Reduced Power Requirements Research Articles

Resonance frequency tuning of an RF cavity through sliding mode extremum seeking

Tuning of the natural resonance frequency of an RF cavity is crucial to achieve maximum power transfer from the cavity to the beam, to reduce power requirements, and to guarantee a predictable particle speed gain within each accelerator structure. So far, most operational cavities are frequency tuned through a phase comparison technique, which is sensitive to temperature variations if the facility or signal transportation cables are not temperature controlled. Temperature induced phase errors render this technique labor and time intensive. This paper presents an RF cavity tuning scheme, based on reflected power measurements and sliding mode extremum seeking control, to eliminate the phase measurement related difficulties. A stability analysis provides conditions on how to choose the controller parameters to guarantee stable system operation up to twice the cavity bandwidth, which is a controllable bandwidth improvement of a factor of two. The system has been implemented in two of TRIUMF’s (Canada’s particle accelerator centre) room temperature resonators and long term measurements show that the system effectively counteracts the RF heating effect as well as diurnal temperature variations.

Weird magnetic effect could improve computer memory

A surprising, theory-defying effect observed in magnetic devices could lead to efficient, low-power forms of computer memory, according to a new study (Phys. Rev. Lett. 2018, DOI: 10.1103/PhysRevLett.120.117703). For decades, applied physicists and semiconductor companies have developed computer magnetoresistive random access memory (MRAM) that uses the direction of a magnetic field to store data. A magnetic pulse or a jolt of electricity can change the properties of an island of magnetic material, flipping its field up or down to represent a 1 or a 0. The primary advantage of MRAM is its durability. “Once the data are recorded, you can pull the plug, and nothing will be lost,” says Johns Hopkins University physicist Chia-Ling Chien. Chien and other researchers want to improve MRAM by developing memory that can be written using small pulses of current. This would reduce power requirements and improve the lifetime of the memory arrays. Chien’s group

Computational Investigation of a Boundary-Layer-Ingestion Propulsion System

The present paper examines the potential propulsive and aerodynamic benefits of integrating a boundary-layer ingestion propulsion system into the Common Research Model geometry and the NASA tetrahedral unstructured software system. The numerical propulsion system simulation environment is used to generate engine conditions for computational fluid dynamics analyses. Improvements to the boundary-layer ingestion geometry are made using the constrained direct iterative surface curvature design method. The potential benefits of the boundary-layer ingestion system relating to cruise propulsive power are quantified using a power balance method, and a comparison to the baseline case is made. Iterations of the boundary-layer ingestion geometric design are shown, and improvements between subsequent boundary-layer ingestion designs are presented. Simulations are conducted for a cruise flight condition of Mach 0.85 at an altitude of 38,500 ft, with a Reynolds number of 40 million based on the mean aerodynamic chord and an angle of attack of 2 deg for all geometries. The results indicate an 8% reduction in engine power requirements at cruise for the boundary-layer ingestion configuration as compared to the baseline geometry. Small geometric alterations of the aft portion of the fuselage using constrained direct iterative surface curvature are shown to marginally increase the benefit from boundary-layer ingestion further, resulting in an 8.7% reduction in power requirements for cruise, as well as a drag reduction of approximately 12 counts over the baseline geometry.

A dimensionally reduced order piezoelectric energy harvester model

Presently reduced power requirement for small electronic components have been the main motivation for developing vibration based energy harvesting. The ultimate objective in this research field is to provide an easy, sustainable and efficient technology to power such small electronic devices from the unused vibrational energy available in the environment. A comprehensive, reliable mathematical technique is thus in high demand which can model a piezoelectric energy harvester, predict its coupled dynamics (structural and electromechanical) accurately. The present work focuses on developing a mathematical model for a slender, piezoelectric energy harvester based on Variational Asymptotic Method, a dimensional reduction methodology. Variational Asymptotic Method approximates the 3D electromechanical enthalpy as an asymptotic series to formulate an equivalent 1D electromechanical enthalpy functional to perform a systematic dimensional reduction. For validation purpose, we have picked up experimental results for a bimorph PZT harvester, available in the literature. We have studied the extension-bending structural coupling along with the parameter dependence of the voltage, power output from the harvester and validated with the experiments. The present study provides a unique, accurate modeling technique which is capable of capturing material anisotropy, structural coupling and can analyse arbitrary cross section, surface mounted as well as embedded piezo layered energy harvester.

Process and Cost Improved Agitator Solutions for Bioleach Reactors

As mineralogy has become more complex in the long history of hydrometallurgical processing, the process routes and equipment used had to adapt to the changing conditions [1]. Hydrometallurgical bioleaching processes have been developed for different key metals such as gold, nickel and copper amongst others, to overcome the limitations of leaching sulphidic ores. The core of such a hydrometallurgical bioleaching plant is a cascade of stirred atmospheric tank reactors. Large volumes of air that are blown into these tanks must be dispersed by the agitator in order to provide the necessary oxygen mass transfer rates. At the same time the agitator system must be able to properly suspend all solids, homogenize the vessel contents and remove the exothermic reaction heat by inner tube bundles to achieve optimal reaction conditions. Besides the ‘economies of scale’ and advances in process results, cost optimization of such systems is fundamental. Therefore EKATO has developed the Combijet+ technology which has significantly reduced power requirements, compared to conventional agitators. Another advantage of the Combijet+ technology is that the gas is injected directly into the highest shear zones, at the impeller blades. As a result the oxygen mass transfer is improved and also substantial cost savings for compressor power are possible. The technical paper will present EKATO’s Combijet technologies which support the next step towards a new generation of biohydrometallurgical processing plants. It will also give examples of large scale commercial applications where this technology is successfully in operation.

Optimal Mixed Tracking/Impedance Control With Application to Transfemoral Prostheses With Energy Regeneration.

We design an optimal passivity-based tracking/impedance control system for a robotic manipulator with energy regenerative electronics, where the manipulator has both actively and semi-actively controlled joints. The semi-active joints are driven by a regenerative actuator that includes an energy-storing element. External forces can have a large influence on energy regeneration characteristics. Impedance control is used to impose a desired relationship between external forces and deviation from reference trajectories. Multi-objective optimization (MOO) is used to obtain optimal impedance parameters and control gains to compromise between the two conflicting objectives of trajectory tracking and energy regeneration. We solve the MOO problem under two different scenarios: 1) constant impedance; and 2) time-varying impedance. The methods are applied to a transfemoral prosthesis simulation with a semi-active knee joint. Normalized hypervolume and relative coverage are used to compare Pareto fronts, and these two metrics show that time-varying impedance provides better performance than constant impedance. The solution with time-varying impedance with minimum tracking error (0.0008 rad) fails to regenerate energy (loses 9.53 J), while a solution with degradation in tracking (0.0452 rad) regenerates energy (gains 270.3 J). A tradeoff solution results in fair tracking (0.0178 rad) and fair energy regeneration (131.2 J). Our experimental results support the possibility of net energy regeneration at the semi-active knee joint with human-like tracking performance. The results indicate that advanced control and optimization of ultracapacitor-based systems can significantly reduce power requirements in transfemoral prostheses.

Effect of surface roughness on helicopter main rotor blade

This paper describes the effect of surface roughness when applied on helicopter main rotor blade. The aim is to prove that surface roughness can be used as a simple and inexpensive method to achieve better flight performance such as enhanced thrust and/or reduced power requirement. The research was done experimentally, using scaled model of Eurocopter AS350 Ecureuil. Smooth profile of the main rotor blade was modified by applying surface roughness on the upper and lower camber in transition and turbulent boundary layer region, starting from 25% of chord length and extending up to the trailing edge (TE). This study was conducted with the conditions of a vertical flight (particularly in hover condition) since this is a high powerconsuming flight regime for helicopter. The experiment resulted in lower power requirement but at the expense of reduced thrust at the middle collective pitch level. At upper range of the collective pitch level, surface roughness was seen to delay the stall angle as well as increase the lift in the stall region. Meanwhile, at lower pitch level, there was an increase in thrust-to-power ratio.

Natural vacuum distillation for seawater desalination – A review

The availability of fresh drinking water is one of the biggest concerns today. It is a bigger challenge for arid and semi-arid areas. In these regions, desalination is heavily relied upon for meeting freshwater demands. Many processes for desalination have been introduced in an effort to minimize the use of non-renewable energy sources and cut down on pollution. The purpose of this study was to present a review on one such process, namely the natural vacuum distillation (NVD). NVD uses the barometric height of water column (approximately 10.3 m) to generate a “natural vacuum” in the headspace above the water column. This low-pressure environment makes it possible to carry out the desalination process at low temperatures, which can be easily attained from renewable energy sources or from waste heat sources. Another benefit of such a process is that mechanical pumping is required only for start-up, hence reducing power requirements. This paper presents a review of the work carried out on the NVD process so far, the different systems that have been designed using this principle and the major factors that affect the production of water using this technology. Additionally, it points out the areas that need to be investigated further and underscores the future prospects of the NVD process.

Implementation of low‐power, non‐volatile latch utilising ferroelectric transistor

The implementation of a non-volatile latch circuit developed with a metal–ferroelectric–semiconductor field-effect transistor is presented. The circuit contains two inverter stages in order to create and rectify the desired waveform. The hysteresis properties of the ferroelectric transistor allow it to retain a polarisation state after an applied voltage at the gate is removed. This circuit has reduced power requirements because a constant power supply is not needed at all times; instead, a voltage is only needed at the gate of the ferroelectric transistor when storing a value, and the other components only need a power supply when reading the stored value from the circuit. The circuit is less complex than similar non-volatile latches because only a single ferroelectric transistor is used and fewer overall transistors may be used. It also has the advantage of being radiation-hardened for space applications.

Evaluation of tillage efficiency and power requirements for a deep-placement fertilizer applicator with reverse rotational rotary

The new implement “Deep-Placement Fertilizer Applicator” was developed. This implement has mainly two features. At first, it can conduct deep-placement fertilization which is one of environmentally friendly farming method. Second, this implement can save on labor costs because it simultaneously performs tillage, fertilization, seeding and suppression. In addition, an additional mature is not required because the effect of fertilizers is kept over a longer period by the deep-placement fertilization of the slow release fertilizer. In this study the modified model was developed with reverse rotational rotary to reduce power requirements. Experiments were conducted in Andosol soil to investigate the performance of the modified model quantitatively. The performance was compared with that of prototype model with conventional rotary under similar conditions. In this study, actual power requirements and soil pulverization performance were evaluated. The result clearly shows that the modified model was better than the prototype in terms of power requirements reduction and soil pulverization performance. The modified model consumed 16.7, 19.5 and 18.1% less power requirements than the prototype at 1.0, 1.5 and 2.0 km/h forward speed respectively. There were significant differences between the prototype and the modified model (p < 0.01) and clear difference was indicated in all conditions. Moreover, the modified model had a superior soil pulverization performance compared with the prototype. The average particle size of clod of the modified model was smaller than that of the prototype.

Physics-Based Trim Optimization of an Articulated Slowed-Rotor Compound Helicopter in High-Speed Flight

The present study focuses on the optimal trim states of a compound helicopter with an articulated main rotor, at a high-speed of 225 kt. In addition to conventional helicopter trim variables, variation in main rotor revolutions per minute, auxiliary thrust, stabilator pitch and aileron deflection are considered. Simulations are based on a compound derivative of a modified UH-60A helicopter with a 20,110 lb gross weight operating at standard sea level conditions. The results show that to achieve a reduced power requirement the stabilator should be used to bring the aircraft to a nearly nose-level pitch attitude, resulting in a significantly high wing lift share (approaching 70% in this study). Using the ailerons to introduce a roll right moment allows the rotor to operate at a higher lift-offset and generate its share of the lift with greater aerodynamic efficiency on the advancing side. In addition to the use of stabilator and ailerons, reduction in main rotor revolutions per minute is favored for low power, and the combination of these control surface and revolutions per minute settings reduces the rotor drag thereby requiring lower auxiliary thrust from the propulsor. The paper provides detailed discussions on the physical mechanisms producing changes to the trim state and the associated power benefits realized.

Chaotification as a Means of Broadband Energy Harvesting With Piezoelectric Materials

Component miniaturization and reduced power requirements in sensors have enabled growth in the field of low-power ambient vibration energy harvesting. This work aims to increase bandwidth and power output beyond current techniques by inducing chaotic nonlinear phenomena and applying a low-power controller based on the method of Ott, Grebogi, and Yorke (OGY) to stabilize a chosen periodic orbit. Previously, researchers used a nonlinear piezomagnetoelastic beam in search of a large amplitude broadband voltage response, but chaos was strictly avoided. These large amplitude responses can deteriorate over time into low energy chaotic oscillations. Including chaos as a desirable property allows small perturbations to alter the behavior of a system dramatically, improving the dynamic response for energy harvesting. The nonlinear piezomagnetoelastic beam element described by a Duffing oscillator is extended to embrace chaotic motion more actively. By driving motion along a chaotic attractor, even single frequency excitation results in a theoretically infinite number of unstable periodic orbits that can be stabilized using small control inputs. The chosen orbit will be accessible from a large range of excitation frequencies and can be dynamically changed in real-time, potentially expanding the bandwidth of operation.

An Efficient Implementation of Built in Self Diagnosis for Low Power Test Pattern Generator

A New architecture of Built-In Self-Diagnosis is presented in this project. The logic Built-In-Self-Test architecture method is extreme response compaction architecture. This architecture first time enables an autonomous on-chip evaluation of test responses with negligible hardware overhead. Architecture advantage is all data, which is relevant for a subsequent diagnosis, is gathered during just one test session. Due to some reasons, the existing method Built-In Self-Test is less often applied to random logic than to embedded memories. The generation of deterministic test patterns can become prohibitively high due to hardware overhead. The diagnostic resolution of compacted test responses is in many cases poor and the overhead required for an acceptable resolution may become too high. Modifications in Linear Feedback Shift Register to generate test pattern with security for modified Built-In-Self-Test applications with reduced power requirement. The modified Built-In-Self-Test circuit incorporates a fault syndrome compression scheme and improves the circuit speed with reduction of time.

Negative hydrogen ion production in a helicon plasma source

In order to develop very high energy (&amp;gt;1 MeV) neutral beam injection systems for applications, such as plasma heating in fusion devices, it is necessary first to develop high throughput negative ion sources. For the ITER reference source, this will be realised using caesiated inductively coupled plasma devices, containing either hydrogen or deuterium discharges, operated with high rf input powers (up to 90 kW per driver). It has been suggested that due to their high power coupling efficiency, helicon devices may be able to reduce power requirements and potentially obviate the need for caesiation due to the high plasma densities achievable. Here, we present measurements of negative ion densities in a hydrogen discharge produced by a helicon device, with externally applied DC magnetic fields ranging from 0 to 8.5 mT at 5 and 10 mTorr fill pressures. These measurements were taken in the magnetised plasma interaction experiment at the Australian National University and were performed using the probe-based laser photodetachment technique, modified for the use in the afterglow of the plasma discharge. A peak in the electron density is observed at ∼3 mT and is correlated with changes in the rf power transfer efficiency. With increasing magnetic field, an increase in the negative ion fraction from 0.04 to 0.10 and negative ion densities from 8 × 1014 m−3 to 7 × 1015 m−3 is observed. It is also shown that the negative ion densities can be increased by a factor of 8 with the application of an external DC magnetic field.

Nano Josephson superconducting tunnel junctions in YBa2Cu3O(7-δ) directly patterned with a focused helium ion beam.

Since the discovery of the high-transition-temperature superconductors (HTSs), researchers have explored many methods to fabricate superconducting tunnel junctions from these materials for basic science purposes and applications. HTS circuits operating at liquid-nitrogen temperatures (∼77 K) would significantly reduce power requirements in comparison with those fabricated from conventional superconductors. The difficulty is that the superconducting coherence length is very short and anisotropic in these materials, typically ∼2 nm in the a-b plane and ∼0.2 nm along the c axis. The electrical properties of Josephson junctions are therefore sensitive to chemical variations and structural defects on atomic length scales. To make multiple uniform HTS junctions, control at the atomic level is required. In this Letter we demonstrate all-HTS Josephson superconducting tunnel junctions created by using a 500-pm-diameter focused beam of helium ions to directly write tunnel barriers into YBa2Cu3O(7-δ) (YBCO) thin films. We demonstrate the ability to control the barrier properties continuously from conducting to insulating by varying the irradiation dose. This technique could provide a reliable and reproducible pathway for scaling up quantum-mechanical circuits operating at liquid-nitrogen temperatures, as well as an avenue to conduct novel planar superconducting tunnelling studies for basic science.

Investigation of Channel Coding Techniques for High Data Rate Mobile Wireless Systems

st century certainly belongs to a new wireless world. Be it voice or data communication, in every walk of life wireless is the call in this era. The need of the present scenario for wireless applications is the enhanced data rate for various applications of communication along with reduction in power requirements. But during message transferal, the data might get corrupted due to impairments of channels, affecting both the needs of data rate as well as power. Reduction of error due to noisy channels becomes critical. Here, channel coding comes out as bliss. These techniques are used for rendering reliable information through the transmission channel to the user. These approaches preserve data while it is being transported through channel. When error occurs, channel coding detects and corrects it and helps the communication systems design to reduce the noise effect during transmission. It is due to endowment of these coding techniques that we are today capable to reach near Shannon limits. The purpose of this paper is to study and analyze the performance and efficiency of different Forward error correcting (FEC) codes. Their improvement in performance is compared to tradeoffs in complexity and decoding lag. It has been observed that though selection of code is dependent on in-hand application but turbo codes outrun other codes in many aspects. Keywordsbo, Convolution, LDPC, RS codes.

Advanced Catalytic Igniters Technology for Small Compact Engine Applications

Development of technologies that allow small, high power density engines such as unmanned aerial vehicles (UAV), unmanned marine vehicles (UMV), and unmanned ground vehicles (UGV) to operate on single logistic fuel such as JP-8 is one of government goals. To advance this goal, a lightweight, compact, and retrofit capable ignition source is critical. Compared to standard spark igniters and noncatalytic glow plugs, the use of catalytic glow plugs will provide benefits of lower required compression ratio, improved igniter life, reduced electrical energy requirements, and overall reduction in system weight and size. Experimental testing demonstrated a significant increase in surface temperature (160+ °C) with impingement of a fuel spray compared to a conventional glow plug with engine testing demonstrating the use of catalyst allows stable engine operation at reduced power requirements. Computational analysis was performed to provide insight into the catalyst behavior. Analytical studies suggested increased stability due to both heat release due to exothermic catalytic reaction and production of reactive species. This technology would allow high power density engines to use heavy fuels, while potentially reducing electric power supply and engine complexity and weight, both of which would allow greater range and/or payload capacity. This paper discusses the feasibility of advanced igniters technology as an enabling component for the use of heavy fuels in small, high power density internal combustion engines. The paper presents and discusses analytical investigation, experimental test results, and durability testing data in an internal combustion engine environment.

Methods of Reducing the Power Requirements of Ventilation Systems. Part 5. Design of Ventilation Spaces in Transfer of Powder-Like Autohesion Materials1

A method of designing ventilation spaces in the case of transfer of powdery materials with enhanced autohesion properties is developed. Free falling streams of conglomerates and their flows in an impermeable trough are considered. The results obtained are useful in the design of efficient ventilation systems with reduced power requirements.

Percent per Degree Rule of Thumb for Refrigeration Cycle Improvement

A value of 1-1.5% power reduction per degree Fahrenheit (F) has been used successfully for years to estimate the effects of either lowering condenser temperature or raising evaporator temperature in a mechanical cooling system. This concept shows up in a variety of energy conservation measures, all with the goal of reducing power requirements. Reviewing the underlying science will allow confident use of this rule of thumb and explain the range of values given.The principles involved with this rule of thumb include lift, heat exchanger approach, coefficient of performance, refrigeration cycles, and sources of error. Since the work involves differences, pressure and temperature units do not have to be in absolutes. These terms and a Mollier Diagram (pressure-enthalpy, or p-h) were used to evaluate this rule of thumb.Manufacturer's data is the most accurate source of power reduction from a change in operating conditions because it captures all the various influences in a bottom-line live test. A Mollier (p-h) diagram can be used with before/after system conditions for good results. The rule of thumb can be used for reasonable accuracy, especially when incorporating the baseline lift (system lift before the change is made). Using the traditional 1-1.5% rule of thumb can overstate savings, but is ‘safe’ at the 1% level.

Voltage lowering and gain control techniques for a single-supply-driven 0.7 V amplifier

A CMOS amplifier architecture is presented with a voltage lowering technique so that it can be driven from a single 0.7 V bias supply. The topology does not need scaled gate voltages (or additional bias circuits) and uses branching of its bias path to reduce power requirement. A three-stage cascaded structure is adopted for high gain with the output common-drain block realizing a gain control mechanism. The technique achieves 6 dB gain regulation (with a control voltage) at the expense of small additional power (1.27 mW). A K-band architecture is simulated with a 90-nm CMOS process to verify the proposed mechanisms. The low-power (7.37 mW) unregulated front-end achieves 27 dB gain with a noise figure range of 2.99–3.06 dB within the 20.5–22.2 GHz bandwidth. Port reflection loss figures ( and ) are analysed to be −8 dB and −11 dB. The circuit has an area requirement of 0.62 mm2 and performs better in terms of power supply requirement and potential packaging cost when compared with simulated results of published millimetre-wave amplifiers.