Independent Process Variables Research Articles

Evaluation of mass exchange during osmotic dehydration of carrots using response surface methodology

Water and sucrose transfer were quantitatively investigated during osmotic dehydration of carrot slices using response surface methodology with the sucrose concentration (40–60%, w/w), temperature of sucrose solution (40–60 °C) and immersion time (0.5–6.0 h) being the independent process variables. Quadratic regression equations describing the effects of independent process variables on the water loss (WL) and sucrose gain (SG) were developed. It was found that immersion time and concentration of sucrose solution were the most significant factors affecting the WL during osmotic dehydration of carrots followed by temperature. Effect of temperature and time were more pronounced for SG than the concentration of sucrose solution. It is suggested that the regression equations obtained in this study can be used to find optimum conditions for the desired sensory and physical properties of sweet carrot products such as preserves.

Optimizing sugarbeet molasses distillery slops to olive mill husks ratio and incubation period for composting

This paper analyzes the influence of operating conditions, such as mixing ratio of the waste ingredients and extension of the stabilization time, on the composting of sugarbeet molasses distillery slops (DS) and olive mill husks (OMH). The addition of 0–40% sugarbeet molasses DS to the starting mixtures and the treatment duration (40 d) were tested at the bench to optimize the process dynamics using the in-vessel composting method. Changes of compost stabilization conditions (organic matter, nitrogen losses, germination index) were also related to the characteristics of the different end products obtained. A second-order polynomial equation based on two independent process variables was developed to model the composting of sugarbeet molasses DS – OMH mixtures. Differences between experimental values and data derived by the application of the model never exceeded 10%. The best results in terms of biodegradation rate (i.e., degree of stabilization), maturity, and limitation of Kjeldahl-N losses were observed with process times of 30–40 d and the addition of 0–10% sugarbeet molasses DS to OMH. Key words: biodegradability, compost, sugarbeet molasses distillery slops, olive mill husks.

A Novel Amylose Corn-Starch Dispersion as an Aqueous Film Coating for Tablets

A novel aqueous coating dispersion of amylose-rich corn starch (Hylon VII) was evaluated in an aqueous film-coating process of tablets using an instrumented laboratory-scale pan-coating apparatus. The influence of two independent process variables, the coating temperature and the atomizing air pressure, on the properties of the coated tablets were investigated. The pre-use stability of aqueous coating dispersion (i.e., amylose corn-starch precipitate) was studied using a powder X-ray diffraction (XRD) technique. The crystallinity of amylose starch in the coating dispersion was found to increase slightly during 9 months of storage (in a refrigerator 6±2°C). The film coatings of an aqueous amylose-rich starch dispersion were successfully applied onto tablets without any significant drawbacks, such as nozzle blockage or related problems. It was found that the temperature in the coating pan had a significant influence on the film surface roughness, mechanical strength, and drug release in vitro. When the lowest coating temperature (30°C) was used, rougher film coatings were obtained due to overwetting. At higher temperatures (up to 50–60°C), lower surface roughness and higher mechanical strength values for the coated tablets were obtained. With the present amylose starch dispersion, the atomizing air pressure had a minor influence on the quality of the coating. Under appropriate coating conditions, a smooth tablet film coating was produced with this new, natural, and inexpensive amylose starch dispersion.

Modelling vinasse/cotton waste ratio incubation for optimum composting

A central composite experimental design was used to investigate the influence of incubation conditions (vinasse added and operation time) for vinasse/cotton waste mixtures on the properties of products obtained (pH, electrical conductivity, organic matter, Kjeldahl-N, C/N ratio, biodegradability, Kjeldahl-N losses and germination index) in order to determine the best in-vessel composting conditions. The range of the independent variable measured was 0–80% for vinasse added and 1–50 days for operation time. A second-order polynomial model consisting of two independent process variables was found to accurately describe the vinasse/cotton waste incubation. The differences between the experimental values and those estimated by using the equations never exceeded 10% of the former. Obtaining products with acceptable chemical properties, high biodegradability and minimum N losses entails operating at medium operation time (20–35 days) and 20–30% of vinasse added.

Comparative statistical analysis of hole taper and circularity in laser percussion drilling

The present study investigates the relationships and parameter interactions between six controllable variables on the hole taper and circularity in laser percussion drilling. Experiments have been conducted on stainless steel workpieces and a comparison was made between stainless steel and mild steel (IMechE Part B: J. Eng. Manufact. (in press)). Laser peak power, laser pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position were selected as independent process variables. The central composite design (CCD) was employed to plan the experiments in order to achieve required information with reduced number of experiments. The process performance was evaluated in terms of equivalent entrance diameter, hole taper and hole entrance circularity. The ratio of minimum to maximum Feret’s diameter was considered as circularity characteristic of the hole. The models of these three process characteristics were developed by linear multiple regression technique. The initial models were computed according to the least squares procedure and were finalised by stepwise regression method. The significant coefficients were obtained by performing analysis of variance (ANOVA) at 1, 5 and 7% levels of significance. The final models were checked by complete residual analysis and finally were experimentally verified. It was found that the pulse frequency had a significant effect on the hole entrance diameter and hole circularity in drilling stainless steel unlike the drilling of mild steel where the pulse frequency had no significant effect on the hole characteristics.

Parametric Study of a Pressure Swing Adsorption Process

The performance of a pressure swing adsorption (PSA) process for production of high purity hydrogen from a binary methane-hydrogen mixture is simulated using a detailed, adiabatic PSA model. An activated carbon is used for selective adsorption of methane over hydrogen. The effects of various independent process variables (feed gas pressure and composition, purge gas pressure and quantity, configuration of process steps) on the key dependent process variables (hydrogen recovery at high purity, hydrogen production capacity) are evaluated. It is demonstrated that many different combinations of PSA process steps, their operating conditions, and the feed gas conditions can be chosen to produce an identical product gas with different hydrogen recovery and productivity.

Use of formaldehyde for making wheat straw cellulose pulp

A central composite design was used to investigate the influence of the cooking conditions (time, temperature and formaldehyde concentration) for wheat straw with formaldehyde–water mixtures on the properties of the pulp obtained (yield and holocellulose, α-cellulose, lignin and ethanol–benzene extractives contents) and the pH of the resulting wastewater. A second-order polynomial model consisting of three independent process variables was found to accurately describe the organosolv pulping of wheat straw. The equations derived predicted the yield, the holocellulose, α-cellulose, lignin and ethanol–benzene extractives contents of the pulp, and the pH of the wastewater with multiple- R, R 2, adjusted- R 2 and Snedecor F values of 0.99, 0.99, 0.99 and 321.33; 0.98, 0.95, 0.92 and 35.01; 0.92, 0.86, 0.78 and 10.68; 0.99, 0.97, 0.96 and 68.19; 0.91, 0.83, 0.80 and 29.68; and 0.97, 0.95, 0.93 and 46.10, respectively. While ensuring a high holocellulose content and low lignin and ethanol–benzene-extractive contents entails using high levels of the process variables involved, a compromise can be made in order to achieve both the previous objectives and a high α-cellulose content provided a long cooking time, a high temperature and a low formaldehyde concentration are used – alternatively, a long time, a high formaldehyde concentration and a low temperature can be equally effective and save energy. The yield, pH and holocellulose, α-cellulose, lignin and alcohol/benzene extractive contents are more sensitive to changes in the cooking time than they are to modifications of the formaldehyde concentration.

Use of butanol-water mixtures for making wheat straw pulp

A central composite design was used to investigate the influence of the cooking conditions (time, temperature and butanol concentration) for wheat straw with butanol-water mixtures on the properties of the pulp obtained (yield and holocellulose, α-cellulose, lignin and ethanol-benzene extractives contents) and the pH of the resulting waste water. A second-order polynomial model consisting of three independent process variables was found to accurately describe the organosolv pulping of wheat straw. The equations derived predict the yield, the holocellulose, α-cellulose, lignin and ethanol-benzene extractives contents of the pulp, and the pH of the waste water with multiple-R, R2, adjusted-R2 and Snedecor' F values of 0.99, 0.99, 0.99 and 310.33; 0.98, 0.97, 0.95 and 56.63; 0.91, 0.84, 0.74 and 9.14; 0.99, 0.98, 0.96 and 70.52; 0.97, 0.94, 0.92 and 40.42; and 0.98, 0.95, 0.93 and 49.33, respectively. The process variables must be set at low values in order to ensure a high yield and pH. On the other hand, if a high holocellulose content and low lignin and ethanol-benzene extractives contents are to be obtained, then the process variables must be set at high values. Finally, obtaining pulp with a high α-cellulose content entails using a long cooking time and a high temperature, as well as a low butanol concentration.

Organosolv pulping of wheat straw by use of acetone-water mixtures

A central composite design was used to investigate the influence of the cooking conditions (time, temperature and acetone concentration) for wheat straw with acetone-water mixtures on the properties of the pulp obtained (yield and holocellulose, α-cellulose, lignin and ethanol-benzene extractable contents) and the pH of the resulting waste water. A second-order polynomial model consisting of three independent process variables was found to accurately describe the organosolv pulping of wheat straw. The equations derived predict the yield, the holocellulose, α-cellulose, lignin and ethanol-benzene extractable contents of the pulp, and the pH of the waste water with multiple- R, R 2 and adjusted- R 2 high values. The process variables must be set at low values to ensure a high yield and pH. Conversely, if high holocellulose and α-cellulose contents and low lignin and ethanol-bezene extractable contents are desired, then a high temperature (200°C), an intermediate-to-long cooking time (95–100 min), and a low-to-intermediate acetone concentration (55–60%) must be used.

Organosolv pulping of wheat straw by use of phenol

A central composite design was used to investigate the influence of the cooking conditions (time, temperature and phenol concentration) for wheat straw with phenol-water mixtures on the properties of the pulp obtained (yield and holocellulose, α-cellulose, lignin and ethanol-benzene extractable contents) and the pH of the resulting wastewater. A second-order polynomial model consisting of three independent process variables was found to accurately describe the organosolv pulping of wheat straw. The equations derived predict the yield, the holocellulose, α-cellulose, lignin and ethanol-benzene extractable contents of the pulp, and the pH of the wastewater with multiple- R, R 2 and adjusted- R 2 high values. The process variables must be set at low variables in order to ensure a high yield and pH. Conversely, if high holocellulose and α-cellulose contents, and low lignin and ethanol-benzene extractable contents are desired, then a high temperature (200°C), long cooking time (120 min), and intermediate phenol concentration (65%) must be used.

Influence of granulation and compression process variables on flow rate of granules and on tablet properties, with special reference to weight variation

The influence of three independent fluidized bed granulation process variables (inlet air temperature, atomizing air pressure and binder solution amount) on the flow rate of granules and on the tablet properties was studied using the 3 3 factorial design. The dependence of the flow rate of granules, the tablet friability and the disintegration time of tablets on the fluidized bed granulation process variables was explained using the multilinear stepwise regression analysis. The flow time of the granules was affected by all three factors. The friability and the disintegration time of tablets were affected by the binder solution amount and the atomizing air pressure. The influence of inlet air temperature on the tablet responses was insignificant.

Optimization of Granulates in a High Shear Mixer by Mixture Design

AbstractOptimization of wet granulation in a 10 litre high shear mixer was examined by mixture design. Lactose, corn starch and cellulose microcrystalline were used as eccipients of the granules. Mixing ratios of these eccipients were selected as formulation factors. In addition, the impeller speed and granulation time was employed as independent process variables. A two-phase experimental strategy was drawn up: one phase for the percentages of the three eccipients and the other phase for the determination of the influence of process variable on geometric mean diameter. The percentages were studied using a Scheffe simplex-centroid design, and the other phase was examined using a Doehlert experimental matrix.

Escherichia coli plasmid production in fermenter

Escherichia coli harboring a recombinant plasmid was grown in a fermenter to study the effects of selected process parameters on the growth of the microbe and on plasmid amplification with chloramphenicol treatment. Eighteen fermentations were carried out according to a statistical experimental design in which the fermentation temperature, pH, and turbidity of culture at the onset of plasmid amplification were the selected independent process variables. Static regression models describing the process were derived from the experimental results. It turned out that recombinant plasmid copy numbers could be influenced by controlling fermentation temperature and pH. The maximal copy number during bacterial growth phase and the optimal plasmid production were found to require fermentation conditions different from those needed for optimal bacterial growth and cell division. The conditions also differed significantly from those routinely used in research laboratories for plasmid preparation. The chloramphenicol treatment increased the plasmid copy number compared with chromosome numbers up to fivefold. Some of the data suggest that under certain conditions the number of chromosome molecules in E. coli cells may rise during the plasmid amplification stage. Statistical experimental design, a nucleic acid sandwich hybridization technique for plasmid quantification, and regression models proved to be useful in this study.

Metallurgical conditions for development of adequate magnetic properties in grain oriented silicon iron

The mechanisms underlying the secondary recrystallization process in connection with the production of grain-oriented silicon iron have recently been clarified, throwing light on the microstructural parameters and the relationships which control the development of the final orientation. In particular, the interrelationships among grain growth, texture, and the presence of second-phase particles and/or segregating atoms has been quantified. The conditions which cause drastic deterioration in magnetic properties are analyzed here in terms of simple microstructural parameters, namely, the inhibition factor, which describes the amount of restraining force on grain growth, and the effective grain radius, which takes into account the driving force caused by grain boundary curvature and microstructural heterogeneity. It is shown that several independent process variables contribute to the modification of the microstructural parameters responsible for the secondary recrystallization instability and therefore for the magnetic properties. >

Metastable states in a food extrusion cooker

An extrusion cooking process for the manufacture of expanded wheat flour products was found to exhibit two states in which the system could come to equilibrium for the same settings of the independent process variables. Examination of the degree of fill in the sections of the screw and observations of the dependent process variables such as torque, pressures and mass temperatures enabled an explanation of the metastable states to be proposed related to moisture movement within the screw system. Certain design features of the screw system are proposed to eliminate this form of instability.

BUBBLE AND FOAM SEPARATION OF EMULSIFIED BITUMEN FROM TAR SAND WASTEWATER

Process waters generated by the steam purging of tar sand deposits in Vernal, Utah, were treated by means of second-stage foam separation and air flotation operations. Among the independent process variables considered were hydraulic detention time, air flowrate. temperature, and polymer or surfactant addition level. System performance evaluations were based on second-stage effluent levels of total organic carbon (TOC), chemical oxygen demand (COD), suspended solids (SS). total solids (TS), and turbidity. The results indicated that the most effective second-stage system studied was air flotation aided by polymer addition. Removals of TOC, COD, and SS accomplished by this system exceeded 98 percent.

Hydrodearomatization of liquid paraffins on palladized zeolite catalysts

The authors determine the influence of the SiO/sub 2/:Al/sub 2/O/sub 3/ mole ratio in the NaY support of palladium-containing catalysts on the efficiency of hydrogenation of aromatic hydrocarbons in petroleumderived liquid paraffins obtained by adsorption in a fluidized bed of zeolite. Catalyst preparation and the details of the experimental set up are described. The authors calculated the regression coefficients of the equations describing the conversion of the aromatic hydrocarbons in the liquid paraffin as a function of the independent process variables. An increase in the SiO/sub 2/:Al/sub 2/O/sub 3/ ratio from 3.8 to 5 in the skeleton of the zeolite support of palladium-containing catalysts, under otherwise equal conditions, leads to a substantial increase in the conversion of aromatic hydrocarbons in liquid paraffins. These data can be used in developing a palladium/zeolite catalyst for the hydrodearomatization of liquid paraffins.

Continuous aerobic conversion of poultry waste into single‐cell protein using a single reactor: Kinetic analysis and determination of optimal conditions

AbstractA single‐stage aerobic continuous process for the conversion of poultry waste into single‐cell protein is described. The slurried manure was supplemented by molasses. Kinetics and possible mechanisms for the suggested conversion‐scheme have been investigated. A Box–Wilson experimental design has been employed to elucidate the effect of environmental conditions on reactor performance. Temperature, pH, and percent solids concentration in the feed (media composition) were the independent process variables, while the minimum residence time for the nearly complete utilization of total uric acid and ammonia nitrogen, the amount of carbon required per gram of nitrogen consumed, and protein content of the product were considered as dependent variables. Optimal environmental conditions for the minimum raw material cost and for the maximum percent protein, lysine, and methionine content of the product were determined. The operating conditions of 25°C, pH 7.5, 1.5% solids in the feed, and a residence time of 8.1 hr were found to be the most appropriate conditions maximizing the “profit” function, which is defined as the difference between the product value and raw material cost.

Relationships of Processes of Care to Patient Outcomes

This study examined relationships between process and outcome components of patient care. Relationships were determined between independent process variables--diagnostic approach, therapeutic approach, and patient compliance--and dependent outcome variables--functional status, clinical health status, perception of health and care, and knowledge and understanding of disease and therapy. Criteria for process and outcome dimensions were developed, based on a literature review. Data on 103 patients, followed for a five-month period, were collected by use of patient record audit and beginning- and end-of-study patient interviews. Cross-tabulations and multiple regression analysis were used to determine relationships between independent and dependent variables. Analysis of variance was used to determine difference in provider and patient process dimensions according to patient severity groups. Significant relationships were found between all independent variables and the dependent variables of clinical health status and knowledge and understanding of disease and therapy. Patient compliance level was found to be the most significant process variable.

Mathematical Model for Enteric Film Coating of Tablets

The enteric film coating of placebo tablets, using a methacrylic acid-methyl methacrylate copolymer as the film former in the coating solution, was studied by statistical techniques. The effects of four independent formulation and process variables on the disintegration time of the coated film in simulated intestinal fluid and on the resistance to disintegration of the coated film in simulated gastric fluid were studied. The results of a statistically designed set of experiments were used as the input data. Regression analysis of these data resulted in two first-order polynomial equations. The linear model obtained for the disintegration time of the coating in the simulated intestinal fluid was analyzed by the steepest descent method to determine the most suitable combination of the independent variables.