令圖G 是一個簡單圖。一個圖G 的分配是一個函數,它將G 中的每一個點對應到一個非負整數,其中對圖G中的每一個點v, $delta(v)$表示點所分配到的圓石數目。一步圓石移動為將G 中的一個點移除兩顆圓石,然後放一顆圓石到它的鄰點。一個圖G 的分配為t倍可解如果無論選擇哪個目標點v,都可 以使用圓石移動來搬動t 顆圓石到v。圖G的最優t-圓石分配數, 以$pi^*_t (G)$表示,為G中所有t倍可解的分配,使用最少的圓石數目。當t=1時,最優t-圓石分配數就是最優圓石分配數 在這篇論文中,我們主要研究一個圖的最優圓石分配數。在第一章中,我們介紹論文研究的背景知識以及一些基本定義。此外為了讓這篇論文更完整,在第二章中,我們也介紹一些最優圓石分配數和最優t-圓石分配數的已知結果。 第三章中,我們研究環的最優t-圓石分配數,我們所得到的結果為求出$pi^*_2(C_n)$的確切值以及找到t大於或等於3 時$pi^*_t(C_n)$的 上界與下界。而在第四章中,我們以$T^m_h$ 來表示一個高度為h的完整m元樹,然後證明出$pi^*_2(T^2_h ) = pi^* (T^2_{h+1})$ 和$pi^*_4(T^2_h ) = pi^* (T^2_{h+2})$兩個結果。最後我們也求出$pi^*_3(T^2_h)$的3的確切值。在第五章,我們對本篇論文的研究成果做個總結。
Let $G$ be a simple graph. A distribution $delta$ of $G$ is a mapping from $V(G)$ into the set of non-negative integers, where $delta(v)$ is the number of pebbles distributed to the vertex $v$ for each $vin V(G)$. A {it pebbling move} consists of removing two pebbles from one vertex and then placing one pebble at an adjacent vertex. A distribution of a given graph $G$ is $t$-fold solvable if, whenever we choose any target vertex $v$ of $G$, we can move $t$ pebbles on $v$ by using pebbling moves. The optimal $t$-pebbling number of the graph $G$, denoted by $pi^*_{t}(G)$, is the minimum number of pebbles necessary so that there is a $t$-fold solvable distribution of $G$. When $t=1$, the optimal $t$-pebbling number is the optimal pebbling number. In this thesis, we mainly study the optimal $t$-pebbling number of a graph. In Chapter $1$, we introduce the background of this study and give some basic definitions. For completeness, we also introduce the known results on the optimal pebbling number and the optimal $t$-pebbling number of a graph in Chapter $2$. In Chapter $3$, we study the optimal $t$-pebbling number of the cycle. As a consequence, we determine the exact value of $pi^*_{2}(C_{n})$ for each cycle $C_n$. We then derive an upper bound and a lower bound for $pi^*_{t}(C_{n})$ for $tgeq 3$. In Chapter $4$, let $T^m_h$ denote the complete $m$-ary tree with height $h$, we first show that $$pi^{ast}_{2}(T^2_{h})=pi^{ast}(T^2_{h+1})qquad ext{and} qquad pi^{ast}_{4}(T^2_{h})=pi^{ast}(T^2_{h+2})$$ and then determine the exact value of $pi^{ast}_{3}(T^2_{h})$. In Chapter $5$, we conclude our research results in this thesis.