• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.72-84
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• 2016

The conventional brace system is generally accepted as the lateral load resisting system for steel structures due to efficient story drift control and economic feasibility. But lateral stiffness of the structure decreases when buckling happens to the brace in compression, so that it results in unstable structure with unstable hysteresis behavior through strength deterioration. Buckling restrained brace(BRB) system, in which steel core is confined by mortar/concrete-filled tube, represents stable behavior in the post-yield range because the core's buckling is restrained. So, seismic performance of BRB is much better than that of conventional brace system in point of energy absorption capacity, and it is applied the most in high seismicity regions as damper element. BRBs with various shaped-sections have been developed across the globe, but the shapes experimented in Korea are now quite limited. In this study, we considered built-up type of restraining member made up of precast reinforcement concrete and the steel core. we experimented the BRB according to AISC(2005) and evaluated seismic performances and hysteresis characteristics.

• Journal of the Korea Convergence Society
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• v.9 no.2
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• pp.303-311
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• 2018

Squat exercise is one of the free weight exercises that are recognized as important from a bio-mechanical point of view. It is an important exercise to train lower extremity muscles in daily activities or sports activities and to strengthen trunk and lower body strength. It is effective and accurate to use a variety of assistive devices to calibrate athletic posture with squat exercise supported interactive device. The issues of the structural analysis for design a foot plate for squat exercise is to model the behavior by simplifying the dynamic behavior. In this paper, the authors proposed a exercise system design method for the vertical load distribution and bio-mechanical signal process used for the squat exercise mechanism analysis, and based on these results, designed device can make the more safe and reliable free weight exercise. It is applied to system design through design method with kinematic dynamic, VR device and estimation model of exercise.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.215-228
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• 2017

A new approach for measuring the specific fracture energy of concrete denoted modified disk-shaped compact tension (MDCT) test is presented. The procedure is based on previous ideas regarding the use of compact tension specimens for studying the fracture behavior of concrete but implies significant modifications of the specimen morphology in order to avoid premature failures (such as the breakage of concrete around the pulling load holes). The manufacturing and test performance is improved and simplified, enhancing the reliability of the material characterization. MDCT specimens are particularly suitable when fracture properties of already casted concrete structures are required. To evaluate the applicability of the MDCT test to estimate the size-independent specific fracture energy of concrete ($G_F$),the interaction between the fracture process zone of concrete andthe boundary of theMDCTspecimens at the end of the test is properly analyzed. Further, the experimental results of $G_F$ obtained by MDCT tests for normal- and high-strength self-compacting concrete mixes are compared with those obtained using the well-established three-point bending test. The procedure proposed furnishes promising results, and the $G_F$ values obtained are reliable enough for the specimen size range studied in this work.

• Restorative Dentistry and Endodontics
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• v.26 no.6
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• pp.464-484
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• 2001

When restoring a tooth, the dentist tries to choose the ideal material for existing situation. One criterion that is considered is its suitability for restoring coronal strength. As more tooth structure is removed, the cusps are weakened and susceptible to fracture. Further, this increased deformation may cause the formation of intermittent gaps at the margin between the hard tissue and the restoration, facilitating marginal leakage. The improvements in ceramic materials now make it possible for alternatives to amalgams, composites, and cast metal to be of offered for posterior teeth. Of the materials used, ceramics most closely approximates the properties of enamel. The introduction of computer-aided design/computer-aided manufacture(CAD/CAM) systems to restorative dentistry represents a major technological breakthrough. It is possible to design and fabricate ceramic restorations at a single appointment. Additionally, CAD/CAM systems eliminate certain errors and inaccuracies that are inherent to the indirect method and provide an esthetic restoration. The aim of this investigation was to study the loading characteristics of CAD/CAM ceramic inlay and to compare the stress distribution and displacement associated with different designs of cavity(the isthmus width and cavity depth). A human maxillary left first premolar was prepared with standard mesio-occlusal cavity preparation, as recommended by the manufacturer Ceramic inlay was fabricated with CEREC 2 CAD/CIM equipment and cemented into the prepared cavity. Three dimensional model was made by the serial photographic method. The cavity width was varied $\frac{1}{3}$, $\frac{1}{2}$ and $\frac{2}{3}$ of intercuspal distance between buccal and lingual cusp tip. The cavity depth was varied 1.5mm and 2.3mm. So six models were constructed to simulate six conditions. A point load of 500N was applied vertically onto the first node of the lingual slope from the buccal cusp tip. The stress distribution and displacement were solved using ANSYS finite element program(Swanson Analysis System). (omitted)

• The KIPS Transactions:PartC
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• v.18C no.3
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• pp.187-194
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• 2011

IEEE 802.11 wireless LAN has become the center of attention for one of the most dominant wireless networking technologies nowadays. In densely deployed wireless LANs, mobile stations are exposed to a number of AP, thus it is needed to select the best AP to associate with. The most common approach is to select the AP with the highest received signal strength. However it does not consider traffic load imposed to each AP so that it may cause the poor network performance. Therefore, in this paper, we propose a throughput estimation scheme for neighboring APs by sniffing the traffic within 802.11 networks. We devise a tool, named "VirtFrame", which is to estimate the station's capable throughput from neighbor APs based on the channel access time by virtually combining the sniffed frames. Simulation results show that our proposed scheme well matches that there exists correlation between the channel access time and the actual throughput of the APs.

• Nuclear Engineering and Technology
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• v.42 no.4
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• pp.450-459
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• 2010

The present paper investigates the collapse pressure of cylinders with intermediate thickness subjected to external pressure based on detailed elastic-plastic finite element (FE) analyses. The effect of the initial ovality of the tube on the collapse pressure was explicitly considered in the FE analyses. Based on the present FE results, the analytical yield locus, considering the interaction between the plastic collapse and local instability due to initial ovality, was also proposed. The collapse pressure values based on the proposed yield locus agree well with the present FE results; thus, the validity of the proposed yield locus for the thickness range of interest was verified. Moreover, the partial safety factor concept based on the structural reliability theory was also applied to the proposed collapse pressure estimation model, and, thus, the priority of importance of respective parameter constituting for the collapse of cylinders under external pressure was estimated in this study. From the application of the partial safety factor concept, the yield strength was concluded to be the most sensitive, and the initial ovality of tube was not so effective in the proposed collapse pressure estimation model. The present deterministic and probabilistic results are expected to be utilized in the design and maintenance of cylinders subjected to external pressure with initial ovality, such as the once-through type steam generator.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.6
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• pp.271-276
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• 2020

In this study, an amorphous SiC block was manufactured using polycarbosilane (PCS), an organosilicon polymer. The dense SiC blocks were easily fabricated in various shapes via pyrolysis at 1100℃, 1200℃, 1300℃, 1400℃ after manufacturing a PCS molded body using cured PCS powder. Physical and chemical properties were analyzed using a thermogravimetric analyzer (TGA), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and universal testing machine (UTM). The prepared SiC block was decomposed into SiO and CO gas as the temperature increased, and β-SiC crystal grains were grown in an amorphous structure. In addition, the density and flexural strength were the highest at 1.9038 g/㎤ and 6.189 MPa of SiC prepared at 1100℃. The manufactured amorphous silicon carbide block is expected to be applicable to other fields, such as the previously reported microwave assisted heating element.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.27 no.3
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• pp.1-15
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• 2021

Objective: The purpose of this study was to examine the differences in joint position sense (JPS), force sense (FS), and performance level of the upper extremities according to the injury and pain experiences of Korean elite archers. Methods: A total of 15 subjects were briefed about the purpose of this study and agreed to participate voluntarily. JPS was evaluated using the laser-point attached to the wrist while aiming at the target. The difference when relocating while aiming was used as JPS factor. FS was evaluated using load cell through reproduces same muscle strength. Fear-Avoidance Beliefs Questionnaire (FABQ) was used to evaluate psychosocial factors, Kerlan-Jobe Orthopedic Clinic overhead athlete scores (KJOC) and numerical rating scale (NRS) was used to evaluate pain. and performance was evaluated by tournament match score. Results: There is a strong correlation between the current pain and KJOC. Moreover, moderate correlation between KJOC and FABQ also current pain and both upper trapezius and lower trapezius in elite archers. The mean (SD) between groups based on current pain display relatively large margin in force sense than without pain group. The result presents that there is a significant difference in performance and pain. There is a significant difference in the force sense of the upper and lower trapezius and pain. Conclusions: Result present there is a significant difference in functional level in the average comparison between groups according to the presence of absence of current pain. There is a significant difference in the force sense of the upper trapezius as well as lower trapezius and without pain group present a relatively low joint position sense error compared to the groups.

• Composites Research
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• v.34 no.6
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• pp.394-399
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• 2021

Piecewise Integrated Composite (PIC) is a new concept to design composite structures of multiple stacking angles both for in-plane direction and through the thickness direction in order to improve stiffness and strength. In the present study, PIC beam was suggested based on 3D training data instead of 2D data, which did offer a limited behavior of beam characteristics, with enhancing the stiffness accompanied by reduced tip deformation. Generally training data were observed from the designated reference finite elements, and preliminary FE analysis was conducted with respect to regularly distributed reference elements. Also triaxiality values for each element were obtained in order to categorize the loading state, i.e. tensile, compressive or shear. The main FE analysis was conducted to predict the mechanical characteristics of the PIC beam.

• Composites Research
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• v.36 no.6
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• pp.388-394
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• 2023

In composites manufacturing, increasing resin impregnation is a key way to speed up the manufacturing process and improve product quality. While resin improvement is important, simple fiber surface treatments can also improve resin flowability. In this study, different plasma treatment times were applied to carbon fiber fabrics to improve the impregnation between resin and fiber. Electrical resistivity measurements were used to evaluate the dispersion of resin in the fibers, which changed with plasma treatment. The effect of fiber surface treatment on resin spreadability could be observed in real time. When inserting a carbon fiber tow into the resin, the amount of resin that soaked into the tow was measured to objectively compare resin impregnation. Five minutes of plasma treatment improved the tensile and compressive strength of the composite by more than 50%, while reducing the void content and increasing the fire point impregnation flow rate. Finally, a dynamic flexural fatigue test was conducted using a portion of the composite used as an architectural composite part, and the composite part did not fail after one million cycles of a 3 kN load.