scholarly journals Optimization of Bi2O3, TiO2, and Sb2O3Doped ZnO-Based Low-Voltage Varistor Ceramic to Maximize Nonlinear Electrical Properties

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Masoumeh Dorraj ◽  
Azmi Zakaria ◽  
Yadollah Abdollahi ◽  
Mansor Hashim ◽  
Seyedehmaryam Moosavi
Keyword(s):  
Low Voltage ◽  
Quadratic Model ◽  
Molar Ratio ◽  
Sintering Process ◽  
Spinel Type ◽  
Factors Affecting ◽  
Milling Method ◽  
Level 3 ◽  
Central Composite ◽  
Good Agreement

In ZnO-based low voltage varistor, the two essential features of microstructure determining its nonlinear response are the formation Bi-enriched active grain boundaries as well as a controlled ZnO grain size by secondary spinel-type phases. Besides, the microstructure and phase composition are strongly affected by the dopant concentration during sintering process. In this study, the optimal dopant levels of Bi2O3, TiO2, and Sb2O3to achieve maximized nonlinear electrical property (alpha) were quantified by the response surface methodology (RSM). RSM was also used to understand the significance and interaction of the factors affecting the response. Variables were determined as the molar ratio of Bi2O3, TiO2, and Sb2O3. The alpha was chosen as response in the study. The 5-level-3-factor central composite design, with 20 runs, was used to conduct the experiments by ball milling method. A quadratic model was established as a functional relationship between three independent variables and alpha. According to the results, the optimum values of Bi2O3, TiO2, and Sb2O3were obtained 0.52, 0.50, and 0.30, respectively. Under optimal conditions the predicted alpha (9.47) was calculated using optimal coded values from the model and the theoretical value is in good agreement with the value (9.43) obtained by confirmation experiment.

scholarly journals Optimization of sorting efficiency of size grading machine using oscillating sieve with swing along width direction

2019 ◽  
Vol 293 ◽  
pp. 04003
Author(s):  
Thatchapol Chungcharoen ◽  
Warunee Limmun ◽  
Watcharapong Chanpaka ◽  
Naruebodee Srisang
Keyword(s):  
Quadratic Model ◽  
Optimum Operating ◽  
Coffee Bean ◽  
Width Direction ◽  
Sorting Efficiency ◽  
Inclined Angle ◽  
Green Coffee Bean ◽  
Central Composite ◽  
Size Grading ◽  
Good Agreement

Grading according to the sizes is an important value adding technique for Robusta green coffee bean. Mechanical grading can increase the sorting efficiency and the need for workers is decreased. Therefore, the sorting efficiency of size grading machine was optimized based on inclined angle and oscillating speed. The Response Surface Methodology (RSM) combined with central composite design (CCD) was applied in the optimization of the sorting efficiency of the machine. A quadratic model was suggested for the sorting efficiency of size grading machine. The results showed that the optimum operating parameters for size grading machine using oscillating sieve with swing along width direction were inclined angle of 5.06 degree and oscillating speed of 183.28 rpm with a sorting efficiency of 79.99%. The high correlation coefficient (R2 = 0.9676) indicated that the data predicted using RSM were in good agreement with the experimental results.

scholarly journals Optimization of Conversion of High Free Fatty Acid Jatropha curcas Oil to Biodiesel Using Response Surface Methodology

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Prerna Goyal ◽  
M. P. Sharma ◽  
Siddharth Jain
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Jatropha Curcas ◽  
Methyl Esters ◽  
Polynomial Equation ◽  
Molar Ratio ◽  
Optimum Level ◽  
Acid Catalyzed ◽  
Central Composite ◽  
Good Agreement

A five-level-four-factor central composite design (CCD) with 54 assays was employed to study the effect of catalyst concentration (NaOH), reaction temperature, reaction time, and methanol/oil molar ratio on the methyl esters yield from Jatropha curcas oil (JCO) during its transesterification. Using response surface methodology (RSM), a quadratic polynomial equation was obtained for Jatropha curcas biodiesel (JCB) yield by regression analysis. Verification experiments confirmed the validity of the predicted model. The high free fatty acids (FFAs) (14.6%) of JCO could be reduced to 0.34% by acid-catalyzed esterification and a JCB yield of 98.3% was obtained with methanol/oil ratio (11 : 1) using NaOH as catalyst (1% w/w) in 110 min time at 55°C temperature. The predicted value of JCB yield is found to be in good agreement with the experimental value at the optimum level of input parameters. The properties of the biodiesel, thus, produced conform to the ASTM and IS specifications, making it an ideal alternative fuel for diesel engines. The model can be effectively used in oil industry to maximize the biodiesel yield from given oil.

scholarly journals Adaptive Shell Spherical Reflector Actuated with PVDF-TrFE Thin Film Strain Actuators

Actuators ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 7
Author(s):  
Kainan Wang ◽  
Thomas Godfroid ◽  
Damien Robert ◽  
André Preumont
Keyword(s):  
Thin Film ◽  
Active Material ◽  
Quadratic Model ◽  
Influence Functions ◽  
Regularization Technique ◽  
Thin Polymer ◽  
Optical Modes ◽  
Electrostrictive Material ◽  
Ill Conditioning ◽  
Good Agreement

This paper discusses the design and manufacturing of a thin polymer spherical adaptive reflector of diameter D=200 mm, controlled by an array of 25 independent electrodes arranged in a keystone configuration actuating a thin film of PVDF-TrFE in d31-mode. The 5 μm layer of electrostrictive material is spray-coated. The results of the present study confirm that the active material can be modelled by a unidirectional quadratic model and that excellent properties can be achieved if the material is properly annealed. The experimental influence functions of the control electrodes are determined by a quasi-static harmonic technique; they are in good agreement with the numerical simulations and their better circular symmetry indicates a clear improvement in the manufacturing process, as compared to a previous study. The low order optical modes can be reconstructed by combining the 25 influence functions; a regularization technique is used to alleviate the ill-conditioning of the Jacobian and allow to approximate the optical modes with reasonable voltages.

Kinetics and Equilibrium of Radioactive Metal Adsorption onto Sugarcane Bagasse Waste: Comparison of Batch and Column Adsorption Modes

2021 ◽  
Vol 235 (3) ◽  
pp. 281-294
Author(s):  
Abida Kausar ◽  
Haq Nawaz Bhatti ◽  
Munawar Iqbal
Keyword(s):  
Sugarcane Bagasse ◽  
Flow Rate ◽  
Breakthrough Curves ◽  
Quadratic Model ◽  
Waste Biomass ◽  
Initial Concentration ◽  
Bed Height ◽  
Column Adsorption ◽  
Central Composite ◽  
Bagasse Waste

Abstract Sugarcane bagasse waste biomass (SBWB) efficacy for the adsorption of Zr(IV) was investigated in batch and column modes. The process variables i.e. pH 1–4 (A), adsorbent dosage 0.0–0.3 g (B), and Zr(IV) ions initial concentration 25–200 mg/L (C) were studied. The experiments were run under central composite design (CCD) and data was analysed by response surface methodology (RSM) methodology. The factor A, B, C, AB interaction and square factor A2, C2 affected the Zr(IV) ions adsorption onto SBWB. The quadratic model fitted well to the adsorption data with high R2 values. The effect of bed height, flow rate and Zr(IV) ions initial concentration was also studied for column mode adsorption and efficiency was evaluated by breakthrough curves as well as Bed Depth Service and Thomas models. Bed height and Zr(IV) ions initial concentration enhanced the adsorption of capacity of Zr(IV) ions, whereas flow rate reduced the column efficiency.

scholarly journals Optimization of Supercritical Extraction Conditions of Senna Alata and Evaluation of Biological Activity

2018 ◽  
Vol 7 (3.11) ◽  
pp. 94
Author(s):  
Istikamah Subuki ◽  
Aiman Nabilah Abdul Malek ◽  
Saidatul Husni Saidin ◽  
Mazura Md. Pisar
Keyword(s):  
Crude Extract ◽  
Extraction Process ◽  
Quadratic Model ◽  
Total Flavonoids ◽  
Inhibition Activity ◽  
Backward Elimination ◽  
Total Flavonoids Content ◽  
Senna Alata ◽  
Central Composite ◽  
Experimental Runs

Supercritical fluid extraction (SFE) offer faster extraction process, decreased solvent usage and more selectivity on desired compounds. In this present study, the influence of pressure (100, 200 and 300 bar) and temperature (40, 50 and 60˚C) on the Senna alata crude yield were investigated with fixed supercritical carbon dioxide (SC-CO2) at the flow rate of 35 g/min. The parameters were optimised and modelled using response surface methodology (RSM) and central composite design (CCD). The analysis of variance (ANOVA) experimental design consists of 13 experimental runs with 5 replicates at the central points. Well-fitting quadratic model were successfully established for crude extract through backward elimination. The optimum crude extract yield pointed out by RSM was at the pressure of 300 bar and temperature 40˚C respectively. Extraction yields based on SC-CO2 varied in the range of 0.28 to 3.62%. The highest hyaluronidase inhibition activity and total flavonoids content obtained by S.alata crude extracts were 41.19% and 52.53% w/w, respectively. SC-CO2 proves to have great potential for extraction of yield, hyaluronidase inhibition activity and total flavonoids content for S.alata.  

Deceleration of sliding motorcycles (mainly scooters) in accident reconstructions

2017 ◽  
Vol 232 (7) ◽  
pp. 866-876 ◽  
Author(s):  
Carlo Cialdai ◽  
Dario Vangi ◽  
Antonio Virga
Keyword(s):  
Urban Areas ◽  
Test Session ◽  
Road Accidents ◽  
Factors Affecting ◽  
Different Types ◽  
Energy Dissipated ◽  
Comparison Of The Results ◽  
Two Wheeler ◽  
The Impact ◽  
Good Agreement

This paper presents an analysis of the situation in which a two-wheeler (i.e. a motorcycle, where the term motorcycles includes scooters) falls over to the side and then successively slides; this typically occurs in road accidents involving this type of vehicle. Knowing the deceleration rate of the sliding phase allows the kinetic energy dissipated and the speed of the motorcycle just before the fall to the ground to be calculated. These parameters are very important in the analysis and reconstruction of accidents. The work presented in this paper was developed in two experimental test sessions on fully faired motorcycles which are mainly of the scooter type and widely used in urban areas. In the first session, sliding tests were carried out, with the speed in the range 10–50 km/h, on three different types of road surface. Analysis of the evidence allowed the dissipative main phases of motion of the motorcycle (the impact with the ground, the rebounds and the stabilized swiping) to be identified and some factors affecting the phenomenon to be studied. The coefficient of average deceleration was calculated using two typical equations. The second test session consisted of drag tests. In these tests, the motorcycle, which had previously laid on its side, was dragged for a few metres at a constant speed of about 20 km/h, while the drag force was measured. A comparison of the results obtained in these tests with those obtained in the sliding tests yielded very good agreement in the coefficients of deceleration.

scholarly journals Long-Term Changes in Solar Shortwave Irradiance Due to Different Atmospheric Factors According to Measurements and Reconstruction Model in Northern Eurasia

2020 ◽  
Vol 4 (1) ◽  
pp. 5
Author(s):  
Elena Volpert ◽  
Natalia Chubarova
Keyword(s):  
Optical Thickness ◽  
Cloud Amount ◽  
Shortwave Radiation ◽  
Northern Eurasia ◽  
Factors Affecting ◽  
Meteorological Observatory ◽  
Cloud Optical Thickness ◽  
Reconstruction Model ◽  
Good Agreement

The temporal variability of solar shortwave radiation (SSR) has been assessed over northern Eurasia (40°–80° N; 10° W–180° E) by using an SSR reconstruction model since the middle of the 20th century. The reconstruction model estimates the year-to-year SSR variability as a sum of variations in SSR due to changes in aerosol, effective cloud amount and cloud optical thickness, which are the most effective factors affecting SSR. The retrievals of year-to-year SSR variations according to different factors were tested against long-term measurements in the Moscow State University Meteorological Observatory from 1968–2016. The reconstructed changes show a good agreement with measurements with determination factor R2 = 0.8. The analysis of SSR trends since 1979 has detected a significant growth of 2.5% per decade, which may be explained by its increase due to the change in cloud amount (+2.4% per decade) and aerosol optical thickness (+0.4% per decade). The trend due to cloud optical thickness was statistically insignificant. Using the SSR reconstruction model, we obtained the long-term SSR variability due to different factors for the territory of northern Eurasia. The increasing SSR trends have been detected on most sites since 1979. The long-term SSR variability over northern Eurasia is effectively explained by changes in cloud amount and, in addition, by changes in aerosol loading over the polluted regions. The retrievals of the SSR variations showed a good agreement with the changes in global radiance measurements from the World Radiation Data Center (WRDC) archive. The work was supported by RFBR grant number 18-05-00700.

scholarly journals Faktor-Faktor yang Mempengaruhi Produksi Biodiesel dari Minyak Sawit Mentah Menggunakan Katalis Padat Kalsium Karbonat yang Dipijarkan

2012 ◽  
Vol 11 (2) ◽  
pp. 129 ◽  
Author(s):  
Amir Awaluddin ◽  
Saryono ' ◽  
Sri Nelvia ◽  
Wahyuni '
Keyword(s):  
Methyl Esters ◽  
National Standard ◽  
Molar Ratio ◽  
High Price ◽  
Homogeneous Catalyst ◽  
World Population ◽  
Crude Palm Oil ◽  
Factors Affecting ◽  
Acid Catalyzed ◽  
Edible Type

The demand for petroleum has increased recently due to the increase of world population, industries andtransportation. Biodiesel (fatty acids methyl esters) has become attractive because of high price of petroleum,limited recourses of crude oil, and environmental concerns. Most biodiesel is produced by transesterification oftriglycerides of refined/edible type oils using methanol and homogeneous catalyst such NaOH and KOH. The useof heterogeneous calcined CaCO3 catalyst, has advantages such as the ease of phase separation betweencatalyst and biodiesel. This paper presents factors affecting the synthesis of biodiesel from crude palm using thecalcined CaCO3 catalyst . The synthesis is carried out by two steps, the acid-catalyzed pre-esterification of free-fatty acid and followed by base-catalyzed transesterification of triglycerides. A study of optimizing the reactioncondition of the esterification followed by transesterification of crude palm oil (CPO) is performed to obtainmaximum production of biodiesel. Under conditions of catalyst calcination temperature of 9000C, reactor time of1.5 hours, catalyst dosage of 1,5%, reaction temperature of 700C and methanol/oil molar ratio of 9 : 1, the oilconversion is 74,6%. The as-synthesized biodiesel meets the requirements of Indonesian National Standard (SNI)for biodiesel.

scholarly journals Luminosity variation in the extended one-zone RR Lyrae model

2005 ◽  
pp. 57-64
Author(s):  
D. Pricopi
Keyword(s):  
Ideal Gas ◽  
Stellar Model ◽  
Nonlinear Analyses ◽  
Uniform Rotation ◽  
Factors Affecting ◽  
Pulsating Stars ◽  
Rr Lyrae ◽  
Stellar Pulsation ◽  
Pulsation Model ◽  
Good Agreement

The Stellingwerf one-zone stellar model is extended by assuming, a slow and uniform rotation that leads to a very small oblateness of the star. The matter in the core-surrounding shell is supposed to consists of a mixture of ideal gas and radiation. This one-zone stellar pulsation model is proposed as a tool to investigate the factors affecting luminosity variations of pulsating stars. Linear and nonlinear analyses of the resulting equations are described. The results are in very good agreement with the observed RR Lyrae light curves. .

scholarly journals Fatigue Performance of Thin Laser Butt Welds in HSLA Steel

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1499
Author(s):  
Patricio G. Riofrío ◽  
Fernando Antunes ◽  
José Ferreira ◽  
António Castanhola Batista ◽  
Carlos Capela
Keyword(s):  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Hsla Steel ◽  
High Strength ◽  
Butt Joints ◽  
Factors Affecting ◽  
Weld Profile ◽  
The Relationship ◽  
Good Agreement ◽  
Significant Factors

This work is focused on understanding the significant factors affecting the fatigue strength of laser-welded butt joints in thin high-strength low-alloy (HSLA) steel. The effects of the weld profile, imperfections, hardness, and residual stresses were considered to explain the results found in the S-N curves of four welded series. The results showed acceptable fatigue strength although the welded series presented multiple-imperfections. The analysis of fatigue behavior at low stress levels through the stress-concentrating effect explained the influence of each factor on the S-N curves of the welded series. The fatigue limits of the welded series predicted through the stress-concentrating effect and by the relationship proposed by Murakami showed good agreement with the experimental results.

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