• Journal of Korean Society of Steel Construction
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• v.27 no.5
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• pp.483-491
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• 2015

Shear resistance of BESTOBEAM, which has angle as shear connector and was developed with purpose of easy construction, was tested. With the test results shear resistance design equation was proposed. Unlike angle connector of Eurocode 4, BESTO BEMA shear connector behaves like fixed-end beam. Therefor longer span of the shear connector the lower shear resistance it has. As a result, shear resistance of BESTOBEAM shear connector according to its length tends to decrease as its length gets longer. The authors proposed design equation of angle shear connector sased on the test results. The results from the test and the proposed equation match within 10% error range. Therefore the proposed equation can be used for designing shear connector of BESTOBEAM.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.5290-5298
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• 2013

In order to apply a mechanical deck joint to the prefabricated steel grid composite decks, shear resistance of a joint composed of concrete shear key and high-tension bolt is experimentally evaluated by the push-out test. Shear resistance evaluated by the test is compared with resistance estimated by empirical and design equations based on the shear friction theory. Test results show that joint specimens bonded by epoxy have about 10% more shear resistance than specimens with strengthened shear key by steel plates, but in the case of specimens with strengthened shear key there is smaller resistance deviation than specimens bonded by epoxy. In comparison with resistances estimated by empirical and design equations, the deck joint can be safely designed. But because the existed shear resistance of deck joint is underestimated by the ACI-318, application of the LRFD design equation could be more reasonable.

• Journal of Internet Computing and Services
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• v.12 no.4
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• pp.181-194
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• 2011

Server push which is technology of sending contents from servers to browsers in real time using long polling requests enables real time bidirectional communications between servers and browsers in HTTP environment. Recently, thanks to the rapid supply of mobile devices having ability of full browsing, server push is being applied to various applications. However, because servers providing services should offer distributed contents to a large number of users simultaneously in various user environments, they have a burden that offers contents quickly distinguishing much more concurrent users than before. The method of message exchange so far achieved in distributed server environment has difficulties in the performance of simultaneous user request process, the identification of users and the contents delivery. In this paper, We proposed message exchange architecture between servers for offering server push in the distributed server environment. The proposed architecture enables message exchange in the method of push between servers based on event driven architecture. In addition, the proposed architecture enables flexible identification of a event agent and event processing under the connected environment of a lot of users. In this paper, we designed and implemented the proposed architecture and compared performance with the previous way through a performance test. In addition, function is confirmed through the case realization. As a result of the performance test, the proposed architecture can lessen the use of server Thread and response time of users and increase simultaneous throughput.

• Restorative Dentistry and Endodontics
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• v.33 no.5
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• pp.443-451
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• 2008

The purpose of this study was to evaluate the effect of additional etching procedure prior to Maxcem resin cement application in indirect restoration cementation using push-out bonding strength. One hundred and two extracted human molars were used to make indirect resin restorations of gold inlay and Synfony. These restorations were cemented using Maxcem and Variolink II. Additional etching procedures were done for one group with Maxcem. Three groups have 17 specimens in both restoration types. Push-out bond strength was measured using multi-purpose tester and calculated for bonding strength per sqaure-millimeter area. The mean bonding strength values were compared using SPSS 12.0K program for one-way ANOVA and Scheffe's Test with 95% significance. Under the condition of this study, the additional etching procedure prior to usage of Maxcem resulted in reduced bond strength for both of restoration types.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.519-528
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• 2008

A simple steel-concrete composite deck is developed for preventing the lateral torsional buckling of girders that are under construction and for reducing the term of works using H-shaped rolled beams as bridge girders. A new type of shear connectors is also developed for the composite behavior between a simple steel-concrete composite deck and the rolled beams by the connecting conditions between the deck and the girders. One is a connector bolt that is lengthened and split or tightened with two nuts and the other is an I-shaped rolled beam welded on a steel plate with a number of holes punched through the web. In this study, to estimate the shear strength of those shear connectors the push-out tests are performed and the test results are compared with that of the previous studies and the codes. The result of the push-out tests of the connector bolts showed that the shear performance is similar to that of the stud connector and revealed that the equation for the shear strength in the Korean Specification of Highway Bridge overestimates the shear capacity of the connector bolt whose diameter is larger than 19mm. From the push-out tests of punched I-shaped rolled beams with varying welding amounts, with the small amount of welding, shear capacity is governed by the shear capacity of welding. On the other hand, shear capacity is governed by the size of the punched I-shaped rolled beams, regardless of the amount of welding.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.10a
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• pp.138-140
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• 2005

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.2
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• pp.131-137
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• 2000

In order to evaluate the design shear strength of composite slabs with truss-shaped shear connectors(TSC), a series of push-out tests on several types of specimens was carried out. The test results for the two parameters of bearing area and solid angle of the connector were compared to obtain the design shear force of the truss-shaped connectors. The results obtained from this study are as follows: (1) The slip-coefficients of TSC ranges from 0.87 to 3.12(${\times}10^6kgf/cm$). (2) The slip stiffness and the shear strength of TSC with $60.6cm^2$ bearing area are greater than those with $14.6cm^2$. (3) For estimating the allowable shear force of TSC, a design equation that is based on the bearing strength of the connector is suggested. (4) The mean safety factors of the critical force and the ultimate force are 2.38 and 4.62. respectively.

• Steel and Composite Structures
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• v.42 no.4
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• pp.477-487
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• 2022

The shear stiffness of headed-stud shear connectors has no unified definition due to the nonlinear characteristics of its load-slip relationship. A unified framework was firstly adopted to develop a general expression of shear load-slip equation for headed-stud shear connectors varying in a large parameter range based on both force and energy balance. The pre- and post-yield shear stiffness were then determined through bilinear idealization of proposed shear load-slip equation. An updated and carefully selected push-out test database of 157 stud shear connectors, conducting on studs 13~30mm in diameter and on concretes 30~180 MPa in cubic compressive strength, was used for model regression and sensitivity analysis of shear stiffness. An empirical calculation model was also established for the stud shear stiffness. Compared with the previous models through statistical analysis, the proposed model demonstrates a better performance to predict the shear load-slip response and stiffness of the stud shear connectors.

• Structural Engineering and Mechanics
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• v.80 no.5
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• pp.595-608
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• 2021

To investigate the mechanical behavior of large stud shear connector embedded in hybrid fiber-reinforced concrete (HFRC), a refined 3D nonlinear finite element (FE) model incorporating the constitutive model of HFRC was developed using ANSYS. Firstly, the test results conducted by the authors (He et al. 2017) were used to validate FE model of push out tests. Secondly, a total of 27 specimens were analyzed with various parameters including fiber volume fractions of HFRC, diameter of studs and HFRC strength. Finally, an empirical equation considering the contribution of steel fiber (SF) and polypropylene fiber (PF) was recommended to estimate the ultimate capacity of large stud shear connector embedded in HFRC.

• Journal of Biomedical Engineering Research
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• v.38 no.4
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• pp.143-152
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• 2017

The main purpose of this research was to examine the EMG characteristics of driver's upper limb and driving performance for operating accelerator and brake pedal by using four types of left hand control devices(Push/Pull, Push/Right angle, Push/Rock, Push/Twist) during simulated driving. The persons with disabilities in the lower extremity have problems in operation of the vehicle because of functional impairments for controlling accelerator and brake pedal. Therefore, if hand control device is used for adaptive driving controls in persons with lower extremity loss, the disabled people could improve their quality of mobility life by driving a car. Twenty subjects were involved in this research to assess driving performance and EMG activities for operating accelerator and brake pedal by using four types of left hand controls in driving simulator. We measured EMG responses of six muscles(posterior deltoid, middle deltoid, biceps, triceps, extensor carpi radialis, and flexor carpi radialis) during pulling and pushing movement with four types of left hand controls for acceleration and braking. STISim Drive 3 program was used for evaluation test of four types of left hand control devices in straight lane course for time to reach target speed and brake reaction time. While operating the four types of left hand controls for acceleration, EMG activities of posterior deltoid in normal subjects were significantly increased(p < 0.05) compared to the disabled subjects. It was also found that EMG responses of triceps and posterior deltoid were significantly increased(p < 0.05) when using the Push/Right angle type than Push/Pull type. While operating the four types of left hand controls for braking, EMG activities of flexor carpi radialis and triceps in subjects with disability were significantly increased(p < 0.05) compared to the normal subjects. It was shown that muscle responses of posterior deltoid, middle deltoid and triceps were significantly increased when using the Push/Right angle type than Push/Rock type. Time to reach target speed and brake reaction time in subjects with disability was increased by 2.5% and 4.6% on average compared to normal subjects. The person with disabilities showed a tendency to relatively slow performance in acceleration at the straight lane course.