• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.985-993
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• 2015

Free-piston Stirling engines (FPSEs) have attracted much attention in the renewable energy field as a key device in the conversion from thermal to mechanical energy, and in the recycling of waste energy. Traditional Stirling engines consist of two pistons that are connected by a mechanical link, while FPSEs are formed as a vibration system by connecting each piston to a spring without a physical link. To ensure the correct design and control of operations, this requires elaborate dynamic-performance predictions. In this paper, we present the performance-prediction methodology using a linear and nonlinear dynamic analytical model considering the external load of FPSEs. We perform linear analyses to predict the operating point of the engine using the root locus technique. Using nonlinear analysis, we also predict the amplitude of pistons by performing numerical integration considering both the linear and nonlinear damping terms of the external load. We utilize the predicted dynamic behavior to predict the engine performance. In addition, we compare the experiment results and existing model predictions for RE-1000 to verify the reliability of the analytical model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.659-666
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• 2006

Servo-motors are used as key components of automated system by performing precise motion control as accurate positioning and accurate speed regulation in response to the commands from computers and sensors. Especially, the linear brushless servo-motors have numerous advantages over the rotary servo motors which have connection with the friction induced transfer mechanism such as ball screws, timing belts, rack/pinion. This paper proposes an estimation method of unknown motor system parameters using the informations from the sinusoidal driving type linear brushless DC motor dynamics and outputs. The estimated parameters can be used to tune the controller gain and a disturbance observer. In order to meet this purpose high performance Digital Signal Processor, TMS320F240, designed originally for implementation of a Field Oriented Control(FOC) technology is adopted as a controller of the liner BLDC servo motor. Having A/D converters, PWM generators, rich I/O port internally, this servo motor application specific DSP play an important role in servo motor controller. This linear BLDC servo motor system also contains IPM(Intelligent Power Module) driver and hail sensor type current sensor module, photocoupler module for isolation of gate signals and fault signals.

• Journal of Korean Society on Water Environment
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• v.35 no.6
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• pp.580-588
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• 2019

The flow of the middle and downstream of the Yeongsan River is stagnant by two weirs of Seungchon and Juksan and the estuary dam and maintained in freshwater. In this study, the Environmental Fluid Dynamics Code-National Institute of Environment Research(EFDC-NIER) model was applied to the Yeongsan River to simulate water flow, temperature, and salinity stratification. The EFDC-NIER model is an improved model which can simulate multi-functional weirs operation, multiple algal species, and the vertical movement mechanism of algal based on the EFDC model. The simulation results for the water level, water temperature, velocity, and salinity reproduced the observed values well. The mean absolute error(MAE) of the model calibration in the annual variations of the water level was 0.1-0.3 m, water temperature was 0.8-1.7 ℃, velocity was 4.5-7.1 cm/sec, and salinity was 1.5 psu, respectively. In the case of scenario simulation for the full opening of the estuary dam, the water level of the estuary dam was directly impacted by the tide so it was predicted to rise - 1.35 m to 0.2 m on average sea level. The velocity was also predicted to increase from 2.7 cm/sec to 50.8 cm/sec, and the flow rate to increase from 53 ㎥/sec to 5,322 ㎥/sec.

• Journal of the Korea Computer Industry Society
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• v.7 no.5
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• pp.583-590
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• 2006

BT technology, medical treatment engineering technology is offering important role and grow by creative technology. Specially, bone fracture treatment can achieve very important role in research of bone, physiology and dynamics of bone is very useful patient's diagnostic and treatment in presence at a sickbed. <중략>Furthermore embedded base of in administration aspect as well as if supersonic waves curer is treatment innocuously and without invasion very efficient tell. If apply supersonic waves in bone fracture treatment, can reduce curer about 40%. Operation frequency through bone fracture treatment supersonic waves curer of embedded base designs and manufactured 1m Hz, 1.2mHz, 1.3mHz, 1.4mHz, supersonic waves origination that have 1.5mHz's tranducer, and embodied protocol in PDA base in this research, and did so that is interfaced to general PC. If is using but supplement research water that see clinically by diagnosis in city, is seen to become convenient medical treatment assistance mounting to bone fracture patient's treatment and courtesy call. Specially, tried to approach basic form after modeling processing if may be applied variously to physiotherapy, orthopaedics patient who gouge late, and study standardization special quality little more.

• Journal of the Economic Geographical Society of Korea
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• v.19 no.1
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• pp.122-142
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• 2016

This paper examines the implications of North Korea's Special Economic Zone (SEZ) strategy since the early 1990s in terms of the shifts in both North Korea's economic system and geopolitical order on the Korean peninsula. Specifically, it analyzes the shifts in North Korea's SEZ policy in three different aspects-North Korea's unique territorial logic, stress on decentralization, and comparison with Chinese reform and opening-up. Based upon this analysis, this paper criticizes a linear approach to understand North Korea's economic transformation from isolation to opening-up, and explores the dynamics of North Korea SEZ strategy in various dimensions. It contends that North Korea's SEZ strategy is neither an inevitable choice from economic difficulty nor an adoption of Chinese model of reform and opening up. Rather this paper focuses on the geopolitical logic and local development imperatives underlying SEZ strategy.

• Journal of Hydrogen and New Energy
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• v.31 no.4
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• pp.387-394
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• 2020

A parametric study of a 2.5 kW class propeller type micro hydraulic turbine was performed. In order to analyze the internal flow characteristics in the hydraulic turbine, three dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used and the hexahedral grid system was used to construct computational domain. To secure the reliability of the numerical analysis, the grid dependency test was performed using the grid convergence index method based on the Richardson extrapolation, and the grid dependency was removed when about 1.7 million nodes were used. For the parametric study, the axial distance at shroud span (L) between the inlet guide vane and the runner, and the inlet and outlet blade angles (β₁, β₂) of the runner were selected as the geometric parameters. The inlet and outlet angles of the runner were defined in the 3 spans from the hub to tip, and a total of 7 geometric parameters were investigated. It was confirmed that the outlet angles of the runner had the most sensitive effect on the power and efficiency of the micro hydraulic turbine.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.681-689
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• 2012

In this study, we performed a simulation of the dynamic response of a multibody system to calculate the tension acting on wire ropes connecting floating cranes and a heavy cargo such as a Giga Block weighing over 5000 tons when the cargo is salvaged using parallel connected floating cranes. In this simulation, we supposed that the motion of the floating cranes, barge ship, and heavy cargo has 6 degrees of freedom and that the interaction is determined by constraints among them. In addition, we considered independent hydrostatic and hydrodynamic forces as external forces acting on the floating cranes and barge ship. The simulation result can be a basis for verifying the safety of construction methods in which heavy cargo is salvaged by parallel connected floating cranes, and it can also be used to guide the development of such construction methods.

• Korean Journal of Construction Engineering and Management
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• v.7 no.6
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• pp.141-150
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• 2006

As the law on the private sector investment in social infrastructure was amended in January of 2005, the government is aggressively promoting BTL projects but many trials and errors and problems are occurring. Especially, the Value-For-Money evaluation conducted by the responsible agencies to judge the appropriateness of the project found there was a conspicuous difference between the computed cost and the final contract sum. Accordingly, this study is aimed to grasp the problems in the current Value-For-Money evaluation and to improve it in order to proceed with BTL projects efficiently. To achieve this, through a relative comparison to the final contract sum, a clear standard for the items of Value-For-Money evaluation was presented and thus, a model that can ensure accuracy in computing the Value-For-Money was established so that a delay in negotiations can be avoided. If the Value-For-Money evaluation established in this study is used in assessing the appropriateness of unit prices for BTL projects for education facilities, a reasonable result can be expected to be drawn in selection and negotiations with contractors, and maintenance and Post-Operation-Evaluation(POE) of education facilities as well.

• Korean Institute of Interior Design Journal
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• no.11
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• pp.57-63
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• 1997

In the early 20'c, scientific thoughts make a change the absolute and separate concept of space-time into relative concept of continual entity; a kind of ideal world. It suggests that the meaning of geometry as absolute truth with which has endowed human beings would changed to a relative meaning of accumulation in intellectual work on 'nature'. This cognitive changes appeared into absolute arts in 20'c like Cubism, Superematism or Constructivism. De Stijl movement which had recepted the relative concepts like Einstein's 'theory of relativity' as a developed thought from Newton-Cartesian cognition on the world. Abstration would be adequate method for expressing the dynamics and interrelationship between forms and for giving values to indivisual elements in a compositiov. This method had appeared Modern architectural form, as a common framework. The expression characteristics of geometrical design in Deconstructive and Experimental architecture were summerized in four features through the results of the analysis. First, the relation of architectural element and intertextuality is expressed in discontinuation of context and refusal of functional building. Second, the concept of trace expresses as connection of place, decomposing of excavation of trace, trace of axis, trace of fragments. Third, anti-gravity expression is there to express of open cubic, to outgrow of rectangular system, to outgrow of volume, to separate of ground connectiov. Fourth, the complex composition of abstracted geometric form is these to abstracted geometry about indefinite shape, to layer through the overlap and collage, to de-meaning and amusement of form through the pursuit of uncertainty, to indeterminate of formal meaning through operation and composition of similar form cause to the diverse of meaning.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.135-146
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• 2013

This paper presents a feedforward control algorithm for the EGR and VGT systems of passenger car diesel engines. The air-to-fuel ratio and boost pressure are selected as control indicators and the positions of EGR valve and VGT vane are used as control inputs of the EGR and VGT controller. In order to compensate the non-linearity and coupled dynamics of the EGR and VGT systems, we have proposed a non-linear model-based feedforward control algorithm which is obtained from static model inversion approach. It is observed that the average modeling errors of the feedforward algorithm is about 2% using stationary engine experiment data of 225 operating conditions. Using a feedback controller including proportional-integral, the modeling error is compensated. Furthermore, it is validated that the proposed feedforward algorithm generates physically acceptable trajectories of the actuator and successfully tracks the desired values through engine experiments.