• Journal of Korean Ophthalmic Optics Society
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• v.14 no.3
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• pp.17-27
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• 2009

Purpose: This review article was written to determine the effects of parameters characterizing a hard contact lens (RGP included), such as BCs, diameters, edge angles, on the time interval for tight fitted lens to return to the equilibrium when it was decentered from blinking. Methods: A mathematical formulation was established to relate or calculate the restoring forces and thickness of lacrimal layer beneath the cornea with the various lens parameters when the tight fitted lens was decentered from blinking. Based on this formulation the differential equations and their numerical solution program were set up to describe the time dependence of the lens on the position and to estimate the time for the lens's return to the equilibrium after blink. Results: It is found that the time interval for the tight fitted lens to return to the equilibrium decreases as either the BC decreases or the diameter increases because both the reduction in BC and increase in diameter result in the increase in the lacrimal layer thickness between the lens and cornea increase which yielded the lowering of the viscous friction in the lens motion. As the edge angle of tight fitted lens increases the time for recentering decreases due to the increase in restoring force without change in lacrimal thickness beneath the lens. In the case of flat fitted hard lens (RGP included), the lacrimal layer thickness under the lens increases as either BC or diameter increases which results in reduction in viscous friction so that the time for the lens's return to the equilibrium were to decrease. The edge angle of flat fitted lens does not affect the lens motion. Conclusions: The effect of BCs on the lens motion (time to approach the equilibrium) was concluded to be significant with both tight and flat fitted lens where its results are contrary with each other. The edge angle of lens only affects the motion in tight fitted lenses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.67-75
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• 2019

The diaphragm used for CFT columns has a small amount of steel to be used, but has a disadvantage that welding is difficult and openings are required because the steel tube and four sides must be welded. The improved diaphragm to be examined in this study was cut into four corners by cutting the center hole for concrete filling. In the improved diaphragm, the width of the center hole is the same as that of the previous diaphragm, but the width of the diaphragm contacting the steel tube is reduced, thereby reducing the welding length by about 70% compared to the previous diaphragm. The in-plane strain of each specimen was analyzed when the same load was applied to the interior diaphragm through a simple tensile test. Using the general FEM program(ANSYS 19.2), the analysis was performed under the same conditions as the actual simple tensile test, and the load transfer between the improved diaphragm and the previous diaphragm was compared. When the width of the diaphragm is equal to or smaller than the flange width, stress is concentrated from the end of the diaphragm, and when the flange width is larger, stress is concentrated at the center.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.46-53
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• 2023

In this paper, we evaluated the flexural performance of three types of reinforced concrete beams (SHCC-RB, SHCC-SB, SHCC-FRP) strengthened with ordinary steel rebar, very high strength (super strength) rebar, and FRP bars together with strain-hardening cement composite (SHCC). For this purpose, a series of beam specimens were manufactured and four-point load bending experiments were performed. As a result of the experiment, all specimens strengthened with SHCC exhibited tightly controlled flexural microcrakcs with the crack width of less than 100 ㎛. This is mostly due to the material properties of SHCC showing tensile strain hardening properties with multiple microcracks under uniaxial tension. The specimen SHCC-FRP showed lower initial cracking moment and yield flexural strength than SHCC-RB, whereas the maximum flexural strength of SHCC-FRP was superior to that of SHCC-RC. This is because the tensile strength of FRP bars is higher than that of ordinary steel reabr. The initial cracking moment of the beam specimen SHCC-SB was similar to that of SHCC-RB, but the yield flexural strength and maximum flexural strength of SHCC-SB were evaluated to be the highest.

• Composites Research
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• v.19 no.5
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• pp.20-27
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• 2006

Self-sensing and interfacial evaluation of Ni nanowire/polymer composites were investigated using electro-macromechanical technique, which can be used fur a feasible sensing measurement on tensile and compressive loading/consequent unloading, temperature, and humidity. Mechanical properties of Ni nanowire with different aspect ratio and adding contents in either epoxy or silicone composites were measured indirectly using electro-pullout test under uniform and non-uniform cyclic loadings. Comparing apparent modulus with the conventional mechanical tensile modulus of Ni nanowire/epoxy composites, the trends were consistent with each other. Ni nanowire/epoxy composites showed the sensing response on humidity and temperature. Self-sensing on applied tensile and compressive loading/unloading was also responded for Ni nanowire/silicone composites via electrical contact resistivity showing the opposite trend between tension and compression. It can be due to the different electrically-interconnecting mechanisms of dispersed Ni nanowires embedded in silicone matrix.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.281-290
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• 2009

In this study, an analysis technique of hybrid girder considering nonlinearity of steel-concrete contact surface is presented. Steel-concrete hybrid girder shows partial-interaction behavior due to the deformation of shear connectors, slip and detachment at the interface, and cracks under the applied loads. Therefore, the partial-interaction approach becomes more reasonable. Contact surface is modeled by interface element and analyzed nonlinearly because of cost of time and effort to detailed model and analysis. Steel and Concrete are modeled considering non-linearity of materials. Material property of contact surface is obtained from push-out test and input to interface element. For the constitutive models, Drucker-Prager and smeared cracking model are used for concrete in compression and tension, respectively, and a von-Mises model is used for steel. This analysis technique is verified by comparing it with test results. Using verified analysis technique, various analyses are performed with different parameters such as nonlinear material property of interface element and prestress. The results are compared with linear analysis result and analysis result with the assumption of full-interaction.

• Steel and Composite Structures
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• v.48 no.1
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• pp.43-57
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• 2023

The impacts of waste tire rubber (WTR) on the bending conduct of reinforced concrete beams (RCBs) are investigated in visualization of experimental tests and 3D finite element model (FEM) using both ANSYS and SAP2000. Several WTR rates are used in total 4 various full scale RCBs to observe the impact of WTR rate on the rupture and bending conduct of RCBs. For this purpose, the volumetric ratios (Vf) of WTR were chosen to change to 0%, 2.5%, 5% and 7.5% in the whole concrete. In relation to experimental test consequences, bending and rupture behaviors of the RCBs are observed. The best performance among the beams was observed in the beams with 2.5% WTR. Furthermore, as stated by test consequences, it is noticed that while WTR rate in the RCBs is improved, max. bending in the RCBs rises. For test consequences, it is clearly recognized as WTR rate in the RCB mixture is improved from 0% to 2.5%, deformation value in the RCB remarkably rises from 3.89 cm to 7.69 cm. This consequence is markedly recognized that WTR rates have a favorable result on deformation values in the RCBs. Furthermore, experimental tests are compared to 3D FEM consequences via using ANSYS software. In the ANSYS, special element types are formed and nonlinear multilinear misses plasticity material model and bilinear misses plasticity material model are chosen for concrete and compression and tension elements. As a consequence, it is noticed that each WTR rates in the RCBs mixture have dissimilar bending and rupture impacts on the RCBs. Then, to observe the impacts of WTR rate on the constructions under near-fault ground motions, a reinforced-concrete building was modelled via using SAP2000 software using 3-D model of the construction to complete nonlinear static analysis. Beam, column, steel haunch elements are modeled as nonlinear frame elements. Consequently, the seismic impacts of WTR rate on the lateral motions of each floor are obviously investigated particularly. Considering reduction in weight of structure and capacity of the members with using waste tire rubber, 2.5% of WTR resulted in the best performance while the construction is subjected to near fault earthquakes. Moreover, it is noticeably recognized that WTR rate has opposing influences on the seismic displacement behavior of the RC constructions.

• Composites Research
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• v.36 no.5
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• pp.303-309
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• 2023

In this paper, a Progressive Damage and Failure Analysis (PDFA) modeling method was developed using ABAQUS/EXPLICIT to predict in-plane damage and delamination for Open-Hole Compression (OHC) testing. The proposed PDFA model was constructed based on Hashin criteria and cohesive behavior. The strength and stiffness of OHC specimens with three types of stacking sequences [(45/-45/0₂)₃]_s , [(45/0/-45/90)₃]_s and [45/-45/0/45/-45/90/(45/-45)₂]_s were compared to comprehensively evaluate the validity of the Finite Element(FE) model of PDFA. The strength and stiffness of the OHC specimens were predicted relatively well, with less than a percentage error 10.0 %. For the numerical simulation case for each layup, the damage initiation/evolution of OHC specimens were evaluated for delamination and tension/compression matrix damage before and after failure.

• Korean Journal of Environmental Agriculture
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• v.27 no.2
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• pp.178-184
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• 2008

This work was carried out to investigate the effect of waterlogging on the growth and nutrient contents of 'Campbell Early' and 'Kyoho' grapevines under the vinyl house condition from June 14 to July 20, 2005. For the trial, seedlings of two-year-old grapevine were transplanted to 40 L pot with a sandy loam soil. Irrigation point of non-waterlogging(control) treatment was controlled at -40 kPa of soil water tension using tensiometer and waterlogging treatments were imposed for 35 days at the water levels of above 10 cm from the soil surface using tap water. The growth of aerial(shoot length, leaf number and stem diameter) and underground(root) parts of 'Campbell Early' and 'Kyoho' grapevines tended to be wholly reduced by waterlogging, while the growth of aerial parts were more severely impaired in 'Kyoho' than in 'Campbell Early' cultivar. The different responses for waterlogging between two grapevines seem to be related with the capacity for absorbing mineral nutrients, because nitrogen content of 'Campbell Early' cultivar leaves was significantly higher than that of 'Kyoho' cultivar although the contents of phosphorus and potassium in leaves of two grapevine cultivars were similarly declined. There was no significant different of fruit quality, such as contents of soluble solid, titratable acidity and weight of berry in 'Campbell Early' between waterlogging and control. In 'Kyoho' cultivar, however, berry weight and titratable acidity were decreased and soluble solid content was increased by waterlogging. It was assumed that waterlogging stress for grapevines promotes maturation and coloring processes of berries by stimulating maturation hormone such as ethylene. In conclusion, 'Campbell Early' cultivar seems to be more tolerable than 'Kyoho' cultivar when comparing the growth responses and nutrient contents between two grapevine cultivars under waterlogging.

• The Journal of Internal Korean Medicine
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• v.28 no.1
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• pp.47-67
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• 2007

Objectives : This study was aimed to investigated the warning signs and its relationship with the other characteristics in acute stroke patients. Methods : 225 acute stroke patients were recruited at the Department of Cardiovascular and Neurologic Diseases (Stroke Center) of Kyung Hee University Oriental Hospital from October 2005 to September 2006. We evaluated their stroke type with brain MRI, their warning signs, and general characteristics such as age, sex, past history, risk factors, etc. Results : 225 subjects were included in the final analysis. In the subjects' general characteristics, the most common etiology of stroke was small vessel occlusion. In the assessment of the subjects' warning signs, the frequency of tension felt at the cervical area was highest followed by blepharospasm, sensory dysfunction (one side of numbness, tingling sensation, dead sensation), one side paralysis or weakness, etc. After analyzing etiology, cerebral hemorrhage had more facial spasm sign and hypertension than cerebral infarction. On the other hand, cerebral infarction had more diabetes and sensory dysfunction (one side of numbness, tingling sensation, dead sensation) than cerebral hemorrhage. Among stroke locations, subjects with their brain lesion in the cortex had more warning sings of motor dysfunction such as one side paralysis, or weakness. Multiple lesions showed a close relationship with smoking habit and were more common in males than in females. The under 65 years old group were more commonly associated with alcohol consumption, accidental mental stress and blepharospam than the over 65 years old group. In the group of under 65 years old, males more commonly had lesions in occipital lobe, alcohol consumption and smoking habit than females. Otherwise, females more commonly had vision dysfunction and blepharospasm than males. In the group of over 65 years old, males more commonly had cortex lesion than females. On the other hand, Females more commonly had accidental mental stress than males. Conclusions : We observed various warning signs and their distribution in acute stroke patients. The subjects' brainlesions and their etiology seemed to affect the features of the warning signs. Hypertension, diabetes and hyperlipidemia were also related to etiology of stroke and some habitual problems such as smoking and drinking seemed to reduce the age of stroke ictus. Although a concrete conclusion can hardly be drawn from this study, it reminds physicians of the importance of warning signs which appear among their patients.

• Restorative Dentistry and Endodontics
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• v.34 no.5
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• pp.424-429
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• 2009

This study aimed to assess the influence of different cross-sectional area on the cyclic fatigue fracture of Ni-Ti rotary files using a fatigue tester incorporating cyclical axial movement. Six brands of Ni-Ti rotary files (ISO 30 size with. 04 taper) of 10 each were tested: Alpha system (KOMET), HeroShaper (MicroMega), K3 (SybronEndo), Mtwo (VDW), NRT (Mani), and ProFile (Dentsply). A fatigue-tester (Denbotix) was designed to allow cyclic tension and compressive stress on the tip of the instrument. Each file was mounted on a torque controlled motor (Aseptico) using a 1:20 reduction contra-angle and was rotated at 300 rpm with a continuous, 6 mm axial oscillating motion inside an artificial steel canal. The canal had a $60^{\circ}$ angle and a 5 mm radius of curvature. Instrument fracture was visually detected and the time until fracture was recorded by a digital stop watch. The data were analyzed statistically. Fractographic analysis of all fractured surfaces was performed to determine the fracture modes using a scanning electron microscope. Cross-sectional area at 3 mm from the tip of 3 unused Ni-Ti instruments for each group was calculated using Image-Pro Plus (Imagej 1.34n, NIH). Results showed that NRT and ProFile had significantly longer time to fracture compared to the other groups (p < .05). The cross-sectional area was not significantly associated with fatigue resistance. Fractographycally, all fractured surfaces demonstrated a combination of ductile and brittle fracture. In conclusion, there was no significant relationship between fatigue resistance and the cross-sectional area of Ni-Ti instruments under experimental conditions.