• Smart Structures and Systems
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• v.12 no.3_4
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• pp.345-361
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• 2013

Locating and assessing the severity of damage in large or complex structures is one of the most challenging problems in the field of civil engineering. Considering that the wavelet packet transform (WPT) has the ability to clearly reflect the damage characteristics of structural response signals and the artificial neural network (ANN) is capable of learning in an unsupervised manner and of forming new classes when the structural exhibits change, this paper investigates a multi-stage structural damage diagnosis method by using the WPT and ANN based on "energy-damage" theory, in which, the wavelet packet component energies are first extracted to be damage sensitive feature and then adopted as input into an improved back propagation (BP) neural network model for damage diagnosis in a step by step mode. To validate the efficacy of the presented approach of the damage diagnosis, the benchmark structure of the American Society of Civil Engineers (ASCE) is employed in the case study. The results of damage diagnosis indicate that the method herein is computationally efficient and is able to detect the existence of different damage patterns in the simulated experiment where minor, moderate and severe damages corresponds to involving in the loss of stiffness on braces or the removal bracing in various combinations.

• Journal of Auto-vehicle Safety Association
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• v.11 no.2
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• pp.23-28
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• 2019

This paper presents an optimal performance of rear wheel steering vehicle for maneuverability. The maneuverability of vehicle is evaluated in terms of yaw rate, body slip angle and driver input. The maneuverability of vehicle can be improved by rear wheel steering system. To obtain optimal performance of rear wheel steering vehicle, the optimal control history is designed. The high dimensional trajectory optimization problem is solved by formulating a quadratic program considering rear wheel steer input. To evaluate handling performance 7 degree-of-freedom vehicle model with actuation sub-models is designed. A step steer test is conducted to evaluate rear wheel steering vehicle. A response time, a TB factor, overshoot, and yaw rate gain are investigated through objective criteria, assessment webs. The handling performance of vehicle is evaluated via computer simulations. It has been shown from simulation studies that optimal controlled rear wheel steering vehicle provides improved performance compared to others.

• Journal of The Korean Association For Science Education
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• v.25 no.3
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• pp.400-410
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• 2005

According to the cognitive conflict process model, student anxiety factor is known to have both positive and negative effects on student response behaviors in a conflict situation for conceptual change learning. However, there is little research that reveals what type of anxiety, either constructive or destructive, is related when conducting step-by-step experiments to resolve cognitive conflicts. This study attempted to learn the characteristic of explanatory hypothesis according to anxiety type after conducting five step-by-step experiments related to action and reaction concept. Results found that students who belonged to the types of 'conviction in logical misconception', 'insisting on additional variables', and 'reasonable modification' suggested explanatory hypothesis close to physical nature. On the other hand, those who showed the other five types of anxiety ('compatible predictions', 'dependence on others', 'fusion of past experience', 'lack of confidence', and 'conflict with past experience') suggested temporary supported hypothesis or simple explanatory hypothesis according to student intuition and simple observation. These results indicate that students in the above-mentioned five categories need more external interactions with instructors based on the type of anxiety related to student behavior. In addition, the results present student characteristics which instructors should be more attentive to when using step-by-step experiments to resolve cognitive conflicts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.4745-4750
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• 2011

A HIL(hardware-in-the-loop) system was established and the simulation was carried out to determine whether the system operates normally. The system consists of turbocharger test bench, HIL platform with real time S/W and DAQ, and engine model using Matlab/Simulink. In the simulation the supplied fuel rate is changed step-by-step from 1.8944 kg/h to 4.7360 kg/h. The change of air-fuel ratio is analyzed and observed whether the air-fuel ratio follow the target air-fuel ratio 32. When the supplied fuel rate is changed, the air-fuel ratio is converged to the target air-fuel ratio after about 20 seconds. And the vane duty ratio of turbine and the boost pressure of compressor are also changed properly. Therefore this HIL system can be used to develop the new turbocharger and improve the performance of the modified turbocharger.

• The Korean Journal of Medicine
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• v.99 no.2
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• pp.84-95
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• 2024

In Harrison's Principles of Internal Medicine, human understanding is emphasized as one of three necessary characteristics that a physician must have. Inflammation, which is caused by inflammatory inducers (inf-ids), is a fundamental feature of disease at the cellular and molecular levels. Inflammation protects the body, but excessive or prolonged inflammation can be damaging and can cause disease. Humans are repeatedly exposed to external and internal environmental factors that generate inf-ids throughout their lives. External environmental factors include microbial and non-microbial inf-ids, as well as stressors that inevitably arise during social interactions. Internal environmental factors include the adaptive physiological response that is present from birth. Inf-ids may also be produced by the four-step habit loop, which consists of a cue (e.g., stressor), emotions, routine act (adaptive response), and a reward. Immune cells in the circulatory system and in tissues may have positive and negative effects in inflammatory responses. However, low-grade inflammation may be difficult to detect. We propose a model of disease development that integrates external and internal environmental factors from the perspective of human understanding.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.4
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• pp.106-113
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• 1997

Dynamic loading of structures often causes excursions of stresses well into the inelastic range, and the influence of the geometric changes on the dynamic response is also significant in many cases. Therefore, both material and geometric nonlinearity effects should be considered in case that a dynamic load acts on the structure. A structure in a nuclear power plant is a structure of importance which puts emphasis on safety. A nuclear container is a pressure vessel subject to internal pressure and this structure is constructed by a reinforced concrete or a pre-stressed concrete. In this study, the material nonlinearity effect on the dynamic response is formulated by the elasto-viscoplastic model highly corresponding to the real behavior of the material. Also, the geometrically nonlinear behavior is taken into account using a total Lagrangian coordinate system, and the equilibrium equation of motion is numerically solved by a central difference scheme. The constitutive relation of concrete is modeled according to a Drucker-Prager yield criterion in compression. The reinforcing bars are modeled by a smeared layer at the location of reinforcements, and the steel layer model under Von Mises yield criteria is adopted to represent an elastic-plastic behavior. To investigate the dynamic response of a nuclear reinforced concrete containment structure, the steel-ratios of 0, 3, 5 and 10 percent, are considered. The results obtained from the analysis of an example were summarized as follows 1. As the steel-ratio increases, the amplitude and the period of the vertical displacements in apex of dome decreased. The Dynamic Magnification Factor(DMF) was some larger than that of the structure without steel. However, the regular trend was not found in the values of DMF. 2. The dynamic response of the vertical displacement and the radial displacement in the dome-wall junction were shown that the period of displacement in initial step decreased with the steel-ratio increases. Especially, the effect of the steel on the dynamic response of radial displacement disapeared almost. The values of DMF were 1.94, 2.5, 2.62 and 2.66, and the values increased with the steel-ratio. 3. The characteristics of the dynamic response of radial displacement in the mid-wall were similar to that of dome-wall junction. The values of DMF were 1.91, 2.11, 2.13 and 2.18, and the values increased with the steel-ratio. 4. The amplitude and the period of the hoop-stresses in the dome, the dome-wall junction, and the mid-wall were shown the decreased trend with the steel-ratio. The values of DMF were some larger than those of the structure without steel. However, the regular trend was not found in the values of DMF.

• Korean Journal of Agricultural and Forest Meteorology
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• v.15 no.4
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• pp.312-319
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• 2013

Our understanding of the sensitivities of crop responses to changes in carbon dioxide, temperature, and water is limited, which makes it difficult to fully utilize crop models in assessing the impact of climate change on future agricultural production. Genetic coefficients of CERES-Barley model for major domestic cultivars in South Korea (Olbori at Suwon, Albori at Milyang, Saessalbori at Iksan, and Samdobori at Jinju) were estimated from the observed data for daily weather and field trials for more than 10 years by using GenCalc in DSSAT. Data from 1997-2002 annual crop status report (Rural Development Administration, RDA) were used to validate the crop coefficients. The sitecalibrated CERES-Barley model was used to perform crop growth simulation with the 99 treatments of step change combinations in temperature, precipitation and carbon dioxide concentration with respect to the baseline climate (1981-2010) at four sites. The upper boundary corresponds to the 2071-2100 climate outlook from the RCP 8.5 scenario. The response surface of grain yield showed a distinct pattern of model behavior under the combined change in environmental variables. The simulated grain yield was most sensitive to $CO_2$ concentration, least sensitive to precipitation, and showing a variable response to temperature depending on cultivar. The emulated impacts of response surfaces are expected to facilitate assessment of projected climate impacts on a given cultivar in South Korea.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.4
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• pp.359-365
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• 2006

Recently generated natural disaster of rainfall is transformed into nationwide generate form from a specific region of generated form that damages are steadily growing. such natural disaster lead to much influence such as socioeconomic, financial, physical and casualties etc, therefore model collection can be a step required establishment of systematically management foundation and offer of systematic solved plan. this study proposed to analyze and arrange pattern of disaster and systems designed plan and establishment further scientific, prompt service of disaster. with GIS technique for decision-making offer the necessary preliminary data. also, each city have orthophoto and digital elevation model that analyze real topography and situation. with establish management system in order to carry out appropriate service of disaster management and establish realistic management system. system had established that OpenGL make three dimensional illustrate scale image data and digital elevation model therefore a module of section analysis developed way to illustrate and to analyze topography and longitudinal section in screen.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.405-411
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• 2012

This paper deals with direct torque control of an induction motor (IM) with constant switching frequency. The desired torque is obtained from the speed controller which is designed using the IP controller. Decoupling control of torque and flux is developed based on the energy model of IM using the IP controller strategies. The desired d-axis and q-axis stator voltage components are obtained from the designed controller, which decouples torque and flux. The constant switching frequency can be applied using space-vector pulse width modulation, since the desired stator voltage can be known from the decoupling torque and flux controllers. In order to achieve stable operation of the proposed IP controllers, the gains of the controllers are chosen by setting the poles in negative (left) half of s-plane and by choosing the rising time for the response of the step function. The proposed controller was verified in simulations using Matlab/Simulink and results have proven excellent performance. It was found that the proposed IP controllers can provide excellent performance to track the desired torque and speed and to reject the disturbance of load.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.686-689
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• 2005

A numerical simulation method is developed to analyze the dynamic response of a cantilever switch, which is driven by electrostatic force and a basic component of electro-mechanical coupled system. First, point-charges model on conductor is proposed as a lumped parameter of electrical part. Then, this model is easily incorporated into a multi-body dynamics analysis algorithm, the generalized recursive dynamics formula previously developed by our research group. The resulting motion of a coupled overall system is formulated as a differential algebraic equation form including electrical and mechanical variables together. The equation is simultaneously solved in every time step. To implement this approach into the useful dynamics analysis tool, we used multibody dynamics software (RecurDyn) based on the generalized recursive formula using relative coordinate. The developed numerical simulation tool is evaluated by applying to many different driving condition and switch configuration. The final analysis model will be added to RecurDyn as a basic module for dynamics analysis of electro-mechanical coupled system.