• The Journal of Advanced Prosthodontics
• /
• v.6 no.4
• /
• pp.253-258
• /
• 2014

PURPOSE. To compare marginal and internal gaps of zirconia substructure of single crowns with those of three-unit fixed dental prostheses. MATERIALS AND METHODS. Standardized Co-Cr alloy simulated second premolar and second molar abutments were fabricated and subsequently duplicated into type-III dental stone for working casts. After that, all zirconia substructures were made using $Lava^{TM}$ system. Marginal and internal gaps were measured in 2 planes (mesial-distal plane and buccal-palatal plane) at 5 locations: marginal opening (MO), chamfer area (CA), axial wall (AW), cusp tip (CT) and mid-occlusal (OA) using Replica technique. RESULTS. There were significant differences between gaps at all locations. The $mean{\pm}SD$ of marginal gap in premolar was $43.6{\pm}0.4{\mu}m$ and $46.5{\pm}0.5{\mu}m$ for single crown and 3-unit bridge substructure respectively. For molar substructure the $mean{\pm}SD$ of marginal gap was $48.5{\pm}0.4{\mu}m$ and $52.6{\pm}0.4{\mu}m$ for single crown and 3-unit bridge respectively. The largest gaps were found at the occlusal area, which was $150.5{\pm}0.5{\mu}m$ and $154.5{\pm}0.4{\mu}m$ for single and 3-unit bridge premolar substructures respectively and $146.5{\pm}0.4{\mu}m$ and $211.5{\pm}0.4{\mu}m$ for single and 3-unit bridge molar substructure respectively. CONCLUSION. Independent-samples t-test showed significant differences of gap in zirconia substructure between single crowns and three-unit bridge (P<.001). Therefore, the span length has the effect on the fit of zirconia substructure that is fabricated using CAD/CAM technique especially at the occlusal area.

• Journal of Astronomy and Space Sciences
• /
• v.22 no.4
• /
• pp.363-376
• /
• 2005

To study the effects of giant population on dynamical substructures of the central region of NGC 7006, we examine the radial variations of ellipticity and position angle on By stellar photometry using ellipse fitting technique. Total variations of ellipticity and position angle lie in the range $0.02\~0.06\;and\;-10^{\circ}+90^{\circ}$, respectively, from the center out to three times the half light radius. Our ellipse fitting results, after removing giant populations, show that the apparent central dynamical substructures of NGC 7006 are mainly affected by red giant, horizontal branch stars. On the contrary, the contribution of light from subgiant stars to the inner dynamical substructure seems to be insignificant.

• Structural Engineering and Mechanics
• /
• v.4 no.5
• /
• pp.553-568
• /
• 1996

Finite element stiffness matrix methods are presented for finding natural frequencies (or buckling loads) and modes of repetitive structures. The usual approximate finite element formulations are included, but more relevantly they also permit the use of 'exact finite elements', which account for distributed mass exactly by solving appropriate differential equations. A transcendental eigenvalue problem results, for which all the natural frequencies are found with certainty. The calculations are performed for a single repeating portion of a rotationally or linearly (in one, two or three directions) repetitive structure. The emphasis is on rotational periodicity, for which principal advantages include: any repeating portions can be connected together, not just adjacent ones; nodes can lie on, and members along, the axis of rotational periodicity; complex arithmetic is used for brevity of presentation and speed of computation; two types of rotationally periodic substructures can be used in a multi-level manner; multi-level non-periodic substructuring is permitted within the repeating portions of parent rotationally periodic structures or substructures and; all the substructuring is exact, i.e., the same answers are obtained whether or not substructuring is used. Numerical results are given for a rotationally periodic structure by using exact finite elements and two levels of rotationally periodic substructures. The solution time is about 500 times faster than if none of the rotational periodicity had been used. The solution time would have been about ten times faster still if the software used had included all the substructuring features presented.

• Journal of the Korean Society for Railway
• /
• v.9 no.1 s.32
• /
• pp.118-124
• /
• 2006

SThe rigidities of bridge substructures are the important data in the rail-bridge interaction analysis in Korean High -Speed Railway. This experimental study is being performed because of followings. 1) More correct longitudinal stiffness of the structure including substructure should be considered in the calculation of stresses in rails. 2) There are many uncertainties in the design and construction of the piers and foundations. 3) Actual guideline for the rigidities of piers and foundations in the design is necessary. 4) Measurement on the rigidity of pier according to the types of piers, foundations and soil-conditions is needed. Curve for estimating the total rigidity of substructure will be obtained through this and further experimental studies. It may be used in the analysis of Korean High-Speed Railway bridge and then, longitudinal stresses in the rails can be estimated more accurately. One pair of piers, which consist of pot-bearing for fixed support and pad-bearing for movable support, are loaded by steel frame devices with steel wire ropes and hydraulic jack. The responses which are measured at each loading stages in those field tests are displacements and tilted angles on the top and bottom of piers. This study is being performed testing and analysis about several piers in the construction field.

• Structural Engineering and Mechanics
• /
• v.11 no.1
• /
• pp.35-48
• /
• 2001

The objective of this study is to investigate the stability behavior of steel cable-stayed bridges by comparing the buckling loads obtained by means of finite element methods with eigen-solver. In recent days, cable-stayed bridges dramatically attract engineers' attention due to their structural characteristics and aesthetics. They require a number of design parameters and present a high degree of static indetermination, especially for long span bridges. Cable-stayed bridges exhibit several nonlinear behaviors concurrently under normal design loads due to the individual nonlinearity of substructures such as the pylons, stay cables, and bridge deck, and their interactions. The geometric nonlinearities arise mainly from large displacements of cables. Strong axial and lateral forces acting on the bridge deck and pylons cause structural nonlinear behaviors. The interaction is among the substructures. In this paper, a typical three-span steel cable-stayed bridge with a variety of design parameters has been investigated. The numerical results indicate that the design parameters such as the ratio of $L_1/L$ and $I_p/I_b$ are important for the structural behavior, where $L_1$ is the main span length, L is the total span length of the bridge, $I_p$ is the moment of inertia of the pylon, and $I_b$ is the moment of inertia of the bridge deck. When the ratio $I_p/I_b$ increases, the critical load decreases due to the lack of interaction among substructures. Cable arrangements and the height of pylon are another important factors for this type of bridge in buckling analysis. According to numerical results, the bridges supported by a pylon with harp-type cable arrangement have higher critical loads than the bridges supported by a pylon with fan-type cable arrangement. On contrary, the shape of the pylon does not significantly affect the critical load of this type of bridge. All numerical results have been non-dimensionalized and presented in both tabular and graphical forms.

• Journal of Astronomy and Space Sciences
• /
• v.21 no.4
• /
• pp.249-262
• /
• 2004

The variations of the dynamical substructures of NGC 6934 have been investigated by means of performing point spread function stellar photometry and the surface photometry on BV CCD images of NGC 6934. Our results show that overall variations of ellipticity and position angle range in $0.02{\sim}0.08\;and\;-90^{\circ}{\sim}+90^{\circ}$, respectively out to three times the half light radius. The inner ($r_{eff}) substructures of NGC 6934 inferred from the variations of ellipticity and position angle are mainly affected by the bright red giant populations, while the effects of the other giant populations are weaker than those of the bright red giant populations. Horizontal branch populations and faint red giant star populations affect the dynamical substructures of NGC 6934 in the region of $r_h.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.5
• /
• pp.391-401
• /
• 2009

The hybrid approach for structural experiments decomposes a structure into independent substructures that can be tested or simulated. The results from the decomposed substructures are combined to predict the behaviors of the entires structure. The hybrid approach is especially useful for the hybrid pseudo-dynamic tests that overcome the limitations of size of a test structure present in a shaking table test. The development of a computer system for the hybrid experiment requires a data model that formally organizes the information involved in the hybrid experiments. This paper provides the data model for representing the information involved in the hybrid experiments, by modifying the classes and attributes for the hybrid experiments in the Lehigh Model that is one of the data models for structural experiments. The data model for the hybrid experiments includes the classes for the physical substructures being tested and the analytical substructures being analyzed, and the simulation coordinator managing the overall experiments. Some objects for classes are implemented as an example to show the links among the classes. The data model presented in this paper can be applied for developing a computer system that helps structural engineers and researchers store, share, and access the information for the hybrid experiments.

• The Journal of Korean Academy of Prosthodontics
• /
• v.42 no.6
• /
• pp.654-663
• /
• 2004

Statement of problem. According to the fracture pattern in several reports, fractures most frequently occur in the interface between the ceromer and the substructure. Purpose. The aim of this in vitro study was to compare the macro shear bond strength and microshear bond strength of a ceromer bonded to a fiber reinforced composite (FRC) as well as metal alloys. Material and methods. Ten of the following substructures, type II gold alloy, Co-Cr alloy, Ni-Cr alloy, and FRC (Vectris) substructures with a 12 mm in diameter, were imbedded in acrylic resin and ground with 400, and 1, 000-grit sandpaper. The metal primer and wetting agent were applied to the sandblasted bonding area of the metal specimens and the FRC specimens, respectively. The ceromer was placed onto a 6 mm diameter and 3 mm height mold in the macro-shear test and 1 mm diameter and 2 mm height mold in the micro-shear test, and then polymerized. The macro- and micro-shear bond strength were measured using a universal testing machine and a micro-shear tester, respectively. The macro- and micro-shear strength were analyzed with ANOVA and a post-hoc Scheffe adjustment ($\alpha$ = .05). The fracture surfaces of the crowns were then examined by scanning electron microscopy to determine the mode of failure. Chi-square test was used to identify the differences in the failure mode. Results. The macro-shear strength and the micro-shear strength differed significantly with the types of substructure (P<.001). Although the ceromer/FRC group showed the highest macroand micro-shear strength, the micro-shear strength was not significantly different from that of the base metal alloy groups. The base metal alloy substructure groups showed the lowest mean macro-shear strength. However, the gold alloy substructure group exhibited the least micro-shear strength. The micro-shear strength was higher than the macro-shear strength excluding the gold alloy substructure group. Adhesive failure was most frequent type of fracture in the ceromer specimens bonded to the gold alloys. Cohesive failure at the ceromer layer was more common in the base metals and FRC substructures. Conclusion. The Vectris substructure had higher shear strength than the other substructures. Although the shear strength of the ceromer bonded to the base metals was lower than that of the gold alloy, the micro-shear strength of the base metals were superior to that of the gold alloy.

• Journal of KIISE:Computing Practices and Letters
• /
• v.11 no.2
• /
• pp.133-148
• /
• 2005

Since understanding of similarities and differences among protein structures is very important for the study of the relationship between structure and function, many protein structure comparison systems have been developed. Hut, unfortunately, these systems introduce their own protein data derived from the PDB(Protein Data Bank), which are needed in their algorithms for comparing protein structures. In addition, according to the rapid increase in the size of PDB, these systems require much more computation to search for common substructures in their databases. In this paper, we introduce a protein structure comparison system named WS4E(A Web-Based Searching Substructures of Secondary Structure Elements) based on a PSAML database which stores PSAML documents using the eXist open XML DBMS. PSAML(Protein Structure Abstraction Markup Language) is an XML representation of protein data, describing a protein structure as the secondary structures of the protein and their relationships. Using the PSAML database, the WS4E provides web services searching for common substructures among proteins represented in PSAML. In addition, to reduce the number of candidate protein structures to be compared in the PSAML database, we used topology strings which contain the spatial information of secondary structures in a protein.

• Korean Journal of Mathematics
• /
• v.16 no.3
• /
• pp.271-280
• /
• 2008

In this paper, we initiate a study of faithful R-group G and some substructures of R and G. Next, we investigate a faithful representation of near-ring R and some properties of monogenic Rgroups.