Low Energy Transfer Efficiency Research Articles

Temperature-Dependent Characterization of Long-Range Conduction in Conductive Protein Fibers of Cable Bacteria.

Multicellular cable bacteria display an exceptional form of biological conduction, channeling electric currents across centimeter distances through a regular network of protein fibers embedded in the cell envelope. The fiber conductivity is among the highest recorded for biomaterials, but the underlying mechanism of electron transport remains elusive. Here, we performed detailed characterization of the conductance from room temperature down to liquid helium temperature to attain insight into the mechanism of long-range conduction. A consistent behavior is seen within and across individual filaments. The conductance near room temperature reveals thermally activated behavior, yet with a low activation energy. At cryogenic temperatures, the conductance at moderate electric fields becomes virtually independent of temperature, suggesting that quantum vibrations couple to the charge transport through nuclear tunneling. Our data support an incoherent multistep hopping model within parallel conduction channels with a low activation energy and high transfer efficiency between hopping sites. This model explains the capacity of cable bacteria to transport electrons across centimeter-scale distances, thus illustrating how electric currents can be guided through extremely long supramolecular protein structures.

Time, temperature and concentration resolved Yb3+ luminescence study in co-sputtered Cu2-xGaxS2 (0.1 < x < 1.6) thin films with a Cu–Ga composition gradient

The broad class of Cu(Al,Ga,In) (S,Se,Te)2 solar absorber materials when doped with Yb3+ are interesting for thin film based luminescent solar concentrator (LSC's) application. In this work the strong and broad absorption properties of co-sputtered CuGaS2 (CGS) thin films combined with the luminescent properties of Yb are reported. Energy-dispersive x-ray spectroscopy (EDS), x-ray diffraction, transmission, excitation, and temperature dependent emission as well as radiative lifetime measurements are performed on thin films with varying Cu:Ga ratios and Yb3+ concentrations. It is found that Yb3+ emission can be broadly sensitized by the host in the range of 200–600 nm. A lower Cu:Ga ratio, crystallinity and post annealing in air provides a positive impact on the sensitization of Yb3+ emission. The temperature dependent time integrated decay curves show a clear thermal energy barrier of about 0.2 eV. Because the exponential tail, with a lifetime of 110 μs, is constant with temperature, we conclude that the barrier is connected to the thermal release of electrons trapped at the Yb2+ ground state. The low energy transfer efficiency from the host to the Yb dopant is attributed to efficient non-radiative electron-hole pair recombination. The prospects and design criteria of Cu(Al,Ga,In) (S,Se,Te)2 solar absorber materials for LSC applications is the further subject of the discussion.

Influence of metal encapsulation on thermophysical properties and heat transfer in salt hydrate phase change material for air conditioning system

Phase change materials (PCM) are gaining increasing attention as a cold energy storage technology for air conditioning systems due to their potential to reduce electrical grid loading, energy consumption, and electricity costs. However, realizing the full potential of PCM-based cold energy storage in practical applications is constrained by low cold energy transfer efficiency within air conditioning systems. This study addresses this challenge by exploring the encapsulation of salt hydrate PCM using six different metals to enhance heat transfer efficiency. Additionally, the corrosion behaviors of the PCM towards these metals were thoroughly evaluated. Notably, copper demonstrated the highest corrosion rate, and the resulting corrosion products, particularly from copper and brass, were found to substantially reduce the energy storage capacity of PCM. Moreover, PCM encapsulated into aluminum alloy exhibited higher heat transfer efficiency than that of stainless steel. In light of these findings, aluminum alloy is recommended as the optimal choice for PCM encapsulation, given its corrosion resistance and minimal effect on thermal properties. This research provides crucial insights for selecting appropriate metals to enhance the efficiency and durability of air conditioning systems utilizing salt hydrate PCM.

Boosting characteristic emissions of lanthanide in Cs2Ag0.6Na0.4InCl6–xBrx double perovskites via mixing halide

Lanthanide ions (Ln3+) doping provides a potential strategy to control over the luminescent properties of lead-free halide double perovskite nanocrystals (DP NCs). However, due to the low energy transfer efficiency between self-trapped exciton (STE) and Ln3+ ions, the characteristic emissions of Ln3+ ions are not prominent. Furthermore, the energy transfer mechanism between STE and Ln3+ ions is also elusive and requires in-depth study. We chose trace Bi3+-doped Cs2Ag0.6Na0.4InCl6–xBrx as a representative DP matrix to demonstrate that by tuning the bromide concentration, the Ln3+ emission can be greatly enhanced. Such enhanced STE and Ln3+ ions energy transfer originates from the high covalency of Ln–Br bond, which contributes to improvement of the characteristic emission of Ln3+ ions. Furthermore, optical spectroscopy reveals that the energy transfer mechanism from DP to Eu3+ ions is different from all the other doped Ln3+ ions. The energy transfer from DP to Eu3+ ions is mostly through Eu–Br charge transfer while the other Ln3+ ions are excited by energy transfer from STE. The distinct energy transfer mechanism has resulted from the energy separation between the excited energy level of Ln3+ ions and the bottom of conduction band of DP. With increasing the energy separation, the energy transfer from STE to Ln3+ ions is less efficient because of the generation of a larger number of phonons and finally becomes impossible for Eu3+ ions. Our results provide new insight into tuning the energy transfer of Ln3+-doped DP NCs.

Magnetic-responsive upconversion luminescence resonance energy transfer (LRET) biosensor for ultrasensitive detection of SARS-CoV-2 spike protein

Upconversion nanoparticles (UCNPs) are ideal donors for luminescence resonance energy transfer (LRET)-based biosensors due to their excellent upconversion luminescence properties. However, the relatively large size of antibodies and proteins limits the application of UCNPs-based LRET biosensors in protein detection because the large steric hindrance of proteins leads to low energy transfer efficiency between UCNPs and receptors. Herein, we developed a magnetic responsive UCNPs-based LRET biosensor to control the coupling distance between antibody-functionalized UCNPs (Ab-UCNPs) as donors and antibody-PEG linker-magnetic gold nanoparticles (Ab-PEG-MGNs) as acceptors for ultrasensitive and highly selective detection of SARS-CoV-2 spike proteins. Our results showed that this platform reversibly shortened the coupling distance between UCNPs and MGNs and enhanced the LRET signal with a 10-fold increase in the limit of detection (LOD) from 20.6 pg/mL without magnetic modulation to 2.1 pg/mL with magnetic modulation within 1 h. The finite-difference time-domain (FDTD) simulation with cyclic distance change confirmed the distance-dependent LRET efficiency under magnetic modulation, which supported the experimental results. Moreover, the applications of this magnetic-responsive UCNP-based LRET biosensor could be extended to other large-size biomolecule detection.

Comprehensive Crystal Regulation Reduces Interfacial Energy Loss for Efficient Blue Perovskite Light-Emitting Diodes.

As an essential component of future full-color displays, blue perovskite light-emitting diodes (PeLEDs) still lag far behind the red and green counterparts in the device performances. In the mainstream quasi-2D blue perovskite system, trap-mediated nonradiative loss, low energy transfer efficiency, and interface fluorescence quenching remain significant challenges. Herein, guanidinium thiocyanate (GASCN) and potassium cinnamate (PCA) are respectively introduced into the hole transport layer (HTL) and the perovskite precursor to achieve a dense and uniform perovskite thin film with greatly improved optoelectronic properties. Therefore, adequate GA+ acts as pre-nucleation sites on the HTL surface, regulating crystallization through strong hydrogen bonding with perovskite intermediates. The realized polydisperse domain distribution is conducive to cascade energy transfer, and the improved hole transport ability alleviates interface fluorescence quenching. In addition, the SCN- and CA- groups can form coordination bonds with the defects at the buried perovskite interface and grain boundaries, respectively, which effectively suppresses the detrimental nonradiative recombination. Benefitting from the comprehensive crystal regulation, blue PeLEDs featuring stable emission at 484 and 468nm exhibit improved external quantum efficiencies of 11.5% and 4.3%, respectively.

Effects of non-electrical parameters on the characteristics of discharge craters and machining performance in short electrical arc milling

During electrical discharge machining (EDM), the process parameters greatly influence the discharge characteristics and machining performance, including electrical and non-electrical parameters. As a new EDM method, short electrical arc milling (SEAM) is plagued by frequent short circuits, poor debris removal, and low energy-transfer efficiency. Therefore, this paper investigated the influence of non-electrical parameters (electrode material, working medium, and electrode rotation) on the crater characteristics, machining efficiency, and electrode wear. The micromorphological characteristics of the workpiece were explored. The results suggested that non-electrical parameters compressed and fractured the plasma channels, thus changing the effect of EDM. The air-tap water medium and electrode rotation promoted debris removal and arc breaking, which prevented the arc from ablating the workpiece. When GH4099 alloy was machined with a copper electrode, the workpiece surface quality and machining efficiency were high, and the thickness of the heat-affected zone was small. This work reveals the characteristics of short electric arc discharge and provided a theoretical basis for the efficient and high-quality machining of difficult-to-cut materials by SEAM.

Energy-efficient scheduling for active RIS-assisted self-sustainable wireless powered IoT networks in smart societies

Integrating wireless powered communication networks (WPCNs) into low-power internet of things (IoT) is a promising technique to achieve sustainable cities and society. However, the main design challenge for WPCNs is the low efficiency of wireless energy transfer. To address this challenge, this paper investigates active reconfigurable intelligent surface (RIS)-assisted WPCNs, where the reflecting beamforming gain of active RIS can be utilized to enhance wireless energy and information transmissions. We formulate an energy efficiency maximization problem that jointly optimizes time-slot allocation, transmit power control, and reflection parameters of RIS. Due to the highly coupled variables and fractional structure of the energy efficiency expression, we develop an alternating optimization method to solve it through utilizing the Dinkelbach-type method and block coordinate descent algorithm. Simulation results demonstrate the significant performance gain achieved by the proposed method for active RIS-assisted WPCNs, as compared to the passive RIS-assisted method and the counterpart without the aid of RIS.

All‐Dielectric Insulated 3D Plasmonic Nanoparticles for Enhanced Self‐Floating Solar Evaporation under One Sun

AbstractPlasmonic absorbers, featured by unique capability of broadband light absorption and nanoscale optical concentration, have long been regarded as ideal candidates for self‐floating interfacial solar evaporation yet suffering from low energy transfer efficiency because of poor thermal localization. In this work, by implanting an ion beam exfoliation of the continuous metallic film from the gold/nanoporous alumina template (Au/NPT), the all‐dielectric insulated plasmonic absorbers are demonstrated as efficient self‐floating interfacial solar evaporators with measured efficiency of ≈80% under one sun, which shows a ≈20% increment to conventional Au/NPT and is comparable to mainstream complicated carbon‐based evaporators with external thermal insulators. The enhanced energy transfer process can be ascribed to synergistic effect of plasmon‐enhanced solar absorption, broadband light induced thermal localization and/or insulation, as well as efficient mass transport channels. The results here would provide a new insight in underlying understanding and inspire further development of plasmonic solar thermal conversion.

Broadband high-gain Tm3+/Ho3+ co-doped germanate glass multimaterial fiber for fiber lasers above 2 µm.

High-gain Tm3+/Ho3+ co-doped optical fibers are urgently desired for high-repetition-rate mode-locked fiber lasers at >2 µm. Here, Tm3+/Ho3+ co-doped germanate glass with low hydroxyl (OH-) content was prepared by the conventional melt-quenching method combined with the reaction atmosphere procedure (RAP) dehydration technique. The doping concentrations of Tm2O3 and Ho2O3 are 2.5 mol.% (7.1 wt.%) and 0.25 mol.% (0.7 wt.%), respectively. Thanks to the high Tm3+ doping (7.1 wt.%) and low energy transfer efficiency (19.8%) between Tm3+ and Ho3+ ions, it enables achieving broadband and high-gain performance in the 2 µm region. Then a silicate-clad Tm3+/Ho3+ co-doped germanate core multimaterial fiber was successfully drawn by using the rod-in-tube method, which has a broadband amplified spontaneous emission (ASE) with a full width at half-maximum (FWHM) of 247.8 nm at 2 µm. What is more, this new fiber has a high gain per unit length of 4.52 dB/cm at 1.95 µm. Finally, an all-fiber-integrated passively mode-locked fiber laser was built by using this broadband high-gain fiber. The mode-locked pulses operate at 2068.05 nm, and the fundamental repetition rate is up to 4.329 GHz. To the best of our knowledge, this is the highest fundamental repetition rate for the all-fiber passively mode-locked fiber laser above 2 µm. These results suggest that the as-drawn multimaterial fibers with broadband high-gain characteristics are promising for high-repetition-rate ultrafast fiber lasers.

Near-Field Wireless Power Transfer for 6G Internet of Everything Mobile Networks: Opportunities and Challenges

Radiating wireless power transfer (WPT) brings forth the possibility to cost-efficiently charge wireless devices without requiring a wiring infrastructure. As such, it is expected to play a key role in the deployment of limited-battery communicating devices, as part of the 6G-enabled Internet of Everything (IoE) vision. To date, radiating WPT technologies are mainly studied and designed assuming that the devices are located in the far-field region of the power radiating antenna, resulting in relatively low energy transfer efficiency. However, with the transition of 6G systems to mmWave frequencies combined with the use of large-scale antennas, future WPT devices are likely to operate in the radiating near-field (Fresnel) region. In this article, we provide an overview of the opportunities and challenges that arise from radiating near-field WPT. In particular, we discuss the possibility to realize beam focusing in near-field radiating conditions, and highlight its possible implications for WPT in future IoE networks. Furthermore, we overview some of the design challenges and research directions that arise from this emerging paradigm, including its simultaneous operation with wireless communications, radiating waveform considerations, hardware aspects, and operation with typical antenna architectures.

Simultaneous pulsed interleaved excitation (PIE) and alternating-laser excitation (ALEX): an optimized excitation pattern for single molecule FRET

Pulsed Interleaved Excitation (PIE) is a well-known technique for synchronizing and/or delaying pulsed lasers to alternately excite donor- and acceptor-labeled species within single-molecule FRET (smFRET) studies. Laser pulses are separated on a nanosecond (ns) time scale to allow for the simultaneous recording of the temporal behavior of the two species that are excited by the corresponding laser. This allows to differentiate between a FRET pair - even with very low energy transfer efficiency - from a molecule with either absent or non-fluorescing acceptor.

A self-trigger three-electrode plasma synthetic jet actuator

As a potential active flow control technology, plasma synthetic jet actuator (PSJA) has shown wide and promising application prospects in the high-speed flow. However, the application of PSJA is still limited by the low energy transfer efficiency and high driving voltage. This study presents a novel and practical self-trigger three-electrode plasma synthetic jet actuator (STPSJA), which is able to prolong the electrode distance with low breakdown voltage. A plasma jet is introduced to replace the high-voltage pulse of conventional three-electrode PSJA. The working process of STPSJA is investigated based on discharge waveforms, high-speed photography, and high-speed schlieren image system. Compared with the two-electrode actuator, the maximum precursor shock velocity can be increased from 449 m/s to 605 m/s. Furthermore, the discharge efficiency of STPSJA can be 68% when the electrode distance exceeds 10 mm and the breakdown voltage is only about 318 V. This study presents a promising step toward optimizing the design of plasma synthetic jet actuator.

Temperature-dependent color-tunable luminescence in CsPbBr3: Dy3+ glass ceramic

Available tunability of energy up-conversion in rare-earth (RE) ion doped nanomaterials has drawn great attention recently in the field of high-sensitive optical temperature transducer, but the intrinsically sharp fluorescence thermal-quenching and low energy transfer efficiency certainly limit further development. In this work, CsPbBr3 perovskite quantum dots (PQDs) was prepared by the melt-quenching method, simultaneously doping with Dy3+ in borosilicate glass, aiming to explore the thermochromic property. The novel phenomenon herein is that emerged bimodal emissions come from a luminescent active center of CsPbBr3 and a temperature-passivated RE Dy3+ ion, synergistically contributed to the remarkable relative sensitivities (2.631% K − 1). Interestingly, temperature-depended polychromatic luminescence among the PQDs embedded glass has been fully demonstrated as pumped by 365 nm ultraviolet light. Precise control of luminescent centers and color gamut is expected to design a temperature-sensitive material based on PQDs for promising optical applications.

Antiangiogenesis Combined with Inhibition of the Hypoxia Pathway Facilitates Low-Dose, X-ray-Induced Photodynamic Therapy.

X-ray-induced photodynamic therapy (XPDT) is overwhelmingly superior in treating deep-seated cancers. However, limitations remain, owing to a combination of the poor scintillation performance of the nanoscintillator, low energy transfer efficiency of the therapeutic nanoplatform, and hypoxic environment presented in the tumor tissue. Collectively, these reduce the curative effect of XPDT. Here, we report a highly efficient, low-dose XPDT realized by systematic optimization from scintillation efficiency, nanoplatform structure, to therapeutic approach. We developed a biocompatible, codoped CaF2 nanoscintillator that emitted sufficiently green radioluminescence that was bright enough to be seen by the naked eye. Using dendrimers as a framework, we built a nanoplatform featuring a dual-core-satellite architecture, which enabled both procedurally and spatially separate dual-loading of therapeutic agents. This strategy allowed for the fabrication of a combined XPDT and antiangiogenic therapy, resulting in a therapeutic system capable of simultaneous tumor attacks. After exposure to ultralow dose radiation, XPDT resulted in marked tumor reduction while the antiangiogenic drug effectively blocked tumor vascularization exacerbated by XPDT-mediated hypoxia, rendering a pronounced synergy effect. This system also showed high biosafety, as the agents adopted had been used clinically and both Ca and F elements were widespread in the human body. Taken together, the findings presented here provided a reference for the construction of complex, multiloading architecture in coordination with structural complexity and functional diversification. This work provided a safer and more robust application of the combined XPDT and antiangiogenesis in future clinical treatment settings.

Increasing Power Supply Efficiency for “Two Wire-Rail” Line Consumers

The article is devoted to the problem of non-traction consumers power supply of AC railways. The low efficiency of energy transfer is caused by the design of a non-traction power supply line. The absence of bilateral power is typical for non-traction network 27,5 kV which consist of “two wire-rail” lines. This line is outdated technology, which does not correspond to modern requirements on the power quality, but used on AC railways with three-phase traction transformers. The purpose of the article is to investigate the methods of power supply improvements for non-traction consumers in terms of voltage unbalance, harmonic distortions and energy losses. Connection of the phasing device to delta winding traction transformer for bilateral supplying non-traction customers from network 27,5 kV is suggested in the article. The implementation of a method to increase the efficiency of electricity transmission in the non-traction network power supply allows to reduce power losses from 720 MWh / year to 441 MWh / year, the voltage unbalance from 1,9% to 1,3% and the total harmonic distortion from 8 % to 6 % respectively. Additionally, investment attractiveness of the decision was evaluated. Keywords: non-traction customers, two wire-rail line, phase coordinates, AC railway, power quality

Analysis and Experiment on Performance Improvement of IPPS at Low Temperature

The performance of inductive pulsed power supplies (IPPSs) is limited by excessive joule heat loss and low energy transfer efficiency. A significant reduction in the coil resistance can fundamentally ameliorate this problem. This article takes the meat grinder with self-charge capacitor and thyristor (SECT) circuit as an example to study the performance improvement caused by the reduction of the coil resistance. The influence of coil resistance on several performance indexes is analyzed by circuit analysis and simulation. Then, the experiment with an energy level of 40 kJ is carried out, in which the inductors have very low resistance due to immersion in liquid nitrogen. With low temperature, the charging energy and the output current peak value are increased by 37% and 19%, respectively, the pulsewidth of output current is increased by 257%, and the energy transfer capacitor is successfully self-charged compared to the performance of the same SECT circuit with room temperature. Thus, the feasibility of applying nitrogen cooling to IPPS is validated.

New Sm-PMN-PT Ceramic-Based 2-D Array for Low-Intensity Ultrasound Therapy Application.

A two-dimensional (2-D) array with a small pitch (approximately 0.5λ in medium) can achieve complete 3-D control of ultrasound beams without grating lobes and enable the generation of multiple focal spots simultaneously, which is a desired tool for noninvasive therapy. However, the large electrical impedance of 2-D array elements owing to their small size results in a low energy transfer efficiency between a 2-D array and an electrical system, thereby limiting their practical applications. This article presents the development of a 1-MHz 256-element 2-D array ultrasonic transducer of low electrical impedance based on a new Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Sm-PMN-PT) piezoceramic with ultrahigh dielectric permittivity. The electrical impedance of the array element is decreased by 3.4 times as the Sm-PMN-PT replacing commercial PZT-5H. Consequently, the output acoustic pressure of the 2-D array made of Sm-PMN-PT ceramic is approximately twice that of the 2-D array made of PZT-5H ceramic under the same excitation conditions. Array elements are spaced at a 1.1-mm pitch ( 0.71λ in water), enabling a large steering range of the ultrasound beam. A multiple-target blood-brain barrier opening in vivo is demonstrated using the proposed 2-D array with electronic focusing and steering. The obtained results indicate that the 2-D array made of Sm-PMN-PT ceramic is promising for practical use in low-intensity ultrasound therapy applications.

Engineering the photoactive orange carotenoid protein with redox-controllable structural dynamics and photoprotective function

Photosynthesis requires various photoprotective mechanisms for survival of organisms in high light. In cyanobacteria exposed to high light, the Orange Carotenoid Protein (OCP) is reversibly photoswitched from the orange (OCPO) to the red (OCPR) form, the latter binds to the antenna (phycobilisomes, PBs) and quenches its overexcitation. OCPR accumulation implicates restructuring of a compact dark-adapted OCPO state including detachment of the N-terminal extension (NTE) and separation of protein domains, which is reversed by interaction with the Fluorescence Recovery Protein (FRP). OCP phototransformation supposedly occurs via an intermediate characterized by an OCPR-like absorption spectrum and an OCPO-like protein structure, but the hierarchy of steps remains debatable. Here, we devise and analyze an OCP variant with the NTE trapped on the C-terminal domain (CTD) via an engineered disulfide bridge (OCPCC). NTE trapping preserves OCP photocycling within the compact protein structure but precludes functional interaction with PBs and especially FRP, which is completely restored upon reduction of the disulfide bridge. Non-interacting with the dark-adapted oxidized OCPCC, FRP binds reduced OCPCC nearly as efficiently as OCPO devoid of the NTE, suggesting that the low-affinity FRP binding to OCPO is realized via NTE displacement. The low efficiency of excitation energy transfer in complexes between PBs and oxidized OCPCC indicates that OCPCC binds to PBs in an orientation suboptimal for quenching PBs fluorescence. Our approach supports the presence of the OCPR-like intermediate in the OCP photocycle and shows effective uncoupling of spectral changes from functional OCP photoactivation, enabling redox control of its structural dynamics and function.

Design and control of bidirectional active balancing model for lithium-ion battery pack

The performance of battery cells and serial/parallel pack will be inconsistent, because of the deviation of production process and the different application environment. The overall capacity of lithium-ion battery pack will easily decline. In our study, an efficient bidirectional balancing method based on least squares algorithm and optimal control strategy is proposed. The bidirectional DC/DC converter is designed to transfer the energy between one cell and the adjacent cell. The predictive control (PC) algorithm based on cell state of charge (SOC) value is established. The experimental results indicate that bidirectional active balancing model can effectively reduce the voltage difference between battery cells. The optimal control strategy can overcome the shortcomings of traditional strategy such as low energy transfer efficiency, long equalisation time and unsuitable for large capacity. Besides, it can avoid unnecessary energy loss and reduce the balancing time by 28%.