Search

Cu2Se‐based binary compounds have recently fetched the attention of researchers due to their remarkable electrical and extremely low thermal properties. In addition, Cu2Se‐based quaternary chalcogenides are expected to present exceptional thermoelectric performance. Cu2Se1−x−ySxTey‐like compounds are synthesized via microwave‐assisted hydrothermal method and their respective thermal and electrical transport properties are studied in this research work. The phase purity and homogeneity are examined by X‐ray diffraction and energy‐dispersive X‐ray spectrometry analysis. The introduction of S and Te elements into Cu2Se matrix enhances Seebeck coefficient resulting in improved electrical performance illustrating a maximum power factor of 989.4 μWK−2 m−1 at 673 K. Furthermore, S‐ and Te‐co‐doped samples exhibit reduced total thermal conductivity values with lowest value of 0.808 WK−1 m−1 for Cu2Se0.96S0.02Te0.02 sample in comparison to 1.18 WK−1 m−1 for the pristine sample. The simultaneous improvement in electrical and thermal properties results in enhanced figure of merit of 0.82 for Cu2Se0.96S0.02Te0.02 sample at 673 K. [ABSTRACT FROM AUTHOR]

Al-based alloy ingots are a highly promising material for on-demand hydrogen supply. However, the use of Sn in them restricts the recovery and reuse of alloying elements, and also decreases the purity of byproducts, resulting in a significant increase in the application cost. Herein, a series of Sn-free ternary Al-alloys are prepared and their hydrogen production performance are investigated. Experimental results indicate that the Sn-free Al-Ga-In alloys maintain good hydrogen production performance, and the hydrolysis reaction is more stable and sustained than that of Al-Ga-In-Sn alloys. As the optimized formula, the 94Al-4.73Ga-1.27In alloy exhibits a high hydrogen conversion efficiency of 97.3% and an extremely stable average hydrogen production rate of 0.01423 L/min at 50 °C. In addition, a semi-coherent phase boundary-derived activation mechanism during Al hydrolysis was proposed. This study opens up a prospect for the development and large-scale using of recyclable Al-based on-demand hydrogen supply materials. [Display omitted] • Recyclable Sn-free Al-based alloys are developed for on-demand hydrogen supply. • Optimized alloys show stable H 2 production rate and achieve 97.3% energy conversion. • The hydrolysis reaction of Sn-free Al alloys is activated by the liquid phase. • Semi-coherent phase boundaries promote the hydrolysis reaction of alloys. [ABSTRACT FROM AUTHOR]

The failure features of rolling bearings are often weak due to the influence of strong background noise. In addition, the vibration signals of faulty rolling bearing often show nonlinear and non-stationary characteristics, and the conventional time-frequency method is no longer suitable for extracting effective fault features. In order to extract the early weak fault characteristics of rolling bearing accurately, a weak fault feature extraction method for rolling bearing by combining adaptive chirp mode decomposition (ACMD) based on sparsity index regrouping scheme with time-delayed feedback stochastic resonance (TDSR) is proposed in the paper. The proposed method comprehensively utilizes the adaptive decomposition characteristics of ACMD for multi-component non-stationary signals and the enhancement effect of TDFSR on low-frequency signals in the fast Fourier transform (FFT) result. Firstly, ACMD is used to decompose the early weak fault signal of rolling bearing into a series of mode signals, then the proposed signal regrouping scheme based on sparsity index is utilized to regroup the obtained series of modes. Secondly, the optimal reconstructed component containing the main fault information is input into the calculation model of TDSR. Finally, FFT is performed on the output signal of TDSR to extract the fault characteristics effectively. [ABSTRACT FROM AUTHOR]

Purpose: Patients with advanced cancer are usually willing to participate in shared decision-making (SDM), but in clinical practice, patient participation is easily ignored. This study aimed to analyze the current SDM status of advanced cancer patients and related factors. Methods: In quantitative research, we administered a cross-sectional survey to 513 advanced cancer patients in 16 tertiary hospitals in China. A sociodemographic information questionnaire, the Control Preference Scale (CPS), and Perceived-Involvement in Care Scale (PICS) were used to analyze current SDM status and influencing factors. Our qualitative research was based on the Ottawa Decision Support Framework (ODSF), and 17 advanced cancer patients were interviewed to explore their perceptions of SDM. Results: Our quantitative results show that patients’ actual and expected decision-making participation differed; statistically significant influencing factors were age, insurance, and whether patients were worried about the therapeutic effects. We also found that dynamic decision-making mode changes, disease information acquisition, decision-making participation obstacles, and family members’ roles affected patients’ SDM through qualitative interviews. Conclusion: Advanced cancer patients’ SDM in China is dominated by sharing and continuously fluctuates. Influenced by Chinese traditional culture, family members play an important role in SDM. In clinical work, we should pay attention to the dynamic changes in patients’ participation in decision-making and the role of family members. [ABSTRACT FROM AUTHOR]

In this study, the effect of drying approaches in conjunction with variable temperature and tempering on the physicochemical quality of rice was investigated. The development of fissures, head rice yield, taste quality, textural properties, and microstructure of rice with different drying approaches were evaluated by employing principal component analysis (PCA). The results showed that increasing the tempering treatment could enhance the physicochemical quality of rice, and that the different drying approaches had a significant influence (P < 0.05) on the development of fissures, head rice yield, taste quality, and textural properties. High temperatures result in partial gelatinization of the starch, destruction of the starch granules, and an increase in fissures, as revealed by the microstructure of rice with different drying approaches. In addition, the drying approaches with a variable temperature of Δ0 (35 °C), Δ5 (45 °C–50 °C), and Δ0 (45 °C) in combination with the tempering treatment exhibited a high overall physicochemical quality. This study offers a point of reference for further research into the changes in the physicochemical quality of rice during drying. [ABSTRACT FROM AUTHOR]

To solve the difficulty in weak fault detection of rolling element bearing (REB), a fusion method by combining robust empirical mode decomposition (REMD) with adaptive maximum second-order cyclostationarity blind deconvolution (AMCBD) is proposed in the paper. The advantage of REMD in determining the optimal iteration number of a sifting process and the advantage of AMCBD in setting the key parameter (targeted cyclic frequency or fault period) appropriately are utilized comprehensively by the proposed method. Firstly, in view of the multi-component and modulation characteristic of the vibration signal of REB, REMD is used to extract the useful component from the multi-component and modulated signal. Then, AMCBD is used to process the selected useful component to further highlight the cyclostationary and impulse characteristics of the vibration signal of faulty REB. Compared with traditional maximum second-order cyclostationarity blind deconvolution (MCBD) method, AMCBD has the advantage of no needing prior knowledge of the faulty REB such as the targeted cyclic frequency or fault period. At last, envelope spectral (ES) is applied on the signal handled by AMCBD and satisfactory fault extraction feature result is obtained. Effectiveness of the proposed method is verified through simulated, experimental, and engineering signals, and its superiority is also presented through comparison study. [ABSTRACT FROM AUTHOR]

As the most commonly used support component in engineering, rolling element bearing is also the most prone-to-failure part. The vibration signal of faulty bearing will take on repetitive impact and modulation characteristics, and the two features are often difficult to be extracted by conventional fault feature extraction methods such as envelope spectral. The main reasons are due to the influence of strong background noise, the signal attenuation of the acquisition path, and the early weak failure characteristics. To solve the above problem, a weak fault feature extraction method of rolling element bearing by combing improved minimum entropy de-convolution with enhanced envelope spectral is proposed in the paper. The enhancement effect of improved minimum entropy de-convolution on impact features and the satisfactory extraction effect of EES on repetitive impact and modulation features are utilized comprehensively by the proposed method. Firstly, improved minimum entropy de-convolution is used to filter the vibration signal of faulty bearing to enhance the impact characteristics, and the influence of signal acquisition path on the attenuation of the signal characteristics is also weakened at the same time. Then, enhanced envelope spectral is performed on the filtered signal, and the repetitive impact and modulation characteristics of vibration signal are extracted synchronously. In order to solve the shortcomings of the current commonly used de-convolution methods, an improved minimum entropy de-convolution method based on D-norm is proposed, which can solve the interference caused by random impulsive signals effectively. In addition, compared with the conventional method such as envelope spectral, the enhanced envelope spectral method could extract the repetitive impact and modulation characteristics of the faulty signal simultaneously much more effectively. Effectiveness and superiority of the proposed method are verified through simulation, experiment, and engineering application. [ABSTRACT FROM AUTHOR]

Background: Diabetic cardiomyopathy is characterized by left ventricle dysfunction, cardiomyocyte apoptosis, and interstitial fibrosis and is a serious complication of diabetes mellitus (DM). Autophagy is a mechanism that is essential for maintaining normal heart morphology and function, and its dysregulation can produce pathological effects on diabetic hearts. Neuregulin-4 (Nrg4) is an adipokine that exerts protective effects against metabolic disorders and insulin resistance. The aim of this study was to explore whether Nrg4 could ameliorate DM-induced myocardial injury by regulating autophagy. Methods: Four weeks after the establishment of a model of type 1 diabetes in mice, the mice received Nrg4 treatment (with or without an autophagy inhibitor) for another 4 weeks. The cardiac functions, histological structures and cardiomyocyte apoptosis were investigated. Autophagy-related protein levels along with related signalling pathways that regulate autophagy were evaluated. In addition, the effects of Nrg4 on autophagy were also determined in cultured primary cardiomyocytes. Results: Nrg4 alleviated myocardial injury both in vivo and in vitro. The autophagy level was decreased in type 1 diabetic mice, and Nrg4 intervention reactivated autophagy. Furthermore, Nrg4 intervention was found to activate autophagy via the AMPK/mTOR signalling pathway. Moreover, when autophagy was suppressed or the AMPK/mTOR pathway was inhibited, the beneficial effects of Nrg4 were diminished. Conclusion: Nrg4 intervention attenuated diabetic cardiomyopathy by promoting autophagy in type 1 diabetic mice. Additionally, Nrg4 induced autophagy via the AMPK/mTOR signalling pathway. [ABSTRACT FROM AUTHOR]

Vibration signals of rolling element bearing's early weak fault are often submerged by some interference components. To extract early weak fault features accurately, a weak fault feature enhancement method of rolling element bearing based on resonance sparse decompositionand multi-objective information frequency band selection is proposed. This method makes full use of resonance sparse decomposition in filtering the interferences and multi-objective information frequency band selection in enhancing impulsive and cyclostationary features of rolling element bearing's early weak fault simultaneously. First, resonance sparse decomposition is used as the preprocessing program of multi-objective information frequency band selection to filter the interferences (such as rotating frequency with its harmonics) of rolling element bearing's early weak fault characteristic components. Then, the filtered components containing main fault information are analyzed by MIFBS to establish the best band-pass filter. Finally, the envelope spectrum analysis is applied on the filtered vibration signal, and the fault characteristic frequency with its harmonics is extracted. To achieve the optimal output parameters of multi-objective information frequency band selection, fusion indexes based on time- and frequency-domain estimators are proposed and used to balance the enhancement of impulsive and cyclostationary characteristics of rolling element bearing's early weak fault signals. Compared with most of the existing methods mainly based on single time-domain estimators or frequency-domain estimators to improve performance spectral kurtosis, the proposed fusion indexes overcome their defects and could enhance the impulsive and cyclostationary features of rolling element bearing's early weak fault simultaneously. Effectiveness of the proposed method is verified through simulation and experiment. Besides, its advantage over the other related methods is also presented. [ABSTRACT FROM AUTHOR]

In this study, DBNs‐aminated layered double hydroxide (ALDH) was prepared by connecting ALDH with hydroxylated boron nitride nanosheet (OH–BNs) which was obtained by high‐temperature steam method from hexagonal boron nitride nanosheet (h‐BNs) through the polydopamine. DBNs‐ALDH was characterized by fourier‐transform infrared spectroscopy, x‐ray diffraction, scanning electron microscope, energy dispersive spectrometer, transmission electron microscope, Raman, and x‐ray photoelectron spectroscopy analyses to prove the success of the synthesis. Change of chloride ion concentration was chosen to evaluate the ion exchange function of DBNs‐ALDH. Then, the epoxy resin (EP) mixed with DBNs‐ALDH was coated on the Q215 steel to form a composite epoxy coating. The electrochemical impedance spectroscopy test and brine immersion test were used to characterize the anticorrosion performance of composite EP coating. The results revealed that the DBNs‐ALDH reinforced the anticorrosion performance of the EP coating. [ABSTRACT FROM AUTHOR]

The damage of a long tunnel is found in parts with an adverse geological structure zone under an earthquake. The phenomenon is normally the consequence of a non-uniform seismic load. Thus, to reveal the mechanism of the phenomenon, the dynamic response of the lining structure in a long tunnel passing through an adverse geological structure zone subjected to a non-uniform seismic load is mainly studied in this paper. Firstly, based on the random ground motion synthesis theory, the non-uniform ground motion acceleration–time history curves that reflect local site effects, such as traveling wave effects and attenuation effects, are generated. Secondly, the behavior of the tunnel with a different adverse geological structure zone (including different inclinations, thicknesses, and lithologies) under non-uniform seismic input is studied. Then, the impact of the different adverse geological structure zone on the internal force and safety factor of the tunnel lining is analyzed. Finally, the failure characteristics of the lining structure in the tunnel crossing through the adverse geological structure zone subjected to a non-uniform seismic load are revealed. The results show that the seismic dynamic responses significantly increase under non-uniform seismic input compared with the results under uniform seismic input, and the dynamic responses distribution along the tunnel axial is distinctly different under non-uniform seismic input. The inclination and thickness of the adverse geological structure zone have a significant influence on the internal force and safety factor of the tunnel lining, while the lithology mainly acts around the adverse geological structure zone. When the inclination angle of the adverse geological structure zone is 45°, a large number of compression-bending cracks appear in the entrance and exit sections of the tunnel, and the tunnel is in the most dangerous state. [ABSTRACT FROM AUTHOR]

Based on the strategy of regulating the constitutional liquation of segregation phases, Al-based anode materials with a high voltage in the neutral electrolyte are designed and prepared for the Al–air battery. According to the Ga–In–Sn ternary phase diagram, the liquid segregation phase is designed and constructed inside the Al anode to improve the comprehensive performance of Al anodes. By adjusting the content of Ga and In, the obtained anodes with various liquid phase content in the grain boundaries present different electrochemical properties. The open-circuit potential of the optimal quaternary anode reaches −1.626 V in 2 M NaCl solution. A series of analyses, including phase composition, microstructure, element distribution and thermodynamic properties, are employed to successfully reveal the presence of the low-melting-point segregation phases and the influence on the electrochemical characteristics of these Al anode materials. It is found that the liquid segregation phase formed by alloying elements, Ga, In, and Sn, can effectively activate the Al anode and contribute to the discharge process. Furthermore, the activation mechanism of the Al anode driven by the liquid segregation phase is proposed. [ABSTRACT FROM AUTHOR]

A novel three-dimensional sp 3 hybrid carbon allotrope, namely C mca-C16, is predicted through structure searching within density functional theory (DFT) calculations. The structural, electronic, relative formation enthalpy and mechanical properties including bulk, shear, Young's modulus, ideal strength and Vickers' hardness are systematically investigated. The obtained results demonstrated that C mca-C16 exhibiting excellent mechanical and dynamic stability. The calculations of ideal strength indicate that the failure mode occurs along the [100] direction, with the lowest peak stress of 80.8 GPa. The theoretical hardness of C mca-C16 is calculated to be 88.6 GPa, which is comparable to that lonsdaleite (90.5 GPa) and C14-carbon (89.7 GPa), but higher than most other known carbon phases. [Display omitted] • A novel orthorhombic carbon allotrope: C mca-C16 was uncovered. • C mca-C16 is more energetically favorable than bct-C4 and M-carbon. • The hardness of C mca-C16 is predicted to be 88.4 GPa. [ABSTRACT FROM AUTHOR]

Based on cascade utilization of full spectrum solar energy, a spectral splitting agriculture photovoltaic thermal hybrid system has been proposed in this study. The red and blue light is assigned to farmland for plant photosynthesis, while the photovoltaic active light is absorbed by solar cell for electricity generation, and the rest to thermal receiver for high temperature production. To maximize the power output of proposed system, redundant waste heat is recovered through ejector and converted into electricity in organic Rankine cycle subsequently. By such incorporation, the proposed system can not only increase the overall utilization efficiency of solar energy, but also achieve the cogeneration of crops and electricity on the same land. Energy, exergy, and economic analyses are performed to evaluate the performance of proposed system. Results show that the overall utilization efficiency of solar energy reaches 39.67 % with the highest losses of 79.65 MW in organic Rankine cycle. From the point view of exergy, photoelectric conversion in solar cell is responsible for the largest exergy destruction and finally the overall exergy efficiency of proposed system reaches 40.65 %, which is 16.13 % higher than that of equivalent agricultural and photovoltaic system with separate land use. [ABSTRACT FROM AUTHOR]

Cu-based quaternary chalcogenide compounds have been thermoelectric topic of interest among researchers, especially in recent years, due to their intrinsically low thermal conductivity. Recently plenty of work is done on thermoelectric properties of Cu2ZnSnSe4-based alloys emphasizing on importance of Cu2ZnSnSe4-based alloys in thermoelectric power generation. In this study, we report the effect of annealing temperature on microstructure and thermoelectric properties of Cu2.1Zn0.9SnSe4 alloys. Cu2.1Zn0.9SnSe4 compounds were synthesized by high-temperature melting followed by annealing at four different temperatures (600 °C, 650 °C, 700 °C and 725 °C). X-ray diffraction combined with Raman spectroscopy confirmed the presence of Cu2ZnSnSe4 phase along with ZnSe and CuSe secondary phases. The increased annealing temperature critically affected the microstructure of Cu2.1Zn0.9SnSe4 alloys. Successive increase in annealing temperature subsequently increases the average grain size from 7.3 for 600 sample to 12.1 μm for 725 °C sample by shifting grain size distribution toward higher range. Increased grain size results in reduced carrier scattering and decreases the electrical resistivity eventually improving power factor and maximum power factor of about 400 μWk−2 m−1 is obtained for 725 °C sample. Besides, the increased annealing temperature resulted in increased thermal conductivity attributing increased grain size resulting in low phonon scattering. 725 °C sample shows highest power factor and moderate thermal conductivity among all the samples which resulted in highest value of figure of merit for 725 °C sample of about 0.1 at 673 K. [ABSTRACT FROM AUTHOR]

The conventional signal processing based methods are difficult to achieve satisfactory results for rolling element bearings (REBs)' weak fault due to the serious influence of interference signal. Intelligent classification technology and the arising popular monitoring technology-performance evaluation assessment (PDA) are the research hotspots of fault diagnosis of REB in recent years, which could resolve the above problem to some extent. Especially the latter could reflect the operating status of the equipment more comprehensively. Effective feature extraction basing on signal processing methods and intelligent algorithm are the two key aspects for the above two technologies which will determine their effectiveness to great extent. Multifractal detrended fluctuation analyses (MDFA) is an effective non-stationary signal processing method which could reveal the multifractality buried in nonlinear and nonstationary vibration signals of REB, and continuous hidden markov model (CHMM) is a mature intelligent algorithm with solid theoretical basis and rich mathematical structure. So a diagnosis method basing on combination of MDFA with CHMM is proposed in the paper, and it could deal with both fault classification and PDA tasks for the diagnosis of REBs. Effectiveness of the proposed method is validated by two different diagnosis experiments, one for fault classification and another for lifecycle performance evaluation of REBs. Compared to state-of-the-art peer methods, the proposed method has the best performance when dealing with fault diagnosis tasks for REBs. [ABSTRACT FROM AUTHOR]

Comprehensive understanding for machinery health monitoring could be realized by multisource information. Nevertheless, effective fusion of faulty features extracted from multichannel sensors remains challenging in intelligent fault diagnostics. For this reason, coupled hidden Markov model (CHMM) is proposed in this work to efficiently fuse spectral coherence (SC) features extracted from multichannel sensors for improving the diagnosis performance of rolling element bearings (REBs). To this end, SC features extracted from multichannel vibration data of the REB under different operational conditions are fused by a multichain CHMM. Parameter estimation algorithms and probabilistic inference for the CHMM are also developed in the addressed fusion approach. The effectiveness of the proposed method is validated by two different diagnosis experiments, one for fault classification and another for lifecycle performance evaluation of REBs. Compared with the state-of-the-art peer methods, the proposed multichannel feature fusion method has the best performance when dealing with fault diagnosis tasks for REBs. [ABSTRACT FROM AUTHOR]

Dy/Y co-doped SrTiO3 ceramic composites with submicron A2Ti2O7 (A = Dy, Y) pyrochlore were in situ synthesized by a solid-state method. The microstructure of the A2Ti2O7 phase and its relationship with the thermoelectric properties of Sr0.9−xDyxY0.1TiO3 ceramics are studied. As the Dy content increases, the secondary phase content increases and the grain size slightly decreases from 1.03 to 0.77 μm; meanwhile, the grain size of the main phase also decreases. The highest power factor of 1034.5 μWK−2 m−1 at 569 K has been obtained for the x = 0.08 sample due to comparatively lower electrical resistivity. In addition, the introduction of Dy reduces the thermal conductivity dramatically by decreasing the grain size of the main phase, increasing the number of the second phase and enhancing the scattering of mass fluctuation. In the end, the zT> 0.20 is obtained within the range of size of 0.80–1.03 μm and the mass fraction of 4.91%–13.50% for the second phase. The maximum zT value of 0.22 has been obtained for the x = 0.08 sample with the second phase size and the mass fraction of 0.88 μm and 11.6%, respectively. Thus, heavy element doping and the second phase with the right grain size and proportion can result in high thermoelectric properties for SrTiO3 samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • The graphitization of the diamond (1 0 0) surface is elucidated by the first-principles calculation. • The chemisorption of Fe atoms varies the connections between the sixfold chair ring structures rather than breaking them. • The migration activation energy and movement direction are correlated with the anisotropy of the material removal rate. Studying diamond graphitization is a crucial issue in ultra-precision machining because it sheds light on the reason for material removal during polishing. The polishing disc made of cast iron is usually used to process diamonds, and a high-quality surface can be obtained. However, the graphitization mechanism induced by iron (Fe) is still obscure. This paper employs the density-functional theory (DFT) method to elucidate the mechanism by which Fe induces diamond graphitization. The results demonstrated that Fe atoms at the metastable adsorption sites (P3) on the surface could change some C–C interactions between layers. Notably, multiple Fe atoms at the P3 sites could alter the region of surface graphitization and the structural dissociation direction. The surface area close to Fe atoms became stable, while the surrounding surface areas were susceptible to oblique dissociation into graphite-like structures. Moreover, we speculated that the material removal rate was related to the moving activation energy of Fe atoms. Based on the charge-transfer and microstructural evolution, the phenomenon of Fe-atom-induced diamond graphitization was attributed to varying the connections between sixfold chair rings and promoting their weakening and dissociation rather than breaking the structure of sixfold chair rings. [ABSTRACT FROM AUTHOR]

Lead telluride (PbTe) is an excellent thermoelectric material in the intermediate temperature zone and has been applied to deep space exploration, waste heat recovery and other fields. However, the low thermoelectric conversion efficiency of the n-type PbTe alloys limits its applications. Here, the thermoelectric performances have been enhanced in n-type PbTe alloys through trace bismuth (Bi) and iodine (I) co-doping. The Pb1−xBixTe1−xIx (x = 0.00%, 0.05%, 0.10%, 0.20% and 0.50%) alloys are synthesized in the single phase compounds by a stepwise synthesis method. The carrier concentration has reached an optimal concentration range within the order of 1019 cm−3. The highest absolute Seebeck coefficient of 244 μV/K is obtained for 0.05% doped alloy at 730 K. The highest absolute Seebeck coefficient leads to high power factor for 0.05% doped, especially in low- and middle-temperature range. The highest power factor ∼25 μW K−2 cm−1 has been obtained at 329 K. Complex micro-scale grain boundaries and point defects strongly increase the phonon scattering and then lead to the lowest lattice thermal conductivity of 0.64 W mK−1 at 674 K for x = 0.50%, which is 26% lower than that of pristine PbTe. As a result, the highest figure of merit, zT ∼ 0.9 has been determined in 0.20% doped samples at 725 K. Moreover, the highest average figure of merit, zTave ∼ 0.7 has been achieved in 0.05% doped samples in the 323–723 K temperature range, which is about two or three times higher than reported for single Bi or I doped PbTe samples. [ABSTRACT FROM AUTHOR]

Sparse decomposition has excellent adaptability and high flexibility in describing arbitrary complex signals based on redundant and over-complete dictionary, thus having the advantage of being free from the limitations of traditional signal processing methods such as wavelet and fast Fourier transform being imposed by orthogonal basis. Sparse decomposition provides an effective approach for feature extraction of intricate vibration signals collected from rotating machinery. Self-learning over-complete dictionary and pre-defined over-complete dictionary are the two dictionary construction modes of sparse decomposition. Normally, the former mode owns the virtues of much more adaptive and flexible than the latter one, and several kinds of classical self-learning over-complete dictionary methods have been arising in recent years. K -means singular value decomposition is a classical self-learning over-complete dictionary method and has been used in image processing, speech processing, and vibration signal processing. However, K -means singular value decomposition has relative low reconstruction accuracy and poor stability to enhance the desired features. To overcome the above-mentioned shortcomings of K -means singular value decomposition, a new K -means singular value decomposition sparse representation method based on traditional K -means singular value decomposition method was proposed in this article, which uses the sparse adaptive matching pursuit algorithm and an iterative method based on the minimum similarity of atomic structure. The effectiveness and advantage of the proposed method were verified through simulation and experiment. [ABSTRACT FROM AUTHOR]

High thermoelectric figure of merits have been achieved in lead telluride (PbTe) alloys recently, which are beneficial for future thermoelectric applications. In this study, a PbTe-based thermoelectric module is constructed by eight pairs of p-type PbTe–8%SrTe and n-type PbTe 0.998 I 0.002 –3%Sb legs with initial sizes of 3 × 3 × 3 mm3. The relationship between multiple geometric parameters and performance of module has been studied by finite-element simulation. The maximum output power (P max) of 7.6 W and efficiency (η max) of 15.3% have been achieved at ΔT = 500 K for ideal contacted PbTe-based thermoelectric module. Contact resistance must exist in experimental thermoelectric module, so it has been considered in simulation about geometry optimization. The cross-sectional area ratio (A p /A n) and height (H) show strong dependent relationship to optimize module performance. The larger A p /A n and relatively lower H are propitious to enhance the output power. Moreover, the efficiency is improved at an optimum A p /A n and relatively higher H. In this PbTe-based module, the P max = 4 W is achieved at A p /A n = 1.78 and H = 0.65 mm, while η max = 14% is achieved at A p /A n = 1.64 and H = 13 mm under ΔT = 500 K. The P max and η max are 20% and 65% larger than those of initial design sizes. Thus, geometric structure modification is a good way to improve the performance of thermoelectric applications. • Cross-sectional ratio (A p / A n) and height (H) have strongly depended relationship. • Larger ratio of A p /A n and relatively lower H easily lead to higher output power. • Suitable ratio of A p /A n and relatively higher H can result to higher efficiency. • P and η of PbTe-based module are enhanced by 20% and 65% via geometry design. [ABSTRACT FROM AUTHOR]

Vibration signals are used to monitor the running state of mechanical equipment, but always suffer from a lot of noise in the acquisition process. In order to eliminate noise interference as much as possible, a multilevel residual convolution autoencoder network based noise learning method (LN-MRSCAE) is proposed in this paper. The LN-MRSCAE consists of a deep convolutional autoencoder network and multilevel residual, in which the learning noise module encodes and decodes the noise components, combining with a residual module to obtain the denoised signal. The multilevel residual structure is designed to address the gradient disappearance in network learning and improve the training speed. In specific, the noise learning replaces the traditional clean signal learning. Instead of learning the characteristics of the original clean signal, just learn the characteristics of the noise signal. The effectiveness of LN-MRSCAE network denoising is verified by classic analog signal and actual bearing vibration signals with different faults. The results show that the LN-MRSCAE model is superior to the latest models, and the noise component of the signal is obviously suppressed. [ABSTRACT FROM AUTHOR]

The vibration signal containing the fault feature is buried by the strong background noise usually (the noise is referring to the other signals not containing the fault feature in the general sense) when a fault arises in rotating machinery, so the collected vibration signal needs to be processed normally in order to get a correct diagnosis result. Sparse representation theory is a relatively new signal processing method and matching pursuit (MP) is the classical sparse representation method. However, in the traditional MP method only one kind of atom dictionary is constructed to match the fault feature hidden in the vibration signal, which will cause an unsatisfactory analysis result usually when several different kinds of components arise in the vibration signal synchronously. This paper proposes a novel fault feature strengthening method basing on MP to solve the above problem, and the proposed method constructs several different kinds of atom dictionary based on a multi feature pattern set to match the multi-components buried in the collected vibration signal of rotating machinery. Firstly, the effectiveness and advantages of the proposed method are verified by kinds of typical simulation signals of rotating machinery. Then the proposed method is extended to preprocess the vibration signals of bearing and gearbox, and the corresponding analysis results prove that the proposed method has obviously a better fault feature extraction effect on the vibration signal of rotating machinery than the traditional MP method, and the proposed method lays the foundation for further correct fault analysis. [ABSTRACT FROM AUTHOR]

Lead-free tin telluride (SnTe) has been viewed as one promising solid thermoelectric material for recovering waste heat in recent years. In this work, SnTe alloys doped with excessive In and Sb have been synthesized by melting, quenching and spark plasma sintering. The Seebeck coefficient has been enhanced by synergistic effect based on resonant levels and increased carrier effective mass especially at low and middle temperature range, and then, the power factor is enlarged. With the reduced electrical and lattice thermal conductivity via co-doping, the total thermal conductivity is decreased. Intrinsic point defect and more grain boundaries lead to reduction in the lattice thermal conductivity through the co-doping. In addition, as the doping level is near the solubility limit, the 200–600 nm, In-rich precipitations have been detected in Sn0.848Sb0.14In0.012Te alloy, which can further reduce the lattice thermal conductivity. Thus, the lowest lattice thermal conductivity of 0.96 W m−1 K−1 is obtained at 800 K. Finally, the maximum figure of merit zT of ~ 0.8 at 800 K has been obtained for Sn0.848Sb0.14In0.012Te alloy, and a relative high average zT of ~ 0.45 in 300–800 K is achieved due to the zT improvement in the low and middle temperature range which indicated that SnTe is a promising candidate for the thermoelectric application. [ABSTRACT FROM AUTHOR]

The vibration signals will take on cyclical characteristics when fault arises in the rolling element bearing, and a two-step blind source extraction (BSE) method for fault diagnosis of rolling element bearing is proposed in the paper using the above property. Firstly, calculate the theoretical basic cyclet of the target source fault signal, and the weighted separation matrix ŵ and desired source signal are obtained coarsely. Secondly, use ŵ as the initial weighted matrix and apply the fixed-point algorithm basing on high-order statistics on the observed signals, and much more perfect target source signal is got at last. The proposed method has the following advantages over other BSE method such as constrained independent component analysis (CICA) basing on the analyzed results of simulation and experiment: The fundamental period τ of the target source signal does not needed to be estimated accurately, and the reference signal also does not need to be constructed precisely. However, these two conditions are the necessary prerequisites of CICA. Besides, the proposed method also has the advantage of higher accuracy over the other recent BSE methods through comparison. [ABSTRACT FROM AUTHOR]

Abstract We attempt to develop an optimized metallized layer and evaluate the performance for a SnTe uni-leg thermoelectric module by finite-element simulation. The maximum conversion efficiencies of 3.0% and 0.7% have been achieved under ideal and rough contacted thermoelectric modules at ΔT = 600 K. The Ag metal is found to be the optimized metallized layer. The module with metallized Ag layer shows the lowest contact resistance and the best performance. The efficiency reaches about 60% of ideal contacted module. Following that, the pressure forced on module and the surface roughness between the electrode, metallized layer and thermoelectric material have been simulated. With the increase of surface roughness slope, the contact and inner resistances of the thermoelectric module are decreased, and the voltage, maximum output power and efficiency are increased. When the average surface roughness slope is over 0.8, the efficiency reaches 90% of the ideal contacted module. The contact and inner resistances obviously decrease with increasing pressure, while the voltage, maximum output power and efficiency are enhanced. The greater than 90% efficiency of an ideal contacted module is achieved when the pressure is beyond 100 kPa. These simulated results will be beneficial for the fabrication of SnTe-based thermoelectric modules. Highlights • The SnTe uni-leg thermoelectric module are designed and studied. • Highest efficiencies of 3%, 0.7% are found for ideal and rough contacted modules. • Ag metal is the optimized metallized layer for SnTe uni-leg thermoelectric module. • Optimized roughness slope and pressure lead to 90% of maximum of ideal efficiency. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • N atoms can adsorb on the fully H-Ter-D (0 0 1) surface with E ad = 3.47 eV. • N atoms can adsorb on the 1ORS slab and abstract the H atom nearby. • N atoms can easily migrate along the dimer chain direction on the 2ORS-CO slab. • A deposited C atom can easily migrate in the region of a nitrogen atom adsorbed. • N atoms adsorbed can be abstracted by the other deposited N atoms. Abstract In this paper, the adsorption and migration behaviors of nitrogen (N) atoms on the hydrogen -terminated diamond (0 0 1) surface [H-Ter-D (0 0 1) surface] were investigated. The adsorption energy, the electron charge and the magnetic moment were calculated through first principles methods. The investigation results show that on the fully H-Ter-D (0 0 1) surface, all surface C atoms have saturated bonds. However, the N atom can abstract the H atom from a surface carbon atom nearby or lead to the bond breaking of the dimer carbon atoms to form bonds with the surface carbon atoms. The maximum energy of adsorption reaches to 3.47 eV, corresponding to a stable configuration structure. The charge analysis and the density of state analysis further reveal that the N atom adsorbed has unpaired electrons, which provides the opportunity for adsorption of CH radicals. On the H-Ter-D (0 0 1) surface with one open radical site (1ORS) slab, the N atom can abstract the H atom from a surface carbon atom nearby and bond with the dimer carbon atoms. The adsorption energy rises to 4.85 eV. On the H-Ter-D (0 0 1) surface with the 2ORS slab, the activation energy for a N atom to migrate along the dimer chain to the next dimer is 1.31 eV. Moreover, the adsorption of the N atom on the 1ORS surface promotes the adsorption of a C atom nearby and improves the ability of C atom migration, which is beneficial for the growth of the diamond grains. According to the charge transform analysis, the electronegativity of N atoms plays an important role in their adsorption behaviors. In addition, when the N atom has been adsorbed on the H-Ter-D (0 0 1) surface, it could still be abstracted by the other deposited N atoms; this phenomenon may be the reason for a low deposition efficiency of N atoms in the N-doped diamond films. [ABSTRACT FROM AUTHOR]

High figures of merit of n-type Pb1−xBixTe alloys have been achieved by rapid synthesis at low temperature. The effects of Bi dopant and microwave hydrothermal technology on microstructure and thermoelectric performance have been studied. The solid solubility limit of Bi in PbTe is between x = 0.02 and 0.03. Homogenous nanopowders of about 70 nm have been synthesized by the microwave hydrothermal method. When followed by hot pressing, sub-microscale grain sizes are also formed for Pb1−xBixTe alloys. With increase in Bi, the carrier concentration is improved within the solubility limit. This leads to low electrical resistivity and higher power factor at high temperature. A higher power factor of 8.5 μW cm−1 K−2 is obtained for x = 0.02 sample at 623 K. In addition, the introduction of Bi effectively prohibits the p–n transition and bipolar thermal conductivity of pristine PbTe. Thus, a low lattice thermal conductivity of 0.68 W m−1 K−1 is achieved at 673 K, combining scattering of alloys, grain boundaries, dislocations and defects. As a result, the highest peak figure of merit, i.e., zT = 0.62 at 673 K is achieved for Pb0.98Bi0.02Te sample, which is comparable with that of Bi-doped PbTe alloys synthesized by the conventional melting method. Thus, the right synthesis conditions of the microwave hydrothermal method can rapidly result in thermoelectric materials with comparable figures of merit. [ABSTRACT FROM AUTHOR]

Wave-in-deck loads due to 45 ° oblique transient focus wave groups are investigated using model-scale experiments and computational fluid dynamics simulations with emphasis on comparing with head-on wave impacts for a solid cuboid deck model without and with an I-beam grillage beneath. After validation with experiments, numerical results are extended to consider wave-in-deck loads with 22. 5 ° and 67. 5 ° oblique wave directions. Generally, the head-on wave impacts cause larger longitudinal forces on the deck whereas the oblique cases result in larger downward vertical forces. For the deck with grillage case, Santo et al. (2020) and Wang et al. (2022) show that successive large spikes are observed in the force time series of head-on wave impact due to entrapped air-pocket effects in the grillage. However, here it is found that the large spikes are absent in the force time series for the oblique wave impacts and the patterns of forces are similar to the deck without grillage with rather small or no spikes in the force time series. Interrogation of the numerical flowfield reveals evidence that the asynchronous and less effective air entrapment in the grillage for the oblique cases are responsible for the difference. The maximum positive pressure on the underside of the deck is found to be much larger for the deck with grillage than without due to local slamming of jets formed in the grillage. [ABSTRACT FROM AUTHOR]

A high-performance flexible Al-air battery with liquid alloy-activated anode system is developed for wearable electronics. By constructing activation interface composed of Ga–In liquid particles (GILPs) on the Al anode, the electrochemical performance of the flexible Al-air battery is enhanced. This work validated that GILPs can not only serve as active sites for the oxidation reaction of Al atoms to avoid the generation of passivation film, but also can further expand the active Al range and improve overall performance of the battery. These GILPs also exhibit satisfying electrical conductivity to reduce the mechanical loss of the Al anode during discharge, resulting in a high energy utilization of the battery. The Al-air battery with 150 μg cm−2 GILPs displays remarkable capacities of 2345 mA h g−1 at the current density of 1 mA cm−2, 1.6 times higher than that of Al-air battery without GILPs loading. Amplification experiment of Al anodes' thickness and area are performed. The results indicate that the lifetime of battery can be extended by scaling up thickness of Al anode, and overall battery amplification efficiency is greater than 93.5%. This study opens up a prospect for the application of Al-air batteries in the field of flexible wearable power supply devices. [Display omitted] • A liquid alloy activated high-performance flexible Al-air battery was developed. • Liquid alloy can effectively improve energy density and reduce mechanical losses. • The optimal battery displays remarkable capacity of as high as 2481 mAhg−1. • The battery lifetime can reach 1.67 times that of original one. • The power and lifetime of the flexible battery are adjustable to suit application. [ABSTRACT FROM AUTHOR]

Shield tunnels that cross soft and hard mutation strata will experience severe longitudinal uneven settlement, which results in local damage to the shield tunnel. Previous studies on the longitudinal mechanical properties of shield tunnels generally assumed that the strata were homogeneous or level-layered and that the lining segment ring was uniform and ignored the shield tunnel's discontinuity and the inhomogeneity in the strata adjacent to the shield tunnel. Therefore, a three-dimensional (3D) longitudinal refined numerical calculation model of a shield tunnel is developed under complex geological conditions, which realistically considers the effects of a staggered assembly of a shield tunnel, longitudinal and circumferential bolts between segments, and the interface between the strata and tunnel structure. An improved Timoshenko beam theory method that has been validated by a model test in the literature is adopted to verify the numerical calculation model's reliability and applicability and to highlight its advantages. Then, a study is conducted to analyze the longitudinal mechanical properties of shield tunnels that cross soft and hard mutation strata through this numerical calculation model. The influence law for strata on the longitudinal mechanical properties of the shield tunnel is highlighted by comparisons with another numerical calculation model with simplified strata, which includes the longitudinal uneven settlement and local deformation of the shield tunnel, the opening and dislocation of segment rings, deformation, and yield state of the longitudinal and circumferential bolts. Furthermore, a parametric study is further presented to analyze the influence of the elastic modulus difference between soft and hard strata on the longitudinal mechanical properties of the shield tunnel. An empirical formula is introduced to calculate the maximum opening and dislocation of the segment rings. The longitudinal uneven settlement of the shield tunnel becomes more significant and concentrated as the elastic modulus difference increases, which increases the local deformation and longitudinal internal force in the shield tunnel. Similarly, the deformation and internal force of bolts and the interface increase in the longitudinal direction. Significant differences in the elastic modulus between the soft and hard strata will likely induce severe deformation damage and bolt failure into the shield tunnel. [ABSTRACT FROM AUTHOR]

The near-stoichiometric LiNbO 3 crystal (SLN) with dimension of Φ25 × 45 mm 3 has been successfully grown from Li-rich solutions by the Czochralski method. The results of X-ray rocking curve measurement indicate that the as-grown SLN crystal has a relatively high crystallinity. The mechanical properties of SLN crystal were determined by nanoindentation method. The hardness and elastic modulus values obtained revealed higher values for (300) plane of SLN crystal (10.02 and 225.6 GPa) compared to the (600) plane of SLN crystal (7.09 and 202.8 GPa). Different hardness and elastic modulus values for different planes suggest anisotropic character of mechanical properties in SLN crystals. The distribution characteristic of residual stress in SLN crystal along the optical axis is analyzed by means of photoelasticity effect. [ABSTRACT FROM AUTHOR]

Highly ordered mesoporous materials synthesized by a nanocasting method offer vast opportunities in catalytic applications. However, considerable debates remain as to the mechanism by which the mesoporous structure results in enhanced performance. We demonstrate new insights into the role of ordered mesoporous metal oxides in the catalytic oxidation reaction by preparing nickel (II) oxide (NiO) rather than a multiple valence compound such as Co 3 O 4 as model catalyst. Mesoporous NiO using KIT-6 as a template (m-NiO-k) achieved total formaldehyde (HCHO) mineralization at 90 °C using oxygen (O 2 ) as oxidant, while bulk NiO (b-NiO-c) oxidized HCHO completely at 170 °C. Moreover, using ozone (O 3 ) as oxidant, m-NiO-k attained increased HCHO conversion by ∼34% with a twofold increase in CO 2 selectivity and a 100% O 3 decomposition rate. We conclude that the surface sodium functionalization of m-NiO significantly promotes the total oxidation of HCHO with O 2 , likely via contribute to hydroxyl regeneration during reaction. Furthermore, the extra active oxygen species and undercoordinated NiO on the mesoporous surface owing to the properties of mesoporous structures contribute almost exclusively to the high activity and selectivity in the simultaneous catalytic removal of HCHO and O 3 , which are also involved in the further enhanced activity for HCHO oxidation using m-NiO with O 2 . These findings provide additional new insight into engineering efficient mesoporous metal oxides for VOCs catalysis under mild condition. Furthermore, they provide an innovative perspective on optimizing other reactions employing nanocast mesoporous catalysts. [ABSTRACT FROM AUTHOR]

The bispectrum of rolling element bearing compound faults contains abundant fault characteristic information, and how to extract the fault feature effectively is a key problem. The fault diagnosis method of rolling element bearing compound faults based on Sparse No-Negative Matrix Factorization (SNMF)-Support Vector Data Description (SVDD) is proposed in the paper. The figure handling method SNMF is used firstly in fault feature extraction of the bispectrums of rolling element bearing different kinds of compound faults and the sparse coefficient matrices of the bispectrums are obtained. The sparse coefficient matrices are used as training and test input vectors of SVDD. At last, the three kinds of rolling element bearing compound faults (inner race outer race compound faults, outer race rolling element compound faults and inner race outer race rolling element compound faults) are classified correctly. In order to verify the advantages of the proposed method, the diagnosis results of the same three kinds of rolling element bearing compound faults based on No-Negative Matrix Factorization (NMF)-SVDD is used as comparison. The proposed method provides a new idea for fault diagnosis of rolling element bearing compound faults. [ABSTRACT FROM AUTHOR]

[Display omitted] • The initial reason for Fe-induced graphitization on the diamond (1 1 0) surface was elucidated by the first-principles calculation. • The charge transfer of Fe adatoms reduces the potential energy barrier between diamond and graphite. • The Fe adatom can weaken interlayer C C bonds and change the dissociation direction of the diamond (1 1 0) surface. Understanding the diamond graphitization mechanism is an essential subject in manufacturing research since it helps elucidate the reason for the material removal. Our work addressed the mechanism of Fe-induced graphitization of diamond (1 1 0) surfaces (Dia-(1 1 0)-Surf) by first-principles calculations. The results pointed out that Fe atoms adsorbed at hollow sites could acquire the most stable configuration on the Dia-(1 1 0)-Surf. Meanwhile, the Fe adatom could change interlayer binding energies of C C bonds of various layered. As the amount of Fe atoms increased, the weakening/enhancement effect of C C bonds tended to be apparent. Interestingly, Fe adatoms not only changed interlayer binding energies of C C nearby but also affected the dissociation direction of the surface microstructure. The weakened C C bonds could provoke the flattening of the sixfold chair ring structure of C atoms. The extension direction of the sixfold chair ring structure changed from horizontal to oblique, resulting in eliminating lateral compressive stress. It might be the origin of the Fe-induced graphitization of Dia-(1 1 0)- Surf. Moreover, the migration behaviors of the Fe atom have been studied. It could be inferred that the migration activation energy and movement direction of Fe adatoms were associated with the material removal rate. [ABSTRACT FROM AUTHOR]

Tuning the d -band center and surface formation energy of Ni-based catalysts via Cu for efficient and stable catalytic hydrogenation of dioctyl phthalate. [Display omitted] • A bimetallic strategy is developed built on confinement effect. • Ni 2.5 Cu 0.5 Al 1 catalyst exhibits excellent activity and stability under harsh conditions. • Activity and stability are improved by reducing the surface formation energy and d -band center with Cu. Hydrogenation of dioctyl phthalate (DOP) is an effective strategy to synthesize cyclohexane-1,2-dioctyl phthalate (CDP), an environmentally friendly plasticizer. Many catalysts have already been developed to achieve the hydrogenation of DOP. However, due to the stability of their aromatic rings, the high costs of noble metal catalysts, and the harsh reaction conditions, the fabrication of non-noble metal catalysts with high activity and stability is still challenging. In this work, we report a bimetallic strategy built on the confinement effect to prepare a Ni 2.5 Cu 0.5 Al 1 bimetallic catalyst using Ni-Cu hydrotalcite as the precursor. Results show that DOP conversion and selectivity of CDP could both reach 99%; also, the suggested bimetallic catalyst exhibits excellent stability under harsh reaction conditions, e.g., the catalyst can be recycled up to 9 times with no change in conversion and selectivity. Certain characterizations and theoretical calculations show that introduction of an appropriate amount of Cu can reduce the surface formation energy and d -band center, which can simultaneously improve the activity and stability of the Ni-based catalysts. Therefore, the proposed Ni-Cu bimetallic catalyst is an attractive option for the synthesis of environmentally friendly plasticizers by DOP hydrogenation. [ABSTRACT FROM AUTHOR]

Constructing membrane with good chlorine resistance and antifouling properties is considered to be important challenges confronting membrane applications. In this study, a composite nanofiltration (NF) membrane (β-CD x/y /PES) was prepared by interfacial polymerization using beta cyclodextrin (β-CD) monomers. Subsequently, the β-CD-based (AZ-β-CD x/y /PES) membrane was prepared by assembling azobenzene labeled zwitterions into the hydrophobic internal cavity of β-CD via host-guest interaction. The optimized membrane exhibited slight change in water flux and rejection under chlorine environment. The AZ-β-CD x/y /PES membrane also displayed an evidently lower loss in water flux in the antifouling test in comparison with the β-CD x/y /PES membrane. More interestingly, the trans azo groups in azobenzene labeled zwitterions can turn into the cis isomers as the visible light irradiation converted to the UV light irradiation, breaking the interaction between azobenzene labeled zwitterions and β-CD. Hence, the contaminants upon the membrane surface can be simply eliminated by water washing under UV light irradiation. The antifouling membrane can be regenerated via immersing the reacquired β-CD 2/10 /PES membrane into fresh azobenzene labeled zwitterions solution again. [Display omitted] • Chlorine-resistant membrane was prepared by using β-CD monomers. • The composite nanofiltration membrane shows good antifouling properties. • The fouled membrane can be regenerated via regulating the light irradiation. [ABSTRACT FROM AUTHOR]

The structural, electronic and mechanical properties (elastic, ideal strength and hardness) of two novel superhard boron-carbon-nitride allotropies named as o I m12-BCN and o P m12-BCN were investigated by first-principles calculations. Phonon dispersion calculations indicate that o I m12-BCN and o P m12-BCN are dynamically stable at ambient condition. The results show that o I m12-BCN is more energetically favorable than o P m12-BCN as well as most of the reported BCN compounds. The strength calculations reveal that the failure mode in o I m12-BCN is dominated by the shear type, and the (010)[001] direction is the weakest one with the lowest peak shear stress of 53.1 GPa. In o P m12-BCN, the failure mode is dominated by the shear type, and the (100)[010] direction is the weakest one. Theoretical hardness of o I m12-BCN (74.7 GPa) is evidently greater than that of o P m12-BCN (70.6 GPa), bc-BC 4 N (67.7 GPa), c-BN (66.4 GPa) and most of the reported BCN phases. The results imply that o I m12-BCN and o P m12-BCN are potential superhard materials. [Display omitted] • Two orthorhombic novel superhard boron-carbon-nitride allotropies o I m12-BCN and o P m12-BCN were uncovered. • o I m12-BCN is more energetically favorable than o P m12-BCN as well as most of the reported BCN compounds. • The hardness of o I m12-BCN and o P m12-BCN is predicted to be 74.7 and 70.6 GPa. [ABSTRACT FROM AUTHOR]

Al–Ga based alloys are important on-line hydrogen supply materials under harsh working conditions. Up to now, the activation mechanism is still unclear, especially the reason why In or Sn is indispensable to the alloys' performance is unknown. Here, we elaborately designed and implemented the simulation and validation experiments to unveil the role of indium and tin in the alloys. In simulation experiments, we conducted the penetration of liquid metals (LMs) into Al sheets to analyze its influence on Al's microstructure and the effects of In or Sn on Ga's distribution. We found that the activation effects of In and Sn are different. Subsequently, the validation experiments confirmed the above conclusion that In favors inducing deeper and wider cracks inside the alloy compared with Sn, thus making the alloy easier to break during hydrolysis and ensuring higher yields. Moreover, we found that Sn facilitated the reaction rate, which was explained by experiments and the theoretical calculation. Finally, a novel Al matrix embrittlement mechanism based on low-melting-point phases was proposed for Al–Ga based alloys, which provided a reference for the interpretation of material properties and precise material design. In addition, we gave suggestions for sample selection in actual working conditions. [Display omitted] • Improved mechanism is proposed to guide the application of Al alloys in H 2 supply. • Penetration simulation experiments were used to explored the role of In and Sn. • In and Sn can enhance Al alloys' performance through Al matrix embrittlement. • In and Sn's different effect on Ga's distribution affects Al alloys' performance. • The law that In favors H 2 yield while Sn favors reaction rate is confirmed. [ABSTRACT FROM AUTHOR]

Antifouling properties are considered to be crucial parameter to polyamide (PA) composite nanofiltration (NF) membranes for practical applications. In this study, an antifouling material, surface zwitterionization of Metal-organic frameworks (Z-MIL-101 (Cr)) was firstly prepared by decorating zwitterionic polymer onto the MOFs surface. Subsequently, a novel type of MOFs-based hybrid membranes were fabricated via mixing the Z-MIL-101 (Cr) nanoparticle with the organic matrix by interfacial polymerization technique. The most optimal hybrid membrane had a high water permeation of 26 L m−2 h−1 bar−1, which was 2.1 times higher than that pristine PA membrane, while the retention for Na 2 SO 4 was still kept at a considerably high value of 93%. The significant increased water flue can attribute to the existence of water channels generated by the Z-MIL-101 (Cr). More important, the antifouling property of the hybrid membrane was much better than that pristine PA, which was due to the formation of superhydrophilic liquid layer surrounding the zwitterionic groups. The combination of the micropore structure of the MOFs and the excellent antifouling properties of the decorated zwitterionic polymer effectively improved separation performances and antifouling ability, which makes these hybrid membranes promising for water purification. [Display omitted] • Zwitterionic metal-organic frameworks (Z-MIL-101 (Cr)) were prepared. • Z-MIL-101 (Cr)-based hybrid membranes were fabricated via interfacial synthesis. • The hybrid membranes show high water permeation of 26 L m−2 h−1 bar−1. • The antifouling ability of the hybrid membranes was significantly enhanced. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mechanism of diamond graphitization induced by tungsten is revealed by the DFT method. • The W adatoms of the fcc and hcp sites have different contributions to the surface carbon atoms separation. • The graphitization results from the chemical activation of W atoms, diamond structure contraction and the W-C bond pulling force. In the ultra-precision machining field, tungsten (W) is a promising material as a polishing disc for machining diamond, which is easier to obtain high-quality diamond surfaces than cast iron. The removal mechanism of the diamond during high-speed polishing is considered surface graphitization. In this work, the diamond graphitization mechanism induced by tungsten is revealed by the density functional theory (DFT). The results show that the W adatoms at the fcc sites can activate the interlayer C-C bonds, causing the surface carbon atoms to separate. Notably, the electron transfer of W atoms and the structure contraction of the diamond surface cause the graphitization. Moreover, the movement of W adatoms intensifies the diamond surface structure transformation and graphitization process. It is worth noting that the W adatoms of the fcc and hcp sites have different contributions to the surface carbon atom separation during the interfacial sliding process. When the W atoms cross the hcp sites, the pulling force of the W-C bonds promotes the reconfiguration of the separated surface carbon atoms. The diamond-to-graphite transition is attributed to catalyst activation by W adatoms, diamond surface structure contraction, and mechanical tensile stress by the W-C bonds. [ABSTRACT FROM AUTHOR]

Various two-dimensional (2D) structures cause different catalytic anisotropy based on the stack layers in Li-oxygen batteries (LOBs). Clarify the key factor for catalytic performance of 2D materials in LOBs is necessary. In this study, 2D structured Bi 2 Te 3 with five Te-Bi atom layers in its stack layers is applied as the cathode catalyst for LOBs. Hexagonal nanodisks and roller-like nanoparticles are prepared for exposed controlling crystal plane by simple one-step hydrothermal method. It reveals the stack surface (001) plane can provide outstanding catalytic capability with high conductivity after the adsorption of discharge products and efficient pathway for the conversion from LiO 2 to Li 2 O 2 and prevent the formation of by-products. As consequence, a superior specific capacity of 21,172 mAh g−1 and high cycling stability of 188 cycles at 500 mA g−1 are achieved. The corresponding catalytic mechanism of Bi 2 Te 3 mainly originates from its stack surface derived homogenous electronic state and high conductivity. [Display omitted] • Bi 2 Te 3 with exposed 2D surface plane exhibits excellent catalytic activity in LOBs. • The superior catalytic capability of Bi 2 Te 3 originates from 2D surface (001) plane. • Side edge planes of 2D materials contribute to the formation of side products. [ABSTRACT FROM AUTHOR]

CO 2 is the primary contributor to greenhouse gas that causes rapid global warming. CO 2 capture, utilization, and storage (CCUS) is a crucial technology for CO 2 reduction, typically, CO 2 hydrates form at pressures and temperatures greater than 3 MPa and lower than 10 °C. These non-harsh environmental conditions determine the value of hydrate-based CO 2 sequestration technology, which can be used as a potential effective sequestration measure. In addition, hydrates have the advantages of rapid formation kinetics, high stability, and a low probability of gas leakage; therefore, they can be used to sequester CO 2 in the near future. In this review, we summarize the development status and existing problems of various hydrate-based CO 2 sequestration methods and analyze the mechanisms, influencing factors, and appropriate sequestration locations. The paper focuses on the CO 2 replacement reaction of CH 4 hydrates technology. The feasibility of this method is discussed in terms of thermodynamics and kinetics, the mechanism and influencing factors of the replacement process are analyzed, and various methods to improve the replacement efficiency are illustrated, including the temperature and pressure conditions, the injection phase state of CO 2 , the use of additives, and the assistance of other gases (N 2 and H 2). Next, the method of direct injection of CO 2 into marine sediments to form hydrates for sequestration is discussed. We also generalize appropriate sequestration locations and summarize experimental and simulation studies on CO 2 sequestration in marine sediments, including the technical feasibility, sequestration mechanism, and influencing factors. In addition, the hydrate cap is also discussed. Finally, we briefly introduce a hydrate-based CO 2 sequestration method for reusing depleted deposits. This review paper can provide insights for future research and may help accelerate the field application of the hydrate method for CO 2 sequestration technology. • Hydrate-based CO 2 sequestration methods were summarized. • Suitable conditions and mechanisms for CO 2 hydrate sequestration were identified. • Sealing effect of CO 2 hydrate cap to prevent leakage was studied. • Limitations and countermeasures of proposed method were discussed. [ABSTRACT FROM AUTHOR]

Wave impacts on an elevated solid deck due to transient focused wave groups are studied numerically. Previously reported experiments with and without an I-beam grillage beneath the deck by Santo et al. (2020) are reproduced successfully in a three-dimensional numerical wave tank based on a two-phase Navier–Stokes solver. The impact loads on the solid deck are relatively simple. The three-dimensional horizontal force, characterised by a single peak in time, is close to two-dimensional, whereas the vertical force consists of upward force and downward suction force. The downward suction force is related to triangularisation of the wetted area underneath the deck and dominated by the added mass effect, which is a three-dimensional effect and therefore any two-dimensional simulation will overpredict the strongly three-dimensional process and the vertical impact loads. The wave impact loads on the solid deck with a grillage are more complicated, with successive force spikes observed for both the horizontal and vertical loads. The significance of entrapped air pockets in the grillage to global wave impact loads is ascertained through interrogating flow field of numerical experiments. It is found that large upward vertical impulsive forces are caused by high local pressures when entrapped down-wave air-pockets are formed, while large downward suction forces are resulted from both high-frequency up-wave air-pocket effect and the low-frequency added mass effect. Large horizontal impulsive forces are due to the combined effects of the down-wave air-pocket and the upward jetting motion of the wave crests. The entrapped air-pocket effects are found to be more important for vertical than horizontal forces. [ABSTRACT FROM AUTHOR]

It is an important topic in the manufacturing research field to understand the mechanisms for the wear of diamond surfaces. The density functional theory (DFT) methods have served as useful tools for studying chemical reaction mechanisms in processing. In this work, we studied the changes in the diamond structure during the interface contact between the iron and diamond. The iron-diamond contact area is simplified to different coverage rates of Fe atom, corresponding to different numbers of adatom. With the different numbers of the Fe adatoms, the interlayer C C bonds have different changes. Below the Fe adatom region, the interlayer C C bonds are strengthened, inhibiting the graphitization. It is noteworthy that the C C bonds became significantly weakened or even broken at the boundary of the interface contact. Moreover, the interface sliding simulation verifies that the graphitization preferentially occurs at the edge of the interface between iron and diamond. The actual cause of graphitization is the synergistic effect of the charge transfer of the Fe C bonds and the asymmetric contraction and stretching on the diamond surface. Our work provides a theoretical basis for suppressing excessive diamond tool wear and polishing the diamond surfaces. [Display omitted] • The graphitization mechanism of the interface between iron and diamond was concluded. • The graphitization preferentially occurs at the edge of the interface. • The charge transfer of the Fe C bonds and the asymmetric surface contraction and stretching are the causes of graphitization. [ABSTRACT FROM AUTHOR]

Despite the fact that a number of research efforts in the area of Industrial Wireless Sensor Networks (IWSNs) exist, there is a lack of really practical IWSN implementations, deployments, and in-field applications. This paper presents the design and implementation of an IWSN for welder machine systems, called WirelessCAN which is based on WirelessHART to replace wired CAN fieldbus. Although the implementation and challenges are application-specific, we believe that the problems we encountered will be faced by many IWSN designers. In this paper, selected challenges exposed in our implementation and the potential solutions are introduced, which have not been addressed previously. Specifically, communication resource constraint, real-time rescheduling, integrated knowledge for IWSN applications, centralized control architecture, reliable and immediate message delivery for human and equipment safety, and differential QoS requirements are discussed in detail and in depth. The goal of this paper is to make the design and implementation of IWSNs more efficient and applicable. [ABSTRACT FROM AUTHOR]

In this paper, we propose a heterogeneousmaterial for bulk thermoelectrics.By varying the quenching time of Na doped PbTe, followed by hot pressing,we synthesized heterogeneous nanocomposites, a mixture of nanodotnanocomposites and nanograined nanocomposites. It is well-known thatby putting excess amounts of Na (i.e., exceeding the solubility limit)into PbTe, nanodots with sizes as small as a few nanometers can beformed. Nanograined regions with an average grain size of ca. 10 nmare observed only in materials synthesized with an extremely low quenchingrate, which was achieved by using a quenching media of iced salt waterand cold water. Dimensionless thermoelectric figures of merit, zT, of those heterogeneous nanocomposites exhibited a zTaround 2.0 at 773 K, which is a 25% increase comparedto zTof a homogeneous nanodot nanocomposite withthe largest quenching time in our experiment, i.e. furnace cooled.The power factor increase is 5%, and the thermal conductivity reductionis 15%; thus, zTincrease mainly comes from the thermalconductivity reduction. [ABSTRACT FROM AUTHOR]

Abstract: When early weak fault emerges in rolling bearing the fault feature is too weak to extract using the traditional fault diagnosis methods such as Fast Fourier Transform (FFT) and envelope demodulation. The tunable Q-factor wavelet transform (TQWT) is the improvement of traditional one single Q-factor wavelet transform, and it is very fit for separating the low Q-factor transient impact component from the high Q-factor sustained oscillation components when fault emerges in rolling bearing. However, it is hard to extract the rolling bearing’ early weak fault feature perfectly using the TQWT directly. Ensemble empirical mode decomposition (EEMD) is the improvement of empirical mode decomposition (EMD) which not only has the virtue of self-adaptability of EMD but also overcomes the mode mixing problem of EMD. The original signal of rolling bearing’ early weak fault is decomposed by EEMD and several intrinsic mode functions (IMFs) are obtained. Then the IMF with biggest kurtosis index value is selected and handled by the TQWT subsequently. At last, the envelope demodulation method is applied on the low Q-factor transient impact component and satisfactory extraction result is obtained. [Copyright &y& Elsevier]