19,961 research outputs found
Power Quality Improvement Wind Energy System Using Cascaded Multilevel Inverter
In this paper, a wind energy conversion system based on a cascaded H-bridge multilevel inverter (CHBMLI) topology has been proposed to be used for the grid interface of large split winding alternators (SWAs). A new method has been suggested for the generation of reference currents for the voltage source inverter (VSI) depending upon the available wind power. The CHBMLI has been used as a VSI and operated in a current control mode order to achieve the objectives of real power injection and load compensation (power factor correction, load balancing, and harmonic compensation) based on the proposed reference generation scheme. In the ļ¬eld excitation control of SWA provides a single means vary the dc link voltages of all the CHBs simultaneously and proportionatel
Contra-rotating marine current turbines : single point tethered floating system - stabilty and performance
The Energy Systems Research Unit within the Department of Mechanical Engineering at the University of Strathclyde has developed a novel contra-rotating tidal turbine (CoRMaT). A series of tank and sea tests have led to the development and deployment of a small stand-alone next generation tidal turbine. Novel aspects of this turbine include its single point compliant mooring system, direct drive open to sea permanent magnet generator, and two contra-rotating sets of rotor blades. The sea testing of the turbine off the west coast of Scotland in the Sound of Islay is described; the resulting stability of a single-point tethered device and power quality from the direct drive generator is reported and evaluated. It is noted that reasonably good moored turbine stability within a real tidal stream can be achieved with careful design; however even quite small instabilities have an effect on the output electrical power quality. Finally, the power take-off and delivery options for a 250kW production prototype are described and assessed
Persediaan kerjaya pelajar tahun akhir diploma akauntansi Politeknik dalam melahirkan K-Workes : satu tinjauan
This research was conducted to identify Polytechnic's Diploma in Accountancy
final year students' career preparation before enter the working environment to be
k-workers. The sample in this study consisted of 48 final year students of Diploma in
Accountancy Politeknik Sultan Haji Ahmad Shah (POLISAS), Kuantan. Questionnaire
has been chosen as an instrument to get the data. The data was analyzed by using the
Statistical Package For Social Sciences (SPSS) package to derive the percentages and
mean. The results revealed the Diploma of Accountancy final year students are quite
prepared to enter the working environment. Although the students performed very well
for their career preparation, there are still dissatisfaction in other two aspects i.e. they
lack of information career opportunity and communication in English. Therefore, the
career guideline have been proposed to give an exposure for the students to be k-workers
in their career in the future
Homogeneous Spiking Neuromorphic System for Real-World Pattern Recognition
A neuromorphic chip that combines CMOS analog spiking neurons and memristive
synapses offers a promising solution to brain-inspired computing, as it can
provide massive neural network parallelism and density. Previous hybrid analog
CMOS-memristor approaches required extensive CMOS circuitry for training, and
thus eliminated most of the density advantages gained by the adoption of
memristor synapses. Further, they used different waveforms for pre and
post-synaptic spikes that added undesirable circuit overhead. Here we describe
a hardware architecture that can feature a large number of memristor synapses
to learn real-world patterns. We present a versatile CMOS neuron that combines
integrate-and-fire behavior, drives passive memristors and implements
competitive learning in a compact circuit module, and enables in-situ
plasticity in the memristor synapses. We demonstrate handwritten-digits
recognition using the proposed architecture using transistor-level circuit
simulations. As the described neuromorphic architecture is homogeneous, it
realizes a fundamental building block for large-scale energy-efficient
brain-inspired silicon chips that could lead to next-generation cognitive
computing.Comment: This is a preprint of an article accepted for publication in IEEE
Journal on Emerging and Selected Topics in Circuits and Systems, vol 5, no.
2, June 201
Reactive Atom Plasma (RAP) figuring machine for meter class optical surfaces
A new surface figuring machine called Helios 1200 is presented in this paper. It is designed for the figuring of meter sized optical surfaces with form accuracy correction capability better than 20 nm rms within a reduced number of iterations. Unlike other large figuring facilities using energy beams, Helios 1200 operates a plasma torch at atmospheric pressure, offers a high material removal rate, and a relatively low running cost. This facility is ideal to process large optical components, lightweight optics, silicon based and difficult to machine materials, aspheric, and free form surfaces. Also, the surfaces processed by the reactive atom plasma (RAP) are easy to fine polish through hand conventional sub-aperture polishing techniques. These unique combined features lead to a new capability for the fabrication of optical components opening up novel design possibilities for optical engineers. The key technical features of this large RAP machine are fast figuring capabilities, non-contact material removal tool, the use of a near Gaussian footprint energy beam, and a proven tool path strategy for the management of the heat transfer. Helios 1200 complies with the European machine safety standard and can be used with different types of reactive gases using either fluorine or chlorine compounds. In this paper, first the need for large optical component is discussed. Then, the RAP facility is described: radio frequency R.F generator, plasma torch, and 3 axis computer numerically controlled motion system. Both the machine design and the performance of the RAP tool is assessed under specific production conditions and in the context of meter class mirror and lens fabrication
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Diagnostic Applications for Micro-Synchrophasor Measurements
This report articulates and justifies the preliminary selection of diagnostic applications for data from micro-synchrophasors (ĀµPMUs) in electric power distribution systems that will be further studied and developed within the scope of the three-year ARPA-e award titled Micro-synchrophasors for Distribution Systems
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