Let t(n, d) be the minimum number t such that there are t of the n lattice points {(x1, . . . , xd) : 1 ≤ xi ≤ n} so that the ( t 2 ) lines that they determine cover all the above n lattice points. We prove that for every integer d ≥ 2 there are two positive constants c1 = c1(d) and c2 = c2(d) such that for every n c1n d(d−1)/(2d−1) ≤ t(n, d) ≤ c2n log n. The special case d = 2 settles a proble...

Article history: Received 21 April 2008 Received in revised form 13 May 2009 Accepted 14 May 2009 Available online 27 May 2009 This paper assumes that the decision makers of OPEC (or at least of its core members) are interested in both profits and political payoffs (support, popularity, being a hero of the Arab or Islamic street, etc.). The oil weapon, i.e. a reduction of output is the most pow...

abstract in the 7th and 8th centuries of hijri, kish island had been the maritime trade center of the persian gulf under the reign of  bani gheisar government, and any changes in this area has affected the neighboring areas and further lands. the objective of this essay is to study the economic changes of kish island and its excellent position in the maritime trade of the persian gulf, oman sea...

Today, transportation is one of the substructure parts of society that not only affects the economical growth process, but also is changed in development. The transportation substructure is one of the substructure parts of services has an important position in the economical development of countries. An efficient and appropriate transportation network causes goods transportation and services co...