Current-induced forces: a simple derivation

We revisit the problem of forces on atoms under current in nanoscale conductors. We derive and discuss the five principal kinds of force under steady-state conditions from a simple standpoint that—with the help of background literature—should be accessible to physics undergraduates. The discussion aims at combining methodology with an emphasis on the underlying physics through examples. We discuss and compare two forces present only under current—the non-conservative electron wind force and a Lorentz-like velocity-dependent force. It is shown that in metallic nanowires both display significant features at the wire surface, making it a candidate for the nucleation of current-driven structural transformations and failure. Finally we discuss the problem of force noise and the limitations of Ehrenfest dynamics

State detection of bond wires in IGBT modules using eddy current pulsed thermography

Insulated gate bipolar transistor (IGBT) modules are important safety critical components in electrical power systems. Bond wire lift-off, a plastic deformation between wire bond and adjacent layers of a device caused by repeated power/thermal cycles, is the most common failure mechanism in IGBT modules. For the early detection and characterization of such failures, it is important to constantly detect or monitor the health state of IGBT modules, and the state of bond wires in particular. This paper introduces eddy current pulsed thermography (ECPT), a nondestructive evaluation technique, for the state detection and characterization of bond wire lift-off in IGBT modules. After the introduction of the experimental ECPT system, numerical simulation work is reported. The presented simulations are based on the 3-D electromagnetic-thermal coupling finite-element method and analyze transient temperature distribution within the bond wires. This paper illustrates the thermal patterns of bond wires using inductive heating with different wire statuses (lifted-off or well bonded) under two excitation conditions: nonuniform and uniform magnetic field excitations. Experimental results show that uniform excitation of healthy bonding wires, using a Helmholtz coil, provides the same eddy currents on each, while different eddy currents are seen on faulty wires. Both experimental and numerical results show that ECPT can be used for the detection and characterization of bond wires in power semiconductors through the analysis of the transient heating patterns of the wires. The main impact of this paper is that it is the first time electromagnetic induction thermography, so-called ECPT, has been employed on power/electronic devices. Because of its capability of contactless inspection of multiple wires in a single pass, and as such it opens a wide field of investigation in power/electronic devices for failure detection, performance characterization, and health monitoring. 

Evaluating environmental enrichment options for commercial broiler chickens

Implications Provision of environmental enrichment in line with that required by welfare-based quality assurance schemesdoes not always appear to lead to clear improvements in broiler chicken welfare. This research perhaps serves to highlightthe deficit in information regarding the ‘real world’ implications of enrichment with perches, string and straw bales.

Introduction Earlier work showed that provision of natural light and straw bales improved leg health in commercial broilerchickens (Bailie et al., 2013). This research aimed to determine if additional welfare benefits were shown in windowedhouses by increasing straw bale provision (Study 1), or by providing perches and string in addition to straw bales (Study 2).

Material and methods Commercial windowed houses in Northern Ireland containing ~23,000 broiler chickens (placed inhouses as hatched) were used in this research which took place in 2011. In Study 1 two houses on a single farm wereassigned to one of two treatments: (1) 30 straw bales per house (1 bale/44m2), or (2) 45 straw bales per house (1bale/29m2). Bales of wheat straw, each measuring 80cm x 40cm x 40cm were provided from day 10 of the rearing cycle,as in Bailie et al. (2013). Treatments were replicated over 6 production cycles (using 276,000 Ross 308 and Cobb birds),and were swapped between houses in each replicate. In Study 2, four houses on a single farm were assigned to 1 of 4treatments in a 2 x 2 factorial design. Treatments involved 2 levels of access to perches (present (24/house), or absent), and2 levels of access to string (present (24/house), or absent), and both types of enrichment were provided from the start of thecycle. Each perch consisted of a horizontal, wooden beam (300 cm x 5 cm x 5cm) with a rounded upper edge resting on 2supports (15 cm high). In the string treatment, 6 pieces of white nylon string (60 cm x 10 mm) were tied at their mid-pointto the wire above each of 4 feeder lines. Thirty straw bales were also provided per house from day 10. This study wasreplicated over 4 production cycles using 368,000 Ross 308 birds. In both studies behaviour was observed between 0900and 1800 hours in weeks 3-5 of the cycle. In Study 1, 8 focal birds were selected in each house each week, and generalactivity, exploratory and social behaviours recorded directly for 10 minutes. In Study 2, 10 minute video recordings weremade of 6 different areas (that did not contain enrichment) of each house each week. The percentage of birds engaged inlocomotion or standing was determined through scan sampling these recordings at 120 second intervals. Four perches andfour pieces of string were filmed for 25 mins in each house that contained these enrichments on one day per week. The totalnumber of times the perch or string was used was recorded, along with the duration of each bout. In both studies, gaitscores (0 (perfect) to 5 (unable to walk)) and latency to lie (measured in seconds from when a bird had been encouraged tostand) were recorded in 25 birds in each house each week. Farm and abattoir records were also used in both studies todetermine the number of birds culled for leg and other problems, mortality levels, slaughter weights, and levels of pododermatitis and hock burn. Data were analysed using SPSS (version 20.0) and treatment and age effects on behaviouralparameters were determined in normally distributed data using ANOVA (‘Straw bale density*week’, or‘string*perches*week’ as appropriate), and in non-normally distributed data using Kuskall-Wallace tests (P<0.05 forsignificance) . Treatment (but not age) effects on performance and health data were determined using the same testsdepending on normality of data.

Results Average slaughter weight, and levels of mortality, culling, hock burn and pododermatitis were not affected bytreatment in either study (P<0.05). In Study 1 straw bale (SB) density had no significant effect on the frequency orduration of behaviours including standing, walking, ground pecking, dust bathing, pecking at bales or aggression, or onaverage gait score (P>0.05). However, the average latency to lie was greater when fewer SB were provided (30SB 23.38s,45SB 18.62s, P<0.01). In Study 2 there was an interaction between perches (Pe) and age in lying behaviour, with higherpercentages of birds observed lying in the Pe treatment during weeks 4 and 5 (week 3 +Pe 77.0 -Pe 80.9, week 4 +Pe 79.5 -Pe 75.2, week 5 +Pe 78.4 -Pe 76.2, P<0.02). There was also a significant interaction between string (S) and age inlocomotory behaviour, with higher percentages of birds observed in locomotion in the string treatment during week 3 butnot weeks 4 and 5 (week 3 +S 4.9 -S 3.9, week 4 +S 3.3 -S 3.7, week 5 +S 2.6 -S 2.8, P<0.04). There was also aninteraction between S and age in average gait scores, with lower gait scores in the string treatment in weeks 3 and 5 (week3: +S 0.7, -S 0.9, week 4: +S 1.5, -S 1.4, week 5: +S 1.9, -S 2.0, P<0.05). On average per 25 min observation there were15.1 (±13.6) bouts of perching and 19.2 (±14.08) bouts of string pecking, lasting 117.4 (±92.7) and 4.2 (±2.0) s for perchesand string, respectively.

Conclusion Increasing straw bale levels from 1 bale/44m2 to 1 bale/29m2 floor space does not appear to lead to significantimprovements in the welfare of broilers in windowed houses. The frequent use of perches and string suggests that thesestimuli have the potential to improve welfare. Provision of string also appeared to positively influence walking ability.However, this effect was numerically small, was only shown in certain weeks and was not reflected in the latency to lie.Further research on optimum design and level of provision of enrichment items for broiler chickens is warranted. Thisshould include measures of overall levels of activity (both in the vicinity of, and away from, enrichment items).

Structure and Catalytic Activity of Gold in Low-Temperature CO Oxidation

Structures and catalytic activities of Au thin films supported at anatase TiO(2)(101)) and a Au substrate are studied by using density functional theory calculations. The results show that O(2) can hardly adsorb at flat and stepped Au thin films, even supported by fully reduced TiO(2)(101) that can highly disperse Au atoms and offer strong electronic promotion. Interestingly, in both oxide-supported and pure Au. systems, wire-structured Au can adsorb both CO and O(2) rather strongly, and kinetic analysis suggests its high catalytic activity for low-temperature CO oxidation. The d-band center of Au at the catalytic site is determined to account for the unusual activity of the wire-structured film. A generalized structural model based on the wire-structured film is proposed for active Au, and possible support effects are discussed: Selected oxide surfaces can disperse Au atoms and stabilize the formation of a filmlike structure; they may also serve as a template for the preferential arrangement of Au atoms in a wire structure under low Au coverage.

Economic evaluation and its place in dentistry

Objective: This review intends to examine current research surrounding economic assessment in the delivery of dental care. Economic evaluation is an acknowledged method of analysing dental care systems by means of efficiency, effectiveness, efficacy and availability. Though this is a widely used method in medicine, it is underappreciated in dentistry. As the delivery of health care changes there has been recent demand by the public, the profession, and those funding dental treatment to investigate current practices regarding programs themselves and resource allocation.
Methods: A meta-analysis was conducted regarding health economics. The initial search was carried out using Pubmed, Google Scholar, Science Direct, and The Cochrane Library with search terms “health AND economics AND dentistry”. A secondary search was conducted with the terms “heath care AND dentistry AND”. The third part of the entry was changed to address the aims and included the following terms: “cost benefit analysis”, “efficiency criteria”, “supply & demand”, “cost-effectiveness”, “cost minimisation”, “cost utility”, “resource allocation”, “QALY”, and “delivery and economics”. Limits were applied to all searches to only include papers published in English within the last eight years.
Results: Preliminary results demonstrated a limited number of economic evaluations conducted in dentistry. Those that were carried out were mainly confined to the United Kingdom. Furthermore analysis was mainly restricted to restorative dentistry, followed by orthodontics, and maxillofacial surgery, thereby demonstrating a need for investigation in all fields of dentistry.
Conclusion: Health economics has been overlooked in the past regarding delivery of dental care and resource allocation. Economic appraisal is a crucial part of generating an effective and efficient dental care system. It is becoming increasingly evident that there is a need for economic evaluation in all dental fields.

Material Identification of Loose Particles in Sealed Electronic Devices Using PCA and SVM

The existence of loose particles left inside the sealed electronic devices is one of the main factors affecting the reliability of the whole system. It is important to identify the particle material for analyzing their source. The conventional material identification algorithms mainly rely on time, frequency and wavelet domain features. However, these features are usually overlapped and redundant, resulting in unsatisfactory material identification accuracy. The main objective of this paper is to improve the accuracy of material identification. First, the principal component analysis (PCA) is employed to reselect the nine features extracted from time and frequency domains, leading to six less correlated principal components. And then the reselected principal components are used for material identification using a support vector machine (SVM). Finally, the experimental results show that this new method can effectively distinguish the type of materials including wire, aluminum and tin particles.

Strengthening timber beams with near surface mounted carbon fiber reinforced polymer rods

Many timber structures may require strengthening due to either decay and aging or an increase of load. This paper presents an experimental study in which eleven timber beams were tested, including three unstrengthened reference beams and eight beams strengthened with NSM CFRP bars. The test parameters include the position of NSM (tensile face or the bottom of the sides), the number of CFRP bars (1 or 2), and additional anchorage of NSM CFRP bars (steel wire U anchors or CFRP U strips). The test results show that the ultimate flexural strength of the timber beams were increased by 14%∼85% with an average of 47% due to NSM CFRP bar strengthening. Their deflection corresponding to the peak load was increased by 33% in average.

Experimental analysis of air flow profiles in a double skin facade in a maritime climate

Glazed Double Skin Facades (DSF) offer the potential to improve the performance of all-glass building skins, common to commercial office buildings in which full facade glazing has almost become the standard. Single skin glazing results in increased heating and cooling costs over opaque walls, due to lower thermal resistance of glass, and the increased impact of solar gain through it. However, the performance benefit of DSF technology continues to be questioned and its operation poorly understood, particularly the nature of airflow through the cavity. This paper deals specifically with the experimental analysis of the air flow characteristics in an automated double skin façade. The benefit of the DSF as a thermal buffer, and to limit overheating is evaluated through analysis of an extensive set of parameters including air and surface temperatures at each level in the DSF, airflow readings in the cavity and at the inlet and outlet, solar and wind data, and analytically derived pressure differentials. The temperature and air-flow are monitored in the cavity of a DSF using wireless sensors and hot wire anemometers respectively. Automated louvre operation and building set-points are monitored via the BMS. Thermal stratification and air flow variation during changing weather conditions are shown to effect the performance of the DSF considerably and hence the energy performance of the building. The relative pressure effects due to buoyancy and wind are analysed and quantified. This research aims to developed and validate models of DSFs in the maritime climate, using multi-season data from experimental monitoring. This extensive experimental study provides data for training and validation of models.

Assessment Of various sensors for structural health monitoring for bridge weigh-in-motion (B-WIM).

In recent years, Structural Health Monitoring (SHM) systems have been developed to monitor bridge deterioration, assess real load levels and hence extend bridge life and safety. A road bridge is only safe if the stresses caused by the passing vehicles are less than the capacity of the bridge to resist them. Conventional SHM systems can be used to improve knowledge of the bridges capacity to resist stresses but generally give no information on the causes of any increase in stresses (based on measuring strain). The concept of in Bridge Weigh-in-Motion (B-WIM) is to establish axle loads, without interruption to traffic flow, by using strain sensors at a bridge soffit and subsequently converting the data to real time axle loads or stresses. Recent studies have shown it would be most beneficial to develop a portable system which can be easily attached to existing and new bridge structures for a specified monitoring period. The sensors could then be left in place while the data acquisition can be moved for various other sites. Therefore it is necessary to find accurate sensors capable of capturing peak strains under dynamic load and suitable methods for attaching these strain sensors to existing and new bridge structures. Additionally, it is important to ensure accurate strain transfer between concrete and steel, the adhesives layer and the strain sensor. This paper describes research investigating the suitably of using various sensors for the monitoring of concrete structures under dynamic vehicle load. Electrical resistance strain (ERS) gauges, vibrating wire (VW) gauges and fibre optic sensors (FOS) are commonly used for SHM. A comparative study will be carried out to select a suitable sensor for a bridge Weigh in Motion System. This study will look at fixing methods, durability, scanning rate and accuracy range. Finite element modeling is used to predict the strains which are then validated in laboratory trials.

Corrosion Fatigue Behaviour of Laser-welded Shape Memory NiTi Wires in a Simulated Body Fluid

Corrosion fatigue is a fracture process as a consequence of synergistic interactions between the material structure, corrosive environment and cyclic loads/strains. It is difficult to be detected and can cause unexpected failure of engineering components in use. This study reveals a comparison of corrosion fatigue behaviour of laser-welded and bare NiTi wires using bending rotation fatigue (BRF) test coupled with a specifically-designed corrosion cell. The testing medium was Hanks’ solution (simulated body fluid) at 37.5 oC. Electrochemical impedance spectroscopic (EIS) measurement was carried out to monitor the change of corrosion resistance of sample during the BRF test at different periods of time. Experiments indicate that the laser-welded NiTi wire would be more susceptible to the corrosion fatigue attack than the bare NiTi wire. This study can serve as a benchmark for the product designers and engineers to understand the corrosion fatigue behaviour of the NiTi laser weld joint and determine the fatigue life safety factor for NiTi medical devices/implants involving laser welding in the fabrication process.

Investigations of ultrafast charge dynamics in laser-irradiated targets by a self probing technique employing laser driven protons

The divergent and broadband proton beams produced by the target normal sheath acceleration mechanism provide the unique opportunity to probe, in a point-projection imaging scheme, the dynamics of the transient electric and magnetic fields produced during laser-plasma interactions. Commonly such experimental setup entails two intense laser beams, where the interaction produced by one beam is probed with the protons produced by the second. We present here experimental studies of the ultra-fast charge dynamics along a wire connected to laser irradiated target carried out by employing a ‘self’ proton probing arrangement – i.e. by connecting the wire to the target generating the probe protons. The experimental data shows that an electromagnetic pulse carrying a significant amount of charge is launched along the wire, which travels as a unified pulse of 10s of ps duration with a velocity close to speed of light. The experimental capabilities and the analysis procedure of this specific type of proton probing technique are discussed.

Chromatic Aberration

Chromatic Aberration is a film installation which explores the early technologies of colour filmmaking drawn from the archives of George Eastman House, Rochester, New York. Featuring vibrant close-ups of eyes from fledgling archival experiments in colour film, Chromatic Aberration turns the cinematic lens in on itself: from the prosthetic recording eye of the camera, to an evocation of the abstract inner screen of one's eyelids. Early 1920s colour film footage - mainly tests shots featuring members of George Eastman's family as well as Hollywood stars of the time - is shot in such a way so as to reveal the inherent chromatic fringing, distortion and misalignment. Using specialist equipment at the BFI National Archive, London, the footage is reworked through the use of extreme close-up and magnification, honing in on the eyes. The installation evokes an imagined abstract colour world, a flickering eyelid trapped in a mechanical peephole. Exhibitions: Solo exhibition as film installation at Tyneside Cinema (Newcastle, Oct-Nov 2014); Solo exhibition at George Eastman Museum (Rochester, New York, Jan-April 2015), including a second work on display. Film festivals nominations for competitions: Winner of Best Vanguard Film Competition in Lima Independiente International Film Festival (Peru). Nominations: Filmadrid festival (Spain); Curtas Vila do Conde film festival (Portugal); Festival du Nouveau Cinema (Canada); Jihlava International Documentary Film Festival (Czech Republic ); International Film Festival Bratislava (Slovenia). Additional screenings at International Rotterdam Film Festival (Netherlands); European Media Art Festival (Germany); BFI London Film Festival (UK); Mini-retrospective screening at DIM CINEMA, The Cinematheque (Vancouver May 2015). Reviews and interviews in Artforum, The Wire Magazine, After Image, Studio International. Public lectures: with Prof. Sarah Street at Tyneside Cinema (Nov 2014); Royal Academy visiting public lecture (Nov 2014); ‘The Laughter of Things’ symposium, International Film Festival Rotterdam and Piet Zwart Institute (Jan 2015); George Eastman Museum and Rochester University (April 2015). Acquired by the George Eastman Museum for their collection.

The Trembling Line

The Trembling Line is a film and multi-channel sound installation exploring the visual and acoustic echoes between decipherable musical gestures and abstract patterning, orchestral swells and extreme high-speed slow-motion close-ups of strings and percussion. It features a score by Leo Grant and a newly devised multichannel audio system by the Institute of Sound and Vibration Research, University of Southampton. The multi-channel speaker array is devised as an intimate sound spatialisation system in which each element of sound can be pried apart and reconfigured, to create a dynamically disorienting sonic experience. It becomes the inside of a musical instrument, an acoustic envelope or cage of sorts, through which viewers are invited to experience the film and generate cross-sensory connections and counterpoints between the sound and the visuals. Funded by a Leverhulme Artist-in-Residence Award and John Hansard Gallery, with support from ISVR and the Music Department, University of Southampton. The project provided a rare opportunity to work creatively with new cutting edge developments in sound distribution devised by ISVR, devising a new speaker array, a multi- channel surround listening sphere which spatialises the auditory experience. The sphere is currently used by ISVR for outreach and teaching purposes, and has enables future collaborations between music staff and students at Southampton University and staff and ISVR. Exhibitions: Solo exhibition at John Hansard Gallery, Southampton (Dec 2015-Jan 2016), across 5 rooms, including a retrospective of five previous film-works and a new series of photographic stills. Public lectures: two within the gallery. Reviews and interviews: Art Monthly, Studio International, The Quietus, The Wire Magazine.

Visual cortex frontend: integrating lines, edges, keypoints and disparaty

We present a 3D representation that is based on the pro- cessing in the visual cortex by simple, complex and end-stopped cells. We improved multiscale methods for line/edge and keypoint detection, including a method for obtaining vertex structure (i.e. T, L, K etc). We also describe a new disparity model. The latter allows to attribute depth to detected lines, edges and keypoints, i.e., the integration results in a 3D \wire-frame" representation suitable for object recognition.

Using non-invasive techniques to examine black bear (Ursus americanus) abundance in the North Cascades Ecosystem, Washington State

Thesis (Master's)--University of Washington, 2013