共查询到20条相似文献，搜索用时 250 毫秒
1.
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
2.
The energy of interaction between complementary nucleotides in promoter sequences of E. coli was calculated and visualized. The graphic method for presentation of energy properties of promoter sequences was elaborated on. Data obtained indicated that energy distribution through the length of promoter sequence results in picture with minima at -35, -8 and ＋7 regions corresponding to areas with elevated AT （adenine-thymine） content. The most important difference from the random sequences area is related to -8. Four promoter groups and their energy properties were revealed. The promoters with minimal and maximal energy of interaction between complementary nucleotides have low strengths, the strongest promoters correspond to promoter clusters characterized by intermediate energy values. 相似文献
3.
A novel frequency hopping(FH) sequences generator based on advanced encryption standard(AES) iterated block cipher is proposed for FH communication systems.The analysis shows that the FH sequences based on AES algorithm have good performance in uniformity, correlation, complexity and security.A high-speed, low-power and low-cost ASIC of FH sequences generator is implemented by optimizing the structure of S-Box and MixColumns of AES algorithm, proposing a hierarchical power management strategy, and applying the dynamic clock gating technology based on finite state machine and clock gating.SMIC 0.18 μm standard CMOS technology shows that the scale of ASIC is only about 10.68 kgate, power consumption is 33.8 μW/MHz, and the maximum hop-rate is 1 098 901 hop/s.This design is suitable for portable FH communication system for its advantages in high-security and hop-rate, low-power and low-cost.The proposed FH sequences generator has been employed in Bluetooth SoC design. 相似文献
4.
This paper proposes a hybrid optimization to solve the scheduling of household power consumption for Step and Time-of-Use (TOU) tariff system. The target function is the cost of electricity, and the optimization object is total instantaneous power within a billing period. The control variables are starting moments of each household appliance. The optimization procedure is divided into two stages. Firstly, the prerequisite for minimal cost is calculated through mathematical analysis and generalized function theory. Secondly, the solution is obtained by using a heuristic algorithm in which the result of the first stage is considered to reduce the searching space. And an evaluation methodology is deduced to evaluate the optimization. The computer simulation demonstrates that the proposed approach can reduce the cost of electricity evidently in the sense of probability. The approach shows great value for embedded applications. 相似文献
5.
Shengli Zhan 《Frontiers of Education in China》2013,8(2):323-326
This is a book on policy study in the Chinese mainland by an insider with an outsider perspective.With contemporary policies on minban schooling in Shanghai as a case study,Ding illustrates and analyzes a case of policy metamorphosis in the contemporary Chinese mainland.
The book is based on a well-designed qualitative study with 65 in-depth interviews in 2001 and 2004.Ding tries to figure out the logic of policy implementation in Shanghai as an "insider" while having a clear awareness of the dilemma of studying a policy issue in her own culture.She makes the best use of her identity as an insider,not only as a Chinese but as someone who knows some "inside" stories concerning the issue interviewed.As Ding pointed out,"I had obtained some firsthand information about minban education in Shanghai,so that when I sensed that the informants were talking superficially,I let them know that I had heard some inside stories (which usually had very different versions).In this way,sensitive data emerged." (Ding,2011,p.145).This is true,since the views expressed in most interview data Ding collected cannot be found in public or official documents,and are also rarely found in the academic literature. 相似文献
6.
In this paper, we discuss a class of piecewise linear hyperbolic maps on the 2-torus. These maps arise in the second-order digital fdter with two＇ s complement arithmetic. By introducing codings underlying the map operations, we give some admissibility conditions for symbolic sequences and find some periodic properties of these symbolic sequences. Then we use these conditions to check the admissibility of periodic symbol sequences. 相似文献
7.
Anti-ram bollards used in perimeter protection are tested to meet performance requirements of established standards such as the US Department of State Specification SD-STD-02.01. Under these standards, tests are conducted in prescribed conditions that should be representative of the service installation. In actual project, conditions encountered on site may vary from the test environment and it would be expensive and time consuming to validate each deviation with a physical test. High-fidelity physics-based (HFPB) finite element modeling can provide precise simulations of the behavior of anti-ram bollards. This paper presents the use of HFPB finite element modeling, using LS-DYNA, in an actual project to evaluate the performance of an anti-ram bollard design subjected to various boundary conditions representing the physical conditions encountered on site. The study shows that boundary conditions can have a significant influence on the performance of the anti-ram bollards. This suggests that anti-ram bollards must be designed and engineered according to actual conditions that are found on site. It also shows that HFPB modeling can be an effective tool that supplements physical testing of anti-ram bollards. 相似文献
8.
This paper describes a Least Squares （LS） channel estimation scheme for MIMO OFDM systems based on time-domain training sequence. We first compute the minimum mean square error （MSE） of the LS channel estimation, and then derive the optimal criteria of the training sequence with respect to the minimum MSE. It is shown that optimal time-domain training sequence should satisfy two criteria. First, the autocorrelation of the sequence transmitted from the same antenna is an impulse function in a region longer than the channel maximum delay. Second, the cross-correlation between sequences transmitted from different antennas is zero in this region. Simulation results show that the estimator using optimal time-domain training sequences has better performance than that using optimal frequency training sequence at low signal-to-noise ratio （SNR）. To reduce the training overhead, a suboptimal training sequence is also proposed. Comparing with optimal training sequence, it has low computation complexity and high transmission efficiency at the expense of little performance degradation. 相似文献
9.
Mohd. Sahandri Gani Hamzah Vijayaletchumy a/p Subramamam Saifuddin Kumar Abdullah 《美中教育评论》2009,6(9):67-84
In national perception, education is essentially for all. This is fundamental to all-round development, material and spiritual. It refines sensitivities and perceptions that contribute to national cohesion, a scientific temper and independence of mind and spirit--thus furthering the goals of socialism secularism and democracy enshrined in our constitution. The objective of the study focuses on achievement of children with learning disability in science. There are 5 null hypothesis tested in this research. The sample used in this study includes 35 children with learning disabilities in experimental group and 42 children with learning disabilities in control group. The different views taken on special education have ignited spark of controversies over segregating some children from the mainstream and providing them with extra opportunities. There are arguments for and against both special education and integrated education. Special education means the specifically designed instruction that meets the unusual needs of special children. It requires special materials, teaching, techniques, equipment and facilities. The design was an experimental research pre and post-test equivalent group. The research shows that there is no significant difference in all learning objective such as knowledge, comprehension and skill between control group and experimental group in the pre-test. This two sample groups also did not show any significant difference in the pre-test irrespective of gender, educational qualification of the teacher, years of experience of the teacher, parents＇ education, parents＇ profession, parents＇ income, type of management and type of school. On the other hand, for the post-test all the characteristics show that there are significant differences. This shows that there are effects on the treatment group in learning objective. Furthermore the experimental group showed significantly higher gain score than the control group with regard to the learning objective which comprises of knowledge, comprehension, application and skill. 相似文献
10.
This paper reviews recent developments in nonlinear control technologies for shape memory alloy (SMA) actuators in robotics and their related applications. SMA possesses large hysteresis, low bandwidth, slow response, and non-linear behavior, which make them difficult to control. The fast response of the SMA actuator mostly depends upon, (1) type of controller, (2) rate of addition and removal of heat, and (3) shape or form of the actuator. Though linear controllers are more desirable than nonlinear ones, the review of literature shows that the results obtained using nonlinear controllers were far better than the former one. Therefore, more emphasis is made on the nonlinear control technologies taking into account the intelligent controllers. Various forms of SMA actuator along with different heating and cooling methods are presented in this review, followed by the nonlinear control methods and the control problems encountered by the researchers. 相似文献
11.
应用特征和的性质,改进了丁存生提出的关于周期为pq(p和q皆为素数)的广义割圆序列(并研究了其阶数为d≥2时的线性复杂度),以及陈智雄等人对上述序列的一致分布测度和相关测度所做的相应估计,从而达到了更精确的估计值。 相似文献
12.
给出了利用特征为p的扩张域Fq的割圆类构造的几类q-周期伪随机序列的线性复杂度和k-错线性复杂度的下界。该结果将补充Meidl和Winterhof提出的关于割圆生成器的线性复杂度的相关结果,同时推广了Aly、Meidl和Winterhof关于Fp上的p-周期割圆序列的线性复杂度及k-错线性复杂度等相关结论。 相似文献
13.
给出了一个快速算法决定有限域Fq上周期为upn序列的极小多项式.设p,q,u为不同素数,q为模p2的本原根,m为最小正整数使得qm≡1modu和gcd(m,p(p-1))=1.利用一个算法把有限域Fq上周期为upn序列化为几个有限域Fq(ζ)上周期为pn序列,其中ζ为一个u次本原单位根,从而利用肖国正等的算法得到每个周期为pn序列的极小多项式. 相似文献
14.
李金寨 《宁德师专学报(自然科学版)》2012,24(3):246-249,253
对F4上一类具有高非线性度的4元分圆序列的稳定性进行了深入研究.给出了该序列的1-错线性复杂度的一个上界,研究结果表明该序列不具有稳定的线性复杂度性质. 相似文献
15.
设p为奇素数,整数u与p互素,定义广义费马商为:Hp(u)≡uλ-1/(modp),其中λu为u(modp)的乘法阶。讨论了广义费马商的若干算术性质,并利用广义费马商构造两类伪随机二元序列,通过线性递归关系确定了序列的线性复杂度。结论表明,这两类序列具有高的线性复杂度,在序列密码中具有潜在的应用。 相似文献
16.
在有理整值多项式上建立了等价关系，从而将深度有限的无限长序列与有理整值多项式的等价类建立了一一对应，通过分析等价类计算序列的深度分布，构造了一个码C到C的映射D，利用D的性质和线性空间的基础知识给出了线性循环码的深度分布的计算方法. 相似文献
17.
有限域上的多项式有分圆多项式和不可约多项式,其中各由数条原理构成。文中对其性质和构造方法进行了具体研究与论述。 相似文献
18.
解廷月 《雁北师范学院学报》2006,22(5):46-50
由于真核生物基因组染色体上各种序列的组织和安排复杂,所以我们把果蝇染色体上顺次排列的DNA序列分成内含子和编码序列两类.分别用描述序列构成的四个信息参数,分析各类序列沿着染色体分布特征,并着重讨论染色体着丝粒及其周围区域的分布规律,并解释引起这些特征的原因.用线性拟合和多项式拟合分析染色体各类序列沿染色体的统计分布特征(学生t检验),分析各个参数的平均值在染色体不同区域的差别.果蝇染色体参数X值是由D1(碱基偏置)和D2(碱基关联)值共同决定的,但果蝇染色体的编码序列参数X分内含子序列相比,分布没有趋同性.显示出编码序列跟内含子序列染色体的分布不同. 相似文献
19.
讨论由数域F上的一个n阶方阵A所决定的线性变换DA：Mn（F）→Mn（F）,X→AX—XA的不动点。主要结果如下：（1）由DA的全体不动点组成的集合构成矩阵空间Mn（F）的一个子空间,并且这个子空间中的每一个矩阵都是幂零矩阵;（2）如果A是可对角化矩阵,那么由DA的不动点组成的子空间,其维数不超过ψ（n）,这里n≥2,并且当n为奇数时,ψ（n）=1／4（n^2—1）,当n为偶数时,ψ（n）=1／4n^2;（3）如果m=p1q1＋p2q2＋…＋psqs且p1＋q1＋p2＋q2＋…十ps＋qs≤n,那么存在一个一个n阶方阵A,使得由DA的不动点组成的子空间,其维数等于m,这里p1,q1,p2,q2,…ps,qs都是正整数;（4）如果DA是矩阵空间Mn（C）上的线性变换,那么DA有非零不动点当且仅当存在A的两个特征值,其差等于1。这里n≥2,并且C表示复数域。 相似文献
20.
广义绝对值方程是绝对值方程的推广,证明了其等价于广义线性互补问题,探讨了广义绝对值方程解唯一存在的条件,这些结果也推广了Mangasarian在文献[1]中的结论,提出了广义绝对值方程解唯一存在的几个充要条件．最后,给出了广义绝对值方程的一个迭代算法,理论分析和数值结果均说明该方法是有效的． 相似文献