Total Energy Transfer Efficiency Research Articles

Food Web Structure and Ecosystem Functions of the Water Source in the Middle Route of China’s South-to-North Water Diversion Project

The Danjiangkou Reservoir is the water source of the middle route of China’s South-to-North Water Diversion Project, encompassing the Dan Reservoir and Han Reservoir. However, little is known about the ecological functions of this important ecosystem. Based on a survey conducted in 2023 in the Dan Reservoir, a mass balance model was constructed using Ecopath with Ecosim 6.6 software to characterize its food web structure and ecosystem properties. The model consisted of 18 functional groups, including producers, consumers, and detritus, covering the entire process of energy flow in the ecosystem. The outputs indicated that the fractional trophic level of functional groups in the Dan Reservoir ecosystem ranged from 1.00 to 3.50. The ecotrophic efficiencies of the main economic fish species were all less than 0.9, and the ecotrophic efficiencies of phytoplankton and detritus were less than 0.5. There were two main food chains: the detritus food chain (39%) and the grazing food chain (61%). The total energy transfer efficiency between trophic levels was only 6.02%, and there was a significant phenomenon of energy transfer blockage between trophic levels II and V. Analysis of the overall characteristics of the ecosystem revealed that the total primary production to total biomass (67.96619), connectance index (0.274), and Finn’s cycling index (2.856) of the Dan Reservoir ecosystem all indicate that the ecosystem is immature, with low nutrient recycling efficiency and poor resistance to external disturbances. This may be related to the low proportion of silver carp and bighead carp in the reservoir and the unreasonable structure of the fish community. Our results suggest that it is necessary to scientifically adjust the structure of the fish community, enhance the proportion of filter-feeding and omnivorous fish to improve the energy flow efficiency, and promote the maturity and stability of the Dan Reservoir.

Coupling charge pump and BUCK circuits to efficiently enhance the output performance of triboelectric nanogenerator

Triboelectric nanogenerator (TENG) faces significant challenges in practical applications because of its low output charge density and high matching impedance, and the development of its energy management circuits is hindered by high initial device requirements, large circuit size and poor portability. In this work, we propose a simple, efficient and versatile energy management strategy that two-stage amplification of TENG output performance by coupling a charge pump circuit with a BUCK circuit. By implementing the energy management strategy, the charge output per cycle of an ordinary TENG can be increased by more than 40 times, resulting in a power density of 25.2 mWm−2 and a total energy transfer efficiency of exceeding 88% in constant mode. At a working frequency of 1 Hz, the TENG can charge a 1000 μF capacitor to 5.04 V in 240 s and store the energy of more than 12.72 mJ, of which represents an 848-fold increase in stored energy compared to using TENG directly. Remarkably, this TENG device exhibits exceptional an average power of 100.7 μW/Hz, setting a new record for devices with smaller TENG size (< 50 cm2) or limited PM circuit size (< 10 cm2). Moreover, an ordinary TENG can continuously power a wireless sensor by integrating the portable power management circuit, facilitating real-time wireless data transmission. This study is of great significance for the practical application of the TENG power supply in the sensor network of the Internet of Things and for expanding the application range of the TENG.

Triboelectric charge modulation to understand the electrification process in nanogenerators combined with an efficient power management system for IoT applications

Mechanical energy harvesting from ambient environment has been considered one of the promising technologies for developing autonomous self-powering units, sensors, and various other electronic applications. Triboelectric nanogenerators (TENGs) are one of the recent technologies gaining tremendous interest because of their ability to efficiently harvest ambient energy and convert it into electricity. The phenomenon of the triboelectrification effect in TENGs is not fully understood, along with extracting a maximum electrical output. Herein, we studied the electrification process between two triboelectric films by modulating their charge polarity. The charge polarity in the triboelectric film was modulated without any surface chemical functionalization. A TENG was fabricated to experimentally study the electrification process. Initially, the accepting/donating electrons of a triboelectric film were modulated using fluorine and oxygen atoms contained in polymers and operated against an oppositely charged triboelectric film. After optimizing the electrical output and conducting various stability investigations, the electrical output from the TENG was enhanced. Ultra-low power management integrated circuit (PMIC) implemented in a 180 nm high-voltage BCD (Bipolar CMOS DMOS) process was used. While matching the effective impedance of the TENGs, the PMIC achieves a total energy transfer efficiency of 81.5% utilizing a relatively low input power of 6.5 µW, showing state-of-the-art performance.

Numerical Study of Composite Percussive Drilling With Consideration of Heat Transfer Between Drilling Fluid and Bottom-Hole Rock in Geothermal Drilling

Abstract This article conducted a numerical study of composite percussive drilling with consideration of heat transfer between drilling fluid and bottom-hole rock in geothermal drilling, and analyzed influences of temperature, impact parameters, and heat transfer on rock fragmentation characteristics and energy transfer patterns. In this article, a model for a percussive drilling system based on the coupling of composite percussion and heat transfer was built. The rock fragmentation mechanism and energy transfer efficiency under the coupling of composite percussion and thermal exchange were studied. The main study results are as follows. As the temperature enhances, the total energy transfer efficiency declines, and the tensile damage area shrinks, while the outward extension of tensile cracks enhances. The total energy transfer efficiency enhances with the increase of the heat flux. The thermal load of the rock caused by heat transfer is essentially tensile stress. As the heat flux enhances, the tensile damage areas of the rock gradually expand and interconnect. Under the couplings of composite percussion and heat transfer, the heat transfer can intensify the rock breakage by tensile stress and enhance the energy transfer efficiency, and large deformation of the rock generated by composite percussion can promote the heat transfer process of drilling fluid and high-temperature rock, which in turn enhances the rock thermal damage. This study reveals coupling mechanisms of composite percussion and heat transfer and provides parameter optimization basis for composite percussive drilling in geothermal well.

Energy transfer fluctuation observed by single-molecule spectroscopy of red-shifted bacteriochlorophyll in the homodimeric photosynthetic reaction center.

The photosynthetic reaction center of heliobacteria (hRC) is a homodimeric chromoprotein responsible for light harvesting and photoelectric conversion. The fluorescence of the hRC is radiated from a bacteriochlorophyll (Bchl) g having the lowest energy level, called red-Bchl g. The homodimeric architecture of the hRC indicates that it includes two red-Bchls g arranged symmetrically in pairs. Red-Bchl g is a fluorescent probe useful for monitoring the energy transfer network in the RC. Here, we show the fluorescence polarization dependences of two red-Bchls g, individually measured with selective excitation of chlorophyll a serving as the primary electron acceptor. The two red-Bchls g exhibit almost the same polarization dependences. Based on the polarization dependence and structural data of the hRC, we propose a candidate molecule for red-Bchl g. The fluorescence spectra of single hRCs represent the spectral heterogeneity reflecting the local conformational inhomogeneity. A time series of the fluorescence spectra indicates occasional peak shifts between blue- and red-shifted states without significant changes in the fluorescence intensity. The spectral fluctuation is interpreted to be due to the local conformational dynamics around a Bchl g mediating the energy transfer, switching the terminal energy acceptor between two red-Bchls g. In conclusion, while the energy transfer network in the RC can be perturbed by microscopic dynamics, the total energy transfer efficiency, i.e., the light-harvesting function, is rather robust. The functional robustness may be due to multiple energy transfer pathways composed of many antenna pigments in the RC.

1.9 μm Few-Cycle Pulses Based on Multi-Thin-Plate Spectral Broadening and Nonlinear Self-Compression

In attosecond and strong-field physics, the acquisition of few-cycle laser sources open up a new area. We report a nonlinear pulse compression technology combining multi-thin-plate spectral broadening and nonlinear self-compression that generates a 0.52 mJ, good spatial quality characteristics and a spectral bandwidth supporting a 14 fs Fourier transform limited duration at 1 kHz repetition rate and at a center wavelength of 1.9 μm. The total energy transfer efficiency is up to 83%. Pulse to pulse stability of the energy output is 0.7% (RMS). The pulse duration is near 3 optical cycles. This pulse compression approach can be a key-enabling technology for the next generation of extreme photonics, attosecond research and coherent x ray-science, and it also can be further extended to mid-infrared lasers with longer wavelengths and higher peak power.

Numerical simulation of the energy transfer efficiency and rock damage in axial-torsional coupled percussive drilling

Axial-torsional coupled percussive drilling helps improve the breaking efficiency of hard rock. This paper adopted the simulation method to study the energy transfer efficiency (ETE), and rock damage in axial-torsional coupled percussive drilling with a multiple-button bit. The axial-torsional coupled percussive system model was first built in the finite element calculation platform. And then the temperature-dependent model parameter values for rock were selected. Finally, we simulated axial-torsional coupled percussive process, and analyzed the effects of various parameters. The main simulation results are as follows. In axial-torsional coupled percussive process, axial percussion has a significant influence on the ETE of torsional percussion, while torsional percussion has little influence on the ETE of axial percussion. As the impact velocity of axial percussive hammer increases, the ETE of axial percussion, the ETE of torsional percussion, and the total ETE all augment. When the impact velocity is increased from 4 m/s to 16 m/s, the total ETE is increased by 62.8%. Both the ETE of torsional percussion and the total ETE decline with the pulse torque amplitude increasing. When the pulse torque amplitude is increased from 4000 N m to 28000 N m, the total ETE is reduced by 18.3%. For convenience, we abbreviate the ratio of the torsional input energy to the total input energy as RTT. An increase in RTT, or an increase in rock temperature will reduce the ETE of axial percussion, the ETE of torsional percussion, and the total ETE. When the RTT is increased from 2.3% to 84.4%, the total ETE is reduced by 34.5%. As the axial impact velocity increases, the rock damaged areas gradually expand. With the increase of the pulse torque amplitude, the rock damaged areas sharply expand. As the RTT increases, the number of narrow tensile damaged zones extending outwardly decrease, while the connectivity between the tensile damaged areas caused by buttons augments. As the rock temperature rises, the total damaged area of rock gradually shrinks. This study provides a theoretical basis for the efficient rock breaking in axial-torsional coupled percussive drilling.

Switched-capacitor-convertors based on fractal design for output power management of triboelectric nanogenerator

Owing to the advantages of integration and being magnet-free and light-weight, the switched-capacitor-convertor plays an increasing role compared to traditional transformer in some specific power supply systems. However, the high output impedance and switching loss largely reduces its power efficiency, due to imperfect topology and transistors. Herein, we propose a fractal-design based switched-capacitor-convertors with characteristics including high conversion efficiency, minimum output impedance, and electrostatic voltage applicability. As a double-function output power management system for triboelectric nanogenerators, it delivers over 67 times charge boosting and 954 W m−2 power density in pulse mode, and achieves over 94% total energy transfer efficiency in constant mode. The establishment of the fractal-design switched-capacitor-convertors provides significant guidance for the development of power management toward multi-functional output for numerous applications. The successful demonstration in triboelectric nanogenerators also declares its great potential in electric vehicles, DC micro-grids etc.

Trap-Mediated Energy Transfer in Er-Doped Cesium Lead Halide Perovskite.

Substitutional doping lanthanide ions (Ln3+) in CsPbX3 has been proven to be an efficient strategy for expanding the properties of the perovskite (PVK). Here, erbium (Er3+) uniformly doped CsPbX3 perovskite microplates are grown through a chemical vapor deposition method. Two fluorescence peaks at 430 and 520 nm which respectively correspond to the PVK and Er3+ emissions are observed. The time-resolved photoluminescence of both PVK host and Er dopants demonstrates that trap states play a critical role in facilitating the energy transfer between the PVK host and the Er dopants, which is vital to sensitizing the Er3+. A photophysical model was put forward to comprehensively describe this trap-mediated energy-transfer process, and the dynamics processes are modeled using correlated rate equations. The rates of the carrier's relaxation and energy transfer are respectively obtained as 6.6 and 49 ns-1, and a total energy transfer efficiency was obtained as ∼32.6%.

Intermolecular distance measurement with TNT suppressor on the M13 bacteriophage-based F\xf6rster resonance energy transfer system

An M13 bacteriophage-based Förster resonance energy transfer (FRET) system is developed to estimate intermolecular distance at the nanoscale using a complex of CdSSe/ZnS nanocrystal quantum dots, genetically engineered M13 bacteriophages labeled with fluorescein isothiocyanate and trinitrotoluene (TNT) as an inhibitor. In the absence of trinitrotoluene, it is observed that a significant spectral shift from blue to green occur, which represents efficient energy transfer through dipole-dipole coupling between donor and acceptor, or FRET-on mode. On the other hand, in the presence of trinitrotoluene, the energy transfer is suppressed, since the donor-to-acceptor intermolecular distance is detuned by the specific capturing of TNT by the M13 bacteriophage, denoted as FRET-off mode. These noble features are confirmed by changes in the fluorescence intensity and the fluorescence decay curve. TNT addition to our system results in reducing the total energy transfer efficiency considerably from 16.1% to 7.6% compared to that in the non-TNT condition, while the exciton decay rate is significantly enhanced. In particular, we confirm that the energy transfer efficiency satisfies the original intermolecular distance dependence of FRET. The relative donor-to-acceptor distance is changed from 70.03 Å to 80.61 Å by inclusion of TNT.

Preliminary analysis of the Jimo coastal ecosystem with the ecopath model

The Jimo coast encompasses an area of 2157 km2, and the ecosystem is valuable both socially and economically with regional fisheries substantially contributing to the value. A mass-balanced trophic model consisting of 15 functional ecological groups was developed for the coastal ecosystem using the Ecopath model in Ecopath with Ecosim (EwE) software (version 6.4.3). The results of the model simulations indicated that the trophic levels of the functional groups varied between 1.0 and 3.76, and the total production of the system was estimated to be 5112.733 t km−2 yr−1 with a total energy transfer efficiency of 17.6%. The proportion of the total flow originating from detritus was estimated to be 48%, whereas that from primary producers was 52%, indicating that the grazing food chain dominated the energy flow. The ratio of total primary productivity to total respiration in the system was 3.78, and the connectivity index was 0.4. The fin cycling index and the mean path length of the energy flow were 4.92% and 2.57%, respectively, which indicated that the ecosystem exhibits relatively low maturity and stability. The mixed trophic impact (MTI) procedure suggested that the ecological groups at lower trophic levels dominated the feeding dynamics in the Jimo coastal ecosystem. Overfishing is thought to be the primary reason for the degeneration of the Jimo coastal ecosystem, resulting in a decline in the abundance of pelagic and demersal fish species and a subsequent shift to the predominance of lower-trophic-level functional groups. Finally, we offered some recommendations for improving current fishery management practices.

Effect of nano-clay platelet on fluorescence resonance energy transfer

This communication reports the phenomenon of fluorescence resonance energy transfer observed in between the binary solution of two laser dyes acriflavine (donor) and rhodamine B (acceptor), with and without nano-clay (laponite). It was observed that presence of clay particles increases the energy transfer efficiency. The effect of acceptor concentration on the total energy transfer efficiency has been studied to quantify the energy transfer, which may be used for photon emission and enhancement in lasing efficiency.

Coherent Energy Transfers between Orthogonal Radiant and Weakly Radiant Plasmonic Nanorod Resonators

The coherent couplings between plasmon modes have attracted significant research interest recently as they can dramatically modify the light–matter interactions and have many applications such as sensor and metamaterial. In this work, the energy transfer properties in a radiant and weakly radiant plasmon mode coupled system are investigated in the time domain. The phase difference between the two modes is found to vary from π to 0 with wavelength, and it is about π/2 near the resonance. The plasmon energy transfers back and forth between the two modes, and the transfer cycles increase with the coupling strength. Therefore, the system can undergo from enhanced absorption to Fano resonance phenomena on the optical spectra. Furthermore, the total energy transfer efficiency from the radiant plasmon mode to the weakly radiant one is also studied, and it shows a Förster resonance energy transfer (FRET)-like behavior.

Artificial Light-Harvesting Model in a Self-Assembly Composed of Cationic Dyes and Inorganic Nanosheet

This paper proposes an efficient artificial light-harvesting system in a host–guest assembly composed of functional dyes and inorganic nanosheet. Although we have already reported an efficient energy transfer between two types of porphyrin molecules on inorganic nanosheets (e.g., J. Am. Chem. Soc.2011, 133, 14280), the number of photons captured by one acceptor molecule (photon-harvesting efficiency: the donor/acceptor ratio when the total energy transfer efficiency is 50% as defined in the main text) was a few. To overcome this low photon-harvesting efficiency, we designed and investigated a new nanosheet type light-harvesting system including phthalocyanine. As a result from steady-state and time-resolved fluorescence measurements, the energy transfer reaction was highly efficient even under the donor excess conditions. The efficiency was almost 100% even under the ratio of donor/acceptor = 1/1–6/1. The most advanced point of this study is the presence of energy transfer between nonadjacent donor–accept...

Ultrafast Dynamics of Förster Resonance Energy Transfer and Photo-Induced Charge Transfer in Cationic Polyfluorene/Dye-Labeled DNA Complex

The ultrafast dynamics of Förster resonance energy transfer (FRET) and photo-induced charge transfer (PCT) has been investigated in an electrostatic complex of a fluorescein-labeled single-stranded DNA (as a FRET acceptor) and a cationic polyfluorene copolymer (as a FRET donor). The donor-acceptor intermolecular distance and total energy transfer efficiency are determined for a polymer/DNA complex with two different counter-ions and compared with those obtained using a theoretical model by considering the competition between FRET and PCT processes. The maximum total energy transfer efficiency (0.47) was estimated at the optimum donor-acceptor intermolecular distance of 39.6 A.

Preparation and characterization of bifunctional graphitized carbon-supported Pt composite electrode for unitized regenerative fuel cell

A bifunctional graphitized carbon-supported Pt oxygen electrode with montmorillonite-assisted dispersion was synthesized using an ultrasonic mixed technique process. By comparison, the graphitized carbon-supports obtain the optimal crystal quality with decreasing I D/ I G ratio from 1.43 to 0.81 and narrow the peak linewidth from 186 to 84 cm −1. Both Raman and the selected area diffraction analysis illustrate that the amorphous carbon tends to decrease via high-temperature graphite annealing so that the number of active C atoms will be reduced to improve oxidation resistance. From the CV measurements, the 20 wt.% Pt/graphite produces the highest specific charge transfer due to helpful montmorillonite assisted dispersion, whereas Pt size can only aggregate to grow bigger with an increase the Pt/graphite concentration. The polarization test of URFC presents the optimal performance in both the water electrolysis and fuel cell modes, with cell potentials of 1.6 V and 0.6 V at 100 mA cm −2, respectively; it exhibits an optimized energy conversion efficiency of 37.5%, which is better than a Pt/C electrocatalyst-coated membrane due to its having more mass transportation formation and corrosion suppression. By using generated hydrogen to produce electricity, the total energy transfer efficiency of the cell measurement system will reach 50.6%.

A 10 kW high-voltage pulse generator for corona plasma generation

In this article we discuss a 10 kW high-voltage pulse generator for producing corona-induced plasma. The generator mainly consists of a three-step resonant charging circuit switched by thyristors, a transmission line transformer, and a triggered spark-gap switch. Voltage pulses of 30–100 kV with a rise time of about 20 ns, a pulse duration of 50–250 ns, pulse repetition rate of 1–900 pulses per second, energy of up to 12 J/pulse, and an average power of up to 10 kW have been achieved with a total energy transfer efficiency of about 80%–90%. At each frequency, the deviation of the energy per pulse is around 1.0%. Moreover, the generator has been tested for more than 100 h for both industrial demonstrations and laboratory investigations at an average output power of 1–10 kW.

Femtosecond dynamics of carotenoid-to-bacteriochlorophyll a energy transfer in the light-harvesting antenna complexes from the purple bacterium Chromatium purpuratum

The energy transfer from the carotenoid okenone to bacteriochlorophyll a (Bchl a ) in the light harvesting complex B800–830 and chromatophores of Chromatium purpuratum was studied by steady-state fluorescence and fermtosecond transient absorption spectroscopy. By comparing the fluorescence excitation and the absorption spectra of the B800–830 antenna complex the total energy transfer efficiency of the okenone-to-Bchl a transfer was determined to 95 ± 5%. A fast (<200 fs) transfer from (at least) one carotenoid was observed to the B830 chlorophylls. This transfer was found by fs anisotropy measurements to be a transfer from the okenone S 2 state to the Bchl a Q x state, probably caused by the dipole-dipole (Förster) mechanism. Later the low-lying okenone S 1 state, which has a lifetime of ∼8ps in solution, was observed transferring energy to the B830 pool in ∼3.8 ps, while a second carotenoid transferred its energy also from the S 1 state to B800 in ∼0.5 ps. The results are discussed in relation to the crystal structure of the B800–850 complex of Rhodopseudomonas acidophila [McDermott et al. Nature 374 (1995)].

Energy transfer in water cluster scattering from solid surfaces

Classical trajectory calculations of (H2O)n (n ≤ 123)scattering from rigid model surfaces are presented. Three different intramolecular water potentials are employed together with both flat and corrugated surfaces. Clusters with an internal temperature of 180 K are scattered from the surface with incident velocities of 400–2000 m/s, and energy conversion during surface interaction is followed by probing the temperatures of various degrees of freedom. Molecular translation within the cluster couples strongly to the surface potential resulting in a compression phase of the cluster and a temperature peak at impact. Energy then dissipates to molecular rotation and further on to intramolecular vibration in the bending mode. The choice of the intramolecular potential has a strong effect only on the coupling to the stretch modes. Cluster fragmentation is very low up to 1300 m/s and thereafter increases with velocity. The energy redistribution at impact depends only weakly on cluster size and the surface potential employed. The total energy transfer efficiency is largely determined by the maximum surface potential energy during the scattering event.

Development of a 10-kW solid state pulse power supply for copper vapor lasers

We have developed a magnetic-pulse-compression-type 10-kW-class solid state pulse power supply for copper vapor lasers. By triggering the gates of two gate turn-off thyristors (GTOs) connected in parallel, a 5-μs rise time primary pulse was generated. A three-stage magnetic pulse compression circuit compressed the primary pulse to 0.13 μs. The 13.7-kW GTO switching energy was achieved with a 4-kHz pulse repetition rate when a dummy load was connected instead of copper vapor laser (CVL). Total energy transfer efficiency of the power supply was 60%. This pulse power supply has been applied to a CVL with a plasma tube of 70-mm inner diameter and 1.5-m discharge length, and has operated successfully.