Collaborative knowledge building using the Design Principles Database

In this study we describe a mechanism for supporting a community of learning scientists who are exploring educational technologies by helping them to share and collaboratively build design knowledge. The Design Principles Database (DPD) is intended to be built and used by this community to provide an infrastructure for participants to publish, connect, discuss and review design ideas, and to use these ideas to create new designs. The potential of the DPD to serve as a collaborative knowledge-building endeavor is illustrated by analysis of a CSCL study focused on peer-evaluation. The analysis demonstrates how the DPD was used by the researchers of the peer-evaluation study in three phases. In the first phase, design principles were articulated based on a literature review and contributed to the DPD. In the second phase, a peer-evaluation activity was designed based on these principles, and was enacted and revised in a three-iteration study. In the third phase, lessons learned through these iterations were fed back to the DPD. The analysis indicates that such processes can contribute to collaborative development of design knowledge in a community of the learning sciences. Readers of ijCSCL are invited to take part in this endeavor and share their design knowledge with the community.     

Axial crushing of hollow and foam filled tubes: An overview

Herein, a detailed review of the past studies carried out on crushing and energy absorption behaviour of hollow and foam filled tubes under axial compression is presented. Importance of such investigation is discussed for understanding the research need and to develop suitable alternatives. The focus of review is the deformation mechanism and energy absorption of hollow circular and square tubes, foam filled circular and square tubes notably. Comprehensive review on the various deformation modes for these tubes under axial impact load and effect of foam filling is presented. The review includes the various parameters affecting the peak load and energy absorption. Although various other forms of energy absorbing materials and structures exist such as composites, multi-wall tubes and honeycombs, these are not within the scope of present review. This paper intends to provide assistance in design and development of empty and foam filled tubes as effective energy absorbers. Further, this paper provides the necessary information for designers to understand the deformation of such tubes.     

New shakedown criterion and permanent deformation properties of unbound granular materials

Railway Engineering Science - Unbound granular material specifications for road pavements in Australia are primarily based on physical material specification rather than mechanical...     

Determination of very toxic metal — Cadmium in natural water samples

A potentiometric stripping method for a direct measurement of cadmium in various natural water samples using a Stripping analyzer M1 (designed and manufactured in Serbia) unit has been developed. In order to ascertain optimum conditions for the determination of the effect of the mercury time electrodeposition, the electrolysis potential and the solution stirring rate of the cadmium analytical signal have been examined. Linearity of the cadmium analytical signal was achieved within the wide range of the mass concentrations, from 1 μg/L to 15 μg/L. A detection limit of 0.10 μg/L was obtained, with a reproducibility of 3.55% expressed as the coefficient of variation. The accuracy of the method was confirmed by parallel analyses by flameless atomic absorption spectrophotometry as the reference method.     

Comparative Study on Microstructural Characteristics and Compression Deformation Behaviour of Alumina and Cenosphere Reinforced Aluminum Syntactic Foam Made Through Stir Casting Technique

In order to examine the effect of microballoons type on microstructure and compressive deformation behaviour of aluminum syntactic foam, alumina reinforced and cenosphere reinforced aluminum syntactic foams have been made through stir-casting technique. Alumina microballoons reinforced aluminum syntactic foam (AMRASF) has been developed using stir casting technique. Volume fraction of alumina microballoons in AMRASF varies in the range of 0.39–0.74. The compressive deformation behavior of these AMRASF is compared with that of cenosphere reinforced aluminum syntactic foam (CPRASF). The AMRASF does not exhibit clear plastic collapse stage as observed in case of CPRSAF. It is further noted that AMRASF shows the existence of work hardening phenomena after yielding but CPRASF does not show any significant work hardening after yielding even at higher relative densities of foam. This is explained on the basis of characteristics of alumina microballoons and cenospheres and interface characteristics between matrix and respective microballoons used. Effect of individual microballoons’ characteristics on the foam properties has also been explained.     

Deep eutectic solvents: designer fluids for chemical processes

The increasing demand for multi‐task green solvents has spurred the development of next‐generation liquid media such as deep eutectic solvents (DESs), which have recently attracted increased attention. DESs are mixtures of salts and complexing agents, having freezing points lower than those of starting individual components. Similarly to ionic liquids, DESs exhibit distinctive properties such as chemical and thermal stability, biodegradability, non‐flammability, and cost effectiveness. These features account for their wide range of applications, e.g. as extractants, reactants, catalysts, reaction media, additives, and lubricants. This review summarizes the recent research efforts directed at exploring the potential applications of DESs in various chemical processes. With the rapid publication of reports on this new generation of solvents, other roles also are expected to be seen sooner or later. © 2017 Society of Chemical Industry     

废发动机油的分析与添加剂方法再生可行性研究

2010年中国汽车保有量达5500万辆,按照每车年更换一次润滑油5L计算,年产生废润滑油2.7亿升,这笔巨大的可再生资源,如果不被合理利用,将对环境产生严重的危害。分析研究5组牌号的新、废汽油发动机润滑油,在对其总酸值、油中的元素含量、污染度、摩擦学性能测试的基础上,对比废油与新油各种性能的差异以及元素含量的变化,分析废润滑油各种元素变化与添加剂的相关性。研究结果表明:与新油相比,废发动机润滑油的酸值明显上升,颗粒污染度增大,其原因是极压添加剂、分散剂等添加剂消耗和摩擦化学反应的氧化作用,以及摩擦副材料的磨损及其与润滑添加剂的化学作用;极压添加剂元素消耗和污染度增大导致废发动机润滑油较同牌号新油抗极压性能降低、磨斑直径增大以及摩擦因数增大;所测试的废发动机润滑油都还具有一定量的原始添加剂成分和承载、耐磨、减摩润滑的功能,有可能通过过滤污染颗粒(氧化产物等)、补充再生添加剂和分散剂的方法,即再生添加剂方法,使其再生利用。     

Two-phase lattice Boltzmann simulation of natural convection in a Cu-water nanofluid-filled porous cavity: Effects of thermal boundary conditions on heat transfer and entropy generation

The present work investigates the effect of four different thermal boundary conditions on natural convection in a fluid-saturated square porous cavity to make a judicious choice of optimal boundary condition on the basis of entropy generation, heat transfer and degree of temperature uniformity. Four different heating conditions- uniform, sinusoidal and two different linear temperature distributions are applied on the left vertical wall of the cavity respectively, while maintaining the right vertical wall uniformly cooled and the horizontal walls thermally insulated. The two-phase thermal lattice Boltzmann (TLBM) model for nanofluid is extended to simulate nanofluid flow through a porous medium by incorporating the Brinkman–Forchheimer-extended Darcy model. The close agreement between present LBM solutions with the existing published results lends validity to the present findings. The current results indicate that the uniform and bottom to top linear heating are found to be efficient heating strategies depending on Rayleigh number (10³?≤?Ra?≤?10⁵) and Darcy number (10^?1?≤?Da?≤?10^?6). It is observed that the nanofluid improves the energy efficiency by reducing the total entropy generation and enhancing the heat transfer rate although its augmentation depends on the optimal volume fraction of nanoparticles.     

Development of a nonaqueous solvent system for poly(vinyl alcohol) and its characterization

Solubility of poly(vinyl alcohol) (PVA) in water prevents the preparation of various derivatives through homogeneous techniques as most of the derivatives thus formed are insoluble in aqueous medium. There are a number of solvents that can swell PVA under hot conditions but cannot dissolve PVA. In the present study, N,N‐dimethyl acetamide (DMAc) has been identified as solvent in which PVA can be dissolved in the presence of an equimolar amount of lithium chloride (LiCl). ¹H nuclear magnetic resonance (¹H‐NMR), ¹³C‐NMR, infrared (IR), and X‐ray diffraction (XRD) studies have been carried out to characterize the regenerated poly(vinyl alcohol) (RPVA). DMAc–LiCl is found to be a true solvent system for dissolution of PVA. An attempt has also been made to prepare poly(vinyl acetate) from this solution of PVA by a homogeneous technique. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 663–669, 1999