Minimum switching loss pulse width modulation for reduced power conversion loss in reactive power compensators

Advanced bus-clamping switching sequences, which employ an active vector twice in a subcycle, are used to reduce line current distortion and switching loss in a space vector modulated voltage source converter. This study evaluates minimum switching loss pulse width modulation (MSLPWM), which is a combination of such sequences, for static reactive power compensator (STATCOM) application. It is shown that MSLPWM results in a significant reduction in device loss over conventional space vector pulse width modulation. Experimental verification is presented at different power levels of up to 150 kVA.

Terbium(III)-cholate functionalized vesicles as luminescent indicators for the enzymatic conversion of dihydroxynaphthalene diesters

The phosphorescence intensity of unilamellar DOPC vesicles with embedded Tb3+-cholate complexes depends on the concentration of dihydroxynaphthalene (DHN) as sensitizer in solution. This was used to monitor the enzymatic conversion of DHN esters or DHN glucosides by enzymes in aqueous buffered solution.

Nanostructured electrode materials for electrochemical energy storage and conversion

Manipulation of matter at the nanoscale is a way forward to move beyond our current choices in electrochemical energy storage and conversion technologies with promise of higher efficiency, environmental benignity, and cost-effectiveness. Electrochemical processes being basically surface phenomena, tailored multifunctional nanoarchitecturing can lead to improvements in terms of electronic and ionic conductivities, diffusion and mass transport, and electron transfer and electrocatalysis. The nanoscale is also a domain in which queer properties surface: those associated with conversion electrodes, ceramic particles enhancing the conductivity of polymer electrolytes, and transition metal oxide powders catalyzing fuel cell reactions, to cite a few. Although this review attempts to present a bird's eye view of the vast literature that has accumulated in this rather infant field, it also lists a few representative studies that establish the beneficial effects of going `nano'. Investigations on nanostructuring and use of nanoparticles and nanoarchitectures related to lithium-ion batteries (active materials and electrolytes), supercapacitors (electrical double-layer capacitors, supercapacitors based on pseudo-capacitance, and hybrid supercapacitors), and fuel cells (electrocatalysts, membranes and hydrogen storage materials) are highlighted. (C) 2012 John Wiley & Sons, Ltd.

Nanorod to quantum dot conversion in ZnO dispersions with co-surfactants

A chemically-induced nanorod to quantum dot transition is reported in ZnO. This transition is achieved using co-surfactants in a marginally polar solvent in chimie douce (soft chemical) conditions. This is different from the physical instability driven transitions reported so far in metal nanowires and polymers. We propose a suitable mechanism for the observed phenomenon.

Active Power Decoupling with Reduced Converter Stress for Single-Phase Power Conversion and Interfacing

Single-phase DC/AC power electronic converters suffer from pulsating power at double the line frequency. The commonest practice to handle the issue is to provide a huge electrolytic capacitor for smoothening out the ripple. But, the electrolytic capacitors having short end of lifetimes limit the overall lifetime of the converter. Another way of handling the ripple power is by active power decoupling (APD) using the storage devices and a set of semiconductor switches. Here, a novel topology has been proposed implementing APD. The topology claims the benefit of 1) reduced stress on converter switches 2) using smaller capacitance value thus alleviating use of electrolytic capacitor in turn improving the lifetime of the converter. The circuit consists of a third leg, a storage capacitor and a storage inductor. The analysis and the simulation results are shown to prove the effectiveness of the topology.

Three-Dimensional Nanoarchitecture of BiFeO3 Anchored TiO2 Nanotube Arrays for Electrochemical Energy Storage and Solar Energy Conversion

Here, we report the synthesis of TiO2/BiFeO3 nano-heterostnicture (NH) arrays by anchoring BiFeO3 (BFO) particles on on TiO2 nanotube surface and investigate their pseudocapacitive and photoelectrochemical properties considering their applications in green energy fields. The unique TiO2/BFO NHs have been demonstrated both as energy conversion and storage materials. The capacitive behavior of the NHs has been found to be significantly higher than that of the pristine TiO2 NTs, which is mainly due to the anchoring of redox active BFO nanoparticles. A specific capacitance of about 440 F g(-1) has been achieved for this NHs at a current density of 1.1 A g(-1) with similar to 80% capacity retention at a current density of 2.5 A g(-1). The NHs also exhibit high energy and power performance (energy density of 46.5 Wh kg(-1) and power density of 1.2 kW kg(-1) at a current density of 2.5 A g(-1)) with moderate cycling stability (92% capacity retention after 1200 cycles). Photoelectrochemical investigation reveals that the photocurrent density of the NHs is almost 480% higher than the corresponding dark current and it shows significantly improved photoswitching performance as compared to pure TiO2 nanotubes, which has been demonstrated based the interfacial type-II band alignment between TiO2 and BFO.

Active Power Decoupling with Reduced Converter Stress for Single-Phase Power Conversion and Interfacing

Single-phase DC/AC power electronic converters suffer from pulsating power at double the line frequency. The commonest practice to handle the issue is to provide a huge electrolytic capacitor for smoothening out the ripple. But, the electrolytic capacitors having short end of lifetimes limit the overall lifetime of the converter. Another way of handling the ripple power is by active power decoupling (APD) using the storage devices and a set of semiconductor switches. Here, a novel topology has been proposed implementing APD. The topology claims the benefit of 1) reduced stress on converter switches 2) using smaller capacitance value thus alleviating use of electrolytic capacitor in turn improving the lifetime of the converter. The circuit consists of a third leg, a storage capacitor and a storage inductor. The analysis and the simulation results are shown to prove the effectiveness of the topology.

Investigations into the structural and down-shifting and up-conversion luminescence properties of Ba2Na1-3xErxNb5O15 (0 <= x <= 0.06) nanocrystalline phosphor synthesized via sol-gel route

The present work deals with the structural and efficient down-shifting (DS) and up-conversion (UC) luminescence properties of erbium ion (Er3+) doped nanocrystalline barium sodium niobate (Ba2Na1-3xErxNb5O15, where x = 0, 0.02, 0.04 and 0.06) powders synthesized via novel citrate-based sol-gel route. The monophasic nature of the title compound was confirmed via x-ray powder diffraction followed by FT-IR studies. High-resolution transmission electron microscopy (HRTEM) facilitated the establishment of the nanocrystalline phase and the morphology of the crystallites. The Kubelka-Munk function, based on diffused reflectance studies and carried out on nano-sized crystallites, was employed to obtain the optical band-gap. The synthesized nanophosphor showed efficient DS/PL-photoluminescence and UC luminescence properties, which have not yet been reported so far in this material. The material emits intense DS green emission on excitation with 378 nm radiation. Interestingly, the material gives intense UC emission in the visible region dominated by green emission and relatively weak red emission on 976 nm excitation (NIR laser excitation). Such a dual-mode emitting nanophosphor could be very useful in display devices and for many other applications.

Conversion of plastic waste into CNTs using Ni/Mo/MgO catalystAn optimization approach by mixture experiment

A combustion technique is used to study the synthesis of carbon nano tubes from waste plastic as a precursor and Ni/Mo/MgO as a catalyst. The catalytic activity of three components Ni, Mo, MgO is measured in terms of amount of carbon product obtained. Different proportions of metal ions are optimized using mixture experiment in Design expert software. D-optimal design technique is adopted due to nonsimplex region and presence of constraints in the mixture experiment. The activity of the components is observed to be interdependent and the component Ni is found to be more effective. The catalyst containing Ni0.8Mo0.1MgO0.1 yields more carbon product. The structure of catalyst and CNTs are studied by using SEM, XRD, and Raman spectroscopy. SEM analysis shows the formation of longer CNTs with average diameter of 40-50 nm.

Energy conversion in shape memory alloy heat engine - Part II: Simulation

In this paper, a theoretical model proposed in Part I (Zhu et al., 2001a) is used to simulate the behavior of a twin crank NiTi SMA spring based heat engine, which has been experimentally studied by Iwanaga et al. (1988). The simulation results are compared favorably with the measurements. It is found that (1) output torque and heat efficiency decrease as rotation speed increase; (2) both output torque and output power increase with the increase of hot water temperature; (3) at high rotation speed, higher water temperature improves the heat efficiency. On the contrary, at low rotation speed, lower water temperature is more efficient; (4) the effects of initial spring length may not be monotonic as reported. According to the simulation, output torque, output power and heat efficiency increase with the decrease of spring length only in the low rotation speed case. At high rotation speed, the result might be on the contrary.

GSPS photonic analogue to digital conversion system using broadband continuous wave source

An 80 GSPS photonic ADC system is demonstrated, using broadband MLL and dispersive fibre to form a continuous waveform with time-wavelength mapping, and AWG to channelise. Tests are carried out for RF signals up to 10GHz. © 2005 Optical Society of America.

Energy Conversion in Shape Memory Alloy Heat Engine Part I: Theory

Shape Memory Alloy (SMA) can be easily deformed to a new shape by applying a small external load at low temperature, and then recovers its original configuration upon heating. This unique shape memory phenomenon has inspired many novel designs. SMA based heat engine is one among them. SMA heat engine is an environment-friendly alternative to extract mechanical energy from low-grade energies, for instance, warm wastewater, geothermal energy, solar thermal energy, etc. The aim of this paper is to present an applicable theoretical model for simulation of SMA-based heat engines. First, a micro-mechanical constitutive model is derived for SMAs. The volume fractions of austenite and martensite variants are chosen as internal variables to describe the evolution of microstructure in SMA upon phase transition. Subsequently, the energy equation is derived based on the first thermodynamic law and the previous SMA model. From Fourier’s law of heat conduction and Newton’s law of cooling, both differential and integral forms of energy conversion equation are obtained.

First demonstration on the non-transparency of FWM and its application of 40 Gbit/s all-optical CSRZ-to-RZ format conversion

We report first experimental demonstration on the non-transparent characteristic of FWM using NRZ-DPSK, RZ-DPSK, CSRZ-DPSK, and CSRZ signals. One potential non-transparency application of 40Gbit/s CSRZ-to-RZ format conversion is experimentally demonstrated. © 2008 IEEE.

Un testigo directo de las tensiones religiosas en la Alejandría de los siglos IV y V D.C. : Páladas de Alejandría en la Antología Palatina

Abstract: Although he is the most prolific writer of the Greek Anthology, Palladas’ life is almost unknown. But, in spite of the limited biographical data, his work has fortunately been preserved in the GA. Because of his literary creation, the old times rewarded him with the nickname Μετέωρος, high, since the literary merits of a hundred poems of his authorship was recognized (others are discussed by critics). A dozen of them contains invaluable information about the political, religious and social situation in Alexandria immediately after the victory of the bishop Theophilus, Cyril’s predecessor and uncle, during the conflict between Christians and Gentiles, each sector backed up by an Alexandrian population segment (cfr. 9.528, 10.82, 10.85) . Resigned at times, constantly demanding, Palladas complains about the decline of the belief professed by him due to the increasing penetration of the new faith. Therefore, four epigrams record the conversion of the temple of Tyche into a tavern (9.180-183) and 10.90 seems to attack the doctrine of the Resurrection. When religion and politics go hand-in-hand, when religious conspiracies link up with palace intrigues, consequences are predictable: a man called Doroteo denounced him for his negative response to the new dogma, which caused him the loss of his teacher paid work. His annoyance was even greater with further sufferings, chiefly economic, and he had to sell his books (9.171 and 9.175) among other desperate decisions Forewarned about his radical bitterness against Church, it is just to make clear that he is not fully acquiescent with ancient gods and heroes. Thus, in 5.257 he questions Zeus’ ars amandi, in 9.377 refutes Tantalus’ possibility of thirst and hunger in Hades and 9.773 mischievously points out that Eros has been changed into a pan. The work begins with the selection, personal translation and comprehensive analysis of twenty two epigrams. Through such philological aid, we attempt to verify the frictions and the main perceptible factors in his poetic creation to justify his worldview, according to the pagan sentiment widespread in that time before the twilight already overwhelming of its ailing traditions