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Collecting and mining customer consumption data are crucial to assess customer value and predict customer consumption behaviors. This paper proposes a new procedure, based on an improved Random Forest Model by: adding a new indicator, joining the RFMS-based method to a K-means algorithm with the Entropy Weight Method applied in computing the customer value index, classifying customers to different categories, and then constructing a consumption forecasting model whose RMSE is the smallest in all kinds of data mining models. The results show that identifying customers by this improved RMF model and customer value index facilitates customer profiling, and forecasting customer consumption enables the development of more precise marketing strategies.

The on-chip electrocatalytic microdevice (OCEM) is an emerging platform specialized in the electrochemical investigation of single-entity nanomaterials, which is ideal for probing the intrinsic catalytic properties, optimizing performance, and exploring exotic mechanisms. However, the current catalytic applications of OCEMs are almost exclusively in electrocatalytic hydrogen/oxygen evolution reactions with minimized influence from the mass transfer. Here, an OCEM platform specially tailored to investigate the electrocatalytic oxygen reduction reaction (ORR) at a microscopic level by introducing electrolyte convection through a microfluidic flow cell is reported. The setup is established on gold microelectrodes and later successfully applied to investigate how Ar-plasma treatment affects the ORR activities of 2H MoS

Perovskite solar cells (PVSCs) have drawn great attention due to their high processability and superior photovoltaic properties. However, their further development is often hindered by severe nonradiative recombination at interfaces that decreases power conversion efficiency (PCE). To this end, a facile strategy to construct a 3D/2D vertical heterostructure to reduce the energy loss in PVSCs is developed. The heterostructure is contrived through the van der Waals integration of 2D perovskite ((BA)

Elemental two-dimensional (2D) materials possess distinct properties and superior performances across a multitude of fundamental and practical research fields. Although a tremendous number of earlier studies focus on graphene and its derivatives, other emerging elemental 2D materials, such as borophene, silicene, black phosphorene, antimonene, tellurene, bismuthene and arsenene, are attracting increasing research interest in electronics and optoelectronics, as well as various energy storage and conversion applications, owing to their unique structural, electrochemical and electronic properties. In particular, emerging elemental 2D materials often possess large surface areas, high theoretical capacity, structural anisotropicity, high carrier mobility and tunable bandgaps, making them promising candidates in many energy storage and conversion technologies. Recently, we have witnessed remarkable progress in the preparation, characterization, and application of many emerging elemental 2D materials. However, the challenging yet vastly different synthetic strategies and resulting physicochemical properties, along with complex theoretical and experimental results, make it difficult to navigate through their applications in specific research fields. In this perspective, we summarize the progress of emerging elemental 2D materials in terms of their preparation methods, properties and figures of merit in energy storage and catalytic applications. Furthermore, we present our insight into the challenges and opportunities, which would hopefully shed light on the great potential of this ever-expanding field.

It is vital to develop oxygen evolution reaction catalyst with rational designed composition and microstructure to facilitate the overall electrochemical water splitting. In this work, uniform NixFe1-x-P nanosheets arrays are vertically grown on carbon cloth to form an effective oxygen evolution reaction catalyst. Such structure is prepared by phosphorization of the corresponding layered double hydroxide nanosheets. In this synthesis, the hydroxides are converted to phosphide while the porous nature is well retained. The ratio of Ni to Fe in the phosphide is tuned and the optimized synergistic effect between Ni and Fe for oxygen evolution reaction catalytic activity is achieved. The nanoarrays with hierarchical porous structure offer more reaction sites and promote the charge transfer. As a result, low reaction overpotential and small Tafel slope have been realized. In additional, the synthesis strategy can be also applied to prepare Ni5P4 hydrogen evolution reaction catalyst. A full water electrolyzer is demonstrated with the optimized cathode and anode, and remarkable overall water splitting activity is obtained with a current density of 10 mA cm−2 at the potential of 1.53 V.

The emerging nonlayered 2D materials (NL2DMs) are sparking immense interest due to their fascinating physicochemical properties and enhanced performance in many applications. NL2DMs are particularly favored in catalytic applications owing to the extremely large surface area and low-coordinated surface atoms. However, the synthesis of NL2DMs is complex because their crystals are held together by strong isotropic covalent bonds. Here, nonlayered molybdenum phosphide (MoP) with well-defined 2D morphology is synthesized from layered molybdenum dichalcogenides via surface-confined atomic substitution. During the synthesis, the molybdenum dichalcogenide nanosheet functions as the host matrix where each layer of Mo maintains their hexagonal arrangement and forms isotropic covalent bonds with P that substitutes S, resulting in the conversion from layered van der Waals material to a covalently bonded NL2DM. The MoP nanosheets converted from few-layer MoS

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This paper reports a general electrospinning method to prepare various metal phosphide/carbon nanofibers composite for electrochemical hydrogen evolution reaction (HER) catalysts. An earth-abundant organic acid-phytic acid is successfully incorporated into a conventional electrospinning precursor as the phosphorus source, and continuous nanofibers can be obtained through spinning. After heat treatment, metal phosphide/carbon composite nanofibers can be obtained, with fine phosphide nanoparticles well dispersed on the surface of an interconnected carbon backbone network. Such fibrous structures offer fast charge transfer pathways and enlarged active surface area, which are beneficial for electrocatalysts. As a result, enhance HER catalytic activity can be achieved.

This work reported Co9S8 nanoparticle-decorated carbon nanofibers (CNF) as a supercapacitor electrode. By using a mild ion-exchange method, the cobalt oxide-based precursor nanoparticles were transformed to Co9S8 nanoparticles in a microwave hydrothermal process, and these nanoparticles were decorated onto a carbon nanofiber backbone. The composition of the nanofibers can be readily tuned by varying the Co acetate content in the precursor. The porous carbon nanofibers offered a fast electron transfer pathway while the well dispersed Co9S8 nanoparticles acted as the redox center for energy storage. As a result, high specific capacitance of 718 F g−1 at 1 A g−1 can be achieved with optimized Co9S8 loading. The assembled asymmetric supercapacitor with Co9S8/CNF as the cathode showed a high energy density of 23.8 W h kg−1 at a power density of 0.75 kW kg−1 and good cycling stability (16.9% loss over 10 000 cycles).

This work reports the synthesis of coaxial carbon@NiMoO4 nanofibers for supercapacitor electrode applications. Thin NiMoO4 nanosheets are uniformly coated on the conductive electrospun carbon nanofibers by a microwave assisted hydrothermal method to form a hierarchical structure, which increases the porosity as well as the conductivity of the electrode. The thickness of the NiMoO4 can be easily adjusted by varying the precursor concentrations. The high specific surface area (over 280 m2 g−1) and conductive carbon nanofiber backbone increase the utilization of the active pseudocapacitive NiMoO4 phase, resulting a high specific capacitance of 1840 F g−1.

The design of hierarchical electrodes comprising multiple components with a high electrical conductivity and a large specific surface area has been recognized as a feasible strategy to remarkably boost pseudocapacitors. Herein, we delineate hexagonal sheets-in-cage shaped nickel-manganese sulfides (Ni-Mn-S) with nanosized open spaces for supercapacitor applications to realize faster redox reactions and a lower charge-transfer resistance with a markedly enhanced specific capacitance. The hybrid was facilely prepared through a two-step hydrothermal method. Benefiting from the synergistic effect between Ni and Mn active sites with the improvement of both ionic and electric conductivity, the resulting Ni-Mn-S hybrid displays a high specific capacitance of 1664 F g-1 at a current density of 1 A g-1 and a capacitance of 785 F g-1 is maintained at a current density of 50 A g-1 , revealing an outstanding capacity and rate performance. The asymmetric supercapacitor device assembled with the Ni-Mn-S hexagonal sheets-in-cage as the positive electrode delivers a maximum energy density of 40.4 Wh kg-1 at a power density of 750 W kg-1 . Impressively, the cycling retention of the as-fabricated device after 10 000 cycles at a current density of 10 A g-1 reaches 85.5 %. Thus, this hybrid with superior capacitive performance holds great potential as an effective charge-storage material.

Asymmetric supercapacitors have emerged as one of the most appropriate energy storage systems. Enhancing the specific capacity of electrode materials at high current densities is a critical issue in asymmetric capacitors. Herein, we optimized a simple strategy to develop partial reduced hierarchical nanosheets shaped nickel-cobalt layered double hydroxide with Ag nanoparticles for efficient charge storage. The composite cathodes are prepared using a mild hydrothermal method followed by a liquid phase reduction process. Benefiting from the electric conductivity tuning, the hybrids reveal better capacitive performances. Among all, the nickel-cobalt layered double hydroxide with 5 wt.% Ag decoration presents a high specific capacitance of 1338 F g − 1 at a current density of 10 A g − 1 with a good capacity retention of 660 F g − 1 at 60 A g − 1, implying its fascinating rate capability. Besides, the established capacitor device achieves an energy density of 43.07 Wh kg−1 at a power density of 400 W kg−1. Interestingly, the device exhibits excellent long-term durability for 10,000 consecutive cycles of repeated charge-discharge processes at 12.5 A g − 1 with a capacity retention of 89.6%. Such a high performance suggests a practical and feasible approach as three-dimensional (3D) electrode tailoring for sustainable energy storage devices.

The controllable introduction of heteroatoms into electrode materials via doping is one of the most effective strategies to realize improved electrochemical reaction kinetics and then electrochemical energy storage properties. Herein, vanadium doped nickel-cobalt layered double hydroxide nanosheet arrays (NCV-LDH NSAs) were prepared via a one-step hydrothermal method and applied as a new class of efficient supercapacitor electrode. Benefiting from the exceptional porosities and abundant electroactive sites, the hierarchical NCV-LDH NSAs based electrodes reveal enhanced pseudocapacitive behaviors. Among all, the NCV-LDH-10 displays the highest performance with a specific capacitance of 2960 F g−1 at a current density of 1 A g−1 and retains 762 F g−1 at a high current density of 50 A g−1. The asymmetric supercapacitor was assembled based on NCV-LDH-10 hybrid and activated carbon (AC). It achieves a high energy density of 31.95 Wh kg−1 at a power density of 356 W kg−1. It is worth noting that the integrated electrode exhibits remarkable long-term cycling stability at a current density of 10 A g−1 and preserves about 81.8% of its original capacitance after 10,000 continuous cycles. The outcomes achieved can provide a potential chance for practical application in sustainable energy storage systems.

Ni(OH)2 nanosheets (NSs) were grown onto an electrochemically activated carbon cloth (ECC) with a self-supported microstructure by using efficient ethanol assisted supercritical deposition method. Benefited from the structural features of the well-developed porous architecture with effective channels for electrolyte ions diffusion and accessible redox sites, the nano-heterostructure brings a high utilization of electroactive material and thereby good electrochemical performance. The specific capacity of 918 mC cm−2 at 2 mA cm−2 with good rate performance (68.4 % retention at 20 mA cm−2) was achieved for the obtained Ni(OH)2 NSs/ECC flexible electrode. The assembled flexible solid-state device with a 1.8 V operating potential displays an energy density of 8.3 mW h cm-3 at 20 mW cm-3. Additionally, the as-fabricated device reveals cyclic stability with 87 % capacity retention (10,000 cycles at 50 mA cm−2). These results show the importance of supercritical fluid deposition as a potential method for supercapacitors electrode.

This work reports the synthesis of coaxial carbon@NiMoO

This work reported Co

In this paper, some non-linear diagnostic methods for rotating machinery are introduced and evaluated from the view of diagnostic practice. The methods are pseudo-phase portrait, singular spectrum analysis and correlation dimension. The pseudo-phase portrait is simple, easy to draw, and is sensitive to some fault types. Singular spectrum analysis can reveal the complexity of a signal. By means of singular spectrum analysis one can reduce the noise of a signal. Correlation dimension can provide some intrinsic information of an underlying dynamical system, and can be used to classify different faults intelligently. Examples show that all these methods are advantageous in the field of non-linear diagnostics. Therefore, it is quite reasonable for effective fault diagnosis to use non-linear diagnostic methods in addition to the methods currently used, such as orbit portrait, FFT spectra, time–frequency analysis, etc.

This paper reports on the application of nonlinear dynamics andhigher-order spectra, with particular regard to the correlationdimension and bispectra in rotating machinery fault identification. Theperformance of the two methods is evaluated from the view of thepractitioners' point. The correlation dimension of nonlinear dynamicalsystem is of value to engineers because it provides an estimation of thenumber of degrees of freedom that an engineering system possesses. Itcan provide some intrinsic information of an underlying dynamic system,and can be used to classify different faults intelligently. Therefore,correlation dimension is helpful for an automatic fault detectionprocedure. Bispectral analysis offers a method for determining thenonlinear coupling and energy exchange between Fourier modes, andexplains the origins of spectra peaks at certain values in the frequencyspectrum. Such frequency domain information is necessary in order toclassify different faults in rotating machinery. Therefore, acombination of correlation dimension and bispectra offer a gooddescription of a nonlinear system. These methods can be complementary toeach other in machinery condition monitoring and fault diagnosis field.

This paper reports on the application of the correlation dimension in large rotating machinery fault diagnosis. The Grassberger-Procaccia algorithm and its modified version are introduced. Some important influencing factors relating directly to the computational precision of the correlation dimension are discussed. Industrial vibration signals measured from large rotating machinery with different faults are researched using the above-mentioned methods. The results show that the correlation dimension can provide some intrinsic information on an underlying dynamic system and can be used to classify different faults intelligently.

Manganese and cooper doped FeSi2 and Fe2Si5 alloys were prepared by a rapid solidification technique. X-ray diffraction analysis showed that the as-solidified FeSi2 alloy is composed of α-Fe2Si5 and e-FeSi phases, while only the α-Fe2Si5 phase exists in the as-solidified Fe2Si5 alloy. The semiconducting phase β-FeSi2 has not been found in the as-solidified structures but was obtained after annealing for 21 h at 800°C for both alloys. It was found that the excess silicon over the stoichiometric silicon content of the β-FeSi2 phase could improve the transport properties of the materials.