A Time Domain Approach to Power Integrity for Printed Circuit Boards

Power integrity is becoming increasingly relevant due to increases in device functionality and switching speeds along with reduced operating voltage. Large current spikes at the device terminals result in electromagnetic disturbances which can establish resonant patterns affecting the operation of the whole system. These effects have been examined using a finite difference time domain approach to solve Maxwell's equations for the PCB power and ground plane configuration. The simulation domain is terminated with a uniaxial perfectly matched layer to prevent unwanted reflections. This approach calculates the field values as a function of position and time and allows the evolution of the field to be visualized. The propagation of a pulse over the ground plane was observed demonstrating the establishment of a complex interference pattern between source and reflected wave fronts and then between multiply reflected wave fronts. This interference which affects the whole ground plane area could adversely affect the operation of any device on the board. These resonant waves persist for a significant time after the initial pulse. Examining the FFT of the ground plane electric field response showed numerous resonant peaks at frequencies consistent with the expected values assuming the PCB can be modelled as a resonant cavity with two electric and four magnetic field boundaries.Comment: Presented at The University of Bolton Research and Innovation Conference, Bolton, UK. 16th September, 201

Novel ultra-energy-efficient reversible designs of sequential logic quantum-dot cellular automata flip-flop circuits

The version of record of this article, first published in [The Journal of Supercomputing], is available online at Publisher’s website: http://dx.doi.org/10.1007/s11227-023-05134-1Quantum-dot cellular automata (QCA) is a technological approach to implement digital circuits with exceptionally high integration density, high switching frequency, and low energy dissipation. QCA circuits are a potential solution to the energy dissipation issues created by shrinking microprocessors with ultra-high integration densities. Current QCA circuit designs are irreversible, yet reversible circuits are known to increase energy efficiency. Thus, the development of reversible QCA circuits will further reduce energy dissipation. This paper presents novel reversible and irreversible sequential QCA set/reset (SR), data (D), Jack Kilby (JK), and toggle (T) flip-flop designs based on the majority gate that utilizes the universal, standard, and efficient (USE) clocking scheme, which allows the implementation of feedback paths and easy routing for sequential QCA-based circuits. The simulation results confirm that the proposed reversible QCA USE sequential flip-flop circuits exhibit energy dissipation less than the Landauer energy limit. Irreversible QCA USE flip-flop designs, although having higher energy dissipation, sometimes have floorplan areas and delay times less than those of reversible designs; therefore, they are also explored. The trade-offs between the energy dissipation versus the area cost and delay time for the reversible and irreversible QCA circuits are examined comprehensively

Reversible Quantum-Dot Cellular Automata-Based Arithmetic Logic Unit

Quantum-dot cellular automata (QCA) are a promising nanoscale computing technology that exploits the quantum mechanical tunneling of electrons between quantum dots in a cell andelectrostatic interaction between dots in neighboring cells. QCA can achieve higher speed, lowerpower, and smaller areas than conventional, complementary metal-oxide semiconductor (CMOS) technology. Developing QCA circuits in a logically and physically reversible manner can provide exceptional reductions in energy dissipation. The main challenge is to maintain reversibility down to the physical level. A crucial component of a computer’s central processing unit (CPU) is the arithmetic logic unit (ALU), which executes multiple logical and arithmetic functions on the data processed by the CPU. Current QCA ALU designs are either irreversible or logically reversible; however, they lack physical reversibility, a crucial requirement to increase energy efficiency. This paper shows a new multilayer design for a QCA ALU that can carry out 16 different operations and is both logically and physically reversible. The design is based on reversible majority gates, which are the key building blocks. We use QCA Designer-E software to simulate and evaluate energy dissipation. The proposed logically and physically reversible QCA ALU offers an improvement of 88.8% in energy efficiency. Compared to the next most efficient 16-operation QCA ALU, this ALU uses 51% fewer QCA cells and 47% less area

An Ultra-Energy-Efficient Reversible Quantum-Dot Cellular Automata 8:1 Multiplexer Circuit

Energy efficiency considerations in terms of reduced power dissipation are a significant issue in the design of digital circuits for very large-scale integration (VLSI) systems. Quantum-dot cellular automata (QCA) is an emerging ultralow power dissipation approach, distinct from traditional, complementary metal-oxide semiconductor (CMOS) technology, for building digital computing circuits. Developing fully reversible QCA circuits has the potential to significantly reduce energy dissipation. Multiplexers are fundamental elements in the construction of useful digital circuits. In this paper, a novel, multilayer, fully reversible QCA 8:1 multiplexer circuit with ultralow energy dissipation is introduced. The power dissipation of the proposed multiplexer is simulated using the QCADesigner-E version 2.2 tool, describing the microscopic physical mechanisms underlying the QCA operation. The results show that the proposed reversible QCA 8:1 multiplexer consumes 89% less energy than the most energy-efficient 8:1 multiplexer circuit previously presented in the literature

Air ambulance outcome measures using Institutes of Medicine and Donabedian quality frameworks: protocol for a systematic scoping review

Background: Dedicated air ambulance services provide a vital link for critically ill and injured patients to higherlevels of care. The recent developments of pre-hospital and retrieval medicine create an opportunity for airambulance providers and policy-makers to utilize a dashboard of quality performance measures to assess serviceperformance. The objective of this scoping systematic review will be to identify and evaluate the range of airambulance outcome measures reported in the literature and help to construct a quality dashboard based on ahealthcare quality framework. Methods: We will search PubMed, MEDLINE, CINAHL, Scopus, and Cochrane Database of Systematic Reviews (fromJanuary 2001 onwards). Complementary searches will be conducted in selected relevant journals. We will includesystematic reviews and observational studies (cohort, cross-sectional, interrupted time series) in critically ill orinjured patients published in English and focusing on air ambulance delivery and quality measures. Two reviewerswill independently screen all citations, full-text articles, and abstract data. The study methodological quality (or bias)will be appraised using appropriate tools. Analysis of the characteristics associated with outcome measure will bemapped and described according to the proposed healthcare quality framework. Discussion: This review will contribute to the development of an air ambulance quality dashboard designed tocombine multiple quality frameworks. Our findings will provide a basis for helping decision-making in healthplanning and policy

Effect of cell-size on the energy absorption features of closed-cell aluminium foams

The effect of cell-size on the compressive response and energy absorption features of closed-cell aluminium (Al) foam were investigated by finite element method. Micromechanical models were constructed with a repeating unit-cell (RUC) which was sectioned from tetrakaidecahedra structure. Using this RUC, three Al foam models with different cell-sizes (large, medium and small) and all of same density, were built. These three different cell-size pieces of foam occupy the same volume and their domains contained 8, 27 and 64 RUCs respectively. However, the smaller cell-size foam has larger surface area to volume ratio compared to other two. Mechanical behaviour was modelled under uniaxial loading. All three aggregates (3D arrays of RUCs) of different cell-sizes showed an elastic region at the initial stage, then followed by a plateau, and finally, a densification region. The smaller cell size foam exhibited a higher peak-stress and a greater densification strain comparing other two cell-sizes investigated. It was demonstrated that energy absorption capabilities of smaller cell-size foams was higher compared to the larger cell-sizes examined

A survey of drivers' child restraint choice and knowledge in South Australia

This study investigated the frequency of child restraint choices in a sample consisting of 357 drivers in the Adelaide metropolitan area, who were transporting to school 586 children aged up to 10 years. The main survey result was that the rate of appropriate restraint was between 64% and 72% on such trips, (according to weight criteria in the Australian and New Zealand Standard on child restraints for motor vehicles). Only 1% are completely unrestrained. Most of those who were not restrained appropriately had prematurely progressed to an adult seatbelt. Appropriate child restraint use is lowest for children in the age range 5 - <7. Inappropriate restraint choice is strongly related to the child’s age, their seating location (children seated in the rear being more likely to be restrained appropriately), and possibly the child’s entry into primary school. Female drivers were more likely than male drivers to know what restraints were suitable for children in their carriage. However, it did not appear to be the case than good knowledge of child restraints is predictive of appropriate restraint use. Barriers to booster seat use included the child’s attitudes to using a booster seat. This effect may be lessened if the child’s age were able to used to guide restraint selection, as peer cues (for child and parent) would be more consistent. Drivers almost never mentioned cost as a barrier to child restraint use. Encouraging parents to become better informed may also help, but recommendations should be reviewed. Further developemnt of the Australian and New Zealand Standard for child restraints may enable age to be used as a criterion, thus simplifying advice to parents.S.A. Edwards, R.W.G. Anderson and T.P. Hutchinsonhttp://casr.adelaide.edu.au/publications/researchreports

Ultrasonic inspection and self-healing of Ge and 3C-SiC semiconductor membranes

Knowledge of the mechanical properties and stability of thin film structures is important for device operation. Potential failures related to crack initiation and growth must be identified early, to enable healing through e.g. annealing. Here, three square suspended membranes, formed from a thin layer of cubic silicon carbide (3C-SiC) or germanium (Ge) on a silicon substrate, were characterised by their response to ultrasonic excitation. The resonant frequencies and mode shapes were measured during thermal cycling over a temperature range of 20--100~$^\circ$C. The influence of temperature on the stress was explored by comparison with predictions from a model of thermal expansion of the combined membrane and substrate. For an ideal, non-cracked sample the stress and Q-factor behaved as predicted. In contrast, for a 3C-SiC and a Ge membrane that had undergone vibration and thermal cycling to simulate extended use, measurements of the stress and Q-factor showed the presence of damage, with the 3C-SiC membrane subsequently breaking. However, the damaged Ge sample showed an improvement to the resonant behaviour on subsequent heating. Scanning electron microscopy showed that this was due to a self-healing of sub-micrometer cracks, caused by expansion of the germanium layer to form bridges over the cracked regions, with the effect also observable in the ultrasonic inspection

Spreadsheet tools to estimate the thermal transmittance and thermal conductivities of gas spaces of an Insulated Glazing Unit

An Insulated Glazing unit (IGU) is constructed with two or more layers of glass panes sealed together by gas spaces in-between. IGUs are prevalent in windows, doors and rooflights, primarily due to their improved thermal resistance. Today, most IGUs are either two or three layered. Adding further layers of glass improves thermal insulation but with the penalty of increased cost and weight. Low emissivity (Low-e) film coatings, when deposited on the glass panes, reduce long-wavelength radiative heat losses. Furthermore, filling the gas spaces with the inert gases (e.g. Argon, Krypton, Xenon and SF6), further reduce conduction and natural convection across the gap. In summary, higher thermal insulation performance of an IGU can be achieved with gas fillings and Low-e coatings on glass. This report discusses spreadsheets that have been developed, capable of estimating the thermal transmittance values of IGU, as per BS EN 673. The spreadsheet tools also have the ability to estimate the thermal conductivity of the gas spaces between the panes of IGU

Verification of calculation code THERM in accordance with BS EN ISO 10077-2

Calculation codes are useful in predicting the heat transfer features in the fenestration industry. THERM is a finite element analysis based code, which can be used to compute thermal transmittance of windows, doors and shutters. It is important to verify results of THERM as per BS EN ISO 10077-2 to meet the compliance requirements. In this report, two-dimensional thermal conductance parameters were computed. Three versions of THERM, 5.2, 6.3 and 7.1, were used at two successive finite element mesh densities to assess their comparability. The results were all compliant with the aforementioned British Standard