pinecone/core-2020-05-10-deduplication huggingface dataset:
Observer Based Scheme for the Control of High Order Systems with Two Unstable Poles Plus Time Delay

International audienceThis paper deals with the problem of the stabilization and control of linear time invariant high order systems with two unstable real poles plus time delay. A simple observer based controller is designed in order to achieve a stable behavior of the closed loop system. Necessary and sufficient conditions for the existence of the proposed control structure are stated. Hence, only four proportional gains and the model of the plant are enough to obtain a stable response of the delayed system. Moreover, a robustness analysis is presented in order to compute the maximal uncertainty bound accepted for the delay term. In addition, a two degrees of freedom PI control action is implemented in order to track step references and to reject step disturbances. The achieved performance of the proposed control strategy is illustrated by mean of numerical simulations
Physicochemical characterization of starch isolated from red Monascus rice

Red Monascus rice (Ang-kak) is used as a traditional medicine and a natural colorant for food and beverages. Starch isolated from waste Ang-kak may compete economically with other common starch and give new value to this waste.\ud
Isolation by using alkaline method gave a product with a starch content of 81%. Impurities in the product are protein, fiber, ash, and secondary metabolites of the Monascus rice. Several physicochemical properties of the isolated starch were also investigated. It was found that 88.03% of the isolated starch is amylopectin. Thermogravitation study showed that the\ud
isolated starch degraded only slightly at temperature below 230 °C and can be considered as a new source of starch for various applications
Flow of non-Newtonian Fluids in Converging-Diverging Rigid Tubes

A residual-based lubrication method is used in this paper to find the flow
rate and pressure field in converging-diverging rigid tubes for the flow of
time-independent category of non-Newtonian fluids. Five converging-diverging
prototype geometries were used in this investigation in conjunction with two
fluid models: Ellis and Herschel-Bulkley. The method was validated by
convergence behavior sensibility tests, convergence to analytical solutions for
the straight tubes as special cases for the converging-diverging tubes,
convergence to analytical solutions found earlier for the flow in
converging-diverging tubes of Newtonian fluids as special cases for
non-Newtonian, and convergence to analytical solutions found earlier for the
flow of power-law fluids in converging-diverging tubes. A brief investigation
was also conducted on a sample of diverging-converging geometries. The method
can in principle be extended to the flow of viscoelastic and
thixotropic/rheopectic fluid categories. The method can also be extended to
geometries varying in size and shape in the flow direction, other than the
perfect cylindrically-symmetric converging-diverging ones, as long as
characteristic flow relations correlating the flow rate to the pressure drop on
the discretized elements of the lubrication approximation can be found. These
relations can be analytical, empirical and even numerical and hence the method
has a wide applicability range.Comment: 36 pages, 14 figures, 5 table
Simulation of full-scale reverse osmosis filtration system for the removal of N-nitrosodimethylamine from wastewater

YesReverse osmosis (RO) is becoming one of the most promising technologies used in wastewater treatment because it offers high rate of contaminant rejection and lower energy consumption in comparison with other thermal treatment processes. Earlier research by the same authors in respect of a distributed one-dimensional mathematical model for a single spiral-wound RO membrane module based on the solution-diffusion model has been used in this paper to simulate the rejection of NDMA (N-nitrosodimethylamine) from wastewater in a series of seven RO elements full-scale treatment plant. Firstly, the applicability of this model has been evaluated using a simulation study and the results have been compared against experimental data gathered from the literature for a given plant. Secondly, further simulation and analysis studies are carried out to assess the performance of the plant for NDMA rejection and recovery rate under different operating conditions of feed pressure, flow rate, and concentration. For the studied RO configuration, it is concluded that a maximum of 55.1% NDMA rejection can be achieved, which confirms the remaining issue of lower NDMA rejection
Optimal operation of tubular reactors for naphtha cracking by numerical
simulation

Process gas temperature profile and steam-to-hydrocarbon ratio in the feed have
important impact on product yields and coking rate in tubular reactors for
naphtha cracking. This study is to evaluate these effects quantitatively based
on numerical simulation. Steady-state operation of the tubular reactor in an
industrial thermal cracking furnace was first simulated in HYSYS with a
molecular reaction scheme. Various case studies then investigate the influence
of process gas temperature profile and inlet steam-to-hydrocarbon ratio so that
the ethylene/propylene product yields and coking rate can be evaluated. Finally,
steady-state optimization was applied to the operation of this industrial
furnace. The optimal process temperature profile and the optimal inlet steam-to-
naphtha ratio were found to maximize the operation profit. This study will
provide significant guidance to process engineers in the ethylene industry
Numerical analyses of bubble point tests used for membrane characterisation: model development and experimental validation

This is the pre-peer-reviewed version of an article submitted for publication in the Asia-Pacific Journal of Chemical Engineering [© Curtin University of Technology and John Wiley and Sons Ltd.], which has been published in its final form at: http://dx.doi.org/10.1002/apj.519A numerical model for simulating the microhydrodynamics inside different pore sizes was\ud
developed in this work, using a continuous penalty finite element scheme. This scheme\ud
combines the flexibility in modelling two phase systems, as the one simulated in this work\ud
with accuracy. The volume of fluid (VOF) method was applied to track the motion of the gasliquid\ud
interfacial boundary as an approach to monitor the repulsion of the wetting liquid from\ud
the pores to detect their bubble pressures. To resolve the complexities arising from the\ud
inclusion of the surface tension at the liquid-gas interface as an unknown dynamic condition\ud
it is treated as a resistance force in the equations of motion. The effects of the surface tension\ud
and other forces such as the buoyancy are then determined by model calibration with respect\ud
to a set of experimental data. To obtain the experimental data, the bubble point test was used\ud
to characterise different Nuclepore track etched membrane samples, which provided insights\ud
into the mechanisms underlying the test and into the interpretation of the pore size\ud
distribution. The experimental data are used to calibrate the numerical model. The calibrated\ud
model was, in turn, used to predict the outcome of bubble point tests for a range of inlet\ud
boundary conditions. The results obtained from these simulations are shown to be in good\ud
agreement with of the experimental data, indicating the ability of the developed model to\ud
accurately predict the bubble point pressure
Fluid Flow through 90 Degree Bends

Pressure drop measurement and prediction in curved pipes and elbow bends is reviewed for both laminar and turbulent single-phase fluid flow. For curved pipe under laminar flow, the pressure loss can be predicted both theoretically and using empirical relations. The transitional Reynolds number can be predicted from an empirical relation. Turbulent flow in curved pipes can only be theoretically predicted for large bends but there are a large number of empirical relations that have proved to be accurate. Elbow bends have proven to be difficult to both measure and represent the pressure loss. Methods of overcoming such problems are outlined. There was no reliable method of theoretically predicting pressure drop in elbow bends. Experimental measurements showed considerable scatter unless care was taken to eliminate extraneous effects. Reliable data are highlighted and an empirical method is proposed for calculation of pressure drop in elbow bends
Two- and Three-Phase Flow Through a 90 Degree Bend

Data are presented for two-phase air/water pipeflow and three-phase air/oil/water in a 0.026 m i.d. pipe and elbow bend (R/d = 0.654) for vertical to horizontal flow. The two-phase results were shown to be dependant on the flow regimes present in the system. The elbow bend acted either to smooth the transition from vertical to horizontal flow when the liquid rate was below the bubble rise velocity in the inlet leg (when negative bend pressure losses were achieved), or to generate droplets and increase the bend pressure drop substantially at higher fluid rates.Three-phase data also showed significant but not such dramatic differences, depending on the combined liquid rate being above or below the bubble rise velocity in the inlet leg. Again the variation of pressure drop for the system could be qualitatively explained by the observed flow regimes.For both two-phase and three-phase systems, the observed bend pressure drop could be correlated using a Lockhart-Martinelli approach based on the single-phase flow data for the bend
Correlation of solubility of single gases/hydrocarbons in polyethylene using PC-SAFT

The knowledge of solubility of gases and hydrocarbons in polymer has enormous importance in the design and development of reactor, polymer foaming, and membrane separation processes. In this work, the solubility of gases and hydrocarbons in polyethylene was correlated using a thermodynamic model based on perturbed-chain statistical associating fluid theory (PC-SAFT). The experimental solubility data of various gases such as ethylene, carbon dioxide, nitrogen, methane, and hydrocarbons of up to chain length of seven in both molten and semicrystalline polyethylene has been reviewed and the suitability of the developed model based on PC-SAFT was then tested using the available solubility data in literatures for various gases and hydrocarbons. Furthermore, the optimum values of adjustable solvents-solute binary interaction parameters (Kij) of PC-SAFT at different temperatures have been estimated by regression of the PC-SAFT model using experimental solubility isotherms. A suitable correlation of Kij with temperature was then developed using the estimated Kij at different temperatures. The solubility calculated from the developed model using the estimated Kij was then compared to the experimental results and a reasonably good correlation was observe
The dehydration kinetics, physical properties and nutritional content of banana textured by instantaneous controlled pressure drop

Texturing by instantaneous controlled pressure drop is used to modify texture of banana slices, which was aimed to improve properties of banana flour. Texturing step is inserted between initial and final hot air drying steps. The aim of this research is to investigate the effect of the texturing on the dehydration kinetic, physical properties and nutritional characteristic of banana. Some impacts of the texturing have been identified. The results of this work showed that the texturing increased the effective moisture diffusivity and the water holding capacity, but reduced the oil holding capacity of banana. This work also showed that the banana texturing inhibited the transformation of banana starch to reduction of sugar that might be attributable to enzyme deactivation during the texturing proces
Non-continuous and variable rate processes: Optimisation for energy use

The need to develop new and improved ways of reducing energy use and increasing energy intensity in industrial processes is currently a major issue in New Zealand. Little attention has been given to optimisation of non-continuous processes in the past, due to their complexity, yet they remain an essential and often energy intensive component of many industrial sites. Novel models based on pinch analysis that aid in minimising utility usage have been constructed here through the adaptation of proven continuous techniques. The knowledge has been integrated into a user friendly software package, and allows the optimisation of processes under variable operating rates and batch conditions. An example problem demonstrates the improvements in energy use that can be gained when using these techniques to analyse non-continuous data. A comparison with results achieved using a pseudo-continuous method show that the method described can provide simultaneous reductions in capital and operating costs
Correlation of the material properties of calcium carbonate filled polypropylene with the filler surface energies

The physical and mechanical properties of polypropylene (PP) were measured and compared with those of PP composites filled with calcium carbonate modified with sodium polyacrylate, stearic acid, or both. The variations in the mechanical properties showed a high degree of correlation with the surface energies of the fillers, as determined by inverse gas chromatography. The results confirmed the usefulness of inverse gas chromatography for characterizing the compatibility of polymer-filler combinations
Influence of Temperature on the Ultrasonic Degradation of Poly(vinyl acetate) and Poly(vinyl chloride)

This study investigates the effect of temperature on the ultrasonic degradation of polyvinyl acetate and polyvinyl chloride in chlorobenzene. The time evolution of molecular weight distribution was determined using gel permeation chromatography. Continuous distribution kinetics was used to obtain the degradation rate coefficients. The rate coefficients decrease with increasing temperature, and this is attributed to the increase of vapor pressure and the decrease of kinematic viscosity. The degradation rate coefficient also changes sharply near the glass transition temperature, indicating that this factor may play a role in the degradation process
Structural development of HDPE in injection molding

This study investigated some relevant structure/properties relationships in shear-controlled orientation in injection molding (SCORIM) of high-density polyethylene (HDPE). SCORIM was used to deliberately induce a strong anisotropic character in the HDPE microstructure. Three grades with different molecular weight characteristics were molded into tensile test bars, which were subsequently characterized in terms of the mechanical behavior by tensile tests and microhardness measurements. The structure developed upon processing was also characterized by polarized light microscopy (PLM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WAXD). SCORIM allows the production of very stiff molded parts, exhibiting a very well-defined laminated morphology. This morphology is associated with both an M-shaped microhardness profile and a pronounced mechanical anisotropy. These characteristics are supported by an analogous variation in the crystallinity and a high level of molecular orientation, as indicated, respectively, by calorimetric measurements and X-ray diffraction resultsSubprograma Ciência e Tecnologia do 2° Quadro Comunitário de Apoio, Ministério da Ciência e Tecnologia (Portugal)
Flocculation and sedimentation of cane sugar juice particles with cationic homo- and copolymers

Rapid flocculation and sedimentation of suspended particles in primary cane sugar juice is achieved using a high molecular weight anionic polymer flocculant. This work reports on efforts to enhance the performance of an anionic flocculant by the addition of cationic polymers. Homopolymers of poly(trimethylammonium ethyl methacrylate chloride) (TMAEMAC) and cationic copolymers of poly(trimethylammonium ethyl acrylate chloride) (TMAEAC) and acrylamide were synthesized and their performance, to enhance the flocculation and sedimentation of cane sugar juice particles, was evaluated by turbidity and settling rate measurements. The charge-patch mechanism best explains the performance of the homopolymers, whereas the action of the copolymers is attributed to the bridging mechanism. The results of this work indicate that the copolymers are more effective than the homopolymers to aid flocculation and sedimentation of the cane sugar juice particles, and that the best-performing polymers are those that act by the bridging mechanism. Addition of increased amounts of anionic flocculant did not confer an improvement, suggesting that the cationic bridging flocculant targets a different population of particles that is largely responsible for the residual turbidity
Effect of purified trichoderma reesei cellulases on formation of cotton powder from cotton fabric

The mode of action of monocomponent purified
Trichoderma reesei cellobiohydrolases (CBHI and CBHII)
and endoglucanases (EGI and EGII) on cotton fabrics
was studied by analyzing the weight loss of the fabric, the
reducing sugars, the soluble oligosaccharides and the molecular
weight of the cotton powder formed. The impact of
mechanical action on these factors was also evaluated. EGI
and EGII released the highest amounts of reducing sugars
and soluble oligosaccharides in both treatments with or
without additional mechanical action. After cellulase treatment
without additional mechanical action, all of the cellulases were found to have reduced the molecular weight of
cotton poplin powder. When mechanical action was combined
with enzyme treatments, only EGII reduced the molecular
weight. The weight loss of EG-treated fabrics was
clearly higher than the weight loss of CBH-treated fabrics
with both low and high mechanical action levels
Water and water vapor sorption studies in polypropylene-zeolite composites

Water and water vapor sorption to porous polypropylene-zeolite composites prepared by hot pressing have been studied as a function of zeolite loading. This work presents the first report on the effect of the zeolite as a filler on the water-sorption properties of PP composites. Water swelling experiments were conducted at 25°C using pure PP and PP-zeolite films samples having different zeolite loadings (6-40 wt %). Because PP is a hydrophobic polymer, it does not sorp any water, but the composites having 10, 20, 30, and 40% zeolites have sorbed 0.63, 1.00, 1.72 and 3.74% water, respectively. The zeolite itself at the same conditions sorbed 24.5% water. As the filler loading in the composites increased, equilibrium uptake values increased also. On the other hand, water vapor sorption and kinetics has been studied using a Cahn 2000 gravimetric sorption system. Within in the range of 0.35-0.95% water vapor was adsorbed by the composites containing 10-40 wt % zeolites. Experimental effective water vapor diffusivities of the composite films was about one order of magnitude higher (10-fold) than the experimental water diffusion coefficient in composites. The transport of water in composites was slower than that in the liquid water due to the longer diffusion pathway and adsorption on the surface of the composites. Although the liquid water may fill all the voids in the composite, water vapor is adsorbed on the surface of the zeolite only
Inhibition of calcium oxalate monohydrate by poly(acrylic acid)s with different end groups

Water-soluble low molecular weight polymers are known to affect the crystal habit of scale-forming minerals and their rates of deposition. Poly(acrylic acid) (PAA) and poly(maleic acid) are commonly used to control scale formation in sugar mill evaporators. Calcium oxalate (both mono- and dihydrate) forms the bulk of the hard intractable scale found in Australian sugar mills, causing efficiency losses of significant economic importance. In this work, the formation of calcium oxalate monohydrate in a synthetic juice solution was investigated in the presence of PAAs of varying molecular weights and end-group functionality and a strong dependency on both of these factors was observed. Terminal functionality was controlled using three chain-transfer agents (CTA): thioethanol, thioglycolic acid, and dodecanthiol. Effectiveness of inhibition varied with CTA in the order thioethanol  thioglycolic acid > dodecanthiol for all molecular weights. This suggests that polymer end groups play a role in scale inhibition. The polymers that were prepared with dodecanthiol accelerated rather than inhibited calcium oxalate formation, implying a different mode of action on calcium oxalate crystallization. Consistent with previous reports for other scales, the calcium oxalate inhibition tests show optimum effectiveness for PAAs of molecular weight 2000-4000
Numerical modeling of the dynamic tensile behavior of irregular fibers

Most fibers are irregular, and they are often subjected to rapid straining during mechanical processing and end-use applications. In this paper, the effect of fiber dimensional irregularities on the dynamic tensile behavior of irregular fibers is examined, using the finite element method (FEM). Fiber dimensional irregularities are simulated with sine waves of different magnitude (10%, 30% and 50% level of diameter variation). The tensile behavior of irregular fibers is examined at different strain rates (333%/sec, 3,333%/sec and 30,000%/sec). The breaking load and breaking extension of irregular fibers at different strain rates are then calculated from the finite element model. The results indicate that strain rate has a significant effect on the dynamic tensile behavior of an irregular fiber, and that the position of the thinnest segment along the fiber affects the simulation results markedly. Under dynamic conditions, an irregular fiber does not necessarily break at the thinnest segment, which is different from the quasi-static results.<br /
Biodegradation of gelatin-g-Poly(ethyl Acrylate) copolymers

Gelatin-g-poly(ethy1 acrylate) copolymers were prepared in an aqueous medium, using $K_{2}S_{2}0_{8}$ initiator. The composition of the graft copolymers was dependent upon temperature and duration of the reaction. The number of grafting sites was small and molecular weight of the grafted poly(ethy1 acrylate) branches was high. Three copolymer samples with grafting efficiencies of 33.3% 61.0%, and 84.0%, were tested for their microbial susceptibility in a synthetic medium employing a mixed inoculum of Bacillus subtilis, Pseudomonas aeruginosa, and Serratia marcexens and the percent weight losses were 12%, 10.1%, and 6.0%. respectively, after 6 weeks of incubation. The extent of degradation seems to decrease with increasing grafting efficiency. There was initial rapid weight loss accompanied by the exponential increase in bacterial population and pH of the culture medium during the first week. The nitrogen analysis also showed the utilization of the polymer. A parallel set of experiments, carried out by employing the samples as the only source of both carbon and nitrogen, showed a marginal but definite increase in the utilization of the polymer
Transition metal chelates as accelerators for epoxy resin systems—studies with cobalt (III) acetylacetonate

Cobalt(III)acetylacetonate serves as an accelerator for anhydride curable epoxy resin system and the rate of curing is found to increase with enhanced concentrations of the metal chelate. There is also an appreciable reduction in the cure gel time. Kinetic studies based on thermal analytical techniques reveal that the overall curing process follows first order kinetics. Based on the kinetic results a cure schedule has been proposed. It is also observed that the electrical, mechanical, and thermal properties of the cured epoxy system are not altered by the presence of the metal chelate at the concentration studied