The social profitability of rural roads in a small open economy: Do urban agglomeration economies matter?

The effects of a rural roads programme depend on labour mobility, how the programme is financed, and agglomeration economies. If financed by a rural poll tax and cross-price effects and agglomeration economies are sufficiently small, the wage will rise, with some return migration. Taxes on trade act as countervailing distortions, yielding urban households some relief. Rural-urban commuting promotes the exploitation of agglomeration economies; taxes on international trade are then inferior to a poll tax. The change in the value, at producer prices, of the rural sector's net supply vector can be a poor measure of the programme's social profitability.     

Data-driven placemaking: Public space canopy design through multi-objective optimisation considering shading,structural and social performance

In the context of ongoing densification of cities and aging urban populations, public spaces are a crucial infrastructure to support the physical and mental wellbeing of urban residents. The design of public space furniture elements is often standardised, and not considered in relation to environmental conditions and mechanisms of social interaction. This article presents a digital workflow to generate site-specific designs for shaded public seating, considering the relationships of local public places to their surroundings. A strategy for customised and site-specific design is developed through the use of multiple software tools, employing evolutionary algorithms and multi-objective optimisation. The method is applied to a small public space canopy prototype installed within a public housing estate in Hong Kong, incorporating additional criteria to achieve a low-cost and light-weight structure. Through multiple stages of refinement and optimisation, a material, structural and social performance-driven outcome was achieved that creates a shaded space for public seating, people watching and social interaction. As part of a larger research agenda exploring architectural form-finding and environmental psychology, the project represents potential new applications in the emerging field of socially driven computational design.     

High permittivity BaTiO3 and BaTiO3-polymer nanocomposites enabled by cold sintering with a new transient chemistry: Ba(OH)2∙8H2O

Cold sintering process (CSP) offers a promising strategy for the fabrication of innovative and advanced high permittivity dielectric nanocomposite materials. Here, we introduce Ba(OH)₂?8H₂O hydrated flux as a new transient chemistry that enables the densification of BaTiO₃ in a single step at a temperature as low as 150 °C. This remarkably low temperature is near its Curie transition of 125 °C, associated with a displacive phase transition. The cold sintered BaTiO₃ shows a relative density of 95 % and a room temperature relative permittivity over 1000. This new hydrated flux permits the fabrication of a unique dense BaTiO₃-polymer nanocomposite with a high volume fraction of ceramics ((1-x) BaTiO₃ – x PTFE, with x = 0.05). The composite exhibits a relative permittivity of approximately 800, at least an order of magnitude higher than previous reports on polymer composites with BaTiO₃ nanoparticle fillers that are typically well below 100. Unique high permittivity dielectric nanocomposites with enhanced resistivities can now be designed using polymers to engineer grain boundaries and CSP as a processing method opening up new possibilities in dielectric materials design.     

Domain Wall Motion Across Various Grain Boundaries in Ferroelectric Thin Films

Domain wall movement at and near engineered 10°, 15°, and 24° tilt and 10° and 30° twist grain boundaries was measured by band excitation piezoresponse force microscopy for Pb(Zr,Ti)O₃ films with Zr/Ti ratio of 45/55 and 52/48. A minimum in nonlinear response was observed at the grain boundary for the highest angle twist and tilt grain boundaries, while a maximum in nonlinear response was observed at the 10° tilt grain boundaries. The observed nonlinear response was correlated with the domain configurations imaged in cross section by transmission electron microscopy.     

Tracking and characterizing the head motion of unanaesthetized rats in positron emission tomography

Positron emission tomography (PET) is an important in vivo molecular imaging technique for translational research. Imaging unanaesthetized rats using motion-compensated PET avoids the confounding impact of anaesthetic drugs and enables animals to be imaged during normal or evoked behaviour. However, there is little published data on the nature of rat head motion to inform the design of suitable marker-based motion-tracking set-ups for brain imaging—specifically, set-ups that afford close to uninterrupted tracking. We performed a systematic study of rat head motion parameters for unanaesthetized tube-bound and freely moving rats with a view to designing suitable motion-tracking set-ups in each case. For tube-bound rats, using a single appropriately placed binocular tracker, uninterrupted tracking was possible greater than 95 per cent of the time. For freely moving rats, simulations and measurements of a live subject indicated that two opposed binocular trackers are sufficient (less than 10% interruption to tracking) for a wide variety of behaviour types. We conclude that reliable tracking of head pose can be achieved with marker-based optical-motion-tracking systems for both tube-bound and freely moving rats undergoing PET studies without sedation.     

Modelling powder mixing in mass flow discharge: A kinematic approach

The dynamics of a powder flowing in a mass flow regime through a storage bin with a conical hopper, is a well studied problem. However, many challenges remain, including quantification of the mixing that occurs during discharge through the hopper. We have formulated a model based on the conservation of volume of the powder and a semi-empirical expression for velocity profile, (see [1], [2]), and used this to estimate mixing parameters. We have specifically considered the case of an inflow which is disposed in homogeneous horizontal layers as it enters the storage bin. When the powder, in successive layers, enters the hopper, it accelerates and its velocity along the longitudinal axis of the hopper is greater than at the walls. Portions of layers high in the hopper may overtake layers closer to the exit resulting in mixing of the layers. Using this model we are able to quantify the percentage of each layer in a given output volume and present results for typical hopper geometries.     

Microwave dielectric properties of (ABi)1/2MoO4 (A = Li,Na, K,Rb, Ag) type ceramics with ultra-low firing temperatures

A series of (ABi)_1/2MoO₄ (A = Li, Na, K, Rb, Ag) compositions were studied in regard to the sintering behavior, phase composition, microwave dielectric properties and chemical compatibility with silver and/or aluminum for electrodes. All the (ABi)_1/2MoO₄ (A = Li, Na, K, Rb, Ag) ceramics could be sintered below 700 °C with relative densities above 93%. Whereas the (KBi)_1/2MoO₄ ceramic can be sintered to a high density at around 630 °C/2 hrs with a relative permittivity ∼37, a Qf value of 4000 GHz and a temperature coefficient of resonant frequency (TCF) ∼ +117 ppm/°C. Furthermore, from the XRD analysis of co-fired ceramics, the (KBi)_1/2MoO₄ ceramic reacts with silver but not with aluminum at its densification temperature. The (ABi)_1/2MoO₄ (A = Li, Na, K, Rb, Ag) type ceramics can all be considered into the new field of ultra-low temperature co-firing dielectrics for multilayer applications.     

Microwave processing of electroceramic materials and devices

Microwave synthesis of nano-sized BaTiO₃ and decrystallized titania, and microwave sintering of electroceramics including BaTiO₃, Ba(Zn_1/3Ta_2/3)O₃ (BZT), lead zirconate–titanate (i.e. Pb(Zr _x Ti_1?x )O₃, or PZT), etc., as well as multilayer ceramic capacitors based on X7R, C0G, and ferrite multilayer chip inductors are presented. The results indicate that microwave processing significantly accelerated synthesis and sintering kinetics. As a result, processing time can be saved up to 90%, with the product properties comparable to or better than that of the conventional products.     

Measuring number‐concentrations of nanoparticles and viruses in liquids on‐line

BACKGROUND: The surge of studies on artificial and natural nanoparticles has revealed a new world for engineering and life sciences, but in most instances, the small scale has made their number‐concentration determination in liquids a challenging problem. Former success has mostly been limited to special particles measured by indirect techniques. A new approach is required for this determination to facilitate the production and application of nanoparticles in different systems. RESULT: Here, an approach is described using a nanoparticle tracking system based on Brownian motion, which can be used to determine the number‐concentration of nanoparticles, including viruses, in liquids on‐line. Extensive analysis showed the influence of suspension concentration and particle size on the accuracy of measurements. Natural nanoparticles of Adenovirus and several types of artificial nanoparticles, including precision nanobeads, uniform inorganic silica microspheres, monodisperse gold metal colloids and aggregated Aerosil nanoparticles, were measured and compared by counting the monitored particle number obtained using light scattered from individual particles, from which the particle number‐concentration, the product yield and the aggregation could be evaluated. CONCLUSION: This approach was compared with the mathematical calculation method and the emission spectrophotometry technique used for practical applications. The results showed this new approach had improved accuracy for determination of the particle number‐concentration. Copyright © 2010 Society of Chemical Industry