• 한국세라믹학회지
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• 제26권2호
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• pp.201-209
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• 1989

Fine Si-Al-OH coprecipitate powders were prepared from Si- and Al-alkoxides by the hydrolysis method. $\beta$-Sialon powder was obtained from prepared Si-Al-OH coprecipitate by the simultaneous reduction and nitridation method. The syntehsized Sialon powder was pressureless sintered at 175$0^{\circ}C$ for 90 min in N2 atmosphere. The characterization of the Sialon powder was performed with XRD, BET, SEM, TEM and particle size analysis. The sinterability and mechanical properties of sintered bodies were investigated in terms of relative density, M.O.R., fracture toughness, hardness and the morphology of microstructure. The highest values of their mechanical properties were obtained for the $\beta$-Sialon ceramics at Z=1 and those values are as follows : M.O.R., KIC and HV of $\beta$-Sialon ceramics(Z=1) are 499.1 MPa, 5.9MN/m3/2 and 18.7GPa, respectively.

• Structural Engineering and Mechanics
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• 제75권6호
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• pp.685-699
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• 2020

Polygonal finite element provides a great flexibility in mesh generation of crack propagation problems where the topology of the domain changes significantly. However, the control of the discretization error in such problems is a main concern. In this paper, a polygonal-FEM is presented in modeling of crack propagation problems via an automatic adaptive mesh refinement procedure. The adaptive mesh refinement is accomplished based on the Zienkiewicz-Zhu error estimator in conjunction with a weighted SPR technique. Adaptive mesh refinement is employed in some steps for reduction of the discretization error and not for tracking the crack. In the steps that no adaptive mesh refinement is required, local modifications are applied on the mesh to prevent poor polygonal element shapes. Finally, several numerical examples are analyzed to demonstrate the efficiency, accuracy and robustness of the proposed computational algorithm in crack propagation problems.

• 한국공작기계학회논문집
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• 제11권6호
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• pp.52-59
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• 2002

Resently, reduction of industrial products in size and weight has increased by the application of micro-drill for gadgets of high precision and gave rise to a great interest in a micro-drilling. Due to the lack of tool stiffness and the chip packing, micro-drilling requires not only the robust tool structure which has not affected by the vibration, but also the effective drilling methods designed to prevent tool fracture from cutting troubles. Firstly, this paper presents a optimum characteristic evaluation method of 0.15mm microdrill in consideration of new manufacturing processes for improving the product rate and extend the tool life, and secondly suggest between microdrilling characteristic properties of tool md evaluation of workpiece quality through experiment.

• International Journal of Railway
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• 제3권2호
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• pp.73-82
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• 2010

Global and local behaviors of a lightly RC shear walls are investigated in this paper. For the sake of cyclic behaviors, nominal ground accelerations of 0.15 g, 0.40 g and 0.55 g which associated with natural periods of the walls are applied as listed in French CAMUS-2000 shake table test. Modified Kent & Park model, Drucker-Prager model for concrete material and $Giufr\acute{e}$-Menegotto-Pinto model for rebar are used for time history analyses using fiber/solids elements respectively. Alternatively, Eulerian beam analysis are discussed by imposing inelastic hinges at the most possible plastic hinge location using modified Takeda's trilinear model with stiffness reduction. Relative displacements, base shears, bending moments of 5-story shear building with 36-tons of mass under bi-lateral seismic excitation are extracted and compared with EC-8, PS-92 and KBC-09 provisions. Multi-scaled degradation process; material damage, elemental fracture and structural failure in turn is discussed in the view of numerical accuracy, efficiency and limitation depending on three different model-based analyses.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.687-694
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• 2002

This paper presents the results of 3-D analysis on steady state flow in the region where the leakage in a cable tunnel is occurred due to high excess ground water pressure. In numerical modeling, a relief well is selected as a method of reduction in water pressure at the surrounding region of the cable tunnel. The distribution of ground water level after dewatering by relief wells is analyzed, Results show that the amount of dewatering level in the layer of hard rock is about 4.2∼8.6m, and that in the layer of fracture zone is about 5.8∼8.2m. The predicted settlement at the cable tunnel due to the increase of effective stress by dewatering is 0.3mm.

• 대한족부족관절학회지
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• 제17권4호
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• pp.257-263
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• 2013

Open reduction and internal fixation is currently considered as a gold standard of treatment in most of the intra-articular calcaneal fractures. Among various different approaches, extensile lateral approach is the most popular since it provides good exposure to the subtalar joint. However, wide skin incision followed by extensive soft tissue dissection leading to increased risk of wound breakdown is the most serious drawback. Sinus tarsi approach, a minimal invasive technique to approach the subtalar joint and reduce the intra-articular calcaneal fractures, provides good clinical outcome and less wound complications compared to the extensile lateral approach. This article introduces the surgical technique and review of the literature regarding the sinus tarsi approach.

• 한국세라믹학회지
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• 제26권3호
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• pp.402-408
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• 1989

$\beta$-Sialon powder was synthesized by the simultaneous reduction and nitridation of the mixed powder of Hadong kaolin and Kimcheon quartzite, using graphite as a reducing agent. The synthesized $\beta$-Sialon powder (Z=1) was hot-pressed at 175$0^{\circ}C$, for 90min under 30MPa in N2 atmosphere, after Yttria and YAG composition material were added as sintering agents. The effects of grain-boundary crystallization on high-temperature mechanical properties of $\beta$-Sialon ceramics were investigated. Strength degradation was observed at above 1,00$0^{\circ}C$ for the $\beta$-Sialon (Z=1)-8wt% Y2O3 composition, but it was not observed up to 1,20$0^{\circ}C$ for the $\beta$-Sialon-8wt% YAG composition which was annealed at 1,40$0^{\circ}C$ for 4 hours in N2 atmosphere. After the $\beta$-Sialon-8wt% YAG composition was annealed, the decrease of fracture toughness was observed.

• Journal of Dental Anesthesia and Pain Medicine
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• 제18권2호
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• pp.115-117
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• 2018

Lingual nerve injury is a rare complication of general anesthesia. The causes of lingual nerve injury following general anesthesia are multifactorial; possible mechanisms may include difficult laryngoscopy, prolonged anterior mandibular displacement, improper placement of the oropharyngeal airway, macroglossia and tongue compression. In this report, we have described a case of bilateral lingual nerve injury that was associated with orotracheal intubation for open reduction and internal fixation of the left distal radius fracture in a 61-year-old woman. In this case, early treatment with dexamethasone effectively aided the recovery of the injured lingual nerve.

• 한국안전학회지
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• 제10권2호
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• pp.120-128
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• 1995

The fatigue failure of rail is a principal source of derailment accidents. The reduction of fatigue failures can be achieved by Intensive track maintenance and periodic safety assessments for the railway. For the safety assessments, it is required to have more accurate knowledge for fatigue behavior such as the crack initiation, propagation, crack growth rate and the remaining service life in rail. In this paper, the mean stress effects for the fatigue behavior of rail steel are studied. For this study, the fatigue test is conducted and some equations for fatigue evaluation are applied and compared. From the results, we can see that the fatigue crack growth rate is the more increased as the men stress Is the more increased, the mean stress effect is represented well by the combination of stress intensity factor range and maximum stress intensity factor and Crooker and Range's equation represented by ${\Delta}K, K_{max}$ is the best fit for fatigue evaluation and safety assessment of rail.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.393-396
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• 2005

This paper is concerned with the drawing process of $Al-1\%Si$ bonding wire. In this study, the finite-element model established in previous work was used to analyze the effect of various forming parameters, which included the reduction in area, the semi-die angle, the aspect ratio, the inter-particle spacing and orientation angle of the fine Si particle in drawing processes. The finite-element results gave the consolidation condition. From the results of analysis, the effects of each forming parameter were determined. It is possible to obtain the Important basic data which can be guaranteed in the fracture prevention of $Al-1\%Si$ wire by using FE-Simulation.