• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.169-170
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• 2013

One important test for formation and grading of the lithium-ion battery is to confirm the performance of the battery while discharging battery down to zero volts. In this paper, a novel charge/discharge converter with zero-voltage discharge function is proposed. The proposed converter is able to discharge the battery until the voltage reaches to zero volts. The phase-shifted full bridge method is used to charge the battery and the current-fed push-pull method with bidirectional switches is used for the discharge. The ZVS turn-on is achieved in the charge operation and the ZVS turn-off in the discharge operation. The performance of the system is verified by the experiments using lithium-ion batteries.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.85-86
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• 2014

Connection between concrete and steel in composite members are usually achieved through shear connectors. In this study, the shear strength of concrete througth the holes of perfobond is experimentally obtained. Based on the size of perfobond, different strengths have been obtained and analyzed.

• Structural Engineering and Mechanics
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• v.28 no.3
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• pp.317-334
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• 2008

Seismic performance of coupling beams not designed for ductility is examined. Eight 1:4 scale coupling beam specimens, with seven reinforced concrete sections and one composite section, were tested under cycles of push-pull action. Characteristics of the specimens include moderate shear span ratio in the range of 2.5-3.5, high main reinforcement ratio at 3-4% and small to large stirrup spacing with 90- degree hooks. All the reinforced concrete specimens failed in a brittle manner. Displacement ductility of specimens with large stirrup spacing (${\geq}$140 mm) is in the range of 3 to 5. Seismic performance of the specimens is also examined using the ultimate drift angle and the amount of energy dissipated. Correlating the test data, an empirical relationship is proposed to estimate the ultimate drift angle of a class of coupling beams considered in the study not designed for ductility.

• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.119-122
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• 2001

This paper deals with new type of active magnetic bearing (AMB) for the linear motors. We adopted optical sensing mechanism for the gap sensing. Using the laser and the PSD (Position Sensitive Device), the absolute rotor position is obtained independent of the profile of the guide rail. With this measurement, the rotor can be controller to follow the straight beam of the laser. Another advantage of optical sensing mechanism might be the elimination of the possible interference between the proximity sensor and the electro-magnet. By adopting the push-full actuating mechanism, the bearing stiffness is increased near the equilibrium position. For the simplicity, distributed control system is constructed. Eight independent PID control algorithm is used with the full order observer. Several simulation md test results are presented.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.105-108
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• 2004

In general, the nonlinear behavior of composite structures composing of steel and concrete is analyzed on the basis of the assumption of the perfect bond actions in steel-concrete interface in which the interface slip or separation is not allowed. The assumption is based on the fact that the full interface bond behavior is provided with the mechanical connectors of studs. However, since the number and spacing of the studs are determined by the stress resultants calculated in the interface area, the interface analysis is required to evaluate the stress resultants. This paper describes the nonlinear steel-concrete interface behavior considering the two interface failure mechanisms of slip and separation. Elastoplastic constitutive relation is developed. thru the formulation framework using the two energy dissipation mechanisms. As the result, the steel plate push-out tests sandwitched between concrete blocks are analyzed and compared with the test results with which the good agreements are observed.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.325-328
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• 2006

Joint structures of composite truss bridges can have the same details for the connection between diagonal members and upper concrete slab as the connection between diagonal members and lower concrete slab. Adequate connection details should be decided according to design codes, constructibility, and economical evaluation. It is necessary to clarify the design check items and load transferring mechanism because combined external loads on composite truss bridges are concentrated at the joints. Joints with gusset plates and stud connectors are applied and complicated joint details may arise some problems in construction. This paper deals with experimental evaluation of the joints in composite truss bridges and proper design provisions were investigated to enhance the details. Push-out test specimens with group studs were fabricated and the effects of grouping and bent studs were studied.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.136-137
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• 2006

Crack initiation and short crack propagation was studied on the polished notched surfaces of Cr-Mo prealloy sintered steels with 7.35 $g.cm^{-3}$ sintered density. An ultrasonic resonance test system operating in push-pull mode at 20 kHz and R=-1 was used. It showed that crack initiation took place in several places, small cracks growing oriented to the local pore structure rather than to stress orientation. Their growth rate is markedly higher than the corresponding one of long cracks. Finally, several microcracks join to form a dominant crack.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.202-209
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• 2003

We succeeded to build a cost effective assistance robotic arm with a compact and lightweight body. The robotic arm has three joints, and the tip of robotic arm to install tools consists of a closed link mechanism, which consisted of two actuators and several links. The robotic arm has been made possible by the use of actuators typically used in radio control devices. The controller of the robotic arm consists of a single chip PIC only. The robotic arm has a friendly user interface, as the operators are aged and disabled in most cases. The operator can manipulate the robotic arm by voice commands or by pressing a push button. The robotic arm has been successfully prototyped and tested on an elderly patient to assist with eating. The results of field test were satisfactory.

• Steel and Composite Structures
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• v.17 no.5
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• pp.623-639
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• 2014

Due to recent advancements in the area of Artificial Intelligence (AI) and computational intelligence, the application of these technologies in the construction industry and structural analysis has been made feasible. With the use of the Adaptive-Network-based Fuzzy Inference System (ANFIS) as a modelling tool, this study aims at predicting the shear strength of channel shear connectors in steel concrete composite beam. A total of 1200 experimental data was collected, with the input data being achieved based on the results of the push-out test and the output data being the corresponding shear strength which were recorded at all loading stages. The results derived from the use of ANFIS and the classical linear regressions (LR) were then compared. The outcome shows that the use of ANFIS produces highly accurate, precise and satisfactory results as opposed to the LR.

• Journal of Advanced Engineering and Technology
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• v.11 no.4
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• pp.279-285
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• 2018

A shear connection between the steel beam and concrete slab determines the stability of composite beams. An extensive numerical study to evaluate the resistance of the shear connection in a solid slab at high temperature was conducted. Three-dimensional thermo-mechanical finite element models were developed using a dynamic explicit method and concrete damaged plasticity model. Temperature-dependent plasticity parameters of the concrete model were proposed, and the accuracy of the developed model was obtained against experimental data. This investigation has revealed that a stud shearing failure occurs regardless of temperatures, and its shearing location changes in accordance with a rise in temperature. A new strength reduction formula has been presented to estimate the resistance of the shear connection at high temperatures.