共查询到20条相似文献，搜索用时 46 毫秒
1.
CAI Hong-jie WANG Guo-jin 《浙江大学学报(A卷英文版)》2007,8(10):1650-1656
Applying homogeneous coordinates, we extend a newly appeared algorithm of best constrained multi-degree reduction for polynomial Bezier curves to the algorithms of constrained multi-degree reduction for rational Bezier curves. The idea is introducing two criteria, variance criterion and ratio criterion, for reparameterization of rational Bezier curves, which are used to make uniform the weights of the rational Bezier curves as accordant as possible, and then do multi-degree reduction for each component in homogeneous coordinates. Compared with the two traditional algorithms of ＂cancelling the best linear common divisor＂ and ＂shifted Chebyshev polynomial＂, the two new algorithms presented here using reparameterization have advantages of simplicity and fast computing, being able to preserve high degrees continuity at the end points of the curves, do multi-degree reduction at one time, and have good approximating effect. 相似文献
2.
Applying homogeneous coordinates, we extend a newly appeared algorithm of best constrained multi-degree reduc- tion for polynomial Bézier curves to the algorithms of constrained multi-degree reduction for rational Bézier curves. The idea is introducing two criteria, variance criterion and ratio criterion, for reparameterization of rational Bézier curves, which are used to make uniform the weights of the rational Bézier curves as accordant as possible, and then do multi-degree reduction for each component in homogeneous coordinates. Compared with the two traditional algorithms of "cancelling the best linear common divisor" and "shifted Chebyshev polynomial", the two new algorithms presented here using reparameterization have advantages of simplicity and fast computing, being able to preserve high degrees continuity at the end points of the curves, do multi-degree reduction at one time, and have good approximating effect. 相似文献
3.
LU Li-zheng WANG Guo-zhao 《浙江大学学报(A卷英文版)》2007,8(10):1657-1662
This paper presents a quadratic programming method for optimal multi-degree reduction of Bézier curves with G1-continuity. The L2 and l2 measures of distances between the two curves are used as the objective functions. The two additional parameters, available from the coincidence of the oriented tangents, are constrained to be positive so as to satisfy the solvability condition. Finally, degree reduction is changed to solve a quadratic problem of two parameters with linear constraints. Applica 相似文献
4.
This paper presents a quadratic programming method for optimal multi-degree reduction of Bézier curves with G1-continuity. The L2 and l2 measures of distances between the two curves are used as the objective functions. The two additional parameters, available from the coincidence of the oriented tangents, are constrained to be positive so as to satisfy the solvability condition. Finally, degree reduction is changed to solve a quadratic problem of two parameters with linear constraints. Applica- tions of degree reduction of Bézier curves with their parameterizations close to arc-length parameterizations are also discussed. 相似文献
5.
According to the teaching practice, we find that there are many factors, which affect English language learning in China. In order to raise the help of the factors during English study, it is necessary to know it clearly. This paper aims at introducing the factors which are mainly divided into four parts, that is, interest, motivation, determination and personality, and also suggests three key methods to teach students English, including arousing students＇ interest and stimulating the learning motivation; helping students build up self-confidence and enhancing concept of participation; making easy atmosphere and using artistic ways. 相似文献
6.
QIAO Lei 《重庆大学学报(英文版)》2007,6(2):146-150
Based on a unicity theorem for entire funcitions concerning differential polynomials proposed by M. L. Fang and W. Hong, we studied the uniqueness problem of two meromorphic functions whose differential polynomials share the same 1- point by proving two theorems and their related lemmas. The results extend and improve given by Fang and Hong’s theorem. 相似文献
7.
Dennis Ping-Cheng Wang 《美中教育评论》2008,5(9):32-41
Movement activities can be used to integrate with any other curriculum in childhood education. The movements can inspire the sense of rhythmic concepts for children. This study aims at investigating how children can be motivated and inspired rhythmically by body movement through Dalcroze approach. In this research, the author revealed how physical movements can motivate children＇s potential sense of rhythm and inspire children＇s interest of musical rhythmic concepts learning. The study was conducted with 1000 primary school 6th grade students from twenty primary schools in Taipei, Taiwan. These 1000 6th grade students have the same age, same music syllabus and have equally same music training at their schools. The 1000 students were divided into two equal groups, one having different activities of body movements at school, and the other without. The different activities included tapping, swinging, clapping, turning, and stamping simple rhythms. The experiments consisted two parts which were rhythm dictation and improvisational skills. All the participants were equally given the pre-test and post-test as evidences of progress of the experiment, and the researcher then compared with the differences of the two tests of the two groups before and after the experiment to see if there were any progress in their learning of musical rhythms. The study lasted 6 months and consisted of three stages： observation, comparison, and analysis. The author observed and compared the two groups of students, analyzed the results and found out that the two groups demonstrated obvious differences in their degree of progress on learning of musical rhythms. 相似文献
8.
As time goes by,humans are making the earth sick.People cut down too much trees ① and leave more and more rubbish here and there.Factories let out their waste without doing anything to it.All this has caused many serious problems.More and more good farmland has turned into desert,the rivers and lakes have polluted② and the water in them is dirty and poisonous.The air is less clean,even the temperature of the earth is higher than before.The earth is sick now.What should we do to save her? 相似文献
9.
《海外英语》2014,(4):39-39
The Active ＆ Passive Voices
In this month＇ s grammar fun section, we＇ll be looking at the active and passive voices with past tense verbs. Just to remind you from last month, we use the active voice when the subject of the verb is the thing or person doing the action. For example： 相似文献
In this month＇ s grammar fun section, we＇ll be looking at the active and passive voices with past tense verbs. Just to remind you from last month, we use the active voice when the subject of the verb is the thing or person doing the action. For example： 相似文献
10.
Zou LK Wang HN Pan X Tian GB Xie ZW Wu Q Chen H Xie T Yang ZR 《Journal of Zhejiang University. Science. B》2008,9(7):536-545
The phyAm gene encoding acid phytase and optimized neutral phytase phyCs gene were inserted into expression vector pPIC9K in correct orientation and transformed into Pichiapastoris in order to expand the pH profile of phytase and decrease the cost of production. The fusion phytase phyAm-phyCs gene was successfully overexpressed in P. pastoris as an active and ex-tracellular phytase. The yield of total extracellular fusion phytase activity is (25.4±0.53) U/ml at the flask scale and (159.1±2.92) U/ml for high cell-density fermentation, respectively. Purified fusion phytase exhibits an optimal temperature at 55 ℃ and an optimal pH at 5.5～6.0 and its relative activity remains at a relatively high level of above 70% in the range of pH 2.0 to 7.0. About 51% to 63% of its original activity remains after incubation at 75 ℃ to 95 ℃ for 10 min. Due to heavy glycosylation, the expressed fusion phytase shows a broad and diffuse band in SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). After deglycosylation by endoglycosidase H (EndoHf), the enzyme has an apparent molecular size of 95 kDa. The characterization of the fusion phytase was compared with those of phyCs and phyAm. 相似文献
11.
This paper focuses on obtaining an asymptotic solution for coupled heat and mass transfer problem during the solidification of high water content materials. It is found that a complicated function involved in governing equations can be approached by Taylor polynomials unlimitedly, which leads to the simplification of governing equations. The unknown functions involved in governing equations can then be approximated by Chebyshev polynomials. The coefficients of Chebyshev polynomials are determined and an asymptotic solution is obtained. With the asymptotic solution, the dehydration and freezing fronts of materials are evaluated easily, and are consistent with numerical results obtained by using an explicit finite difference method. 相似文献
12.
We present a novel approach for dealing with optimal approximate merging of two adjacent Bezier eurves with G^2-continuity. Instead of moving the control points, we minimize the distance between the original curves and the merged curve by taking advantage of matrix representation of Bezier curve＇s discrete structure, where the approximation error is measured by L2-norm. We use geometric information about the curves to generate the merged curve, and the approximation error is smaller. We can obtain control points of the merged curve regardless of the degrees of the two original curves. We also discuss the merged curve with point constraints. Numerical examples are provided to demonstrate the effectiveness of our algorithms. 相似文献
13.
丁广义割圆序列的线性复杂度 总被引：1，自引：0，他引：1
Minimal polynomials and linear complexity of binary Ding generalized cyclotomic sequences of order 2 with the two-prime residue ring Zpq are obtained by Bai in 2005. In this paper, we obtain linear complexity and minimal polynomials of all Ding generalized cyclotomic sequences. Our result shows that linear complexity of these sequences takes on the values pq and pq-1 on our necessary and sufficient condition with probability 1/4 and the lower bound （pq - 1）/2 with probability 1/8. This shows that most of these sequences are good. We also obtained that linear complexity and minimal polynomials of these sequences are independent of their orders. This makes it no more difficult in choosing proper p and q. 相似文献
14.
表面磁钢永磁无刷电机电磁转矩的解析法分析 总被引：1，自引：0，他引：1
With the air gap magnetic field distribution of surface mounted permanent magnet （PM） motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis （FEA）. In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy. 相似文献
15.
With the air gap magnetic field distribution of surface mounted permanent magnet (PM) motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis (FEA). In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy. 相似文献
16.
4 总被引：5，自引：0，他引：5
LI Zhong-guo SONG Min-yan 《美中教育评论》2007,4(1):62-65
This paper reconsiders the functions of the traditional English grammar teaching and the communicative language teaching. Through analysis and practice, we think that they are not opposed to each other. In order to improve the students＇ ability and gain better teaching results, the two kinds of teaching approaches should not be used respectively. On the contrary, we＇d better combine them together and use them flexibly in our teaching work. 相似文献
17.
As time goes by,humans are making the Earth sick.People cut down too many trees and leave more and more rubbish here and there.Factories let out their waste without doing anything to it.All of these have caused many serious problems.More and more good land has turned into deserts.Rivers and lakes have been polluted and the water in them becomes dirty and poisonous. 相似文献
18.
A spectral method based on the Legendre polynomials for solving Helmholz equations was proposed. With an explicit formula for the Legendre polynomials in terms of arbitrary order of their derivatives, the successive integration of the Legendre polynomials was represented by the Legendre polynomials. Then the method was formulized for secondorder differential equations in one dimension and two dimensions. Numerical results indicate that the suggested method is significantly accurate and in satisfactory agreement with the exact solution. 相似文献
19.
ZHAO Li-li 《浙江大学学报(A卷英文版)》2007,8(6):957-962
In this paper, we consider some polynomial (α,β)-metrics, and discuss the sufficient and necessary conditions for a Finsler metric in the form F=α a1β a2β2/α a4β4/α3 to be projectively flat, where ai (i=1,2,4) are constants with a1≠0, α is a Riemannian metric and β is a 1-form. By analyzing the geodesic coefficients and the divisibility of certain polynomials, we obtain that there are only five projectively flat cases for metrics of this type. This gives a classification for such kind of Finsler metrics. 相似文献
20.
Anna Quindlen 《海外英语》2004,(1):33
I’m a novelist.My work is humannature.Real life is all I know.Don't everconfuse the two, your life and yourwork.You will walk out of here this af-ternoon with only one thing that no oneelse has.There will be hundreds of peopleout there with your same degree;therewill be thousands of people doing whatyou want to do for a living.But you willbe the only person alive who has sole 相似文献