various types of one-handed manual material handling, based on surface electromyography. Background: Workers in industrial sites frequently carry out one-handed manual material handling using arm and shoulder muscles. Therefore, chronic load and accumulated fatigue occur to arm and shoulder muscles, which becomes a main cause of upper arm and shoulder musculoskeletal disorders. The shoulder muscles have widely range of motion, and complex interactions take place among various muscles including rotator cuff muscles. In this regard, research on interactions among should muscles, according to such various dynamic motions, is required. Method: Ten male subjects in their 20s participated in this research. This research considered upward, downward, leftward, rightward, forward and backward directions and fourteen muscles around arm and shoulder (biceps brachii and trapezius, etc.) as independent variables. The mean muscle activity was set as the dependent variable. This research extracted $4^{th}{\sim}7^{th}$ repetition signals according to ten times of repetitive muscle contraction, and analyzed the muscle activity concerned using the envelope detection technique. Results: The mean muscle activity of upward direction was analyzed highly statistically significant. The reason is that the effect of gravity works to arm and shoulder muscles. Also, it is conjectured that deformation of coracoacromial ligament was caused, and its contact pressure increased, due mainly to the shoulder flexion, and therefore load was analyzed high. Muscle activity was analyzed significantly low, according to concentric ballistic motion used in the concentric contraction phase by storing elastic energy in the eccentric contraction phase with a motion to bring the weight to the front of subject's body as to downward, leftward and backward directions. Because, elbow joint's flexion-extension motions mainly occurred, biceps brachii was analyzed high muscle activity as the prime mover. Conclusion: The information on the quantitative load of muscles can be applied to ergonomic work design for one-handed manual material handling to minimize muscle load. Application: This research has effectively identified muscle activity according to dynamic contraction by applying an envelope detection technique. The results can be used for ergonomic work design to minimize muscle load during the one-handed manual material handling, according to each direction. The research results are expected to be used for musculoskeletal disorder prevention and physiotherapy in the rehabilitation medical field, based on the muscle load of arm and shoulder in various directions.

• Journal of Radiation Protection and Research
• /
• v.2 no.1
• /
• pp.17-23
• /
• 1977

The neutron dosimetrical parameters, i. e., the fission neutron spectrum-averaged cross-sections and the fluence-to-dose conversion factors have been calculated for some threshold detectors with the aid of a computer. The threshold detectors under investigation were the $^{115}In(n,\;n')^{115m}In,\;^{32}S(n,\;p)^{32}P$ and $^{27}Al(n,\;{\alpha})^{24}Na$ reactions. It is revealed that the average cross-sections($\bar{\sigma}$) for the $^{32}S(n,\;p)^{32}P$ reaction are independent of the spectral functions, namely, the Watt-Cranberg and Maxwellian forms. In the case of the $^{27}Al(n,\;{\alpha})^{24}Na$ reaction a variation of the $\bar{\sigma}$ values appears to be highly dependent on the fissioning types. It seems that both the average cross-section for the $^{115}In(n,\;n')^{11m}In$ reaction and the conversion factor are insensitive to the spectral deformation of fission neutrons. These phenomena make it applicable to use indium as a possible integral fast neutron dosimeter in nuclear criticality accidents provided that the virgin fission neutrons are completely free from the scattered neutrons.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.31 no.6
• /
• pp.386-394
• /
• 2019

In this study, according to drainage condition (undrained and drained) in ground, the settlement and horizontal displacement of caisson quay wall and apron in Yeongilman port due to excess pore water pressure in ground induced by the magnitude 5.4 earthquake in Pohang on November 15, 2017. In general, seismic response analysis was carried out under undrained drainage condition, but in this study, drain drainage analysis was conducted to estimate displacement during earthquake as well as an additional displacement due to dissipation of excess pore water pressure after earthquake. The result of after earthquake can not be known under undrained drainage condition. Results cleary showed that the behavior of structure and ground was dependent on drainage condition in ground. Especially, based on the drained drainage condition, the additional displacement was clearly detected due to dissipation of excess pore water pressure after earthquake. Which indicates that both results are different to drainage condition in ground, and therefore, drainage condition analysis is necessary to accurately estimate the behavior of ground and structure in seismic response analysis.

• Geotechnical Engineering
• /
• v.14 no.5
• /
• pp.5-16
• /
• 1998

2-D numerical methods have been applied to analyze the stability of tunnels because of computation efficiency, though the ground around the tunnel under construction shows 3-D reformational behaviour due to the transverse and longitudinal arching effects. Load distribution factors are introduced to the 2-D analysis for the consideration of the effects of the tunnel advance in three dimensions. The load distribution factors influence significantly the ground deformation and the load of primary supports like shotcrete and rockbolts. According to the previous studies for 3-D numerical studies. it was shown that load distribution factors were heavily dependent on the ground deformational properties, tunnel size and the advance length of a tunnel. However, as the quantitative methods evaluating the factors have not been presented yet, constant values have been assigned to the factors for 2-D analysis even if the conditions for tunnel design are different. Accordingly, this paper presents the method to evaluate quantitatively the load distribution factors through the regression analysis of 3-D analysis data on 72 design cases. Also, new modification to the load distribution factors are suggested for the ring-cut excavation method because the conventional 2-D analysis is not able to consider the support effects of the core left on the tunnel face.