Structural and electrical anisotropy of (001)-, (116)-, and (103)-oriented epitaxial SrBi2Ta2O9 thin films on SrTiO3 substrates grown by pulsed laser deposition

Epitaxial SrBi2Ta2O9 (SBT) thin films with well-defined (001), (116), and (103) orientations have been grown by pulsed laser deposition on (001)-, (011)-, and (111)-oriented Nb-doped SrTiO3 substrates. X-ray diffraction pole figure and phi -scan measurements revealed that the three-dimensional epitaxial orientation relation SBT(001)parallel to SrTiO3(001), and SBT[1(1) over bar 0]parallel to SrTiO3[100] is valid for all cases of SET thin films on SrTiO3 substrates, irrespective of their orientations. Atomic force microscopy images of the c-axis-oriented SET revealed polyhedron-shaped grains showing spiral growth around screw dislocations. The terrace steps of the c-axis-oriented SET films were integral multiples of a quarter of the lattice parameter c of SBT (similar to 0.6 nm). The grains of (103)-oriented SET films were arranged in a triple-domain configuration consistent with the symmetry of the SrTiO3(111) substrate. The measured remanent polarization (2P(r)) and coercive field (2E(c)) of (116)-oriented SBT films were 9.6 muC/cm(2) and 168 kV/cm, respectively, for a maximum applied electric field of 320 kV/cm. Higher remanent polarization (2P(r)=10.4 muC/cm(2)) and lower coercive field (2E(c)=104 kV/cm) than those of SBT(116) films were observed in (103)-oriented SET thin films, and (001)-oriented SET revealed no ferroelectricity along the [001] axis. The dielectric constants of (001)-, (116)-, and (103)-oriented SBT were 133, 155, and 189, respectively. (C) 2000 American Institute of Physics.

Microbial Ecology and Geo-electrical Responses across a Groundwater Plume

We have used geophysics, microbiology, and geochemistry to link large-scale (30+ m) geophysical self-potential (SP) responses at a groundwater contaminant plume with its chemistry and microbial ecology of groundwater and soil from in and around it. We have found that microbially mediated transformation of ammonia to nitrite, nitrate, and nitrogen gas was likely to have promoted a well-defined electrochemical gradient at the edge of the plume, which dominated the SP response. Phylogenetic analysis demonstrated that the plume fringe or anode of the geobattery was dominated by electrogens and biodegradative microorganisms including Proteobacteria alongside Geobacteraceae, Desulfobulbaceae, and Nitrosomonadaceae. The uncultivated candidate phylum OD1 dominated uncontaminated areas of the site. We defined the redox boundary at the plume edge using the calculated and observed electric SP geophysical measurements. Conductive soils and waste acted as an electronic conductor, which was dominated by abiotic iron cycling processes that sequester electrons generated at the plume fringe. We have suggested that such geoelectric phenomena can act as indicators of natural attenuation processes that control groundwater plumes. Further work is required to monitor electron transfer across the geoelectric dipole to fully define this phenomenon as a geobattery. This approach can be used as a novel way of monitoring microbial activity around the degradation of contaminated groundwater plumes or to monitor in situ bioelectric systems designed to manage groundwater plumes.

Residential electrical vehicle charging strategies: the good, the bad and the ugly

In recent years, a wide variety of centralised and decentralised algorithms have been proposed for residential charging of electric vehicles (EVs). In this paper, we present a mathematical framework which casts the EV charging scenarios addressed by these algorithms as optimisation problems having either temporal or instantaneous optimisation objectives with respect to the different actors in the power system. Using this framework and a realistic distribution network simulation testbed, we provide a comparative evaluation of a range of different residential EV charging strategies, highlighting in each case positive and negative characteristics.

Structure, mechanical, and electrical properties of high-density polyethylene/multi-walled carbon nanotube composites processed by compression molding and blown film extrusion

The structure and properties of melt mixed high-density polyethylene/multi-walled carbon nanotube (HDPE/MWCNT) composites processed by compression molding and blown film extrusion were investigated to assess the influence of processing route on properties. The addition of MWCNTs leads to a more elastic response during deformations that result in a more uniform thick-ness distribution in the blown films. Blown film composites exhibit better mechanical properties due to the enhanced orientation and disentanglement of MWCNTs. At a blow up ratio (BUR) of 3 the breaking strength and elongation in the machine direction of the film with 4 wt % MWCNTs are 239% and 1054% higher than those of compression molded (CM) samples. Resistivity of the composite films increases significantly with increasing BURs due to the destruction of conductive pathways. These pathways can be recovered partially using an appropriate annealing process. At 8 wt % MWCNTs, there is a sufficient density of nanotubes to maintain a robust network even at high BURs.

Secure data networks for electrical distribution applications

Smart Grids are characterized by the application of information communication technology (ICT) to solve electrical energy challenges. Electric power networks span large geographical areas, thus a necessary component of many Smart Grid applications is a wide area network (WAN). For the Smart Grid to be successful, utilities must be confident that the communications infrastructure is secure. This paper describes how a WAN can be deployed using WiMAX radio technology to provide high bandwidth communications to areas not commonly served by utility communications, such as generators embedded in the distribution network. A planning exercise is described, using Northern Ireland as a case study. The suitability of the technology for real-time applications is assessed using experimentally obtained latency data.

A Reliability Assessment Approach For Integrated Transportation and Electrical Power Systems Incorporating Electric Vehicles

With the increasing utilization of electric vehicles (EVs), transportation systems and electrical power systems are becoming increasingly coupled. However, the interaction between these two kinds of systems are not well captured, especially from the perspective of transportation systems. This paper studies the reliability of integrated transportation and electrical power system (ITES). A bidirectional EV charging control strategy is first demonstrated to model the interaction between the two systems. Thereafter, a simplified transportation system model is developed, whose high efficiency makes the reliability assessment of the ITES realizable with an acceptable accuracy. Novel transportation system reliability indices are then defined from the view point of EV’s driver. Based on the charging control model and the transportation simulation method, a daily periodic quasi sequential reliability assessment method is proposed for the ITES system. Case studies based on RBTS system demonstrate that bidirectional charging controls of EVs will benefit the reliability of power systems, while decrease the reliability of EVs travelling. Also, the optimal control strategy can be obtained based on the proposed method. Finally, case studies are performed based on a large scale test system to verify the practicability of the proposed method.

Local conductance: A means to extract polarization and depolarizing fields near domain walls in ferroelectrics

Conducting atomic force microscopy images of bulk semiconducting BaTiO3 surfaces show clear stripe domain contrast. High local conductance correlates with strong out-of-plane polarization (mapped independently using piezoresponse force microscopy), and current- voltage characteristics are consistent with dipole-induced alterations in Schottky barriers at the metallic tip-ferroelectric interface. Indeed, analyzing current-voltage data in terms of established Schottky barrier models allows relative variations in the surface polarization, and hence the local domain structure, to be determined. Fitting also reveals the signature of surface-related depolarizing fields concentrated near domain walls. Domain information obtained from mapping local conductance appears to be more surface-sensitive than that from piezoresponse force microscopy. In the right materials systems, local current mapping could therefore represent a useful complementary technique for evaluating polarization and local electric fields with nanoscale resolution.

Efficacy of Wind Power in Mitigation of CO2 Emission from the Irish Electrical Grid

The results in this paper are based on a data set containing system demand, wind generation and CO2 emission between Jan 2010 and Sep 2013. The data was recorded at 15 minute intervals and reflects the macroscopic operation of the Republic of Ireland's electrical grid. The data was analyzed by investigating how daily wind generation effected daily CO2 emission across multiple days with equivalent daily demand. A figure for wind turbine efficiency was determined by dividing the CO2 mitigation potential of wind power by the CO2 intensity of the grid; both in units of Tonnes of CO2 per MWh. The yearly wind power efficiency appears to have increased by 5.6% per year, now standing around 90%. Over the four years significant regularity was observed in the profiles of wind turbine efficiency against daily demand. It appears that the efficiency profile has moved in recent years so that maximum efficiency coincides with most frequent demand.

Geotechnical monitoring using a combination of LIDAR, real-time dGPS, and electrical tomography to assess geotechnical risk of a coastal landslide.

The Antrim Coast Road stretching from the seaport of Larne in the East of Northern Ireland has a well-deserved reputation for being one of the most spectacular roads in Europe (Day, 2006). However the problematic geology; Jurassic Lias Clay and Triassic Mudstone overlain by Cretaceous Limestone and Tertiary Basalt, and environmental variables result in frequent instances of slope instability manifested in both shallow debris flows and occasional massive rotational movements, creating a geotechnical risk to this highway. This paper describes how a variety of techniques are being used to both assess instability and monitor movement of these active slopes near one site at Straidkilly Point, Glenarm. An in-depth understanding of the geology was obtained via boreholes, resistivity surveys and laboratory testing. Environmental variables recorded by an on-site weather station were correlated with measured pore water pressure and soil moisture infiltration data. Terrestrial LiDAR (TLS), with surveys carried out on a bi-monthly basis allowed for the generation of Digital Elevation Models (DEMs) of difference, highlighting areas of recent movement, accumulation and depletion. Morphology parameters were generated from the DEMs and include slope, curvature and multiple measures of roughness. Changes in the structure of the slope coupled with morphological parameters were characterised and linked to progressive failures from the temporal monitoring. In addition to TLS monitoring, Aerial LiDAR datasets were used for the spatio-morphological characterisation of the slope on a macro scale. A Differential Global Positioning System (dGPS) was also deployed on site to provide a real-time warning system for gross movements, which were also correlated with environmental conditions. Frequent electrical resistivity tomography (ERT) surveys were also implemented to provide a better understanding of long-term changes in soil moisture and help to define the complex geology. The paper describes how the data obtained via a diverse range of methods has been combined to facilitate a more informed management regime of geotechnical risk by the Northern Ireland Roads Service.

Salinity-induced effects on transpiration rate, stomatal conductance and leaf area of three olive (Olea europaea L.) varieties

Transpiration of two year-old olive trees of three different varieties, Arbequina, Cobrançosa and Galega (18 trees per variety), irrigated with three levels of salt (0, 80 or 200 mM NaCl) for about 90 days, was measured by a gravimetric method. To determine leaf area, each tree was photographed from the side against a white background and the total area of each projected image was determined with ImageJ software. To calibrate these area determinations, one tree of each variety was subsequently stripped of all its leaves and its total leaf area was accurately measured. A correlation was then obtained between the area on the photograph of this particular tree and the total area of the detached leaves of the same tree. Using the leaf area determined by this procedure, transpiration rates of the trees could be calculated. Knowing leaf and air temperatures and RH, it was possible to determine the difference in molar fraction of water between the leaf and the air. Using this and the values of the transpiration rate, stomatal conductance could be calculated (gs calc) and compared with the conductance measured on the same trees with a porometer (gs). Actual leaf area of a plant was 1,40 (Arbequina), 1,42 (Cobrançosa) or 1,24 (Galega) times the area measured with ImageJ on the photograph of the same plant. Leaf area of the trees, on average of all salt irrigations, was significantly higher on Arbequina (0,187 m2) then on the other two varieties (0,138 m2 or 0,148 m2, for Cobrançosa or Galega, respectively), but did not differ significantly in percentage of controls (0 salt). On average of all three varieties, leaf area was also higher on plants irrigated without salt (0,181 m2) than on plants exposed to 80 or 200 mM NaCl (0,152 m2 or 0,140 m2, respectively), which did not differ between them. The same significant difference was observed when leaf area was expressed as percentage of controls. Transpiration rate was significantly higher on Cobrançosa (1,17 mmol m-2 s-1), on average of all treatments, but there were no significant differences between Arbequina (1,08 mmol m-2 s-1) and Galega (0,82 mmol m-2 s-1). In percentage of controls, there were no significant differences between varieties. Salt reduced significantly the transpiration rate in all varieties, both the actual and percentual values, to about 50% or 30% of controls when exposed to 80 mM or 200 mM NaCl, respectively. Stomatal conductance (gs), assessed by porometry, was significantly higher in control plants, mainly in Cobrançosa (102 mmol m-2 s-1), then in Arbequina (77 mmol m-2 s-1) and the lower values were found in Galega (51 mmol m-2 s-1). Salt reduced gs, on average of the three varieties to 30% or 10% of controls on exposure to 80 mM or 200 mM NaCl, respectively. Calculated (gs calc) and measured (gs) values of stomatal conductance showed a close relation between them (0,967, R2 = 0,837) which indicates this non-destructive method to determine whole-plant leaf area to be reasonably accurate.

Electrical characterization of organic based transistors: stability issues

An investigation into the stability of metal insulator semiconductor (MIS) transistors based on alpha-sexithiophene is reported. In particular the kinetics of the threshold voltage shift upon application of a gate bias has been determined. The kinetics follow a stretched-hyperbola type behavior, in agreement with the formalism developed to explain metastability in amorphous-silicon thin film transistors. Using this model, quantification of device stability is possible. Temperature-dependent measurements show that there are two processes involved in the threshold voltage shift, one occurring at T approximate to 220 K and the other at T approximate to 300 K. The latter process is found to be sample dependent. This suggests a relation between device stability and alpha-sexithiophene deposition parameters. Copyright (c) 2005 John Wiley A Sons, Ltd.

Determination of the Maximum Rate of Eccrine Sweat Glands’ Ion Reabsorption Using the Galvanic Skin Conductance to Local Sweat Rate Relationship

Purpose The purpose of the present study was to develop and describe a simple method to evaluate the rate of ion reabsorption of eccrine sweat glands in human using the measurement of galvanic skin conductance (GSC) and local sweating rate (SR). This purpose was investigated by comparing the SR threshold for increasing GSC with following two criteria of sweat ion reabsorption in earlier studies such as 1) the SR threshold for increasing sweat ion was at approximately 0.2 to 0.5 mg/cm2/min and 2) exercise-heat acclimation improved the sweat ion reabsorption ability and would increase the criteria 1. Methods Seven healthy non-heat-acclimated male subjects received passive heat treatment both before and after 7 days of cycling in hot conditions (50% maximum oxygen uptake, 60 min/day, ambient temperature 32°C, and 50% relative humidity). Results Subjects became partially heat-acclimated, as evidenced by the decreased end-exercise heart rate (p<0.01), rate of perceived exhaustion (p<0.01), and oesophageal temperature (p=0.07), without alterations in whole-body sweat loss, from the first to the last day of training. As hypothesised, we confirmed that the SR threshold for increasing GSC was near the predicted SR during passive heating before exercise heat acclimation, and increased significantly after training (0.19 ± 0.09 to 0.32 ± 0.10 mg/cm2/min, p<0.05). Conclusions The reproducibility of sweat ion reabsorption by the eccrine glands in the present study suggests that the relationship between GSC and SR can serve as a new index for assessing the maximum rate of sweat ion reabsorption of eccrine sweat glands in humans.

TINSEL – a web-based intelligent tutoring system on electrical installation design

This paper presents a project consisting on the development of an Intelligent Tutoring System, for training and support concerning the development of electrical installation projects to be used by electrical engineers, technicians and students. One of the major goals of this project is to devise a teaching model based on Intelligent Tutoring techniques, considering not only academic knowledge but also other types of more empirical knowledge, able to achieve successfully the training of electrical installation design.