Thermodynamic approach to the vaporization and growth phenomena of SiC ceramics. II. The SiC surface under oxidative conditions

Thermodynamic conditions at the SiC surface under oxygen pressure are analyzed from two points of view: (i) the conditions for creation of a first layer of silica and (ii) the conditions for carbon precipitation. The active to passive oxidation transition steady-state is studied using a thermodynamic analysis focused on the chemical potential of silicon and oxygen at the surface of the compound in order to ensure the existence of a clean SiC surface, i.e. a flow balance imposed simultaneously for the Si and C vaporization flows Si/C = 1/1 at the surface. Thermodynamic calculations show that there exists a window in the couple as a function of temperature that corresponds to a bare SiC surface. For such prevailing conditions the SiC erosion flows are calculated as well as the related SiC condensation phenomenon that might explain the SiC transport and vapor phase deposition at high temperature.     

A retrospective analysis on the impacts of an immersive digital environment on chemical engineering students’ moral reasoning

Process safety decision making in chemical engineering practice has a strong ethical and moral component. While effective process safety decision making can be taught, it is not solely a technical topic, and includes complex behavioral elements that classroom-based instruction finds difficult to capture. To capture the complexity of this decision making, we have developed a digital immersive environment, Contents Under Pressure (CUP), that includes both technical and behavioral elements. This immersion allows participants to explore realistic process safety decision points in a safe environment. To determine the effect of CUP on moral reasoning, a retrospective study of two cohorts was conducted. The first cohort (n = 109) received traditional process safety instruction, and the second cohort (n = 181) had CUP included as part of their instruction. Pre- and post-assessment of participant process safety reasoning was achieved via the Engineering Process Safety Reasoning Instrument (EPSRI), also developed by the authors. Analysis of the data suggests that exposure to CUP has a distinct and statistically significant impact on process safety reasoning as compared to the comparison cohort.     

Prediction of partition coefficients using COSMO-RS: Solvent screening for maximum conversion in biocatalytic two-phase reaction systems

Many biocatalytic reaction systems are biphasic with a reactive and an immiscible non-reactive phase. The reactive, mostly aqueous phase provides a natural enzyme environment and the non-reactive phase serves for delivery of dissolved substrates at high concentrations and for extraction of products. The proper choice of the non-reactive phase will have manifold influence on the catalytic parameters, such as activity, selectivity, and stability, but also on the maximum obtainable conversion or yield.

Conversion or yield constitutes a concise target of practical relevance for rational solvent screening which requires thermodynamic information on coupled reaction and phase equilibria as input information. As long as the reactive phase is kept constant, only the partition equilibrium of each solute in any solvent combination has to be determined. The experimental determination of these data requires a considerable laboratory effort. Therefore, an in-silico screening of solvents for maximal conversion of alcohol dehydrogenase-catalysed oxidoreductions of prochiral ketones was evaluated. COSMO-RS was used for the prediction of solute partitioning between organic solvents and aqueous reaction medium.

Although significant absolute deviations were found, COSMO-RS still predicted the correct trends for the partition coefficients of solutes in different solvents. The calculated overall reaction equilibrium using these partition coefficients again resulted in the prediction of the correct best solvent regarding conversion.     

A detailed anatomy of students’ perception of engagement and their learning a threshold concept in core chemical engineering

An attempt has been made to reveal a detailed anatomy of students’ self-perceived engagement with material in a lecture and their learning of a key course threshold concept. A cohort of 80 students in a third year chemical engineering (64% response rate) course voluntarily recorded their engagement using a Likert-type scale at intervals of 5 min in a (nominally 50 min) lecture, together with written comments. Marks were awarded for a substantial, follow-up summative assignment to test their understanding of the threshold concept. It was found students were highly unaligned in their level of engagement with the lecture. A key reason was that individuals’ engagement varied highly significantly during the lecture. Six engagement styles were identified. Some 33% exhibited Type 1 (engage strongly at the start and slowly disengage) and 23% exhibited Type 2 (remain at a more or less fixed engagement). Significantly, there was no correlation between students’ engagement scores and marks awarded; in particular there was no correlation with specific lecture intervals in which material was identified as most important. Further, there was no correlation between the number of written comments made by an individual and their marks. It is concluded that student self-perceived engagement is not a good predictor of learning as assessed by marks awarded on a summative assignment. It is not known whether student engagement is predicated on particular lecture material and type of lecturer, or other contributing factors. The experimental design could be readily widely applied.     

Lignin oxidation to generate vanillin: An integrated learning project for chemical engineering students

This paper presents an integrated learning project of 8 months duration, suitable for chemical engineering students entering their First year of major concentration. This project prepares students for a career in chemical engineering and aids their performance in multi-task problem solving using a teamwork approach. In the process, they develop essential competences, such as communication, perseverance, time management, and autonomy.     

Modeling the protein partitioning in aqueous polymer two-phase systems: influence of polymer concentration and molecular weight

Aqueous polymer two-phase system provides a powerful method for separation and purification of biomaterials. Among various factors, polymer concentration and polymer molecular weight are essential and have strong impact on the protein partitioning in these systems. Based on the modified Pitzer's model, a simple expression has been obtained for correlating protein partitioning in aqueous polymer two-phase systems with varying polymer concentration and different polymer molecular weights. Using only one group of parameters for each target protein, the partition coefficients of five proteins (lysozyme, chymotrypsinogen-A, bovine serum albumin, transferrin and catalase) in 16 sets of polyethylene glycol (PEG)/dextran systems were correlated. In addition, partition behavior of lactate dehydrogenase in PEG/hydroxypropyl starch systems were measured, correlated and partially predicted. A comparison of calculated and experimental data indicated that the model provides good correlation and prediction abilities on the protein partitioning in aqueous polymer two-phase systems with a wide range of polymer concentration and molecular weight.     

Assessing the impact of augmented reality application on students’ learning motivation in chemical engineering

Application of augmented reality (AR) in education has recently grown in interest due to distant, online, and self-directed learning. In this study, the impact of implementing an AR application on chemical engineering students’ learning motivation and performance was assessed. Two interactive AR lessons on common industrial equipment (i.e., centrifugal pump and shell-and-tube heat exchanger) were developed on the EON-XR platform. A cohort of 50 undergraduate chemical engineering students participated in the AR lessons and evaluated its impact on students’ learning motivation and usefulness as a learning resource. The level of students’ learning motivation was assessed with a 16-item questionnaire based on the Instructional Materials Motivation Survey (IMMS) from Keller’s ARCS model, and qualitative questions related to the future of AR technology in chemical engineering education. Results show that 82% of respondents found AR lessons helpful compared to conventional lesson delivery modes, while 92% were supportive for AR lessons to be an additional resource to existing learning materials. These findings demonstrated that AR technology impacted students’ learning motivation positively across multiple constructs, namely ‘Attention’, ‘Relevance’, ‘Confidence’ and ‘Satisfaction’ and showed great potential as an innovative pedagogical advancement in chemical engineering education.     

热力学及热力学参数状态图在SiAlON材料合成中的应用

热力学和热力学参数状态图在材料的合成和设计中起着重要的理论指导作用。文中对其基础理论知识进行了概述,重点讲述了它们在确定碳热还原氮化法合成O’SiAlON粉及热压烧结合成βSiAlON-15R复相材料的工艺条件和温度制度中的应用,并对其应用前景进行了展望。     

Equilibrium relationships for non-equilibrium chemical dependencies

It is shown that equilibrium constants determine the time-dependent behavior of particular ratios of concentrations for any system of reversible first-order reactions. Indeed, some special ratios actually coincide with the equilibrium constant at any moment in time. This is established for batch reactors, and similar relations hold for steady-state plug-flow reactors, replacing astronomic time by residence time. Such relationships can be termed time invariants of chemical kinetics.     

Melt Rheological Properties of Silver-Powder-Filled Polypropylene Composites

The melt rheological properties of titanate coupling-agent-treated particulate silver powder (varying from 0 to 5.6 vol% of Ag) were investigated. The effect of filler concentration on shear stress, shear rate, melt viscosity, and melt elasticity parameters were determined by using a piston-type capillary rheometer. The study shows that the materials follow a power law in viscous behavior over the entire range of shear rates and temperatures investigated. The melt viscosity decreases with filler content up to 4.1% and increases with a further increase in filler content. Interestingly, the viscosity of the composition was lower than that of unfilled polypropylene. The melt elasticity decreases with an increase in Ag content in the composites up to 4.1%; beyond that, it increases. The effect of temperature on the viscoelastic properties of filled polypropylene was also investigated.     

Curricular and pedagogical challenges for enhanced graduate attributes in CAPE

The purpose of this paper is to raise important issues in the area of CAPE education in the face of contemporary changes in knowledge development, information and communication technology advances and the practice of professional engineering. The paper does not seek to prescribe specific solutions but considers curriculum design principles that can help address the challenges faced by educators, professional and industry partners in developing graduate attributes within the CAPE domain. It is provided as a catalyst for further discussion and action on this important educational challenge.We discuss a range of important drivers for enhancing CAPE learning and teaching within the context of shifts in engineering practice and important developments in information and communication technologies. Effective development of graduate attributes in the CAPE domain requires innovative, unified curricula and pedagogies that centre on a range of learning strategies, the clever use of technology, collaborative learning spaces and authentic learning experiences. CAPE activities must be contextualized within systems-based courses in the curriculum and those courses must have a cohesive structure and justifiable learning progression. Such strategies can engage learners in situations and tasks that address a range of learning goals such as domain awareness and knowledge through to the deeper aspects of analysis, synthesis and evaluation – all aided by computer based methods.A review is made of the current trends in professional engineering activities across the product and process life cycle. These activities provide an important set of drivers for enhanced CAPE learning and teaching in engineering education. These considerations are coupled with an examination of approaches to curriculum design that sketch out important learning pathways, knowledge integration and pedagogies that must be considered in order to address and enhance the graduate outcomes in the CAPE education domain.We must adopt similar principles used within the application of process systems engineering to design and implement the educational environment for CAPE.