Drought is a phenomenon that threating water quality in addition to its shortage. In this paper we investigate the effect of drought on surface water quality of Kashkan watershed. For this purpose, during the collection of meteorological data and water quality data during 20 years (1987 to 2009) from Meteorology and Water Resources offices of Lorestan province, initially duration and severity o...

abstract the influence of cation?? and anion?? interactions on the strength and nature of n…h hydrogen bond has been investigated by quantum chemical calculations in s-triazine…3hf complex. ab initio calculations were performed at mp2/6-311++g(d,p) level of theory. the natural bond orbital (nbo) analysis and the bader’s quantum theory of atoms in molecules (aim) were also used to elucidate t...

the main objective in sampling is to select a sample from a population in order to estimate some unknown population parameter, usually a total or a mean of some interesting variable. a simple way to take a sample of size n is to let all the possible samples have the same probability of being selected. this is called simple random sampling and then all units have the same probability of being ch...

Vegetation changes can change the rainfall and temperature cycle and also climate fluctuations, especially temperature and precipitation parameters, have significant effects on vegetation. Climate change causes restriction for plant activities which cause changes in vegetation indices including NPP. Considering that Qazvin plain has been affected by climate fluctuations and drought in recent ye...

Decrease of aquifer recharge, Increased pumping through deep wells for agricultural purposes, increases in temperature and evapotranspiration, climate change and change the type of precipitation induced reduce of water level and water table which is called Groundwater Drought. Identifying, monitoring and characterization of drought is very important for water resources planning. The object of t...

abstract: advertisements are the most accessible type of authentic materials, and this is one reason why they are used more and more in english teaching classes. for this cause, studies in the field of advertisements are very widespread nowadays. for pun is one aspect which makes advertisements more interesting, it is used more than before in advertisements. use of puns makes an advertisement m...

today, scouring is one of the important topics in the river and coastal engineering so that the most destruction in the bridges is occurred due to this phenomenon. whereas the bridges are assumed as the most important connecting structures in the communications roads in the country and their importance is doubled while floodwater, thus exact design and maintenance thereof is very crucial. f...

abstract biometric access control is an automatic system that intelligently provides the access of special actions to predefined individuals. it may use one or more unique features of humans, like fingerprint, iris, gesture, 2d and 3d face images. 2d face image is one of the important features with useful and reliable information for recognition of individuals and systems based on this ...