Continuous Mixing Research Articles

Chemical Oxygen Demand Analysis of Anaerobic Digester Contents

An anaerobic digester converts organic materials into biogas and digestate in the absence of oxygen. The organic materials studied in this experiment include fibres (types of paper or cardboard), food waste, and woodchips, which serve as a bulking agent. To analyze digester performance, it is necessary to calculate an accurate mass balance based on the chemical oxygen demand (COD) entering and exiting the system. Digester performance refers to maximum efficiency and biogas yield. The COD of the biogas is known, but that of the feed and the digestate is not. This paper describes a method for measuring the COD of the feed materials and the digestate by creating representative aqueous suspensions of each. The challenges are to ensure that the suspensions are representative of the feed or digestate, and that samples of the suspension extracted for COD analysis are consistent and reproducible. To obtain an accurate COD measurement of the feed and digestate samples, a specific procedure was developed: each material was processed in a blender with deionized water, creating a pulp from which samples were pipetted during continuous mixing of the suspension. The conducted trials provided COD content values ranging from 1.27-1.59 g of COD/ g of dry feed, depending on the fibre. Standard deviations of the COD content ranged from 2.8% to 12.7%, indicating that the procedure is reliable and the results precise. The measured COD content values allow an accurate mass balance of the digester to be determined, ultimately providing a better understanding of the system as the total digestible material entering the digester will be known. An accurate mass balance can improve the efficiency of the digester in order to produce optimal quantities of biogas. The biogas can be harnessed into energy from otherwise useless waste. Further study in this topic can explore the COD content of wider ranges of organic solids as well as further optimize the procedure in order to provide even more accurate results.

Features of the mixing of water and ethanol under alternating pressure pulses

Analytical studies of ways of mixing water and ethanol are conducted. Energy-saving method is proposed for the continuous mixing of water and ethanol under alternating pressure pulses. Rational thermophysical modes of the continuous process of mixing water and ethanol under alternating pressure pulses are chosen. The study of physical and chemical properties of the resulting mixtures is conducted. These results demonstrate the feasibility of using the power saving mode continuous mixing of water and ethanol in the conditions of alternating pressure pulses for food pharmaceutical and cosmetic industries. Based on experimental studies, numerical experiments and field tests proposed rational technological modes of carrying out continuous mixing of water and ethanol in the conditions of alternating pressure pulses. When using the technology of production for water-ethanol mixtures in conditions of alternating pressure pulse is intense impact stress shear, shear flow, a high-frequency oscillation, which leads to reduction of quantity of harmful impurities.

On-chip recalcification of citrated whole blood using a microfluidic herringbone mixer.

In vitro assays of platelet function and coagulation are typically performed in the presence of an anticoagulant. The divalent cation chelator sodium citrate is among the most common because its effect on coagulation is reversible upon reintroduction of divalent cations. Adding divalent cations into citrated blood by batch mixing leads to platelet activation and initiation of coagulation after several minutes, thus limiting the time blood can be used before spontaneously clotting. In this work, we describe a herringbone microfluidic mixer to continuously introduce divalent cations into citrated blood. The mixing ratio, defined as the ratio of the volumetric flow rates of citrated blood and recalcification buffer, can be adjusted by changing the relative inlet pressures of these two solutions. This feature is useful in whole blood assays in order to account for differences in hematocrit, and thus viscosity. The recalcification process in the herringbone mixer does not activate platelets. The advantage of this continuous mixing approach is demonstrated in microfluidic vascular injury model in which platelets and fibrin accumulate on a collagen-tissue factor surface under flow. Continuous recalcification with the herringbone mixer allowed for flow assay times of up to 30 min, more than three times longer than the time achieved by batch recalcification. This continuous mixer allows for measurements of thrombus formation, remodeling, and fibrinolysis in vitro over time scales that are relevant to these physiological processes.

Continuous manufacturing of extended release tablets via powder mixing and direct compression

The aim of the current work was to explore continuous dry powder mixing and direct compression for manufacturing of extended release (ER) matrix tablets. The study was span out with a challenging formulation design comprising ibuprofen compositions with varying particle size and a relatively low amount of the matrix former hydroxypropyl methylcellulose (HPMC). Standard grade HPMC (CR) was compared to a recently developed direct compressible grade (DC2). The work demonstrate that ER tablets with desired quality attributes could be manufactured via integrated continuous mixing and direct compression. The most robust tablet quality (weight, assay, tensile strength) was obtained using high mixer speed and large particle size ibuprofen and HPMC DC2 due to good powder flow. At low mixer speed it was more difficult to achieve high quality low dose tablets. Notably, with HPMC DC2 the processing conditions had a significant effect on drug release. Longer processing time and/or faster mixer speed was needed to achieve robust release with compositions containing DC2 compared with those containing CR. This work confirms the importance of balancing process parameters and material properties to find consistent product quality. Also, adaptive control is proven a pivotal means for control of continuous manufacturing systems.

Magnetoelectric properties in bulk and layered composites

Purpose – The purpose of the paper was to present a comparative study on the microstructure and magnetoelectric effect of new magnetoelectric composites based on TbFe2 compound and Ni0.3Zn0.62Cu0.08Fe2O4, CoFe2O4 ferrites as a magnetostrictive phase, Pb(Fe1/2Ta1/2)O3 (PFT), Pb(Fe1/2Nb1/2)O3 relaxors as a ferroelectric phase and polyvinylidene fluoride (PVDF) as piezoelectric phase. Design/methodology/approach – The ceramic components of composites were prepared by the standard solid-state reaction method. The intermetallic compound TbFe2 was prepared with an arc melting system with a contact-less ignition in a high purity argon atmosphere. The metal – ceramic – polymer composites were prepared in a container in which powder of PVDF were dissolved in N,N-dimethylformamide with continuous mixing and at the controlled temperature. Ceramic composites were prepared as bulk samples and multilayer tape cast and co-sintered laminates. The microstructure of the composites was investigated using scanning electron microscopy (SEM). The magnetoelectric effect of the composites was evaluated at room temperature by means of the dynamic lock-in method. Findings – SEM analysis revealed a dense, fine-grained microstructure and uniform distribution of the metallic, ferrite and relaxor grains in the bulk composites. The SEM image for multilayer composite illustrates the lack of cracks or delaminations at the phase boundaries between the well-sintered ferrite and relaxor layers. For all studied composites, the magnetoelectric coefficients at a lower magnetic field increase, reaches a maximum and then decreases. Originality/value – The progress in electronic technology is directly linked to advances made in materials science. Exploring and characterizing new materials with interesting magnetoelectric properties, in the rapidly growing field of functional materials, is an important task. The paper reports on processing, microstructure and magnetoelectric properties of novel magnetoelectric composites.

Limnological and ecological methods: approaches, and sampling strategies for middle Xingu River in the area of influence of future Belo Monte Power Plant.

In this paper the authors describe the limnological approaches, the sampling methodology, and strategy adopted in the study of the Xingu River in the area of influence of future Belo Monte Power Plant. The river ecosystems are characterized by unidirectional current, highly variable in time depending on the climatic situation the drainage pattern an hydrological cycle. Continuous vertical mixing with currents and turbulence, are characteristic of these ecosystems. All these basic mechanisms were taken into consideration in the sampling strategy and field work carried out in the Xingu River Basin, upstream and downstream the future Belo Monte Power Plant Units.

Theoretical analysis of fluid mixing time in liquid-continuous impinging streams reactor

The mixing time of impact zone in liquid-continuous impinging streams reactor (LISR) is theoretically calculated by empirical model and modern micromixing model of the fluid mixing process, and the variation laws of macromixing time and micromixing time are quantitatively discussed. The results show that under a continuous and stable operating condition, as the paddle speed increases, the macromixing time and micromixing time calculated by the two models both decrease, even in a linkage equilibrium state. Simultaneously, as the paddle speed increases, the results figured by the two models tend to be consistent. It indicates that two models both are more suitable for calculation of mixing time in high paddle speed. Compared with the existing experimental results of this type of reactor, the mixing time computed in the speed of 1500 r/min is closer to it. These conclusions can provide an important reference for systematically studying the strengthening mechanism of LISR under continuous mixing conditions.

Production of water-soluble quercetin formulations by antisolvent precipitation and supercritical drying

Quercetin is one of the most prominent dietary antioxidants. The application of quercetin in food, cosmetic and pharmaceutical industries due to its properties, requires an adequate formulation in order to provide protection against degradation, to increase the solubility in aqueous systems and to improve the bioavailability. This work presents a study of the encapsulation of quercetin in water-soluble carriers by antisolvent precipitation using three different techniques: shear mixing, continuous flow turbulent mixing at atmospheric pressure and ambient temperature and turbulent mixing at high pressure and high temperature. A preliminary study of quercetin formulation by shear mixing showed that modified OSA-starch and Pluronic L-64 were not good carrier materials due to the low encapsulation efficiencies and high particle sizes obtained. However, using lecithin as carrier material, it was possible to obtain stable and homogeneous aqueous dispersions of quercetin particles with encapsulation efficiencies up to 90%. By supercritical drying, spherical particles with particle sizes in the range of 10μm were obtained that could be used to reconstitute the aqueous suspension, maintaining the encapsulation efficiency of quercetin.

ACTIVE BIOPACKAGING FROM DAMMAR FOR COMMINUTED MEAT PRESERVATION

This research aimed to develop biopackaging materials using thermoplastic starch matrix and Indonesian dammar extracts possessing antimicrobial activity, i.e. flesh dammar (Shorea leprosula) and stone dammar (S. eximia), for preserving comminuted meat. The packaging matrix was prepared using continuous melt mixing of tapioca starch and glycerol in a co-rotating twin extruder. Subsequently, the matrix was dipped in dammar extracts, with or without the addition of antimicrobial agents such as propyl paraben, zinc chloride, zinc acetate, and silver nitrate. As a result, flesh dammar performed greater antibacterial activity than that of stone dammar. Moreover, the antibacterial activity of silver nitrate in the biopackaging was comparable to that of zinc chloride while combined with dammar, but zinc acetate was less effective. On the other hand, active biopackaging comprised of combination of dammar and propyl paraben was the least effective. Among the eight combinations of two dammar extracts and four antimicrobial agents, flesh dammar extract comprised of 0.1% (w/v) zinc chloride and 1.0% (w/v) lecithin was found as the most promising formulation for dipping with regard to its production cost and antimicrobial activity. Total plate count (TPC) in comminuted meat wrapped with active biopackaging (initial microbial load of 5.2 ± 0.1 × 104 CFU/g) decreased to 2.8 ± 0.1 × 104 CFU/g over 9 days of storage at 40°C temperature. This number was lower than TPC value of nitrate-preserved meat (3.4 ± 0.2 × 104 CFU/g and 5.9 ± 0.4 × 105 CFU/g, respectively).

English

The influence of mixing H2/CO2 gas recirculation on the performance of hydrogenotrophic methanogens activity in continuous culture was studied at 37 and 20°C. Chemostat fermentation was used at laboratory scale to determine the bioconversion rate of H2/CO2 mixture gas to methane under different mixing rates. On comparison with continuous mixing, intermittent mixing at 45 min/h provided a better methane production, 1.94 ± 0.06 versus 1.83 ± 0.05 L for continuous mixing. When the temperature was progressively decreased to 20°C, the same configuration was observed. The methane production was lowered from 76.2, 80.8, 67.5, 61.2 to 27.9, 35.8, 29.6 and 26.7% for 60, 45, 30 and 15 min/h, respectively. The mixing at 45 min/h showed a stable methane production as compared to all proposed mixing duration especially at psychrophilic temperature. The results would facilitate an empiric model that could help to establish more economical biogas reactor model. Key words: Hydrogenotrophic methanogens, mixing, H2/CO2 gas, bioconversion, temperature fluctuation.

$$n$$ n -Step cycle inequalities: facets for continuous multi-mixing set and strong cuts for multi-module capacitated lot-sizing problem

In this paper, we introduce a generalization of the continuous mixing set, which we refer to as the continuous multi-mixing set. This set is closely related to the feasible set of the multi-module capacitated lot-sizing (MML) problem with(out) backlogging. We present a family of valid inequalities for the continuous multi-mixing set and identify conditions under which they are facet-defining. The cycle inequalities, $$n$$n-step MIR inequalities, and mixed $$n$$n-step MIR inequalities are special cases of these inequalities. We also present an exact separation algorithm for our inequalities. We then use these inequalities to generate valid inequalities for MML with(out) backlogging. Our computational results show that our cuts are very effective in solving the MML instances, resulting in substantial reduction in the integrality gap, number of nodes, and total solution time.

Optimization of Parameters Dry Construction Mixtures in the Horizontal Drum Mixer

In the article the process of continuous mixing of dry construction mixtures and developed an experimental mathematical model of horizontal drum mixer. It is noted that the qualitative analysis of the structure of the mixing process should take into account semantic and mathematical description of the mixing process of building materials in the horizontal continuous mixer drum. On the basis of the developed mathematical model simulation work performed horizontal drum mixer software environment AnyLogic.

Optimization of process parameters mixing dry construction mixtures in the horizontal drum mixer continuous simulation method

In the article the process of continuous mixing of dry construction mixtures and developed an experimental mathematical model of horizontal drum mixer. It is noted that the qualitative analysis of the structure of the mixing process should take into account semantic and mathematical description of the mixing process of building materials in the horizontal continuous mixer drum. On the basis of the developed mathematical model simulation work performed horizontal drum mixer software environment AnyLogic.

Design and Development of Liquisolid Compact of Carvedilol

It is suggested here that liquisolid technique has the potential to be optimized for the reduction of drug dissolution rate and thereby production of sustained release systems is possible. In the present study, carvedilol was dispersed in polyethylene glycol 400 as the liquid vehicle. Then a binary mixture of carrier-coating materials ((Avicel PH-102) as the carrier and silica 200 as the coating material) was added to the liquid medication under continuous mixing in a mortar. The final mixture was compressed using the tablet compression machine. The effect of drug concentration, loading factor, thermal treating and on release profile of carvedilol from liquisolid compacts were investigated. The release rate of carvedilol from liquisolid compacts was compared to the release of carvedilol from matrix tablets. X-ray crystallography and DSC were used to investigate the formation of any complex between drug and excipients or any crystallinity changes during the manufacturing process. carvedilol tablets prepared by liquisolid technique showed greater retardation properties in comparison with matrix tablets. This investigation provided evidence that (HPMC) hydroxypropyl methylcellulose has important role in sustaining the release of drug from liquisolid tablets. The results also showed that wet granulation had remarkable impact on release rate of carvedilol from liquisolid compacts, reducing the release rate of drug from liquisolid compacts. The results showed that aging (liquisolid tablets were kept at 400C and 75% relative humidity for 3 months) had no effect on hardness and dissolution profile of drug. The kinetics studies revealed that most of the liquisolid formulations followed the zero-order release pattern. Infrared spectroscopy and DSC ruled out any changes in crystallinity or complex formation during the manufacturing process of liquisolid formulations.

The N-terminal SH2 domain of Syk is required for (hem)ITAM, but not integrin, signaling in mouse platelets

AbstractWe have used a novel knockin mouse to investigate the effect of disruption of phosphotyrosine binding of the N-terminal SH2 domain of Syk on platelet activation by GPVI, CLEC-2, and integrin αIIbβ3. The SykR41Afl/fl mouse was crossed to a PF4-Cre+ mouse to induce expression of the Syk mutant in the megakaryocyte/platelet lineage. SykR41Afl/fl;PF4-Cre mice are born at approximately 50% of the expected frequency and have a similar phenotype to Sykfl/fl;PF4-Cre mice, including blood-lymphatic mixing and chyloascites. Anastomosis of the venous and lymphatic vasculatures can be seen in the mesenteric circulation accounting for rapid and continuous mixing of the 2 vasculatures. Platelet activation by CLEC-2 and GPVI is abolished in SykR41Afl/fl;PF4-Cre platelets. Syk phosphorylation on Tyr519/20 is blocked in CLEC-2–stimulated platelets, suggesting a model in which binding of Syk via its N-terminal SH2 domain regulates autophosphorylation. In contrast, outside-in signaling by integrin αIIbβ3 is not altered, but it is inhibited in the presence of inhibitors of Src and Syk tyrosine kinases. These results demonstrate that αIIbβ3 regulates Syk through an ITAM-independent pathway in mice and provide novel insight into the course of events underlying Syk activation and hemITAM phosphorylation by CLEC-2.

The Recent Nesting Record of Female Green Turtle, <i>Chelonia mydas</i>,<i> </i> at Pamban, Gulf of Mannar

A female green turtle was sighted at Pamban along the Gulf of Mannar just after the nesting on the beach on 15th January 2011. Morphometric measurements of the turtle were taken and data suggests that this individual is adult. A total number of laid eggs were 109. The distance between the nesting site and the high tide line was found to be 7 m. The depth and diameter of the nesting pit was 52 and 16 cm, whereas the mean egg diameter and weight were found to be 44.3 mm and 40.5 g respectively. Pamban coast may also be considered an important place for nesting, because of the continuous mixing of waters of GOM and Palk Bay areas, which in turn create current patterns continuously throughout the year in addition to the monsoon season. Conservation of nesting habitat along Gulf of Mannar will be important to maintain the green turtle population.

The Recent Nesting Record of Female Green Turtle, <i>Chelonia mydas</i>,<i> </i> at Pamban, Gulf of Mannar

A female green turtle was sighted at Pamban along the Gulf of Mannar just after the nesting on the beach on 15th January 2011. Morphometric measurements of the turtle were taken and data suggests that this individual is adult. A total number of laid eggs were 109. The distance between the nesting site and the high tide line was found to be 7 m. The depth and diameter of the nesting pit was 52 and 16 cm, whereas the mean egg diameter and weight were found to be 44.3 mm and 40.5 g respectively. Pamban coast may also be considered an important place for nesting, because of the continuous mixing of waters of GOM and Palk Bay areas, which in turn create current patterns continuously throughout the year in addition to the monsoon season. Conservation of nesting habitat along Gulf of Mannar will be important to maintain the green turtle population.

Pilot-scale evaluation of an in situ amendment delivery and mixing device for contaminated sediment remediation applications

In situ sediment treatment technologies can be more economical alternatives than dredging and ex situ treatment; however, their development and application had been hindered due to uncertainties associated with the homogeneity of amendment delivery and mixing and the concern of contaminated sediment resuspension and amendment release into the water column. The purpose of this study was to evaluate the subaqueous amendment delivery and mixing efficiency of a novel pilot scale in situ sediment remediation system addressing these concerns. The in situ sediment treatment system consisted of a hydraulically operated steel casing that provided contained conditions for amendment delivery and mixing to occur and the mixing tool housed by this casing. The mixing tool consisted of a hollow vertical shaft with horizontal mixing blades. The device was capable of delivering amendments to subaqueous sediments during continuous mixing in the downward or upward vertical direction. Activated carbon was used as a tracer to evaluate the efficiency of reagent delivery and mixing. The delivery and mixing system operation was defined by the following parameters: mixing speed, vertical descent or ascent speed, mixing time, total processing time, sediment mixing depth, activated carbon slurry injection volume, pumping flow rate for activated carbon, and pumping pressure for activated carbon. Better amendment yield recoveries were observed at lower added activated carbon volumes, at higher mixing speeds, at lower pump flow rates, in case of thicker mixed sediment zones, and at horizontal locations closer to the center shaft. In general, poor amendment recoveries could be attributed to the limited capacity of the sediment pore space to accommodate the activated carbon slurry. Better recoveries close to the shaft might have occurred due to the fact that the amendment delivery pressure was not controlled and therefore was not constant through each reagent delivery port. The reagent stayed within the enclosure of the device, indicating that contained mixing conditions were achieved. The majority of the suspended sediment settled out fairly quickly from the overlying water column within the enclosure. The in situ remediation system showed potential in terms of successful amendment delivery and mixing into subaqueous sediments. Lower doses of activated carbon were mixed in more efficiently due to the limited availability of pore capacity and issues with powdered activated carbon retention in the sediment. The demonstration took place in sediments with large sand and gravel fractions; sediments containing larger silt and clay fractions are likely to behave differently in terms of sediment resuspension.

Theoretical Study of Optimal Positioning of Segregating Component Input into Continuous Mixer of Solids

The objective of the study is to demonstrate theoretically one of the ways of improving the quality of continuous mixing of segregating particulate solids. The objective function of optimization is the standard deviation of segregating component distribution over the mixer's cross-section at the mixer outlet, the optimization parameter being the position of segregating component input. It is shown that the input of the component into the position that is optimized over the length of the mixer allows improving the mixing quality. The gain of optimization depends on the rate of segregation and grows with its increase.

Rate-Distortion Bounds for Wyner–Ziv Coding With Gaussian Scale Mixture Correlation Noise

The objective of this work is the characterization of the Wyner-Ziv rate-distortion function for memoryless continuous sources, when the correlation between the sources is modeled via an additive noise channel. Modeling the distribution of the correlation noise via a Gaussian mixture, with discrete or continuous mixing variable, provides a unified signal model able to describe a wide class of distributions, useful in the context of practical applications. The Wyner-Ziv rate-distortion function associated with this signal model cannot, in general, be obtained in analytical form. This work contributes a method for its analysis, by providing computable upper and lower bounds.