• The Journal of Korean Academy of Prosthodontics
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• v.42 no.4
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• pp.356-372
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• 2004

Statement of problom: In the internal connection system the loading transfer mechanism within the inner surface of the implant and also the stress distribution occuring to the mandible can be changed according to the abutment form. Therefore it is thought to be imperative to study the difference of the stress distribution occuring at the mandible according to the abutment form. Purpose: The purpose of this study was to assess the loading distributing characteristics of 3 implant systems with internal connection under vertical and inclined loading using finite element analysis. Material and method: Three finite element models were designed according to the type of internal connection of ITI(model 1), Friadent(model 2), and Bicon(model 3) respectively. This study simulated loads of 200N in a vertical direction (A), a $15^{\circ}$ inward inclined direction (B), and a $30^{\circ}$ outward inclined direction (C). Result: The following results have been made based on this numeric simulations. 1. The greatest stress showed in the loading condition C of the inclined load with outside point from the centric cusp tip. 2. Without regard to the loading condition, the magnitudes of the stresses taken at the supporting bone, the implant fixture, and the abutment were greater in the order of model 2, model 1, and model 3. 3. Without regard to the loading condition, greater stress was concentrated at the cortical bone contacting the upper part of the implant fixture, and lower stress was taken at the cancellous bone. 4. The stress of the implant fixture was usually widely distributed along the inner surface of the implant fixture contacting the abutment post. 5. The stress distribution pattern of the abutment showed that the great stress was usually concentrated at the neck of the abutment and the abutment post, and the stress was also distributed toward the lower part of the abutment post in case of the loading condition B, C of the inclined load. 6. In case of the loading condition B, C of the inclined load, the maximum von Misess stress at the whole was taken at the implant fixture both in the model 1 and model 2, and at the abutment in the model 3. 7. The stress was inclined to be distributed from abutment post to fixture in case of the internal connection system. Conclusion: The internal connection system of the implant and the abutment connection methods, the stress-induced pattern at the supporting bone, the implant fixture, and the abutment according to the abutment connection form had differenence among them, and the stress distribution pattern usually had a widely distributed tendency along the inner surface of the implant fixture contacting the a butment post.

• Journal of muscle and joint health
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• v.6 no.1
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• pp.100-135
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• 1999

Typical symptoms of rheumatic disease affect overall daily living and cause severe stress. Individuals afflicted with rheumatic disease have many illness-related stresses. Pain was the predominantly perceived stress followed by limitation in mobility, difficulties in carrying out activities of daily living. helplessness, dependency on others, threat to self-esteem, interference in social activity, interference in family relationships. difficulties performing at work, and discomfort of the treatment. Patients with chronic arthritis are subjected to long periods of continuous stress, which may require the management by the health care provider. In these cases, the purpose of the nursing is helping to promote health through supporting patient's coping. Therefore, for the nursing intervention to be effective, it is critical to build a theoretical framework that describes stress-coping for chronic arthritis. Thus, the purpose of this dissertation is to present a theoretical framework which describes the stress-coping processes and to empirically test pathos of this framework for the people with chronic arthritis. The foundation upon which this framework is built in the Erickson, Tomlin, and Swain(1983) theory of Modeling and role-Modeling. The subjects were 275 patients with rheumatoid arthritis or osteoarthritis who visited the outpatient clinic. A hypothetical model of stress-coping was tested by covariance structure analysis with PC-LISREL 8.12 program. As a result, the overall fit was good(Chi-square=94.49, P=0.00, RMR=0.067, GFI=0.95, AGFI=0.91, NNFI=0.93, NFI=0.91) for the hypothetical model. The results of hypothesis testing were as follows : Basic need satisfaction had a statistically significant influence on illness-related experience, emotional stress and coping resources. Internal health locus of control had a statistically significant influence on coping resources. However, independent variables(basic need satisfaction, internal health locus of control, illness-related experience, emotional stress and coping resource) did not have significantly influence on coping. And then, the hypothetical model was modified by considering both the theoretical implication and statistical significance of the parameter estimates. The revised model had a better fit to the data(Chi-square=83.11(P=0.00), RMR=0.061, GFI=0.96, AGFI=0.92, NNFI=0.95, NFI=0.92). Hypothesis emerged from the revised model was tested. The results of hypothesis testing were as follows : Basic need satisfaction had a statistically significant influence on illness-related experience, emotional stress and coping resources. Internal health locus of control had a statistically significant influence on illness-related experience and coping resources. Internal health locus of control, illness-related experience, emotional stress and coping resources had a significantly influence on coping. According to the results of this dissertation, basic need satisfaction and internal health locus of control play a central role in appraisal of illness-related experience and coping resources. And illness related-experience, emotional stress, and coping resources affect on coping activities. In summary, nursing interventions to enhance basic need satisfaction and internal health locus of control will decrease illness related experience and emotional stress and increase coping resources. Increased coping resources will prompt coping activities.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.2
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• pp.385-402
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• 1996

The purpose of this study was to analyze how the stability of the implant prostheses and the loosening of the fastening screw was affected when the various types of Hex structure provided for the effect of anti-rotation of the single prostheses were given. Three dimensional finite element model was designed with which the implants with the external hex type of 0.75mm, 1.5mm and the implant with the internal hex type of 0.75mm, 1.5mm and the implant with the external hex type of $15^{\circ}$ tapered shape of 0.75mm were supposed to completely osseointegrate to the mandible. After fininshing the finite element model, the preload of 10N at the fastening screw was applied and then the vertical and $30^{\circ}$ lateral load of 200N was applied respectively at the cusp tips of the prostheses. The following results were obtained : 1. In case of displacement, the amount of displacement was increased at the internal hex type(model C, D) than at the external hex type(model A, B, E) when the vertical and lateral load was applied. 2. Less equivalent stress was represented at the model B with increased external hex height than at the model A when the vertical and lateral load was applied. 3. Much stress was represented at the model E with increased hex angle than at the model A in case of the stress happened to the implant body and the fastening screw when the vertical and lateral load was applied. 4. Much equivalent stress was represented at the model D with deepened internal hex height than at the model C when vertical and lateral load was applied. 5. The least stress was taken at the model B and the most stress was taken at the model D in case of the stress happened to the implant when the vertical and lateral load was applied. 6. The least stress was taken at the model C at the vertical load. And the least stress was taken at the model B at lateral load in case of the stress happened to the fastening screw. As a results of this study, the good lateral stability of prostheses and less stress of the component of implant was taken when the external hex height was increased, and the risk of neck fracture of implant and fastening screw was increased when the internal hex height was deepned because of long screw neck portion and thin implant neck portion.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.544-561
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• 2005

Purpose : This study was to assess the loading distributing characteristics of implant systems with internal connection or external connection under vertical and inclined loading using finite element analysis. Materials and methods : Two finite element models were designed according to type of internal connection or external connection The crown for mandibular first molar was made using cemented abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the centric cusp tip in a 15$^{\circ}$ inward inclined direction (loading condition B), or 200N at the centric cusp tip in a 30$^{\circ}$ outward inclined direction (loading condition C) respectively. Von Mises stresses were recorded and compared in the supporting bone, fixture, abutment and abutment screw. Results : 1. In comparison with the whole stress or the model 1 and model 2, the stress pattern was shown through th contact of the abutment and the implant fixture in the model 1, while the stress pattern was shown through the abutment screw mainly in the model 2. 2. Without regard to the loading condition, greater stress was taken at the cortical bone, and lower stress was taken at the cancellous bone. The stress taken at the cortical bone was greater at the model 1 than at the model 2, but the stress taken at the cortical bone was much less than the stress taken at the abutment, the implant fixture, and the abutment screw in case of both model 1 and model 2. 3. Without regard to the loading condition, the stress pattern of the abutment was greater at the model 1 than at the model 2. 4. In comparison with the stress distribution of model 1 and model 2, the maximum stress was taken at the abutment in the model 1. while the maximum stress was taken at the abutment screw in the model 2. 5. The magnitude of the maximum stress taken at the supporting bone, the implant fixture, the abutment, and the abutment screw was greater in the order of loading condition A, B and C. Conclusion : The stress distribution pattern of the internal connection system was mostly distributed widely to the lower part along the inner surface of the implant fixture contacting the abutment core through its contact portion because of the intimate contact of the abutment and the implant fixture and so the less stress was taken at the abutment screw, while the abutment screw can be the weakest portion clinically because the greater stress was taken at the abutment screw in case of the external connection system, and therefore the further clinical study about this problem is needed.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.168-173
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• 2004

Microforming can be a good application for bulk metallic glasses. It is important to simulate the deformation behaviour of the bulk metallic glasses in a supercooled liquid region for manufacturing micromachine parts. For these purposes, a correct constitutive model which can reproduce viscosity results is essential for good predicting capability. In this paper, we studied deformation behaviour of the bulk metallic glasses using the finite element method in conjunction with the fictive stress constitutive model which can describe non-Newtonian as well as Newtonian behaviour. A combination of kinetic equation which describes the mechanical response of the bulk metallic glasses at a given temperature and evolution equations fur internal variables provide the constitutive equation of the fictive stress model. The internal variables are associated with fictive stress and relation time. The model has a modular structure and can be adjusted to describe a particular type of microforming process. Implementation of the model into the MARC software has shown its versatility and good predictive capability.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.2
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• pp.123-129
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• 1983

The effect of the micro-internal stress which is induced in the ferrite grain by plastic constraint, on fracture behavior was investigated. The specimen used has combined microstructure with matrix of ferrite encapsulated by second phase of martensite. The micro-internal stress in the ferrite grain was estimated using a simple mechanical model, and its effect on micro and macro fracture behaviors was discussed. The results obtained are summarized as follows; The micro-internal stress promotes the formation of cleavage cracks in the ferrite during deformation. Consequently, it was concluded that the internal stress is one of the significant factors which cause the fracture ductility to decrease.

• Computers and Concrete
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• v.33 no.3
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• pp.309-324
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• 2024

Internal curing, a widely used method for mitigating early-age shrinkage in concrete, also offers notable advantages for concrete durability. This paper explores the potential of internal curing by partial replacement of sand with fine lightweight aggregate for enhancing the behavior of high-performance concrete at elevated temperatures. Such a technique may prove economical and safe for the construction of skyscrapers, where explosive spalling of high-performance concrete in fire is a potential hazard. To reach this aim, the physico-mechanical features of internally cured high-strength concrete specimens, including mass loss, compressive strength, strain at peak stress, modulus of elasticity, stress-strain curve, toughness, and flexural strength, were investigated under different temperature exposures; and to predict some of these mechanical properties, a number of equations were proposed. Based on the experimental results, an advanced stress-strain model was proposed for internally cured high-performance concrete at different temperature levels, the results of which agreed well with the test data. It was observed that the replacement of 10% of sand with pre-wetted fine lightweight expanded clay aggregate (LECA) not only did not reduce the compressive strength at ambient temperature, but also prevented explosive spalling and could retain 20% of its ambient compressive strength after heating up to 800℃. It was then concluded that internal curing is an excellent method to enhance the performance of high-strength concrete at elevated temperatures.

• Korean Journal of Applied Biomechanics
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• v.19 no.2
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• pp.197-204
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• 2009

It bas been hypothesized that foot ulceration might be internally initiated. Current instruments which merely allow superficial estimate of plantar loading acting on the foot, severely limit the scope of many biomechanical/clinical studies on this issue. Recent studies have suggested that peak plantar pressure may be only 65% specific for the development of ulceration. These limitations are at least partially due to surface pressures not being representative of the complex mechanical stress developed inside the subcutaneous plantar soft-tissue, which are potentially more relevant for tissue breakdown. This study established a three-dimensional and nonlinear finite element model of a human foot complex with comprehensive skeletal and soft-tissue components capable of predicting both the external and internal stresses and deformations of the foot. The model was validated by experimental data of subject-specific plantar foot pressure measures. The stress analysis indicated the internal stresses doses were site-dependent and the observation found a change between 1.5 to 4.5 times the external stresses on the foot plantar surface. The results yielded insights into the internal loading conditions of the plantar soft-tissue, which is important in enhancing our knowledge on the causes of foot ulceration and related stress-induced tissue breakdown in diabetic foot.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.171-172
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• 2006

Most existing studies for stress analysis of teeth have employed small number of teeth, and used big element size using F-E models. Therefore, the results are not accuracy enough for showing the internal stress variation. 15 males' and 13 females' mandibular first premolar are employed for internal structure's study of teeth and small element size for a FE model are used. According to these processes, stress distribution of internal parts of teeth are well shown, and the stresses are varied a lot between enamel layer and dentine layer, but there is little variation on pulp chamber.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.318-321
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• 2009

Transformation plasticity is that when a phase transformation of ferrous or non-ferrous alloys progresses even under an extremely small applied stress compared with a yield stress of the material, a permanent deformation occurs. One of widely accepted description for the transformation was proposed by Greenwood and Johnson [1]. Their description is based on an assumption that a weaker phase of an ideal plastic material could deform plastically to accommodate the externally applied stress and the internal stress caused by the volumetric change accompanying the phase transformation. In this study, an implicit finite element model was developed to simulate the deformation behavior of a low carbon steel during phase transformation. The finite element model was coupled with a phase field model, which could simulate the kinetics for ferrite to austenite transformation of the steel. The thermo-elasto-plastic constitutive equation for each phase was adopted to confirm the weaker phase yielding, which was proposed by Greenwood and Johnson [1]. From the simulation, the origin of the transformation plasticity was quantitatively discussed comparing with the other descriptions of it.