in this paper we study finding the $(k,l)$-core problem on a tree which the vertices have positive or negative weights. let $t=(v,e)$ be a tree. the $(k,l)$-core of $t$ is a subtree with at most $k$ leaves and with a diameter of at most $l$ which the sum of the weighted distances from all vertices to this subtree is minimized. we show that, when the sum of the weights of vertices is negative, t...

Let $x$ and $y$ be two distinct vertices in a connected graph $G$. The $x,y$-location of a vertex $w$ is the ordered pair of distances from $w$ to $x$ and $y$, that is, the ordered pair $(d(x,w), d(y,w))$. A set of vertices $W$ in $G$ is $x,y$-located if any two vertices in $W$ have distinct $x,y$-location.A set $W$ of vertices in $G$ is 2-located if it is $x,y$-located, for some distinct...

Capacity of garden productions in Iran is such that is accounted as a country that produces thirteen garden products in the world but despite excellent condition in Iran for producing garden products, natural disasters damage production of fruits in the country therefore farmers incur a loss. Pistachio tree has been in danger of destruction and dryness. Thus, in order to reduce loss incurred on...

Tree structures occur throughout the theory of information storage. Typically each tree node contains some data information and some pointers to other tree nodes. In most cases the number k of pointer fields is fixed and the structure is referred to as a k-way tree. More formally, a k-way tree can be defined as being either empty (having no nodes) or as consisting of a root node together with a...

Xylem sap flux density (Fd) was measured, on a 43-year-old (mature) and three 4-year-old (young) mango (Mangifera indica L.) trees, using Granier-type probes. The relative influences of environmental variables were examined under well-watered condition. Circumferential variation in Fd was also investigated by placing sensors on the north, south-west and south-east sides of the mature tree. Sap ...

mountains and trees have many similarities. in this way, simorgh of shahnameh shifts from the tree of vispobish to alborz mountain. if simorgh has spiritual existence in avesta, a devilish side has been added to it in shahnameh. in avesta, it lives on a tree, but in shahnameh we find him on alborz mountain. all the researches done on shahnameh and iranian mythology did not pay any attention to ...