• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.145-148
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• 2006

Near surface mounted (NSM) is a recent strengthening technique based on bonding fiber reinforced polymer (CFRP) bars (rods and laminate strips), the use of NSM FRP bars is Emerging as a promising technology for increasing flexural strength of deficient concrete. In order for this technique to perform effectively, the structural behaviour of RC element strengthened with NSM FRP bars to be fully characterized. Totally, 10 beams were tested using symmetrical two-point loads test. The parameters examined under the beam test were a diffrent type of strengthening length.

• Imaging Science in Dentistry
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• v.39 no.3
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• pp.133-147
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• 2009

Purpose : To investigate the reproducibilities and compare the measurements in digital and MDCT-synthesized cephalometric radiograph, and to investigate the effect of head position on the measurement during imaging with MDCT. Materials and Methods : Twenty-two dry skulls (combined with mandible) were used in this study. Conventional digital cephalometric radiograph was taken in standard position, and MDCT was taken in standard position and two rotated position ($10^{\circ}$ left rotation and $10^{\circ}$ right tilting). MDCT data were imported in $OnDemand^{(R)}$ and lateral cephalometric radiograph were synthesized from 3D virtual models. Two types of rotated MDCT data were synthesized with default mode and with corrected mode using both ear rods. For all six images, sixteen angular and eleven linear measurements were made in V-$Ceph^{(R)}$ three times. Reproducibility of measurements was assessed using repeated measures ANOV A and ICC. Linear and angular measurements were compared between digital and five MDCT-synthesized images by Student t-test. Results : All measurements in six types of cephalometric radiograph were not statistically different under ICC examination. Measurements were not different between digital and MDCT-synthesized images (P>.05). Measurements in MDCT-synthesized image in $10^{\circ}$ left rotation or $10^{\circ}$ right tilting position showed possibility of difference from digital image in some measurements, and possibility of improvement via realignment of head position using both ear rods. Conclusion : MDCT-synthesized cephalometric radiograph can substitute conventional cephalometric radiograph. The error on head position during imaging with MDCT have possibility that can produce measurement errors with MDCT-synthesized image, and these position error can be corrected by realignment of the head position using both ear rods.

• Journal of KSNVE
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• v.5 no.4
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• pp.515-524
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• 1995

Tubes in heat exchanger of fuel rods in reactor core are supported at intemediate point by support p0lates or springs. Current practice is, in case of heat exchanger, to allow clearance between tube and support plate for design and manufacturing consideration. And in case of fuel rod the clearance in support point can be generated due to the support spring force relaxation. Flow-induced vibration of a tube can cause it to impact or rub against support plate or against adjacent tubes and can result in fretting-wear. The tube-to- support dynamic interaction is used to relate experimental wear data from single-span test rigs to real multi-span heat exchanger configurations. The dynamic interaction cna be measured during experimental wear tests. However, the dynamic interaction is difficult to measure in real heat exchangers and, therefore, analytical techniques are required to estimate this interaction. This paper describels the nonlinear impact model of DAGS(Dynamic Analysis of Gapped Structure) code which simulates the tube response to external sinusodial or step excitation and predicts tube motion and tube-to-support dynamic interaction. Three experimental measurements-two single span rods excited by sinusodial force and a two span rod impacted by a steel ball are compared from the simulation nonlinear model of DAGS code. The simulation results from DAGS code are in good agreement with measurements. Therefore, the developed model of DAGS code is good analytical tool for estimating tube-to-support dynamic interaction in real heat exchangers.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.6
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• pp.745-750
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• 2005

Statement of problem. Resonance frequency analysis has been increasingly served as a non-invasive and objective method for clinical monitoring of implant stability. Many clinical studies must be required for standardized data using RFA. Purpose. This study was performed to evaluate RFA value changes in two anodized implant groups. Material and method. Among a total of 24 implants, twelve screw shaped implants as a test group (H2-R8.5) were manufactured, which had a pitch-height of 0.4 mm, an outer diameter of 4.3 mm, a length of 8.5 mm, and external hexa-headed, were turned from 5 mm rods of commercially pure titanium (ASTM Grade IV, Warantec Co., Seoul, Korea), and another twelve implants as a control group were $Br{\aa}nemark$ Ti-Unite MK4 (diameter 4.0 mm, length 8.5 mm). Each group was installed in tibia of rabbit. Two implants were placed in each tibia (four implants per rabbit). Test two implants were inserted in right side and control two in left side. ISQ values were measured using $Osstell^{TM}$ (Integration Diagnostics Ltd. Sweden) during fixture installation, and 12 weeks later and evaluated the RFA changes. Results. Mean and SD of baseline ISQ values of test group were $75.0{\pm}3.4$ and $68.7{\pm}8.1$ for control group. Mean and SO of ISQ values 12 weeks after implant insertion were $73.2{\pm}4.7$ for test group and $72.6{\pm}3.9$ for control group. There were no statistically significant differences between groups in ISQ values after 3 months (P>0.05). From the data, RFA gains after 3 months were calculated, and there was statistically significant difference between groups (P<0.05). Conclusion. Although there were RFA changes between groups, implant stability after experimental period shows alike tendency and good bone responses.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.6
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• pp.3-10
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• 2018

This paper described the shear strengthening effect by deviator location in pre-damaged reinforced concrete (RC) beams strengthened with externally post-tensioning steel rods. Three reinforced concrete beams as control beam and eight post-tensioned beams using external steel rods were tested to fail in shear. The externally post-tensioning material was a steel rod of 22 mm diameter, and it had a 655 MPa yield strength and an 805 MPa tensile strength. Specimens depend on multiple variables, such as the number of deviators, location of deviator, and load pattern. The pre-damaged loads up to about 2/3 of ultimate shear capacities were applied to specimens using displacement control and the diagonal shear crack just occurred at these loading levels. And then, the post-tensioning up to when a strain of steel rod reaches about $2000{\mu}{\varepsilon}$ was continuously applied to beam. A displacement control was changed to a load control during post-tensioning. The post-tensioning resulted in increase of load-carrying capacity and restoration of existing deflection. Also, it prevented the existing diagonal cracks from excessively growing. Two deviators effectively improved the load capacity when compared with in case of test which one deviator at mid-span installed. When deviators were located near region which the diagonal crack occurred on, the strengthening impact by post-tensioning was greater.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.3
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• pp.424-431
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• 2003

The spacer grid is one of the main structural components in the fuel assembly, which supports the fuel rods and maintains coolable geometry from an external load. A vibration test and a finite element analysis using ABAQUS on a dummy fuel rod continuously supported by Optimized H type(OHT) and New Doublet (ND) spacer grids arc performed to obtain the vibration characteristics such as natural frequencies and mode shapes an(1 to verify a finite element model. The results from the test and the finite element analysis are compared by modal assurance criteria (MAC) values. It is resulted that MACs for the first, the third and the fifth mode shapes are relatively good as compared with those of the second an(1 fourth ones. The natural frequency differences between two methods as well as the mode comparison results for the rod with OHT spacer grid are better than those with ND spacer grid. It is judged that the FE model for the ND spacer grid spring should be modified to consider the long contact length which actually happen when the spring supports the rod.

• Steel and Composite Structures
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• v.36 no.5
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• pp.569-586
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• 2020

The behavior of composite steel-concrete beams depends on the transmission of forces between two parts: the concrete slab and the steel I-beam. The shear connector is responsible for the interaction between these two parts. Recently, an alternative shear connector, called Truss Type connector, has been developed; it aligns efficient structural behavior, fast construction and implementation, and low cost when compared to conventional connectors applied in composite structures. However, there is still a lack of full understanding of the mechanical behavior of the Truss Type connector, due to its novelty. Thus, this study aims to analyze the influence of variation of geometric and physical parameters on the shear resistance of the Truss Type connector. In order to investigate those parameters, a non-linear finite element model, able to simulate push-out tests of Truss Type connectors, was specifically developed and validated with experimental results. A thorough parametric study, varying the height, the angle between rods, the diameter, and the concrete strength, was conducted to evaluate the shear resistance of the Truss Type connector. In addition, an equation to predict the resistance of the original Truss Type shear connector was proposed.

• Tribology and Lubricants
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• v.34 no.1
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• pp.33-41
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• 2018

This paper describes a new test rig for identification of rotordynamic force coefficients of squeeze film dampers (SFDs) in automotive turbochargers (TCs). Prior studies have mainly concentrated on relatively large-sized SFDs used in aircraft engines, turbocompressors, and turbopumps. The main objective of the current study is to propose a test rig for identification of dynamic force coefficients of small-sized SFDs (a journal diameter of ~11 mm). The current test rig consists of a journal, a SFD cartridge, four support rods, an upper structure, a data acquisition (DAQ) system, and an oil circulation unit. The annular gaps between the journal outer surface and SFD cartridge inner surface create SFD film lands. The damper has two parallel film lands separated by a central groove, having an axial length and depth of 3 mm. Each film land has a length of 4 mm with a $40{\mu}m$ radial clearance. The static load and dynamic impact tests identify the structural characteristics (i.e., stiffness and natural frequency) of the journal and assembled test rig. The measurements show good agreement with predictions. The SFD performance data from this test rig will be used to develop innovative TC rotor systems with improved NVH and reliability characteristics incorporating advanced SFD technology.

• Journal of Periodontal and Implant Science
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• v.29 no.2
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• pp.433-447
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• 1999

The objective of this study was to evaluate the effect a chewable tablet containing sodium flouride and lauroyl sodium sulfate on removing plaque and inhibiting gingival inflammation. A randomized parallel study was designed. 100 voluteers participated in the study. There were two test groups each with 30 subject. Test group A was instructed to brush once in the morning, and to use the tablet once in the afternoon and once in the evening. Test group B was instructed to use the tablet three times a day without brushing. There were two control groups each with 20 subjects. Control group A was instructed to brush once in the morning only. Control group B was instructed not to brush all. Two weeks before the test period, the subjects received through tooth cleaning and polishing. At baseline, GI, PI, BOP, and GCF of the Ramfjord teeth were measured in all groups. Bacteria culture was done with the plaque sampled from tooth with the deepest pocket. After 5 days, clinical indices were measured and the bacterial culture was repeated. Control group B was dropped from the study after this period. All the other groups remained and the indices and the culture was repeated after 2 weeks, and 3weeks. Also whether the oral mucosa showed signs of irritation was monitored throughout the test period. Test group A showed less PI, GI, BOP, probing depth, GCF than test group B or control group A. Especially, PI and the BOP was significantly less than that of the group that was instructed to brush once a day. This implies that the added use of this tablet aids in plaque removal in people who brush just once a day. Test group A showed increase of cocci, decrease of motile rods, and decrease of spirochetes after 14-21 days. And this was significantly different from the control group A. At no time of the test period did any of the subjects show signs of irritation of the oral mucosa or adverse reactions. Following conclusions could be obtained from this study. This chewable tablet for enhanced oral hygiene could be used as an adjunct to oral hygiene in people who do not brush adequately. The use of this tablet decreased the number of subgingival bacteria, and this could be effective in plaque removal and for prevention of gingival inflammation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.4
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• pp.165-175
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• 1997

This study qualitatively reviewed effect of the height of loading and the ratio of penetration on. the characteristics of deformation of cellular bulkhead by performing a model test of embedded steel plate cellular bulkhead which had different loading height and penetration ratio. And we also examined the effect of the loading height upon the shear behavior by performing two-dimensional model test making use of aluminum rods for a filler. Besides, test results and theoretical values based on Hansen's earth pressure theory were compared and reviewed. In consequence, it was ascertained that the yield moment of cells depended on the height of loading and the ratio of penetration, and the slip surface was located on the lower area of a cell interior according as the height of loading becomes lower. The theoretical consideration which was based on the theory of earth pressure proposed by Hansen revealed that the test results accorded with the theoretical values to some degree, and the same results were derived about the location change of the slip surface.