The purpose of this study was to conduct a meta-analysis that shows the effects of fiber on ultimate compressive ultra-high performance concrete and its tensile strengths. The internet scholarly search engines and ScienceDirect article references were used to illustrate the papers concerning the experimental investigations of mechanical properties of ultra-high strength concrete with and without fiber with clearly, completely and comparative raw data.The normal concrete test results were dismissed from this search. Seven trials were identified based on the adopted inclusion and exclusion criteria above. The meta-analysis based on standardized mean difference was carried out on the basis of a fixed-effects model for the major outcomes of the ultimate compressive and tensile properties of ultra-high performance concrete. A total of 888 test specimens were enrolled in these seven trials. The combined analysis yielded a sign of a significant improvement in ultimate compressive and tensile ultra-high performance concrete strengths with fiber addition of 2% by concrete volume. The summary effect size of ultimate compressive strength was 2.34 while a more improvement in term of tensile strength with effect size of 2.64. By addition fiber of 2% provides a significant benefit in mechanical properties of ultra-high performance concrete.

The UV radiation of sunlight is considered the main source of microbial germicide and environmental sterilization. The objective of this study includes the estimation of the UV dose amount and time, which required to inactivate coronaviruses by solar exposure. The mean with its confident interval of the unified D90-254 nm inactivation dose (ultraviolet dose for 90% inactivation at 254nm) in several trials published on coronaviruses families, was assumed as ultraviolet susceptibility of the SARS-CoV-2 (COVID-19) virus. The inactivation dose spectrum (sensitivity envelope) for coronaviruses as a function of the UV wavelength equivalent to UVB range (280 to 320 nm) was adopted from literature. The UVB solar measurement intensity at Baghdad's geographical location was used over a year at every fifteen minutes and converted from a lump sum to solar spectrum per wavelength in the range of 280 to 320 nm using a simplified mathematical model. A composite action spectrum was drawn that including the virus sensitivity spectrum normalized to 254 nm, UVB solar measurements spectrum, and inactivation effective dose spectrum for coronaviruses. The area under the inactivation effective dose spectrum was calculated numerically to find the equivalent solar flux. The time required to inactivation the SARS-CoV-2 (COVID-19) virus is predicted for each value of UVB lump sum intensity to simulate the time required to sterility the outdoor surfaces at all months within Baghdad geographical station. the time required for sterilization ranged from 92.9 minutes at solar flux 0.56 J/m2254/min in July, to 371.4 minutes at solar flux 0.14 J/m2254/min in January for the year of data used. This work would be useful to provide the decision-makers with a clear picture of the sterilization process management of the outdoor surfaces and curfew timing arrangement.

In most vibration structural problems, the value of damping is less than unity. Such a small amount of damping may increase near or exceed unity under certain special circumstances. Critically damped and overdamped solutions are completed until the final expressions are generated and an indication provided by MATLAB as to how these expressions depend on viscous damping ratios, natural frequencies, and initial conditions. The developed equations of various damping systems, which are commonly employed in vibration analyses, are compared, with several important observations are noted. Natural frequency is of primary importance when controlling the settling time of critically damped and overdamped vibration responses. Initial conditions are also considered main factors that affect critically damped and overdamped vibration peak responses. Damping plays a crucial role in the peak response of an overdamped system. A direct relationship between the damping ratio and the peak response is observed, whereas an inverse relationship exists between the damping ratio and the settling time. Therefore, critically damped and overdamped systems exhibit an identical response in the large scale perspective, whereby they first rise and then fall. In the zoomed scale, the peak response of the overdamped system is lower than that of the critically damped system, and the latter falls faster than the former. No cyclic response is observed, and the vibration statement is abnormally used for both critically damped and overdamped systems.

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