Abstract: Earth velocity changes under many reasons. They cause variations in the length of daytime. These reasons are; interior changes, which usually occur during events that tend to speed up Earth’s rotation slightly but noticeably, and Outward changes, where material that was typically at one point at a higher elevation on Earth surface falls down to be at a lower point. The first reason may show in several figures like earthquake and condensing core of earth. On the other hand, tide, melting glacier poles, and changing weather they cause the other reason. The amount of time that increasing or decreasing in a day until now do not exceed few seconds, but on the massive scale of time as the age of earth it becomes important value. 

An attempt has been made to evaluate the effect of welding parameters on the weld penetration, weld bead width and heat effective zone of Tungsten Inert Gas (TIG) welded 2 mm 304L stainless steel joints. The welding parameters including arc current, welding travel speed and gas flow rate were used to achieve the optimum joint. Taguchi technique has been implemented to optimize the welding parameters. Orthogonal array L9 (Three factors with three levels 3x3) was used to study the effect of arc current, welding travel speed and gas flow rate on the quality of 304 stainless steel welds. Signal to a noise ratio (SNR) and the analysis of variance (ANOVA) are also used to determine the main effects of different welding parameters on the weld bead width (WB), weld penetration (WP) and heat affected zone (HAZ). Results showed that welding current has significant effect, whereas gas flow rate showed no effect on the quality of 304Lwelded joints. Welding current of 185A, welding speed of 135mm/min and gas flow rate of 15lit/min have been selected as the best process parameter of weld bead width and weld penetration at level three of experiment seven. However, the optimum process parameter for heat affected zone are level one experimental three at165 A, 235 mm/min, 15 lit/min of welding arc current ,travel speed and gas feeding rate, respectively.

ABSTRACT

Water sources in Al-Jabal Al-Gharbi area are very limited and need to be studied for use either as drinking water or human activities. Therefore, several physical and chemical parameters of water sources in Al-Jabal Al-Gharbi region located in Northwest of Libya were investigated. For untreated water three sources were studied including groundwater wells, rain water, and Man-Made River (MMR). However, for drinking water packed and unpacked treated commercial water were investigated. The examined properties were pH, conductivity, salinity, turbidity, total dissolved solids (TDS), chlorine, nitrates (NO- ), nitrites, sulfate, phosphate, iron, and cupper. The results showed that the groundwater and MMR water had high TDS concentrations between 1115 and 4090 mg/L leading to increase the total hardness in these samples. Most of the treated waters had very low of TDS concentrations causing loss the useful salts for consumers . However, the rain water samples had optimum values of TDS and other parameters. Regarding NO- all samples were within the limitation and in the range of 0.02 to 15 mg/L. Furthermore, all metal ions examined in this work such as iron and Cupper were within the WHO guidelines.