• Title, Summary, Keyword: quadratic form

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A study on log-density ratio in logistic regression model for binary data

  • Kahng, Myung-Wook
    • Journal of the Korean Data and Information Science Society
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    • v.22 no.1
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    • pp.107-113
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    • 2011
  • We present methods for studying the log-density ratio, which allow us to select which predictors are needed, and how they should be included in the logistic regression model. Under multivariate normal distributional assumptions, we investigate the form of the log-density ratio as a function of many predictors. The linear, quadratic and crossproduct terms are required in general. If two covariance matrices are equal, then the crossproduct and quadratic terms are not needed. If the variables are uncorrelated, we do not need the crossproduct terms, but we still need the linear and quadratic terms.

Development of an Optimum Hull Form for a Container Ship with Minimum Wave Resistance (최소 조파저항을 가지는 컨테이너선의 선형최적화 기법에 대한 연구)

  • 최희종;서광철;김방은;전호환
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.4
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    • pp.8-15
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    • 2003
  • This paper presents the method for developing an optimum hull form with minimum wave resistance using SQP(sequential quadratic programming) as an optimization technique. The wave resistance is evaluated by a Rankine source panel method with non-linear free surface conditions and the ITTC 1957 friction line is used to predict the frictional resistance coefficient. The geometry of the hull surface is represented and modified using B-spline surface patches. The optimization method is applied to Series 60 hull and KCS(KRISO 3600 TEU Container Ship). The obtained results prove that the method is appropriate for preliminary hull form design.

A Study about the Properties of Quadratic Functions and Classroom Implications from a Polynomial Perspective (다항식 관점에 의한 이차함수의 성질 탐구와 지도방안 탐색)

  • Cho, Cheong-Soo
    • Journal of the Korean School Mathematics Society
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    • v.9 no.2
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    • pp.121-139
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    • 2006
  • This study identified the problems of teaching quadratic functions using a translation and a vertex form by completing squares of which method make teaching contents not to be interconnected and tend to interfere students' conceptual understanding. This seems to generated from which the current mathematics curriculum is not organized to deliver the related contents of quadratic functions from polynomial expressions students have already known. To resolve it this study investigates the properties of quadratic functions from a polynomial perspective and discusses classroom implications with a couple of concrete applications.

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Study for Optimal Hull Form Design of a High Speed Ro-Pax Ship on Wave-making Resistance Performance (고속 Ro-Pax선형의 조파저항성능 향상을 위한 최적 선형설계에 관한 연구)

  • Park, Dong-Woo;Choi, Hee-Jong
    • Journal of Navigation and Port Research
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    • v.36 no.10
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    • pp.787-793
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    • 2012
  • A hull form design technique to enhance the wave-making resistance performance for a medium size high speed Ro-Pax ship was studied introducing an optimization method and an automatic hull form modification method. SQP(sequential quadratic programming) was applied as the optimization algorithm and the geometry of hull surface was represented and modified using the NURBS(Non-Uniform Rational B-Spline). The wave-making resistance performance as an objective function in the optimization procedure was evaluated using the Rankine source panel method in which nonlinearity of the free surface boundary conditions and the trim and sinkage of the ship was fully taken into account. Using the Ro-Pax ship as a base hull, the hull-form optimization method was applied to obtain the hull shape that produced the lower wave-making resistance. To verify the validity of the hull-form optimization method, the numerical results was compared with the model test results.

An Analysis on the Inquiry Activities of Quadratic Surface throughout Mathematically Gifted Students' Analogical Inference (수학영재학생들의 유추를 통한 이차곡면의 탐구활동 분석)

  • Yang, Ki-Yeol;Lee, Ui-Jin
    • Journal of Gifted/Talented Education
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    • v.21 no.2
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    • pp.269-286
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    • 2011
  • The purpose of this thesis is to examine difficulties students face in the inquiry activities of quadratic surface throughout mathematically gifted students' analogical inference and the influence of Cabri 3D in students' inquiry activities. For this examination, students' inquiry activities were observed, data of inferring quadratic surface process was analyzed, and students were interviewed in the middle of and at the end of their activities. The result of this thesis is as following: First, students had difficulties to come up with quadratic surfaced graph in the inquiry activity of quadratic surface and express the standard type equation. Secondly, students had difficulties confirming the process of inferred quadratic surface. Especially, students struggled finding out the difference between the inferred quadratic surface and the existing quadratic surface and the cause of it. Thirdly, applying Cabri 3D helped students to think of quadratic surface graph, however, since it could not express the quadratic surface graph in a perfect form, it is hard to say that Cabri 3D is helpful in the process of confirming students' inferred quadratic surface.

RAY CLASS INVARIANTS IN TERMS OF EXTENDED FORM CLASS GROUPS

  • Yoon, Dong Sung
    • East Asian mathematical journal
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    • v.37 no.1
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    • pp.87-95
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    • 2021
  • Let K be an imaginary quadratic field with ��K its ring of integers. For a positive integer N, let K(N) be the ray class field of K modulo N��K, and let ��N be the field of meromorphic modular functions of level N whose Fourier coefficients lie in the Nth cyclotomic field. For each h ∈ ��N, we construct a ray class invariant as its special value in terms of the extended form class group, and show that the invariant satisfies the natural transformation formula via the Artin map in the sense of Siegel and Stark. Finally, we establish an isomorphism between the extended form class group and Gal(K(N)/K) without any restriction on K.

Quadratic B-spline finite element method for a rotating non-uniform Rayleigh beam

  • Panchore, Vijay;Ganguli, Ranjan
    • Structural Engineering and Mechanics
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    • v.61 no.6
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    • pp.765-773
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    • 2017
  • The quadratic B-spline finite element method yields mass and stiffness matrices which are half the size of matrices obtained by the conventional finite element method. We solve the free vibration problem of a rotating Rayleigh beam using the quadratic B-spline finite element method. Rayleigh beam theory includes the rotary inertia effects in addition to the Euler-Bernoulli theory assumptions and presents a good mathematical model for rotating beams. Galerkin's approach is used to obtain the weak form which yields a system of symmetric matrices. Results obtained for the natural frequencies at different rotating speeds show an accurate match with the published results. A comparison with Euler-Bernoulli beam is done to decipher the variations in higher modes of the Rayleigh beam due to the slenderness ratio. The results are obtained for different values of non-uniform parameter ($\bar{n}$).

ISOGONAL AND ISOTOMIC CONJUGATES OF QUADRATIC RATIONAL Bézier CURVES

  • Yun, Chan Ran;Ahn, Young Joon
    • The Pure and Applied Mathematics
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    • v.22 no.1
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    • pp.25-34
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    • 2015
  • In this paper we characterize the isogonal and isotomic conjugates of conic. Every conic can be expressed by a quadratic rational B$\acute{e}$zier curve having control polygon $b_0b_1b_2$ with weight w > 0. We show that the isotomic conjugate of parabola and hyperbola with respect to ${\Delta}b_0b_1b_2$ is ellipse, and that the isotomic conjugate of ellipse with the weight $w={\frac{1}{2}}$ is identical. We also find all cases of the isogonal conjugate of conic with respect to ${\Delta}b_0b_1b_2$. Our characterizations are derived easily due to the expression of conic by the quadratic rational B$\acute{e}$ezier curve in standard form.