• Coupled systems mechanics
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• v.7 no.5
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• pp.509-524
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• 2018

A hierarchical multi-scale modeling strategy devoted to the study of a Bitumen-Bound Gravel (BBG) is presented in this paper. More precisely, the paper investigates the temperature-dependent linear viscoelastic of the material when submitted to low deformations levels and moderate number of cycles. In such a hierarchical approach, 3D digital Representative Elementary Volumes are built and the outcomes at a scale (here, the sub-mesoscale) are used as input data at the next higher scale (here, the mesoscale). The viscoelastic behavior of the bituminous phases at each scale is taken into account by means of a generalized Maxwell model: the bulk part of the behavior is separated from the deviatoric one and bulk and shear moduli are expanded into Prony series. Furthermore, the viscoelastic phases are considered to be thermorheologically simple: time and temperature are not independent. This behavior is reproduced by the Williams-Landel-Ferry law. By means of the FE simulations of stress relaxation tests, the parameters of the various features of this temperature-dependent viscoelastic behavior are identified.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.1
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• pp.29-36
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• 2016

Tensairity girder is a light weight inflatable fabric structural concept which can be used in road emergency transportation. It uses low pressure air to stabilize compression elements against buckling. With the purpose of obtaining the comprehensive target of minimum deflection and weight under ultimate load, the cross-section and the inner pressure of tensairity girder was optimized in this paper. The Variable Complexity Modeling (VCM) method was used in this paper combining the Kriging approximate method with the Finite Element Analysis (FEA) method, which was implemented by ABAQUS. In the Kriging method, the sample points of the surrogate model were outlined by Design of Experiment (DOE) technique based on Optimal Latin Hypercube. The optimization framework was constructed in iSIGHT with a global optimization method, Multi-Island Genetic Algorithm (MIGA), followed by a local optimization method, Sequential Quadratic Program (SQP). The result of the optimization gives a prominent conceptual design of the tensairity girder, which approves the solution architecture of VCM is feasible and efficient. Furthermore, a useful trend of sensitivity between optimization variables and responses was performed to guide future design. It was proved that the inner pressure is the key parameter to balance the maximum Von Mises stress and deflection on tensairity girder, and the parameters of cross section impact the mass of tensairity girder obviously.

• Journal of Korean Society of Transportation
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• v.7 no.1
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• pp.35-42
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• 1989

The multinomial logit model has been applied for various choice problems. Among others, the joint destination mode choice, the mode choice and the route choice are the three major modeling topics for korean transportation planners. This paper examines with real world data (the Olympic road and its competing two major arterials) the usefulness of a Logit route choice model. Quites surpisingly, it is found that the multinomial route choice behavioral model calibrated for this study based on (0,1) individula data base can not provide a good estimate for O-D trips less than 6㎞. 400data points and 3case studies might not be sufficient for a sound conclusion. It is, however, believed from a series of similar studies conducted by the authors that the route choice behavior is more sensitive (more demand elastic with respect to travel time changes) than the mode choice and the shorter trip, the more sensitive. The travel time parameters for destination choice models are usually smalle than the travel time parameters for mode choice models and these parameters (for mode choice models) turn our smaller than the travel time parameters for route choice models from this study. Table 2 in this paper shows parameter changes for three different markets and Table 3 shows the modeling errors when the estimated individual probabilities are aggregated into a route level.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.432-439
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• 2003

In this research, we are trying to develop the new hydraulic driven tire roller which is conventionally operated by mechanical transmission system. The reason why we would like to develop it is that tire roller is one of the most useful machine for the road construction site and also imported totally from overseas. In this paper, we conceptualize the new hydraulic system and derive the equations of motion for dynamic analysis. And we investigate system modeling by using DAQ system. Finally, we will design the controller, which can manage the hydraulic circuit of steering and traction mechanism system. The advent of modern high-speed computers coupled with the application of high-fidelity simulation technology can be used to create “virtual prototypes of construction equipment. Tests conducted on these virtual prototypes may be used to augment actual machine testing, thereby lowering costs and shortening time to production. So, we studied tire roller to integrate development technology. In System Analysis, We formulate hydraulic driving system model and hydraulic steering system model. Also, We integrate DAQ system to acquire experimental result in real tire roller equipment.

• International Journal of Highway Engineering
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• v.14 no.6
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• pp.93-101
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• 2012

PURPOSES : This study is to develop ISM for potential risk factor in School Zone. METHODS : Based on the literature review, the Analytic Hierarchy Process (AHP) has been used most widely. However, it is difficult to apply in practice because the AHP results have the characteristics of the independence between each element and the interlayer can not explain the interrelationship. The Network Analysis Process (ANP) is possible to analyze the relationship between the elements and the network through the feedback. But, the reliability of the analysis fall because of complicated pair of comparison, also it is difficult to solve the super matrix. In this study, the complicated relationship between each element is inquired through the Interpretive Structural Modeling (ISM). RESULTS : The methodology of ISM is developed to remove the children's potential risk factors in school zone. CONCLUSIONS : It is possible to remove the children's potential risk factors from low level to high level step by step and improve safety. Through this, risk factors can be removed from the low-level, and upper-level will automatically improve.

• Korean Journal of Computational Design and Engineering
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• v.19 no.4
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• pp.316-323
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• 2014

This paper proposes the 3D modeling and simulation technique for predicting the integrated performance of combat vehicle. To consider the practical driving and firing condition of a combat vehicle, the full vehicle model, which can define the six degrees-of-freedom of vehicle motion and various firing angles, is developed. The critical design parameters such as the stiffness and damping coefficient of suspension system are applied to construct the analysis model of vehicle. A simple ballistic model, which incorporates the empirical interior ballistic model and the point mass trajectory model, is built to estimate the firing range and the firing recoil force. To predict the integrated performance and analyze the effect of system parameters, MATLAB/SIM-ULINK model of a combat vehicle for performing the real time simulation is also developed. Several simulation tests incorporating the road bump and the firing recoil force are presented to confirm the effectiveness of the proposed vehicle model.

• Korean Journal of Remote Sensing
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• v.22 no.3
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• pp.221-228
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• 2006

In this study, an integrated 3D modeling and rendering system dealing with 3D urban landscape features such as terrain, building, road and user-defined geometric ones was designed and implemented using $OPENGL\;{|}\;ES$ (Embedded System) API for mobile devices of PDA. In this system, the authoring functions are composed of several parts handling urban landscape features: vertex-based geometry modeling, editing and manipulating 3D landscape objects, generating geometrically complex type features with attributes for 3D objects, and texture mapping of complex types using image library. It is a kind of feature-based system, linked with 3D geo-based spatial feature attributes. As for the rendering process, some functions are provided: optimizing of integrated multiple 3D landscape objects, and rendering of texture-mapped 3D landscape objects. By the active-synchronized process among desktop system, OPENGL-based 3D visualization system, and mobile system, it is possible to transfer and disseminate 3D feature models through both systems. In this mobile 3D urban processing system, the main graphical user interface and core components is implemented under EVC 4.0 MFC and tested at PDA running on windows mobile and Pocket Pc. It is expected that the mobile 3D geo-spatial information systems supporting registration, modeling, and rendering functions can be effectively utilized for real time 3D urban planning and 3D mobile mapping on the site.

• Journal of the Korean Society of Safety
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• v.28 no.2
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• pp.78-83
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• 2013

The traffic culture index is used as a major index in evaluating the traffic safety services of local governments and also serve as important data for the planning and implementation of traffic safety services. However, as the traffic culture index gradually became a standard for comparison among local governments, in part, certain cases arose which questioned the grounds for selecting variables for the index and the validity of the index in terms of its influential relationship between evaluation items. This study analyzed the index's influential relationship by utilizing a PLS structural equation model based on the evaluation results of the 2011 traffic culture index. A variable-linking model was created which recognized the relativity taking into account of the indirect effects between latent variables and this model was proven to be a model suitable in explaining the traffic culture index with a 97.8% explanation power. It was found that traffic safety(0.530), driving behavior(0.527), pedestrian behavior(0.187) and vulnerable road users(0.147), in such order, had an effect on the traffic culture index. It was also found that human casualties due to traffic accidents under "traffic safety" and traffic light compliance rate under "driving behavior" had an important effect. The study showed that motor vehicle share in illegal parking in school zones did not have a valid explanation power regarding "vulnerable road users".

• Journal of Preventive Medicine and Public Health
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• v.50 no.2
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• pp.83-90
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• 2017

Objectives: The aim of this study was to model the avoidable burden of the risk factors of road traffic crashes in Iran and to prioritize interventions to reduce that burden. Methods: The prevalence and the effect size of the risk factors were obtained from data documented by the traffic police of Iran in 2013. The effect size was estimated using an ordinal regression model. The potential impact fraction index was applied to calculate the avoidable burden in order to prioritize interventions. This index was calculated for theoretical, plausible, and feasible minimum risk level scenarios. The joint effects of the risk factors were then estimated for all the scenarios. Results: The highest avoidable burdens in the theoretical, plausible, and feasible minimum risk level scenarios for the non-use of child restraints on urban roads were 52.25, 28.63, and 46.67, respectively. In contrast, the value of this index for speeding was 76.24, 37.00, and 62.23, respectively, for rural roads. Conclusions: On the basis of the different scenarios considered in this research, we suggest focusing on future interventions to decrease the prevalence of speeding, the non-use of child restraints, the use of cell phones while driving, and helmet disuse, and the laws related to these items should be considered seriously.

• The Journal of Engineering Geology
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• v.14 no.2
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• pp.223-233
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• 2004

When the groundwater outflow occurs due to tunnel excavation during the road and railroad construction, depletion of groundwater resources, deficiency in the living and agricultural waters, and changes in the surface water flux are expected. The MODFLOW is a most commonly used and three dimensional finite difference model to predict changes in the groundwater system due to the tunnel construction. A conceptual model is one of the most important elements for the proper modeling results. Essential information will not be extracted from an oversimplified conceptual model while excess time and resources with much field data are required for the very complicated one. This study presented a comparison of the modeling results depending on some conceptual models and discussed construction of the efficient conceptual model for reasonable and realistic results in the tunnel modeling.