• The Journal of Korean Academy of Prosthodontics
• /
• v.43 no.4
• /
• pp.478-486
• /
• 2005

Statement of problem : Fracture and dimensional change of an acrylic resin denture are a rather common occurrence. Purpose : The purpose of this study was to compare differences in dimensional changes and flexural strength of separate maxillary complete dentures after immediate deflasking by injection molding and conventional compression processing. Material and method: To evaluate dimensional stability, the maxillary dentures were fabricated by using different materials and methods. Lucitone 199(Dentsply Trubyte. york, pennsylvania, USA) and Vertex(Dentimex, zeist, Netherlands) were used as materials. Compression and injection packing methods were used as processing methods. The impression surface of the dentures was measured by 3D Scann-ing System(PERCEPTRON USA) and overlapped original impression surface of the master cast. To evaluate flexural strength, resin specimens were made according to the different materials, powder/liquid ratio and processing methods. Flexural strength of the complete resin specimens (64mm$\times$10mm$\times$3.3mm) were measured by INSTRON 4467. (INSTRON, England) The data was analyzed by ANOVA, t-test and Tukey test. (p<.05 level of significance) Result: The results were as follows 1. There was no significant differences between master model and denture base for each group in overall dimensional changes. 2. Palatal area was more stable than flange or alveolar area in dimensional stability. but. there was no significant differences among each area. 3. Materials and power/liquid ratio had an effect on flexural strength. (P<.05) Especially materials was most effective. (P<.05) 4. Lucitone 199(powder/liquid ratio followed by manufacturer's direction) showed higher flexural strength than Vertex. Conclusion : Dimensional stability or flexural strength are affected by materials rather than packing techniques.

• Journal of Trauma and Injury
• /
• v.18 no.2
• /
• pp.107-111
• /
• 2005

Backgrounds: To evaluate the effectiveness of conservative treatment in osteoporotic thoraco-lumbar compression fractures and to identify the factors influencing the progression of compression. Materials and Methods: From January 2003 to October 2004, Patients who were admitted to our hospital for osteoporotic thoraco-lumbar compression fractures were reviewed retrospectively with follow-up more than 12 months (ave. 14.6 months). With simple x-ray lateral view, we evaluate wedge compression ratio (WCR) and kyphotic angle (KA) at initial and final follow-up. We separate the patients into two groups baesed on the amount of progression of vertebral compression and evaluate a relation with BMD, vertebral fracture level, initial WCR, initial KA. All datas were statistically analyzed. Results: An average of T-score was -3.5 and the changes of KA between initial and final follow-up were average $3.5^{\circ}$. Compression of anterior column were progressed to 8.5%. The changes between initial and final WCR in Group I (N=24) was 17.8%, and Group II (N=18) was 3.3%. T-score in group I was -3.4 and group II was -3.8 (p=0.228). vertebral fracture level were 10 T12, 12 L1, 2 L2 in group I; 6 T12, 6 L1, 6 L2 in group II (p=0.156). Initail WCR was 0.74 in group I, 0.63 in group II, and there was statistical difference between two groups(p=0002). Initial kyphotic angle was $13.9^{\circ}$in group I, $16.2^{\circ}$in group II repectively (p=0.392). Conclusion: The conservative treatment with short-term bed rest and early embulation is effective and valuable method to patients who have osteoporotic thoraco-lumbar compression fractures. There was no statistical difference between two groups according to BMD, vertebral fracture level, KA. But in comparison with initail WCR between two groups, there was statistical difference. That means, in the case of small initial compression of anterior column, the progression of compression was bigger than else. In these patients, more strict use of appropriate brace and careful follow-up should be needed.

• Steel and Composite Structures
• /
• v.3 no.4
• /
• pp.261-275
• /
• 2003

Truss members built-up with double angles back-to-back have monosymmetric cross-section and twisting always accompanies flexion upon the onset of buckling about the axis of symmetry. Approximate formulae for calculating the buckling capacity are presented in this paper for routine design purpose. For a member susceptible only to flexural buckling, its optimal cross-section should consist of slender plate elements so as to get larger radius of gyration. But, occurrence of twisting changes the situation owing to the weakness of thin plates in resisting torsion. Criteria for limiting the leg slenderness are discussed herein. Truss web members in compression are usually considered as hinged at both ends for out-of-plane buckling. In case one (or both) end of member is not supported laterally by bracing member, its adjoining members have to provide an elastic support of adequate stiffness in order not to underdesign the member. The stiffness provided by either compression or tension chords in different cases is analyzed, and the effect of initial crookedness of compression chord is taken into account. Formulae are presented to compute the required stiffness of chord member and to determine the effective length factor for inadequately constrained compressive diagonals.

• Journal of Korea Game Society
• /
• v.14 no.6
• /
• pp.29-38
• /
• 2014

In the large scale indoor 3D game scenes, the data amount of potentially visible set (PVS) which pre-computes the information of occlusion culling can be huge. However, the large part of them can be represented as zero. In this paper, the effective hardware structure is designed, which compresses PVS data as the way of zero run length encoding (ZRLE) during building the scene trees of 3D games in mobile environments. The compression ratio of the proposed structure and the rendering speed (frame per second: FPS) according to both PVS culling and frustum culling are analyzed under 3D game simulations.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.28B no.11
• /
• pp.866-875
• /
• 1991

In this paper, multi pulse excited-linear predictive coding (MPE-LPC), where the correlation eliminated residual signal is modeled by a few pules, is shown to be effective for the compression of electrocardiogram (ECG) data, and a more efficient scheme for a faithful reconstruction of ECG is proposed. The reconstruction charateristic of QRS's and P.T waves is improved using the adaptive pulse allocation (APA), and the compression ratio (CR) can be changed by controlling the mumber of modeling pulses. The performance of the proposed method was evaluated using 10 normal and 10 abnormal ECG data. The proposed method had a better performance than the variable threshold amplitude zone time epoch coding (AZTEC) algorithm and the scan-along polygonal approximation (SAPA) algorithm with the same CR. With the CR in kthe range of 8:1 to 14:1, we could compress ECG data efficiently.

• Structural Engineering and Mechanics
• /
• v.8 no.6
• /
• pp.531-546
• /
• 1999

The paper presents an experimental and theoretical study on the influence of steel fibers and longitudinal tension and compression reinforcements on immediate and long-term deflections of high-strength concrete beams of 85 MPa (12,300 psi) compressive, strength. Test results of eighteen beams subjected to sustained load for 180 days show that the deflection behavior depends on the longitudinal tension and compression reinforcement ratios and fiber content; excessive amount of compression reinforcement and fibers may have an unfavorable effect on the long-term deflections. The beams having the ACI Code's minimum longitudinal tension reinforcement showed much higher time-dependent deflection to immediate deflection ratio, when compared with that of the beams having about 50 percent of the balanced tension reinforcement. The results of theoretical analysis of tested beams and those of a parametric study show that the influence of steel fibers in increasing the moment of inertia of cracked transformed sections is most pronounced in beams having small amount of longitudinal tension reinforcement.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.4 no.1
• /
• pp.13-20
• /
• 1998

Since the digital chart consists of a large number of points, the effective method for the coastline data compression(CDC), storing the data compactly and reproducting the coastline feature accurately, is important. In the CDC, the key technique is to determine the optimal positions as node points in given coastlines. In this paper, a new CDC method, selecting node points with conspicuous coast positions in the view point on navigation and adopting spline interpolation to the nodes partly, is proposed. Using the northern part of KEOJE-DO coastline in Korean chart No.204, CDC experiments are carrie out with various compression ratio. The results fro the influence of coastline shape according to various CDC methods are discussed and presented.

• Journal of Ocean Engineering and Technology
• /
• v.15 no.1
• /
• pp.98-103
• /
• 2001

This paper is conducted to compare the seismic design standard of a bridge column such as the Korean Bridge Design Standard(KBDS), EC 8, NZS 3101 and ATC 32. The KBDS adopted the seismic design requirements in 1992. The earthquake magnitude in Korea is compared with those in the west coast of the USA. It may be said that the current seismic design requirements of the KBDS provides design results, that are too conservative especially for transverse reinforcement details and amounts in reinforced concrete columns. This fact usually creates construction problems in concrete casting, due to congestion of transverse reinforcement. Furthermore, the effective stiffness; $I_{eff}$ depends on both the axial load P/$A_gF_{ck}$ and the longitudinal reinforcement ratio $A_{st}/A_g, so it is the conservative to use the effective stiffness I$_{eff}$ than the gross section stiffness Ig. Seismic design for the transverse reinforcement content of the concrete column was analyzed and considered to have an extreme-fiber compression strain, response modification factor, axial load and effective stiffness etc.c.

• Journal of Korean Society of Steel Construction
• /
• v.15 no.2
• /
• pp.159-165
• /
• 2003

A tubular member with through-gusset plate is often used to transmit axial compression in an electric transmission towers. In current code, the strength of tubular member is evaluated with an effective length factor k=0.9 without considering the deformation of boundary element. A buckling strength of member with end gusset plate is affected by stiffness ratio($\beta$) and the length ratio(G) between main tubular member and end gusset plate. In this study theoretical mechanism based on the elastic buckling behavior was investigated, and finite element analysis was performed to propose a formula for the buckling strength and effective length factor of tubular member in elsatic and inelastic ranges.

• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.8
• /
• pp.1009-1015
• /
• 2011

In this study, in the high expansion cycle was conduced by variable valve timing system composition to close intake valve late, and in the intake air reduction on the low compression was solved by supercharging pressure. In this wise, by constituting Diesel-Atkinson cycle, this study looked into a possibility of thermal efficiency improvement. As a result, there was improvement in thermal efficiency and output in a whole range of closing timing from ABDC $40^{\circ}$ to ABDC $80^{\circ}$. However, after ABDC $70^{\circ}$ of closing timing, the thermal efficiency increase was getting smaller. As the result of the study, the optimum intake valve closing timing was about ABDC $70^{\circ}$, high loading territory of engine was more effective than low loading territory, and engine operation in middle loading territory was stable. At this time, brake thermal efficiency was 12.5% higher than ordinary engine on average.