Terms Of Energy Transfer Research Articles

The variability, structure and energy conversion of the northern hemisphere traveling waves simulated in a Mars general circulation model

Investigations of the variability, structure and energetics of the m=1−3 traveling waves in the northern hemisphere of Mars are conducted with the MarsWRF general circulation model. Using a simple, annually repeatable dust scenario, the model reproduces many general characteristics of the observed traveling waves. The simulated m=1 and m=3 traveling waves show large differences in terms of their structures and energetics. For each representative wave mode, the geopotential signature maximizes at a higher altitude than the temperature signature, and the wave energetics suggests a mixed baroclinic-barotropic nature. There is a large contrast in wave energetics between the near-surface and higher altitudes, as well as between the lower latitudes and higher latitudes at high altitudes. Both barotropic and baroclinic conversions can act as either sources or sinks of eddy kinetic energy. Band-pass filtered transient eddies exhibit strong zonal variations in eddy kinetic energy and various energy transfer terms. Transient eddies are mainly interacting with the time mean flow. However, there appear to be non-negligible wave-wave interactions associated with wave mode transitions. These interactions include those between traveling waves and thermal tides and those among traveling waves.

Efficient evaluation of collisional energy transfer terms for plasma particle simulations

Particle-based simulations, such as in particle-in-cell (PIC) codes, are widely used in plasma physics research. The analysis of particle energy transfers, as described by the second moment of the Boltzmann equation, is often necessary within these simulations. We present computationally efficient, analytically derived equations for evaluating collisional energy transfer terms from simulations using discrete particles. The equations are expressed as a sum over the properties of the discrete particles.

A high performance desiccant dehumidification unit using solid desiccant coated heat exchanger with heat recovery

A new type of solid desiccant dehumidification cycle with internal heat recovery based sorptive material coated heat exchanger (SCHE) is proposed. This system can realize waste heat recovery from exhausted air in regeneration process, in which a heat recovery device (HRD) is adopted. The performance evaluation of the novel cycle is compared with that of the conventional cycle without HRD in terms of moisture and energy transfer. Based on the experimental results, the thermal coefficient of performance of the system has been improved to 1.2, almost twice the thermal coefficient of performance of the conventional cycle without HRD. The electrical coefficient of performance can reach about 13.83. When HRD is involved in the system, the supply air temperature is close to the inlet temperature of process air (ambient air), dehumidification capability meets the design requirements (lower than 8gkg−1) and the regeneration temperature can satisfy the regeneration requirement of low grade heat source. The thermal efficiency of the HRD is calculated as 0.88 on average. As a conclusion, SCHE with HRD system could be a potential alternative with effective operation which can be promoted in higher humidity and temperature areas.

Modulating fluorescence quantum yield of highly concentrated fluorescein using differently shaped green synthesized gold nanoparticles

The interaction of dye molecules with differently shaped nanoparticles is of great interest owing to the potential applications in areas of bioimaging, sensing and photodynamic therapy (biology) as well as solar cells (photonics) applications. For such applications, noble metallic nanoparticles are commonly employed to either enhance or quench the luminescence of a nearby fluorophore. However, in most of the studies, the dye concentration is limited to avoid self-quenching. This paper reports the influence of differently shaped gold nanoparticles (spherical, bean and star), prepared via green synthesis, on the emission behavior as well as on the fluorescence quantum yield of fluorescein dye at concentrations for which self-quenching occurs. The emission behavior is probed via laser based steady state fluorescence whereas quantum yield is measured using a dual beam laser based thermal lens technique. The experimentally observed fluorescence quenching with a concomitant increase in thermal lens signal in the vicinity of nanoparticles are explained in terms of nonradiative energy transfer between the donor and the acceptor. Further, the influence of pH of the prepared gold nanofluid on the absorption, emission as well as quantum yield are also accounted. These studies elucidate that even at high concentrations of dye, the gold nanoparticle and its shape clearly influences the optical properties of nearby dye molecules and thus can be exploited for future applications.

Formation of the bi-directional energy cascade in low-frequency damped wave-turbulent systems

We demonstrate that in wave-turbulent systems, an inverse energy flux can be formed in addition to the conventional direct energy flux if large-scale wave damping is present. Such a bi-directional energy cascade can be understood in terms of the wave energy transfer on the temperature wave background. The formation of the bi-directional cascade provides an effective mechanism for global coupling between the scales where the turbulent fluctuations at small scales are affected by the wave distribution at large scales due to the total energy conservation. We discuss physical systems where this scenario is realized.

Energy cooperation for throughput optimization based on save-then-transmit protocol in wireless communication system

Green communication and energy saving have been a critical issue in modern wireless communication systems. The concepts of energy harvesting and energy transfer are recently receiving much attention in academic research field. In this paper, we study energy cooperation problems based on save-then-transmit protocol and propose two energy cooperation schemes for different system models: two-node communication model and three-node relay communication model. In both models, all of the nodes transmitting information have no fixed energy supplies and gain energy only via wireless energy harvesting from nature. Besides, these nodes also follow a save-then-transmit protocol. Namely, for each timeslot, a fraction (referred to as save-ratio) of time is devoted exclusively to energy harvesting while the remaining fraction is used for data transmission. In order to maximize the system throughput, energy transfer mechanism is introduced in our schemes, i.e., some nodes are permitted to share their harvested energy with other nodes by means of wireless energy transfer. Simulation results demonstrate that our proposed schemes can outperform both the schemes with half-allocate save-ratio and the schemes without energy transfer in terms of throughput performance, and also characterize the dependencies of system throughput, transferred energy, and save-ratio on energy harvesting rate.

Biologically inspired band-edge laser action from semiconductor with dipole-forbidden band-gap transition

A new approach is proposed to light up band-edge stimulated emission arising from a semiconductor with dipole-forbidden band-gap transition. To illustrate our working principle, here we demonstrate the feasibility on the composite of SnO2 nanowires (NWs) and chicken albumen. SnO2 NWs, which merely emit visible defect emission, are observed to generate a strong ultraviolet fluorescence centered at 387 nm assisted by chicken albumen at room temperature. In addition, a stunning laser action is further discovered in the albumen/SnO2 NWs composite system. The underlying mechanism is interpreted in terms of the fluorescence resonance energy transfer (FRET) from the chicken albumen protein to SnO2 NWs. More importantly, the giant oscillator strength of shallow defect states, which is served orders of magnitude larger than that of the free exciton, plays a decisive role. Our approach therefore shows that bio-materials exhibit a great potential in applications for novel light emitters, which may open up a new avenue for the development of bio-inspired optoelectronic devices.

H2Odouble ionization induced by electron impact

Double ionization of water molecules remains, still today, rarely investigated on both the experimental and the theoretical side. In this context, the present work reports on a quantum mechanical approach providing a quantitative description of the electron-induced double ionization process on isolated water molecules for impact energies ranging from the target ionization threshold up to about 10 keV. The cross section calculations are here performed within the first Born approximation framework in which the initial state of the system includes a molecular ground-state wave function expressed as a single-center linear combination of atomic orbitals while the final state of the system is characterized by two independent Coulomb wave functions used for describing the two ejected electrons coupled by a Gamov factor used for modeling the electron-electron repulsion. Besides, in order to go beyond the first Born approximation, the scattered electron is considered as a particle being in the Coulomb field of the nucleus---whose charge is screened by the ejected electrons---and then treated by an approximate Coulomb wave function. In this perturbative-type description, let us add that the passive (not ionized) electrons are considered as frozen in their molecular orbitals during the collision which permits to reduce the electron-target interaction potential to a two-active-electron problem. Comparisons with rare available experimental data are reported as well an energetic analysis in terms of mean secondary energy transfer during the double ionization process in order to demonstrate the relevance of the electron-induced double ionization process.

Symmetry-Related Transitions in the Photoluminescence and Cathodoluminescence Spectra of Nanosized Cubic Y2O3:Tb3+

Herein the photoluminescence spectra of nanosized cubic Y2O3:Tb3+ having Tb3+ concentrations varying between 0.1 and 10 Mol% are described. Low temperature cathodoluminescence spectra from these materials recorded in a scanning transmission electron microscope are presented and discussed. By studying the photoluminescence-spectra recorded at room temperature and focused on the 5D4→7F5 (C2) and 5D4→7F5 (C3i) transitions, at 542.8 and 544.4 nm respectively, it was found that the critical distance for energy transfer from Tb3+ ions at C3i lattice sites to Tb3+ ions at C2 lattice sites was 1.7 nm; at distances >1.7 nm, which prevail at low Tb3+ concentration, this energy transfer virtually stops. The gradual change of the excitation spectra upon increasing the Tb3+ concentration is also explained in terms of energy transfer from Tb3+ at C3i sites to Tb3+ at C2 sites. Cathodoluminescence spectra recorded at low temperatures with the scanning transmission electron microscope provided additional evidence for this radiationless energy transfer.

Zero-Energy Buildings-A Review

A zero-energy building (ZEB), which is an autonomous building energy option, is defined as a building that produces as much energy as it uses from renewable energy sources at the site. Zero-energy buildings can exchange energy with the power grid as long as the net energy balance is zero on an annual basis.In terms of the thermal energy transfer and storage, zero-energy buildings can achieve annual energy consumption levels down to 0 kWh per square metre through the use of renewable energy sources, which compares favourably with the passive house energy criteria per square metre. Energy plus houses, in contrast with both the passive houses and zero-energy buildings, focus on producing more energy per year than they consume, which can lead to an annual energy performance of -25 kWh per square metre. Zero-energy buildings should have features like: i) Enable building owners to be isolated from fluctuating energy prices through the on or off-grid renewable energy supply ii) Help reduce peak electrical demand by self-supplying energy demands on site iii) Go hand in hand with the transformation of energy infrastructure and market. Zero-energy buildings can be achieved by incorporating energy efficiency measures and on-site renewable energy generation technologies and its energy efficiency measures include: creating a high-performance building envelope, installing energy efficient appliances and lights, increasing the use of passive solar cooling and heating techniques and installing high-efficiency mechanical systems that match the lower energy requirements of the home. On-site renewable energy generation systems can be available within a building’s footprint by using PVs, solar hot water and wind located on the building or at the site by means of PVs, solar hot water, low impact hydro and wind located on-site not on the building. Zero-energy building is still in the conceptual stage in the Asia-Pacific region. A few pilot projects have been applied to public buildings, such as research institutes, for demonstration purpose e.g., Sustainable Energy Technology Centre in China, Pusat Tenaga Malaysia’s Zero Energy Office (ZEO) Building and National Institution of Environmental Research in Republic of Korea.

Optimal Energy Transfer Pipe Arrangement for Acoustic Drill String Telemetry

Drill string acoustic telemetry is an effective transmission method to retrieve downhole data. Finite-difference simulations produce the comb-filter-like channel response (patterns of pass bands and stop bands) due to the presence of coupling joints in the metallic drill string. Practical pipes used for drilling deep wells have slight variation in length. The selection and arrangement of downhole pipes is important for improving the transmission efficiency of extensional waves transmitted through the drill string. Downhole drill string channel is studied using the transmission coefficients calculated from the transmission matrix method, and the resultant transfer function produces identical results similar to the finite-difference simulations. Reciprocity of the drill string structure is proved by comparing the pass band responses using the ascend-only (AO) and descend-only pipe arrangements. Transferred energies calculated up to 180 pipes of random length at the end of the drill strings using transmission coefficients for the three different pipe arrangements, namely, AO, descend-then-ascend, and ascend-then-descend (ATD), are compared to find the optimal pipe arrangement for single measurement. For the situations when pipes are distributed in sets, multiple measurements are required. In this paper, two sets of AO and two sets of ATD arrangements are analyzed for multiple measurements. ATD and $n$ xATD arrangements are proposed as optimal pipe arrangements to produce the best possible telemetry performance in terms of optimal acoustic energy transfer via one- and two-way acoustic communication for single and multiple measurements, respectively.

Experiments on Gliding Discharge Configuration for Plasma-Assisted Combustion

Gliding discharges are of interest to be used to assist combustion processes, one reason being their ability to transit from the thermal arc mode to a nonthermal discharge mode. We report on experiments performed with a gliding discharge in a forced flow of ambient air to study the discharge mode and discharge behavior when the impedance of the discharge channel is matched to the inner impedance of the power source. Our discharge remained in the arc mode and a higher flow rate of the externally forced airflow gave better performance in terms of energy transfer to the discharge channel.

Simultaneous light emissions from erbium-thulium silicates and oxides on silicon in the second and third telecommunications bands

We demonstrate simultaneous light emissions in O (1260-1360 nm), S (1460-1530 nm), and C (1530-1565 nm) telecommunications bands from films composed of mixtures of polycrystalline Er2xTm2-2xSiO5 and Er2xTm2-2xSi2O7 and of polycrystalline Er2xTm2-2xO3 grown by radio frequency (rf) magnetron sputtering using polycrystalline Tm2O3, Er2O3 and SiO2 targets on Si(100) substrates. Photons are emitted in the O and S + C bands when the samples are optically excited at 532 nm and in the S and C bands when excited at 785 nm. The simultaneous dual-wavelength light emissions are discussed in terms of energy transfers between Er3+ and Tm3+ ions in the polycrystalline Er-Tm compounds.

A rapid and sensitive resonance Rayleigh scattering spectra method for the determination of quinolones in human urine and pharmaceutical preparation

A new method based on resonance Rayleigh scattering (RRS) was proposed for the determination of quinolones (QNS) at the nanogram level. In pH 3.3-4.4 Britton-Robinson buffer medium, quinolones such as ciprofloxacin, pipemidic acid (PIP), lomefloxacin (LOM), norfloxacin (NOR) and sarafloxacin (SAR) were protonated and reacted with methyl orange (MO) to form an ion-pair complex, which then further formed a six-membered ring chelate with Pd(II). As a result, new RRS spectra appeared and the RRS intensities were enhanced greatly. RRS spectral characteristics of the MO-QNS-Pd(II) systems, the optimum conditions for the reaction, and the influencing factors were investigated. Under optimum conditions, the scattering intensity (∆I) increments were directly proportional to the concentration of QNS with in certain ranges. The method had high sensitivity, and the detection limits (3σ) ranged from 6.8 to 12.6 ng/mL. The proposed method had been successfully applied for the determination of QNS in pharmaceutical formulations and human urine samples. In addition, the mechanism of the reaction system was discussed based on IR, absorption and fluorescence spectral studies. The reasons for the enhancement of scattering spectra were discussed in terms of fluorescence-scattering resonance energy transfer, hydrophobicity and molecular size.

Photosystem II activity in the leaves and assimilative branches of Alhagi sparsifolia Shap. under brief elevated temperature

Leaves and assimilative branches are crucial to the life cycle of Alhagi sparsifolia Shap. that is one of the main shrubs in the southern fringe of the Taklamakan desert. They reduce photosynthesis at midday during summer and exhibit different degrees of adaptability to severe environments. We investigated the changes in the PSII activity of leaves and assimilative branches of under elevated temperature and whether they have the same response and level of tolerance to different temperatures, thus to understand the roles of leaves and assimilative branches of A. sparsifolia in global warming. In this study, the kinetics of induced chlorophyll a fluorescence under heat-stress-induced inhibition of photosystem II in leaves and assimilative branches of A. sparsifolia after 15 min of treatment was investigated. The results show that both the activity and density of reaction centers of leaves are higher than assimilative branch at 35–48 °C, and both in the leaves and assimilative branches were decreased above 45 °C, the assimilative branches adapted better to the severe environment in terms of light energy transfer, light usage efficiency, and electron transport at 52 °C. Assimilative branches had better adaptability to elevated temperature than leaves of A. sparsifolia suggesting that assimilative branches might be more adaptive to severe environment.

Effects of Cl− on spectroscopy properties of methyl orange containing silver nanoparticles

In this article, the authors studied the effect of Cl− on the fluorescence of methyl orange solution containing silver nanoparticles by UV–visible absorption spectra, fluorescence spectra, and transmission electron microscopy. The results indicated that there is little change in the UV–visible absorption spectra of methyl orange after adding Cl− into the mixed solutions of the methyl orange and silver colloid. With the increase in Cl− content, the fluorescence of S1→S0 decreases first and then increases, and the fluorescence of S2→S0 increases, which almost has nothing to do with the pH value of methyl orange solution. The fluorescence enhancement ratio of S1→S0 in the solution of pH = 6.1 was higher than that in the solution of pH = 2.1. The authors discussed the mechanism of the effect of Cl− on the fluorescence of methyl orange solution containing silver nanoparticles in terms of interaction and energy transfer. The results indicated that the effect of Cl− on the fluorescence of methyl orange solution containing silver nanoparticles depends on the bridge role and the competitive adsorption between nanoparticles and methyl orange molecules, molecular adsorption mode, and so on.

Intramolecular photoinduced reactions in corrole–pyrene and corrole–fluorene dyad systems

We have designed and synthesized donor–acceptor conjugates in which donor polycyclic aromatic hydrocarbons such as either pyrene or fluorene linked at the pyrrole-β position of a corrole using vinylene spacer. Both the dyads are characterized by elemental analysis, MALDI-MS, 1H NMR, UV–vis and fluorescence spectroscopy (steady-state and time-resolved) as well as electrochemical method. The Soret absorption band of corrole was split in both the dyads and more over both Soret and Q bands are red-shifted by 15–25 nm as compared to the unsubstituted corrole. Ground state properties indicate that there is a moderate π–π interactions in these dyad systems. However, fluorescence emission of polycyclic aromatic hydrocarbons of both the dyads quenched significantly (88–98%) compared to their monomeric units. The quenched emission was attributed in terms of intramolecular excitation energy transfer, which competes with the photoinduced electron transfer reaction in these dyads.

Phase contrast and operation regimes in multifrequency atomic force microscopy

In amplitude modulation atomic force microscopy the attractive and the repulsive force regimes induce phase shifts above and below 90°, respectively. In the more recent multifrequency approach, however, multiple operation regimes have been reported and the theory should be revisited. Here, a theory of phase contrast in multifrequency atomic force microscopy is developed and discussed in terms of energy transfer between modes, energy dissipation and the kinetic energy and energy transfer associated with externally driven harmonics. The single frequency virial that controls the phase shift might undergo transitions in sign while the average force (modal virial) remains positive (negative).

Characteristics of energy transfer in disc and fibre laser

Characteristics of energy transfer of two laser systems, fibre and disc lasers, are studied in this paper. Laser induced plasma is characterised by estimating the electron temperature and the electron density in both laser systems. Based on the electron temperature and electron density, the coefficients of inverse Bremsstrahlung absorption are estimated to investigate the energy absorption by the plasma in both systems. The electron temperature is evaluated from the observed Fe I emission lines using Boltzmann plot, whereas the electron number density is determined from the broadened line of Fe I 381·58 nm. The penetration characteristics in both systems are examined to study the role of the attenuated beam by the plasma absorption. Based on the observed features, the performance of the disc and fibre lasers, in terms of energy transfer, are comparable. However, in high power densities, the disc laser has slightly deeper penetration.

Two dimensional numerical prediction of deflagration-to-detonation transition in porous energetic materials

This paper describes a two-dimensional code developed for analyzing two-phase deflagration-to-detonation transition (DDT) phenomenon in granular, energetic, solid, explosive ingredients. The two-dimensional model is constructed in full two-phase, and based on a highly coupled system of partial differential equations involving basic flow conservation equations and some constitutive relations borrowed from some one-dimensional studies that appeared in open literature. The whole system is solved using an optimized high-order accurate, explicit, central-difference scheme with selective-filtering/shock capturing (SF-SC) technique, to augment central-diffencing and prevent excessive dispersion. The sources of the equations describing particle-gas interactions in terms of momentum and energy transfers make the equation system quite stiff, and hence its explicit integration difficult. To ease the difficulties, a time-split approach is used allowing higher time steps. In the paper, the physical model for the sources of the equation system is given for a typical explosive, and several numerical calculations are carried out to assess the developed code. Microscale intergranular and/or intragranular effects including pore collapse, sublimation, pyrolysis, etc. are not taken into account for ignition and growth, and a basic temperature switch is applied in calculations to control ignition in the explosive domain. Results for one-dimensional DDT phenomenon are in good agreement with experimental and computational results available in literature. A typical shaped-charge wave-shaper case study is also performed to test the two-dimensional features of the code and it is observed that results are in good agreement with those of commercial software.