Methods for enhanced control over the density and electrical properties of SWNT networks

The formation of manufacturable electronic materials that incorporate single-walled carbon nanotubes (SWNTs) will most likely involve the use of networks of these molecular wires, due to the enhanced current drive and reproducibility of such films. Therefore, control over the density of SWNTs during the deposition of 2-D networks is of critical importance for the development of numerous enhanced electronic materials. Room temperature deposition methods are of particular interest as they allow separation, purification, and/or chemical modification of SWNTs before deposition. This article reports three iterative liquid-deposition techniques that allow control over the properties of three distinct types of SWNT networks. First, density control was obtained for 2-D networks of unbundled, high-aspect ratio SWNTs. Such networks exhibited semiconductive behavior, with tunable on/off ratios. Second, electrically continuous 2-D clusters of high aspect ratio SWNTs were formed by allowing capillary forces to develop in a sessile suspension droplet. These constructs displayed tunable metallic conductivity, and may have the applications as interconnects in microelectronics. Finally, highly conductive, 3-D networks of bundled SWNTs were formed via an evaporation method. For these three types of networks, the density of SWNTs, and thus the macroscopic conductance, was readily controlled via the number of deposition cycles used in their formation.     

Comparative studies on parametric sensitivity analyses using conventional and factorial design methodologies: mathematical modelling of clavulanic acid adsorption on zeolites

BACKGROUND: The main objective of this work was to evaluate the parametric sensitivity of model parameters of clavulanic acid (CA) adsorption in a stirred‐tank reactor using zeolites. The system sensitivity was evaluated in terms of mass transfer and hydrodynamic parameters using two methodologies. First, the sensitivity factors of input variables were evaluated according to a disturbance of ± 20% in the nominal parameter values; second, the factorial design methodology was employed. In both cases, the responses were obtained by means of model simulations. RESULTS: From the sensitivity analysis by experimental design, the best operational conditions for adsorption of CA on zeolites were solid to liquid percentage 7.0%, initial CA concentration 300 mg L^?1 and particle diameter 0.100 mm, which led to a reduction of 25 min in the adsorption time and 9% in the adsorption capacity, increasing the process productivity. CONCLUSION: The use of the factorial design had advantages compared with the conventional method because it provided information regarding the possibility of simultaneous changes in the factors investigated, enabling analyses of system sensitivity regarding operational parameters, as well as the choice of more suitable parameters. Copyright © 2012 Society of Chemical Industry     

Mechanical deformation of carbon-nanotube-based aerogels

We compare deformation behavior of conventional carbon and carbon-nanotube (CNT) based aerogels with monolith densities of 30–300 mg cm^?3. Results show that CNT-based aerogels have superior elastic moduli, comparable failure stresses, and, hence, lower failure strains. The density scaling law exponents are statistically indistinguishable for both types of aerogels, suggesting the same ligaments connectivity. The superior elastic properties and lower failure strains of CNT-based aerogels are attributed to a higher stiffness of CNT-based ligaments, while comparable failure stresses are attributed to the common junction geometry. Practical implications of these findings are discussed.     

Thermodynamics and local atomic arrangements of gold-nickel alloys

An e.m.f. apparatus with an oxygen-ion conducting solid electrolyte, differential thermal analysis, powder diffractometry, density measurements, and transmission electron microscopy (TEM) were used to determine thermodynamic quantities, the phase boundaries in the solid and liquid, and the microstructure of gold-rich solid solutions. Alloys with x_Ni = 0.03, 0.06, 0.10, 0.15, 0.21, 0.35, 0.55, 0.73, 0.87 and 0.93 were investigated. The thermodynamic activities deviate positively from Raoult's law in the liquid and solid states. The heats of formation and excess entropies exhibit positive values. This causes a large miscibility gap in the solid state. TEM, however, reveals short-range order in the alloys annealed above the miscibility gap.     

An ecological study of families in transitional housing – ‘housed but not homed’

This article discusses the sense of homelessness among nine homeless families who are in transitional housing in Singapore, where homelessness is minimal and mostly out of the public eye. This study is significant as it investigates homelessness experienced by married couples with children in Singapore, unlike most other research which has examined homelessness among singles or single-parent families, and which is based in Australia, Europe, and the US. The sense of homelessness was shaped by the ecological environment that comprised systemic elements such as kin support, housing policies, and non-housing policies like citizenship, education, welfare, and so forth. Homelessness was seen as (i) a loss of complete autonomy, control, privacy, and comfort; (ii) the lack of physical, practical, and emotional support from kin; (iii) a compromised ‘sense of family’ and family decisions; and (iv) hope and endurance while interacting with the ecological system.     

Industrially Harvested Peatlands and After-use Potential: Understanding Local Stakeholder Narratives and Landscape Preferences

Recent years have witnessed much debate on the turn towards community within landscape management and planning. This is particularly evident in the European Landscape Convention which asserts the legitimacy of local preferences and citizen involvement in policy processes. This paper explores a bottom-up perspective on people–place relationships in a changing landscape, through assessing the after-use potential of industrially mined peatlands in Ireland and the rehabilitation of degraded landscapes. The mining of the peatland resource has a longstanding tradition in Ireland, however, significant attention has now focused on exploring market and non-market uses of remains after harvesting has finished resulting in a cutaway landscape. We argue that local people's everyday experiences of the landscape is a legitimate form of knowledge and should provide a key input into deliberative planning and management processes. Drawing largely on an interpretive research approach, we assess key local narratives in relation to harvested peatland landscapes and explore local people's after-use preferences. There appears to be strong support among the local community for amenity/biodiversity after-uses, which are currently not reflected in public policy debates. We review people–place relationships and discuss the role of ethnographic research in a peatland context as well as defining the relevant stakeholders. Finally, conclusions are developed to identify wider lessons for people/place relationships within the context of landscape management and planning.     

Assessment of Durability and Long Term Performance of High Density Polyethylene Drainboards in the Gotthard Railway Tunnels

Drainage layers provide permanent relief of hydrostatic water pressure, while the waterproof liner prevents any ingress of water into the tunnel. The durability and aging resistance of drainage membranes are of primary concern. This paper describes advantages and concerns related to the usage of, and the design with, polymeric drainboards in tunnel construction. Common degradation mechanisms associated with HDPE （high density polyethylene） sheets are described. The stringent requirements for the Gotthard Alpine Railway Tunnel through the Swiss Alps, e.g., high ambient temperatures of up to 45 ℃ and an expected service life of up to 100 years require outstanding aging resistance of polymeric drainage materials. The paper describes the methods deployed to investigate the long-term performance of HDPE drainboards, focusing on aging mechanisms. Details associated with the test procedures developed to reflect the specific properties of drainboards, as well as the results obtained, are presented. A summary table shows recommended product specifications needed to confine the aging properties of drainboards and to design a system performing adequately during the entire lifetime of the structure.     

Sewer Discharge Estimation by Stereoscopic Imaging and Synchronized Frame Processing

A system for fully automatic contact‐less image‐based measurement of volumetric flow rate in urban drainage structures is presented. The hardware includes two original equipment manufacturer cameras and a single‐board computer on which our custom image processing software is running. The value of water discharge depends on the surface velocity, water level and channel's geometry. The level of the flow is estimated as the difference between distances from the camera to the water surface and from the camera to the channel's bottom. Camera‐to‐water distance is recovered automatically using large‐scale stereo‐matching, whereas the distance to the channel's bottom is measured upon installation. Surface velocity is calculated using cross‐correlation template matching: individual natural particles in the flow are detected and tracked throughout the sequence of images recorded over a fixed time interval. The relative discharge computation error is lower than 1.34% of the theoretical maximal discharge for a given location, which makes our system competitive to commercial components such as ultrasonic flow meters, while using cheaper technologies.     

Design of a Low-Cost Thermal Dispersion Mass Air Flow (MAF) Sensor

There is a need for a low-cost sensor to be used in many practical applications, such as the control of the air–fuel ratio in combustion burners, which measures the mass flow rate of fluid. This paper focuses on the design, calibration, and testing of a mass flow sensor operating on the principle of thermal dispersion. The developed sensor implements a digital proportional-integral controller which regulates the body temperature of a heated element, recognized as a thermistor, located in the stream of the fluid flow to a constant difference with respect to the ambient air temperature. The power dissipated by this heated element was referenced to known mass flow rates of air to determine the relationship between the dissipated power and ambient temperature to the measured mass flow rate. The inclusion of air flow conditioners, which filtered unwanted debris and delivered a more laminar air flow, was imperative to the success of the design. The designed sensor was proven to measure the incoming mass air flow through a duct, in the presence of moderate disturbances in the intake air pipe and for a wide range of ambient air temperatures, with a maximum full-scale error of 5.5% and a range up to 80 kg/h.