• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.162-167
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• 1999

GaN epilayers deposited by the OMVPE method on sapphires with 3 different surface orientations were investigated by TEM and their difference in mucrostructure were compared with each other. GaN epilayers were grown on the all three kinds of sapphire substrates; however, the best interfacial state and crystallinity were observed in the specimen using a {0001} substrate The density of defects in GaN epilayers on {0001} substrates was also less than others. No buffer layer was found at the interfaces of all the specimens; however, it was observed that the region which shows lattice distortion at the interface was only a few nonameter wide. Accordingly, TEM investigation revealed that GaN epilayers having some internal defects could be grown on sapphire {1120} and {1102} planes without a buffer layer, and the hetero-epitaxial GaN films were obtained from the specimen using {0001} substrates with the microstructural point of view.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.79-86
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• 2015

This research proposed a design direction for the ambulance interior storage space based on the placement and access to the equipment to facilitate an emergency medical practice taking into account the safety and efficiency by the emergency medical technician ergonomic factors. Therefore, through a field survey for the current derivation of the storage space problem 'placement', 'enable', 'management' like these three items resulting clarity, accessibility, simplicity and functionality of the four functional elements by targeting ambulances in operation in this country. First, there is a need to improve standardized of cabinet sizes fit to loaded meet emergency equipment standards. Currently, the equipment designed to use a simple storage cabinet has had problems in the usability. Second, it must be located in the continuous exposure in progress to the user's traffic line. Third, the problem was the insufficient function of the cabinet to ensure the safety of patients by paramedics from the emergency rescue equipment and due to the leaning of the ambulance driving. Besides, it was pointed out that in addition to the proposed alternatives, including the agenda, states that safety belt replacement equipment, emergency personnel and patients with the handle of a guardian for the efficient use storage space within the 119 ambulance. However, in the present study suggest that there is a state proceeds mainly limited usability in the field, having been installed.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.85-87
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• 1990

Silicon nitride film was deposited on a silicon wafer using a laser CVD(LCVD) technique, which is based on direct photolysis of $SiH_4/NH_3$ gas mixture by ArF laser beam(${\lambda}=193\;nm$). The refractive index of deposited SiN film is 1.9 at the temperature of $300^{\circ}C$, pressure of 5 torr. The breakdown field strength of LCVD SiN film was 10MV/cm. In IR spectrum, the absorption peak of Si-H, N-H, and Si-N is detected and it is shown that hydrogen is included in SiN film. From analysis of absorption band. it is calculated that density of Si-H, N-H bond is higher than $5{\times}10^{22}cm^{-3}$. LCVD MIS capacitor and PECVD MIS capacitor have injection-type hysteresis but it is known that hysteresis loss of LCVD MIS capacitor is smaller than that of PECVD MIS capacitor. It means that Interface state density of LCVD capacitor is smaller than that of PECVD capacitor. In addition, the flatband voltage($V_{FB}$) of LCVD is smaller than that of PECVD capacitor. And it means that fixed charged density($Q_{FIX}$) of LCVD capacitor is smaller than that of PECVD MIS capacitor.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.18 no.2
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• pp.224-235
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• 1996

Early implantation before sufficient ossification has taken place usually results in osseointegartion failure due to reduced bone-fixture interface area. However, various studies have shown successful osseointegration results following immediate implants concurrently with GTR. The clinical trends have been to shorten the patients' edentulous state by immediate implantation, and reduce the alveolar bone resorption. However, it may be difficult to attain the complete soft tissue coverage of the sites, increasing the chance of infection. Furthermore, there may be more studies needed on the clinical behaviors of e-PTFE membranes, various modofications in the membrane materials and bone graft materials. Various animal and clinical studies have been reported on the successful osseointagration following immediate implantation, but the long-term follow-up studies are limited. The present study investigated 16 immediately-implanted implants with GTR therapy with or without calcium carbonate grafting on 11 patients 3 years after installation and 24-30 months after functional loading. Based on the clinical, radiographic and histologic findings, the following results have been attained. 1. Clinically, stability has been shown on all 16 implants throughout the investigated periods. 2. Radiologically, the alveolar bone loss has progressed up to the polished neck portion but not beyond it, suggesting the progressive osseointegration from the GTR therapy. 3. The GTR method used in the present study is easy to use clinically, and may be appied in the regeneration of ossoeous defects around implants and in the immediate implantation. 4. The difficulty in complete tissue coverage may be avoided by delaying the installation for 2 to 3 weeks after the extraction allowing certain degree of soft tissue healing.

• Fibers and Polymers
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• v.3 no.1
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• pp.8-13
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• 2002

The effect of block sequence on the self-assembly of ABC-type triblock copolymers in the ordered state is investigated using an isothermal-isobaric molecular dynamics simulation. The block sequence has an important effect ,on the ]norphology of ABC triblock copolymers. Different morphologies are observed depending on the block sequence as well as the block composition. The triblock copolymers with the volume fraction of 1 : 1 : 1 ($f_A$=$f_B$=$f_C$= 0.33) show the three phase and four layered lamellar structures irrespective of the block sequence. The $A_{32}$$B_{16}$$C_{32}$triblock copolymer with $f_B$=0.2 shows a morphology In which cylinders of midblock B are formed at the interface between A and C lamellae, whereas the morphology of triblock copolymer $B_{16}$$C_{32}$ $A_{32}$ and $C_{32}$ $A_{32}$ $B_{16}$ show a cylindrical core-shell structure and a lamellar type morphology, respectively. The $A_{20}$$B_{40}$$C_{20}$the triblock copolymer with the block B as a major component shows a tricontinuous structure, whereas both $B_{40}$$C_{20}$$A_{20}$ and $C_{20}$$A_{20}$$B_{40}$ triblock coolymers exhibit the lamellar structures. When the block B has larger volrome fraction with $f_B$=0.75, the matrix is composed of block B, and other two blocks A and C form spherical domains.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.1
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• pp.31-42
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• 2007

The purpose of this study was to compare the stress distribution according to the splinting condition and non-splinting conditions on the finite element models of the two units implant prostheses. The finite element model was designed with the parallel placement of two fixtures ($4.0mm{\times}11.5mm$) on the mandibular 1st and 2nd molars. A cemented abutment and gold screw were used for superstructures. A FEA models assumed a state of optimal osseointegration, as the bone quality, inner cancellous bone and outer 2 mm compact bone was designed. This concluded that the cortical and trabecular bone were assumed to be perfectly bonded to the implant. Splinting condition had 2 mm contact surface and non-splinting condition had $8{\mu}m$ gap between two implant prosthesis. Two group (Splinting and non-splinting) were loaded with 200 N magnitude in vertical axis direction and were divided with subdivision group. Subdivision group was composed of three loading point; Center of central fossa, the 2 mm and 4 mm buccal offset point from the central fossa. Von Mises stress value were recorded and compared in the fixture-bone interface and bucco-lingual sections. The results were as follows; 1. In the vertical loading condition of central fossa, splinting condition had shown a different von Mises stress pattern compared to the non-splinting condition, while the maximum von Mises stress was similar. 2. Stresses around abutment screw were more concentrated in the splinting condition than the non-splinting condition. As the distance from central fossa increased, the stress concentration increased around abutment screw. 3. The magnitude of the stress in the cortical bone, fixture, abutment and gold screw were greater with the 4 mm buccal offset loading of the vertical axis than with the central loading.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.33-40
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• 1988

The new technique has been used to determine the soil-reinforcement interaction. The testing apparatus is essentially a triaxial cell fitted with the capability to house a hollow cylinderical sample. A hollow cylinderical sand specimen with a concentrical layer of reinfarcing material sandwitched in the middle is used in this investigation. The reinforcement is fastened at the base. The hollow specimen can be viewed as a "unit sheet" of a soil-reinforcement composite system of infinite horizontal extent. Axial load as well as inner and outer chamber pressures can be applied to perform a test. The specimen is first subjected to an isotropic stress state corresponding to the overburden pressure. Next, an extension test by reducing the axial load is carried out. The specimen is "loaded" to failure by either the breakage of reinforcing material (tensile failure) or slippage which takes place at the soil-reinforcement interface (i.e. the overcoming of the bonding capacity). Since the reinforcement is fastened at its lower end to the base, any tendency of relative movement between the reinforcement and the sand during an extension test can induce tensile force in the reinforcement thus forming a "reversed pull-out" test condition. Preliminary test results have demonstrated positively of the new approach to test the soil-reinforcement interaction. Reinforcing elements of different extensibility were used to study the deformbility of reinforced soil. Furthermore, both the breakage and the pull-out modes of failure were observed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.11-19
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• 2015

We present the results of a multi-material numerical investigation of the propagation of a combustible gas mixture detonation in narrow metal tubes. We use an experimentally tuned one step Arrhenius chemical reaction and ideal gas equation of state (EOS) to describe stoichiometric $H_2-O_2$ and $C_2H_4-O_2$ detonations. The purely plastic deformations of copper and steel tubes are modeled using the Mie-Gruneisen EOS and Johnson-Cook strength model. To precisely track the interface motion between the detonating gas and the deforming wall, we use the hybrid particle level-sets within the ghost fluid framework. The calculated results are validated against the experimental data because the results explain the process of the generation and subsequent interaction of the expansion wave with the high-strain-rate deformation of the walls.

• Proceedings of the ESK Conference
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• 1995.10a
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• pp.208-213
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• 1995

The vehicle navigation system is developed for helping driver to retrieve driving information more easily and lastly. Navigation System informs driver many pieces of driving information - roadway structure and system, on-line traffic condition, the position of vehicle, route guidance, destination and other infor- mation service. As the style of information is diverse and the amount of information is large, driver may have mental and visual overload. The display of information can disturb the driver's attention and this can cause accidents. This state is caused by the defect of human-machine interactions. When the navigation system is designed, human factors - cognitive, judgment, operating -must be considered. The display style must be designed simply and easily, not to be obstacle of human - machine interface. In this study, outside- in view display style and inside-out view display style are compared each other. Tow factors are measured. One is cognitive factor-time of cognition on information that is displayed by screen display, cognition error rate. The other is image of screen display - subject's feeling about several styles of display, degree of subject's preference. The prototype of roadway is four kinds -Cross, T-cross and O-cross. Roadway display for test is taken from paper maps. Traffic condition display style, vehicle position display style and route guidance display style are taken from current display style. Traffic condition display style is symbol. vehicle position display style and route guidance display style are described as color and symbol. The test on screen display is implemented doing given tasks. Then the test is analyzed statistically. The result of test analysis gives the guideline to the designer for the map display of the vehicle navigation system.

• International Journal of Highway Engineering
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• v.8 no.1 s.27
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• pp.139-152
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• 2006

Many experimental and numerical approaches have been developed to evaluate paving materials and to predict pavement response and distress. Micromechanical simulation modeling is a technology that can reduce the number of physical tests required in material formulation and design and that can provide more details, e.g., the internal stress and strain state, and energy evolution and dissipation in simulated specimens with realistic microstructural features. A clustered distinct element modeling (DEM) approach was implemented In the two-dimensional particle flow software package (PFC-2D) to study the complex behavior observed in asphalt mixture fracturing. The relationship between continuous and discontinuous material properties was defined based on the potential energy approach. The theoretical relationship was validated with the uniform axial compression and cantilever beam model using two-dimensional plane strain and plane stress models. A bilinear cohesive displacement-softening model was implemented as an intrinsic interface and applied for both homogeneous and heterogeneous fracture modeling in order to simulate behavior in the fracture process zone and to simulate crack propagation. A disk-shaped compact tension test (DC(T)) with heterogeneous microstructure was simulated and compared with the experimental fracture test results to study Mode I fracture. The realistic arbitrary crack propagation including crack deflection, microcracking, crack face sliding, crack branching, and crack tip blunting could be represented in the fracture models. This micromechanical modeling approach represents the early developmental stages towards a 'virtual asphalt laboratory,' where simulations of laboratory tests and eventually field response and distress predictions can be made to enhance our understanding of pavement distress mechanisms, such its thermal fracture, reflective cracking, and fatigue crack growth.