• Smart Structures and Systems
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• v.33 no.2
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• pp.133-143
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• 2024

Piezoelectric (PZT) actuators have been widely used in precision positioning fields for their excellent displacement resolution. However, due to the inherent characteristics of piezoelectric actuators, hysteresis has been proven to greatly reduce positioning performance. In this paper, five mathematical hysteretic models based on activation function are proposed to characterize the nonlinear hysteresis characteristics of piezoelectric actuators. Then the performance of the proposed models is verified by particle swarm optimization (PSO) algorithm and the experiment data. Thirdly, the fitting performance of the proposed models is compared with the classical Bouc-Wen model. Finally, the performance of the five proposed models in modelling hysteresis nonlinearity of piezoelectric drivers is compared, in terms of RMSE, MAPE, SAPE and operation efficiency, and relevant suggestions are given.

• Journal of the Korean School Mathematics Society
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• v.19 no.4
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• pp.357-371
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• 2016

The purpose of this study was to decide the task space and Rating Scheme of task difficulty in complicated mathematical modelling situations. One of main objective was also to conform the validation of Rating Scheme to determine the degree of difficulty by comparing the student performance with the statement of the theoretical model. In spring 2014, the experimental setting was in Modelling Course for 38 in-service teachers in mathematics education. In conclusions, we developed the Model of Task Space based on their solution paths in mathematical modelling tasks and Rating Scheme for task difficulty. The Validity of Rating Scheme to determine the degree of task difficulty based on comparing the student performance gave us the meaningful results. Within a modelling task the student performance verifies the degree of difficulty in terms of scoring higher using solution approaches determined as easier and vice versa. Another finding was some relations among three research topics, that is, degree of task difficulty on rating scheme, levels of students performance and numbers of specific heuristic. Those three topics showed the impressive consistence pattern.

• Journal of the Korea Furniture Society
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• v.22 no.4
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• pp.323-329
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• 2011

In our country, domestic species can not be used as a structural member because we have not yet grading system. So, to utilize as a basic data of grading system, bending test and numerical modelling on structural member were conducted in this study. 35 of Douglas-fir, 2" ${\times}$ 6", span 2.4 m were tested for the bending properties, and Ansys software was used to analyze the numerical modelling on the structural members. The data of knots were inspected and applied in numerical modelling. To obtain the accuracy of analysis, nonlinear numerical analysis was carried out instead of linear numerical analysis. Ultimate load had a wide range from 4883N to 11,738 N, and maximum deformation also had a range from 26 mm to 68 mm. Average of ultimate load was 8,616 N, and that of maximum deformation was 48 mm. The distinctive features of failure types were simple tension type and cross-grain tension type. Ulitmate load and maximum deformation from numerical modelling were 7,504 N and 37 mm. The numerical modelling drawn by this study is available to all species, and reasonable prediction on the bending performance is possible with only some material properties.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.4
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• pp.220-228
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• 2002

The cool-down performance after soaking is very important in an automotive air-conditioning system and is considered as a key design variable. Therefore, transient characteristics of each system component are essential to the preliminary design as well as steady-state performance. The objective of this study is to develop a computer simulation model and ostinato theoretically the transient performance of an automotive air-conditioning system. To do that, the mathematical modelling of each component, such as compressor, condenser, receiver/drier, expansion valve, and evaporator, is presented first of all. The basic balance equations about mass and energy are used in modelling. For detailed calculation, condenser and evaporator are divided into many sub-sections. Each sub-section is an elemental volume for modelling. In models of expansion valve and compressor, dynamic behaviors are not considered in this analysis, but the quasisteady state ones are just considered, such as the relation between mass flow rate and pressure drop in expansion device, polytropic process in compressor, etc. Also it is assumed that there are no heat loss and no pressure drop in discharge, liquid, and suction lines. The developed simulation model is validated by comparing with the laboratory test data of an automotive air-conditioning system. The overall time-tracing properties of each component agreed well with those of test data in this case.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.6
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• pp.556-565
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• 2004

We have experimented an actual solar water heating system acquiring real data for one year period. On the basis of the operation data, it is necessary to predict the system performance such as collector efficiency and solar fraction, and to analyze the economical efficiency for system optimal design. To estimate the performance of actual systems through simulation, valid modelling for components consisting of the system should be accompanied. The present study is focused on the modelling for load patterns and operating control conditions. We proposed two load models: concentration model which gathers real loads as a meaningful group and distribution model which disperses real loads with time. If grouping of the load distribution is suitable, the predicted values by the concentration model approaches to those by the distribution model close to actual load pattern apparently. As a result, both of them are in good agreement with those by experiment.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.774-780
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• 2009

Simulation is becoming increasingly popular in construction for training, planning and for assessment of projects. There are, however, significant problems inherent in simulating construction which are not common to other simulations. This paper describes the development and use of computer-based game for teaching and learning of some aspects of construction project management. It is concerned with the development of a model used to simulate the construction of a rock- and clay-fill dam. It includes detailed physical modelling of the performance of individual pieces of equipment and their interaction with the ground, the geography of the project and the weather in which the equipment operates. The behaviour of all of the individual pieces of equipment when acting as fleets is also discussed. The paper also describes the modelling issues of non-technical aspects of earthmoving operations. These include environmental impact, safety, quality and risks. The problems of integrating these with the physics-based models of the equipment performance are discussed. The paper also draws on real experience of using the game in classes in three universities in different countries.

• Korea-Australia Rheology Journal
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• v.21 no.2
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• pp.91-102
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• 2009

This paper describes an extension of viscoelastic Group Interaction Modelling (GIM) to predict the relaxation response of linear, branched and cross-linked structures. This model is incorporated into a Monte Carlo percolation grid simulation used to generate the topological structure during the isothermal cure of a gel, so enabling the chemorheological response to be predicted at any point during the cure. The model results are compared to experimental data for an epoxy-amine systems and good agreement is observed. The viscoelastic model predicts the same exponent power-law behaviour of the loss and storage moduli as a function of frequency and predicts the cross-over in the loss tangent at the percolation condition for gelation. The model also predicts the peak in the loss tangent which occurs when the glass transition temperature surpasses the isothermal cure temperature and the system vitrifies.

• Geomechanics and Engineering
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• v.3 no.1
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• pp.45-59
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• 2011

Scaled centrifuge modelling techniques were used to study the soil-structure interactions and performance of a jointed rollable aluminium roadway (or trackway) system on soft clay under light truck tyre loads. The measured performance and subsequent analyses highlighted that the articulated connections significantly reduced the overall longitudinal flexural stiffness of the roadway leading to stress concentrations in the soil below the joints under tyred vehicle loadings. This resulted in rapid localised failure of the supporting soil that in turn led to excessive transverse flexure of the roadway and ultimately plastic deformations. It is shown that the performance of rollable roadway systems under tyred vehicle trafficking will be improved by eliminating joint rotation to increase longitudinal stiffness.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.328-339
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• 2023

Methanol steam reforming (MSR) is a promising method for hydrogen supplying as a critical step in hydrogen fuel cell commercialization in mobile applications. Modelling and understanding of the reactor behavior is an attractive research field to develop an efficient reformer. Three-layer feed-forward artificial neural network (ANN) and Box-Behnken design (BBD) were used to modelling of MSR process using the Cu-SiO₂ aerogel catalyst. Furthermore, impacts of the basic operational variables and their mutual interactions were studied. The results showed that the most affecting parameters were the reaction temperature (56%) and its quadratic term (20.5%). In addition, it was also found that the interaction between temperature and Steam/Methanol ratio is important on the MSR performance. These models precisely predict MSR performance and have great agreement with experimental results. However, on the basis of statistical criteria the ANN technique showed the greater modelling ability as compared with statistical BBD approach.

• Journal of Information Science Theory and Practice
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• v.11 no.1
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• pp.61-78
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• 2023

Ontological knowledge modelling of epic texts, though being an established research arena backed by concrete multilingual and multicultural works, still suffers from two key shortcomings. Firstly, all epic ontological models developed till date have been designed following ad-hoc methodologies, most often combining existing general purpose ontology development methodologies. Secondly, none of the ad-hoc methodologies consider the potential reuse of existing epic ontological models for enrichment, if available. This paper presents, as a unified solution to the above shortcomings, the design and development of GOMME - the first dedicated methodology for iterative ontological modelling of epics, potentially extensible to works in different research arenas of digital humanities in general. GOMME is grounded in transdisciplinary foundations of canonical norms for epics, knowledge modelling best practices, application satisfiability norms, and cognitive generative questions. It is also the first methodology (in epic modelling but also in general) to be flexible enough to integrate, in practice, the options of knowledge modelling via reuse or from scratch. The feasibility of GOMME is validated via a first brief implementation of ontological modelling of the Indian epic Mahabharata by reusing an existing ontology. The preliminary results are promising, with the GOMME-produced model being both ontologically thorough and competent performance-wise.