Conversion Of Electronic Energy Research Articles

파도를 이용한 광대역 진동에너지 하베스터에 대한 연구

In general, existed vibration energy harvester is optimum in electronic energy gleaned from vibration energy with fixed single frequency, because it is using resonance. But it is limit in electronic energy gleaned from ocean wave energy with variant frequency. This paper studied for width band vibration energy harvester that obtains electronic energy from ocean wave with infinite vibration energy in order to solve it. It is composed of buoy to occur resonance in the center frequency of ocean wave energy and the vibration system to occur resonance in the same frequency. As a result, existed vibration energy harvester using resonance maximized electronic energy conversion efficiency in single frequency, while proposed width band vibration energy harvester has merit that maximized electronic energy conversion efficiency in ocean wave with variant frequency.

Design and Implementation of Digital Control in a Fuel Cell System

Digital control implementation is crucial in modern power electronic converters and energy conversion systems, as more complex control and friendly user interface are required. The fuel cell (FC) is a promising clean energy source and a reliable technology for niche applications providing high conversion efficiency. In this paper, a digitally controlled FC system is documented based on the boost-inverter topology that achieves both boosting and inversion functions in a single-stage. A digital signal processor TMS320F28335 is used to implement the control of the FC system in order to provide a number of benefits including low-cost, good performance, an easy implementation of a relatively complicated algorithm, and user friendly interface. The control design, analysis, simulation and experimental results are presented in the paper to confirm the performance of the digitally controlled FC system.

Phonon Dominated Heat Conduction Normal to Mo/Si Multilayers with Period below 10 nm

Thermal conduction in periodic multilayer composites can be strongly influenced by nonequilibrium electron-phonon scattering for periods shorter than the relevant free paths. Here we argue that two additional mechanisms-quasiballistic phonon transport normal to the metal film and inelastic electron-interface scattering-can also impact conduction in metal/dielectric multilayers with a period below 10 nm. Measurements use the 3ω method with six different bridge widths down to 50 nm to extract the in- and cross-plane effective conductivities of Mo/Si (2.8 nm/4.1 nm) multilayers, yielding 15.4 and 1.2 W/mK, respectively. The cross-plane thermal resistance is lower than can be predicted considering volume and interface scattering but is consistent with a new model built around a film-normal length scale for phonon-electron energy conversion in the metal. We introduce a criterion for the transition from electron to phonon dominated heat conduction in metal films bounded by dielectrics.

Revealing the structural origin of the redox-Bohr effect: the first solution structure of a cytochrome from Geobacter sulfurreducens

Gs (Geobacter sulfurreducens) can transfer electrons to the exterior of its cells, a property that makes it a preferential candidate for the development of biotechnological applications. Its genome encodes over 100 cytochromes and, despite their abundance and key functional roles, to date there is no structural information for these proteins in solution. The trihaem cytochrome PpcA might have a crucial role in the conversion of electronic energy into protonmotive force, a fundamental step for ATP synthesis in the presence of extracellular electron acceptors. In the present study, 15N-labelled PpcA was produced and NMR spectroscopy was used to determine its solution structure in the fully reduced state, its backbone dynamics and the pH-dependent conformational changes. The structure obtained is well defined, with an average pairwise rmsd (root mean square deviation) of 0.25Å (1Å=0.1nm) for the backbone atoms and 0.99Å for all heavy atoms, and constitutes the first solution structure of a Gs cytochrome. The redox-Bohr centre responsible for controlling the electron/proton transfer was identified, as well as the putative interacting regions between PpcA and its redox partners. The solution structure of PpcA will constitute the foundation for studies aimed at mapping out in detail these interacting regions.

Modeling and performance analysis of energy selective electron (ESE) engine with heat leakage and transmission probability

A model of an energy selective electron (ESE) engine with linear heat leakage and Lorentzian transmission probability is established in this paper. The expressions for the main performance parameters of the ESE engine operating as a heat engine or a refrigerator are derived by using the theory of finite time thermodynamics. The optimum performances of the ESE engine are explored and the influences of the heat leakage, the central energy level of the resonance, and the width of the resonance on the performance of the ESE engine are analyzed by using detailed numerical examples. The optimal operation regions of power output and efficiency (or cooling load and coefficient of performance (COP)) are also discussed. Moreover, the performances of the ESE engine with Lorentzian transmission probability are compared with those with rectangular transmission probability. It is shown that the power output versus efficiency (or cooling load versus COP) characteristic curves with and without heat leakage are all closed loop-shaped ones. The efficiency (or COP) of the ESE engine decreases as the heat leakage increases. It is found that as the resonance width increases, the power output and efficiency (or cooling load and COP) increase to a maximum and then decrease due to the finite range of energies which contribute positively to the power generation or refrigeration in the electron system. Especially, when heat leakage is taken into account, the characteristic curves of maximum efficiency (or maximum COP) versus half resonance width are parabolic-like ones, which are quite different from the monotonic decreasing characteristic curves obtained in previous analyses without considering heat leakage. The results obtained in this paper can provide some theoretical guidelines for the design and operation of practical electron energy conversion devices such as solid-state thermionic refrigerators.

Cage opening and fragmentation of C60 fullerene induced by an ultrashort laser pulse

Response of C60 fullerene to a 40 fs full-width at half-maximum laser pulse with a photon energy of 2.0 eV and different laser intensities is studied by semiclassical dynamics simulation technique. The simulation results show that soon after the irradiation with a strong laser pulse, many C–C bonds abruptly break but no fragments are produced. The breaking of multiple C–C bonds induces a quick increase in the kinetic energy and potential energy and a decrease in electronic energy. These results suggest that the opening of the C60 cage is an effective channel for the conversion of electronic energy to kinetic energy for the electronically excited C60 fullerene.

Improved Current Density with Al<SUB>2</SUB>O<SUB>3</SUB> Coated ZnO Nanorod in Hybrid Solar Cell

Heterojunction photovoltaic devices consisting of hybrid p-type organic Cu-phthalocyanine and inorganic n-type Al2O3 nanoparticle-coated aligned ZnO nanorods were fabricated. With microwave treatment, an interaction occurred between the Al2O3 and ZnO, as evidenced from TEM image. This interaction shifts the absorption peak of the aligned nanorods from the UV region to visible light and subsequently causes more charge generation. For 5 mol% Al2O3 nanoparticle-coated aligned ZnO nanorods treated with microwaves of 600 W for 300 sec, the maximum incident photon to electron conversion and energy conversion efficiencies under simulated sunlight of AM1.5G (10 mW/cm2) are 0.036 mA and 1.32%, respectively.

Positive anodic poised potential regulates microbial fuel cell performance with the function of open and closed circuitry

Positive influence of poised potential on microbial fuel cell (MFC) performance was observed with increase in the applied potential up to 600 mV and decreased thereafter. Higher power output (79.33 mW/m 2) was observed at 600 mV poised potential under open circuit operation (OC). Closed circuit operation (CC) showed almost negligible power output due to continuous electron discharge against an external load (100 Ω). However, CC operation resulted in the higher substrate (chemical oxygen demand (COD)) degradation [61.23% (control); 70.46% (OC; 600 mV); 74.15% (CC; 600 mV)] and total dissolved solids (TDS) removal [29.17% (control); 43.75% (OC; 600 mV); 72.92% (CC; 600 mV)] efficiencies compared to OC. Electron discharge and energy conversion efficiency was also observed to be higher with 600 mV poised potential. Poising potential showed additional redox couples (−0.29 ± 0.05 mV) on cyclic voltammetry. Application of poised potential during startup phase will help to enrich electrochemically active consortia on anode resulting in improved performance of MFC.

Using Fluorescence Dyes as a Tool for Analyzing the MALDI Process

In a recent paper (Setz, P. D.; Knochenmuss, R. Phys. Chem. A2005, 109, 4030-4037) energy-transfer from excited matrix molecules to fluorescent traps was used to study the role of pooling reactions for the ionization processes in matrix-assisted laser desorption ionization (MALDI) using 2,5-dihydroxybenzoic acid as matrix. Exciton trapping was shown to interfere with matrix ionization. These investigations were extended to analyze the influence of fluorescent traps on both matrix and analyte ions for alpha-cyano-4-hydroxycinnamic acid and further matrices. A strong influence of the fluorescent traps on both matrix and analyte ionization was revealed, depending on the matrix:trap ratio, and manifested itself differently for low and high mass analytes. The observations are rationalized by the intermediate formation of a "hot spot" due to an efficient conversion of electronic excitation energy to vibronic energy within the fluorescent traps. This process favors the desorption and ionization of small vaporizable analytes and compromises the cluster ablation process needed for larger analyte ions.

PWM Converter Power Density Barriers

Power density of power electronic converters in different applications has roughly doubled every 10 years since 1970. Behind this trajectory was the continuous advancement of power semiconductor device technology allowing an increase of converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts, and passive components and wire bond interconnection technologies could be major barriers for a continuation of this trend. For identifying and quantifying such technological barriers this paper investigates the volume of the cooling system and of the main passive components for the basic forms of power electronics energy conversion in dependency of the switching frequency and determines switching frequencies minimizing the total volume. The analysis is for 5 kW rated output power, high performance air cooling, advanced power semiconductors, and single systems in all cases. A power density limit of 28 kW/dm3@300 kHz is calculated for an isolated DC-DC converter considering only transformer, output inductor and heat sink volume. For single-phase AC-DC conversion a general limit of 35 kW/dm3 results from the DC link capacitor required for buffering the power fluctuating with twice the mains frequency. For a three-phase unity power factor PWM rectifier the limit is 45 kW/dm3@810 kHz just taking into account EMI filter and cooling system. For the sparse matrix converter the limiting components are the input EMI filter and the common mode output inductor; the power density limit is 71 kW/dm3@50 kHz when not considering the cooling system. The calculated power density limits highlight the major importance of broadening the scope of research in power electronics from traditional areas like converter topologies, and modulation and control concepts to cooling systems, high frequency electromagnetics, interconnection technology, multi-functional integration, packaging and multi-domain modeling and simulation to ensure further advancement of the field along the power density trajectory.

The effects of the guide field and tapered wiggler in free-electron laser

The interaction between electromagnetic field and electron beam was investigated numerically in a free-electron laser, using a new simulation code which consist of the three-dimensional electron motion, amplitude and phase of emitted radiation. The maintenance of the quality and stability of electron beam and the resonance condition through the wiggler is important to obtain the high gain and the high efficiency. But the electron orbits diverge and become unstable, and the resonance condition is not preserved because of the three-dimensional effects on the off-axis electron and the conversion of electron energy to electromagnetic field. To prevent those defects and improve the efficiency compared with the conventional case, we used the new methods such as the axial-guide field and tapered wiggler.

Toward Quantitative Prediction of Molecular Fluorescence Quantum Efficiency: Role of Duschinsky Rotation

It is a highly desirable but difficult task to predict the molecular fluorescence quantum efficiency from first principles. The molecule in the excited state can undergo spontaneous radiation, conversion of electronic energy to nuclear motion, or chemical reaction. For relatively large molecules, it is impossible to obtain the full potential energy surfaces for the ground state and the excited states to study the excited-state dynamics. We show that, under harmonic approximation by considering the Duschinsky rotation effect, the molecular fluorescence properties can be quantitatively calculated from first principles coupled with our correlation function formalism for the internal conversion. In particular, we have explained the peculiar fluorescence behaviors of two isomeric compounds, cis,cis-1,2,3,4-tetraphenyl-1,3-butadiene and 1,1,4,4-tetraphenyl-butadiene, the former being nonemissive in solution and strongly emissive in aggregation or at low temperature, and the latter being strongly emissive in solution. The roles of low-frequency phenyl ring twist motions and their Duschinsky mode mixings are found to be crucial, especially to reveal the temperature dependence. As an independent check, we take a look at the well-established photophysics of 1,4-diphenylbutadiene for its three different conformers. Both the calculated radiative and nonradiative rates are in excellent agreement with the available experimental measurements.

The role of large conformational changes in efficient ultrafast internal conversion: deviations from the energy gap law.

Conversion of electronic excitation energy into vibrational energy was investigated for photochromic spiropyran molecules, using femtosecond UV-mid-IR pump-probe spectroscopy. We observe a weaker energy gap dependence than demanded by the "energy gap law". We demonstrate that large conformational changes accompanying the optical excitation can explain the observed time scale and energy gap dependence of ultrafast S(1) --> S(0) internal conversion processes. The possibility of dramatic deviations from standard energy gap law behavior is predicted. We conclude that controlling molecular conformations by rigid environments can have a substantial impact on photophysical and (bio)chemical processes.

Nonequilibrium electron and phonon transport and energy conversion in heterostructures

We establish a unified model dealing with the transport of electrons and phonons in double heterojunction structures with the coexistence of three nonequilibrium processes: (1) nonequilibrium among electrons, (2) nonequilibrium among phonons, and (3) nonequilibrium between electrons and phonons. Using this model, we investigate the energy conversion efficiency based on concurrent thermoelectric and thermionic effects on electrons and size effects on electrons and phonons. It is found that heterostructures can have an equivalent figure of merit higher than the corresponding bulk materials.

Ultrafast spectroscopy studies on the mechanism of electron transfer and energy conversion in the isolated pseudo ginseng, water hyacinth and spinach chloroplasts

The spectroscopy characteristics and the fluorescence lifetime for the chloroplasts isolated from the pseudo ginseng, water hyacinth and spinach plant leaves have been studied by absorption spectra, low temperature steady-state fluorescence spectroscopy and single photon counting measurement under the same conditions and by the same methods. The similarity of the absorption spectra for the chloroplasts at room temperature suggests that different plants can efficiently absorb light of the same wavelength. The fluorescence decays in PS II measured at the natural QA state for the chloroplasts have been fitted by a three-exponential kinetic model. The three fluorescence lifetimes are 30, 274 and 805 ps for the pseudo ginseng chloroplast; 138, 521 and 1494 ps for the water hyacinth chloroplast; 197, 465 and 1459 ps for the spinach chloroplast, respectively. The slow lifetime fluorescence component is assigned to a collection of associated light harvesting Chl a/b proteins, the fast lifetime component to the reaction center of PS II and the middle lifetime component to the delay fluorescence of recombination of P+ 680 and Pheo-. The excitation energy conversion efficiency(η) in PS II RC is defined and calculated on the basis of the 20 ps electron transfer time constant model, 60%, 87% and 91% for the pseudo ginseng, water hyacinth and spinach chloroplasts, respectively. This interesting result is in unconformity with what is assumed to be 100% efficiency in PS II RC. Our result in this work stands in line with the 20 ps electron transfer time constant in PS II rather sound and the water hyacinth plant grows slower than the spinach plant does as envisaged on the efficiency. But, our results predict that those plants can perform highly efficient transfer of photo-excitation energy from the light-harvesting pigment system to the reaction center (closely to 100%). The conclusion contained in this paper reveals the plant growth characteristics expressed in the primary processes of photosynthesis and a relationship between a plant growing rate and its spectroscopy characteristics and fluorescence lifetimes, namely, the slower a plant grows, the less excitation energy conversation efficiency used might be anticipated.

Energy loss mechanisms in the microdischarges in plasma display panels

Low luminous efficacy is one of the major drawbacks of plasma display panels (PDPs), where the main limiting factor is the efficiency of the microdischarges in generating UV radiation. In this work we use a two-dimensional self-consistent fluid model to analyze the energy loss mechanisms in neon–xenon discharges in coplanar-electrode color PDPs and interpret experimental data on the luminous efficacy of these PDPs. The modeling results are in good agreement with the measured UV emission spectrum and measured trends in the efficacy. Most of the electrical input energy is transferred to ions and subsequently to the gas and the surface. The electrical energy transferred to electrons is mostly used for ionization and excitation, where the part used for xenon excitation largely ends up in UV radiation. The amplitude, frequency, and rise time of the driving voltage mainly affect the energy losses due to ion heating. The xenon content also affects the conversion of electron energy into UV energy.

Cluster fusion

Clustered materials strongly couple with intense laser radiation. The instantaneous conversion of laser energy into electron energy and subsequent conversion into ion energy leads to an efficient rapid laser energy injection into high energy (>10 keV) components of ions. This property of the laser-cluster interaction allows us to suggest compact ways to trigger nuclear fusion. A compact pulsed neutron source as well as a compact fusion reactor are considered.

Surface-induced dissociation of singly and multiply charged fullerene ions

Collisions of singly and multiply charged ions C60z+ (z=1,2,3,4,5) with a hydrocarbon-covered stainless steel surface have been investigated; product ions of fragmentation and pickup reactions were determined as a function of the collision energy (100–500 eV) and the projectile charge z. All ions scattered off the surface are singly charged. The extent of fragmentation increases with the collision energy and the projectile charge. However, the increase of fragmentation with the charge of the projectile is less pronounced than expected from a full conversion of electronic energy, gained in the neutralization process, into internal energy of the ion.

CCD detectors in high-resolution biological electron microscopy.

1. Introduction 11.1 The ‘band gap’ in silicon 22. Principles of CCD detector operation 32.1 Direct detection 32.2 Electron energy conversion into light 42.3 Optical coupling: lens or fibre optics? 62.4 Readout speed and comparison with film 83. Practical considerations for electron microscopic applications 93.1 Sources of noise 93.1.1 Dark current noise 93.1.2 Readout noise 93.1.3 Spurious events due to X-rays or cosmic rays 103.2 Efficiency of detection 113.3 Spatial resolution and modulation transfer function 123.4 Interface to electron microscope 143.5 Electron diffraction applications 154. Prospects for high-resolution imaging with CCD detectors 185. Alternative technologies for electronic detection 235.1 Image plates 235.2 Hybrid pixel detectors 246. References 26During the past decade charge-coupled device (CCD) detectors have increasingly become the preferred choice of medium for recording data in the electron microscope. The CCD detector itself can be likened to a new type of television camera with superior properties, which makes it an ideal detector for recording very low exposure images. The success of CCD detectors for electron microscopy, however, also relies on a number of other factors, which include its fast response, low noise electronics, the ease of interfacing them to the electron microscope, and the improvements in computing that have made possible the storage and processing of large images.CCD detectors have already begun to be routinely used in a number of important biological applications such as tomography of cellular organelles (reviewed by Baumeister, 1999), where the resolution requirements are relatively modest. However, in most high- resolution microscopic applications, especially where the goal of the microscopy is to obtain structural information at near-atomic resolution, photographic film has continued to remain the medium of choice. With the increasing interest and demand for high-throughput structure determination of important macromolecular assemblies, it is clearly important to have tools for electronic data collection that bypass the slow and tedious process of processing images recorded on photographic film.In this review, we present an analysis of the potential of CCD-based detectors to fully replace photographic film for high-resolution electron crystallographic applications.

Mechanisms for the desorption of large organic molecules. Part 2

Models are reviewed for ejection of intact biomolecules and biomolecular ions in response to the electronic energy deposited by a fast heavy ion. These models are compared with laboratory data and molecular dynamics calculations. Over a limited range of electronic energy deposited per unit path length, the scaling of the total yield with energy deposition is understood, and it has been shown that, except for Langmuir-Blodgett films of fatty acids, the large intact ions are ejected primarily from the surface or adsorbed sites. The principal outstanding problems are a detailed description of the electronic energy conversion into molecular motion and the ion formation—neutralization process. An understanding of these is needed in order to improve sensitivity at the higher masses in PDMS.