Central Composite Design Method Research Articles

A Heterogeneous Phosphomolybdate Nanocatalyst Utilizes Vitamin B1 to Promote Solvent‐Free H2O2 Sulfoxidation Selectivity

ABSTRACTCatalyst design and fabrication with safe and affordable components and methods is a high‐value‐added business. In this work, a vitamin‐based hybrid nanomaterial (PMoB1) is prepared by simple stirring of thiamine hydrochloride (vitamin B1, VB1) as an inexpensive commercially available biologically active compound with phosphomolybdic acid (PMo12) in acidic aqueous solution to catalyze selective oxidation of sulfides using aqueous H2O2. A small amount of this heterogeneous catalyst drives rapidly the sulfoxidation reaction under mild and solvent‐free conditions facilitating the product separation and reducing significantly the environmental impacts. The main factors of the catalytic reaction were optimized by the central composite design (CCD) method. The solid catalyst tolerates a wide range of pH and retained its structural integrity even at alkaline solution (pH = 11). PMoB1 composed of two VB1 and one PMo12 was found to be partially reduced based on 13P NMR and UV–Vis spectra. An amorphous structure with aggregated nanoparticles with sizes ranging between 50 and 70 nm and a specific surface area of 35 m2/g are important reasons for enhanced catalytic activity and selectivity. Nevertheless, non‐covalent interactions such as hydrogen bonding and the π–π stacking can also significantly affect the catalyst performance. Given the scavenging tests and spectral evidences, a non‐radical mechanism involving peroxo species is postulated. The catalysis is shown to be truly heterogeneous while the solid catalyst largely maintains its structural integrity during the recycling test.

Liquid–liquid extraction of mandelic acid using deep eutectic solvent prepared by mixing choline chloride and ethylene glycol: an optimisation study

ABSTRACT In this study, deep eutectic solvent (DES) was prepared using choline chloride (a hydrogen bond acceptor) and ethylene glycol (a hydrogen bond donor) in different molar ratios for extracting mandelic acid from its aqueous matrix. At first, the experiments were performed with different molar ratios of DES with 0.1 and 1 M concentrations of mandelic acid to screen out the best combination of DES to be used in the optimisation study. A set of 20 runs was obtained using a central composite design method considering acid concentration, DES to aqueous solution volume ratio, ultrasonication time as input variables, and extraction efficiency as a response. The highest extraction efficiency was predicted to be 86.78% at acid concentration = 0.33 M, ultrasonication time = 12.15 min, and aqueous phase/DES volume ratio = 4.68. Further, solvent recovery and back-extraction of acid were performed using a sodium hydroxide solution.

Optimization of Magnetic Biochar Preparation Process, Based on Methylene Blue Adsorption.

The search for low-cost and effective adsorbents for the removal of organic dyes from contaminated water is urgently needed. The substantial amount of waste mushroom cultivation substrates generated in practical production can serve as an ideal material for the preparation of adsorbents. In this study, we investigated the main control parameters affecting the performance of magnetic mushroom substrate biochar and optimized the process of preparing biochar by using the Plackett-Burman and central composite design methods. Various analytical techniques including SEM, EDX, BET, and VSM were used to characterize the biochar. The results indicate that the carbonization temperature had the most significant impact on the yield and adsorption performance of biochar. Under the conditions of a carbonization temperature of 600 °C, a carbonization retention time of 1 h, and an impregnation ratio of 0.1, the yield and methylene blue adsorption value of magnetic biochar were 42.54% and 2297.04 μg/g, respectively, with a specific surface area of 37.17 m2/g. This biochar effectively removed methylene blue from the solution, demonstrating a high economic efficiency for wastewater treatment and pollution control. Furthermore, the adsorption-desorption cycle studies revealed its excellent stability and reusability. Additionally, based on the response surface methodology, a three-dimensional surface model of the adsorption performance of magnetic biochar under different carbonization conditions was established, providing a theoretical basis for the preparation of magnetic biochar from agricultural wastes.

Preparation and Evaluation of Poloxamer/Carbopol In-Situ Gel Loaded with Quercetin: In-Vitro Drug Release and Cell Viability Study.

Periodontitis is a severe chronic inflammatory disease, whose traditional systemic antimicrobial therapy faces great limitations. In-situ gels provide an effective solution as an emerging local drug delivery system. In this study, the novel thermosensitive poloxamer/carbopol in-situ gels loaded with 20μmol/L quercetin for the treatment of periodontitis were prepared by cold method. Thirteen batches of in-situ gels based on two independent factors (X1: poloxamer 407 and X2: carbopol 934P) were designed and optimized by the statistical method of central composite design (CCD). The transparency, pH, injectability, viscosity, gelation temperature, gelation time, elasticity modulus, degradation rate and in-vitro drug release studies of the batches were evaluated, and the percentage of drug release in the first hour, the time required for 90% drug release, gelation temperature, and gelation time were selected as dependent variables. These two independent factors significantly affected the four dependent variables (p < 0.05). The optimization result displayed that the optimized concentration of poloxamer 407 was 20.84% (w/v), and carbopol 934P was 0.5% (w/v). The optimized formulation showed a clear appearance (++), acceptable injectability (Pass), viscosity(151,798mPas), gelation temperature (36°C), gelation time (213s), preferable cell viability and cell proliferation, conformed to first-order release kinetics, and had a significant antibacterial effect. The article demonstrates the great potential of the quercetin in-situ gel as an effective treatment for periodontitis.

Effect of low-frequency alternating magnetic field on exopolysaccharide production and antioxidant capacity of Pleurotus citrinopileatus by submerged fermentation.

The objective of this study was to investigate the effect of low-frequency alternating magnetic field (LF-AMF) on the production of extracellular polysaccharide (EPS) by submerged fermentation of Pleurotus citrinopileatus. The fermentation conditions optimized by the central composite design method were as follows: fermentation time of 6.18days, temperature of 28.28°C, shaking speed of 149.04 r/min, and inoculum amount of 8.43%. Under these conditions, a LF-AMF was applied to the submerged fermentation of P. citrinopileatus. When the intensity of LF-AMF was 40 Gs, the initial intervention time was 24h after inoculation, and the treatment time was 6h at one time, the mycelial biomass of P. citrinopileatus increased by 11.30%, and the EPS yield increased by 23.09% compared with the fermentation without LF-AMF treatment. The morphology of mycelium after LF-AMF treatment was observed by scanning electron microscopy. It was found that the surface of mycelium was wrinkled, and the structure of mycelium was loose, which might be more conducive to the production of EPS. Mycelium diameter decreased, and ATPase activity increased, indicating that LF-AMF had a positive effect on the production of EPS by P. citrinopileatus fermentation. Moreover, LF-AMF could improve the permeability of the mycelial cell membrane, facilitate the exchange of intracellular and extracellular substances, and increase the metabolic capacity of P. citrinopileatus. In vitro antioxidant test of EPS showed that LF-AMF treatment also improved its antioxidant capacity.

Improved black-winged kite algorithm and finite element analysis for robot parallel gripper design

This paper presents a comprehensive study on the design optimization of a robotic gripper, focusing on both the gripper modeling and the optimization of its parallel mechanism structure. This study integrates the Black-winged Kite Algorithm (BKA), Finite Element Analysis (FEA), Backpropagation Neural Network (BPNN), and response surface optimization techniques. The Good Point Set (GPS), nonlinear convergence factor, and adaptive t-distribution method improve BKA, which enhances exploration and exploitation performance, convergence speed, and solution quality. Subsequently, the parallel mechanism structure is designed to minimize the total mass, total deformation, and maximum equivalent stress. The central composite design (CCD) method was used to design the FEA experiment and establish the BKA-BPNN regression prediction model. The RMSE of this model’s training set and test set are 0.001615 and 0.0029328. A response surface optimization model is constructed to determine the best design solution. The optimized design achieves a 33.12% reduction in maximum equivalent stress, a 1.47% decrease in total mass, and a 0.16% reduction in maximum total deformation. This study provides valuable insights into the design optimization process for robotic grippers, showcasing the effectiveness of the proposed methodologies in enhancing performance while reducing mass and improving structural integrity.

Optimization of municipal solid waste management system in landfill using response surface methodology - a case study of Ogbomoso South Local Government

In this study, Solid waste generation and collection assessment within the study area was undertaken with the view of formulating an optimization model that helped identify the important variables influencing the overall cost of solid waste management and also determine their optimum values. Some of the important variables used in formulating the model include; The number of solid waste collection trips (X1), Number of manpower (Persons) (X2), Fuel consumption per day (X3), Weight of solid waste collection per trip (X4). To determine the model, Statistical design of experiment (DOE) using central composite design method (CCD) was employed. The number of experimental runs based on the CCD method was determined and thirty (30) experimental runs were thereafter generated and optimized. Result of the optimization model revealed that; the number of solid waste collection trips per month (X1 = 47), Number of manpower (persons) (X2 = 3), Fuel consumption per day (X3 = 18.20liters) and Weight of solid waste collection per trip (X4 = 6.33tons). The optimal solution of selected variables produced an overall cost of N162,300. The solution was selected by the Design Expert software with a desirability value of 1 that is 100% reliability.

A comprehensive study on active mixer performance using liquid metal droplets: an experimental approach

In this experimental study, we delve into the performance of an active mixer that utilizes liquid metal droplets. Our mixer configuration follows an innovative Y-type design, where two liquid metal-based pumping mechanisms operate within the minichannel inlet branches. By applying alternating current voltage to both sides of the liquid metal, we induce a surface tension gradient, propelling the fluid from the reservoirs toward the minichannel. Notably, the two entering liquids are distinctly colored, allowing us to quantify mixing using a Mixing Index (MI) definition and image processing techniques. Our investigation centers on four key variables governing mixer performance: applied voltage, liquid metal droplet diameter, input angle between the branches, and minichannel width. Given the experimental nature of our research, we employ a central composite design method within the framework of design of experiments (DoE). From our obtained experimental results, we establish correlations between MI and the other variables. Our examination of the four mentioned parameters revealed that liquid metal droplet diameter exerts the most significant influence on the mixing index. Following this, in descending order of impact, we find applied voltage, input angle, and channel width. In the optimal dimensions of our mixer, we achieve a remarkable maximum MI of 0.867.

Optimization of Polylactide-Co-Glycolide-Rifampicin Nanoparticle Synthesis, In Vitro Study of Mucoadhesion and Drug Release.

Despite the large number of works on the synthesis of polylactide-co-glycolide (PLGA) nanoparticles (NP) loaded with antituberculosis drugs, the data on the influence of various factors on the final characteristics of the complexes are quite contradictory. In the present study, a comprehensive analysis of the effect of multiple factors, including the molecular weight of PLGA, on the size and stability of nanoparticles, as well as the loading efficiency and release of the antituberculosis drug rifampicin (RIF), was carried out. Emulsification was carried out using different surfactants (polyvinyl alcohol, Tween 80 and Pluronic F127), different aqueous-to-organic phase ratios, and different solvents (dichloromethane, dimethyl sulfoxide, ethyl acetate). In this research, the PLGA nanoemulsion formation process was accompanied by ultrasonic dispersion, at different frequencies and durations of homogenization. The use of the central composite design method made it possible to select optimal conditions for the preparation of PLGA-RIF NPs (particle size 223 ± 2 nm, loading efficiency 67 ± 1%, nanoparticles yield 47 ± 2%). The release of rifampicin from PLGA NPs was studied for the first time using the flow cell method and vertical diffusion method on Franz cells at different pH levels, simulating the gastrointestinal tract. For the purpose of the possible inhalation administration of rifampicin immobilized in PLGA NPs, their mucoadhesion to mucin was studied, and a high degree of adhesion of polymeric nanoparticles to the mucosa was shown (more than 40% within 4 h). In the example of strain H37Rv in vitro, the sensitivity of Mycobacterium tuberculosis to PLGA-RIF NPs was proven by the complete inhibition of their growth.

Parameter optimization of ultrafine molybdenum powder during hydrogen reduction of MoO2 based on central composite design method

The hydrogen reduction of MoO2 is a common method for preparing ultrafine molybdenum powder, which is an important basic material for manufacturing high-performance Mo-based alloys. However, its preparation parameters are usually hard to be controlled. To address this issue, the work conducted the parameter optimization research during the hydrogen reduction process with using central composite design method, and the influence of different parameters such as reaction temperature, yttrium content, and hydrogen flow rate, on the particle size and oxygen content of the prepared molybdenum powder were investigated. The findings showed that the particle size of the prepared molybdenum powder is gradually decreased with the increase of reaction temperature and yttrium content, while gradually increased with the increase of hydrogen flow rate. The oxygen content of the prepared molybdenum powder is gradually decreased with the increase of reaction temperature and hydrogen flow rate, while gradually increased with the increase of yttrium content. Reaction temperature and yttrium content have significant interactions on the particle size and oxygen content are also concluded, and their respective regression model equations are obtained. The result also demonstrated that the particle size and oxygen content of the prepared molybdenum powder had a certain contradictory relationship. Through the comprehensive analysis, the optimal parameters for preparing ultrafine molybdenum powder with a low oxygen content are deduced, that is, reaction temperature: 1200 K, yttrium content: 0.1 mass%, and hydrogen flow rate: 1000 mL/min. Under the conditions, the average particle size and oxygen content of the prepared molybdenum powder are 320 nm and 0.456 mass%, respectively.

A flexible and efficient calibration method for discrete element simulations of additive manufacturing in construction

Extrusion-based 3D concrete printing (E3DCP), as one of the most advanced Additive Manufacturing processes, is a hotspot in the construction industry. Using the Discrete Element Method (DEM), the E3DCP can be investigated with reduced prototyping- and trial costs. However, DEM parameter calibration is challenging in the accurate simulation of construction materials because they are hardly typical granular matters. In addition, the introduction of a novel extrusion-based process Near-Nozzle-Mixing calls for a more flexible, efficient, and reliable calibration procedure due to the useable wide variety of material models.In this study, DEM simulation parameters of mortar and its components (e.g. Poraver® and paste) were thoroughly calibrated based on the central composite design method. Notably, the specific shape indices of related substrates were identified in the study to achieve the precise calibration of Poraver® and paste. Moreover, the European standard-based Haegermann flow table test was applied in the calibration by quantifying mortar consistency. This work provides a holistic and efficient calibration approach for three typical and physically different construction materials, which can be universally explored in the DEM simulation of most materials in E3DCP.

Application of MoS42−intercalated magnetic layered double hydroxide for preconcentration of cadmium and lead from water samples

A MoS42−-intercalated magnetic FeMgAl layered double hydroxide (Fe3O4@MoS42−-FeMgAl LDH) nanocomposite was synthesised via hydrothermal assisted exfoliation. The material was applied as the adsorbent for extraction, preconcentration and removal of cadmium ions (Cd2+) and lead ions Pb2+ from wastewater and river water. The structural properties and morphologies of the adsorbent were determined by transmission electron microscopy (TEM), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), zeta potential and X-ray diffraction (XRD). The parameters influencing preconcentration and the adsorptive removal process were optimised using the central composite design (CCD) method. The concentration of Cd2+ and Pb2+ in the samples was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The preconcentration method developed in the study was ultrasound-assisted magnetic solid phase extraction (UA-MSPE). Under optimum conditions, linearity was 0.1-800 µg/L with a correlation of determination (R2) of 0.9987. The uncertainty of the slope and the uncertainty of the intercept were both lower than the uncertainty of the calibration indicating good precision, selection of standards closest to a blank and wide range. Precision expressed as %RSD for both intra-day (n = 27) and inter-day (n = 9) were found to be 3.3 % and 7.0 % respectively. The limit of detection (n = 10) and limit of quantification (n = 10) of the UA-MSPE/ICP-OES were 0.03 µg/L and 0.10 µg/L. The developed method was applied for real sample analysis. Herein, influent wastewater was reported as 1.77 ± 0.14 and 6.53 ± 0.33 ug/L for Cd2+ and Pb2+, respectively while the effluent was reported at 0.96 ± 0.07 and 2.57 ± 0.13 ug/L, respectively. River water samples were found to be 0.45 ± 0.01 and 1.23 ± 0.04 ug/L, respectively proving that the adsorbent is capable of preconcentrating the target analytes.

Bacterial growth inhibition in spring water utilizing silver nanoparticles: Optimization using central composite design

Ensuring safe drinking water remains a significant challenge due to the prevalence of waterborne diseases. While chlorine-based and UV-based methods effectively kill pathogens, they often generate harmful byproducts. Consequently, there's a pressing need for innovative techniques, such as utilizing silver nanoparticles(AgNPs) renowned for their antibacterial properties. In this study, a chemical reduction technique was employed to synthesize AgNPs. Subsequently, these AgNPs underwent comprehensive characterization using techniques such as FTIR, XRD,TGA and XPS. The synthesized nanoparticles were then applied for disinfecting spring water. The experimental design was meticulously planned using the central composite design method (CCD) from Response Surface Methodology (RSM), facilitated by Design Expert software. Three key factors: AgNPs, pH, and contact time were varied across three levels, resulting in a total of 20 designed experiments. These experiments were conducted in accordance with the specified run order, culminating in the achievement of maximum bacteria growth inhibition efficiency of 99.72 % at the optimal conditions of 0.01 mg/100 mL AgNPs dose, a pH of 6, and a contact time of 20 min. Overall, the findings of this study underscore the efficiency of AgNPs in disinfecting spring water.

Optimization of CNC milling parameters using the response surface method for aluminum 6061

The manufacturing sector is constantly seeking ways to optimize the machining process, specifically for 3-axis CNC machines. This study aims to identify the optimal parameter values that result in the lowest roughness and the highest process capability in 3-axis CNC milling. The roughness level (Ra) of the product is primarily influenced by factors such as feed rate, spindle speed, and depth of cut. Additionally, the reliability of the machining process was analyzed to evaluate its ability to consistently achieve low roughness values and to validate the process capability of the VH850L3 series 3-axis CNC milling machine. The suggested approach for this analysis was the RSM central composite design method, which involved conducting experiments under various input conditions. The results indicated that the feed rate had the most significant impact on roughness, followed by the spindle speed, while the depth of cut had no effect. The parameters that resulted in the lowest roughness response were a spindle speed of 2589.76 rpm, a depth of cut of 0.159 mm, and a feed rate of 247.731 mm/min. These parameter values were tested on a 3-axis CNC machine, and the resulting data exhibited variations. Data processing revealed that the machine still performed optimally in the machining process, as indicated by the value of . However, the milling process deviates from the standard target, as the response value shows significant variation with a Cpk value 1.

Chlorogenic Acid: HPLC Quantification and In Vitro Assessment of Proliferative and Migration Effects on Human Dermal Fibroblast Cells

Chlorogenic acid (CA) exhibits diverse biological activities, including antioxidant and antiinflammatory effects. This research aims to develop, optimize, and validate an HPLC method to quantify CA in methanol and investigate its in vitro proliferative and cell migration effects on human-dermal-fibroblast (HDF) cell lines in a dose-dependent manner. The HPLC experimental conditions were optimized using the central composite design (CCD) method for determining CA. Chromatographic separation occurred at a wavelength of 330 nm. Under the optimized conditions, the method exhibited linearity across a concentration range of 0.1-100 µg/mL, demonstrating sensitivity (LOQ:0.1µg/mL), precision (RSD%≤3.32), and accuracy (RE%≤4.05). To evaluate the in vitro proliferative and cell migration effects on HDFs, we employed the XTT cell proliferation assay and TAS-TOS commercial kits. The XTT assay revealed that CA displayed a proliferative effect within the concentration range of 75-250 µM (P &amp;lt;0.01), and at a concentration of 125 µM, TAS levels increased significantly (P&amp;lt;0.05). The scratch assay demonstrated that HDF cell migration increased at 12 h, with substantial closure of the wound area at 24 h when treated with CA concentrations between 75-125 µM. The results demonstrate that pure chlorogenic acid extracted from plants exhibits dose-dependent effects on cell proliferation, antioxidant, and cell migration

Analysis and Testing of Pre-Cut Sugarcane Seed Stalk Sawing Performance Parameters

Sugarcane is an important economic crop in tropical and subtropical regions. Presawing planting is an important method for achieving automated and precise planting with sugarcane planting machines. The sawing process is a key stage in planting management, affecting not only the germination and survival rates of sugarcane, but also reflecting the mechanical performance of sawing. To reduce the peak sawing force and enhance the sawing surface quality of sugarcane seedlings, this study utilized a central composite experimental design method. Single-factor and multi-factor experiments were conducted with a specially designed sugarcane stalk sawing experimental rig to investigate the impact of factors such as the stalk diameter feeding speed, and sawing speed on the peak sawing force and sawing surface quality. Upon being developed and validated, multivariate mathematical regression models elucidated the relationships among these factors. The experimental results showed that the order of influence of each factor on the peak sawing force was the stalk diameter, feed speed, and sawing speed, while for the sawing surface quality, the sequence was the sawing speed, stalk diameter, and feed speed. Correspondingly, the determination coefficients for the peak sawing force and sawing surface quality prediction models were 0.9708 and 0.9675. With a maximum error of 7.6% for the peak sawing force and an average relative error of 7.1%, and a maximum error of 3.5% for the sawing surface quality and an average relative error of 2.83%, the calculated results from the regression models were in good agreement with the experimental findings. This indicates that the models are capable of quickly and accurately predicting the peak sawing force and sawing surface quality of sugarcane stalks under different conditions. The research findings provide valuable insights for the development and optimization of sugarcane stalk presawing equipment and related experimental studies.

Removal of river water turbidity and total dissolved solids using natural coagulants derived from banana peel and Moringa stenopetala seed

ABSTRACT In this study, natural coagulants obtained from banana peel and Moringa stenopetala seed were applied to remove total dissolved solids (TDS) and turbidity from river water. Central composite design (CCD) method was applied for the operating conditions of pH (3–10), coagulant dosage (0.3–1 g/L), stirring speed (30–90 rpm), and settling time (20–60 min). The optimum conditions obtained from the numerical optimization for pH, coagulant dosage, stirring speed, and settling time were 8.52, 1.000 g/L, 33.58 rpm, and 37.92 min, respectively, with a desirability value of 0.883 when banana peel powder was used as a natural coagulant. Under those optimum conditions, the experimental results for banana peel showed 81.32 and 93.09%, removal efficiency for TDS and turbidity, respectively. Similarly, the optimum conditions obtained from numerical optimization for pH, coagulant dosage, stirring speed, and settling time were 9.99, 0.999 g/L, 30.0 rpm, and 39.96 min, respectively, with a desirability value of 0.963. Under these optimum conditions for M. stenopetala seed powder, the experimental results showed 83.64 and 95.13%, removal efficiency for TDS and turbidity, respectively. Overall, M. stenopetala seed powder shows a higher potential for TDS and turbidity removal efficiency than banana peel powder.

Tribological Behaviour of Short Carbon Fiber Reinforced Polyethersulfone Composites with PTW Filler

In various applications like bearings, gear pairs, and brake pads, understanding how polymer composites interact with harder counterparts during sliding motions is crucial. A challenge arises from the heat generated during sliding friction, which has the potential to raise the contact temperature. This temperature increase, if it exceeds the material's glass transition temperature, can compromise the thermal stability of the composites, leading to rapid material wear. In the present investigation, dry sliding wear test was performed on 25 wt. % of short carbon fiber (SCF) reinforced polyethersulfone (PES) composites filled with 2.5 and 5.0 wt. % of potassium titanate whisker (PTW) using pin-on-disc tribometer. Wear test was planned and executed according to the experiment design formulations obtained by central composite design method. Contact temperature at the interface between composite pin and steel disc was monitored with an infrared thermal camera. Wear resistance was found to increase with the addition of fibers and fillers. PTW filled composites exhibited minimum wear with maximum coefficient of friction. Morphology studies were carried out on worn surfaces of the composites using scanning electron microscope to identify and describe the mechanism of wear involved. This investigation sheds light on the intricate behavior of polymer composites during sliding interactions.

Pemanfaatan Cangkang Kerang Darah Sebagai Katalis dan Filter Rokok Sebagai Adsorben Dry Washing dalam Pembuatan Biodiesel Minyak Kesambi

These three wastes can be used as raw materials for biodiesel in the transesterification and purification processes. The purpose of this study was to determine and analyze the variations of blood clam shell catalysts and cigarette butt adsorbents and to compare the most optimal quality of biodiesel (producing the highest yield) based on SNI 7182:2015. The method used in this research consists of FFA testing, degumming, esterification, tranesterification and purification processes. In the transesterification process, a catalyst was added in the range of 2-6% m/v and 75% methanol, while in the refining process, active charcoal filter cigarette adsorbents were added in the range of 5-10% m/v. The data obtained was subjected to statistical analysis using the Response Surface Methodology (RSM) Central Composite Design (CCD) method. Based on statistical analysis, a linear model equation was obtained and there were no optimum and minimum points. This research also obtained the highest bisodiesel yield of 73.33% at a catalyst concentration of 6% m/v and adsorbent of 5% m/v. Some of the quality characteristics of the biodiesel produced are in accordance with SNI standards.

Complex modal optimization of the disk brake based on thermal–structural coupling

The brake disk and friction material parameters were taken as design variables, with the negative damping ratio of the unstable mode as the optimization target. The central composite design method was employed to obtain suitable data sample points. A neural network response surface model was constructed to predict the real part values of the unstable mode. Structural optimization design was then conducted using a screening method to derive optimized parameters for the brake disk structure and physical parameters such as density, elastic modulus, and Poisson’s ratio of the friction material. The optimized coefficient of the negative damping ratio of the brake system’s unstable mode was enhanced, thereby reducing the likelihood of brake squeal. Harmonic response analysis showed a significant optimization effect on the curve of brake disk amplitude fluctuations with frequency. These findings offer valuable insights for improving the stability of disk brake systems.