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Analysis and optimal design of fiber-reinforced composite structures: sail against the wind

  • Nascimbene, R.
    • Wind and Structures
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    • v.16 no.6
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    • pp.541-560
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    • 2013
  • The aim of the paper is to use optimization and advanced numerical computation of a sail fiber-reinforced composite model to increase the performance of a yacht under wind action. Designing a composite-shell system against the wind is a very complex problem, which only in the last two decades has been approached by advanced modeling, optimization and computer fluid dynamics (CFDs) based methods. A sail is a tensile structure hoisted on the rig of a yacht, inflated by wind pressure. Our objective is the multiple criteria optimization of a sail, the engine of a yacht, in order to obtain the maximum thrust force for a given load distribution. We will compute the best possible yarn thickness orientation and distribution in order to minimize the total fiber volume with some displacement constraints and in order to leave the most uniform stress distribution over the whole structure. In this paper our attention will be focused on computer simulation, modeling and optimization of a sail-shape mathematical model in different regatta and wind conditions, with the purpose of improving maneuverability and speed made good.

The Analysis study of 'datum' 'in Middle School Geometry on the Basis of 'The Data' of Euclid (유클리드의 자료론(The Data)에 기초한 중학교 기하영역의 '자료(datum)' 분석 연구)

  • Suh, Bo-Euk
    • Communications of Mathematical Education
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    • v.24 no.3
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    • pp.691-708
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    • 2010
  • The purpose of this study is to analyze 'datum' of 'The Data' in the textbooks of middle school on the basis of 'The Data of Euclid' and develop datum. For this, the followings are conducted. First, the distinctive structure of datum of 'The Data' is considered. Second, some learning materials the contents of geometry in the textbooks of middle school are analyzed and the mathematical meanings are explored. Third, the applicable datum to geometry education of middle school are developed and the way of educational use is studied. The hopefully, the result of this study will make school mathematics education more plentiful and give meaningful implications to revision of mathematics education curriculum and the improvement of teaching and learning.

The controllable fluid dash pot damper performance

  • Samali, Bijan;Widjaja, Joko;Reizes, John
    • Smart Structures and Systems
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    • v.2 no.3
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    • pp.209-224
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    • 2006
  • The use of smart dampers to optimally control the response of structures is on the increase. To maximize the potential use of such damper systems, their accurate modeling and assessment of their performance is of vital interest. In this study, the performance of a controllable fluid dashpot damper, in terms of damper forces, damper dynamic range and damping force hysteretic loops, respectively, is studied mathematically. The study employs a damper Bingham-Maxwell (BingMax) model whose mathematical formulation is developed using a Fourier series technique. The technique treats this one-dimensional Navier-Stokes's momentum equation as a linear superposition of initial-boundary value problems (IBVPs): boundary conditions, viscous term, constant Direct Current (DC) induced fluid plug and fluid inertial term. To hold the formulation applicable, the DC current level to the damper is supplied as discrete constants. The formulation and subsequent simulation are validated with experimental results of a commercially available magneto rheological (MR) dashpot damper (Lord model No's RD-1005-3) subjected to a sinusoidal stroke motion using a 'SCHENK' material testing machine in the Materials Laboratory at the University of Technology, Sydney.

A four variable trigonometric integral plate theory for hygro-thermo-mechanical bending analysis of AFG ceramic-metal plates resting on a two-parameter elastic foundation

  • Tounsi, Abdelouahed;Al-Dulaijan, S.U.;Al-Osta, Mohammed A.;Chikh, Abdelbaki;Al-Zahrani, M.M.;Sharif, Alfarabi;Tounsi, Abdeldjebbar
    • Steel and Composite Structures
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    • v.34 no.4
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    • pp.511-524
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    • 2020
  • In this research, a simple four-variable trigonometric integral shear deformation model is proposed for the static behavior of advanced functionally graded (AFG) ceramic-metal plates supported by a two-parameter elastic foundation and subjected to a nonlinear hygro-thermo-mechanical load. The elastic properties, including both the thermal expansion and moisture coefficients of the plate, are also supposed to be varied within thickness direction by following a power law distribution in terms of volume fractions of the components of the material. The interest of the current theory is seen in its kinematics that use only four independent unknowns, while first-order plate theory and other higher-order plate theories require at least five unknowns. The "in-plane displacement field" of the proposed theory utilizes cosine functions in terms of thickness coordinates to calculate out-of-plane shear deformations. The vertical displacement includes flexural and shear components. The elastic foundation is introduced in mathematical modeling as a two-parameter Winkler-Pasternak foundation. The virtual displacement principle is applied to obtain the basic equations and a Navier solution technique is used to determine an analytical solution. The numerical results predicted by the proposed formulation are compared with results already published in the literature to demonstrate the accuracy and efficiency of the proposed theory. The influences of "moisture concentration", temperature, stiffness of foundation, shear deformation, geometric ratios and volume fraction variation on the mechanical behavior of AFG plates are examined and discussed in detail.

Mechanical behaviour analysis of FGM plates on elastic foundation using a new exponential-trigonometric HSDT

  • Fatima Z. Zaoui;Djamel Ouinas;Abdelouahed Tounsi;Belkacem Achour;Jaime A. Vina Olay;Tayyab A. Butt
    • Steel and Composite Structures
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    • v.47 no.5
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    • pp.551-568
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    • 2023
  • In this research, a new two-dimensional (2D) and quasi three-dimensional (quasi-3D) higher order shear deformation theory is devised to address the bending problem of functionally graded plates resting on an elastic foundation. The displacement field of the suggested theories takes into account a parabolic transverse shear deformation shape function and satisfies shear stress free boundary conditions on the plate surfaces. It is expressed as a combination of trigonometric and exponential shear shape functions. The Pasternak mathematical model is considered for the elastic foundation. The material properties vary constantly across the FG plate thickness using different distributions as power-law, exponential and Mori-Tanaka model. By using the virtual works principle and Navier's technique, the governing equations of FG plates exposed to sinusoidal and evenly distributed loads are developed. The effects of material composition, geometrical parameters, stretching effect and foundation parameters on deflection, axial displacements and stresses are discussed in detail in this work. The obtained results are compared with those reported in earlier works to show the precision and simplicity of the current formulations. A very good agreement is found between the predicted results and the available solutions of other higher order theories. Future mechanical analyses of three-dimensionally FG plate structures can use the study's findings as benchmarks.

A Comparative Study between Korea and Japan's First Grade Math Textbooks: centered on Area (우리나라와 일본의 초등학교 1학년 수학 교과서 비교 연구: <수와 연산> 영역을 중심으로)

  • Park, Kyo Sik
    • Journal of the Korean School Mathematics Society
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    • v.17 no.2
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    • pp.235-249
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    • 2014
  • In this paper, teaching contents in area between Korea and Japan's first grade math textbooks are compared. Based on the results of this comparison, implications for improving our grade 1 math textbooks are obtained as follows. Firstly, when describing the configuration of two-digit numbers, it needs to be considered that, after the mathematical description of a concrete material representing two-digit numbers, then it should be processed mathematically. Secondly, with respect to the composition and decomposition of numbers, use of the expression of 'some number and some number' needs to be considered. Thirdly, when reading addition expression and subtraction expression with an equal sign, the way of reading them with terms 'sum' and 'difference' respectively needs to be reconsidered. Fourthly, use of the distinct expression for the supplementing situation and the merging situation respectively and use of the distinct expression for the removing situation and the comparing situation respectively need to be considered. Fifthly, the jump in representing the expression of subtraction of two numbers as the expression of the subtraction or mixed operation of three numbers to explain (some number)-(some number) with borrowing need to be resolved.

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DETERMINATION OF MOISTURE AND NITROGEN ON UNDRIED FORAGES BY NEAR INFRARED REFLECTANCE SPECTROSCOPY(NIRS)

  • Cozzolino, D.;Labandera, M.;Inia La Estanzuela
    • Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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    • 2001.06a
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    • pp.1620-1620
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    • 2001
  • Forages, both grazed and conserved, provide the basis of ruminant production systems throughout the world. More than 90 per cent of the feed energy consumed by herbivorous animals world - wide were provided by forages. With such world - wide dependence on forages, the economic and nutritional necessity of been able to characterize them in a meaningful way is vital. The characterization of forages for productive animals is becoming important for several reasons. Relative to conventional laboratory procedures, Near Infrared Reflectance Spectroscopy (NIRS) offers advantages of simplicity, speed, reduced chemical waste, and more cost-effective prediction of product functionality. NIR spectroscopy represents a radical departure from conventional analytical methods, in that entire sample of forage is characterized in terms of its absorption properties in the near infrared region, rather than separate subsamples being treated with various chemicals to isolate specific components. This forces the analyst to abandon his/her traditional narrow focus on the sample (one analyte at a time) and to take a broader view of the relationship between components within the sample and between the sample and the population from which it comes. forage is usually analysed by NIRS in dry and ground presentation. Initial success of NIRS analysis of coarse forages suggest a need to better understand the potential for analysis of minimally processed samples. Preparation costs and possible compositional alterations could be reduced by samples presented to the instrument in undried and unground conditions. NIRS has gained widespread acceptance for the analysis of forage quality constituents on dry material, however little attention has been given to the use of NIRS for chemical determinations on undried and unground forages. Relatively few works reported the use of NIRS to determine quality parameters on undried materials, most of them on both grass and corn silage. Only two works have been found on the determination of quality parameters on fresh forages. The objectives of this paper were (1) to evaluate the use of NIRS for determination of nitrogen and moisture on undried and unground forage samples and (2) to explore two mathematical treatments and two NIR regions to predict chemical parameters on fresh forage. Four hundred forage samples (n: 400) were analysed in a NIRS 6500 instrument (NIR Systems, PA, USA) in reflectance mode. Two mathematical treatments were applied: 1,4,4,1 and 2,5,5,2. Predictive equations were developed using modified partial least squares (MPLS) with internal cross - validation. Coefficient of determination in calibration (${R^2}_{CAL}$) and standard error in cross-validation (SECV) for moisture were 0.92 (12.4) and 0.92 (12.4) for 1,4,4,1 and 2,5,5,2 respectively, on g $kg^{-1}$ dry weight. For crude protein NIRS calibration statistics yield a (${R^2}_{CAL}$) and (SECV) of 0.85 (19.8) and 0.85 (19.6) for 1,4,4,1 and 2,5,5,2 respectively, on a dry weight. It was concluded that NIRS is a suitable method to predict moisture and nitrogen on fresh forage without samples preparation.

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An analysis of preservice mathematics teachers' reading of curriculum materials: Focused on conditional probability (예비 수학교사들의 교육과정 자료 해석: 조건부확률을 중심으로)

  • Ku, Nayoung;Tak, Byungjoo;Choi, Inyong;Kang, Hyun-Young
    • The Mathematical Education
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    • v.58 no.3
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    • pp.347-365
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    • 2019
  • It is important to pay attention to how teachers recognize and use curriculum materials in order to link written curriculum and enacted curriculum. In this study, 90 preservice mathematics teachers were surveyed to identify their perspective and reading of curriculum materials. Especially, we focused on the curriculum documents, textbooks, and teachers' guidebooks containing the concept of conditional probability which is addressed in highschool mathematics curriculum. The various misconceptions of conditional probability were reported in the many researches, and there are multiple methods to introduce conditional probability in mathematics classes. As a result, curriculum materials have some limits to be used as they are and considered to be reconstructable by participants, but their curriculum reading were mainly classified to be descriptive and evaluative, not to be interpretive. However, unlike curriculum documents, textbooks and teachers' guidebooks were partially interpreted by participants using their knowledge of conditional probability. The purpose of this study is to investigate the profession of mathematics teachers in terms of curriculum implementation. We expect that this study will provide a basic framework for analyzing mathematics teachers' works and suggest some implications for the professional development of mathematics teachers.

Development of the Diagnostic Worksheet for Mathematics Academic Counseling (수학학습 상담을 위한 진단 검사지 개발 연구)

  • Ko, Ho Kyoung;Yang, Kil-seok;Lee, Hwan Chul
    • Communications of Mathematical Education
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    • v.29 no.4
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    • pp.723-743
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    • 2015
  • In this research, The objective of the present study was to develop a preliminary diagnostic worksheet for use in consultations for learning mathematics. In order to achieve this, the worksheet was constructed with questions designed to assess the students. Through standardization, diagnostic worksheets for primary school students in grades 5 and 6 and secondary school students in grades 7 and 8 were produced. The diagnostic worksheet was divided into three sections, consisting of the psychology of learning mathematics in section 1, the methodology in learning mathematics in section 2, and personal preferences in learning mathematics in section 3. The psychology of learning mathematics was composed of questions on factors such as, "confidence in math learning ability," "math anxiety," and "attitude in learning mathematics." Moreover, factors in methodology in learning mathematics were "self-management in learning mathematics" and "math learning strategies." Those for personal preferences in learning mathematics asked about "motivation" and "preferences" with questions about "math learning habits" and "management methods for learning math." This diagnostic worksheet can be used as basic material in consulting students on learning mathematics.

Use of design optimization techniques in solving typical structural engineering related design optimization problems

  • Fedorik, Filip;Kala, Jiri;Haapala, Antti;Malaska, Mikko
    • Structural Engineering and Mechanics
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    • v.55 no.6
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    • pp.1121-1137
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    • 2015
  • High powered computers and engineering computer systems allow designers to routinely simulate complex physical phenomena. The presented work deals with the analysis of two finite element method optimization techniques (First Order Method-FOM and Subproblem Approximation Method-SAM) implemented in the individual Design Optimization module in the Ansys software to analyze the behavior of real problems. A design optimization is a difficult mathematical process, intended to find the minimum or maximum of an objective function, which is mostly based on iterative procedure. Using optimization techniques in engineering designs requires detailed knowledge of the analyzed problem but also an ability to select the appropriate optimization method. The methods embedded in advanced computer software are based on different optimization techniques and their efficiency is significantly influenced by the specific character of a problem. The efficiency, robustness and accuracy of the methods are studied through strictly convex two-dimensional optimization problem, which is represented by volume minimization of two bars' plane frame structure subjected to maximal vertical displacement limit. Advantages and disadvantages of the methods are described and some practical tips provided which could be beneficial in any efficient engineering design by using an optimization method.