• Steel and Composite Structures
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• v.17 no.4
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• pp.371-386
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• 2014

This paper presents a tri-linear restoring force model based on the test results of 12 circular RC columns strengthened by CFRP strips under low cyclic loading. The pre-stress of CFRP strips and axial load ratio of specimens are considered as the affect parameters of the proposed model. All essential characteristics of the hysteretic behavior of the proposed model, including the hysteretic rules, main performance points, strength degradation, stiffness degradation and confinement effects are explicitly analyzed. The calculated results from the proposed model are in good agreement with the experimental results, which shows that the recommended model can be reliably used for seismic behavior predictions of circular RC columns strengthened by pre-stressed CFRP strips.

• Computers and Concrete
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• v.10 no.2
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• pp.121-133
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• 2012

Structures suffer from damages in their lifetime due to time-dependant effects, such as fatigue, creep and shrinkage, which can be expressed by concrete strains. These processes could be seen in the context of strain estimation of pre-stressed structures in two phases by using numerical methods. Their aim is checking and validating existing code procedures in determination of deformations of pre-tensioned girders by solving a system of nonlinear equations with strains as unknown parameters. This paper presents an approach based on the Newton-Raphson method for obtaining the stresses and strains in middle span section of pre-stressed girders according the equilibrium state.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.255-261
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• 2000

Tube bending is one of the conventional manufacturing process. Recently, tube bending was highlighted in automotive industry by hydroforming. Tube hydroforming process is divided into pre-bending process and hydroforming process. It's initial state is very important in die cavity of first hydroforming process. So tube bending is important factor of the hydroforming process. In this paper, two pre-bending simulations, by a rotary draw bending machine and a bend die. This paper presents the simulation results in pre-bending process that is used to form an automotive part, tie-bar.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.162-167
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• 2004

The low velocity impact characteristics of composite laminate curved beams are investigated to increase damage tolerance and reduce the deflection. Drop weight impact tests of the composite curved beam were performed with respect to pre-load, then the damage after impact was measured by macrography. Also, finite element analyses were performed using ABAQUS to investigate the stress state of composite curved beam with respect to pre-load and impact. From the investigation, it was found that pre-load of the composite curved beams had much influence on impact damage of the curved beam, which showed good agreement with the experiment results.

• KCI Concrete Journal
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• v.12 no.1
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• pp.69-77
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• 2000

The reinforced concrete(RC) flexural members strengthened with steel plate/CFS at soffit have initial stresses and strains in reinforcements and concrete caused by the service loads at the time of retrofitting works. These initial residual stresses and strains of strengthened beams may affect the flexural performance of the rehabilitated beams. The objective of this study is to evaluate and verify the effectiveness of rehabilitation by external bonded steel plates and CFS to the tension face of the beams under three conditions of pre-loading. Thirteen beam specimens are tested and analyzed. Main test parameters are pre-loading conditions, strengthening materials and reinforcement ratio of specimens. The effect of test parameters on the strengthened beams is analyzed from the maximum load capacity, load-deflection relationship, state of stress of the materials. crack propagation phase, and failure modes. Both test results and design formulas of ACI Code provisions are compared and evaluated.

• Research in Mathematical Education
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• v.23 no.2
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• pp.113-133
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• 2020

Pre-service teachers (PST) are students who are developing their mindset, persistence, instructional practices, and perception of tasks from two perspectives: as current students and as future teachers. As part of a larger study with PSTs engaged in a mindset intervention, this study quantitatively investigated PSTs mindset and persistence. During professional development (PD), PSTs engaged in multiple strategies (MS) tasks that promoted changes to PSTs mindset and persistence. PSTs' mindset pre- and post- PD were categorized after attending at least 4 interventions as fixed, mixed, or growth using the theory of intelligence, and their persistence as high or low using the Grit-S. Changes in categorization were noticed and explored for reasons of what could be done to make mindset interventions more effective such as consistently using challenging mathematics tasks with more open ended answers and focusing on discussion based mathematical lessons.

• Korean Journal of Metals and Materials
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• v.49 no.10
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• pp.790-796
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• 2011

To reduce the heat released during intermetallic reaction, Ni-50at%Al powder compact has been previously annealed at several conditions before the reaction. The effects of the pre-annealing conditions on the reaction synthesis process have been investigated. Experimental results show that the heat released during the reaction synthesis decreased proportionally with increase of the pre-annealing temperature and duration time. The reaction duration period was significantly increased when the intermetallics were formed in the powder compact during the pre-annealing. This was attributed to the fact that the reaction occurred by solid-state diffusion between the un-reacted elemental atoms and that the $NiAl_3$ phase formed predominantly during pre-annealing.

• Journal of the Korea Society of Computer and Information
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• v.16 no.5
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• pp.127-134
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• 2011

A finite state machine was designed to control user's gaze on the screen when the user is monitoring the. It consists of a set of situations where pupils are gazed and a set of states which decide the gaze on a screen or sleeping. The states were especially classified into main states, pre-states and potential states. The machine uses the situation history, which decide current state using continuous previous situation and current situation, and improves the accuracy to control the gaze on a screen. We implemented the machine with the data which were get using a pupil detection method, and tested the verification of the system with monitoring operations. The experimentation using the method which get date from real images shows advantage of decision whether it is temporary gaze or long-term gaze.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1229-1232
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• 2004

The ratio of optimized concentration on optical characteristics for phase-separated composite organic films (PSCOF) liquid crystal display is 30% of pre-polymer (NOA65) and 70% of ferroelectric liquid crystal (Felix). The layer structure in ferroelectric liquid crystal cell made by 30% NOA65 and 70% Felix materials is tilt-bookshelf layer structure. The angle of tilt-bookshelf structure are 17$^{\circ}$, 12$^{\circ}$ which are almost same of tilt angle of ferroelectric liquid crystal in Sm $C^{\ast}$ phase. We know that this result is from compensating the layer buckling. In this paper, we will discuss the effect of layer structure in PSCOF cell on ratio of concentration between pre-polymer and liquid crystal by x-ray measurements. We believe that technology of PSCOF is a good solution to solve the problems of align-defect and mechanical shock for future TV application and plastic LCD.

• Macromolecular Research
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• v.11 no.1
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• pp.53-61
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• 2003

A molecular-thermodynamic model is developed for the salt-induced protein precipitation. The protein molecules interact through four intermolecular potentials. An equation of state is derived based on the statistical mechanical perturbation theory with the modified Chiew's equation for the fluid phase, Young's equation for the solid phase as the reference system and a perturbation based on the protein-protein effective two body potential. The equation of state provides an expression for the chemical potential of the protein. In a single protein system, the phase separation is represented by fluid-fluid equilibria. The precipitation behaviors are simulated with the partition coefficient at various salt concentrations and degree of pre-aggregation effect for the protein particles. In a binary protein system, we regard the system as a fluid-solid phase equilibrium. At equilibrium, we compute the reduced osmotic pressure-composition diagram in the diverse protein size difference and salt concentrations.