氨吸收式串联型动力/制冷复合循环

本文提出了一种新型的采用氨水混合工质的动力／制冷复合循环,该循环以中低温工业余热或燃气轮机排气为热源,将动力、制冷子循环采用串联方式连接,基础循环工质为氨质量浓度为0．27的氨水溶液,热源为365℃／104．3 kPa 的热空气,透平进气参数为350℃／3750 kPa,,以热效率η1、(火用)效率η2作为评价准则,模拟计算表明本循环的热效率η1 为17．8％,炯效率η2为45％,通过与其它有代表性的分供系统及联供系统进行热力性能方面的比较,表明本循环η1、η2均有不同程度提高。     

论连通图的可重构性

本文我们利用带权核子图的可重构性证明了连通图是可重构的,从而证明了重构猜想为真.     

On the dimension of almost -dimensional spaces

Oversteegen and Tymchatyn proved that homeomorphism groups of positive dimensional Menger compacta are -dimensional by proving that almost -dimensional spaces are at most -dimensional. These homeomorphism groups are almost -dimensional and at least -dimensional by classical results of Brechner and Bestvina. In this note we prove that almost -dimensional spaces for are -dimensional. As a corollary we answer in the affirmative an old question of R. Duda by proving that every hereditarily locally connected, non-degenerate, separable, metric space is -dimensional.

     

2-阶邻域连通无爪图的Hamilton性

设Ｇ是无爪图．对ｘ∈Ｖ（Ｇ），若Ｇ［Ｎ（ｘ）］不连通，则存在ｙｉ∈Ｖ（Ｇ）－｛ｘ｝（ｉ－１，２），使｜Ｎ（ｙｉ）∩Ｋｉ（ｘ）｜≥２，且｜Ｎ（ｙｉ）∩Ｎ（Ｋｉ＋１（ｘ））｛ｘ｝｜≥２（ｉ模２），那么称无爪图Ｇ是强２－阶邻域连通的，其中Ｋ１（ｘ），Ｋ２（ｘ）分别表示Ｇ［Ｎ（ｘ）］的两个分支．本文证明了：连通且强２－阶邻域连通的无爪图是Ｈａｍｉｌｔｏｎ图．     

On <Emphasis Type="Italic">k</Emphasis>- critical 2<Emphasis Type="Italic">k</Emphasis>- connected graphs

A graph G is called an (n,k)-graph if κ(G-S)=n-|S| for any S ? V(G) with |S| ≤ k, where ?(G) denotes the connectivity of G. Mader conjectured that for k ≥ 3 the graph K_2k+2?(1-factor) is the unique (2k, k)-graph. Kriesell has settled two special cases for k = 3,4. We prove the conjecture for the general case k ≥ 5.     

Almost Connected Orders

One of the standard axioms for semiorders states that no three-point chain is incomparable to a fourth point. We refer to asymmetric relations satisfying this axiom as almost connected orders or ac-orders. It turns out that any relation lying between two weak orders, one of which covers the other for inclusion, is an ac-order (albeit of a special kind). Every ac-order is bracketed in a natural way by two weak orders, one the maximum in the set of weak orders included in the ac-order, and the other minimal, but not necessarily the minimum, in the set of weak orders that include the ac-order. The family of ac-orders on a finite set with at least five elements is not well graded (in the sense of Doignon and Falmagne, 1997). However, such a family is both upgradable and downgradable, as every nonempty ac-order contains a pair whose deletion defines an ac-order on the same set, and for every ac-order which is not a chain, there is a pair whose addition gives an ac-order.     

A Distance-Regular Graph with Strongly Closed Subgraphs

Let be a distance-regular graph of diameter d, valency k and r := maxi | (c _i,b _i) = (c ₁,b ₁). Let q be an integer with r + 1 q d – 1.In this paper we prove the following results: Theorem 1 Suppose for any pair of vertices at distance q there exists a strongly closed subgraph of diameter q containing them. Then for any integer i with 1 i q and for any pair of vertices at distance i there exists a strongly closed subgraph of diameter i containing them. Theorem 2 If r 2, then c _2r+3 1.As a corollary of Theorem 2 we have d k ²(r + 1) if r 2.     

On locally convex hypersurfaces in Hadamard manifolds

Locally convex compact hypersurfaces immersed in a hollow simply connected Riemannian space of nonpositive sectional curvature are considered. They are proved to be convex hypersurfaces homeomorphic to the sphere. A similar result for immersed hypersurfaces with nonpositive definite second quadratic form of rank no smaller than one is obtained. Translated fromMatematicheskie Zametki, Vol. 67, No. 4, pp. 498–507, April, 2000.