首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 62 毫秒
1.
The vehicle-scheduling problem involves the design of several vehicle tours to meet a given set of requirements for customers with known locations, subject to a capacity constraint for the vehicles and a distance (or time) constraint for vehicle tours. Three methods of solution are considered in this paper:
  1. a
    A branch-and-bound approach.
     
  2. b
    The "savings" approach.
     
  3. c
    The 3-optimal tour method.
     
The excessive computation time and computer storage required for the first method renders it impracticable for large problems. Ten problems are examined and the results suggest that method C is superior to the other two methods.  相似文献   

2.
We give a complete solution of the following two problems:
  1. (1)
    For which (n, x) does there exist a pair of hexagon triple systems of order n having x inside triples in common?
     
  2. (2)
    For which (n, x) does there exist a pair of hexagon triple systems having x outside triples in common?
     
  相似文献   

3.
This paper describes the techniques used in an enquiry into production planning and stock holding problems encountered by one of our member firms.The investigation of the problem falls into three parts:
  1. i)
    The analysis of demand.
     
  2. ii)
    The determination of optimum stock levels.
     
  3. iii)
    The solution of the allocation problem which arises if the capacity available for the production of stock lines is not equal to the amount required to bring stocks back to the optimum levels. This problem has not been fully investigated, but a proposed method of solution is given in an appendix.
     
  相似文献   

4.
We consider the eigenvalue problems for boundary value problems of second order difference equations
(1)
and
(2)
Comparison results for the eigenvalues of the problem (1) and the problem (2) are established.  相似文献   

5.
We consider all complex projective manifolds X that satisfy at least one of the following three conditions:
  1. (1)
    There exists a pair \({(C\,,\varphi)}\) , where C is a compact connected Riemann surface and
    $\varphi\,:\, C\,\longrightarrow\, X$
    a holomorphic map, such that the pull back \({\varphi^* {\it TX}}\) is not semistable.
     
  2. (2)
    The variety X admits an étale covering by an abelian variety.
     
  3. (3)
    The dimension dim X ≤ 1.
     
We prove that the following classes are among those that are of the above type.
  • All X with a finite fundamental group.
  • All X such that there is a nonconstant morphism from \({{\mathbb C}{\mathbb P}^1}\) to X.
  • All X such that the canonical line bundle K X is either positive or negative or \({c_1(K_X)\,\in\,H^2(X,\, {\mathbb Q})}\) vanishes.
  • All X with \({{\rm dim}_{\mathbb C} X\, =\,2}\).
  相似文献   

6.
Let (Xω) be a compact connected Kähler manifold of complex dimension d and \({E_G\,\longrightarrow\,X}\) a holomorphic principal G–bundle, where G is a connected reductive linear algebraic group defined over \({\mathbb{C}}\). Let Z(G) denote the center of G. We prove that the following three statements are equivalent:
  1. (1)
    There is a parabolic subgroup \({P\,\subset\,G}\) and a holomorphic reduction of structure group \({E_P\,\subset\,E_G}\) to P, such that the corresponding L(P)/Z(G)–bundle
    $E_{L(P)/Z(G)}\,:=\,E_P(L(P)/Z(G))\,\longrightarrow\,X$
    admits a unitary flat connection, where L(P) is the Levi quotient of P.
     
  2. (2)
    The adjoint vector bundle ad(E G ) is numerically flat.
     
  3. (3)
    The principal G–bundle E G is pseudostable, and
    $\int\limits_X c_2({\rm ad}(E_G))\omega^{d-2}\,=\,0.$
     
If X is a complex projective manifold, and ω represents a rational cohomology class, then the third statement is equivalent to the statement that E G is semistable with c 2(ad(E G )) = 0.
  相似文献   

7.
Consider the random entire function
$f(z) = \sum\limits_{n = 0}^\infty {{\phi _n}{a_n}{z^n}} $
, where the ? n are independent standard complex Gaussian coefficients, and the a n are positive constants, which satisfy
$\mathop {\lim }\limits_{x \to \infty } {{\log {a_n}} \over n} = - \infty $
.
We study the probability P H (r) that f has no zeroes in the disk{|z| < r} (hole probability). Assuming that the sequence a n is logarithmically concave, we prove that
$\log {P_H}(r) = - S(r) + o(S(r))$
, where
$S(r) = 2 \cdot \sum\limits_{n:{a_n}{r^n} \ge 1} {\log ({a_n}{r^n})} $
, and r tends to ∞ outside a (deterministic) exceptional set of finite logarithmic measure.
  相似文献   

8.
The purpose of this paper is to discuss and if possible to dispel the industrialist's misunderstanding of operational research. The author lists some of the varied ideas held by industrialists of operational research including several which are contradictory, as for example (a) That operational research is new and revolutionary; and (b) That operational research proves nothing new and has always been practised without being so named.A number of suggestions are then made and developed, which should lead to a better understanding. These include, clearer definitions of operational research and a better adaptation of the specialized literature to the needs of industrial management, with particular emphasis on the publication of real rather than synthetic case histories. Headings of sections are:
  1. 1
    The attitude of industrialists.
     
  2. 2
    The exact nature of operational research.
     
  3. 3
    Problems, criteria, models.
     
  4. 4
    The practice of operational research in business.
     
  相似文献   

9.
We further develop the method, devised earlier by the authors, which permits finding closed-form expressions for the optimal controls by elastic boundary forces applied at two ends, x = 0 and x = l, of a string. In a sufficiently large time T, the controls should take the string vibration process, described by a generalized solution u(x, t) of the wave equation
$$u_{tt} (x,t) - u_{tt} (x,t) = 0,$$
from an arbitrary initial state
$$\{ u(x,0) = \varphi (x), u_t (x,0) = \psi (x)$$
to an arbitrary terminal state
$$\{ u(x,T) = \hat \varphi (x), u_t (x,T) = \hat \psi (x).$$
  相似文献   

10.
Let X be a metric space andμa finite Borel measure on X. Let pμq,t and pμq,t be the packing premeasure and the packing measure on X, respectively, defined by the gauge (μB(x,r))q(2r)t, where q, t∈R. For any compact set E of finite packing premeasure the authors prove: (1) if q≤0 then pμq,t(E)=pμq,t(E);(2)if q>0 andμis doubling on E then pμq,t(E) and pμq,t(E) are both zero or neither.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号