Large Energy Loss Research Articles

Research on optimal control strategy of wind–solar​ hybrid system based on power prediction

In wind and solar power generation systems, the MPPT algorithm is often used to quantify renewable energy production power, if the light or wind changes suddenly in the algorithm search process, it is possible that the iterative algorithm will not be able to track to the maximum power point or fall into turbulence, and frequent restart of the relevant algorithm will also bring a large energy loss. In view of this situation. For the purpose of further analysis the effect of power output characteristics on the tracking ability of the system, and to enhance the reliability and energy utilization of renewable energy generation system. This manuscript studies an optimal control method for a wind–solar storage complement device designed using power prediction. The article establishes the simulation model of each subsystem separately, and the wavelet packet neural network is used to build a power prediction model. An MPPT optimal control strategy is proposed. This control strategy combines the hysteresis loop comparison-based P&O algorithm in single-peak MPPT and the improved firefly algorithm in multi peak MPPT. The dynamic tracking ability, speed and single peak value and multi peak optimization capability of the algorithm are guaranteed. And the simulation analysis of the control strategy is executed by MATLAB, and the findings demonstrate the efficacy of the optimum control technique proposed in this article. This algorithm has also been shown to outperform traditional intelligent algorithms in terms of tracking efficiency and stability

The Discovery of a Low-energy Excess in Cosmic-Ray Iron: Evidence of the Past Supernova Activity in the Local Bubble.

Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species ( , e ±, and nuclei, 1H-8O, 10Ne, 12Mg, 14Si) which resulted in a number of breakthroughs. One of the latest long-awaited surprises is the spectrum of 26Fe just published by AMS-02. Because of the large fragmentation cross section and large ionization energy losses, most of CR iron at low energies is local and may harbor some features associated with relatively recent supernova (SN) activity in the solar neighborhood. Our analysis of the new AMS-02 results, together with Voyager 1 and ACE-CRIS data, reveals an unexpected bump in the iron spectrum and in the Fe/He, Fe/O, and Fe/Si ratios at 1-2 GV, while a similar feature in the spectra of He, O, and Si and in their ratios is absent, hinting at a local source of low-energy CRs. The found excess extends the recent discoveries of radioactive 60Fe deposits in terrestrial and lunar samples and in CRs. We provide an updated local interstellar spectrum (LIS) of iron in the energy range from 1 MeV nucleon-1 to ~10 TeV nucleon-1. Our calculations employ the GALPROP-HELMOD framework, which has proved to be a reliable tool in deriving the LIS of CR , e -, and nuclei Z ⩽ 28.

Numerical simulation and performance evaluation of cyclone separator with built‐in material for sand removal in gas well

AbstractThe natural gas produced from gas wells contains a lot of fine gravel impurities, which causes the blockage of precision pressure regulating equipment and metering equipment. Cyclone separator is widely used in the field of natural gas surface sand removal because of its simple structure and high separation efficiency. In the field application of traditional cyclone separators, there are some problems, such as ineffective separation of fine sand particles in natural gas, low separation efficiency, and large energy loss. In order to solve the above problems, a new cyclone separator is designed in this paper; that is, a cone built‐in object is arranged inside the traditional separator to improve the separation efficiency and reduce the pressure drop. First, the feasibility of the scheme is verified by comparing the computational fluid dynamics (CFD) simulation results of the traditional separator with the experimental results. Second, the performance indexes of the new separator and the traditional separator under specific working conditions are simulated and compared. The conclusions are as follows: compared with the traditional separator, the new separator can improve the tangential velocity of the outer cyclone. It has obvious separation effect on small particles, and the separation particle size ratio can be reduced by 47.83%. The pressure drop of the separator is reduced by 11.42%. While the separation efficiency and precision are improved, the overall performance of the separator is also improved and the energy consumption is reduced.

In‐Situ Hot Oxygen Cleansing and Passivation for All‐Inorganic Perovskite Solar Cells Deposited in Ambient to Breakthrough 19% Efficiency

AbstractAll‐inorganic perovskite CsPbI3 has attracted extensive attention recently because of its excellent thermal and chemical stability. However, its photovoltaic performance is hindered by large energy losses (Eloss) due to the presence of point defects. In addition, hydroiodic acid (HI) is currently employed as a hydrolysis‐derived precursor of intermediate compounds, which often leads to a small amount of organic residue, thus undermining its chemical stability. Herein, an in‐situ hot oxygen cleansing with superior passivation (HOCP) for the triple halide‐mixed CsPb(I2.85Br0.149Cl0.001) perovskite solar cells (abbreviated as CsPbTh3) deposited in an ambient atmosphere to reduce the Eloss to as low as 0.48 eV for the power conversion efficiency (PCE) to reach 19.65% is demonstrated. It is found that the hot oxygen treatment effectively removes the organic residues. Meanwhile, it passivates halide vacancies, hence reduces the trap states and nonradiative recombination losses within the perovskite layer. As a result, the PCE is increased significantly from 17.15% to 19.65% under 1 sun illumination with an open‐circuit voltage enlarged to 1.23 from 1.14 V, which corresponds to an Eloss reduction from 0.57 to 0.48 eV. Also, the HOCP‐treated devices exhibit better long‐term stability. This insight should pave a way for decreasing nonradiative charge recombination losses for high‐performance inorganic perovskite photoelectronics.

Morphological, mechanical, and electromagnetic interference shielding effectiveness characteristics of glass fiber/epoxy resin/MWCNT buckypaper composites

AbstractGlass fiber/epoxy resin composites (GF/EP) using one and three multi‐walled carbon nanotube buckypapers (BP) were obtained and their complex parameters, reflectivity, and electromagnetic interference (EMI) shielding effectiveness (SE) at X‐band (8.2–12.4 GHz) and Ku‐band (12.4–18 GHz) were evaluated. The preparation of BP used polyacrylonitrile (PAN) nanofibers (PF These composites show both large storage and energy loss capacity in both bands revealing promising results related to EMI SE applications. Besides, a high attenuation of around 67% and 72% were achieved for BP based composites. The cross‐section view of the buckypaper and the laminates was analyzed by scanning electron microscopy (SEM). The incorporation of the CNT film into the laminates showed no improvements in the elastic properties through dynamic mechanical analyses (DMA). Nevertheless, a decrease in the shear properties by the compression shear test (CST) and interlaminar shear strength (ILSS) has been observed. GF/EP/BP/PF composite presented a reduction of 29 and 39% in its ILSS properties compared to the base laminate (GF/EP). Also, the decrease was even more significant, revealing a steep reduction in its CST properties. On the other hand, the removal of the pan nanofiber (PF) led to better mechanical properties for GF/EP/BP/RPF composites. Results have shown ILSS values of 47.4 ± 2.2 MPa which are close to the base laminate (52.4 ± 3.1 MPa). The removal of the PF provided larger porous in the CNT network, making the impregnation by epoxy easier in the BP/RPF which resulted in improved shear properties compared to GF/EP/BP/PF samples.

High Efficiency (15.8%) All-Polymer Solar Cells Enabled by a Regioregular Narrow Bandgap Polymer Acceptor.

Despite the significant progresses made in all-polymer solar cells (all-PSCs) recently, the relatively low short-circuit current density (Jsc) and large energy loss are still quite difficult to overcome for further development. To address these challenges, we developed a new class of narrow-bandgap polymer acceptors incorporating a benzotriazole (BTz)-core fused-ring segment, named the PZT series. Compared to the commonly used benzothiadiazole (BT)-containing polymer PYT, the less electron-deficient BTz renders PZT derivatives with significantly red-shifted optical absorption and up-shifted energy levels, leading to simultaneously improved Jsc and open-circuit voltage in the resultant all-PSCs. More importantly, a regioregular PZT (PZT-γ) has been developed to achieve higher regiospecificity for avoiding the formation of isomers during polymerization. Benefiting from the more extended absorption, better backbone ordering, and more optimal blend morphology with donor component, PZT-γ-based all-PSCs exhibit a record-high power conversion efficiency of 15.8% with a greatly enhanced Jsc of 24.7 mA/cm2 and a low energy loss of 0.51 eV.

On the stability and stationarity of the Super H-mode combined with an ion transport barrier in the core

The Super H-mode, a regime with high pedestal pressure and stored energy, is explored on DIII-D and combined with an ion transport barrier in the plasma core to increase performance. A significant improvement of ion temperatures and confinement is facilitated by favorable conditions such as high rotational shear and high ion pedestal temperatures. As a result of a rise in density and simultaneous decrease in rotation, the ion transport barrier disappears during the discharge evolution, leading to a transition from a very high confinement state at early times, to a reduced but still high confinement phase. Additionally, in many discharges, a global magnetohydrodynamic (MHD) event consistent with the coupling of a destabilized internal mode to an edge localized mode causes a large energy loss and leads to a reorganization of the plasma into a lower temperature, higher density state. Depending on the magnitude of the global MHD event, the plasma edge collisionality can increase significantly and shift the operational boundary from the peeling to the ballooning side, which can be understood as a drop out of the Super H-mode channel into standard H-mode. Hence, in Super H-mode discharges with ion transport barriers, both the improved pedestal height and rotational shear contribute to the high stored energy. At very low levels of rotation, the confinement factor for SH modes is still expected to exceed standard H-mode by 20%–30%. With their overall stationarity and high-performance levels, Super H-mode discharges provide an attractive regime for ITER and may enable a more compact design of future fusion power plants.

Effect of the flow upstream the impeller inlet on flow instability of a centrifugal pump

Under part-load conditions, flow instability phenomena in a hydraulic machinery could lead to strong pressure fluctuations and vibrations, posing a great threat to the safety of the units. This paper analysed unsteady flow in a centrifugal pump (specific speed of 39 min−1·m3s− 1·m) with different inlet geometries under part-load conditions. An advanced turbulence model, PANS (partially averaged Navier-Stokes), acting as a bridge from RANS to DNS, is applied for numerical simulations. The results indicated the pump with a straight inlet pipe reached higher values of pump head and efficiency near the design point than the test pump with a non-straight inlet pipe. According to the characteristic curves, hump phenomenon was observed at 0.75ϕbep for the pump having a straight inlet pipe, while it occurred at 0.5ϕbep for the test pump. Under the condition of a low flow rate i.e. ϕ=0.5ϕbep, there is strong pre-swirling flow upstream impeller inlet for the test pump, which contributes to the propagation of rotating stall cells; But energy loss in the impeller inlet of the pump with straight inlet pipe is slightly higher than that in the test pump due to the presence of the stationary stall cells, which causes large energy loss in the impeller and the passage upstream impeller inlet. Further, rotating stall cells are captured in the impeller in both pumps under the condition of ϕ=0.75ϕbep.

SWIPT-Enabled D2D Communication Underlaying NOMA-Based Cellular Networks in Imperfect CSI

Device-to-Device (D2D) communication is an emerging paradigm which enhances the coverage, capacity, and spectral efficiency of the network using cooperative communication in an underlay of cellular networks. In spite of these advantages, it suffers from large bandwidth and energy loss due to usage of half-duplex relaying and limited energy storage devices. To solve these issues, we integrate the full-duplex (FD) relaying and time splitting simultaneous wireless information and power transfer (SWIPT) technique at the D2D transmitters (DDTs). Moreover, to support the ubiquitous connectivity and reduce the latency, non-orthogonal multiple access is used at the base station. The SWIPT-FD-based DDTs and SWIPT-based cell user equipment (CUE) harvest the energy from the base station, after that the DDTs and CUEs decode the desired signal from the multiplexed signal using successive interference cancellation technique, and forward the desired signal to the D2D user equipment (DUE) to improve their QoS. In this paper, ergodic capacity at the DDTs and DUEs & closed-form expressions of the outage probabilities are derived with imperfect CSI. The results demonstrate that the proposed scheme achieves better performance as compared to that of the existing SWIPT-FD-OMA based scheme.

Effect of External Magnetic Field on Long DC Arc Characteristics with Rng-shaped Anode

Fluctuation phenomena of plasma jet flow in an innovative long DC arc system with a ring-shaped anode were successfully clarified by a high-speed camera visualization. The long DC arc with long electrode gap distance more than 350 mm has been applied to gas decomposition due to its advantages of long plasma length, resulting in long residence time of treated gas. However, large heat loss at a conventional hemispherical-shaped anode was a critical issue in the long DC arc system. Therefore, the ring-shaped anode was utilized to convert large energy loss at the anode into the plasma jet flow. High-speed camera observation revealed the effect of external magnetic field on the fluctuation phenomena. Plasma jet fluctuates with the frequency of several tens Hz when the magnetic field was applied. These understanding of arc and plasma jet fluctuation enables to improve the capability of long DC arc system.

Drive circuitry of an electric vehicle enabling rapid heating of the battery pack at low temperatures.

SummaryHeating battery at low temperatures is fundamental to avoiding the range anxiety and the time-consuming charging associated with electric vehicles (EVs). One method for achieving fast and uniform battery heating is to polarize the cell under pulse currents. However, the on-board implementation of this method leads to an increase in the cost and size. Therefore, in this study, an adapted EV circuitry compatible with the existing one and an optimized operating condition are proposed to enable rapid battery heating. With this circuit, electricity transfer between the cells can be realized through a motor, leading to remarkably higher battery currents than those of the conventional circuit. The increase in the maximum heating currents (from 1.41C to 4C) resulted in a battery temperature rise of 8.6°C/min at low temperatures. This heating method exhibits low cost, high efficiency, and negligible effects on battery degradation, practical and promising on battery heating of EVs.

Fused-Ring Electron Acceptors for Photovoltaics and Beyond.

ConspectusEmerging solar cells that convert clean and renewable solar energy to electricity, such as organic solar cells (OSCs) and perovskite solar cells (PSCs), have attracted increasing attention owing to some merits such as facile fabrication, low cost, flexibility, and short energy payback time. The power conversion efficiencies (PCEs) of OSCs and PSCs have exceeded 18% and 25%, respectively.Fullerene derivatives have high electron affinity and mobility with an isotropic transport feature. Fullerene-based OSCs yielded superior PCEs to other acceptors and have dominated electron acceptor materials from 1995 to 2015. However, some drawbacks of fullerenes, such as weak visible absorption, limited tunability of electronic properties, laborious purification, and morphological instability, restrict further development of OSCs toward higher PCEs and practical applications. The theoretical PCE of fullerene-based OSCs is limited to ∼13% due to the relatively large energy losses. Many efforts have been dedicated to developing new acceptor systems beyond fullerenes, and some successful systems such as rylene diimides have achieved PCEs up to ca. 11%.In 2015, our group pioneered a new class of electron acceptors, fused-ring electron acceptor (FREA), as represented by the star molecule ITIC. The chemical features of FREAs include: (1) a modular structure, consisting of an electron-donating core, electron-withdrawing end groups, π-bridges, and side chains, which benefits molecular tailoring; (2) facile synthesis, purification, and scalability. The physical features of FREAs include: (1) a broad modulation range of absorption and energy levels; (2) strong absorption, especially in the 700-1000 nm region; (3) high electron mobility. The device features of FREAs include: (1) low voltage loss; (2) high efficiency; (3) good stability. The FREAs boosted PCEs of the OSCs up to 18% and initiated the transformation from the fullerene to nonfullerene era of this field. FREAs can also be used in PSCs as interfacial layers, electron transport layers, or active layers, improving both efficiency and stability of the devices. Beyond photovoltaic applications, FREAs can also be used in photodetectors, field-effect transistors, two-photon absorption, photothermal therapy, solar water splitting, etc.In this Account, we review the development of the FREAs and their applications in OSCs, PSCs, and other related fields. Molecular design, device engineering, photophysics, and applications of FREAs are discussed in detail. Future research directions toward performance optimization and commercialization of FREAs are also proposed.

Enhanced CW Lasing and Q‐Switched Pulse Generation Enabled by Tm3+‐Doped Glass Ceramic Fibers

AbstractFiber lasers, owing to the high beam quality and super robustness, are widely used in fields from optical communications, fiber sensing, biomedicine to material processing. The use of glass fibers as the gain medium has, however, posed a strong obstacle for improving efficiency and, especially, achieving efficient lasing action in the mid‐infrared (MIR) region, because of the relatively large nonradiative energy loss. Here, the fabrication of a Tm3+‐doped tellurate glass‐ceramic (GC) fiber is demonstrated, which enables enhanced lasing action at ≈2 µm. Compared with the as‐prepared fiber, the optical conversion efficiency of GC fiber is increased from 8.8% to 14.1%. The microstructure and spectral characterization analyses suggest that the improvement of the laser performance in GC fiber is induced by the significant change of the local environment surrounding Tm3+ ions due to the formation of nanocrystals within the glass fibers. Moreover, the developed GC fiber also enables Q‐switched pulsed laser output at ≈2 µm with a pulse energy of 3.2 J and pulse width of 4.1 ns. The results demonstrated here may have strong implications in the development of MIR fiber lasers and the applications of GC fibers in MIR photonics.

A detailed second law (excergic) analysis approach of H2O-LiBr vapour absorption cooling system

Vapour absorption technology is generally known as a potential environmental friendly strategy to use solar heat energy reliably for space cooling applications. The thermodynamic analysis is used as an approach for determining efficiency in these systems. Two methods are the first law (FLA) and the second law (SLA) analyses in it. FLA uses the energy conservation of each component and gives the COP of the cycle. Comparing vapour absorption cooling systems on the basis of COPs is not justified. Hence second law is used for a better understanding of the performance. Second law analysis uses exergic method, thereby providing information on the losses in each component of the system which will indirectly influence the COP. During the present work on a single-effect H2O-LiBr vapor absorption cooling system of a ton capacity, a comprehensive SLA has been carried out. Enthalpy, entropy, exergic and dead state values at each state have been found. Exergic values have been compared with the literature values. The reason for the differences in these values has been discussed. The importance of choosing dead state properties of a solution and the proper approach to find it has been provided. Among four key components of a vapour absorption system, an absorber is found to be the component with the largest energy losses.

Adhesion modelling by finite elements of three-dimensional fretting

This work builds a comprehensive adhesion model by finite elements (FEA) for a deformable hemisphere subject to fretting. The hemisphere is constrained between two rigid and frictionless plates as it is loaded in the normal direction and followed by prescribe oscillatory tangential motions. The material for the deformable hemisphere is gold (Au). The normal direction adhesion contact is based on the classic JKR model; however, the tangential resistance is based on the definition of the shear strength and the surface free energy. That is manifested into interfacial bilinear springs where detachment or reattachment of the two contacting surfaces occur when the springs “break” or “snap-back” at the interface. It is shown that the breakage of the springs may be gradual or avalanching. The tangential resistance effect is robust, that is, it is not influenced by the choice of meshing or the spring settings. When the two surfaces are about to detach, the most part of the contact region deforms plastically. At small fretting amplitudes (with no springs breakage), the fretting loop behaves similarly to that of full stick conditions. Hence, the von-Mises stress distributions, plastic strain distributions, and fretting loops, are similar to those of full stick condition. However, the current adhesion model is structurally less stiff because of the bilinear spring. Conversely, at a large oscillation amplitude, the fretting loop exhibits large energy losses, and yet it does not resemble those of gross slip conditions.

Numerical investigation of energy loss mechanism of mixed-flow pump under stall condition

In order to further enrich the theory of rotational stall, this paper explored the mechanism of internal energy loss in the mixed-flow pump under stall condition based on the shear stress transport (SST) k-ω turbulence model, identified the vortices in the impeller by the Q-criterion method, and characterized the turbulence intensity by the turbulent kinetic energy (TKE). The results show that the SST turbulence model can well predict the positive slope characteristics of the energy performance curve of a mixed-flow pump, and there are obvious characteristics of rotating stall in impeller. The numerical results of the energy performance curve and internal flow field are in good agreement with the experimental results. Under stall conditions, there exist swirls and vortices at impeller inlet, which makes the flow inception angle increase by 38°. Meanwhile, the tip leakage flow causes certain energy loss in the rim region, but the high loss area caused by the leakage vortex does not coincide with the core region of the leakage vortex. The interaction between stall vortex and the main flow in the flow passage results in the large-scale blockage area, which is the most fatal effect on the head drop of the mixed-flow pump. The backflow appears on the suction surface of the blade outlet, which has a great impact on the main flow and leads to a large hydraulic loss. The typical characteristics of critical stall and deep stall are found. Under the critical stall condition, part of the leakage flow overflows the leading edge of the lower blade and affects the flow of the next passage. While under deep stall condition, the streamlines of the leading edge of stall vortex reaches the inlet of the next stage blade and overflows, causing a lot of energy loss. And the interference effect between tip leakage flow and stall vortex is strengthened. In general, under the deep stall condition, the average turbulent kinetic energy value in the passages is the highest, and the uniformity of flow rate distribution in the four passages is the worst, resulting in the largest energy loss, which is at the lowest head in the saddle area.

Optimized all-fiber laser Doppler velocimeter with large depth of field

• The structure of the existing laser Doppler velocimeter has been improved to measure a greater depth of field: 0–25 m. • For the first time, the changes of the echo signal strength of the laser Doppler velocimeter at different distances were tested and given graphically, and the signal-to-noise ratio is higher than 15 dB within the whole detection range. • An apparatus for calibrating the speed accuracy of all fiber laser Doppler velocimeter was designed and made. The experimental results showed that the speed accuracy was better than ±0.1 m/s at different distances. Due to the low spatial coupling efficiency of optical fiber and large energy loss, the depth of field in the all-fiber laser Doppler velocimeter is short, and the focus needs to be adjusted before measurement, so it is impossible to continuously measure the velocity of object moving along the optical axis. To solve this problem, an all-fiber Doppler velocimeter based on the Mach-Zehnder interferometer structure is designed, also, in the optical antenna section, C-lens is used to change the divergence angle of the light coming out of the optical fiber. The optimized design achieves the detection with large depth of field. The experiment is designed to verify the intensity of the echo signal, signal-to-noise ratio (SNR) and the speed accuracy of the velocimeter taken in different depths of field. The test results show that the depth of field in this system is superior to 25 m. The SNR is stable around 16 dB with small fluctuation in the range of depth of field, and the speed accuracy is better than ±0.1 m/s.

Nature-Inspired Flow-Fields and Water Management for PEM Fuel Cells

Flow-field design is crucial to polymer electrolyte membrane fuel cell (PEMFC) performance, since non-uniform transport of species to and from the membrane electrode assembly (MEA) results in significant power losses. The long channels of conventional serpentine flow-fields cause large pressure drops between inlets and outlets, thus large parasitic energy losses and low fuel cell performance.Here, a nature-inspired approach is used to design flow-fields guided by the structure of the human lung.[1-4] Its fractal geometry provides scalable, uniform distribution of air from a single outlet (trachea) to multiple outlets (alveoli). Furthermore, the human lung transitions between two flow regimes: 14-16 upper generations of branches dominated by convection, and 7-9 lower generations of space-filling acini dominated by diffusion. The upper generations of branches reduce the gas flow to a rate compatible with the rate in the diffusional regime (Pé ~ 1); in addition, the channel dimensions between branching points are proportioned in a way that results in constant entropy production in both regimes and, thus, in minimal global entropy production over the entire structure of the human lung.By employing a three-dimensional (3D) fractal structure as flow-field inlet channel, we aim to yield similar benefits from replicating these characteristics of the human lung. The fractal pattern consists of repeating “H” shapes, where daughter “H’s” are located at the four tips of the parent “H”. The fractal geometry obeys Murray’s law, much like the human lung, hereby leading to minimal mechanical energy losses. Furthermore, the three-dimensional branching structure provides uniform local conditions on the surface of the catalyst layer, as only the outlets of the fractal inlet channel are exposed to the MEA.Numerical simulations were conducted to determine the number of generations required to achieve uniform reactant distribution and minimal entropy production. The results reveal that the ideal number of generations for minimum entropy production lies between N = 5 and 7, for 10 cm2 surface area.[3, 5] Guided by these simulation results, three flow-fields, with N = 3, 4 and 5, were 3D printed via direct metal laser sintering (DMLS), and experimentally validated against conventional serpentine flow-field based PEMFCs. The fractal flow-field based PEMFCs with N = 4 and 5 generations showed ~20% and ~30% increase in performance and maximum power density over serpentine flow-field based PEMFCs above 0.8 A cm-2 at 50% RH. At fully humidified conditions, though, the performance of a fractal flow-field based PEMFC with N = 5 significantly deteriorates due to flooding issues.[3]Another defining characteristic of the fractal approach is scalability, which is an important feature in nature. Fractal flow-fields can bridge multiple length scales by adding further generations, while preserving the building units and microscopic function of the system. Larger, 3D printed fractal flow-fields (25 cm2 surface area) with N = 4 are compared to conventional serpentine flow-fields. Performance results show that fractal and serpentine flow-field based PEMFCs have similar polarization curves, which is attributed to the significantly higher pressure drop (~ 25 kPa) of large serpentine flow-fields compared to fractal flow-fields. However, such excessive pressure drop renders the use of large serpentine flow-field prohibitive, thus favoring the fractal flow-field.[3]A shortcoming of these fractal flow-fields for PEMFCs operated at high humidity is, though, their susceptibility to flooding in the gas channels, due to low gas velocity. This problem has led to the development of a nature-inspired water management mechanism that draws inspiration from the ability of the Thorny Devil (Australian lizard) to passively transport liquid water across its skin using capillary pressure.[6] We have recently integrated this strategy with the fractal N = 4 flow-fields and verified the viability of the strategy using neutron imaging. Implementation of this water management strategy is expected to circumvent remaining problems of high-generation fractal flow-fields.

Uncovering quirk signal via energy loss inside tracker

The quirk particle carries Lorentz force and long-range infracolor force, while suffers relatively large ionization energy loss inside the detector. It can be indirectly constrained by mono-jet search or directly search through co-planar hits if the confinement scale is not too low ($\Lambda \gtrsim 100$ eV). Considering the ionization energy loss inside tracker, we improve the co-planar search. We also will solve the equation of motion for quirks numerically by including all of the important contributions. Based on our selection strategy, the $\sim 100$ fb$^{-1}$ dataset at the LHC will be able to probe the colored fermion/scalar quirks with masses up to {2.1/1.1 TeV}, and the color neutral fermion/scalar quirks with masses up to {450/150 GeV}, respectively.

A Dynamic Resonant Period Control Technique for Fast and Zero Voltage Switching in GaN-Based Active Clamp Flyback Converters

Compared to Si FETs, when the main GaN FET is in full zero voltage switching condition, maximum switching loss reduction can be achieved. Therefore, in this article, an active clamp flyback converter with GaN devices that implements fast ZVS by using the proposed dynamic resonant period control (DRPC) technique can reduce large transformer leakage inductance energy loss on the active resonant circuit. As the loading changes, the DRPC technique can dynamically adjust the on -time in auxiliary switch to prevent large voltage stress on the components in the primary side. In full load condition, the leakage energy loss can be reduced, thereby transferring more energy to the secondary side with maximum efficiency up to 94%.