• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.6
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• pp.84-91
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• 1999

The goal of this study is to analyse the stress and the strain occurring within the work piece at the fine-blanking process and hence to assume the size direction and a distribution chart of the shearing stress as the penetration of the punch is being increased trough the application of the FEM. For this analysis we introduced the piece-wise linear method in the non linear structural analysis program for large deformation sheet metal forming and we defined it as the problem of the non linear contact. Therefore we modeled the above problems as quadratic-nodded axi-symmetrical elements for the character-istics of the work piece. From the result of this analysis it was found that the shearing stress is a great deal occurred on the surface of the work piece during the beginning process of the punch penetration and it's effect is expected to influence importantly for the formation of burnish because the deeper is the penetration of the punch in the narrow clearance zone. the greater is the degree of the strain stress.

• Journal of Korean Clinical Health Science
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• v.6 no.1
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• pp.1089-1096
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• 2018

Purpose: To investigate the corneal thickness and anterior chamber depth (ACD) of eyes with Keratoconus in the Korean population with the Pentacam. Methods: The subjects consisted of 84 eyes from Keratoconic adults aged 7-59 years during 2010. The thinnest area, apex zone, and pupil centre of the corneal thickness were measured using the Pentacam pachymetry. ACD value was also measured with Pentacam. Results: There was a statistically significant relationship between thickness of the cornea at the apex area and the pupil centre (p=0.0001). However, there was no statistical difference (p>0.5) in the mean thickness of thinnest area, apex zone, pupil centre of cornea between right eye and left eye. Also, correlation between ACD and corneal thickness in all subjects had no statistical differences (p>0.05) in all subjects. Conclusion: These results suggested that the regional thickness of cornea and ACD with Pentacam can provide correct and useful diagnostic information of the morphology of Keratoconus for the RGP contact lens and diagnosis of abnormal corneal refraction surgery.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.299-304
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• 2001

An approach is developed for parametric investigation of the influence of the surface roughness on thermohydrodynamic analysis with film conditions which systemically occur in journal bearings. A parametric investigation is performed for predicting the bearing behaviors such as pressure and temperature distributions in lubricating films between the stationary and moving surfaces determined by absorbed layers and interfaces on the statistical method for rough surface with Gaussian distribution. The layers expressing the effects of surface roughness are expressed as functions of the standard deviations (${\sigma}$) of each surface and surface orientation (j) to explain the flow patterns between both rough surfaces. The coupled effect of surface roughness and shear zone dependency on hydrodynamic pressure and temperature has been found by solving the present model in non-contact mode and contact mode, respectively.

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.2
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• pp.88-93
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• 1981

The three force components of shear spinning are calculated by a newly proposed deformation model. The spinning process is understooed as shearing deformation arter uniaxial yuelding by ending, and shear stress .tau.$\sub$rz/ becomes .kappa. the yueld limit in pure shear, in the deformation zone. The tangential forces are calculated and then the feed forces and normal foeces are obtained by assuming a nuiform distribution of roller pressure on the contact surface. An optimum contact area is obtaned by minimizing the bending energy required to obtain the assumed deformation mechanism. The calculated forces are compared with experimental data form published literature and present experiments. Good agreement cetween calculated and experimental values for working forces is obtained over a wide range of process variables.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.317-317
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• 2000

The mathematical set-up model was developed to reduce the mechanical property deviation in annealed and slightly rolled steel strip. The mechanical peculiarities of temper rolling process, such as high friction value and non-circular contact arc, Low reduction and non-negligible entry and exit elastic zones as well as central restricted deformation zone are all taken into account. The deformation of work rolls is calculated with the influence function method and arbitrary contact arc shape is permitted. The strip deformation is modeled by slab method and the entry and exit elastic deformation zones are included. The restricted deformation Bone near the neutral point is also considered. It was revealed that the new model has better accuracy than present regression model by statistical analysis with actual mill rolling data.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.507-513
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• 1993

The purpose of this study was to observe the effect of immersion in water at 3, 5, 7, and 10 minutes after mixing on the surface of three regular and one light-curing glass-ionomer cement by measuring penetration of a methylene blue solution. Early solubility of these cements was also measured and compared with that of a zinc phosphate and a polycarboxylate cement. A blue-stained zone was observed in all glass-ionomer cement, but an inner, opaque zone was observed in only two of the regular glass-ionomer cements. Extending the time between start of mixing and immersion on water decreased the width of both zones in all cements and markedly lowered the loss of substance from the surface of regular glass-ionomer cements. However, time after mixing had no or only a limited effect on the loss of substance from the light-curing glass-ionomer cement, the zine phosphate cement, or the polycarboxylate cement.

• Magazine of the Korean Society of Agricultural Engineers
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• v.8 no.1
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• pp.1055-1063
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• 1966

Ground water hydrology may be defined as the science of the occnrrence, distribution, and movement of water below the surface of the earth. Geohydrology has an identical connotation, and hydrogeology differs only by its greater emphasis on geology. Ground water referred to with out further specification is commonly understood to mean water occupying all the voids with in a geologic stratum. This saturated zone is tobe distinguished from an unsaturated, or aeration zone where voids are filled \yith water and air. Water contained in saturate:! zones is important for engineering works, geologic studies, and water supply developements Conseqently, the occurrence of water in these zones will be emphasized here. Un-saturated zones are usualiy found above saturated zones and extending upward to the ground surface. Because this water includes soil moisture with in the root zone, it is a major concern of agricultlre, botmy and soil science. No rigid demarcation of waters, between the two zones is possible, for they possess an iriterdependent boundary and water can move from zone to zone in either science, including eology, hydrology, meteorology, and oceanography are concerned with earths water, but ground water hydrology may be regarded as a specialized science combining elements of geology, hydrology, and fluid mechanics. Geology governs the occurrence and distribution of ground water, hydrology determines the supply of water to the ground, and fluid mechanics explains its movement. To provide maximum development of grofnd water resources. for benefical use requires thinking in terms of an entire ground water basin. In order to inorease the natural supply of ground water, man has attempted to artifially recharge ground water basins. Coastal aquifers come in contact with the ocean at seawater of the coastline. Fresh ground water is discharged in to the ocean. the seaward flow of ground water has been decreased or even reversed, Sea water penettating in land in aquifer.

• Economic and Environmental Geology
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• v.13 no.2
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• pp.104-116
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• 1980

The Ulsan mine is one of the largest contact metasomatic magnetite and scheelite deposits in the southeastern part of Korea. Mineralization at the Ulsan mine is localized along the contact between upper Cretaceous volcanic rocks and age unknown limestone which were intruded by 58 m.y. -old biotite-horndlende granite. General zonal sequence of skarn toward crystalline limestone from limestone-volcanics contact is grandite, grandite-salite and salite zones. On the otherhand volcanics origin skarns exhibits zonal sequences toward hornfels from boundary with limestone is garnet, garnet-epidote, and epidote zone. Compositions of garnets and clinopyro xenes are determined by the X-ray diffraction and reflective indecies. Local brecciation of these early skarns were followed by formation of the later skarn as zoned patches, breccia fillings and cross-cutting veins. Paragenetic sequence of late skarn minerals which is exhibited in the zoned patches and veins is an overlapping progression with time from andradite through hedenbergite or actinolite, quartz to calcite deposition. Magnetite metallization followed early formed skarns and pyrite pyrrhoite, sphalerite, galena, tennantite, scheelite and arsenopyrite deposition were simultaneously with hedenbergite, quartz and calcite of late skarn. Filling temperatures of fluid inclusions in calcites range from $160^{\circ}$ to $280^{\circ}C$.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.465-472
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• 2008

An automotive windshield wiper system is modeled mainly for vibration analysis purpose. The model is composed of solid links, ideal joints, imperfect joints to simulate unavoidable manufacturing defects and bushings having stiffness, contact between a wiper blade and a wind screen glass, friction, a spring and an actuator. Main stream of wiper dynamics analysis has been obtaining a closed form of system of equations using Newton's or Lagrange's formula and doing a numerical simulation study to understand and predict the behavior of it. However, the modeling process is complex since a wiper system is of multibody and a contact problem occurs. When imperfection, such as dead zone of a joint and stiffness of a rubber bushing, should be included, the added complexity makes the modeling difficult. Since the imperfection is understood as main cause of problematic vibration, the dynamics model of a wiper system aiming vibration analysis should include such unavoidable manufacturing defects in the model. An open form of dynamic model of a automotive windshield wiper system with imperfect joints using a commercial software is obtained and a simulation analyssis is conducted for vibration reduction study.

• Structural Engineering and Mechanics
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• v.56 no.2
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• pp.275-291
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• 2015

Adherence between reinforcement and the surrounding concrete is usually ignored in finite element analysis (FEA) of reinforced concrete (RC) members. However, load transition between the reinforcement and surrounding concrete effects RC members' behavior a great deal. In this study, the effects of bond-slip on the FEA of RC members are examined. In the analyses, three types of bond-slip modeling methods (perfect bond, contact elements and spring elements) and three types of reinforcement modeling methods (smeared, one dimensional line and three dimensional solid elements) were used. Bond-slip behavior between the reinforcement and surrounding concrete was simulated with cohesive zone materials (CZM) for the first time. The bond-slip relationship was identified experimentally using a beam bending test as suggested by RILEM. The results obtained from FEA were compared with the results of four RC beams that were tested experimentally. Results showed that, in FE analyses, because of the perfect bond occurrence between the reinforcement and surrounding concrete, unrealistic strains occurred in the longitudinal reinforcement. This situation greatly affected the load deflection relationship because the longitudinal reinforcements dominated the failure mode. In addition to the spring elements, the combination of a bonded contact option with CZM also gave closer results to the experimental models. However, modeling of the bond-slip relationship with a contact element was quite difficult and time consuming. Therefore bond-slip modeling is more suitable with spring elements.