• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.101-108
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• 2013

Ara Canal is the first artificial canal in Korea that connects the Han River and the Yellow Sea. Due to mixture of waters with different salinity and water quality, complicated hydrodynamic and water quality distributions are expected to occur inside the canal. An integrated hydrodynamic and water quality modeling system was developed using the 3 dimensional hydrodynamic model, EFDC (Environmental Fluid Dynamics Code) and the water quality model WASP (Water Quality Analysis and Simulation Program). According to the modeling results, BOD, TN, TP and Chl-a concentrations inside the canal were lower at the West Gate side than the Han River side since influent concentrations of the West Gate side are significantly lower. Chemical stratification due to salinity difference were more evident at the West Gate side as vertical salinity difference were more pronounced in this area. On the other hand, Chl-a concentrations showed more pronounced vertical distribution at the Han River side as Chl-a concentrations were higher in this area. It was notable that Dissolved Oxygen concentrations can be lower than 2 mg/L occasionally in the middle part of the canal. While major factor affecting DO concentrations in the canal are inflows via both gates, the other important factor was found to be BOD decay in the canal due to extended hydraulic residence time. This study can be used to predict hydrodynamic conditions and water quality in the canal during the year and thus can be helpful in the development of gate operation method of the canal.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.51-63
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• 2002

This paper presents a hybrid control strategy for seismic protection of a benchmark cable-stayed bridge, which is provided as a testbed structure for the development of strategies for the control of cable-stayed bridges. This benchmark problem considers the cable-stayed bridge that is scheduled for completion in Cape Girardeau, Missouri, USA in 2003. Seismic considerations were strongly considered in the design of this bridge due to the location of the bridge in the New Madrid seismic zone and its critical role as a principal crossing of the Mississippi river. Based on detailed drawings of this cable-stayed bridge, a three-dimensional linearlized evaluation model has been developed to represent the complex behavior of the bridge. A set of eighteen evaluation criteria has been developed to evaluate the capabilities of each control strategy. In this study, a hybrid control system is composed of a passive control system to reduce the earthquake-induced forces in the structure and an active control system to further reduce the bridge responses, especially deck displacements. Conventional base isolation devices such as lead rubber bearings are used for the passive control design and Bouc-Wen model is used to simulate the nonlinear behavior of these devices For the active control design, ideal hydraulic actuators are used and on $H_2$/LQG control algorithm is adopted. Numerical simulation results show that the performance of the proposed hybrid control strategy is quite effective compared to that of the passive control strategy and slightly better than that of the active control strategy. The hybrid control method is also more reliable than the fully active control method due to the passive control part. Therefore, the proposed hybrid control strategy can effectively be used to seismically excited cable-stayed bridges.

• Steel and Composite Structures
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• v.39 no.1
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• pp.109-123
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• 2021

This research endeavor intends to use the implicit finite element method to investigate the structural response of steel shear walls with partial plate-column connection. To this end, comprehensive verification studies are initially performed by comparing the numerical predictions with several reported experimental results in order to demonstrate the reliability and accuracy of the implicit analysis method. Comparison is made between the hysteresis curves, failure modes, and base shear capacities predicted numerically using ABAQUS software and obtained/observed experimentally. Following the validation of the finite element analysis approach, the effects of partial plate-column connection on the strength and stiffness performances of steel shear wall systems with different web-plate slenderness and aspect ratios under monotonic loading are investigated through a parametric study. While removal of the connection between the web-plate and columns can be beneficial by decreasing the overall system demand on the vertical boundary members, based on the results and findings of this study such detachment can lower the stiffness and strength capacities of steel shear walls by about 25%, on average.

• The Journal of Engineering Geology
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• v.20 no.4
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• pp.391-399
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• 2010

We performed a hydraulic analysis based on the wetness index of talus slopes in Jungsun, Gangwon province. We estimated the relation between the degree of development of the temporary water system, and talus topography and distribution. We also assessed the distribution of talus based on a map of the wetness index. We divided areas of tallus into stable and unstable types, and estimated the size, distribution and shape-preferred orientation of clasts. We performed numerical simulations of rockfall events to assess the optimum location of rockfall barriers upon talus slopes.

• Journal of Drive and Control
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• v.12 no.2
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• pp.39-48
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• 2015

In order to control the actuators of hydraulic machinery such as excavators, various control valves are typically assembled in a single block. Such a control block is called a main control valve(MCV). In this paper, we analyzed the working principle and the particular purpose of the design of all valves included in the MCV system. To Examine the reliability of the analysis model, the pressure drop of the MCV at each port was measured. The authors developed an analytical model of the control valve(main spool, load poppet, pressure relief, make up, and regeneration). The authors considered the notch shape of the spool while developing the analytical models of the main spool valve. Most importantly, at the stage before the analysis model was applied in the design tuning, the reliability was ensured by comparing the analysis results with the test results. This paper showed a process of developing an analysis model that can be utilized in the design and tuning stages.

• Journal of Drive and Control
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• v.15 no.2
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• pp.38-45
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• 2018

In this study, the theory of fluid mechanics and dynamics is used to build a mathematical model for a three-stage flow control valve. The significance of the study is that the mathematical model can easily be used to study the effect of different design parameters on the performance of the valve. The geometry of the valve and the properties of the fluid were used in this study to determine the variation in the performance of the valve when varying the magnetic force on the pilot spool. While a linearization technique is not used to solve the developed model, the solution of the mathematical model is found in the time domain by simulation of the equations using a software package. The results indicate that if the developed mathematical model is solved for the different values of magnetic force, the valve behaves linearly; the valve is thus called the proportional flow control valve.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.6
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• pp.69-76
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• 2013

This paper presents the development of the FCF method for the manufacturing of final products using numbers related to the minimum amount of work. The utilized product is a drum clutch, which is part of the transmission of an automobile. A double acting press is secured first and a prediction of the forming load on the practical material is made through an experiment with a plasticine model. Also, a finite element simulation using product shape and properties is performed, as well as a press experiment. A double acting press is manufactured that is suitable for a double acting experiment with a conventional hydraulic press(200 tons). A peripheral device for the press is additionally designed for experimental purposes. And, the press has as its essential points the drive speed, stroke control, etc., all of which influence the forming and is modified. Especially, a laser system is used for velocity measurement of two punches. The forming load of a practical material is predicted in order to derive a forming load formula for cold conditions on the basis of approximate similarity theory. Finite element analysis of the relative velocity ratio(RVR), etc., for most suitable flow defect(unfilling, etc.) prevention is achieved as well. The results are verified through a press experiment.

• Steel and Composite Structures
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• v.28 no.1
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• pp.1-11
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• 2018

In this paper, local ratcheting behavior of 1045 steel plates with circular cutout was investigated. Experimental tests were carried out by a Zwick/Roell HB 100 servo hydraulic machine. In order to measure the local strain at notch root, a data acquisition system with strain gauge was used. Various notch diameters and distances of strain gauges mounted from the notch root were found influential in the magnitude of local ratcheting strain. It was found that the local maximum principal stress plays a crucial role in increasing the local plastic deformation. Numerical simulation was done by ABAQUS software using nonlinear isotropic/kinematic hardening model. Material parameters of hardening model were attained from several stabilized cycles of flat specimens subjected to symmetric strain cycles. The nonlinear kinematic hardening model along with the Neuber's rule was employed to assess local ratcheting at the notch root of steel plates. The results of the numerical simulations agreed closely with those measured values in this study. Both ratcheting progress and mean stress relaxation occurred simultaneously at the notch root.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.12
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• pp.1305-1311
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• 2004

This study presents a mathematical model and a sliding mode observer of the injection system for common rail diesel engines. The injector model consists of three subsystems: the actuator subsystem, the mechanical subsystem, and the hydraulic subsystem. In the actuator subsystem, the constitutive relations of piezoelectricity are used to model the actuator made up of piezoelectric material. Based on the proposed model, the observer estimates the injection rate and injection timing, and can play a vital role of sensorless control of fuel injection in the near future. The sliding mode theory is applied to the observer design in order to overcome model uncertainties. The injector model and observer are evaluated through the injector experiments. The simulation results of the injector model are in good agreement with the experimental data. The sliding mode observer can effectively estimate the injection timing and the injection rate of the injector.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.38-47
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• 2005

In this paper, a regenerative braking algorithm is proposed to make the maximum use of the regenerative braking energy for an independent front and rear motor drive parallel HEV. In the regenerative braking algorithm, the regenerative torque is determined by considering the motor capacity, motor efficiency, battery SOC, gear ratio, clutch state, engine speed and vehicle velocity. To implement the regenerative braking algorithm, HEV powertrain models including the internal combustion engine, electric motor, battery, manual transmission and the regenerative braking system are developed using MATLAB, and the regenerative braking performance is investigated by the simulator. Simulation results show that the proposed regenerative braking algorithm contributes to increasing the battery SOC, which recuperates 60 percent of the total braking energy while satisfying the design specification of the control logic. In addition, a control algorithm which limits the regenerative braking is suggested by considering the battery power capacity and dynamic response characteristics of the hydraulic control module.