平原区河道流速分布规律及其在横向声学多普勒流量测验系统中的应用

横向声学多普勒流速仪(H-ADCP)因其测验的自动高效和信息传输的快捷在流量测验中得到广泛应用。针对现状代表流速选取存在水文物理含义不明的缺点,根据垂线流速分布理论模型,并结合实测垂线流速资料,提出了平原区不同类型河道流速分布拟合模型,并实际引用。应用结果表明：基于幂指数函数和一元多项式函数拟合的流速分布模型能够用于H-ADCP层流速到垂线流速的转化,率定的单断关系精度可靠,可为H-ADCP测流系统流速率定单断关系提供新的方法。     

On comparingLL(k) andLR(k) grammars

A new and rigorous proof of the well-known fact thatLL(k) grammars areLR(k) grammars is provided. The proof is elementary in the sense that it is directly based on relations defining leftmost and rightmost derivations and no additional formalism is needed.     

Embeddings ofPSL(2, 41) andPSL(2, 49) inE8(C)

We classify embeddings of the finite simple groups PSL(2, 41) andPSL (2, 49) into algebraic groups of type E₈in characteristic not dividing the orders of these respective groups. Lie theory and finite group theory point to families of elements in a group of typeE₈ over a finite field which might satisfy a presentation for our finite simple group. Techniques from computational representation theory identify all suitable systems of generators. We describe a number of methods of computation in Chevalley groups of type E₈.     

The numerical solution of the time-dependent matrix equation A(t)V(t) + WA(t) = G(t)

A rapidly convergent iterative method for the solution of matrix equations of the form

A(t)V(t) + WA (t) = G(t)

is outlined. Such matrix equations arise in the study of parabolic systems and in the application of Lyapunov methods in the stability analysis of linear time-invariant systems. The desired solution at each time step is obtained by solving a comparatively small ordered matrix equation of the form

AV + WA=G rather than resorting to the conventional systems of linear algebraic equations with a composite coefficient matrix of order mn × mn.     

LL(1) grammars and Sub-LL(1) grammars

LL(1) grammars play an important role in top-down parsing. In order to improve their efficiency, this paper presents a new type of grammar, Sub-LL(1), based on LL(1), and shows that there is a grammar which is Sub-LL(1) and not LL(1) though LL(1)- and Sub-LL(1)-languages are identical.     

Zeros of f(z) = (az-b)npm (cz-d)n

The zeros off(z) = (az - b)^{n} pm (cz - d)^{n}are found to lie on a circle of radius|(ad - cb)/(|a|^{2} - |c|^{2})|with its center atz = (a^{ast}b - c^{ast}d)/(|a|^{2} - |c|^{2}), wherea, b, c, anddare complex numbers andnis assumed real. When|a| = |c|the locus of the zeros is a straight line perpendicular to the line joining the pointsb/aandb/cand intersecting it atz = 0.5(b/a + d/c). The zeros are found analytically and constructed geometrically.     

德州仪器最新DualCool~(TM) NexFET~(TM)功率MOSFET

<正>在标准封装尺寸下将散热效率提升80%、允许电流提高50%随着许多标准架构(PCI、AT-CA),电信及服务器机柜的尺寸越来越小,功率密度会越来越大。在相同尺寸下,PCB板上集成的芯片越来越多,从而导致其电流不断增加。所     

组合公钥（CPK）体制标准（v5．0）

1引言 组合公钥体制（Combined Public Key Cryptcwaem,简称CPK）,是在椭圆曲线密码（ECC）上,由组合矩阵和分割密钥序列构成。ECC遵从IEEE标准。     

LR(0) grammars generated by LR(0) parsers

Summary Let be an LR(0) parser of a given LR(0) grammar G. Generally, does not only parse the words generated by G but also the words of some other LR(0) grammars different from G. In this paper we shall define a class of LR(0) parsers and shall present a characterization and a method for the construction of all LR(0) grammars which can be parsed by a given LR(0) parser.