Indentation Studies on Y2O2-Stabilized ZrO2: I, Development of Indentation-Induced Cracks

The development of Vickers indent-induced tracks with increasing indent load has been studied in two Y₂O₃-stabilizel ZrO₂ ceramics. Such cracks form as radial or Palmqvist cracks at low loads, assume "kidney" shapes at intermediate loads, and finally form median (half-penny) cracks at high loads. The plastic zone directly beneath the indent is uncracked; a significant portion of the plasticity induced by indentation occurs by martensitic transformation.     

Modelling the linear viscoelastic rheological properties of bituminous binders

An extensive literature review on the modelling of the linear viscoelastic (LVE) rheological properties of bitumen over the last six decades is presented in this paper. The use of reliable models can, in general, be considered as a valuable alternative tool for estimating the LVE rheological properties of bitumen. These properties are normally presented in terms of complex modulus and phase angle master curves at a particular reference temperature. The review in this paper consists of three nonlinear multivariable models, 13 empirical algebraic equations and four mechanical element approaches. The details as well as the advantages and disadvantages of the models are discussed. In general, all the models are able to predict the LVE rheological properties of unmodified bitumen as well as follow the time–temperature superposition principle (TTSP). However, the observations suggest a lack of agreement between predicted and experimental LVE rheological properties for materials that contain a phase transition, such as found for highly crystalline bitumen, structured bitumen with high asphaltenes content and highly modified bitumen.     

An observation on the initiation of micro-pitting damage in as-ground and coated gears during contact fatigue

The effect of surface features on as-ground gears and the influence of BALINIT^® C and Nb–S coatings on the initiation of micro-pitting damage have been examined in case-carburised and tempered S156 steel helical gears subjected to contact fatigue using back-to-back gear testing. The initiation of micro-pitting damage has been studied using scanning electron and optical microscopy examination. It has been observed that micro-cracks tend to initiate against the sliding direction preferentially from micro-valleys on the surface of as-ground gears, particularly when the depth of micro-valley is favourably oriented at an angle against the sliding direction. It has been found that the micro-pitting damage is drastically reduced in both coated gears. In BALINIT^® C coated gears, the micro-scale surface irregularities are removed by a wear process resulting in a polished surface of the gear flank below the pitch diameter which is attributed to the effect of hard BALINIT^® C coating. However, there is region of interface between the polished and unpolished regions of gear flank where there is small scale initiation of micro-pitting due to the absence of BALINIT^® C coating at micro-valleys. In Nb–S coated gears, the coating tends to penetrate and fill-up the micro-valleys on as-ground surface modifying the gear flank surface. Hence, the micro-pits tend to initiate only at some micro-valley sites where the Nb–S coating is locally removed during running. This study shows that, both BALINIT^® C and Nb–S coated gears show enhanced resistance to micro-pitting damage by removing localised stress concentration at micro-valleys present on as-ground gears.     

Solid Freeform Fabrication of Permanent Dental Restorations via Slurry Micro-Extrusion

A solid freeform fabrication procedure for human dental restorations via a slurry micro-extrusion process is described. A dental porcelain slurry is developed with pseudoplastic property and moderate viscosity, which permits the slurry to be extruded at low extrusion pressure and have good shape-keeping ability. A green tooth can be produced by this method directly from a CAD digital model in 30 min. The sintering shrinkage of the green tooth is uniform. The microstructure of the sintered tooth is identical to that made via the traditional dental restoration processes. This new dental restoration process presents potential to provide dental patients with better, faster, and less expensive service.     

Manufacturing knowledge management strategy

The study sought to understand the components of knowledge management strategy from the perspective of staff in UK manufacturing organizations. To analyse this topic, we took an empirical approach and collaborated with two manufacturing organizations. Our main finding centres on the key components of a knowledge management strategy, and the relationships between it and manufacturing strategy and corporate strategy. Other findings include: the nature of knowledge in manufacturing organizations; the relevance of (in)formal processes; top-down and bottom-up communication; taking ownership for information processes. We also make comments on the development of action plans for better knowledge management. The implications are that, for an integrated approach to knowledge management strategy in manufacturing organizations, involvement across the organization and at all levels is necessary.     

Charge carrier mobility through vacuum–sublimed glassy films of s-triazine- and carbazole-based bipolar hybrid and unipolar compounds

Instead of physical mixtures as bipolar charge transport media for organic electronics, chemical hybrids comprising non-conjugated spacers are explored to strive for miscibility and morphological stability. Bipolar TRZ-3Cz(MP)2 and TRZ-1Cz(MP)2 as well as unipolar C3-2TRZ(2tBu), C2-2TRZ(2tBu) and C3-2Cz(MP)2 were synthesized with propylene or ethylene spacers serving to decouple the Cz(MP)2 and TRZ moieties. Glassy films were prepared by vacuum sublimation for the characterization of transport properties using the photocurrent time-of-flight technique. The results indicate that both the TRZ:Cz(MP)2 ratio and the spacer length enable charge-carrier mobility to be modulated across orders of magnitude. The C2-2TRZ(2tBu) film exhibits the highest electron mobility of all the unipolar TRZ-based glassy films reported to date.     

Radiation Damage in Type II Superlattice Infrared Detectors

The effects of 2 MeV proton irradiation on a set of four long-wave infrared type II superlattice photodiodes with various structures were studied. Changes were monitored in operating bias, quantum efficiency (QE), and dark current. Shifts in operating bias indicate that irradiation causes the superlattices to become more p-type, and decreases in QE are found to be consistent with a reduction in carrier lifetime. Leakage currents remain lower in graded-gap diodes at all fluences.     

Evaluating the perspectives for hydrogen energy uptake in communities: Success criteria and their application

In recent years, a number of initiatives have been supported in Europe in the hydrogen energy sector. Communities can play an important role in the adoption process of these emerging technologies: supporting pre-commercial deployment, building public acceptance, and promoting innovation clusters, all of which lay the foundations for more widespread and sustained technology deployment. Participation by communities is hinged on the perceived contribution of technology adoption to community socio-economic and energy related goals, such as, climate change mitigation, air quality improvement, creation of new industries and businesses, exploitation of abundant renewable resources, and meeting growing energy needs. Hydrogen uptake in communities therefore stands to benefit development of the hydrogen energy sector and the communities themselves. This paper presents a methodology for evaluating the potential for successful large-scale hydrogen and fuel cell technology adoption—beyond demonstration projects—within defined community frameworks. This methodology can be a valuable tool, for community decision-makers and industry stakeholders alike, to evaluate and identify opportunities for large-scale hydrogen technology adoption. Results of applying the methodology are presented for three community types: islands, cities and regions. The work in this paper reflects work done within the frame of the European Commission-funded ‘Roads2HyCom’ project, Work Package 3.¹     

Numerical Simulation of Unsteady Flows and Shape Oscillations in Liquid Droplets Induced by Deployment Needle Retraction

Retractable opposed needles are often used in reduced-gravity droplet combustion experiments to deploy droplets prior to ignition. Needle retraction induces droplet shape oscillations and internal flows that can have important effects on subsequent droplet behaviors. In the present paper, the unsteady flows and droplet shape oscillations associated with deployment needle retraction are investigated using the commercial CFD software package Fluent. A volume-of-fluid method with a second-order upwind scheme and a dual time stepping solver is employed to solve the conservation equations in 2-d and 3-d simulations of droplets prior to ignition. A moving-mesh method is employed to model needle movements. Calculations indicate that rapid needle retraction causes ligament formation between a droplet and a needle, with ligament breakage sometimes resulting in the formation of satellite droplets. Needle retraction also induces droplet shape oscillations that rapidly decay, though significant internal flows are predicted to remain within droplets even after droplet shape oscillations have damped to low levels. The calculations indicate that the initial needle spacing can have important effects on droplet shape oscillations and internal flow characteristics. Comparison of model predictions and experimental data is favorable.     

Partial least squares (PLS) regression for the analysis of instrument measurements and sensory meat quality data

The partial least squares (PLS) regression technique was used to examine meat quality data derived from instruments (including Warner-Bratzler shear force and Instron Compression) and sensory panels. The data related to beef longissimus dorsi muscles collected during trials to study the effect of hot boning on meat quality. The univariate analysis of tenderness showed that over 60% of the variation in sensory tenderness, and almost 60% of the variation in sensory acceptability, could be explained from instrument variables and a consideration of boning and ageing time. Graphical displays from the analysis indicated that hot boning (either at 1 or 4 h) had little effect on meat quality. Graphical displays demonstrated a possible important effect of vacuum-pack ageing on acceptability. For this data set, it appears that samples of approximately equivalent tenderness differ in acceptability, depending on whether the samples have been aged for 1 or 4 weeks. This finding may have practical importance in attempts to predict eating quality (acceptability) from instrument measurements. Separate equations are necessary for products aged for different periods. ?