Mixing Elements Research Articles

Growing dendrites enhance a neuron’s computational power and memory capacity

Neocortical pyramidal neurons have many dendrites, and such dendrites are capable of, in isolation of one-another, generating a neuronal spike. It is also now understood that there is a large amount of dendritic growth during the first years of a humans life, arguably a period of prodigious learning. These observations inspire the construction of a local, stochastic algorithm based on an earlier stochastic, homeostatic, Hebbian developmental theory. Here we investigate the neurocomputational advantages and limits on this novel algorithm that combines dendritogenesis with supervised adaptive synaptogenesis. Neurons created with this algorithm have enhanced memory capacity, can avoid catastrophic interference (forgetting), and have the ability to unmix mixture distributions. In particular, individual dendrites develop within each class, in an unsupervised manner, to become feature-clusters that correspond to the mixing elements of class-conditional mixture distribution. Error-free classification is demonstrated with input perturbations up to 40%. Although discriminative problems are used to understand the capabilities of the stochastic algorithm and the neuronal connectivity it produces, the algorithm is in the generative class, it thus seems ideal for decisions that require generalization, i.e., extrapolation beyond previous learning.

A Letter from Algerian Rabbi David Askénazi to Rabbi Kook Advocating for the Use of the Organ in Synagogue Services

Abstract In 1934, David Askénazi, the chief rabbi of Oran, Algeria, responded to a decision by Abraham Kook, at the time chief rabbi of Mandatory Palestine, condemning the use of the organ in synagogue services in Oran. Transcending the typical European dichotomies between Orthodox and Reform, Askénazi’s letter is above all a testimony to the religious and cultural hybridity of Algerian Jews during the colonial era. In a mere few pages, the rabbi developed a religious argument mixing elements of language and arguments typical of Maghrebian rabbis with positions common to liberal European Jews. Aware of the structure of power between the East and the West, Askénazi also criticized Kook’s interventionism in the affairs of his community. In light of what he denounced as a form of Jewish imperialism, Askénazi emphasized the agency of Sephardic rabbis and called for full recognition of their religious tradition.

Enhancement investigation of mass transfer and mixing performance in the static mixers with three twisted leaves

Abstract The mass transfer and mixing performance in the static mixers with three twisted leaves (TKSM) were investigated by the computational fluid dynamics coupled population balance model. A high-precision and efficient gas-liquid two phase model were evaluated by considering several drag models based on experimental bubble size distributions. The bubble size prediction matched well with experimental data and the mean relative error of Sauter mean diameter (d 32) between the prediction and experiment values is 4.93 %. The drag correction factor considering hindering effect of small bubbles can improve the accuracy of cumulative probability distribution (CPD) prediction by 10.06 %. Bubble breakup capacity is quantized via gas-liquid interfacial area, and an empirical correlation between Eo and bubble aspect ratio (γ) have been proposed to predict morphological characteristics of bubble swarms. The effect of liquid Re on the mass transfer rate is much more significant than that of gas volume fraction (α d). The coefficients of variation profiles show that RL-TKSM has better mixing efficiency compared with LL-TKSM and perfect mixing could be achieved after seven mixing elements. The micro mixing efficiency of RL-TKSM is 1.06–1.14 times that of LL-TKSM, which indicates that RL-TKSM has excellent mixing and mass transfer performances.

Twin-screw continuous mixing: Effect of mixing elements and processing parameters on properties of aerosol powders

Twin-screw continuous mixing was used to prepare aerosol powders containing 1% budesonide, 0.3% magnesium stearate, and 98.7% α-lactose monohydrate. The effect of mixing configuration was studied using three screw profiles containing either a combing element, 30° forward kneading element, or a 60° forward kneading element. The impact of screw speed, feed rate, and multiple passes through the mixer on powder quality was investigated. The impact of specific energy on aerosol performance was dependent on the mixing configuration, and high energy input was detrimental to FPF for the 30° kneading element. Control of content uniformity was demonstrated by varying the mixing element in the screw profile. Passing the material through the mixer multiple times improved the aerosol performance. The robust and tunable nature of twin-screw mixing makes it a process well suited for continuous manufacturing of aerosol powders.

Comparative analysis of the working bodies of the vibrating mixer of bulk feed

BACKGROUND: The paper is devoted to the preparation of highly homogeneous bulk feed mixtures. It is known that the efficiency of the mixing process increases significantly when vibra-tion is applied, while reducing the time to achieve maximum uniformity of the mixture and reduc-ing the energy costs of mixing. In some cases, vibration can only intensify the main process, and in others it can cause specific vibration effects that are used for mixing.
 AIMS: Increasing the homogeneity of the mixture due to vibration effects.
 METHODS: A laboratory-experimental vibrating mixer of continuous bulk feed has been de-veloped for conducting research. Its general structure and principle of operation are considered, the influence of design features of replaceable working bodies on the quality of the mixing pro-cess is analyzed.
 RESULTS: Comparative analysis has shown that mixing elements with complex vibration con-tact surfaces provide a sufficiently high quality of the resulting mixture, but the mixer perfor-mance is relatively low. To increase productivity while maintaining consistently high quality, flat working bodies with holes in the form of isosceles triangles are proposed. During the studies of their work, a decrease in the uniformity of the resulting mixture was revealed, therefore, it is pro-posed to install concave or curved triangular plates under the holes. This technical solution allows us to obtain the quality of the feed mixture that meets the requirements without reducing produc-tivity.
 An additional way to intensify the mixing process, regardless of the type of working bodies, is the hinge fastening of the mixing elements. In addition, using a special mechanism, it is possi-ble to change the speed of mass movement inside the vibrating trough and, accordingly, the per-formance of the entire installation as a whole and the mixing intensity.
 CONCLUSIONS: All types of mixing elements have been successfully tested. The laboratory-experimental vibrating mixer has passed the production test as part of a small-sized feed unit.
 The article describes the history of the development and creation of the first domestic neutralizers of exhaust gases of internal combustion engines, which began with testing and research of foreign neutralizers. Sequential stages of design, study and testing of domestic converters for gasoline and diesel engines are considered. There are described the following processes: the process of developing methods for testing engines for toxicity and the process of creating estimated indicators and developing normative and technical documents in the field of toxicity of engines and vehicles.

Tailoring flow behavior and heat transfer in tempering channels for high-pressure die casting—analysis of potentials of commercial static mixers and prospects of additive manufacturing

Additive manufacturing (AM) opens up manifold possibilities to influence the heat transfer between fluid and die in high-pressure die casting (HPDC), eventually allowing to minimize the total cycle time of the process. AM already has been exploited to establish near-contour temperature control systems in industrial applications. However, AM not only allows to influence the position of tempering channels in dies but it also allows to influence the fluid dynamics itself, e.g., by imprinted static mixers. Up to now, such flow-influencing mixing elements have not been considered in metal AM. In the present work, the impact of such metallic static mixers and most relevant processing conditions is investigated experimentally as well by computational fluid dynamics (CFD) simulation. In a first step, conventional static mixer elements are integrated into straight tempering channels to stimulate turbulences of the flowing tempering medium, finally resulting in an increase of the heat transfer up to 33%. In a second step, laser-based powder bed fusion of metals (PBF-LB/M) is applied to realize static mixers. Results obtained reveal that tempering channels without negative influences on the general flow behavior compared to conventional static mixers in straight tempering channels can be realized. In conclusion, the presented results show a positive impact on heat transfer and, thus, allow to further increase the economic efficiency of the HPDC process.

Geometry optimization of a continuous millireactor via CFD and Bayesian optimization

Computational Fluid Dynamics (CFD) is a powerful tool which can help with the geometry optimization of continuous milli-scale reactors, which often are highly complex devices. Attempting to perform this optimization by manually modifying and testing geometry configurations can however be tedious and computationally inefficient. Addressing this problem, we present a framework in which the CFD software COMSOL Multiphysics is coupled with the multi-objective Bayesian Optimization algorithm TSEMO (Thompson sampling efficient multiobjective optimization), implemented in MATLAB. The mixing element geometry of a Miprowa Lab millireactor is parameterized, and the framework automatically executes CFD simulations to minimize areas of stagnating flow and maximize the mixing performance. The framework is able to find Pareto-optimal reactor variations, and can easily be adapted for other devices and objectives.

An improved correlation for dry pressure losses across static mixers at high Reynolds numbers

AbstractCorrugated (SMV‐style) static mixers are industrially important for process intensification and can promote gas–liquid mass transfer in processes such as sour gas sweetening. Current correlations for pressure loss are limited to Reynolds numbers (Re) below 40 000, far below the ranges encountered in natural gas systems (105 < Re < 107). An experimental and numerical study of pressure drop across multiple corrugated mixers in the range of 104 < Re <2 × 105 encompassing different configurations (aligned, rotated), pipe diameters (1–4 in.), and sand grain surface roughness values (10–5000 μm) is reported here. Our previous correlation for pressure loss across a single corrugated element is shown to be extendable to multiple corrugated mixing elements. Through the inclusion of mixer tortuosity (τ), porosity (ε), and macro‐scale (geometric) wall roughness (e), the correlation also matches historical pressure drop data (at different τ, ε) reported in literature, thereby demonstrating the utility of these variables as parameters that can help optimize mixer performance. Experiments and computational fluid dynamics (CFD) modelling revealed that the rotated configuration increased the residence time by up to 13% in comparison to the aligned configuration. This may have implications on the selective absorption of sour gas components that are based on fast kinetics. In addition, the role of wall roughness (both pipe housing and mixer) was demonstrated to be significant in this study (accounting for 55% of the pressure losses) and must be accurately accounted for when scaling laboratory measurements.

High-Entropy Alloys FeCoNiCuX (X = Al, Mo)-Ce0.8Sm0.2O2 as High-Performance Solid Oxide Fuel Cell Anodes

High-entropy alloys (HEAs) have received a lot of attention in electrocatalysis due to their potent synergistic effects of uniformly mixing many elements. In this study, HEAs FeCoNiCuX (X = Al, Mo)-Ce0.8Sm0.2O2 (SDC) are considered as a prospective intermediate temperature solid oxide fuel cell (SOFC) anode. FeCoNiCuX-SDC as a SOFC anode shows comparable high conductivity with a Ni-based anode and exhibits outstanding catalytic capability for H2, CH4, and CO2. The LSGM electrolyte-supported single cell with FeCoNiCuAl-SDC as anode shows maximum power densities of 779 and 526 mW cm–2 with H2 and CH4 as fuel gases and testing at 850 °C, respectively. The distribution of relaxation time analysis shows that the prime speed-limiting steps for the FeCoNiCuX-SDC anode are the adsorption/dissociation of fuel gas. X-ray photoelectron spectroscopy results showed that FeCoNiCuX HEAs with the main constituents in different valence states created more active sites, which provided a synergistic effect for H2, CH4, and CO2 catalysis.

Rosalía as Resource: Pedagogical Synergies

Abstract: Rosalía is an expert at borrowing and mixing elements from various time periods and places, resulting in a fusion of aesthetic styles, along with literary and cultural references. While her work is sometimes criticized for cultural appropriation, we might take another look at it to reframe Rosalía's ethos as one that is part and parcel of a generation that embraces multimedia. This note asks, then, what can we, as scholars and professors, adopt from her work for teaching purposes? The creative synergies she exemplifies as well as her own star persona encourage us to think more expansively about how to enlarge our pedagogical repertoire. Rosalía's creative output may be utilized to enhance our pedagogy by making literary texts more accessible to students, to make historical connections throughout different periods, and to teach about relevant topics, which is ultimately exemplified with an illustration of how I drew upon Rosalía's work in a 2021 undergraduate seminar I designed about fashioning women in modern Spain.

Effects of static mixers on continuous methyl ester production: comparing four types of 3D-printed mixing elements

Four types of 3D-printed static mixer were employed in the continuous transesterification process to examine the pressure drop and mixing intensity. Methanol, KOH, and mixer length were also optimized using RSM to obtain the highest biodiesel purity.

Renormalization group improved ms and |Vus| determination from hadronic τ decays

We determine the strange quark mass (${m}_{s}$) and quark mixing element $|{V}_{us}|$, and their joint determination from the Cabibbo suppressed hadronic $\ensuremath{\tau}$ decays in various perturbative schemes. We improve this analysis compared to the previous analysis based on the optimal renormalization or the renormalization group summed perturbation theory (RGSPT) scheme by replacing the theoretical longitudinal contributions with phenomenological parametrization; the RGSPT coefficients are used for the dimension-4 Adler functions. The improved analysis results in the extraction of ${m}_{s}(2\text{ }\text{ }\mathrm{GeV})=98\ifmmode\pm\else\textpm\fi{}19\text{ }\mathrm{MeV}$ and $|{V}_{us}|=0.2191\ifmmode\pm\else\textpm\fi{}0.0043$ from the RGSPT scheme.

A poisonous cocktail: ethnic quotas, liberal voting rights and the democracy problem

ABSTRACT The literature on consociational democracies has introduced an important distinction between corporate and liberal types of consociations. However, once we apply a deeper conceptualization of this corporate-liberal divide, we find that many empirical cases are mixing elements of the two. Most consociational democracies of the corporate type rely on ethnic quotas or reserved seats for national elections, but combine them with liberal voting rights, i.e. a ballot that is universal for all voters, without segmenting voters into different identity groups. This has consequences for the democratic principle of “one-person-one-vote,” leading to a novel type of deviation. This article discusses different consociational democracies in light of the one-person-one-vote principle, and identifies new “paradoxes” of representation related to (corporate) quota rules that are combined with (liberal) universal voting rights.

Assessing residence time distributions and hold-up mass in continuous powder blending using discrete element method

Continuous manufacturing of pharmaceutical products can improve process efficiency and quality assurance. The propagation of material through continuous manufacturing processes can be characterized by residence time distributions (RTDs). Conventional parameter-fitted RTD models rely extensively on experimental measurements that are often expensive and limited to available observation methods and instruments. This limitation can be compensated by discrete element method (DEM) simulations. This work evaluates the predictive capabilities of DEM modeling for a continuous powder mixing process. First, the developed DEM model was validated using experimentally measured RTDs. Then, the effects of the mass flow rate, blender element pattern, and blender speed on mean residence time and hold-up mass were studied. The simulation results showed that the mean residence time increased linearly with increasing number of mixing elements but decreased with increasing mass flow rate and blender speed. The hold-up mass increased with increasing mass flow rate and number of mixing elements but decreased with increasing blender speed. The work successfully demonstrated the capability of the DEM model in improving our understanding regarding the impacts of the blender operating conditions on the RTD and hold-up mass as well as in supporting the assessment of control strategies for continuous blending processes.

Light sterile neutrino and leptogenesis

We studied models of leptogenesis where three right-handed Majorana neutrinos are involved and the minimal-extended seesaw mechanism including an additional singlet field produces four light neutrinos. This study shows that the type of mass ordering and heavy Majorana scales can be determined by inputting the simplest orthogonal matrix into the Casas-Ibarra(CI) representation of seesaw. The CP asymmetry produced from the decays of heavy neutrinos and the dilution mass are predicted in terms of the mass and mixing elements of the fourth neutrino. Upon the choice of CI matrix, the existence of a light sterile neutrino is required to explain the high-energy lepton asymmetry in light of phenomenological measurements. Although there are several free parameters attributable to an additional neutrino, the model can be in part constrained by low-energy experiments such as sterile neutrino searches and neutrinoless double-beta decays, as well as the observed baryon asymmetry in the universe.

A 230-GHz Endfire SIS Mixer With Near Quantum-Limited Performance

In this letter, we report the near quantum-limited performance of a 230 GHz endfire superconductor-insulator-superconductor (SIS) mixer utilizing a Nb/Al-AlOx/Nb trilayer. An important feature of this mixer is its use of a unilateral finline for the waveguide-to-planar circuit transition, which allows for a wide radiofrequency (RF) bandwidth, a simple waveguide structure with easy alignment, and for the mixer chip to be aligned along the optical axis. Each of these factors is beneficial in the construction of large-format focal plane arrays. We tested the new finline mixer from 210 to 260 GHz in a liquid helium cryostat at ~4 K. The best recorded noise temperature was approximately twice the quantum limit, which is comparable to conventional radial probe mixers. This suggests that endfire SIS mixers can be used in large format arrays, comprising 100s or even 1000s of SIS mixing elements, while retaining state-of-the-art quantum mixing performance.

Enhanced of fluids mixing and heat transfer in a novel SSK static mixer Organic Rankine Cycle direct contact heat exchanger

In this study, new gas-liquid-liquid three phase direct contact heat exchangers based on SSK mixing elements and annular ribs are proposed to improve the thermal efficiency of the Organic Rankine Cycle. Three types of heat exchangers, including hollow tube heat exchanger, SSK heat exchanger and SSK annular rib combined heat exchanger, are established to compare their heat transfer performance. The heat transfer performance, turbulence intensity, turbulence kinetic energy and pressure drop of three heat exchangers are numerically investigated. The results show that the volumetric heat transfer coefficient, outlet temperature of gaseous working medium, turbulence intensity and turbulent kinetic energy of the combined heat exchanger are significantly higher than those of the SSK heat exchanger and the hollow tube heat exchanger. In addition, the pressure drops of the SSK heat exchanger and the combined heat exchanger are basically the same, which are slightly larger than the pressure drop of the empty tube heat exchanger. In summary, the combined heat exchanger has improved heat transfer performance without causing excessive pressure drop.

Design and validation of an innovative 3D printer containing a co-rotating twin screw extrusion unit

This paper presents the design and validation of an innovative 3D printer containing a co-rotating twin screw extrusion unit (Co-TSE). Single screw print heads were developed in the mid-2000s as an alternative to filament-based 3D printers, but they have limited process flexibility and mixing capacity. The new design accepts material in powder or micro-pellet form, and its dispersive and distributive mixing capacity can be fine tuned by setting output and screw rotation speed independently. The design combines a miniaturized modular Co-TSE operated under starve-fed conditions with a benchtop Cartesian platform. Numerical calculations were performed to ascertain whether the appropriate thermomechanical environment for polymer processing could be created by the proposed design. A prototype was built and extrusion tests were performed under different operating conditions, using polypropylene and a 90/10 wt% polypropylene/polystyrene blend. Two screw configurations were used, with and without kneading discs, to assess the response of the extrusion unit in terms of flow characteristics and mixing performance. The restriction to flow created by the mixing elements determines the starting melt position, and the average residence times, while their shearing and extensional action enhances homogenization effectiveness. The screw configuration and rotation speed do not affect the output, which depends only on the feed rate. Preliminary deposition tests were conducted to determine the feasible printing parameters. A standard tensile test specimen, a square scaffold and a multicolored rectangular box were successfully printed, validating the innovative design. The mechanical properties of printed test specimens were within the expected values.

Numerical Simulation of Mixing Characteristics in a Split-and-Recombine Microchannel

The mixing efficiency in microdevices is limited by laminar flow. For passive mixing, the structure of micromixer determines its mixing performance. A novel micromixer with a self-designed repetitive SAR (split-and-recombine) mixing element was carried out and investigated in the present work. The number of mixing elements for simulation was confirmed primarily. Based on the established model, the flow and geometric parameters in this micromixer were discussed systematically by numerical simulation and evaluated by mixing index. Furthermore, the mixing performance of SAR micromixer was compared with conventional T-shaped micromixer for Reynolds numbers ranging from 0.05 to 960. Finally, we concluded that the novel SAR micromixer revealed high performance of mixing due to the enhanced convection. In addition, its input power was similar to that of T-shaped micromixer, which provided the possibility for future industrial applications.

Serpentine Micromixers Using Extensional Mixing Elements.

Computational fluid dynamics modeling was used to characterize the effect of the integration of constrictions defined by the vertices of hyperbolas on the flow structure in microfluidic serpentine channels. In the new topology, the Dean flows characteristic of the pressure-driven fluid motion along curved channels are combined with elongational flows and asymmetric longitudinal eddies that develop in the constriction region. The resulting complex flow structure is characterized by folding and stretching of the fluid volumes, which can promote enhanced mixing. Optimization of the geometrical parameters defining the constriction region allows for the development of an efficient micromixer topology that shows robust enhanced performance across a broad range of Reynolds numbers from Re = 1 to 100.