Dramatic Drop in Cell Resistance through Induced Dipoles and Bipolar Electrochemistry

The use of slurries of conducting particles has been considered a way to extend the electrode area in some energy storage electrochemical cells. When suspensions of conducting particles are used in electrolytes a decreased impedance is observed, even for concentrations much lower than the theoretical percolation limits. Indeed, it is known that polarization occurs when a conducting material is immersed in an electrolyte in presence of electric fields, and bipolar electrochemistry processes may occur. This work demonstrates the dramatic drop in resistance for electrochemical cells with just a few macroscopic conducting pieces immersed in the electrolyte, in the absence of any electrical contact, through bipolar induction. Furthermore, mediation of soluble redox species between adjacent induced poles of opposite charge results in an additional mechanism for charge transfer, contributing further to the decrease in impedance. Relevant parameters like size, geometry, and spatial occupation of inducible pieces within the electric field, are relevant. Remarkably, the effects observed can explain some empirical observations previously reported for carbon suspensions and slurries. Thus, no electronic percolation requiring particle contact, nor ordering, are needed to explain the good performance associated to lowered impedance These results suggest new engineering designs for electrochemical cells with enhanced currents

Failure and Improvement in Elementary Engineering

Recent science education reform documents in the United States have called for teachers to teach content related to engineering and science and to do so by engaging students in disciplinary practices. One important practice of engineering is improving from failure. Thus, students should experience productive failure as part of engineering design activities. However, engineering is a new subject for most elementary teachers. Historically failure has had negative connotations in elementary and precollege classrooms. To scaffold students through failure as they learn from and improve engineering designs, teachers will need to understand failure and pedagogical strategies for managing it. This study uses discourse analysis of video from eight elementary classes engaged in engineering to examine the nature of failure in engineering design projects. It also investigates how the collective actions of students and teachers support or constrain the process of improvement from engineering design failure. From these data, we propose a model of improvement through failure. This includes a classification of types and causes failure as well as facilitating conditions that must be present for improvement. We explore three features of engineering and three features of classroom cultures that contribute to learning to engage in productive failure.

Families’ engagement in making activities related to aerospace engineering: designing for parents as learning partners in pop-up makerspaces

Purpose The researchers conducted a collective case study to investigate how families engaged in making activities related to aerospace engineering in six pop-up makerspace programs held in libraries and one museum. The purpose of this paper is to support families’ engagement in design tasks and engineering thinking, three types of discussion prompts were used during each workshop. The orienting design conjecture was that discussion prompts would allow parents to lead productive conversations to support engineering-making activities. Design/methodology/approach Within a collective case study approach, 20 consented families (22 adults, 25 children) engaged in making practices related to making a lunar rover with a scientific instrument panel. Data included cases of families’ talk and actions, as documented through video (22 h) and photographs of their engineering designs. An interpretivist, qualitative video-based analysis was conducted by creating individual narrative accounts of each family (including transcript excerpts and images). Findings Parents used the question prompts in ways that were integral to supporting youths’ participation in the engineering activities. Children often did not answer the astronomer’s questions directly; instead, the parents revoiced the prompts before the children’s engagement. Family prompts supported reflecting upon prior experiences, defining the design problem and maintaining the activity flow. Originality/value Designing discussion prompts, within a broader project-based learning pedagogy, supports family engagement in engineering design practices in out-of-school pop-up makerspace settings. The work suggests that parents play a crucial role in engineering workshops for youths aged 5 to 10 years old by revoicing prompts to keep families’ design work and sensemaking talk (connecting prior and new ideas) flowing throughout a makerspace workshop.

Determination of the Topography and Draining of the Site for the Benin City Bus Rapid Transit (BRT) Station

The reconciliation of engineering designs that do not have survey information, that involve accurate configuration of the proposed constructions at their respective locations on-site requires first a topographic survey to obtain the perimeter survey plan, which in turn, shows the area, shape, perimeter and orientation of the site; spot heights plan showing the existing ground levels thereby used to decide on suitable gradients and determine appropriate finished ground surface, coordinates of the turning points of outlines of the proposed constructions and their respective elevations. For that reason, this study determines the topography and drains the site for the Benin City Bus Rapid Transit (BRT) station in Oredo Local Government Area of Edo State. A topographic survey was carried out to produce topographic plans. The accuracy of the survey was computed to determine its reliability. The perimeter survey plan was plotted using AutoCAD Civil 3D Land Desktop Companion 2009 to present the area, shape, perimeter and orientation of the site. The TIN method was used for the computation of the volume of earthworks. The existing and the finished ground surfaces, vector, as well as the flow direction plans, contour plans and the 3D surface maps were plotted using Surfer 11 to show graphically the existing and the proposed topography of the site. A network of drainages was established to drain the site. The study has shown that the site can be drained in two ways, into the moat behind it and existing drainage along Obakhavbaye.

Scaling, Complexity, and Design Aspects in Computational Fluid Dynamics

With the availability of more and more efficient and sophisticated Computational Fluid Dynamics (CFD) tools, engineering designs are also becoming more and more software driven. Yet, the insights in temporal and spatial scaling issues are still with us and very often imbedded in complexity and many design aspects. In this paper, with a revisit to a so-called leakage issue in sucker rod pumps prevalent in petroleum industries, the author would like to demonstrate the need to use perturbation approaches to circumvent the multi-scale challenges in CFD with extreme spatial aspect ratios and temporal scales. In this study, the gap size between the outer surface of the plunger and the inner surface of the barrel is measured with a mill (one thousandth of an inch) whereas the plunger axial length is measured with inches or even feet. The temporal scales, namely relaxation times, are estimated with both expansions in Bessel functions for the annulus flow region and expansions in Fourier series when such a narrow circular flow region is approximated with a rectangular one. These engineering insights derived from the perturbation approaches have been confirmed with the use of full-fledged CFD analyses with sophisticated computational tools as well as experimental measurements. With these confirmations, new perturbation studies on the sucker rod leakage issue with eccentricities have been presented. The volume flow rate or rather leakage due to the pressure difference is calculated as a quadratic function with respect to the eccentricity, which matches with the early prediction and publication with comprehensive CFD studies. In short, a healthy combination of ever more powerful modeling tools along with the physics, mathematics, and engineering insights with dimensionless numbers and classical perturbation approaches may provide a balanced and more flexible and efficient strategy in complex engineering designs with the consideration of parametric and phase spaces.

Lovina Beach landscape design in Buleleng Regency Bali based on landscape engineering

Lovina Beach is a famous tourist attraction on the northern island of Bali. This beach is somewhat unique because it has an exciting dolphin viewing attraction. However, some lack elements on-site reduce the value of beach tourism, such as unattractive design, many idle facilities, empty spaces, and puddle. This study aims to analyze and redesign the beach based on landscape engineering to overcome sustainability. The design stage consists of project acceptance, research and analysis, design, and construction drawings combined with the scoring system of the hydro-oceanographic analysis. The analysis aimed to identify the value of coastal vulnerability indexes. The results of this study are site plan concepts, perspective drawings, cut images, planting plans, and detailed engineering designs, which is formed on the results of analysis and synthesis, and preferences score. The design of this coastal waterscape will be used as a recommendation to the beach management.

Comparison of the Thermal and Electrical Conductivities of Pretreated Kenaf–Polyester Composites

Conductivity of a material is an important physical property that determines its suitability or otherwise in all engineering designs and construction. The aim of this study is to determine the effects of two pretreatment methods viz acetylation and permanganate on the thermal and electrical conductivities of pretreated kenaf bast fibres applied in polyester resin. Fully grown kenaf (hibiscus cannabalis) were manually retted from the stalk, washed, and cut into short fibre lengths of about 10 cm. One portion of the fibres was pretreated with 5%pbw NaOH solution before immersing it in glacial acetic acid and then in acetic anhydride. The second was also pretreated with5%pbw of NaOH before being pretreated with 0.125%of KMnO4. The third portion of fibres was untreated to serve as control. The ground fibre was incorporated into ortho unsaturated polyester rand cast with moulds of dumb-belland square shapes. The electrical conductivity of the composites was deduced by measuring the resistance of the composites using the high voltage insulation tester model 3122 and calculating from equations. The thermal conductivities were determined by analytical method. The results show that chemical pretreatments of fibres by acetylation and permanganate methods have no appreciable effect on the thermal conductivities of composites. Further findings show that the acetylated fibre composites have no effect on the electrical conductivities of the composites. The permanganate pretreated fibre composites however increased the electrical conductivities of the composites significantly.

CFD modelling of biomass catalytic fast pyrolysis in bubbling fluidized reactor: effects of catalyst parameters

In this study, a CFD mathematical model has been developed for catalytic fast pyrolysis (CFP) of biomass. The multi-phase fluid flow, and the inter-phase momentum and energy transfer processes were modelled with Eulerian multi-phase formulas. The biomass catalyst fast pyrolysis reactions were described by using a two-stage, semi-global model. Specified secondary tar catalytic cracking process, which considers both intrinsic reaction rates and mass transfer process are embedded to the developed model by user-defined function (UDF). The developed model has then been employed to investigate the effects of structural properties of catalyst, such as specific internal area, average size of active sites, pore diameter, and tortuosity, on products yields and composition. The influences of adsorption capability of tar molecule on catalyst surface and external film mass transfer were also analyzed. The developed model can be employed for further research and engineering designs of the catalyst pyrolysis of carbonaceous materials.

The Algal Chloroplast as a Testbed for Synthetic Biology Designs Aimed at Radically Rewiring Plant Metabolism

Sustainable and economically viable support for an ever-increasing global population requires a paradigm shift in agricultural productivity, including the application of biotechnology to generate future crop plants. Current genetic engineering approaches aimed at enhancing the photosynthetic efficiency or composition of the harvested tissues involve relatively simple manipulations of endogenous metabolism. However, radical rewiring of central metabolism using new-to-nature pathways, so-called “synthetic metabolism”, may be needed to really bring about significant step changes. In many cases, this will require re-programming the metabolism of the chloroplast, or other plastids in non-green tissues, through a combination of chloroplast and nuclear engineering. However, current technologies for sophisticated chloroplast engineering (“transplastomics”) of plants are limited to just a handful of species. Moreover, the testing of metabolic rewiring in the chloroplast of plant models is often impractical given their obligate phototrophy, the extended time needed to create stable non-chimeric transplastomic lines, and the technical challenges associated with regeneration of whole plants. In contrast, the unicellular green alga, Chlamydomonas reinhardtii is a facultative heterotroph that allows for extensive modification of chloroplast function, including non-photosynthetic designs. Moreover, chloroplast engineering in C. reinhardtii is facile, with the ability to generate novel lines in a matter of weeks, and a well-defined molecular toolbox allows for rapid iterations of the “Design-Build-Test-Learn” (DBTL) cycle of modern synthetic biology approaches. The recent development of combinatorial DNA assembly pipelines for designing and building transgene clusters, simple methods for marker-free delivery of these clusters into the chloroplast genome, and the pre-existing wealth of knowledge regarding chloroplast gene expression and regulation in C. reinhardtii further adds to the versatility of transplastomics using this organism. Herein, we review the inherent advantages of the algal chloroplast as a simple and tractable testbed for metabolic engineering designs, which could then be implemented in higher plants.