pinecone/core-2020-05-10-deduplication huggingface dataset:
Students as Surrogates for Managers: Evidence from a Replicated Experiment

Using students as surrogates for managers in experiments is commonplace, yet this practice is not always valid. To explore when the use of student samples is appropriate, we replicate an experiment previously conducted employing a sample of senior managers involved in financial reporting. The result is that although student and manager responses are significantly different from a statistical perspective, both samples lead to the same conclusion for this experiment. The findings suggest that having some disassociation between students and the target population they are meant to represent does not necessarily make them inappropriate surrogates. To examine when inferences are best supported, we explore the comparability for student sub-groups and managers
Destabilisation of a homogeneous bubbly flow in an annular gap bubble column

This is a pre-publication version of an article published in The Canadian Journal of Chemical Engineering.Experimental results are presented to show that there are very significant differences in the\ud
mean gas void fractions measured in an open tube and a annular gap bubble column, when\ud
operated at the same gas superficial velocity, using a porous sparger. The mean gas void\ud
fraction decreases with increasing ratio of the inner to outer diameter of the annular gap\ud
column and the transition to heterogeneous flow occurs at lower gas superficial velocities and\ud
lower void fractions. Two reasons are proposed and validated by experimental investigations:\ud
(1) the presence of the inner tube causes large bubbles to form near the sparger, which\ud
destabilize the homogeneous bubbly flow and reduce the mean void fraction; this was\ud
confirmed by deliberately injecting large bubbles into a homogeneous dispersion of smaller\ud
bubbles and (2) the shape of the void fraction profiles changes with gap geometry and this\ud
affects the distribution parameter in the drift flux model
WET SCRUBBING INTENSIFICATION APPLIED TO HYDROGEN SULPHIDE REMOVAL IN WASTE WATER TREATMENT PLANT

International audienceHydrogen sulphide removal in a Waste Water Treatment Plant at semi-industrial scale in a compact wet scrubber has been investigated. The gas residence time in the scrubber was reduced to 30 ms using a NaOCl caustic scrubbing solution. The contactor is composed of a wire mesh packing structure where liquid and gas flow co-currently at high velocity (> 12 m.s-1). H2S removal percentages higher than 95% could be achieved whereas a moderate pressure drop was measured (< 4000 Pa). Both the hydrodynamic and chemical conditions can influence the efficiency of the process. Correlations were developed to predict both the pressure drop and the H2S removal efficiency at given operating conditions
Trickle flow liquid-solid mass transfer and wetting efficiency in small diameter columns

A novel method to simultaneously measure liquid-solid-mass-transfer and external wetting
efficiency was employed at column to particle ratios of 10, 6 and 3. Two prewetting
procedures representing the upper (Kan) and lower (Levec) hysteresis branches were used.
For a multipoint distributor on a Kan-prewetted bed wetting efficiency and the specific masstransfer
coefficient were almost unaffected by column diameter. The multipoint distributor on
a Levec-prewetted bed exhibited a decrease in specific mass transfer with decreasing column
diameter. Pointsource experiments resulted in significantly lower wetting and mass-transfer
measurements with an increasing trend with respect to decreasing column diameter. The
results indicate that with proper distribution and prewetting, the effect of column diameter on
averaged wetting and liquid-solid mass transfer is almost negligible, a powerful result
considering the importance of these parameters on reaction experiments.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1939-019Xhb201
A comparison of nonlinear control performance assessment techniques for nonlinear processes

Assessing the quality of industrial control loops is an important auditing task for the control engineer. However, there are complications when considering the ubiquitous nonlinearities present in many industrial control loops. If one simply ignores these nonlinearities, there is the danger of over-estimating the performance of the control loop in rejecting disturbances and thereby possibly overlooking loops that need attention. To address this problem, several techniques have been recently developed to extend the control performance assessment (CPA) of single input/single output linear systems to nonlinear systems. This article surveys these nonlinear CPA techniques and compares their performances using three case studies. These results can be used to guide control engineers to select the most suitable CPA techniques for their particular applications
Incorporating feedforward action into self-optimising control policies

Control structure design traditionally involves two steps of selections, namely the selection of controlled and manipulated variables and the selection of pairings interconnecting these variables. The available criteria for both selections require enumeration of every alternative. Hence, an exhaustive search can be computationally forbidding for large-scale processes. On the other hand, owing to the computational complexity, variables and pairings are often selected sequentially, which may result in suboptimal control structures. In this paper, an efficient branch and bound (BAB) method is proposed to select the variables and pairings together in a multiobjective optimization framework. As an illustration of the proposed multiobjective BAB framework, the minimum singular value rule and the μ-interaction measure are used as the criteria for selection of controlled variables and pairings, respectively. Numerical tests using randomly generated matrices and the large-scale case study of hydrodealkylation of toluene (HDA) process show that the BAB method is able to reduce the solution time by several orders of magnitude in comparison with exhaustive search
From molecules to processes : molecular simulations applied to the design of simulated moving bed for ethane/ethylene separation

This paper presents results of a modelling study on the separation of ethane/ethylene mixture by selective adsorption on zeolite 13X in a simulated moving bed (SMB) unit. Propane and n-butane are evaluated as desorbent candidates. The study encompasses molecular simulation calculations for determination of adsorption parameters, whose results will then be used in a mathematical model for evaluating the performance of an SMB unit. This work is entirely done in silico, by using available force field parameters for the molecular simulations part and reliable mathematical models for the SMB part. Experimental data are solely used for comparison with the molecular simulation results, which are subsequently expanded to calculate adsorption properties for separating the mixtures, without further experimental work. The separation regions of an SMB unit operating with zeolite 13X for ethane/ethylene separation, using propane and n-butane as desorbents, were obtained by simulation at 110 kPa and at four different temperatures: 298, 323, 348 and 373 K. For each desorbent, an operating point was selected, and the size of the required unit was presented for the complete separation of the two components of the mixture
Demineralization of glucose solutions by electrodialysis: Influence of the ionic composition on the mass transfer and process performances

The aim of the present work was to investigate the influence of the ionic composition on the demineralization of a saccharide solution containing glucose. Experiments were carried out in order to evaluate the influence of the ionic composition on the solvent and solutes fluxes (glucose and electrolytes) through the membrane under different conditions (ionic compositions: NaCl, Na2SO4 and CaCl2; with or without current). From diffusion experiments (without current), it was shown that the glucose diffusion flux decreases for increasing ion hydration. These results are in agreement with those obtained in a previous work showing that the transfer modification reflects changes in the membrane properties associated with the hydration of its counter‐ion which is likely linked to swelling mechanisms at a microscopic scale. From the experiments carried out in normal ED conditions (with current) an additional convective contribution was pointed out. This kind of result is rather scarce in the literature. The glucose flux was then the sum of two contributions: diffusion and convection, due to the electro‐osmotic flux which is proportional to the electrical current. The contribution of the glucose convection flux on the overall glucose transfer was ranged between 70 and 90 % according to the electrolyte nature (NaCl, Na2SO4 and CaCl2) and the electric current (150 or 300 A m−2). The variation of the convective flux has been further correlated to the hydration of the ions. Indeed increasing convection fluxes were obtained for decreasing anion (or cation) hydration. It was shown that the saccharide transfer increases in presence of salts and that this increase was correlated to the saccharide dehydration in presence of electrolyte. Finally, the solvent, ions and glucose fluxes were used to calculate the glucose loss factor versus the demineralization factor to evaluate the influence of the electrolyte nature on the demineralization process performances. It was observed that, for a fixed demineralization factor, the glucose loss factor (comprised between 4 and 5 % for a demineralization factor of 90 %) increased with the ion hydration due to the higher contribution of the glucose convection flux
Hydrocarbons – Water Phase Equilibria Using the CPA Equationof State with a Group Contribution Method

International audienceIt is proposed in this paper to extend the original group contribution method PPR78 to systems containing water, by combining it to the Cubic–Plus–Association (CPA) equation of state (EoS). Applying simple geometric combination rules, the binary interaction parameter kij(T) can be calculated frominteraction parameters between hydrocarbon groups and water. This model, called the GC–PR–CPA is applied to predict hydrocarbons – watermutual solubilities over a wide temperature and pressure range, depending on available literature data. Group interaction parameters, here CH4,C2H6, CH3, CH2, CH, C, CHaro, CH2,cyclic, CHcyclic/Ccyclic, C2H4, CH2,alkene/CHalkene with H2O have been defined with solubility data. Predictions ofthe developed model have been validated against independent solubility data as well as water content in hydrocarbon rich phase. Predictions of thenew model are in good agreement for light and medium hydrocarbons; however, some deviations are observed for heavier hydrocarbons
Towards the modelling of a heat-exchanger reactor by a dynamic approach

The aim of this paper is to present the development of a simulation tool in order to assess the inherently safe characteristics of a heat‐exchanger reactor(HEX) operating reaction systems. The modelling of steady and transient states of a HEX reactor is performed following a hybrid dynamic approach. The global dynamic behaviour of this reactor can be represented by several continuous models, which are bounded by state or time events. Each continuous model is defined as a system of partial differential‐algebraic equations. The numerical scheme is based on the method of lines. Special attention is paid to the model initialization and a simulation strategy of the start‐up phase is presented. The validation of the model is made by numerous examples, such as the simulation of an exothermic reaction
Treatment of gaseous effluents by using surface discharge plasma in continuous reactors: Process modelling and simulation

International audienceIn the present work, the oxidation of isovaleraldehyde, a typical pollutant of indoor air, is investigated by using two different plasma DBD reactors: cylindrical and planar reactor. The study of the influence of the specific energy shows that its increment is accompanied by an increase of the removal efficiency. In fact, when specific energy extends three times, the removal efficiency is increased from 5 to 40%. Moreover an increase of the specific energy induces a higher mineralization due to byproducts oxidation with reactive species production. The same behavior is observed with ozone production. A generic mathematical model is developed to represent the experimental results obtained. This model is based on several mass transfer steps occurring in series between bulk and plasma phases. The degradation reaction mechanism is supposed to occur on two steps. Firstly, isovaleraldehyde leads to the formation of a fictitious equivalent intermediate (EI). In a second step, EI is transformed into CO and CO2. This approach gives a good agreement between modeling and experiments with a satisfactory overall description of byproducts formation. This original approach allows for the simulation of plasma oxidation kinetics process without knowing the complete chemical pathway
Development of a transfer model for the design and the operation of sodium purification systems for fast breeder reactors

Operating a Sodium Fast Reactor (SFR) in reliable and safe conditions requires mastering the quality of the sodium ﬂuid coolant, regarding oxygen and hydrogen impurities contents. A cold trap is a puriﬁcation unit in SFR, designed to maintain oxygen and hydrogen contents within acceptable limits. The puriﬁcation of these impurities is based on crystallization of sodium hydride on cold walls and sodium oxide or hydride on wire mesh packing. Indeed, as oxygen and hydrogen solubilities are nearly nil at temperatures close to the sodium melting point, i.e., 97.8 8C, on line sodium puriﬁcation can be performed by cooling down liquid sodium ﬂows and promoting crystallization of sodium oxide and hydride. However, the management of cold trap performances is necessary to prevent from unforeseen maintenance operations, which could induce shut-down of the reactor. It is thus essential to understand how a cold trap ﬁlls up with impurities crystallization in order to optimize the design of this system and to overcome any problems during nominal operation. This paper deals with the mathematical modelling of crystallization process in a cold trap and predicts the location and the amount of the impurities deposit, on cold walls for sodium hydride and on wire mesh packing for sodium oxide. A model of the front propagation by “diffuse deposit interface method” was developed and sensitivity to various parameters was evaluated. These results will enable to understand the consequences of the impurities deposited on the hydrodynamics and heat transfer in a cold trap
The engine reformer: Syngas production in an engine for compact gas-to-liquids synthesis

Methane (CH[subscript 4]) reforming was carried out in an internal combustion engine (an “engine reformer”). We successfully produced syngas from the partial oxidation of natural gas in the cylinder of a diesel engine that was reconfigured to perform spark ignition. Performing the reaction in an engine cylinder allows some of the exothermicity to be captured as useful work. Intake conditions of 110 kPa and up to 480 °C allowed low cycle-to-cycle variability (COV[subscript nimep] < 20 %) at methane-air equivalence ratios (ϕ[subscript M]) of 2.0, producing syngas with an H[subscript 2]-to-CO ratio of 1.4. Spark ignition timing was varied between 45–30° before top-dead-center (BTDC) piston position, showing significant improvement with delayed timing. Hydrogen (H[subscript 2]) and ethane (C[subscript 2]H[subscript 6]) were added to simulate recycle from a downstream synthesis reactor and realistic natural gas compositions, respectively. Adding these gases yielded a stable combustion up to hydrocarbon-air equivalence ratios (ϕ[subscript HC]) of 2.8 with COV[subscript nimep] < 5 %. Ethane concentrations (with respect to methane) of up to 0.2 L/L (20 vol%) (with and without H[subscript 2]) produced robust and stable combustions, demonstrating that the engine can be operated across a range of natural gas compositions. Engine exhaust soot concentrations demonstrated elevated values at ϕ[subscript HC] > 2.4, but < 1 mg/L below these equivalence ratios. These results demonstrate that the engine reformer could be a key component of a compact gas-to-liquids synthesis plant by highlighting the operating conditions under which high gas conversion, high H[subscript 2]-to-CO ratios close to 2.0, and low soot production are possible.United States. Advanced Research Projects Agency-Energy (Award DE-AR0000506)Research Triangle InitiativeMIT Energy InitiativeMassachusetts Institute of Technology. Tata Center for Technology and Desig
Population balances in case of crossing characteristic curves: Application to T-cells immune response

International audienceThe progression of a cell population where each individual is characterized by the value of an internal variable varying with time (e.g. size, mass, and protein concentration) is typically modelled by a population balance equation, a first-order linear hyperbolic partial differential equation. The characteristics described by internal variables usually vary monotonically with the passage of time. A particular difficulty appears when the characteristic curves exhibit different slopes from each other and therefore cross each other at certain times. In particular, such a crossing phenomenon occurs during T-cell immune response when the concentrations of protein expressions depend upon each other and also when some global protein (<i>e.g.</i> Interleukin signals) that is shared by all T-cells is involved. At these crossing points, the linear advection equation is not possible by using the hyperbolic conservation laws in a classical way. Therefore, a new transport method is introduced in this article that is able to find the population density function for such processes. A multi-scale mathematical modelling framework is employed. At the first scale, two processes, the activation and reaction terms (assimilated as nucleation and growth in particulate processes), are studied as independent processes. At the second scale, the dynamic variation in the population density of activated T-cells is investigated in the presence of activation and reaction terms. The newly-developed transport method is shown to work in the case of crossing characteristics and to provide a smooth solution at the crossing points in contrast to the classical numerical techniques
Coumarin and carbazole fluorescently modified cellulose nanocrystals using a one-step esterification procedure

Fluorescent cellulose nanocrystals with carbazole and coumarin functionalities were synthesised in a one-step esterification reaction using carbazole-9-yl-acetic acid and coumarin-3-carboxylic acid respectively, using a p-toluenesulfonyl chloride/pyridine system. Characterization with elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy, infrared, absorption and emission spectroscopy, and
AFM and TEM imaging confirmed that a high degree of modification could be achieved (up to DSsurf = 1.33) while retaining the CNC core crystallinity and nanoparticle dimensions. The present grafting method gives a straightforward way when compared with previously reported fluorescent labelling methodologies and gives an extremely high grafting density while retaining the CNC crystallinity. UV spectroscopy also indicates fluorescence quenching at high grafting densities so that
optimal fluorescence does not necessarily mean maximum grafting density.status: publishe
Heat convection and radiation in flighted rotary kilns: A minimal model

We propose a minimal model aiming to describe heat transfer between particles
(i.e. grains) and gases in a model of flighted rotary kilns. It considers a
channel in which a convective gas interacts with a granular suspension and a
granular bed. Despite its simplicity it captures the main experimental findings
in the case of dilute suspension of heavy grains typical of what can be
observed in many industrial rotary kilns. Energy balance between each phase
takes into account the main heat transfer mechanisms between the transverse
granular motion and the convective gas. In the absence of radiation heat
transfer, the model predicts exponential variations of the temperatures
characterized by a length which depends on the granular and gas heat flow rates
as well as on the exchange areas. When radiation is taken into account, the
model can be solved numerically. For this case, the temperature variations can
be fitted by stretched exponentials whose parameters are found to be
independent of the studied phases. Finally, an efficiency criterion is proposed
to optimize the length of the system
Gaseous ozone decomposition over high silica zeolitic frameworks

For several decades, it has been known that ozone emissions are harmful to humans, plants, and animals. Heterogeneous catalytic decomposition is an efficient process for removing ozone from air. This study examines the effect of the zeolite's framework and pore width on efficiency for decomposing gaseous ozone. Four highly hydrophobic zeolites are used: a large cavity zeolite (Faujasite/H‐FAU), a medium pore zeolite with parallel channel (Mordenite/H‐MOR), and two medium pore zeolites with interconnected channels (H‐ZSM‐5/H‐MFI and Na‐ZSM‐5/Na‐MFI). Experiments were conducted in fixed‐bed flow reactors loaded with zeolite at ambient conditions (20 °C and 101 kPa). Zeolite surfaces were analyzed during the experiments in order to understand the influence of physical and chemical surface properties on the ozone decomposition mechanism. A higher amount of ozone is eliminated using H‐MOR, compared with the zeolite samples H‐FAU, H‐MFI, and Na‐MFI. Pore width and micropore framework size distribution (channel and cages) appear to be key factors. A narrow channel or cage, slightly larger than the ozone molecule size, seems to promote ozone interactions with Lewis acid sites. Fourier transform infrared spectroscopy shows that Lewis acid sites (LAS), located on the walls of zeolite pores, decompose ozone. This leads to the formation of atomic oxygen species that could react with another ozone molecule to form dioxygen. Hence, LAS are regenerated, ready to decompose another ozone molecule once more
Application of inductive heating to granular media: Modelling of electrical phenomena

A model is examined in order to predict the behaviour of a granular bed made with conductive particles subjected to an inductive electromagnetic field. The model shows how heat generated in the bed can be described by its electric impedance for the high‐frequency generator required for inductive heating. Once the relationship between electrical characteristics and power dissipation has been established, comparisons between experimental and theoretical results are presented and the validity of the model is discussed
Measurements of Bubble Characteristics: Comparison Between Double Optical Probe and Imaging

The objective of this study is to evaluate the accuracy of double optical probe technique in local two-phase flow measurements. Able to provide both bubble velocity, chord length, and gas hold-up, this\ud
technique involves nevertheless delicate signal treatment procedures and, being intrusive, depends on probe tips configurations and sizes. During probe-bubble interactions, bubble surface is occasionally deformed and this can complicate measurements analysis. The current study is focussed on the rise of single bubbles of known sizes in still water (equivalent diameter of 2.15mm and 4.5mm). Bubble parameters\ud
obtained from digital image processing method and from a double optical probe are compared statistically