• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.21 no.1
• /
• pp.43-50
• /
• 2008

The analysis and results of flexural behavior for steel composite beam with built-up cross-section considering bolt deformation are presented in this paper. The bolt deformation and the restrict effect due to bolt-connection and friction are considered to investigate the flexural behavior of steel composite beam. Nonlinear spring element in ABAQUS is used to consider bolt deformation, also the results are compared with those in case bolt deformations are ignored. The displacement, bending stresses and shear stresses are calculated by F.E. model, and these results are compared with the analytical value of no interaction beam, partial interaction beam and full interaction beam. As a result of analysis, the behavior of composite beam is more dependant on the composite rate than the friction of the steel. When the composite rate is more than 50%, the behavior of composite beam considering the effects of bolt deformation is similar to that of fully composite beam.

• The Journal of Advanced Prosthodontics
• /
• v.7 no.2
• /
• pp.146-150
• /
• 2015

PURPOSE. This in vitro study aimed to compare the failure load and failure characteristics of two different zirconia framework designs of premolar crowns when subjected to static loading. MATERIALS AND METHODS. Two types of zirconia frameworks, conventional 0.5 mm even thickness framework design (EV) and 0.8 mm cutback of full contour crown anatomy design (CB), were made for 10 samples each. The veneer porcelain was added on under polycarbonate shell crown made by vacuum of full contour crown to obtain the same total thickness of the experiment crowns. The crowns were cemented onto the Cobalt-Chromium die. The dies were tilted 45 degrees from the vertical plane to obtain the shear force to the cusp when loading. All crowns were loaded at the lingual incline of the buccal cusp until fracture using a universal testing machine with cross-head speed 0.5 mm/min. The load to fracture values (N) was recorded and statistically analyzed by independent sample t-test. RESULTS. The mean and standard deviations of the failure load were $1,170.1{\pm}90.9$ N for EV design and $1,450.4{\pm}175.7$ N for CB design. A significant difference in the compressive failure load was found (P<.05). For the failure characteristic, the EV design was found only cohesive failures within veneering porcelain, while the CB design found more failures through the zirconia framework (8 from 10 samples). CONCLUSION. There was a significant difference in the failure load between two designs, and the design of the framework influences failure characteristic of zirconia crown.

• The Journal of the Acoustical Society of Korea
• /
• v.24 no.5
• /
• pp.282-293
• /
• 2005

Sonoelastography is an ultrasound-based technique that visualizes the elastic properties of soft tissues by measuring the tissue motion generated by an externally applied vibration. In this paper. the characteristics of wave generation in soft tissues due to an acoustic vibrator are studied. The effects of modal patterns on the detectability of lesions such as tumors in senoelastography are also investigated These are accomplished by analyzing the vibration patterns calculated using theoretical equations and finite element methods in halt space, infinite plate. and finite-sized tissue. A finite-width source generates shear waves with large amplitude Propagating in specific directions. and the generation characteristics depend both on the width and frequency of the vibrator. as well as the distance from it. It is shown in a finite-sized tissue that the lesion detection in displacement images is quit dependent on the modal patterns inside tissue. In contrast it Is also found that the lesion detectability in strain images is less dependent on the modal Patterns and is much better than that in displacement images.

• Structural Engineering and Mechanics
• /
• v.31 no.4
• /
• pp.453-475
• /
• 2009

The literature regarding the free vibration analysis of Bernoulli-Euler and Timoshenko beams on elastic soil is plenty, but the free vibration analysis of Reddy-Bickford beams on elastic soil with/without axial force effect using the Differential Transform Method (DTM) has not been investigated by any of the studies in open literature so far. In this study, the free vibration analysis of axially loaded Reddy-Bickford beam on elastic soil is carried out by using DTM. The model has six degrees of freedom at the two ends, one transverse displacement and two rotations, and the end forces are a shear force and two end moments in this study. The governing differential equations of motion of the rectangular beam in free vibration are derived using Hamilton's principle and considering rotatory inertia. Parameters for the relative stiffness, stiffness ratio and nondimensionalized multiplication factor for the axial compressive force are incorporated into the equations of motion in order to investigate their effects on the natural frequencies. At first, the terms are found directly from the analytical solutions of the differential equations that describe the deformations of the cross-section according to the high-order theory. After the analytical solution, an efficient and easy mathematical technique called DTM is used to solve the governing differential equations of the motion. The calculated natural frequencies of one end fixed and the other end simply supported Reddy-Bickford beam on elastic soil using DTM are tabulated in several tables and figures and are compared with the results of the analytical solution where a very good agreement is observed and the mode shapes are presented in graphs.

• Korean Journal of Materials Research
• /
• v.24 no.1
• /
• pp.60-65
• /
• 2014

Fe-based amorphous coatings were fabricated on a soda-lime glass substrate by the vacuum kinetic spray method. The effect of the gas flow rate, which determines particle velocity, on the deposition behavior of the particle and microstructure of the resultant films was investigated. The as-fabricated microstructure of the film was studied by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). Although the activation energy for transformation from the amorphous phase to crystalline phase was lowered by severe plastic deformation and particle fracturing under a high strain rate, the crystalline phases could not be found in the coating layer. Incompletely fractured and small fragments 100~300 nm in size, which are smaller than initial feedstock material, were found on the coating surface and inside of the coating. Also, some pores and voids occurred between particle-particle interfaces. In the case of brittle Fe-based amorphous alloy, particles fail in fragmentation fracture mode through initiation and propagation of the numerous small cracks rather than shear fracture mode under compressive stress. It could be deduced that amorphous alloy underwent particle fracturing in a vacuum kinetic spray process. Also, it is considered that surface energy caused by the formation of new surfaces and friction energy contributed to the bonding of fragments.

• Elastomers and Composites
• /
• v.47 no.4
• /
• pp.310-317
• /
• 2012

A jute fiber surface was modified with argon gas in a cylinder type RF plasma generator to enhance the interfacial bond strength and to optimize the plasma treatment condition. The plasma power, gas pressure, and treat time were varied to figure out any effect of those parameters on the morphology and mechanical strength of jute fibers, and the interfacial bond strength for a model composite with polypropylene resin. As the severity of plasma treatment was increased, the surface of jute fibers became rougher. Gas pressure was less effective in roughening of the surface compared with those of treat time and plasma power. Approximately 25% drop in tensile strength of jute fibers was observed for the parameters of treat time and plasma power, while little deterioration was found for gas pressure, with increasing the severity. Based on the interfacial shear strength (IFSS), the optimum plasma treatment condition was determined to be treat time of 30 s, plasma power of 40 W, and gas pressure of 30 mTorr.

• Journal of Ginseng Research
• /
• v.19 no.1
• /
• pp.62-72
• /
• 1995

During the controlled atmosphere storage (CA), fresh ginseng showed good appearance in quality, and other deterioration of freshness was not observed until 12 weeks. On the other hand, MA storage had kept freshness only in treatment of 1 until 8 weeks. There was no significant difference between treated and non-treated sample with preservatives, and not treated sample was not infected with various different fungi. Moisture contents and hardness of ginseng in all treatments were not changed much until 12 weeks, and surface shrinkage did not occur either. But shear stress increased somewhat in all treatments after 12 weeks. The granule of microstructure in tissue diminished slightly. The apparent Quality of red ginseng was good until 4 weeks of treatment. But as time passed, white skin and wrinkled skin were generated and darkened in its color. B-1 in CA and E-1 in MA were found to be the most favorable one. The content of crude saponin did not change significantly during storage of CA or MA by preservation conditions and period. Though a small increase in saponin content from 4.92% to 5.43% was recognized in B-1, which was treated with preservative and 6.0% In B-2, control, this could rather explain increment of soluble component by butanol. Thus, there was no change in total contents of ginsenoside pattern and composition of each content. The Rbl content in B-1 and B-2 were 0.98%, and 0.97%, respectively, whereas that of control was 0.96%. E-1 of MA, treated with preservative was 5.32% after 12 weeks, but was 5.73% in control, indicating that ginsenosides pattern was quite similar to that of CA storage.

• Journal of the Korean Magnetics Society
• /
• v.8 no.5
• /
• pp.275-281
• /
• 1998

Effects of coupling agents on the rheological and magnetic properties of plastic ferrite magnets were investigated. Magnetic powder used was Sr-ferrite, and binder used was polypropylene (PP), and coupling agents used were ${\gamma}$-methacryloxypropyl trimethoxy silane (A174) and isopropyl triisostearoyl titanate (TTS). It was found that the addition of coupling agents to the PP/ferrite system reduced the melt viscosity and increased the magnetic properties considerably, and the treatment with TTS showed greater effect than A174 did. By comparison with that of the untreated one, the apparent viscosities of the mixtures treated with A174 and TTS decreased 23 % and 50%, respectively, at the shear rate of $1280\; sec^{-1}$ . Untreated plastic magnets showed remanent flux density $(B_r)$ of 1.89 kG and maximum energy energy product $(BH_{max})$ of 0.84 MGOe, and A174 treated magnets showed of Br 2.25 Kg and $BH_{max}$ of 1.23 MGOe. TTS treated magnets showed $B_r$ of 2.35 kG and $BH_{max}$ of 1.33 MGOe.

• Korean Journal of Medicinal Crop Science
• /
• v.17 no.6
• /
• pp.379-387
• /
• 2009

The aim of this investigation was to examine the influence of extrusion on dietary fiber profile and the content of bioactive compounds, rutin and quercetin in young sprout, whole seed, and matured stem of Tartary buckwheat. WSI(water soluble index) is increased by a function of both screw profile and process temperature, compared to control in different parts of Buckwheat. Also, WSI of ME is increased more than 5.2 times in grain, compared to that of control. The effect of precooking by extrusion on the dietary fiber profile of buckwheat flour was evaluated. Precooking by extrusion significantly increased SDF in flour, although in most cases extrusion decrease in TDF a little. The thermo-mechanical treatment undergone by the buckwheat flour during extrusion led to redistribute part IDF fraction to SDF, leading to an increase in the latter. The content of rutin was increased about two fold in extruded flour of sprout, compared to in control. This increase maybe why these compounds are released from cell wall by high shear processing under high temperature.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.12
• /
• pp.59-69
• /
• 2015

This study examined the magnitude and distribution of earth pressure on the support system in a jointed rock mass due to the different joint sets as well as varying the rock type and joint condition (joint shear strength and joint inclination angle). Based on a physical model test and its numerical simulation, a series of numerical parametric analyses were conducted using a discrete element method. The results showed that the induced earth pressure was affected significantly by a joint set depending on the inclusion of the joint inclination angle, which induces a joint sliding condition, but the number of joint sets alone was not important, even though the earth pressure could be increased slightly as the number of joint sets is increased. In addition, the study results were compared with Peck's earth pressure for soil ground, which indicated that the earth pressure in a jointed rock mass could be considerably different from that in soil ground. The study suggests that the effects of joint sets as well as rock type and joint condition are important factors affecting the earth pressure in a jointed rock mass and they should be considered when designing a support system in a jointed rock mass.