variability

In the present study, concepts related to climate change and climate study scales have been studied and various indicators related to climate change have been presented and then important and practical indicators in evaluating climate change components have been evaluated.

Monitoring the changes in extreme climatic events requires data in short-term time scales. The 32 indicators used in the present study were evaluated and classified into two categories related to rainfall and temperature. Rainfall indices included maximum rainfall and heavy rainfall, maximum number of consecutive dry and wet days, total wet day rainfall, seasonal rainfall index (SI). In addition, regarding temperature, the glacial day (FD) indices, tropical days and nights, hot and cold, minimum and maximum temperature in daily and monthly time scales, range of circadian temperature changes (DTR) and length of growing season (GSL) were assessed.

In selecting the appropriate index for assessing climate change, the length of the existing statistical period, existing of missing data, time scale of the data (hourly, daily, monthly, annual) and the purpose of the research should be considered. In the assessing drought and water balance, the mean values ​​and timing indices would be a good option. While, in studying the flow regime and hydrologic modeling, the daily data flow produce satisfying results. In assessing vegetation change due to climatic factors, as well as groundwater fluctuations, seasonal indicators of rainfall distribution and timing will be better. Average or minimum and maximum and daily or annual indicators will be used to predict changes in climatic variable.

The introduced indicators can be used in selection of suitable climatic variables and adaptive management approaches to climate change challenges. In general, the selection of the appropriate index depends on the available data and the purpose of the research, and the statistical methods used in interpreting the variables will affect the choice of the index.

The main purpose of this study was to select a preventive and maintenance net strategy to improve the assessment indexes of dependability and variability in a company providing the gas and oil machinery and equipment for oil and gas production. The research method was an applied and experimental one. To gather the data, the standard daily visit, the cause and effect analysis of using lathe damages of nine machine system during the two study phases were investigated. The research hypotheses, after confirming the normality of the data, were analyzed through mean hypothesis of one population, paired T- test, and between group correlation coefficient. In the first phase, the inclusive net strategy based on mean time for maintenance and net based on dependability were administered. In the second phase the combined net strategy was administered. In both phases the mean time indexes between failure and repair were assessed to see the effects of three compared strategies and the best net strategy was chosen. The results showed that the combined net strategy produced the improvement of the assessment indexes of dependability and variability and also increased the productivity of machinery and equipments.

The aim of this study was to evaluate the variability of Tavanmand engineering firm، due to instrumental changing in the way of control equipment from manually install to technical. In this way، the theoretical literature review explores change management and resistance to change and methodology is based on quantitative data collection and analysis. The results of data analysis indicate that the engineer’s Awareness of the need to change، Willingness to change and retrofitting (the support of) has a high average. But the engineer’s Knowledge about the Change and Changing skills has low average. At the end، recommendations are offered to improve the variability of engineers.