Factorial Experimental Design Approach Research Articles

Optimization and Validation of a Plaque Reduction Neutralization Test for the Detection of Neutralizing Antibodies to Four Serotypes of Dengue Virus Used in Support of Dengue Vaccine Development

A dengue plaque reduction neutralization test (PRNT) to measure dengue serotype–specific neutralizing antibodies for all four virus serotypes was developed, optimized, and validated in accordance with guidelines for validation of bioanalytical test methods using human serum samples from dengue-infected persons and persons receiving a dengue vaccine candidate. Production and characterization of dengue challenge viruses used in the assay was standardized. Once virus stocks were characterized, the dengue PRNT50 for each of the four serotypes was optimized according to a factorial design of experiments approach for critical test parameters, including days of cell seeding before testing, percentage of overlay carboxymethylcellulose medium, and days of incubation post-infection to generate a robust assay. The PRNT50 was then validated and demonstrated to be suitable to detect and measure dengue serotype-specific neutralizing antibodies in human serum samples with acceptable intra-assay and inter-assay precision, accuracy/dilutability, specificity, and with a lower limit of quantitation of 10.

How nutrient availability influences acclimation to shade of two (pioneer and late-successional) Mediterranean tree species?

Examining ecological limits to shade acclimation at whole-plant level is determinant for evaluating the success of sapling establishment in low-light environments. We studied nutritional effects on whole-plant development in response to shade in two Mediterranean forest tree species with different successional status: the early-successional Pinus halepensis Mill. and the late-successional Quercus pubescens Wild. Through a nursery-based factorial experimental design approach, we measured height increment along 2 years and final leaf, stem and root biomass in both species saplings subjected to two lights and two soil nutrient availability treatments. The shade avoidance response was exclusive to P. halepensis, appeared as timely dependent, and persisted longer in saplings exposed to higher nutrient availability. Q. pubescens benefited from the higher nutrient availability by lowering the light-driven plastic response in aerial support investment and belowground carbon allocation, whereas P. halepensis heightened its light-driven plastic response. These contrasted responses are thus clearly related to the shade acclimation strategy of each species: the shade-intolerant P. halepensis enhances shade avoidance when non-nutrient-limited, whereas the shade-tolerant Q. pubescens assumes a conservative strategy by limiting phenotypic plasticity-induced costs. Maintaining greater shade avoidance in non-nutrient-limited soil conditions might be an adaptive advantage for P. halepensis seedlings growing in the understory, in response to gap formation in the overstory. In contrast, the more conservative and less costly shade responsiveness of Q. pubescens may confer it a better adaptive advantage in long-term light-limited environments.

Influence of Cutting Parameters on Surface Roughness for Wet and Dry Turning Process

This paper presents a study of the quality of a surface roughness model for mild steel with coated carbide cutting tool on turning process. The experiments were carried out under wet and dry cutting conditions. The model is developed based on cutting speed, feed and depth of cut as the parameters of cutting process. This research applies the fractional factorial design of experiment approach to studied the influence of cutting parameters on surface roughness. The measured results were collected and analyzed using commercial software package called Minitab. Analysis of variances is used to examine the influence of turning factors and factor interactions on surface roughness. The result indicated that, there are inherent differences in surface roughness between wet and dry cutting process with the same parameters process model. Analysis of variance was found that feed parameter is the most significant cutting parameter, which influences the surface roughness. The most significant interactions were found between cutting speed and feed parameters for dry turning process. Therefore is a significant effect of using combination of the fluid for cooling the cutting operation.

A factorial design of experiments approach to synthesize CZTS absorber material from aqueous media

ABSTRACTCu2ZnSnS4 (CZTS), an emerging p-type quaternary chalcogenide, offers many potential advantages as an absorber material. Using factorial design of experiments approach, single stage Cu-Zn-Sn co-electrodeposition from aqueous solution followed by annealing is reported in this paper. Factorial experiments facilitate to study the effects of each factor on the response variable as well as effects of interactions between individual factors on the response variable. Selected factors include concentration of individual ionic species, time of sulfurization and amount of complexing agent, whereas CZTS phase, band gap, carrier concentration, open circuit voltage, and morphological characteristics are the response variables. A model has been developed to show and predict the domain for the best possible factors for CZTS based device fabrication.

On-line preconcentration and recovery of palladium from waters using polyaniline (PANI) loaded in mini-column and determination by ICP-MS; elimination of spectral interferences

The applicability of polyaniline (PANI) for the on-line preconcentration and recovery of palladium from various water samples has been investigated. Batch experiments were performed to optimize conditions such as pH and contact time to achieve quantitative separation of Pd spiked at high (μg ml −1) and low levels (ng ml −1). During all the steps of the removal process, it was found that Pd was selectively removed by PANI even in the presence of various ions. Quantitative removal of Pd occured in the entire studied pH range (1–12) and the K d value was found to be >10 6. Kinetic studies show that a contact time of <4 min was adequate to reach equilibrium. The retained Pd was subsequently eluted with a mixture of HCl and thiourea, optimized using a factorial experimental design approach. ICP-OES was used for the micro-level determinations of Pd whereas ICP-MS was used for the determination of Pd at sub-ppb levels. Breakthrough curve using column experiments demonstrated that PANI has an excellent ability to accumulate up to ∼120 mg g −1 of Pd from synthetic sample solutions. A preconcentration factor of about 125 was achieved for Pd when 250 ml of water was passed. PANI columns prepared were used up to 10 times in consecutive retention–elution cycles without appreciable deterioration in their performance. The proposed on-line method also has the ability to remove interfering elements Cu and Y for the determination of Pd in waters by ICP-MS. The reported method has been applied successfully for the determination of Pd in ground water, lake water sea-water and waste water samples. The recoveries were found to be >95% in all cases. These studies indicate that PANI has an excellent ability to preconcentrate Pd from various waters making the method very promising for the determination of Pd.

Factorial experimental design approach in semicontinuous emulsion polymerization of methyl methacrylate to study the effect of process variables

AbstractThis article describes the effect of various process variables in the semicontinuous emulsion polymerization of methyl methacrylate. A series of poly(methyl methacrylate) (PMMA) emulsions were prepared using ammonium persulphate as initiator in absence and presence of Dowfax 2AI as surfactant. The effect of process variables such as initiator concentration, monomer concentration (solid content), surfactant concentration, reaction temperature, monomer feeding time, and holding time were systematically studied on monomer conversion, particle size, gel content, and molecular weight using a two‐level fractional factorial experimental method. Analysis of fractional factorial design revealed that surfactant concentration, monomer concentration, initiator concentration, and monomer feeding time affect all the properties. However, the surfactant concentration and the interaction effect of initiator and monomer feeding time are the key variables influencing the properties of PMMA latex. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effects of area ratio and nature of surfaces on scuffing in lubricated contacts

Heavily loaded moving machine components encounter severe tribological problems. Typical examples include piston and cylinder contacts in a hydraulic motor. Piston and cylinder bore contacts invariably operate in boundary lubrication regime and the risk for seizure of these contacts is high particularly when lubricated with low-viscosity lubricants. The piston assembly in a radial piston hydraulic motor has conformal (area) contact. In this work, these contacts have been simulated in the laboratory by using a thrust washer test configuration. The influence of area ratio, nature of contacting surfaces, and speed on scuffing has been investigated by using a factorial design of experiments approach. The influence of area ratio on wear at lower speed has also been studied. The results have revealed that the surface power, or μ pv-value, at scuffing varies by 3—4 times when the area ratio was increased from 8 to 72 per cent. The running-in wear tests have shown that running-in of the upper and lower specimens also varies with the area ratio. During the first 30 s the upper specimen is polished with low area ratio, whereas the lower specimen is polished with high area ratio. The surface temperature was estimated by using finite-element calculation and it was found to be similar prior to scuffing for both 8 and 72 per cent area ratios at 1.7 m/s sliding speed. The comparison of the results with the actual motor tests shows that an area ratio of 24 per cent seems to simulate the piston-cylinder contact better.

Screening of factors influencing the performance of manipulator using combined array design of experiment approach

A robot must manipulate objects with high accuracy and repeatability to perform precise tasks. However, deviation in performance is attributed to uncertainties and improper selection of control, noise, and process factors. The information regarding the effect of these factors on performance is almost non-existent. A probabilistic approach has been used to model and simulate the performance of manipulator. The combined array fractional factorial design of experiment approach has been employed to identify the significant factors and their interactions. This approach helps in screening of the manipulator factors and focus on those that are important. To explore further, two indices, viz. link length ratio and link mass ratio, have been proposed and impact of these indices on manipulator performance is investigated. A two degree of freedom (2-DOF) RR planar manipulator performing a task with cubic and quintic trajectory has been used to illustrate the approach. It has been observed that the statistically significant factors are different for different tasks in workspace. It has also been observed that for the same task, factors responsible for performance variations are different for cubic and quintic trajectories. Finally, it has been demonstrated that the link length ratio change has significant influence on performance compared to link mass ratio.

Quasi-Automatic Monitoring System For Turning Operation Using Acoustic Emission Signal Response And Factorial Design Method

This work discusses the generation of a quasi monitoring system intended for an operator to change cutting tool during turning operation. The monitoring system uses the effects of turning va riables on acoustic emission signal responses and factorial experimental design approach. In cutting operations, acoustic emission provides useful information concerning the tool wear condition because of the fundamental differences between its source mechanisms in the rubbing friction on the wear land of the single point tool. In this study, effects of cutting speed, feed and tool condition on the acoustic emission signal are investigated using acoustic emission's energy, amplitude, and frequency response and 23 factorial design for turning operation. Cutting tests were performed using high-speed steel under dry conditions. Calculated effects, standard errors at 95% confidence level, and models governing the acoustic emission response to the cutting conditions have been generated from the acoustic emission signal responses. The generated models revealed that acoustic energy response is affected by significant interactions between cutting speed and feed, and insignificant interactions between cutting speed and tool condition, while the acoustic amplitude response is affected by insignificant interactions among cutting speed, feed, and tool condition. These results suggest that acoustic emission's energy and amplitude responses could be used to control the cutting speed and feed during turning operation, thus prolonging the life of the cutting tool.Journal of Science & Technology (Ghana) Vol. 27 (2) 2007: pp. 107-121

Getting accurate nanoindentation data from time-dependent and microstructural effects of zinc

Abstract The main objective of this study was obtaining accurate data from nanoindentation experiments on zinc. Nanoindentation experiments can be performed under displacement control, load control, or open loop conditions at different loading/unloading rates. All the above control schemes and range of loading rates were used to test pure zinc samples with different surface preparation using a Hysitron Triboindenter fitted with a blunt Berkovich indenter. The results showed that displacement control with a high loading/unloading rate gave the most reliable results. However, because of the anisotropy of zinc and its large grain size the material should be considered as a single crystal on the scale of the impression generated. It has been found that using the feedback control of nanoindentation experiments can give a significant improvement in the results compared to open loop control due to the time-dependent behaviour of zinc. A full factorial design of experiments approach was performed to investigate the optimum combination of the feedback parameters to obtain accurate and reliable data for the hardness and Young's modulus of zinc.

Arsenic determination in gasoline by hydride generation atomic absorption spectroscopy combined with a factorial experimental design approach

Three locally collected gasoline samples were analyzed for arsenic content using factorial experimental design (FED) with hydride generation atomic absorption spectrometry (HGAAS). Five factors (including the reduction agent flow, the acid flow, the sample flow, the reductor concentration and the acid concentration) in two levels (low and high) were used in this optimization process. In order to design the surface response, five levels of central composite with 15 central points were down-selected. The results were compared with those determined by graphite furnace atomic absorption spectrometry (GFAAS) and a 95% confidence interval (regression procedure) was obtained. The HGAAS and GFAAS measurement sensitivities determined arsenic levels of 0.02 μg L −1 and 0.08 μg L −1, respectively.

Studies of the Flash Carbonization Process. 2. Violent Ignition Behavior of Pressurized Packed Beds of Biomass: A Factorial Study

The Flash Carbonization (FC) process is a novel procedure by which biomass is converted to biocarbon (i.e., charcoal) quickly and efficiently. To begin this process, a canister containing a packed bed of feedstock is placed within a pressure vessel, compressed air is used to charge the system to an initial pressure of ∼1−2 MPa, and a flash fire is ignited at the bottom of the bed. After about two minutes, air is delivered to the top of the bed and the biomass is converted to a high-yield biocarbon. In lab-scale tests, some fuels have been observed to ignite violently, resulting in a sudden drastic pressure rise (ΔP ≈ 1 MPa within 2−3 s). Because this event could be potentially hazardous, a study of this phenomenon was undertaken in preparation for a scale-up of the FC process to a commercial-sized demonstration reactor. The influence of initial pressure, feed moisture content, and ignition heater power were examined following a 23 full factorial experimental design approach. The combined effect of initial...

The effect of olive mill wastewater on seed germination after various pretreatment techniques

Olive mill wastewater (OMW) management has been a major issue of environmental concern for olive oil producing countries. OMW can be a serious nuisance, when disposed of untreated, due to its significantly high organic load, its phytotoxic properties and its relatively low biodegradability. Field and plant irrigation with raw or pretreated OMW is an easy and relatively inexpensive method to treat and dispose of OMW. Typical pretreatment techniques could be comprised of phase separation through a settling basin, dilution with water, aeration to promote biological degradation and pH neutralization. A full factorial experimental design approach was used here to study the main effects and interactions of the above four pretreatment techniques on the germination of tomato and chicory seeds. Results of the study showed that the most statistically significant technique affecting OMW phytotoxicity is water dilution. The next most significant technique was aeration. In particular, phytotoxicity decreased with increased OMW dilution with water, when OMW was aerated and without pH adjustment. pH neutralization resulted in increased phytotoxicity. Settling did not significantly decrease the phytotoxicity of settled OMW and is therefore not considered necessary in an OMW management system in which plant irrigation is the goal. The interaction of aeration and pH was, marginally, the most significant two-way interaction for tomato seeds, while no interactions were significant when chicory seeds were used.

Development and Calibration of Route Choice Utility Models: Factorial Experimental Design Approach

This paper provides a detailed overview on the state of practice in the area of data collection, modeling, calibration, and validation of route choice models. This paper presents a new approach for modeling route choice behavior using stated preference data coupled with rating (scoring) technique. The data collection was carried out over three stages; travelers’ scores of route attributes, attributes’ levels identification, and experimental templates for validation. A factorial experiment-design model was developed and validated through a two-stage procedure: the validation of the scoring technique, and the validation of the developed factorial experiment design model. Results indicated the dominant influence of travel time, and queuing time information on the route choice decisions. Other factors such as the speed, highway class, familiarity, and highway/pavement conditions were also found significantly important. The results include the percentages of the factors’ contributions to the route utility, and the relationships derived to illustrate the effect of the factors’ interactions on the travelers’ route utility.

Use of factorial designs to optimize animal experiments and reduce animal use.

Optimization of experiments, such as those used in drug discovery, can lead to useful savings of scientific resources. Factors such as sex, strain, and age of the animals and protocol-specific factors such as timing and methods of administering treatments can have an important influence on the response of animals to experimental treatments. Factorial experimental designs can be used to explore which factors and what levels of these factors will maximize the difference between a vehicle control and a known positive control treatment. This information can then be used to design more efficient experiments, either by reducing the numbers of animals used or by increasing the sensitivity so that smaller biological effects can be detected. A factorial experimental design approach is more effective and efficient than the older approach of varying one factor at a time. Two examples of real factorial experiments reveal how using this approach can potentially lead to a reduction in animal use and savings in financial and scientific resources without loss of scientific validity.

Factorial design of experiments on the effect of surface charges on stability of aqueous colloidal ceramic suspension

The present investigation was aimed at studying the synergistic effects of different surface-active agents (SAA) on the stability of aqueous alumina suspensions. The SAA used were dibasic ammonium citrate as dispersant, albumin as binder and octanol-2 as an antifoaming agent. Stability of suspensions was assessed through measurement of the specific surface charge of the system, using the fact that the particles exhibit maximum repulsion between them at high magnitude of surface charge. The experiments were statistically designed to bring out the effect of each variable as well as the effect due to interactions. The results show that the strongest affects on stability of aqueous colloidal suspension is that of dibasic ammonium citrate and albumin. The effect of interactional parameters, though slightly favourable for increasing the stability of the suspension, is very small. Dibasic ammonium citrate and albumin, both highly negatively charged SAA, stabilise the suspension by increasing the overall surface charges of the ceramic particles which inturn increases the overall repulsive forces. On the other hand, the positive charge of octanol-2 neutralises/decreases the magnitude of negative surfaces charge and, consequently, decreases the stability of the suspension. It has been shown that factorial design of experiment approach is very helpful in defining conditions for an optimum performance in such complex systems.

Factorial optimization of a six-cellulase mixture

A factorial experimental design approach was used to optimize mixtures of six cellulases (five Thermomonospora fusca cellulases and plus/minus Trichoderma reesei CBHI along with beta-glucosidase) so as to maximize the glucose produced from filter paper. Optimized mixture A and mixture B produced glucose at 25 and 8.3 μmol glucose/μmol enzyme/min, respectively, which are 8 and 1.5 times higher than the sum of the activity of the individual cellulases. In both mixtures, the glucose yield depended on the ratio and the cellulases used. Most enzymes showed synergistic interactions that increased the glucose yield. The yield of glucose with the optimum mixtures depended on the total enzyme concentration. Copyright 1998 John Wiley & Sons, Inc.

Effects of Ni(II) on respirometric oxygen uptake

The effects of Ni(II), substrate and initial biomass concentrations on biochemical oxygen demand (BOD) were studied by using an electrolytic respirometer. The effects of Ni(II) (2.5, 5.0, 10.0, 25.0 mg/l) and substrate (325, 650, 1300 mg/l as chemical oxygen demand) in a synthetic wastewater with differing initial biomass concentrations (1, 10, 100 mg/l) were investigated. The biomass-to-metal ratio was found to be the most important parameter affecting the measured BOD values. The maximum specific growth rates were calculated and the results of batch respirometric experiments were analysed both by graphical and statistical methods. In statistical analyses, a factorial experimental design approach was followed and results were treated by multiple regression techniques. A mathematical model was developed to express the maximum oxygen uptake in terms of nickel, substrate and initial biomass concentrations and their magnitudes of their effects were compared. The biomass-to-metal ratio was found to be very significant so that another model that expresses oxygen uptake in relation to the biomass-to-metal ratio and also to substrate concentration was developed. Finally, the effect of Ni(II) was demonstrated to depend on both substrate and initial biomass concentrations. This effect was stimulatory at low concentrations of Ni(II), and complete inhibition was never observed even at the highest concentration of Ni(II) studied, which was 25.0 mg/l.

Uncertainty and the acquisition of capacity: A competitive analysis

Motivated by experience with the telecommunications industry, analysis of a dynamic game approach to price competition is undertaken. In the underlying model, two firms competing for demand determine the amount of new capacity to be acquired which has the effect of reducing the unit cost of production and thereby the price charged for output. Using a factorial experimental design approach, policy oriented results are obtained which explore the effects of several factors in the exogenous environment (level of exogenous demand, purchase cost of capacity, and interest rate) on a firm's optimal behavior and competitive position. In particular, the experimental designs facilitate analysis of the impact of synergistic forces in the external environment. Lastly, the effect of different levels and forms of uncertainty associated with exogenous demand are explored.