pinecone/core-2020-05-10-deduplication huggingface dataset:
Farmgate Private Standards and Price Premium: Evidence From the GlobalGAP Scheme in Kenya's French Beans Marketing

The proliferation of private quality and assurance schemes in international trade is defining market access in high value chains. The prime concern for small-scale producers is whether price premiums are realizable due to compliance. Using French beans marketing, the authors find that GlobalGAP certification, produce traceability, number of suppliers, competition for supplies, direct procurement, a good road network, and supply contracts have positive farmgate price effects for smallholders. Potential policy implications are drawn
Do inventories have an impact on price transmission? Evidence from the Canadian chicken industry

This paper investigates the influence of inventories in explaining the magnitude of price transmission. The empirical strategy consists of two distinct steps. First, the flexible non-linear framework of Hamilton is used to investigate the influence of inventories on price transmission. The procedure detects significant non-linearities and suggests that the price transmission elasticity is increasing in the level of the farm price and decreasing in the ratio of inventories to sales. This evidence leads to specific functional forms for the price transmission and target inventory equations which are estimated in a second step. The estimation procedure accounts for potential simultaneity between sales at the wholesale level and the wholesale price. Our results suggest that price transmission is lower (higher) when inventories are below (above) a target which is function of domestic sales.
Importance of Social Influence in Consumers' Willingness to Pay for Local Food: Are There Gender Differences?

The authors assess consumers' willingness to pay (WTP) for a local food product using an experimental auction. As local foods involve a social component, they aim also to test if social influence affects WTP for local foods and if the effects of social influence on WTP are different between men and women. They found that consumers are willing to pay a premium for the analyzed local food product. Moreover, social influence indeed affects WTP values, but the effects are different between men and women. Although social influence positively affects WTP for local foods for women, the effect is negative for men. The results have significant marketing and policy implications related to the promotion of local foods
Preferences, market structure, and welfare evaluations in the Argentinean FFP industry: a case in Buenos Aires Province

This paper analyzes the demand of frozen fried potatoes in an important city of Argentina, Mar del Plata, and the effect of changes in market structure on consumer welfare. We find that high income individuals are more concerned about health and nutrition, and that younger and lower-income consumers are more price sensitive. The results suggest that consumer surplus would decrease with a merger between the two smaller firms of the market, and would increase if the market turned into a single-product firms industry. The influence of these counterfactual changes would be greater for wealthier and older individuals. This article contributes to the analysis of a food market which is rapidly growing in developing countries and is starting to play a more relevant role in consumers' diet.Fil: González, Julia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina.Fil: Lacaze, María Victoria. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina
Effect of price-discount distribution in multi-unit price promotions on consumers' willingness to pay, sales value, and retailers' revenue

Using multi-unit auctions, we examined the effect of different distributions of price discount across multiple units of a relatively new product on consumers' Willingness to Pay (WTP), sales value and retailers' revenue. We found that allowing the price discount to be increasing in the number of units increases willingness to pay, sales value and retailers' revenue and that a price discount that is uniformly distributed across units also has the potential to motivate consumers to buy more units of the product. However, multi-unit price promotions that concentrate all the amount of price discount on the last unit only generate a weak positive effect on sales value. [EconLit Citations: C910, D120, M310]. (C) 2014 Wiley Periodicals, Inc.Postprint (published version
Interaction of separation and reactive stages on ETBE reactive distillation columns

Reactive distillation is a favorable alternative to conventional series of reactor-distillation processes for ether productions. However, the design of such columns is complicated due to the interaction between vapor-liquid equilibrium and reaction rates. There are conflicting reports on whether adding excessive separation stages degrade the column performance. A comparison is made of several designs of single and double feed reactive distillation columns for ETBE production to investigate the effects of separation and reaction stages on the overall performance. The explanations are presented using simulation results, whose mathematical models are written in the Aspen Plus environment. The results confirm that a conservative approach by adding extra separation and reaction stages can be applied to reactive distillation design. However, output multiplicity may be observed for longer column and should be considered in the early design phase
Influence of microstructure on the rheological behavior of dense particle gels

Rheological measurements are performed on highly concentrated alumina gels. By using an in situ mechanism based on enzyme-catalyzed internal reactions, we are able to form gels of highly concentrated particles without disturbing the microstructures that develop during the gelation process. These gels are produced by two different destabilization mechanisms: Either the pH of the suspension is shifted toward the isoelectric point (ΔpH method) or the ionic strength of the suspension is increased at a constant pH (ΔI method). The two destabilization mechanisms lead to gels of significantly different microstructures. We find notable differences in the rheological behavior of the two systems, suggesting a bond-bending mechanism for stress transmission in the case of ΔpH gels and a bond-stretching mechanism in the case of ΔI gels. In addition, for both kinds of gels we compare the in situ properties to those obtained after altering the microstructure by shearing. Results suggest an increase in elastic and yield properties of concentrated particle gels with decreasing homogeneity of their microstructures
Effect of Volume Decrease on Fluidization Quality of Fluidized Catalyst Beds

The fluidization quality significantly decreased when the reaction involving a decrease in the gas volume was carried out in a fluidized catalyst bed. In the present study, we carried out the hydrogenation of carbon dioxide in a transparent column to observe the bed behavior. When the reaction rate was increased, the fluidity of the emulsion phase decreased and channeling occurred. When the fluidity of the emulsion phase decreased even further, the upper part of the bed was defluidized and this part was lifted up through the column. This phenomenon caused the entrainment of a large amount of catalyst particles from the reactor. We studied the effects of the reduction rate of the gas volume and the maximum gas contraction ratio on the fluidization behavior. The criterion for a stable operation, which could be successfully given by the gas-volume reduction rate, is useful for determining the operating conditions needed to establish good fluidization when the reactions involving a decrease in the gas volume are carried out in a fluidized catalyst bed
Process Flow Diagram of an Ammonia Plant as a Complex Network

Complex networks have attracted increasing interests in almost all
disciplines of natural and social sciences. However, few efforts have been
afforded in the field of chemical engineering. We present in this work an
example of complex technological network, investigating the process flow of an
ammonia plant (AP). We show that the AP network is a small-world network with
scale-free distribution of degrees. Adopting Newman's maximum modularity
algorithm for the detection of communities in complex networks, evident modular
structures are identified in the AP network, which stem from the modular
sections in chemical plants. In addition, we find that the resultant AP tree
exhibits excellent allometric scaling.Comment: 15 pages including 4 eps figure
Ruthenium catalyzed oxidative conversion of isatins to anthranilic acids: Mechanistic study

Oxidation of isatins (isatin, 5-methylisatin, 5-bromoisatin, and 5-nitroisatin) to their corresponding anthranilic acids was performed with sodium N-bromo-p-toluenesulfonamide or bromamine-T (BAT) as an oxidant and ruthenium trichloride (Ru(III)) as a catalyst in HCl medium at 30 +/- 0.1 degrees C. The four reactions follow identical kinetics with a first-order dependence each on [BAT](o) and [Ru(III)], zero-order on [Isatin], and inverse fractional-order on [H(+)]. Activation parameters have been deduced for the composite reaction. The rates satisfactorily correlate with the Hammett U relationship and the reaction constant p is -0.36 signifies that the electron donating groups accelerate the reaction while the electron withdrawing groups retard the rate. An isokinetic relationship is observed with beta = 360 K, indicating that enthalpy factors control the reaction rate. Oxidation products of isatins were identified as their corresponding anthranilic acids by GC-MS analysis and the yields were found to be > 90%. Under similar experimental conditions, the kinetics of Ru(III)-catalyzed oxidation of isatins with BAT has been compared with that of uncatalyzed reactions, revealing that the catalyzed reactions are three to fourfold faster. The observed results have been explained by a plausible mechanism and the related rate law has been deduced. The method adopted for the oxidation of isatins to anthranilic acids in the present work offers several advantages and can be scaled up to industrial operation. (c) 2008 American Institute of Chemical Engineers
The effects of manifold flow on mass transport in electrochemical filter-press reactors

The mass transport rates to planar electrodes, in a series of electrochemical laboratory filter-press reactors were measured to quantify the effects of the inlet and outlet design manifolds on the fluid flow. In small reactors, entrance/exit effects are especially important due to the localized generation of fluid recirculation zones, which affect the overall rate of mass transport. Limiting current data, the cathodic reduction of Cu(II) ions on a copper surface (under convective-diffusion control) were used to measure global mass transport coefficients. The data are compared with those from a well-characterized laboratory cell, the FM01-LC electrolyzer. The importance of manifold design in small-scale electrochemical reactors is discussed, and several dimensionless parameters are used to characterize the manifold geometry
Exponential observers for distributed tubular (bio)reactors

14 páginas, 2 tablas, 9 figuras, 2 apéndicesThe dissipative nature of spatially distributed process systems is exploited to develop\ud
efficient exponential state observers based on a low-dimensional dynamic representation\ud
of the original set of partial differential equations. The suggested approach combines\ud
standard observer design techniques for reactors, where the reaction rates are\ud
unknown with efficient model reduction methodologies based on projection of the original\ud
concentration and temperature fields on low-dimensional subspaces capturing the\ud
slow dynamics of the process. The global exponential stability of the resulting observer\ud
is derived combining classical Lyapunov analysis with a transformation that allows us\ud
to obtain a diffusion system from a diffusion-convection system. In addition, aspects\ud
related to the location of sensors and their influence on the ability to reconstruct the\ud
necessary fields to feed the observer will also be consideredThe authors acknowledge\ud
financial support received from the Spanish Government (MCyT Projects\ud
PPQ2001-3643 and DPI2004-07444-C04-03) and Xunta de Galicia\ud
(PGIDIT02-PXIC40209PN)Peer reviewe
Optimal tuning of thermodynamic-based decentralized PI control loops: application to the Tennessee eastman process

21 páginas, 24 figuras, 5 tablasThe need of designing decentralized control loops emerges to ensure the global stability of a given process plant. To that purpose, it has been proposed in recent works a systematic approach to derive robust decentralized controllers, which is based on the link between thermodynamics and passivity theory, as well as on the fundamentals of process networks. This thermodynamic-based control (TBC) methodology has several steps: (1) Decomposition of the considered process system into abstract mass and energy inventory networks; (2) design of conceptual mass and energy inventory control loops to guarantee the convergence of the states of the plant to a compact convex region defined by constant inventories, where input-output stability follows; (3) definition of intensive variable control loops (if needed) to achieve global stability, and (4) realization of the conceptual inventory and intensive variable control loops over the available degrees of freedom in the system by using, for instance, PI controllers. A tool to tune these PI control loops is developed, based on the solution of a nonlinear programming optimization problem (NLP), in order to complete the proposed hierarchical and systematic TBC design. The aim is to minimize a given cost function, subject to both the system dynamics, as well as the linear and nonlinear constraints (no disturbances affecting the system are considered), where the vector of decision variables will be formed by the parameters of the PI controllers used in the defined decentralized control loops. We will test this tuning procedure in several control designs developed for the challenging benchmark of the Tennessee Eastman Process (TEP) by Ricker and Larsson et al., as well as in two TBC candidates, concluding that the best candidate among the proposed ones (in terms of final cost function) will be one of these TBC designs. For solving the NLP problem, two local (FMINCON and NOMADm) solvers, and a new global (MITS) one are used, comparing their performances. Finally, the dynamic analysis of the optimal tuned closed loop systems is carried out, finding that the presented TBC control candidates will be stable, while the other control structures considered exhibit complex dynamic behaviors or even instability when disturbances affecting the process are consideredThe authors acknowledge the financial support received from the Spanish Government (MCyT Projects PPQ2001-3643), Xunta de Galicia (PGIDIT02-PXIC40209PN) and "PRIMS" Marie Curie Action (MRTN-CT-2004-512233).Peer reviewe
Lateral surface nonuniformities in drying latex films

The length scales of film, thickness nonuniformities, commonly observed in polymer colloid (i.e., latex) films, are predicted. This prediction is achieved by investigating the stability behavior of drying latex films. A linear stability analysis is performed on a base solution representing a uniformly drying latex film containing a surfactant. The analysis identifies film thickness nonuniformities over two length scales: long (millimeter) range (from lubrication theory) and short (micrometer) range (from nonlubrication theory). Evaporation and surfactant desorption into the bulk film are identified as the primary destabilizing mechanisms during drying. Experimental evidence through direct visualization and atomic force microscopy confirm the existence of nonuniformities over both length scales, which are shown to be functions of parameters such as initial particle volume fraction, surfactant amount, and desorption strength, while being independent of drying rate. © 2008 American Institute of Chemical Engineers
Drying-induced surface roughening of polymeric coating under periodic air blowing

We carried out numerical simulations of drying-induced surface roughening of a moving liquid layer under periodic air blowing conditions. Using spatially non-uniform Biot number profiles along the coating surface, the solutions of coupled diffusion/heat transfer equations reveal a periodic growth and relaxation in concentration gradients in the vicinity of the liquid–gas interface. The resultant interfacial stress variations promote particular asymmetric surface topographies that grow and level in a sequential manner. The unique surface roughness is identified by considering time scales required for the web motion, the stress-induced surface evolution, and the pressure-driven leveling. Predicted drying maps represent the surface roughening behavior as regions in parameter space. © 2009 American Institute of Chemical Engineers AIChE J, 200
Precipitation dynamics of zinc sulfide multi-scale agglomerates

International audienceHomogeneous precipitation of zinc sulfide from thioacetamide decomposition in presence of zinc sulfate in acid solution results in the formation of four-scale agglomerates. We present here experimental results relative to the monitoring of several physicochemical (pH, electrical conductivity, concentration in sulfide ions, turbidity) and morphological (agglomerate shape and size) parameters throughout the precipitation process. From these parameters essential characteristics of the precipitation process can be determined, especially the supersaturation level and the precipitated product mass. From this information and with the help of microphotographs of samples withdrawn at different stages of the precipitation, it is possible to formulate a new mechanism of zinc sulfide precipitation. In particular the nature of the different agglomeration scales is elucidated as well their succession in time
Correlating the solubility of supercritical gases in high-molecular weight substances using a density-dependent equation

El pdf del artículo es la versión pre-print.Chrastil (1982) established that the solubility of a substance in a supercritical fluid can be correlated with the density of the pure supercritical gas. Recently, the solubility of supercritical fluids in different organic liquids was successfully correlated as a function solely of the supercritical fluid density, since we demonstrated that the supercritical fluid density also defines the solubility of the gas in the liquid phase. In this work, the solubility of supercritical carbon dioxide in high-molecular weight substances, such as high-molecular weight paraffins, alcohols, fatty acids, fatty acid methyl and ethyl esters, has been correlated and constants provided. More than 20 binary systems comprising around 1000 solubility data points were correlated, obtaining regression coefficients greater than 0.96 and confirming the goodness of the density-dependent equation previously reported.The authors thank the financial support from Comunidad Autónoma de Madrid (ALIBIRD, Project S2009-AGR-1469) and the Ministerio de Ciencia e Innovación (Project 25506 FUN-C-FOOD), Spain.Peer Reviewe
Experimental investigation of a circulating fluidized bed reactor to capture CO2 with CaO

[EN] Calcium looping processes for capturing CO2 from large emissions sources are based on\ud
the use of CaO particles as sorbent in circulating fluidized bed (CFB) reactors. A\ud
continuous flow of CaO from an oxyfired calciner is fed into the carbonator and a\ud
certain inventory of active CaO is expected to capture the CO2 in the flue gas. The\ud
circulation rate and the inventory of CaO determine the CO2 capture efficiency. Other\ud
parameters such as the average carrying capacity of the CaO circulating particles, the\ud
temperature and the gas velocity must be taken into account. To investigate the effect of\ud
these variables on CO2 capture efficiency we employed a 6.5 m height CFB carbonator\ud
connected to a twin CFB calciner. Many stationary operating states were achieved using\ud
different operating conditions. The trends of CO2 capture efficiency measured are\ud
compared with those from a simple reactor model. This information may contribute to\ud
the future scaling up of the technology.The work was possible thanks to a contract with the companies Endesa and Hunosa and\ud
to the CaOling project funded by the European Commission FP7. N Rodríguez\ud
acknowledges a fellowship awarded by FICYT. The assistance of B González, F\ud
Fuentes and I Rodríguez during the experiments and sample analysis is also\ud
acknowledged.Peer reviewe
Parallel hydrogenation for the quantification of wetting efficiency and liquid-solid mass transfer in a trickle-bed reactor

A novel method for the measurement of wetting efficiency in a trickle-bed reactor under reaction conditions is introduced. The method exploits reaction rate differences of two first-order liquid-limited reactions occurring in parallel, to infer wetting efficiencies without any other knowledge of the reaction kinetics or external mass transfer
characteristics. Using the hydrogenation of linear- and isooctenes, wetting efficiency is measured in a 50-mm internal diameter, high-pressure trickle-bed reactor. Liquid–solid mass transfer coefficients are also estimated from the experimental conversion data. Measurements were performed for upflow operation and two literature-defined boundaries of hydrodynamic multiplicity in trickle flow. Hydrodynamic multiplicity in trickle flow gave rise to as much as 10% variation in wetting efficiency, and 10–20% variation in the specific liquid–solid mass transfer coefficient. Conversions for upflow
operation were significantly higher in trickle-flow operation, because of complete wetting and better liquid–solid mass transfer characteristics
A novel approach for modeling bubbling gas–solid fluidized beds

A phenomenological discrete bubble model is proposed to help in the design and dynamic diagnosis of bubbling fluidized beds. An activation region mechanism is presented for bubble formation, making it possible to model large beds in a timely manner. The bubbles are modeled as spherical-cap discrete elements that rise through the emulsion phase that is considered as a continuum. The model accounts for the simultaneous interaction of neighboring bubbles by including the trailing effects due to the wake acceleration force. The coalescence process is not irreversible and therefore, the coalescing bubble pair is free to interact with other rising bubbles originating the splitting phenomena. To validate the model, the simulated dynamics are compared with both experimental and literature data. Time, frequency, and state space analysis are complementarily used with a multiresolution approach based on the empirical method of decomposition to explore the different dynamic scales appearing in both the simulated time series and those obtained from experimental runs. It is concluded that the bubble dynamics interactions play the main role as the driver of the resulting bed dynamics, matching the main features of measured bubble dynamics. Exploding bubble phenomena have been identified by establishing a direct relation between the bubble generation, interaction and eruption, and the measured signalsProjects DPI2009-10518 (MICINN) and CARDENER-CM (S2009ENE-1660)Publicad