• Journal of Technologic Dentistry
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• v.22 no.1
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• pp.79-88
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• 2000

The objective of this finite element method study was to analyze the stress distribution induced in a maxillary central incisor Ni-Cr base metal coping ceramic crowns with various margin design. Margin designs of crown in this experiment were knife-edge metal margin on chamfer finishing line of tooth preparation(M1), butt metal margin on shoulder finishing line(M2), reinforced butt metal margin on shoulder finishing line(M3), beveled metal margin on bevelde shoulder finishing line(M4). Two- dimensional finite element models of crown designs were subjected to a simulated biting force of 100N which was forced over porcelain near the lingual incisal edge. Base on plane stress analysis, the maxium von Miss stresses(Mpa) in porcelain venner was 0.432, in metal coping was 0.579, in dentin abutment was 0.324 for M1 model, and M2 model revealed in porcelain was 0.556, in metal coping was 0.511, in dentin was 0.339, and M3 model revealed in porcelain was 0.556, in metal coping was 0.794, in dentin was 0.383 for M4 model. All values of each material in metal-ceramic crown were much below the critical failure values.

• Structural Engineering and Mechanics
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• v.60 no.4
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• pp.547-565
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• 2016

In this work a new 3-unknown non-polynomial shear deformation theory for the buckling and vibration analyses of functionally graded material (FGM) sandwich plates is presented. The present theory accounts for non-linear in plane displacement and constant transverse displacement through the plate thickness, complies with plate surface boundary conditions, and in this manner a shear correction factor is not required. The main advantage of this theory is that, in addition to including the shear deformation effect, the displacement field is modelled with only 3 unknowns as the case of the classical plate theory (CPT) and which is even less than the first order shear deformation theory (FSDT). The plate properties are assumed to vary according to a power law distribution of the volume fraction of the constituents. Equations of motion are derived from the Hamilton's principle. Analytical solutions of natural frequency and critical buckling load for functionally graded sandwich plates are obtained using the Navier solution. The results obtained for plate with various thickness ratios using the present non-polynomial plate theory are not only substantially more accurate than those obtained using the classical plate theory, but are almost comparable to those obtained using higher order theories with more number of unknown functions.

• Smart Structures and Systems
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• v.26 no.2
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• pp.213-226
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• 2020

In this manuscript, static and dynamic behaviors of geometrically imperfect carbon nanotubes (CNTs) subject to different types of end conditions are investigated. The Doublet Mechanics (DM) theory, which is length scale dependent theory, is used in the analysis. The Euler-Bernoulli kinematic and nonlinear mid-plane stretching effect are considered through analysis. The governing equation of imperfect CNTs is a sixth order nonlinear integro-partial-differential equation. The buckling problem is discretized via the differential-integral-quadrature method (DIQM) and then it is solved using Newton's method. The equation of linear vibration problem is discretized using DIQM and then solved as a linear eigenvalue problem to get natural frequencies and corresponding mode shapes. The DIQM results are compared with analytical ones available in the literature and excellent agreement is obtained. The numerical results are depicted to illustrate the influence of length scale parameter, imperfection amplitude and shear foundation constant on critical buckling load, post-buckling configuration and linear vibration behavior. The current model is effective in designing of NEMS, nano-sensor and nano-actuator manufactured by CNTs.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.1-6
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• 2000

FFP(Fitness For Purpose) type defect assessment methodologies based on ECA(Engineering Critical Analysis) have been established and are in use for the structural integrity evaluation of gas pipelines. ECA usually includes the fracture mechanics analysis, and it assumes that J-integral uniquely characterizes crack-tip stress-strain fields. However, it has been shown that it is not sufficient to characterize the crack-tip field under low levels of constraint with a single parameter. Since pipeline structures are made of ductile material, locally loaded in tension, cracks may experience low level of constraint, and therefore, J-dominance will be lost. For this reason, the level of constraint must be quantified to establish a precise assessment procedure for pipeline defects. The objective of this paper is to Investigate the fracture behavior of a crack in gas pipeline by quantifying the level of constraint. For this purpose, tensile tests and CTOD tests were performed at room temperature$(24^{\circ}C)$ and low temperature$(-40^{\circ}C)$ to obtain the material properties. J-Q analyses were performed for SENB and SENT specimens based on 2-D finite element analyses, in order to investigate the in-plane constraint effects on pipeline defects.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.292-292
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• 2014

Wide band gap semiconductors, such as III-nitrides (GaN, AlN, InN, and their alloys), SiC, and diamond are expected to play an important role in the next-generation electronic devices. Specifically, GaN-based high electron mobility transistors (HEMTs) have been targeted for high power, high frequency, and high temperature operation electronic devices for mobile communication systems, radars, and power electronics because of their high critical breakdown fields, high saturation velocities, and high thermal conductivities. For the stable operation, high power, high frequency and high breakdown voltage and high current density, the fabrication methods have to be optimized with considerable attention. In this study, low ohmic contact resistance and smooth surface morphology to AlGaN/GaN on 2 inch c-plane sapphire substrate has been obtained with stepwise annealing at three different temperatures. The metallization was performed under deposition of a composite metal layer of Ti/Al/Ni/Au with thickness. After multi-layer metal stacking, rapid thermal annealing (RTA) process was applied with stepwise annealing temperature program profile. As results, we obtained a minimum specific contact resistance of $1.6{\times}10^{-7}{\Omega}cm2$.

• Progress in Superconductivity
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• v.8 no.1
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• pp.8-15
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• 2006

The size of the superconducting domains and the critical current density inside these domains have to be enhanced for most of cryomagnetic applications of melt-textured YBCO bulks. To enlarge the size of the domains we studied the multi-seeding technique based on a well-established procedure for preparing high quality YBCO monoliths using self-made SmBCO seeds. The distance between the seeds was optimised as a result of the investigation of the effects of various seed distances on the characteristics of the grain boundary Junctions. The influences of a-b plane intersections and c-axis misalignments were researched. Thereby, a small range of tolerance of the misorientations between the seed crystals was found. Field mapping was applied to control the materials quality and the superconductor's grain structure was investigated using polarisation microscopy. YBCO function elements with iou. seeds in a line and an arrangement of making type (100)/(100) and (110)/(110) boundary junctions, respectively, were processed. The trapped field profile in both sample types shows single domain behaviour. To demonstrate the potential of the multi-seeding method a ring-shaped sample was processed by placing sixteen seeds in a way to make both (100)/(100) and (110)/(110) grain junctions at the same time. The results up to now are very promising to prepare large single domain melt-textured YBCO semi-finished products in complex shapes.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.259-269
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• 2017

Gust load is a very important load factor in designing various structures of an aircraft and judging its stability. This is because the blast effect on the aircraft in operation increases the risk of damage to the structure of the aircraft and causes a negative impact such as shortening the fatigue life by generating vibration. Particularly in the case of wing, a change in angle of attack is caused by gust load, and an additional lift acts on the wing, thereby being exposed to various excitational environments. Severe structural damage to the aircraft may occur if the natural frequencies of the aircraft wing are close to or coincident with the frequencies of the gust load applied to the wing. Recent trends of research include flight dynamics analysis considering discontinuous gusts or structural optimization of the blades under gust load. A number of studies have been conducted to interpret gust load response in consideration of irregularities in gusts. In this paper, we tried to imagine the situation of the aircraft subjected to the gust load as realistic as possible, and proposed an algorithm to track back the critical gust profile according to given aircraft characteristics from the viewpoint of preliminary engineering prediction.

• Journal of Educational Research in Mathematics
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• v.22 no.2
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• pp.261-275
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• 2012

There are some geometry achievement standards presented indistinctly in middle school mathematics curriculum revised in 2011. In this study, indistinctness of some geometric topics presented indistinctly such as symbol $\overline{AB}{\perp}\overline{CD}$ simple construction, properties of congruent plane figures, solid of revolution, determination condition of the triangle, justification, center of similarity, position of similarity, middle point connection theorem in triangle, Pythagorean theorem, properties of inscribed angle are discussed. The following three agenda is suggested as conclusions for the development of next middle school mathematics curriculum. First is a resolving unclarity of curriculum. Second is an issuing an authoritative commentary for mathematics curriculum. Third is a developing curriculum based on the accumulation of sufficient researches.

• Plant Journal
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• v.8 no.2
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• pp.59-69
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• 2012

This study focuses on avoiding the failures from the wrong selections by experiences as simulation programs is not available, and suggests the methods which effectively select the alternatives when the selected model is not appropriate for the original plan. First, CC8800-1K of DEMAG has the longest boom whose length is 216 m at the maximum. The combination of the boom is feasible to second level except for MANITIWOC M 2250 (M-1200 RINGER) which is possible to third level. Second, the angle of boom is from 20 degrees to 82 degrees. Suitable angle to work is in the 55-78 degrees. The working load of crawler type and hydraulic one to be applied is 75-85% in the critical loads capacity. As increasing operating radius, crawler type is a favorable position over hydraulic one. Lastly, related problems were verified through examination by suggestions for the design of the selection methods for the case analysis. The major problems are stemming from the selection based on its experiences, unreasonable demand for the existing facility and repeated selections by the designer who accumulates his experiences via same or similar projects.

• Advanced Composite Materials
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• v.16 no.2
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• pp.95-113
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• 2007

Experimental investigations of interlaminar mechanical properties for carbon fiber reinforced plastic (CFRP) laminates were carried out using aramid fiber ($Kevlar^{(R)}$-29 1000d) and carbon fiber (TR40-1K 612d, Mitsubishi Rayon) stitching. Various carbon fiber (CF) stitch densities were used to prepare a number of CF stitched CFRP laminates for double cantilever beam (DCB) tests. An insert tongue-type loading fixture, developed by the Japan Aerospace Exploration Agency (formerly the National Aerospace Laboratory of Japan), was also employed in the DCB test. Interlaminar tension tests were carried out under an out-of-plane directional loading using a single CF stitch thread in the CFRP laminates. The DCB test results clarified that the relationship between the volume fractions of the CF stitch thread ($V_{ft}$) and mode I critical energy release rate ($G_{Ic}$) showed a mostly linear function with a higher gradient than that of the $Kevlar^{(R)}$ stitched CFRP laminates. The CF stitched CFRP tension test results indicated that the consumption energy per unit area ($E_i$) was larger than that of $Kevlar^{(R)}$ stitched CFRP laminates.