Performance Investigation of Evacuated Tube Collector using Different Nano fluids Applied to Winter Climatic Conditions in Egypt

In this paper, the performance of the evacuated tube solar collector is investigated theoretically by the TRNSYS program. The simulation is conducted during the winter of 14th February-2019 in Cairo – Egypt. In this simulation, water and Nanofluids areworking fluids. The types of Nanofluids are CeO2/water, WO3/water and AL2O3/water. The simulation is conducted at0.015%,0.025%, 0.035% and 0.045% (volume concentrations).The mass flux rate and tilt angle are 0.017 kg/s.m2and 45o; respectively.The results show that the collector has the highest performance using nanofluids at studied concentrations. At 12:00 PM, thehighest useful energy gain can be obtained from CeO2/water Nanofluid at 0.045% concentration, while thermal efficiency ishigher by 34.2% than water. The nanofluidWO3/water presents low performance than that of CeO2/water and AL2O3/water. The thermal efficiencies ofAL2O3/ water and WO3/ water Nanofluids are higher than water by 28.4% and 12.5%; respectively, atconcentration of 0.045% and 12:00P

Using a combination of industrial and agricultural wastes to manufacture sustainable ultra-high-performance concrete

Today, recycling and the use of eco-friendly construction supplies are major concerns for the environment. Concrete is frequently utilized in the engineering and construction sectors. In the past several decades, ultra-high performance concrete (UHPC), characterized by very high mechanical qualities, has emerged as one of the most popular types of concrete. Huge quantities of Ordinary Portland cement (OPC) are often utilized; this increases the price of UHPC, limits its widespread usage in structural applications, produces a substantial quantity of carbon dioxide, and uses a sizable amount of natural resources. It is recommended that other additives be used in lieu of OPC in concrete preparation and that recycled aggregates from a variety of sources be used in place of natural aggregates to make UHPC production more environmentally friendly and economically feasible. This study combines industrial and agricultural waste to create an affordable and sustainable UHPC. For example, glass particles (GP) as a manufacturing byproduct generated by glass waste (GW) are utilized as an alternative for fine aggregate ''sand (S)'' with substitution ratios of 0 %, 50 %, and 100 %, while wheat straw ash (WSA), as an agricultural byproduct, is utilized as an OPC substitute at varying substitution ratios 0 %, 10 %, 20 %, and 30 %. We conducted and analyzed experiments with 12 mixtures divided into three groups. Several factors are studied, including slump flow, mechanical characteristics, drying shrinkage, high temperature, and microstructural features. Based on the obtained outcomes, boosting the percentage of GP utilized to substitute the S made it more workable. In addition, replacing 20 % of the OPC with WSA and 0 % of the S with GP yielded the best results in terms of mechanical characteristics. Increasing the WSA replacement rate while fixing GP to S substitution level significantly reduced drying shrinkage values. Lastly, the compressive strength (fc) findings of UHPC structural components exposed to elevated temperatures up to 200 °C were enhanced using GP as a replacement for S. In brief, the results of this experimental investigation can contribute well to illustrating the effect of utilizing GP and WSA to manufacture sustainable ultra-high-performance concrete

Comparative Evaluation of Accuracy of Different Apex Locators: Propex IQ, Raypex 6, Root ZX, and Apex ID with CBCT and Periapical Radiograph—In Vitro Study

Objectives. This study aimed to validate the accuracy of working length (WL) measurements obtained with the newly introduced Propex IQ apex locator and to compare it with the latest generations of other electronic apex locators, CBCT, and conventional periapical radiographs by using the actual WL measurements obtained by using an endodontics microscope as a reference. Materials and Methods. Thirty-five extracted single-rooted human mandibular first premolars with curvatures from 10° to 20° were selected according to the inclusion and exclusion criteria and cut at the cementoenamel junction to achieve a standard reference point for WL determination. The actual WL was obtained by inserting a size-15 k-file in the root canal until the tip of the file was visible under an endodontic microscope. The definitive WL was measured using Propex IQ (Dentsply Sirona), Raypex 6 (VDW Dental), Root ZX (Morita), and Apex ID (Kerr Dental). In addition, radiographic WL was obtained using periapical radiographs and CBCT. One-way ANOVA was used for comparisons of the WL values, with a p value < 0.05. The percentage of success of each method for determination of the definitive WL was assessed using cross-tabulation and chi-square tests. Results. CBCT radiographs and Propex IQ apex locator yielded the most accurate WL measurements in comparison with the actual WL measurements (p<0.05). Raypex 6, Root ZX, and Apex ID yielded more accurate WL measurements than conventional periapical radiographs (p<0.05). Periapical radiographs yielded the least accurate WL measurements in comparison with the actual WL values (p<0.05). Conclusions. Within the limitations of this study, the Propex IQ apex locator showed higher accuracy than Raypex 6, Root ZX, and Apex ID for WL determination in the root canal. Nevertheless, CBCT radiographs yielded the maximum accuracy for WL measurements