Statistical Design Of Experiments Methodology Research Articles

Performance Assessment and Modeling of Routing Protocol in Vehicular Ad Hoc Networks Using Statistical Design of Experiments Methodology: A Comprehensive Study

The performance assessment of routing protocols in vehicular ad hoc networks (VANETs) plays a critical role in testing the efficiency of the routing algorithms before deployment in real conditions. This research introduces the statistical design of experiments (DOE) methodology as an innovative alternative to the one factor at a time (OFAT) approach for the assessment and the modeling of VANET routing protocol performance. In this paper, three design of experiments methods are applied, namely the two-level full factorial method, the Plackett–Burman method and the Taguchi method, and their outcomes are comprehensively compared. The present work considers a case study involving four factors namely: node density, number of connections, black hole and worm hole attacks. Their effects on four measured outputs called responses are simultaneously evaluated: throughput, packet loss ratio, average end-to-end delay and routing overhead of the AODV routing protocol. Further, regression models using the least squares method are generated. First, we compare the main effects of factors resulted from the three DOE methods. Second, we perform analysis of variance (ANOVA) to explore the statistical significance and compare the percentage contributions of each factor. Third, the goodness of fit of regression models is assessed using the adjusted R-squared measure and the fitting plots of measured versus predicted responses. VANET simulations are implemented using the network simulator (NS-3) and the simulator of urban mobility (SUMO). The findings reveal that the design of experiments methodology offers powerful mathematical, graphical and statistical techniques for analyzing and modeling the performance of VANET routing protocols with high accuracy and low costs. The three methods give equivalent results in terms of the main effect and ANOVA analysis. Nonetheless, the Taguchi models show higher predictive accuracy.

Tracking the thermal decomposition of plasma-sprayed hydroxylapatite

In modern orthopedics, plasma-sprayed hydroxylapatite coatings are applied routinely to metallic parts of hip and knee prostheses, as well as to dental root implants to render them osseoconductive, that is, able to assist the body in creating new bone by ingrowth of bone cells, blood capillaries, and soft tissue. In this work, hydroxylapatite coatings were deposited by atmospheric plasma spraying on titanium alloy substrates, and characterized by synchrotron radiation X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy. The deposition parameters were varied using a statistical design of experiments methodology. Depending on the degree of heat input and heat transfer rates, (1) dehydroxylated hydroxylapatite phases such as oxy- and oxyhydroxylapatite, (2) thermal decomposition phases (tri- and tetracalcium phosphates, CaO), and (3) amorphous calcium phosphate were formed. Implications of this research are that oxyapatite appears to be unstable at ambient conditions, and that proper selection of intrinsic plasma-spray parameters is key to the chemical stability and mechanical performance of the coating.

DoE Method for Operating Parameter Optimization of a Dual-Fuel BioEthanol/Diesel Light Duty Engine

In recent years, alcoholic fuels have been considered as an alternative transportation biofuel even in compression ignition engines either as blended in diesel or as premixed fuel in the case of dual-fuel configuration. Within this framework, the authors investigated the possibility to improve the combustion efficiency when ethanol is used in a dual-fuel light duty diesel engine. In particular, the study was focused on reducing the HC and CO emissions at low load conditions, acting on the most influential engine calibration parameters. Since this kind of investigation would require a significant number of runs, the statistical design of experiment methodology was adopted to reduce significantly its number. As required by the DoE approach, a set of factors (injection parameters, etc.) were selected. For each of them, two levels “high” and “low” were defined in a range of reasonable values. Combining the levels of all the factors, it was possible to evaluate the effects and the weight of each factor and of their combination on the outputs. The results identified the rail pressure, the pilot, and post-injection as the most influential emission parameters. Significant reductions of unburnt were found acting on those parameters without substantial penalties on the global engine performances.

Influence of process parameters on the content of biomimetic calcium phosphate coating on titanium: a Taguchi analysis.

In this study, a statistical design of experimental methodology based on Taguchi orthogonal design has been used to study the effect of various processing parameters on the amount of calcium phosphate coating produced by such technique. Seven control factors with three levels each including sodium hydroxide concentration, pretreatment temperature, pretreatment time, cleaning method, coating time, coating temperature and surface area to solution volume ratio were studied. X-ray diffraction revealed that all the coatings consisted of the mixture of octacalcium phosphate (OCP) and hydroxyapatite (HA) and the presence of each phase depended on the process conditions used. Various content and size (-1-100 μm) of isolated spheroid particles with nanosized plate-like morphology deposited on the titanium surface or a continuous layer of plate-like nanocrystals having the plate thickness in the range of -100-300 nm and the plate width in the range of 3-8 μm were formed depending on the process conditions employed. The optimum condition of using sodium hydroxide concentration of 1 M, pretreatment temperature of 70 degrees C, pretreatment time of 24 h, cleaning by ultrasonic, coating time of 6 h, coating temperature of 50 degrees C and surface area to solution volume ratio of 32.74 for producing the greatest amount of the coating formed on the titanium surface was predicted and validated. In addition, coating temperature was found to be the dominant factor with the greatest contribution to the coating formation while coating time and cleaning method were significant factors. Other factors had negligible effects on the coating performance.

A New Approach of Improving Rain Erosion Resistance of Nanocomposite Sol-Gel Coatings by Optimization Process Factors

Erosion protection nanocomposite sol-gel coatings based on tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxisilane (GPTMS) are prepared and characterized to protect marine structures susceptible to damage caused by liquid impact, e.g., the submarine body. This study focuses on the optimization of compositional and process parameters of transparent hybrid nanocomposite sol-gel coatings resistant to rain erosion by using statistical design of experimental methodology (DoE) based on Taguchi orthogonal design. The impact of compositional and process parameters of the coatings on the erosion protection performance is investigated by five-factor–four-level design methodology. Hybrid coatings were deposited on AA5083 by a dip coating technique. Optimization coatings are analyzed regarding their adhesion (pull-off), flexibility (impact and mandrel bending), hardness (pencil), wear (Taber wear index), and rain erosion resistance (stationary sample erosion test). The surface morphology and roughness were studied by field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The optimization coatings showed excellent flexibility and adhesion to the substrate with smooth nanostructure surface; the RMS surface roughness was 1.85 nm. The evaluation of the result obtained from abrasion shows cohesive and interfacial wear with abrasive and adhesive mechanisms, respectively. Liquid impact results show cohesive failure of the coatings without any sign of delamination.

Optimization of process factors for the synthesis of advanced chrome-free nanocomposite sol–gel coatings for corrosion protection of marine aluminum alloy AA5083 by design of experiment

Nanocomposite sol–gel coatings based on tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxisilane (GPTMS) have been prepared for corrosion protection of AA5083. Statistical design of experimental methodology based on Taguchi orthogonal design has been used to study and optimize various parameters using multifactor analysis of variance (ANOVA). The corrosion current density has been used as a response. Structure, surface morphology and composition of the hybrid coatings were studied by using SEM, AFM and ATR/FTIR, respectively. Corrosion performance of coatings was examined using potentiodynamic polarization and EIS. The results show that by proper choice of parameters, adherent, dense and protective hybrid coatings can be obtained.

A design of experiment aided sensitivity analysis and parameterization for hydrological modeling

To provide a better understanding of the water balance in the Deer River watershed of the Hudson Bay lowlands, the Semi-distributed Land Use-based Runoff Process hydrological model was applied to simulate the runoff over a 20 year period. The purpose of this study is to develop an approach to examine the sensitivity of the ten parameters and their interactions via statistical design of experiment methodology. Using the proposed approach, the contribution of each parameter and how they interact with one another were evaluated. The results indicated that the interaction between “retention constant for fast storage” and “precipitation factor” had the greatest positive impact on the Nash–Sutcliffe efficiency (NSE) and the quadratic factor term of “precipitation factor” had the greatest negative effect on the NSE. The proposed approach provided an effective tool for evaluating the contribution of the input parameters and could also be applied for calibration of other hydrological models.

Advanced chrome-free organic–inorganic hybrid pretreatments for aerospace aluminum alloy 2024-T3—application of novel bis-ureasil sol–gel precursors

Effective pretreatment of aluminum alloys is very critical to success of protective coating systems for aerospace applications. While chromate-based pretreatments have been very successful for corrosion protection, they have been a target for replacement due to the increasingly stricter regulatory requirements arising from toxicity and carcinogenic nature of Cr(VI) used in such pretreatments. Among many approaches to develop alternative systems, the organic–inorganic hybrid (OIH) coatings based on sol–gel technology has advanced rapidly. We have successfully developed OIH coating systems by using suitably tailored organosilane precursors and sol–gel processing conditions. A series of novel bis-ureasil precursors have been developed and employed as organic precursor of OIH systems. Statistical design of experimental methodology (DoE) has been used to study and optimize compositional and process parameters using multifactor analysis of variance (ANOVA) analysis method. The corrosion resistance study (Potentiodynamic polarization, salt-spray corrosion test) shows that by proper choice of sol–gel precursors, cross-linkers, and reaction conditions, very dense, adherent and protective hybrid coatings, comparable in performance to chromate-based ones, can be obtained for aerospace aluminum alloy 2024-T3.