Exploding pressure vessel test on zylon/epoxy composite

The efficiency of zylon/epoxy composites under radial load for the reinforcement of high-field magnet coils is studied using the exploding pressure vessel technique. Under the combined stresses in tangential and radial directions, the behaviour of zylon/epoxy composite is well described by the theory of orthotropic cylindrical shells when the pre-stress effects are considered. The ultimate tensile strength of the zylon/epoxy shell with a fibre-filling factor of 90% is found to be 4.8 GPa. The bursting pressure (maximal radial stress) is, for a given filling factor, a monotonically increasing function of the ratio of the shell thickness to inner radius. The beneficial effects of the pre-stress during winding on the reinforcement are discussed.     

Effect of CO in the anode fuel on the performance of PEM fuel cell cathode

Even trace amounts of CO in the fuel for a proton-exchange membrane fuel cell (PEMFC) could poison not only the anode, which is directly exposed to the fuel, but also the cathode, which is separated from the fuel by a proton-exchange membrane; and the performance decline of the cathode is sometimes more than that of the anode. Adsorption of CO on the cathode catalyst has been detected electrochemically, and this indicates that CO can pass through the membrane to reach the cathode. To reduce such a poisoning effect, fuel cell operation conditions (e.g. level of membrane humidification, gas pressure difference between cathode and anode), membrane and catalyst layer structures, and CO-tolerant cathode catalysts should be further explored.     

Dependence of microporosity formation on the direction of solidification

The aim of this paper is to suggest a new approach in the investigation of the effect of gravity on microporosity formation in solidification of binary alloys. Instead of traditional unidirectional solidification from the bottom, which involves solidification against the gravity, we suggest to carry out solidification from the top, which involves solidification along the gravity. Numerical modeling performed in this paper suggests an experimental study that compares the results of these two experiments, which potentially reveals some important data concerning the influence of gravity on microporosity formation and also could be used as a tool for validation of microporosity formation models.     

Surface remobilization of buoyancy-driven surfactant-laden drops at low reynolds and capillary numbers

It is well known that the terminal velocity of a drop settling in a viscous fluid is impacted by surface tension gradients. These gradients can develop because of nonuniform accumulation of surfactant on the surface as a result of a number of transport mechanisms. Here, a surfactant transport model based on a sorption-limited Frumkin framework is used to describe surfactant transport in the presence of both surface convection and diffusion at low Reynolds and capillary numbers. Constants characterizing surfactant transport in the Frumkin framework are experimentally determined and used to predict aqueous drop velocities with varying surfactant concentrations and volumes. Computation is carried out by satisfying equations governing mass, momentum, and interface species conservation. Experiments demonstrate qualitative and quantitative agreement between predicted and measured drop velocities. It is shown that surface remobilization explains some observed trends in measured velocity as the drop size decreases. © 2018 American Institute of Chemical Engineers AIChE J, 65: 294–304, 2019     

Concrete–ice abrasion mechanics

The mechanisms of abrasion of concrete by ice are investigated by review of lab and field studies, wear theory, fracture-, contact- and poromechanics. Experience indicates that ice abrasion does not require freeze/thaw cycles. Three distinct mechanisms may contribute to abrasion damage of concrete: (1) asperities of ice sliding on concrete can create tensile stresses sufficient to initiate cracks (with fatigue from repeated contacts playing an important role); (2) debris released from the surface of the concrete can act as sharp abrasive particles that enhance the damage as the ice drags them along the surface; and (3) water forced into surface defects can create pressure that propagates cracks. Topics for further research and recommendations for minimizing abrasion are suggested.     

An improved iterative stochastic multi-objective acceptability analysis method for robust alternative selection in new product development

Alternative selection in new product development (NPD) is a multi-criteria decision-making (MCDM) problem. It usually starts with incomplete, imprecise or even partially missing information. Currently, most existing methods in dealing with this problem cannot work well if required information is incomplete or missing. It is acknowledged that stochastic multi-objective acceptability analysis (SMAA) can be applied to address MCDM problem with incomplete preference information and uncertain criteria measurements. In SMAA, alternatives are evaluated based on SMAA measurements (acceptability index, central weight vector and confidence factor). The discriminability of SMAA for the optimum alternative heavily depends on differences of SMAA measurements among different alternatives. Usually, a large number of alternatives and high level of uncertainty are involved in alternative selection in NPD. In this situation, the differences among SMAA measurements are not obvious, and therefore SMAA cannot deal with such problem very well. To this end, this paper proposes an improved SMAA method called Iterative-SMAA (I-SMAA) for alternative selection in NPD. In the I-SMAA, an iterative multi-step decision-making process is suggested to improve differences of SMAA measurements among different alternatives, and thus assist decision makers (DMs) to positively discern from the most preferred alternative. To enhance the decision-making efficiency, sensitive criteria are acquired in each iteration by ranking sensitivity analysis. DMs are guided to provide partial preference information and give more accurate criteria measurements for sensitive criteria rather than all criteria. Eventually, to verify the proposed method, a numerical example of the existing literature is solved with the method, and the results are compared. And then, a practical example of a preparation equipment for coal samples is further employed to verify the practicability of the proposed I-SMAA.     

Structural performance of ballastless track slabs reinforced with BFRP and SFCB

Because of the inductive impedance caused by steel meshes in traditional reinforced ballastless track slabs, the electrical properties, primarily the rail resistance and inductance, of jointless track circuits are affected by electromagnetic induction between the slabs and the electric current in the rail. This problem results in poor transmission performance throughout the track circuit. Insulating sleeves or cards between the steel meshes have been used to improve the insulation capability of steel meshes in slabs; however, they reduce the bonding performance between the steel bars and concrete. Because of the good insulation properties of fiber-reinforced polymer composite bars (FRPs) and steel-fiber reinforced polymer composite bars (SFCBs), these composite materials have shown potential to overcome this insulation problem. However, the structural performance of the ballastless track slabs reinforced by basalt fiber reinforced polymer composite bars (BFRPs) and SFCBs, which play a key role in the structure and transportation safety, needs to be investigated. In this paper, six ballastless track slabs reinforced with BFRPs, SFCBs, and steel bars were constructed and tested. The following results were obtained. (1) Shear failures were observed for all slabs, both the BFRP and SFCB slabs meet the load level requirements, and SFCBs reinforcements have higher strength utilization compared with BFRPs reinforcements. (2) The bond-quality of SFCBs and BFRPs reinforcements proved slightly poorer than that of the steel bars. Because of the good corrosion resistance of the FRP, the maximum crack width limits can be slightly larger than that of the RC slabs. (3) Bischoff’s equation was initially used to calculate the deflection of partially prestressed concrete slabs under service loads. The results demonstrated a good agreement between the theoretical and experimental analysis. (4) Considering the tensile stiffness, the modified ACI equation was used to calculate the slabs’ crack width and the theoretical and experimental results showed a good agreement.     

Mining urban data (part A)

Modern cities are flooded with data. New information sources like public transport and wearable devices provide opportunities for novel applications that will improve citizens׳ quality of life. From a data science perspective, data emerging from smart cities give rise to a lot of challenges that constitute a new inter-disciplinary field of research. This article introduces the first part of a special issue on the topic ‘Mining Urban Data’ published in the journal Information Systems.     

Molecular design for thermally stable SiZrBOC structure from single source precursor with high ceramic yield

A new type of high-temperature-resistant SiZrBOC ceramics was prepared by sol-gel method using polymethyl-hydro siloxane (PMHS), boric acid (B(OH)₃), and n-propyl zirconate (Zr(OPr)₄) as raw materials. After high-temperature pyrolysis, the SiZrBOC precursor was transformed into a crystalline ceramic material with a yield of 89.5 wt%. Fourier infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) were applied to characterize the polymer-ceramic conversion process and thermal behavior of ceramic precursors. According to the results, the addition of boron elements led to the formation of Si-O-B links in the system. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the phase composition and microstructure of SiZrBOC ceramics. Finally, the oxidation test at 1200 °C revealed that SiZrBOC ceramics with a boron/zirconium molar ratio of 2.5:1 exhibited the best oxidation resistance at a weight gain of 0.4 wt% only.