The aim of this study is to evaluate the effect of preheating on composite resins' mechanical and physical properties. preheating of composite resins positively affects the degree of conversion, viscosity, microleakage, marginal adaptation, microhardness and color change however, the flexural strength is adversely affected.

A comprehensive thermodynamic analysis is used to characterize the exergy destruction rate in any part of the solar air preheating system (SAPHS) and calculate its efficiency. The system consists of a solar evaporator, a heat exchanger to air preheating and an auxiliary pump. A computer simulation program using EES software is developed to model and analyses the SAPHS. The system provides preheated air during the year. The thermodynamic analyses involves the determination of effects of air preheating (APH) heat exchanger pinch point temperature, solar radiation intensity and overall heat loss coefficient of the solar evaporator on the performance of the SAPHS. The result showed that the main source of the exergy destruction is the solar evaporator. In the solar evaporator, 115. 9 kW of the input exergy was annihilated. Other main source of exergy annihilation is the APHHE, at 7. 45 kW. The overall energetic and exergetic efficiencies of the SAPHS were 70. 11% and 9. 766%, respectively.

The main problem in the utilization of bran into rice bran oil is easy to rancid because of the high lipase enzyme content. The preheating process on the bran using an oven serves to inactivate the lipase enzyme and increase oil yield. Aim this research is to find out the effect of preheating temperature and preheating time on physical properties (yield, color, and melting point) and chemical properties (free fatty acid, antioxidant activity, phenol levels, and fatty acid profiles) crude black rice bran oil (Oryza sativa L.) cultivar Mutiara. The experimental design used Complete Randomized Design (CRD) with of two factors, the temperature and time heating. The research were analyzed using One Way Anova with significance level α = 0,05. The research showed variations in temperature and pre heating time significant effect on the physical and chemical characteristics of crude black rice bran oil. The preliminary heating treatment at 110°C for 10 minutes is the best treatment. The physical characteristics of yield 9,62%, color is obtained value L* 33,70, a* 2,99, b* 1,08, and whiteness degree 33,62 and melting point 28,50-34,50°C. Chemical characteristics free fatty acid level 18,43%, antioxidant activity 76,69%, and phenol level 0,46%. The fatty acid profiles selected black rice bran oil cultivar Mutiara is myristoleic acid 0,44%, palmitoleic acid 20,04%, elaidic acid 2,01%, linoleic acid 34,91%, linolelaidic acid 0,32%, γ-linolenic acid 38,37%, α-linolenic acid 2,88%, eicosanoic acid 0,65%, and eicosadienoic acid 0,38%. Based on these results, black rice bran oil is suitable for use as cooking oil and oleogel which is applied to fat and oil based spread products.

One of the most important products of tomato is tomato paste and characteristics improvement is noticeable. In this research, the effect of whole and break tomato preheating on consistency and other properties of tomato paste has been studied. The results showed that heating the whole tomato at 85°C resulted in better preserving of pectin, color quality, and improving the consistency. Furthermore, in conventional heating process, increasing the temperature up to 100°C led to keep more quantity of pectin and improving the consistency; however, the color quality decreased significantly.

Background. Due to the effect of pre-heating on the degree of conversion of composite resins and the possible effect on cytotoxicity, the effect of pre-heating of bulk-fill composite resins was investigated on cytotoxicity in this study. Methods. In this study, three different types of composite resin were used, including Tetric N-Ceram Bulk-Fil, Xtrafil, and Xtrabase. From each composite resin, 10 cylindrical samples (5 mm in diameter and 4 mm in height) were prepared, with five samples preheated to 68° C, and the other five samples polymerized at room temperature (25° C). Twenty-four hours after polymerization, cytotoxicity was assessed by MTT assay on human fibroblasts. Statistical analysis of data was carried out with two-way ANOVA and Sidak Post-Hoc. The significance level of the test was determined at 0. 05. Results. There was no statistically significant difference between the mean percentage of cytotoxicity in terms of pre-heating (P>0. 05), but the cytotoxicity of the studied composite resins was significantly different (P<0. 001). The cytotoxicity of Tetric N-Ceram Bulk-fil composite resin was higher than that of the two other composite resins. Conclusion. Pre-heating of bulk-fill composite resin did not affect their cytotoxicity. In addition, the cytotoxicity of different bulk-fill composite resins was not the same.

Background. Due to incomplete polymerization of composite resin restorations, residual monomers adversely affect their mechanical properties and biocompatibility. preheating of composite resins is advised to increase the degree of conversion and reduce monomer elution. This study aimed to analyze the effect of preheating and repeated preheating on the amount of monomer released from a bulk-fill composite resin. Methods. Forty samples were prepared using Filtek One Bulk Fill Restorative composite resin. Samples in one group were fabricated at room temperature, whereas the composite resins in the other groups were cured after 1, 10, or 20 repeated preheating cycles (55 °C), 10 in each group. Eluted urethane dimethacrylate (UDMA) and bisphenol-A-glycidylmethacrylate (BisGMA) monomers were measured with high-performance liquid chromatography (HPLC) 24 hours and 30 days after immersion. The data were evaluated using one-way ANOVA and post hoc Tukey tests. Paired-sample t tests were used to test the differences between time intervals. Results. At both time intervals, the greatest amounts of released BisGMA, UDMA, and total monomers were obtained from the control group, whereas 10 preheating cycles resulted in the least monomer elution. The decrease in monomer elution was not statistically significant after 10 preheating cycles compared with that after one preheating cycle (P>0. 05). The group with 20 preheating cycles showed a greater amount of monomer elution compared to that with 1 and 10 cycles, which was statistically significant (P < 0. 05). The amount of released monomers on day 30 was significantly higher than on day 1 (P<0. 01). Conclusion. preheating of the bulk-fill composite resin was shown to be effective in reducing monomer elution. However, monomer elution was adversely affected after repeated preheating cycles of 20.

Growing worldwide energy demands, the drawbacks of fossil fuels, and global climate change have prompted the creation of sustainable, clean power. One of the viable alternatives to the consumption of fossil fuels is the use of solar energy. Solar photovoltaics (PV) and solar thermal are the most widely accessible solar technology. Hybrid solar systems that make use of Concentrated PV Thermal (CPV/T) technology give an alluring option for the generation of both electrical and thermal energy at the same time. CPV reduces the area of PV receivers while capturing the same amount of solar energy through the use of solar radiation that has been Concentrated on PV cells. However, a notable concern associated with CPV is the elevated temperature of the PV surface, often necessitating the implementation of cooling measures. This problem can be resolved by the implementation of a CPV/T system. Conditions for modeling a novel CPV/T hybrid system embedded Multi Junction Photovoltaic cells (MJPV) and based on Fresnel Lens (FL) have been presented in this research. The Python programming language was utilized to simulate the functioning of a linear concentrated Photovoltaic System (LCPVS). In addition, the influence of cooling fluid and its impact on the efficiency of MJ cells (MJC) were assessed. The findings indicate that the proposed system's average thermal and electrical energy were 7.259 and 3.737 (kWh) respectively. Moreover, the average efficiency of the new design was 34.713% and the amount of potable and hot water has more optimum outcomes.

In this investigation effect of preheating temperature of the GTAW process on weldability of the ferritic ductile cast iron has been studied. The ductile cast iron plates were welded in butt joint design by GTAW with ERNiCu-B wire in different preheats (100-600oc ) temperature. The XRF was used for determining of the chemical analysis of the weld metals. The OM and SEM were used for study of the microstructure characteristics of weld metal, fusion line and HAZ at different samples. In addition tensile, hardness and impact test were used for determining of mechanical properties of the weld metal and HAZ of different samples. The OM and chemical analysis of different samples weld metals result shows , that by increasing of the preheat temperature, the solidification time , percent of dilution, percent of the Fe, Si, Mn, C elements in the weld metals were increased while the tensile strength and hardness of the weld metals were increased. The hardness of UMZ and PMZ were reduced when the preheating temperature increased. The SEM and OM of the HAZ result shows, that the HAZ width increased and the graphite nodule size and volume fraction of the ferrite phase in the microstructure were changed when the preheating temperature increased, also the hardness of the HAZ decreased and impact energy increased. In a general summary, the 400oc is the appropriate temperature for preheating of the welding of the ferritic cast iron by GTAW.

This study deals with the design and analysis of a polygeneration system for the utilization of flare gas to produce power, freshwater, hydrogen, and heat simultaneously. The proposed system, using local resources such as flare gas and Persian Gulf water in the Ahvaz region, consists of a supercritical carbon dioxide power cycle, a thermoelectric generator, crude oil preheating, a reverse osmosis desalination unit, and hydrogen production in a proton exchange membrane electrolyzer. The system modeling was carried out using Engineering Equation Solver software and evaluated based on energy, exergy, and exergoeconomic analyses. The novelty of this research lies in presenting an integrated system that, by using flare gas for the simultaneous production of multiple products, maximizes energy recovery and meets both industrial and domestic needs. The base design results show that the energy and exergy efficiencies of the system are 83.24% and 23.56%, respectively, with a net output power of 12.23 MW and a thermal load capacity of 13.39 MW. Hydrogen production amounts to 60.93 kg/day, and freshwater production equals 106.7 kg/s. Moreover, the total rates of exergy production cost, exergy destruction, and investment are calculated to be 2982.96, 347.58, and 645.84 $/h, respectively, with a payback period of 1.172 years. Finally, a sensitivity analysis was performed to investigate the effect of key variables on the system performance.

To determine the preheating effect on frozen French - fries quality, four potato cultivars: Agria, Marfona, Auozonia & Auola were selected from Faridan region in Isfahan province & transferred to cold storage at temp. =5+0.5 oC and RH=85-90%. At first, some physico – chemical characteristics of potato tubers such as specific gravity and dry matter content were measured by A.O.A.C methods. Also reducing sugar contents were analyzed by “High Performance Liquid Chromatography” (HPLC). The potato strips were blanched in hot water at different condition: 70 oC - 4 min, 70 oC 10 min, 95 oC - 2min and then deep - fat fried at temperature 175 oC for 2 minutes.Product quality properties such as texture, color and oil absorption were determined by standard methods. The data were analyzed using a factorial experiment in a completely randomized design, and average comparisons were made by by Duncan's multiple range test (p < 0.01). The results showed that blanching at 70 oC for 10 minutes markedly improved the quality parameters. Treatment at 95 oC – 2 min did not have any significant effect on Hunter Lab color parameters compared with 70 oC – 10 min. treatment, but the texture was significantly different. The oil absorption increased in strips blanched at 95 oC for 2 minutes. The samples blanched at 70 oC – 4 min had no significant effect on the product quality. In conclusion, Agria & Auola cultivars were more suitable for manufacturing French - fries than the other two varieties.