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181.
马尾松幼龄阶段的生长规律 总被引:3,自引:0,他引:3
薛建辉 《南京林业大学学报(自然科学版)》1987,30(3):48
<正>研究表明,马尾松幼树顶芽大小和春梢长度呈正相关。计算得出估测高生长量的Logistic方程和Ⅱ型S型曲线方程。春梢生长速率和气温的关系最为密切,适于春梢生长的旬平均气温为10~30℃,20℃左右生长速率最大。直径月生长量的季节变化与月降雨量及日平均净光合率的季节波动相一致。一年生叶的日平均净光合率于5月底达一年中最大值,7~9月由于干旱而明显下降,10月达一年中的第二峰值。 相似文献
182.
A series of nanocatalysts consisting of acid treated carbon nanotubes (CNTs) with different diameters (8-15, 20-30, 30-50, >50 nm) supporting platinum (Pt) nanoparticles (Pt/CNTs) were synthesized via a microwave-assisted ethylene glycol method. The as-synthesized catalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). Their catalytic performances in the oxygen reduction reaction (ORR) were evaluated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The experimental results showed that the diameter of the CNTs influences the particle size, loading, and dispersion of Pt NPs. Furthermore, the Pt/CNTs having different CNT diameters displayed different catalytic activities in the ORR. The catalyst Pt/CNT8, which was prepared by using CNTs with diameters ranging between 8-15 nm as the support, exhibited the highest Pt loading, catalytic activity, and stability in the ORR. The mass activity of Pt/CNT8 was determined to be 0.188 A·mg-1 at 0.9 V, which is folds higher than that of the commercially available JM Pt/C catalyst. After testing the stability for 5000 potential cycles, the negative shift (~7 mV) of the half-wave potential for Pt/CNT8 was found to be significantly lesser than that for the JM Pt/C catalyst (~32 mV), indicating superior catalytic stability. 相似文献
183.
This article studies the zero divisor graph for the ring of Gaussian integers modulo n, Γ (? n [i]). For each positive integer n, the number of vertices, the diameter, the girth and the case when the dominating number is 1 or 2 is found. Complete characterizations, in terms of n, are given of the cases in which Γ (? n [i]) is complete, complete bipartite, planar, regular or Eulerian. 相似文献
184.
185.
2族3-紧优的有向双环网络无限族 总被引:4,自引:0,他引:4
该文给出一种寻找k-紧优的双环网络无限族(k≥0)的方法,利用此方法得到了2族 3-紧优的有向双环网络无限族. 相似文献
186.
The bandwidth B(G) of a graph G is the minimum of the quantity max{|f(x)−f(y)| : xyE(G)} taken over all proper numberings f of G. The composition of two graphs G and H, written as G[H], is the graph with vertex set V(G)×V(H) and with (u1,v1) is adjacent to (u2,v2) if either u1 is adjacent to u2 in G or u1=u2 and v1 is adjacent to v2 in H. In this paper, we investigate the bandwidth of the composition of two graphs. Let G be a connected graph. We denote the diameter of G by D(G). For two distinct vertices x,yV(G), we define wG(x,y) as the maximum number of internally vertex-disjoint (x,y)-paths whose lengths are the distance between x and y. We define w(G) as the minimum of wG(x,y) over all pairs of vertices x,y of G with the distance between x and y is equal to D(G). Let G be a non-complete connected graph and let H be any graph. Among other results, we prove that if |V(G)|=B(G)D(G)−w(G)+2, then B(G[H])=(B(G)+1)|V(H)|−1. Moreover, we show that this result determines the bandwidth of the composition of some classes of graphs composed with any graph. 相似文献
187.
Raymond Viglione 《Acta Appl Math》2008,104(2):173-176
Let q be a prime power,
the field of q elements, and n≥1 a positive integer. The Wenger graph W
n
(q) is defined as follows: the vertex set of W
n
(q) is the union of two copies P and L of (n+1)-dimensional vector spaces over
, with two vertices (p
1,p
2,…,p
n+1)∈P and [l
1,l
2,…,l
n+1]∈L being adjacent if and only if l
i
+p
i
=p
1
l
i−1 for 2≤i≤n+1. Graphs W
n
(q) have several interesting properties. In particular, it is known that when connected, their diameter is at most 2n+2. In this note we prove that the diameter of connected Wenger graphs is 2n+2 under the assumption that 1≤n≤q−1. 相似文献
188.
Let γ
pr
(G) denote the paired domination number of graph G. A graph G with no isolated vertex is paired domination vertex critical if for any vertex v of G that is not adjacent to a vertex of degree one, γ
pr
(G – v) < γ
pr
(G). We call these graphs γ
pr
-critical. In this paper, we present a method of constructing γ
pr
-critical graphs from smaller ones. Moreover, we show that the diameter of a γ
pr
-critical graph is at most and the upper bound is sharp, which answers a question proposed by Henning and Mynhardt [The diameter of paired-domination
vertex critical graphs, Czechoslovak Math. J., to appear].
Xinmin Hou: Research supported by NNSF of China (No.10701068 and No.10671191). 相似文献
189.
We study diameter preserving linear bijections from onto where X, Y are compact Hausdorff spaces and V, Z are Banach spaces. For instance, we obtain that if X has at least four points, Z is linearly isometric to V and either Z is a space or Z* is strictly convex or smooth, then there is a diameter preserving linear bijection from onto if and only if X is homeomorphic to Y. We also consider the case when X and Y are not compact but locally compact spaces. 相似文献
190.
On the spectral radius of unicyclic graphs with fixed diameter 总被引:1,自引:0,他引:1