• International Journal of Highway Engineering
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• v.11 no.1
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• pp.165-175
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• 2009

With the current move towards adopting mechanistic-empirical concepts in the design of pavement structures, state-of-the-art mechanistic analysis methodologies are needed to determine accurate pavement responses, such as stress, strain, and deformation. Previous laboratory studies of pavement foundation geomaterials, i.e., unbound granular materials used in base/subbase layers and fine-grained soils of a prepared subgrade, have shown that the resilient responses followed by nonlinear, stress-dependent behavior under repeated wheel loading. This nonlinear behavior is commonly characterized by stress-dependent resilient modulus material models that need to be incorporated into finite element (FE) based mechanistic pavement analysis methods to predict more realistically predict pavement responses for a mechanistic pavement analysis. Developed user material subroutine using aforementioned resilient model with nonlinear solution technique and convergence scheme with proven performance were successfully employed in general-purpose FE program, ABAQUS. This numerical analysis was investigated in predicted critical responses and domain selection with specific mesh generation was implemented to evaluate better prediction of pavement responses. Results obtained from both axisymmetric and three-dimensional (3D) nonlinear FE analyses were compared and remarkable findings were described for nonlinear FE analysis. The UMAT subroutine performance was also validated with the instrumented full scale pavement test section study results from the Federal Aviation Administration's National Airport Pavement Test Facility (FAA's NAPTF).

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.41-48
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• 2022

Generally it was known that member forces in the earthquake resistant design is lower than those in the general design. But it is not true in cases of water treatment underground structures, which is different in each case like water treatment plant, sedimentation basin, and utility-pipe conduit. Also, looking at the scale of earthquakes that have recently occurred in Korea, large-scale earthquakes are frequent, so when the magnitude of the design seismic force increases, it is necessary to investigate the seismic behavior of the water treatment underground structure and to deal with it. In this study the change rate of member forces was investigated by the change of design load factor (earthquake acceleration design criteria), earth depth, underground water level. The pseudo-static analysis and response displacement method was applied, and various analyzes were conducted depending on the ground water and soil depth. The proposed formula in this study will be efficient when the earthquake design code of water treatment underground structures is revised.

• Composites Research
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• v.21 no.5
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• pp.23-30
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• 2008

Stab threats using sharp edged or pointed Instruments could be easily encountered by police officers or soldiers. In this study, the shear thickening fluids (STF) was impregnated into Kevlar fabrics to improve the stab protection and the resistance of STF impregnated Kevlar fabrics was experimentally investigated. The puncture and cut resistance were tested using a drop test machine withspike and knife indenters fabricated based on the National Institute of Justice (NIJ) standard. The STF was filled with spherical $SiO_2$ particles having an average diameter of 100nm, 300nm, and 500nm. The effect of particle size on puncture and cut resistance of STF impregnated Kevlar fabrics was also investigated. The measured impact load histories showed that STF impregnation into fabric leads to withstand higher peak loads than that of neat fabrics under spike test. The test results showed that Kevlar impregnated with STF exhibit remarkable improvements in puncture resistance while it is slightly influential on the cut resistance. Specifically, particle size is the one of the dominant factors controlling fabric resistance to puncture under spike impact test.

• The Journal of Korean Academy of Prosthodontics
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• v.62 no.2
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• pp.146-156
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• 2024

Implant assisted removable partial denture (IARPD) has been practiced in various forms for a long time, and among them, implant surveyed crown RPD is gaining predictability as well as being considered as a treatment option for patients with anatomical and financial disadvantages. The position of implant could be divided as posterior placement or anterior placement according to the purpose of the treatment and should be planned in consider to the alveolar ridge of patient, anticipated prognosis of remaining teeth, and opposing dentition. This case report describes a treatment for mandibular Kennedy class I partial edentulous patient with two implant-supported surveyed crown and implant assisted removable partial denture. Given the difficulty of posterior placement in this patient and the prognosis of the residual teeth, the plan was to place two implants in close proximity to the residual teeth, which were placed in the planned position, angle, and depth using guided surgery. The process of fabricating the fixed prosthesis was carried out in parallel with the maxillary edentulous tooth arrangement process to increase predictability, and when fabricating the localized tooth, the implant was designed in a form that allows the patient to perform functional movements by preventing excessive loading as the last supporting tooth, and was fabricated through a secondary impression process. Each treatment procedure was proceeded as planned, with aesthetically and functionally satisfactory results for both patient and operator.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.5
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• pp.581-596
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• 1999

The purpose of this study was to investigate the stress distribution of the abutment and sup-porting tissues according to the slopes and types of the guiding plane of distal extension removable partial dentures. The 3-dimensional finite element method was used and the finite element models were prepared as follows. Model I : Kratochvil type guiding plane with $90^{\circ}$ to residual ridge Model II : Kratochvil type guiding plane with $95^{\circ}$ to residual ridge Model III : Kratochvil type guiding plane with $100^{\circ}$ to residual ridge Model IV : Krol type guiding plane with $90^{\circ}$ to residual ridge Distal extension partial denture which right mandibular first and second molar were lost was used and the second premolar was prepared as primary abutment with RPI type retainer. Then 150N of compressive force was applied to central fossae of the first and second molars and von Mises stress and displacement were measured. The results were as follows 1. Model I and Model IV showed a similar stress distribution pattern and the stress was concentrated on the apex of the root of the abutment. 2. The stress was increased and concentrated on mesial side of the root of the abutment in Model II. The stress was concentrated on buccal and mesiobuccal side of the root of the abutment in Model IV. 3. In Model I, the root of the abutment displaced and twisted a little in clockwise. In Model IV, the root of the abutment displaced to distolingually at apical region of the root and mesiobuccally at cervical region of the root. 4. In Model II, the root of the abutment displaced to mesiolingually at apical region of the root and more displaced and twisted in counterclockwise at cervical region of the root. In Model III, the root of the abutment displaced to mesiobucally at apical region of the root and more displaced and twisted in clockwise at cervical region of the root.

• The korean journal of orthodontics
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• v.36 no.6
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• pp.412-421
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• 2006

Objective: The result of finite element analysis depends on material properties, structural expression, density of element, and boundar or loading conditions. To represent proper elastic behavior, a finite element model was made using Hounsfield unit (HU) values in CT images. Methods: A 13 year 6 month old male was used as the subject. A 3 dimensional visualizing program, Mimics, was used to build a 3D object from the DICOM file which was acquired from the CT images. Model 1 was established by giving 24 material properties according to HU. Model 2 was constructed by the conventional method which provides 2 material properties. Protraction force of 500g was applied at a 45 degree downward angle from Frankfort horizontal (FH) plane. Results: Model 1 showed a more flexible response on the first premolar region which had more forward and downward movement of the maxillary anterior segment. Maxilla was bent on the sagittal plane and frontal plane. Model 2 revealed less movement in all directions. It moved downward on the anterior part and upward on the posterior part, which is clockwise rotation of the maxilla. Conclusion: These results signify that different outcomes of finite element analysis can occur according to the given material properties and it is recommended to use HU values for more accurate results.