Understanding hydrotropism: A chemical engineering perspective

The mechanism of root hydrotropism has been a mystery for many years, due to the complexity of the interactions between the external environment and plants themselves. To gain an engineering perspective, the time‐dependent hydrotropism of a single root has been modeled, initially using a two‐dimensional model. Based on the water and nutrient distribution in rhizosphere as computed with the conservation equations, together with a basic reaction‐kinetics‐type growth model and an intuitive root bending model, it has been found that the root already possesses the property of hydrotropism. For the first time, hydrotropism could be tracked by a process engineering model, which is a new idea based on chemical engineering concept, suggesting an alternative mechanism of hydrotropism. The effects of different initial root widths, lengths, and other growth/transport coefficients on root hydrotropism have then been explored. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1331–1346, 2016     

On the possibility of using embedded electrodes for the measurement of dielectric properties in organic coatings

The present paper discusses the electric field distribution when an electric field is applied between two sensing electrodes embedded in an organic coating applied on metallic substrate. The results show that current lines tend to short-circuit throughout the metallic substrate and hence the measured impedance tends to approach that of the volume located below the electrodes plus the interfacial impedance. The results obtained from the numerical model have been verified by experimental measurements on organic coatings.     

On the rectification of measurement errors for complex chemical plants: Steady state analysis

An algorithmic approach is developed in the present work, which allows: (i) the classification of the measured and unmeasured process variables, (ii) The estimation of the desired unmeasured variables (using available measurements) in a complex chemical plant and (iii) the rectification of the process measurements. The method is very general and unlike the previous works it can be used in conjunction with linear and nonlinear mass and heat balances.The size of the estimation problem has been reduced significantly. Different algorithms are presented which permit the solution of special practical problems, and stochastic tests are proposed to check the consistency of the process data and detect gross measurement errors.Several examples demonstrate the developed algorithms and indicate the usefulness of the proposed approach, in classifying and estimating the processing variables and adjusting the process data through the utilization of mass and heat balances.     

Hydrogen evolution reaction on Ni-P alloys: The internal stress and the activities of electrodes

The hydrogen evolution reaction (HER) was studied on Ni-P electrodes prepared by electrodeposition at temperatures varying from 23 °C to 65 °C. The activities for the HER of the electrodes first decreased slowly with the increasing temperature of the Ni-P preparation. A sudden decrease in the HER activity occurred on the electrode prepared at 65 °C. Similar dependence was found for the variation of the amounts of absorbed hydrogen with the electrodeposition temperature of the Ni-P electrodes. The behavior of Ni-P electrodes prepared from Ni-P powders was quite different. (Ni-P powder was prepared by peeling off the Ni-P layer and by milling the leaves of the Ni-P alloy in a vibrating ball mill.) The Ni-P powder electrodes displayed little activity independently of the temperature of the Ni-P powder preparation. It was followed from the results that the high activity for the HER of the layer Ni-P electrodes prepared at T ≤ 53 °C was caused by the internal stress in the layer. The stress originated during the electrodeposition of the Ni-P layer by co-deposited and absorbed hydrogen.     

Evaluation of the biomass fractionation capability of the ultrafiltration permeate: A learning project for chemical engineering students

This paper presents a 6-month integrated learning project, suitable for chemical engineering students in their last academic course (4 years bachelor). Within the Department of Chemical and Environmental Engineering at the University of the Basque Country (UPV-EHU), the performance of the project was established offering to the students the possibility of developing practical aspects studies in order to introduce them to the engineering profession. The general goals of the project have been to develop basic competences, such as the capability of finding and synthesizing the available information, the active participation in a team work, the improvement of the communications (oral and written) skill, the time management, the problem identification, strategy raising, the autonomy, in summary, to improve the students’ performance in multitask problem solving using a team work approach. The proposed educational objectives were achieved. The participant students were positive when asked whether, overall, the development of this project was “worth the effort” indicating as the most important benefit the developing of considerable indepth understanding and expertise in their work field.     

风险管理视角下的化工企业内部控制浅析

随着市场经济的不断进步和发展,我国的企业也面对着更加广阔的市场,参与了更广泛的竞争,化工企业也不例外。全球化背景下,在提高企业竞争力的同时,加强企业的风险管理,提高企业的内部控制水平,促进企业的健康有序发展十分必要。     

Cooperative WebLab in chemical engineering between France and Brazil: Validation of the methodology

A WebLab is an experiment operated remotely via Internet. Besides the strictly technical aspects of such an experiment, which may contribute to the learning of Chemical Engineering fundamentals, there is also important feedback when teams of students of two different countries are working together: the WebLab becomes an intercultural experience, enhancing the communication skills of the students. A WebLab between Universidade Federal de São Carlos (DEQ/UFSCar) and the Ecole Nationale Supérieure d’Ingénieurs en Arts Chimiques et Technologiques (ENSIACET) is presented in this work. A mass transfer experiment in a bench scale reactor (stirred and aerated) had to be studied by mixed teams, thus emulating challenges that will be common in future working environments. In order to perform the experiment, students in Brazil and in France were put into groups. The students had to make decisions about the procedure for executing the experiments. All the students were able to control the equipment, no matter where they were physically. Students communicated using video conference software. The students’ and teachers’ opinions of this experience were very positive. This methodology is an important contribution to the education of engineers in a world integrated by modern communication technologies.     

Student Peer Assessment: A research study in a level III core course of the bachelor chemical engineering program

A study of anonymous student peer marking in a level III (third year) core course of the bachelor chemical engineering has shown that there was no significant difference (p > 0.05) in the average marks awarded by student assessors who had idealized solutions of the lecturer compared with those who did not; although more students with solutions (84%) completed the peer task than those without (69%). Students in a cohort of 64 (21 females, 43 males) were randomly assigned as a student-pair and tasked to mark each other's solutions to three numeric-type problems out of a possible 50, but only one student had idealized solutions. In 49 valid responses, 27 with and 22 without solutions, the maximum mark awarded by any assessor was 49 and the maximum awarded by the tutor was 50. The overall mean grade over the three problems was 14.3 for those with solutions and 14.5 without. The overall mean grade of the experienced tutor was 14.6. Despite this agreement in mean marking there were notable differences between student assessors and tutor marks in particular cases. The problems required stage calculations with reflux and column efficiencies; each had the marks indicated to be awarded for all sub-sections. Granularity in grades for both student assessors and tutor was a 1/2. There was no evidence of student collusion in marking. Independent survey results showed more than 3/4 of all student assessors highly valued this learning experience and that it stimulated interest in the course material. Students without solutions however were marginally less likely to want to have peer assessment in other courses (p = 0.095).     

A preliminary study on the effectiveness of inquiry-based activities for addressing misconceptions of undergraduate engineering students

This paper presents results from a preliminary study of the effectiveness of using inquiry-based activities to address misconceptions held by undergraduate engineering students in heat transfer and thermodynamics. These targeted misconception areas were identified previously as both important and difficult for students to master by a panel of engineering educators. Five separate inquiry-based activities (two physical experiments and three computer simulations) were developed and tested for their effectiveness at producing conceptual change during a 4-year study. Students’ conceptual change was assessed with concept inventories used in a pre-test–post-test design. The research examined students’ ability to answer conceptual questions both directly coupled with the developed activity and questions that required students to apply the targeted concept in new contexts. These assessments were done both immediately after the activity and 10 weeks later. Students’ performance generally improved in all areas, suggesting that the activities were effective for promoting conceptual change.     

On the modeling of phase and chemical equilibria by equations of state for systems containing supercritical components and ionic species

A technique of modeling of phase and chemical equilibria by equations of state for systems containing supercritical components and ionic species is considered. Attention is focused on the structure of equation of states with inclusion of non-electrolyte and electrostatic contributions. A hole quasichemical model was applied to illustrate the technique and to show how an EOS can be modified for systems with chemical reactions and electrostatic interactions in the liquid phase. The concentration dependency of the density and dielectric permittivity was taken into account in describing the electrostatic contribution that is required for thermodynamic consistency of the results of modeling. A method of assessing the appropriate relationships for mixtures containing supercritical components is suggested, alongside with the way to estimate the “true” composition of mixtures where ionic species are formed due to chemical reactions. The raised questions are discussed with respect to the following systems: solutions of acid gases in water-alkanolamine mixtures and water-ammonia-carbon dioxide system in a broad interval of temperatures and pressures.     

Modeling the influence of chemical reactions on the mechanisms of ionic transport in porous materials: An overview

This paper attempts to critically review various approaches developed to model the effects of chemical reactions on the mechanisms of ionic transport in porous media. A comprehensive overview of the various types of chemical reactions that can occur in reactive porous solids is first presented. Methods to model each of these chemical reactions are then described and analyzed. The ability of each of the proposed algorithms to predict the behavior of hydrated cement systems is discussed. The implementation of these algorithms in an ionic transport numerical model is also discussed.     

A facile chemical conversion synthesis of Sb2S3 nanotubes and the visible light-driven photocatalytic activities

ABSTRACT: We report a simple chemical conversion and cation exchange technique to realize the synthesis of Sb2S3 nanotubes at a low temperature of 90°C. The successful chemical conversion from ZnS nanotubes to Sb2S3 ones benefits from the large difference in solubility between ZnS and Sb2S3. The as-grown Sb2S3 nanotubes have been transformed from a weak crystallization to a polycrystalline structure via successive annealing. In addition to the detailed structural, morphological, and optical investigation of the yielded Sb2S3 nanotubes before and after annealing, we have shown high photocatalytic activities of Sb2S3 nanotubes for methyl orange degradation under visible light irradiation. This approach offers an effective control of the composition and structure of Sb2S3 nanomaterials, facilitates the production at a relatively low reaction temperature without the need of organics, templates, or crystal seeds, and can be extended to the synthesis of hollow structures with various compositions and shapes for unique properties.     

A versatile chemical conversion synthesis of Cu2S nanotubes and the photovoltaic activities for dye-sensitized solar cell

A versatile, low-temperature, and low-cost chemical conversion synthesis has been developed to prepare copper sulfide (Cu₂S) nanotubes. The successful chemical conversion from ZnS nanotubes to Cu₂S ones profits by the large difference in solubility between ZnS and Cu₂S. The morphology, structure, and composition of the yielded products have been examined by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction measurements. We have further successfully employed the obtained Cu₂S nanotubes as counter electrodes in dye-sensitized solar cells. The light-to-electricity conversion results show that the Cu₂S nanostructures exhibit high photovoltaic conversion efficiency due to the increased surface area and the good electrocatalytical activity of Cu₂S. The present chemical route provides a simple way to synthesize Cu₂S nanotubes with a high surface area for nanodevice applications.     

Waste water treatment using reverse osmosis: real osmotic pressure and chemical functionality as influencing parameters on the retention of carboxylic acids in multi-component systems

The influence of chemical functionality in carboxylic acids and osmotic pressure of multi-component solutions on the retention in the reverse osmosis process are discussed. Therefore formic-, acetic-, propionic-, glycolic-, acrylic- and methoxyacetic acid (target substances) were combined with one or two other carboxylic acids (active substances), chosen out of a pool of 16. All investigations were carried out with an aromatic polyamide membrane and the operating conditions were kept constant. Although the combination of all effects is extremely complex, the experiments showed that the influence on the retention of a substance equate as an outcome of molecular mass, acidity, functionality and spatial requirement. The influence of functionality in the active substances could be further divided into an additional carboxylic group, double bond and aromaticity. The calculation of the osmotic pressure demonstrated that there was no observable difference between the real and ideal one when the solution contained the same number of components. Therefore it can be concluded that in this study the osmotic pressure has no influence on the retention of the target substance.