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An autonomous underwater vehicle (AUV) can only carry limited energy for improved flexibility, but this brings the problem of working endurance. The acquisition of environmental energy by an underwater robot is a positive way to supplement energy and increase endurance. However, the instability and difference in power output capacity of different environmental energies will lead to low utilization of environmental energy. In this study, a multi-energy acquisition model is established to manage the AUV’s energy, which includes a heart rate sampling system, a mixed-energy circuit topology, and a maximum power output algorithm of environmental energy based on power trajectory tracking. The simulating results show that the power output control strategy can effectively improve the multi-energy acquisition and utilization efficiency of underwater vehicles, which has a positive significance and could improve endurance time.

Additional file 10: Table S1. Clinicopathologic characteristics of patients.

The structure of current collectors has significant effects on the performance of a lithium-ion battery (LIB). In this study, we use copper fiber felts made by multi-tooth cutting and high-temperature solid-phase sintering as the current collector for LIBs. An integrated porous electrode based on CuO nanoflowers/copper fiber felt is developed for the anode. Results suggest that the reversible capacity and cycle stability of this new anode are significantly improved, compared with the pristine bare-surface copper plate under the same condition of rate cycles. The new anode structure based on the copper-fiber felt with a porosity of 60% exhibits a higher performance with an initial specific capacity of 609.5 mAh g−1 and retains 486.1 mAh g−1 after 200 cycles at a current density of 0.5 C. The improved electrochemical performance of this electrode is attributed to its large surface area of CuO nanoflowers and porous structure of the copper fiber felt, due to enhanced contact between the active material of CuO nanoflowers and electrolyte. This pore-rich structure makes the electrolyte easy to permeate into the electrode, shortens the diffusion path of Li+, reduces the internal resistance and alleviates the volume expansion of the active material during the insertion and desertion processes of Li+.

The lithium-ion battery (LIB) is an efficient electrochemical energy storage device with high voltage, long life, good safety, etc. Silicon has a high theoretical specific capacity (4200 mA h g−1), due to which it is considered a promising anode material for next-generation LIBs. However, the huge volume change (400%) of the Si material during the lithiation/delithiation processes destroys its structure, which greatly reduces the initial coulombic efficiency, cycle stability and rate performance of the battery. Accordingly, constructing nanostructured Si, particularly silicon nanowires (SiNWs), can help to address the above issues. Additionally, it is important to further improve the electrochemical performance by incorporating some additives in SiNW-based electrodes. Therefore, this review focuses primarily on SiNW-based materials as anodes for LIBs from a material-based perspective. Various materials incorporated into SiNW-based anodes through doping or compositing are reported. The electrochemical effects of diverse additives, including carbon materials, metals, metal oxides, polymers, Si-based materials and other special substances, are comprehensively reviewed.

Lithium-ion batteries (LIBs) play an important role in modern society. The low capacity of graphite cannot meet the demands of LIBs calling for high power and energy densities. Silicon (Si) is one of the most promising materials instead of graphite, because of its high theoretical capacity, low discharge voltage, low cost, etc. However, Si shows low conductivity of both ions and electrons and exhibits a severe volume change during cycles. Fabricating nano-sized Si and Si-based composites is an effective method to enhance the electrochemical performance of LIB anodes. Using a small size of Si nanoparticles (SiNPs) is likely to avoid the cracking of this material. One critical issue is to disclose different types and electrochemical effects of various coupled materials in the Si-based composites for anode fabrication and optimization. Hence, this paper reviews diverse SiNP-based composites for advanced LIBs from the perspective of composition and electrochemical effects. Almost all kinds of materials that have been coupled with SiNPs for LIB applications are summarized, along with their electrochemical influences on the composites. The integrated materials, including carbon materials, metals, metal oxides, polymers, Si-based materials, transition metal nitrides, carbides, dichalcogenides, alloys, and metal-organic frameworks (MOFs), are comprehensively presented.

With the development of GEN-IV nuclear reactor technology, the supercritical carbon dioxide (SCO2) Brayton cycle has attracted wide attention for its simple structure and high efficiency. Correspondingly, a series of research has been carried out to study the characteristics of the cycle. The control flexibility of the power generation system has rarely been studied. This paper carried out a dynamic performance of the 20 MW-SCO2 recompression cycle based on the Simulink software. In the simulation, the response characteristics of the system main parameters under the disturbances of cooling water temperature, split ratio, main compressor inlet temperature and pressure were analyzed. The results show that the turbine inlet temperature is most affected by the disturbances, with a re-stabilization time of 2500–3000 s. According to the response characteristics of the system after being disturbed, this study proposed a stable operation control scheme. The scheme is coordinated with the main compressor inlet temperature and pressure control, recompressor outlet pressure control, turbine inlet temperature control and turbine load control. Finally, the control strategy is verified with the disturbance of reduced split ratio, and the results show that the control effect is good.

The Fe15−xMn40Al45+x (x = 0, 1, 2 and 3) and Fe15Mn40−yAl45+y (y = 1, 2 and 3) alloys were prepared by arc melting and annealed at 1000 °C for 7 days. The microstructure and magnetic properties are characterized by XRD and VSM. Corresponding corrosion potential and hardness are measured by electrochemical workstation and Vickers hardness tester. All samples have CsCl type Cubic structure. And for Fe15Mn40−yAl45+y alloys, with increasing Mn content, the lattice parameters increase from 2.9613 A to 2.9678 A, while the curie temperatures can be tuned from 288 K to 330 K. As for Fe15−xMn40Al45+x alloys, the curie temperatures rise from 315 K to 340 K with lattice parameters increasing from 2.9658 A to 2.9689 A. The peak values of magnetic entropy change under 5 T are −2.4 and −3.1 J·kg−1K−1 for Fe15Mn40Al45 and Fe14Mn40Al44 respectively. The values of refrigerant capacity power are 223.4 and 232.5 J·kg−1 under 5 T. The Arrott plots are also employed to investigate the magnetic phase transition, showing all samples undergo second order ferro-paramagnetic phase transition. Furthermore, these alloys have good hardness and corrosion resistance properties. The potential applications of these alloys as magnetic refrigerant will be also discussed in this paper.

The surface microstructure of the current collectors significantly affects the electrochemical performance of lithium-ion batteries (LIBs). This study shows that an effective method of orthogonal p...

In this paper, we propose an approach to handle the anomaly detection for the thermal system on ships by the sensor associated network method. A large number of sensors are placed in different positions of the thermal system. These sensors form a topological network which can represent the operation state of the thermal system. There are both linear correlation and nonlinear correlation between the operating parameters reflected by these sensors. The MAS index from MINE is utilized to represent the correlation information between sensors when the thermal system is in dynamic operation condition. Based on the MAS correlation coefficient, the sensor correlation network is constructed to represent the dynamic operation process of thermal system. Using DBSCAN clustering algorithm, the large topological network is divided into different subnetworks. When the system is running dynamically, the Manhattan distance between the sub networks can reflect the running state of the system. Based on the distance of sub networks, the similarity of sensor networks with continuous changes is calculated and the similarity correlation sequence is formed. Through the matching between the similarity correlation sequence and the historical experience sequence, we can judge whether the system dynamic condition is abnormal. By the simulation experiment data, we verify the effectiveness of the proposed method.

The magnetic anisotropy of SmCo-based permanent magnetic thin films are generally controlled by introducing buffer layer or heating substrate. However, the design for the multi-layer thin film system is complicated and the thickness of SmCo is limited due to a short range of interfacial stress/strain between the buffer layer and SmCo layer. In this work, the effects of temperature gradients, generated by RTP (rapid thermal process), on the magnetic anisotropy of the SmCo-based films were systematically investigated. The results show that the as-deposited films exhibit amorphous state. The out-of-plane coercivity of RTP-treated films is strongly correlated with the heating rate, and its optimum value (2810 Oe) is larger than that of the CTA (conventional thermal annealing) treated films (1670 Oe). For the RTP-treated films, the intensity of characteristic diffraction peaks for in-plane oriented SmCo5 (200) and Sm2Co17 (300) decreases, together with reducing the roughness. Besides, the grain size is finer and the contrast of magnetic domains becomes stronger for the RTP-treated films due to that the easy axis of SmCo5/Sm2Co17 phase gradually changes from in-plane to out-of-plane direction. It is suggested that the RTP treatment with a shorter annealing time has beneficial effects on obtaining finer microstructure and improving the out-of-plane magnetic anisotropy of the SmCo-based films. This work provides a novel way to control the magnetic anisotropy via annealing temperature gradients for permanent magnetic thin films, compared with conventional methods, to induce the magnetic anisotropy.

A conductive layer, made of multi-walled carbon nanotubes (MWCNTs), with micro-cracks and a micro/nano porous structure was fabricated between the active material layer (AML) and the current collector in this study. The coating thickness of MWCNTs-based conductive layer (MCL) varies in the range of 25-100 μm. The electrochemical tests of half-cells demonstrate that both the mesocarbon-microbeads (MCMB) anode and the LiCoO2 cathode with a micro-cracked MCL show higher capacity, lower impedance and less capacity fading. These improvements are closely due to the enhancement of adhesion strength, and also the outstanding buffer effect of the micro-cracked MCL. With the change of the coating thickness, the size and amount of the micro-cracks on the MCL varies accordingly to accommodate the active material with different particle sizes. The electrodes including a micro-cracked MCL with a coating thickness of 50 and 75 μm are more suitable for MCMB and LiCoO2 with a particle size of 10-20 μm.

The energy density and operational life of lithium-ion batteries (LIBs) depend sensitively on the properties of electrode materials. Transition metal oxide based electrodes attract much attention because of their potential to offer high energy density. In this study, we report a binder-free composite anode composed of CuO nanosheets and multi-wall carbon nanotubes for LIBs. This composite anode is fabricated by a cost-effective electrophoretic deposition process followed by facile solution immersion. When tested in a LIB, this composite anode delivers a high reversible capacity of 540 mAh g−1 and maintains its capacity retention of above 78% after 50 cycles at a current density of 100 mA g−1, which is much higher than the CuO anode without carbon nanotubes. The high capacity, enhanced rate capability, low resistance, and increased operational life are attributed to the unique architecture of the hybrid electrode. The carbon nanotubes facilitate the electron transfer, enhance the structural stability of CuO nanosheets, and improve the adhesion of the CuO nanosheets to current collector. Such highly porous cross-linked network based on CuO nanosheets and multi-wall carbon nanotubes has great potential as a binder-free anode for high-performance LIBs.

The relation between the microstructure and the magnetic properties of Fe2P-type (Mn,Fe)2(P,Si,B) based materials has been systematically investigated by changing the annealing temperature and time. X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy measurements show that the alloys contain the main Fe2P-type phase and two impurity phases of (Fe,Mn)5Si3-type and Fe2MnSi-type. Boron appears to facilitate the formation of the Fe2P-type phase during the arc-melting progress. Upon increasing the annealing temperatures from 1123 to 1423 K, the Curie temperature (TC) decreases from 302.0 to 270.5 K in the Mn1.15Fe0.85P0.55Si0.45 alloys and the magnetic-entropy change (ΔSM) increases linearly with annealing temperature. For the Mn1.15Fe0.85P0.52Si0.45B0.03 alloys annealed at 1423 K for different times, TC decreases from 263.8 and 232.8 K with increasing annealing time and ΔSM reaches a maximum value after annealing for 48 h. The differences in the annealing temperature and time influence the Si content in the Fe2P-type phase of the alloys and determine TC, the thermal hysteresis and the magneto-elastic transition.

Fe-based metallic glass has been reported to exhibit high degradation ability for azo dye due to its unique atomic structure. In this work, we show that the degradation efficiency of Fe-based alloy can be further improved via simple heat treatment. Fe82Si2.5B12P2.5C amorphous ribbons were prepared by arc melting and melt spinning and then annealed from 100 °C to 850 °C for 5 min. A crystallization process from single α-Fe at 500 °C, to α-Fe + Fe3B at 520 °C, to α-Fe + Fe3B + Fe2C at 850 °C, took place. The degradation efficiency of the heat-treated ribbons decreased monolithically when annealed at 100-600 °C, but increased dramatically at 850 °C. The underlying degradation mechanisms were analyzed, that the formation and interaction of nanocrystals after annealing were considered mainly responsible for the differences in their degradation performances.

The effects of Co on microstructure, crystallization behavior and magnetic properties of (Ni0.5Fe0.5-xCox)80B10Si2Cu1Zr7 (x = 0~0.5) alloys were investigated. The results show that, the as-spun alloys remain lower coercivity (Hc) values (5 A/m ~ 14 A/m) over the whole Co content range, owing to their amorphous structure. After being annealed for 20 min above the onset temperatures of primary crystallization (Tx1), amorphous and nanocrystallines are coexisted in the alloys, and the crystal structure of nanocrystallines changes between fcc-(Ni, Fe, Co) and bcc-(Fe, Ni, Co) with the increasing Co content. In particular, it was found that Hc of the annealed alloys changes anomalously between 40 A/m and 1529 A/m with the increasing Co content, owing to the integrated action of grain size (D), magnetocrystalline anisotropy (K1) and lattice distortion. Especially for the alloys with x = 0.2 and x = 0.3, serious lattice distortion is the dominant factor for their higher Hc value than 1000 A/m.

This study presents a hierarchical MCMB/CuO/Cu anode structure with super-hydrophilic CuO substrate and blind-hole structures (BHSs) for lithium-ion battery (LIB) application. The porous hierarchical CuO clusters with controllable morphology and super hydrophilicity are prepared and combined with the BHSs on the surface of copper plates (CPs). Results indicate that the new anode yields a considerable improvement in reversible capacity and robustness under the condition of rate cycles. Compared with the conventional pattern of MCMB/Cu, the MCMB/CuO/Cu anode with BHSs produces reversible initial discharge and charge capacities of 381.5 and 347 mAh g−1 at a constant current of 0.5 mA. After 30 cycle times, the battery retains 276.7 and 276.6 mAh g−1, which amounts to 5 times as much as that of 0.5 C rate cycles. The energy density of the battery can be also greatly promoted. The larger surface area and porosity of the new anode facilitate formation of contact interface between the active material and current collector (CC). It also helps shorten the diffusion path of Li-ions and alleviate the volume expansion during the insertion and desertion processes of Li-ions.

Developing high-performance electrode structures is of great importance for advanced lithium-ion batteries. This study reports an efficient method to fabricate hierarchical shell/core CuO nanowire/carbon fiber composites via electroless plating and thermal oxidation processes. With this method, a binder-free CuO nanowire/carbon fiber shell/core hierarchical network composite anode for lithium-ion batteries is successfully fabricated. The morphology and chemical composition of the anode are characterized, and the electrochemical performance of the anode is investigated by standard electrochemical tests. Owing to the superior properties of carbon fibers and the morphological advantages of CuO nanowires, this composite anode still retains an excellent reversible capacity of 598.2 mAh g −1 with a capacity retention rate above 86%, even after 50 cycles, which is much higher than the CuO anode without carbon fibers. Compared to the typical CuO/C electrode systems, the novel binder-free anode yields a performance close to that of the typical core/shell electrode systems and a much higher reversible capacity and capacity retention than the similar shell/core patterns as well as the anodes with binders. It is believed that this novel anode will pave the way to the development of binder-free anodes in response to the increasing demands for high-power energy storage.