Design Of Response Surface Method Research Articles

Performance assessment of mechanical properties of green normal strength concrete produced with metakaolin-cement coated recycled concrete aggregate for sustainable construction

Reusing demolished concrete waste is a promising alternative to natural aggregate for resource conservation and achieving sustainable environment. However, there is a need to improve their quality and performance in new concrete. Therefore, this study aims to examine the mechanical performance of normal strength concrete containing metakaolin-cement coated recycled concrete aggregate (RCA). Three mixture batches were produced at water-cement ratios (w/c) of 0.25 and 0.45. The first batch is control mix, while the second and third batches contained uncoated RCA and metakaolin-cement coated RCA (TRCA) respectively. Materials characterization and workability of fresh concrete mixes were carried out. Compressive and split tensile strengths and water absorption tendency of hardened samples were determined. Morphology of selected concrete samples was analysed with scanning electron microscopy (SEM) with energy dispersive x-ray (EDX). The experimental results were further analysed with central composite design (CCD) response surface method. Results show improvements in the physical properties of RCA aggregates and declining trends in slump values. However, relative to the control mixes, concrete mixes containing TRCA exhibited significant improvement in strength performance and low water absorption tendency compared to RCA concrete mixes. This was corroborated by the response surface models showing that both w/c ratio and TRCA amount significantly influenced the strength and water intake performance of the concrete. The study demonstrated that TRCA can be deployed as an alternative for natural coarse aggregate up to 50% substitution in making normal concrete for structural purposes.

Study on the Performance and Mechanism of Cold-Recycled Asphalt Based on Permeable Recycling Agent.

In order to investigate the influence of recycling agent composition on the recycling effect of aged asphalt in the cold recycling process, the design and optimization of cold recycling agent composition were performed through the central composite design-response surface method combined with the dynamic shear rheometer (DSR) test and the bending beam rheometer (BBR) test. The molecular weight distribution and component changes in aged asphalt before and after the addition of a cold recycling agent were also analyzed by gel permeation chromatography (GPC) and hydrogen-flame ionization test. The results showed that the permeable cold recycling agent has a recycling effect on the aged asphalt, but its effectiveness is greatly affected by recycling agent composition. The best recycling effect was achieved when the ratio of aromatic oil and penetrant in the cold recycling agent was 61.2:38.8, respectively. In terms of the recycling agent and aromatic functional groups in the aromatic oil, the aromatics in the recycling agent are derived from the aromatic oils, and the penetrant is only fused and permeated with the aromatic oils. After the admixture of the cold recycling agent, the penetrant in the recycling agent allows the aromatic oil to enter the aged asphalt at room temperature. The light components volatilized by aging are replenished, allowing the aged asphalt to recover some of its properties.

Application of essential oils and optimizing storage conditions for control of postharvest diseases in apple

Postharvest loss in fruits and vegetables accounts for more than one third of the world production. On the other hand, using chemicals has raised food health concerns, and grown the demand for eco-friendly materials. Given the promising results of essential oil use to control and prevent postharvest decay, we conducted this research. In the present study, a two-step statistical method was used to determine and optimize application of essential oils along with parameters of storage conditions. Significant level of essential oils and storage conditions (temperature, ventilation, and relative humidity) were screened by using PBD method and the best concentration were determined by central composite design of response surface method. The results showed that 1000 and 1500 microgram/l (µg/l) of basil essential oils, and 1500 µg/l of peppermint essential oils reduced the lesion diameter in apple fruits infected with Penicillium expansum. All storage conditions had significant effect on postharvest decay. Based on the CCD of RSM method, the best concentration of essential oils and the optimal level of the storage condition were determined. Furthermore, basil and peppermint treatments reduced rate of the ethylene production during 56 days after treatment. The results of this study revealed and confirmed that basil essential oils as a postharvest treatment under optimized storage conditions can be utilized as a low-cost substrate for controlling postharvest decay in apple.

Performance enhancement of up-flow anaerobic sludge blanket reactor for psychrophilic temperature during the dry season: Kality wastewater treatment plant

The main purpose of wastewater treatment plant (WWTP) is to reduce organic and inorganic pollutants to meet standards. But WWTPs employing up flow anaerobic sludge blanket (UASB) reactors under psychrophilic temperature are currently removing about 55% chemical oxygen demand (COD) and 70% total dissolved solids (TSS). The research was done to increase the treatment efficiencies of UASB reactor working under psychrophilic conditions through optimization of operational parameters like temperature, organic loading rate (OLR), pH and hydraulic retention time (HRT). Experimentation was carried out in a 0.0486 m3 square-shaped pilot-scale UASB reactor. Experimental design response surface method (RSM) for performance enhancement and optimization of UASB reactor operational parameters through five levels of central composite design (CCD) was used. The optimized operational parameters obtained from CCD-RSM were as follows: temperature of 21.58 °C, OLR of 2.99 kg COD/m3.d, HRT of 4.37hrs and pH of 6.3. Using optimized parameters, tests yielded efficiencies of 92.70%, 99.06%, and 94.50% for COD, TSS, and volatile suspended solid (VSS) respectively. The outlet concentrations of alkalinity, and volatile fatty acids (VFA), were found to be lower than the inlet concentrations. The alkalinity in the system accepts the hydrogen ion released by acids and the system is taken over by methanogensis to maintain the pH. The outlet concentration of sulfate ion was found to be increasing due to inhabitation of sulfur-reducing bacteria by an anaerobic condition of VFA and alkalinity at a pH less than 7.8.This process favors the production of CH4 than H2S gas. In general, there was a high likelihood of improving the performance of UASB reactor operating at psychrophilic temperature by optimizing operational parameters.

C/C soft-hard mixed preform multi-units compression compaction viscoelastic rebound technique and optimization

To address the issue of non-uniform fiber volume fraction between layers in the compression compaction process of C/C soft-hard mixed preforms, a multi-unit variable duration cyclic compression compaction process based on the inter-laminar fiber compression viscoelastic deformation behavior is proposed. This process aims to gradually eliminate the rebound characteristics of inter-laminar fibers and reduce the error of inter-laminar fiber volume fraction. The mapping relationships between the number of units, holding duration, and compaction times with the rebound height of inter-laminar fibers are established using data fitting. The compression compaction process is determined using the Box Behnken response surface design method, and digital devices are utilized for preform compaction experiments. The micro-morphology of the preform is observed using an optical microscope, and the density of inter-laminar fibers before and after process optimization is compared. Experimental results indicate that when the number of units is 3, the holding duration is 57 s, and the compaction times is 2, the fiber volume fraction of the soft-hard mixed preform is 42.90%, which is 12.16% higher than before process optimization, and the error of inter-laminar fiber volume fraction is less than 6.5%.

Effects of nanoparticles on mechanical and microstructural properties of cement composite pastes at high temperature and high pressure

This study aims to investigate the effects of nanoalumina (nano-Al2O3, NA) and nanotitanium dioxide (nano-TiO2, NT) particles on the mechanical and microstructural properties of oil well cement composite pastes. Eleven groups of cement composite pastes mixed with NA (0.5–2.5 wt.%), NT (0.5–2.5 wt.%) particles and silica flour were designed by central composite response surface design method (CCD method). Meanwhile, a reference group (SF-OWC) consisting of oil well cement and silica flour was designed. These pastes were cured at 300 °C/13.0 MPa in an autoclave to simulate the downhole condition during the steam injection process in steam injection wells. The compressive strength and Young's modulus of cured cement composite pastes were tested, and mathematical models were developed to evaluating the response of NA and NT particle content on compressive strength and Young's modulus. Moreover, the mineralogy and microstructural evolution of the pastes were investigated using multi-technique methods. The results showed that the compressive strength of the mixed nanoparticles modified SF-OWC composite pastes increased by 7.5%–36.4% compared to the reference group. Moreover, this enhancement is more significant when the incorporated NA or NT particles dominate the mixed nanoparticles. The model prediction results show that adding 2.5 wt.% NA and 0.5 wt.% NT particles or adding 0.5 wt.% NA and 2.5 wt.% NT could increase the compressive strength of cement composite pastes by 58.8% and 37.5%, respectively. The mechanism analysis showed that when the incorporated mixed nanoparticles were mainly NT particles, the improvement of mechanical properties was mainly attributed to the filling effect and nuclear effect of NT particles. When the incorporated mixed nanoparticles were mainly NA particles, more C-(A)-S-H gels were retained and tightly filled and bonded with xonotlite, which made the microstructure of the cement composite pastes more dense, stronger bonding, and more conducive to resistance to load or stress variations.

Production of a new type of cemented paste backfill with solid waste from carbide slag, soda residue, and red mud: mechanism, optimization, and its environmental effects.

To solve the disposal problems of carbide slag (CS), soda residue (SR), and red mud (RM) solid wastes, a new type of cemented paste backfill (CPB) was prepared with CS, SR, and RM solid wastes. The mixing proportion for the CPB was optimized by combining the Box‒Behnken design (BBD) response surface method and the satisfaction function method. The strength formation mechanism for the CPB was analyzed with physical and mechanical property tests, X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), etc. The safety of the CPB was evaluated with heavy metal leaching testing. The results showed that the 28-day unconfined compressive strength (UCS) of CPB first increased and then decreased with increasing CS/RM (0.2 ~ 0.6) and SR/RM (0.2 ~ 0.6); the optimum mixing ratios were CS/RM = 0.45 and SR/RM = 0.37, and the solid mass concentration was 64.75%; dense calcium silicate (aluminum) hydrate (C-S-H/C-A-S-H) bound to the solid particles of red mud and filled pores to provide early strength for the CPB, laminar interwoven Friedel's salt (Fs), ettringite and portlandite hydration products provided late strength for the CPB; and the leaching concentrations of five heavy metals (Fe, Mn, Cu, Zn, and Cr) in the solidified CPB were greatly reduced and far below the leaching limits specified in China's Quality Standard for Groundwater (GB/T 14848-2017).

Efficient degradation of carbamazepine using a modified nickel-foam cathode (Ni-FM/CNTs) in penetrating electro-Fenton process

A modified nickel-foam (Ni-FM) cathode coated with multi-walled carbon nanotubes (Ni-FM/CNTs) was synthesized for carbamazepine (CBZ) highly energy-efficient degradation in penetrating electro-Fenton. Scanning Electron Microscopy (SEM) and X-ray diffractometer (XRD) test proves that multi-walled CNTs were successfully coated on the surface of nickel foam. The linear sweep voltammetry (LSV) results revealed the greater electrochemical activity of Ni-FM/CNTs compared to Ni-FM. The H2O2 accumulation performance tests showed that Ni-FM/CNTs cathode had higher H2O2 accumulation performance than Ni-FM cathode, and the H2O2 yield of Ni-FM/CNTs was 5.7 times higher than that of Ni-FM after 1 h of electrolysis. The reaction rate of CBZ degradation in penetrating electro-Fenton process was 2.5 times that of planar electro-Fenton process because the flow-through process enhanced O2 mass transfer and promoted the production of H2O2. The Box-Behnken Design response surface method was used to analyze the factors affecting the degradation efficiency of CBZ in the penetrating electro-Fenton process. The CBZ degradation efficiency could reach 100%, and electric energy consumption was 0.4356 Wh/L at current density of 9 mA/cm2, pH = 3, concentration of Fe2+ was 0.3 mM, and the through-flow velocity of 60 mL/min. The quenching experiment and EPR test results confirmed the degradation of CBZ was mainly the oxidation of·OH, and O2-·is the prerequisite for the production of·OH. Eight possible degradation products of CBZ degradation were identified and the probable degradation route was proposed. The ECOSAR program was used to predict the toxicities of CBZ and its degradation products, and the consequences revealed that the electro-Fenton process has a detoxification effect on CBZ, but may also produce more toxic organic compounds than the parent compound.

Triptolide nanoemulsion gel as a transdermal drug delivery system: preparation, pharmacokinetics, and rheumatoid arthritis evaluation.

This study aimed to develop and evaluate triptolide nanoemulsion gels (TP-NE gels) as a transdermal drug delivery system. TP-NE was prepared and optimized via emulsification and the central composite design response surface method. The optimized TP-NE gel was evaluated in vitro and in vivo. TP-NE gel microstructure, in vitro and in vivo pharmacokinetics, and anti-rheumatoid arthritis effects were studied to evaluate the feasibility of its percutaneous administration. The Optimized TP-NE was observed using a Malvern Autosizer Nano ZS 90 inspection system and a transmission electron microscope (TEM). The nanoemulsion had an average size of 162.9 ± 0.281 nm, a polydispersity index of 0.272 ± 0.024, a zeta potential of -30.03 ± 2.01 mV, and mostly spherical and uniform morphology. In addition, the TP-NE gel pharmacokinetics, assessed via a skin-blood two-site synchronous microdialysis, revealed that TP was higher in the skin than in the blood. TP-NE gel is crucial in reducing knee edema, inhibiting inflammation, and treating rheumatoid arthritis by regulating tumor necrosis factor-alpha, interleukin-1β, and -6 levels. The TP-NE gel is a promising local delivery method for rheumatoid arthritis (RA)-associated edema and inflammation and can serve as a prospective platform for percutaneous TP administration.

Investigation of Physico-Mechanical Properties and Multi-Objective Optimization of Industrial Ceramic Tiles Using Response Surface Method: Sintering Temperature and Time

Firing process, which is highly difficult part to control, is the most important step in the ceramic manufacturing process. In this study, manufacturing technology and statistical methods were used together to produce low-cost and high-quality products at the optimum sintering temperature and sintering time. Physio-mechanical properties of ceramic tiles manufactured on the industrial scale were optimized using Central Composite Design of Response Surface Method. The regression coefficients of the obtained models (R 2) were evaluated according to the variance analysis (95% confidence level) results and determined as 97.70% for flexural strength, 98.50% for water absorption, and 97.90% for fired shrinkage. The standard deviation of flexural strength, water absorption, and firing shrinkage values, calculated according to the theoretical results, were 1.397%, 0.00265% and 0.0255%, respectively. The samples with desired physical properties were obtained with the developed models by examining the interactions of variables at the industrial conditions.

Structural optimization of melting process of a latent heat energy storage unit and application of flip mechanism

Thermal energy storage technology is of great significance for the efficient utilization of solar energy. In this paper, the melting process of a horizontal latent heat energy storage unit is studied by numerical method. Taguchi design method and response surface method are exploited to optimize its melting performance. The effects of inner tube eccentricity, fin deflection angle, and fin width upon the melting performance are investigated. The contribution of each parameter to the melting performance is processed by Taguchi method, and the interactions of each parameter are obtained by response surface method. The fluid-structure coupling equation of target response is fitted to obtain the optimal structure, and the influence of different structural parameters on the melting performance is discussed. The results reveal that compared with the initial structure, the melting time of the optimal structure is reduced by 64.16% and the average heat absorption rate is increased by 168.38%, respectively. It is evaluated that the structure optimization greatly increases the heat absorption rate and reduces the melting time, but it has a negative effect on the heat absorption in one melting cycle. Finally, the single flip mechanism is introduced innovatively, and the influence of flip time on the related melting properties is discussed. The single flip is the best to increase the average thermal energy absorption rate by 6.30% and reduce the melting time of the unit by 10.57%.

Effects of Tillage Depth and Tractor Speed on Implement Speed for Three Tillage Implements on a Clay Loam Soil

The utilization of agricultural machinery represents the main aspect contributing to the total energy input in the agricultural system. The trials were achieved using five tractor speeds(3.6, 5.4, 7.2, 9.0 and 10.8 km/hr) and five tillage depths(10, 15, 20, 25 and 30 cm) to determine implement speed at different tillage depths for 3-bottom disc plough, spring tine cultivator and offset disc harrow on a clay loam soil. The design of the experiment used were two factors, five levels factorial of Central Composite Rotatable Design of Response Surface Method. The implement speed for 3-bottom disc plough, spring tine cultivator and offset disc harrow ranged from 0.78 to 1.95, 0.67 to 2.19 and 0.70 to 2.11 m/s, respectively. The effects of tillage depths and tractor speeds on implement speed for the three tillage implements were assessed. The results indicated that increasing the tillage depth decreased the implement speed for all the tested implements but increasing the tractor speed increased the implement speed. The tractor speed had more pronounced effect on the implement speed than the tillage depth. This study therefore recommends that the availability of time and implement width should be used in determining the speed required to finish the work on time.

Study on the mechanism of catalytic fast co-pyrolysis of biomass and coal tar asphaltenes: Gas-liquid-solid products' optimization

It is very important to evaluate how coal tar asphaltenes (CTA) and corn cob (CB) could be used comprehensively in order to achieve zero waste. Catalytic co-pyrolysis is a feasible method to reduce CO2 emissions, realizing the development and utilization of biomass energy, and the recycling of asphaltenes. In this study, the catalytic effect of K on co-pyrolysis was more obvious than that of Ca, Co, Ni, Cu and Zn based on the analysis of TG/DTG, FTIR and Py-GC/MS. The response surface design method and artificial neural network were introduced to comprehensively investigate the effects of mixing ratios, metal loads and heating rates on the catalytic co-pyrolysis. The results showed that K-catalysis co-pyrolysis effectively improved the yield of gas and char, and increased the content of phenolics. In particular, when the load of K was 5.3 wt%, the heating rate was 476 °C/min, and the proportion of CB was 38 wt%, the maximum solid yield was 35.16 wt%, and the solid product had good catalytic ability. Based on the above analysis, the mechanism of K-catalysis co-pyrolysis was proposed.

Optimization of technological parameters in ultrasonic welding of the polypropylene fabric using Taguchi and FCCCD methods

Ultrasonic welding is a welding method that has been applied for welding nonwoven fabrics, with many advantages such as fast speed, high reliability, easy automation and especially less pollution to the environment. This paper studies the optimization of technological parameters in the welding process such as welding time, pressure, and weld shape on the breaking strength of ultrasonic welding of Polypropylene (PP) nonwovens. To evaluate the influence level and find the reasonable technological parameters domain in the paper, the Taguchi method is used in combination with the face-centered central composite design (FCCCD) response surface method. The research results have determined the regression equations used to calculate the breaking strength for each weld shape as well as the optimal domain for the main technological parameters, ensuring the breaking strength of the weld. There are different degrees of influence of technological parameters (shape of the weld zone, welding time and welding pressure) on the breaking strength of ultrasonic welds. Among them, the influence level of welding time t is 45.31 %, the weld shape is Pattern 2 with the rate of 30.03 %, and the welding pressure is 24.66 %. Carrying out a verification test with the welding parameters: t=1.6 s, p=3.1 kgf/cm2, two patterns ( Pattern 2 and Pattern 3), the result of breaking strength for patterns was achieved. Pattern 2 has a difference of 1.19 % between the regression equation results and the actual experimental results, while the figure for Pattern 3 is 0.77 %. From these results, it is possible to select the appropriate technological parameters for ultrasonic welding equipment when processing products from nonwoven fabrics to ensure the highest quality and productivity

Catalytic co-pyrolysis of cellulose over alkali and alkaline earth metal salts for levoglucosan production

A comprehensive study of alkali and alkaline earth metal (AAEM) salts including two different anions (Cl- and CH3COO-) in the catalytic pyrolysis of cellulose to produce levoglucosan (LG), bio-oil, and biochar were investigated. At the same time, the catalytic pyrolysis mechanism was also speculated. The thermogravimetric analyzer (TGA) and lab-scale fixed-bed reactor system were used to determine the thermal degradation process and the pyrolysis products of LG, bio-oil, and biochar. The optimized pyrolysis parameters were obtained by using Box-Behnken design-response surface method. According to the results, AAEM salts significantly boosted the yield of biochar, as well as greatly cut down the output of LG and bio-oil. The rank of effect on LG yield was as follows: CaCl2, MgCl2 > CH3COOK, CH3COONa > (CH3COO)2Mg, (CH3COO)2Ca > KCl, NaCl. Moreover, the addition of AAEM salts considerably dropped the activation energy E of cellulose pyrolysis as well as prompted microcrystalline cellulose pyrolysis under lower temperatures. This study was pivotal in deducing the pathway of cellulose pyrolysis, thereby offering critical insights to hasten the progress of biomass utilization.

Preparation of inorganic binder-stabilised material with iron tailings: strength formation and gradation optimisation

This study focuses on mechanical strength and gradation optimisation of inorganic binder-stabilised material with iron tailings for pavement engineering. The mechanical strength and compatibility of iron tailings mortar with various inorganic binders were explored. Mechanical strength formation of iron tailings mortar was analysed using hydration products, micromorphology and microstructures. Composition optimisation of inorganic binder-stabilised material with iron tailings was discussed using the central composite design-response surface method. Results showed that the mechanical strength formation of iron tailings mortar is primarily dependent on ettringite and calcium silicate hydrate (C–S–H) gels. Iron tailings mortars with an appropriate amount of lime or fly ash replacement of cement exhibit a denser structure and adequate pore structure distribution that help improve their mechanical properties compared with cement iron tailings mortars. To balance the amount of iron tailings and the strength of cement-stabilised material, optimal application conditions were proposed for different levels of highways.

Vitexin loaded mixed polymeric micelles: preparation, optimization, evaluation and anti-osteoporotic effect

In this regard, we developed vitexin (Vi)-loaded D-ɑ-tocopherol polyethylene glycol succinate, polyvinylpyrrolidone K30 and sodium cholate mixed micelles (Vi-MMs) mainly for improving oral bioavailability and enhancing anti-osteoporotic effect of Vi. Thin layer dispersion method was employed to prepare Vi-MMs, and then the optimal prescription was optimized by the orthogonal design-response surface method, wherein encapsulation efficiency (EE) was used as optimizing index. The physical properties of Vi-MMs such as appearance morphology, particle size, and zeta potential were also characterized. We further analyzed the in-vitro release of Vi and Vi-MMs in three media and investigated the pharmacokinetics of Vi and Vi-MMs in rats. Anti-osteoporotic activity of Vi and Vi-MMs was assessed by establishing a zebrafish osteoporosis model with prednisone. Drug loading, EE, particle size and zeta potential of the optimized Vi-MMs were 8.58 ± 0.13%, 93.86 ± 1.79%, 20.41 ± 0.64 nm and −10 ± 0.56 mV, respectively. The optimized Vi-MMs were shaped spherically as exhibited by transmission electron microscopic technique, with evident core shell nano-structure, well dispersed. In all three media, the release rate of Vi-MMs was significantly higher than that of free Vi. The oral bioavailability of Vi-MMs was increased by 5.6-fold compared to free Vi. In addition, alleviation of prednisone induced osteoporosis in zebrafish by Vi-MMs further demonstrated good anti-osteoporotic effect. In summary, Vi-MMs exhibited enhanced bioavailability and anti-osteoporotic effect, which is expected to be potential nanocarrier for Vi applications in drug development.

Optimization of the QuEChERS extraction method to determine Polycyclic Aromatic Hydrocarbons (PAHs) in powder aerosol particles collected by cyclone

Conventional methods for collecting and extracting aerosol particles are challenging in accurately characterizing particle-bound polycyclic aromatic hydrocarbons (PAHs) contamination and conducting cellular exposure studies. Therefore, developing direct aerosol sample collection and simple pretreatment analytical methods is necessary. This study describes the optimization of the QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction method for the determination of PAHs in powder-form environmental standard materials (SRM1944) and proves it is also effective for analyzing PAHs in powder aerosol particle samples collected by cyclone. In this study, we used an I-optimal design response surface method combined with a desirability function to investigate the extraction effect of PAHs under different combinations of QuEChERS extraction factors, including extraction solvent, salt, and clean-up reagent. The optimized conditions of the method were determined using the 2-factor interaction (2FI) model combined with boundary conditions, resulting in acetonitrile/dichloromethane (7:1, v/v), Na2SO4/NaCl (1:1, w/w), and primary and secondary amine (PSA) as extraction solvents, extraction salts, and clean-up reagent, respectively. The optimized method showed good recoveries of PAHs reaching 76%–118% and 85%–121% for SRM1944 and standard solution. The results for cyclone-collected ambient powder aerosol particles extracted by the optimized QuEChERS illustrated that this improved procedure has good PAHs extraction efficiency as the traditional Soxhlet method, while reducing hazardous organic solvents usage, experimental cost (per mg sample) by 97% and sample pretreatment time. Overall, this combination of “powder aerosol particle collection and modified QuEChERS extraction” provides new insight on aerosol sample collection, extraction, and in vitro/in vivo exposure studies.

Experimental Investigation On Machining Performance of Ti6Al4V On Electro Discharge Machining Using Stationary and Rotary Electrode

Titanium alloys are commonly used in different industries due to its high strength and less in weight. Even though the machinability of titanium alloys is very less, due to its high strength, it becomes more useful in aerospace and medical industries. In this paper, the performance of stationary and rotary copper electrodes on machining of Titanium alloy Ti-6Al-4V with Electro Discharge Machining (EDM) have been studied. Material removal rate (MRR), tool ware rate (TWR) and surface roughness (SR) were analyzed with three controllable input parameters such as pulse on time (Ton), Peak Current (Ip) and Gap Voltage (V). The design of experiment is chosen for the experimentation as the Box-Behnken response surface design method. The results are analyzed using grey relational analysis (GRA) coupled with firefly algorithm. In both the case of stationary and rotary electrode, it was revealed that gap voltage is significant for overall grey relational grade. The machining performance of Titanium alloy Ti-6Al-4V in the case of rotary mode of electrode is quite better as compared to the stationary mode of operation.

Optimization of uranium bioreduction by shewanella RCRI7 using Response Surface Design Method (RSM) in industrial waste

تمام ترکیبات اورانیم، سمی و رادیواکتیو هستند. سمی بودن این عنصر می‌تواند کشنده باشد. با توجه به سمیت شیمیایی و رادیواکتیویته اورانیم، ضروری است از ورود آن به طبیعت جلوگیری شود. پسماندهای خروجی از مراکز صنعتی- هسته­ای نیز دارای مقادیر مختلفی از اورانیم می­باشد و لذا حذف این عنصر از پساب این مراکز از اهمیت ویژه­ای برخوردار است. از سویی دیگر، نظر به اهمیت این عنصر و محدودیت منابع آن، بازیابی اورانیم از پسماندها، دارای ارزش اقتصادی نیز می­باشد. در پژوهش حاضر، از روش سطح پاسخ (RSM) بر اساس طرح مرکب مرکزی به منظور بررسی و بهینه­سازی پارامترهای مختلف بر فرایند احیای اورانیم توسط باکتری 7Shewanella RCRI در پساب واقعی استفاده گردید. معادله­ی درجه دوم پیشنهاد شده با ضریب همبستگی 94/0=2R از کفایت مناسبی برخوردار بوده و حداکثر راندمان احیای اورانیم توسط 7Shewanella RCRI در شرایط بهینه (pH=5/6-7/5، دمای 63/26 درجه سانتی­گراد و زمان 117 ساعت)، 98% براورد شده است. در گام بعدی به منظور تعامل بین متغیرها، رویه­های سه­بعدی با تقابل pH و دما; دما و زمان;pH و زمان به دست آمده و در پایان بر اساس بهینه­های پیشنهادی احیای اورانیم در پساب واقعی توسط دو روش XRD و اسپکتروفتومتری مورد بررسی قرار گرفته است. بر اساس نتایج به­دست آمده، باکتری 7Shewanella RCRI می­تواند، به عنوان باکتری با ارزش در احیای زیستی اورانیم از پساب خروجی مراکز صنعتی معرفی گردد. از سوی دیگر استفاده از روش سطح پاسخ می‌توانند درک جامعی از فرایند و مکانیسم احیای زیستی اورانیم توسط باکتری 7Shewanella RCRI و پشتیبانی نظری برای انجام این فرایند ارایه دهد.