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The electrochemical reduction of CO2 to produce high-value multicarbon products represents a challenging yet highly desirable process, particularly due to the inefficient C–C coupling observed in current electrocatalysts. In this study, Cu2+ and Co2+ were introduced into ZIF-8 as precursors to synthesize a series of Co- and CuCo-doped carbon nanostructure materials with varying Co-to-Cu ratios. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) analyses confirmed the successful doping of metal Co in the form of Co–Nx, while Cu was partly doped as nanoparticles attached to the carbon substrate surface and partly as single atoms forming Cu–Nx. Transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses revealed uniform distribution of elemental Co and Cu on the carbon substrate, with Cu loaded as nanocluster on the surface. Linear sweep voltammetry tests indicated that Cu/CoCu-Nx-C composites exhibited enhanced reactivity toward CO2 reduction compared to other samples. At −0.19 V (vs RHE), the Faradaic efficiencies (FEs %) of C2H4, C2H6, CH4, CO, and H2 over Cu/CoCu-Nx-C were 29.7, 8.6, 20.2, 9.8, and 31.5%, respectively. The influence of Co and Cu doping modes on the selectivity of electrocatalytic reduction products was investigated. Results showed that Cu/CoCu-Nx-C exhibited a higher FE of C2 compared to Cu/Cu–Nx-C, with nearly 10 times higher C2 current density. Mechanistic insights from acid-etching experiments and XPS revealed a synergistic interaction between metallic Co and Cu, promoting the generation of multicarbon products. Co–Nx improved *CO coverage, facilitating subsequent C–C coupling on neighboring Cu–Nx. Additionally, CH4 production was attributed to the (111) crystalline facets in the Cu nanocluster and isolated Cu–Nx. Overall, this research provides an important understanding of the creation of straightforward and effective catalysts for the reduction of CO2. It holds considerable potential for the production of hydrocarbons using carbon dioxide. [ABSTRACT FROM AUTHOR]

This paper proposes a novel on-line rotor system condition monitoring approach using nonlinear data-driven modelling and model frequency analysis. First, the dynamic process model of the vibration transmission path between the vibration measurement points of two fulcrum structures is established by utilizing nonlinear data-driven modelling. Then, the unique frequency properties are extracted from the established model to reveal, in real time, the health condition of the rotor system. Finally, using the frequency properties as features, the unsupervised learning technology is applied to the on-line monitoring of the rotor system. Compared to conventional condition monitoring methods, the proposed approach can output an early warning 26 min before a shaft fracture occurs, without generating false alarms. Consequently, this approach can greatly enhance diagnostic accuracy, demonstrating its potential to contribute to the advancement of rotor system condition monitoring techniques. [ABSTRACT FROM AUTHOR]

The squeeze film damper (SFD) is proven to be highly effective in mitigating rotor vibration as it traverses the critical speed, thus making it extensively utilized in the aeroengine domain. In this paper, we investigate the stiffness and damping of SFD using the Reynolds equation and neural network models. Our specific focus includes examining the structural and operating parameters of SFDs, such as clearance, feed pressure of oil, rotor whirl, and rotational speed. Firstly, the pressure distribution analytical model of the oil film inside the SFD based on the hydrodynamic lubrication theory is established, as described by the Reynolds equation. It obtained oil film forces, pressure, stiffness, and damping values under various sets of structural, lubrication, and operating parameters, including length, clearance, boundary pressure at both sides, rotational speed, and whirling motion, by applying difference computations to the Reynolds equation. Secondly, according to the significant analyses of the obtained oil film stiffness and damping, the following three parameters of the most significance are found: clearance, rotational speed, and rotor whirl. Furthermore, neural network models, including GA-BP and decision tree models, are established based on the obtained results of difference computation. The numerical simulation and calculation of these models are then applied to show their validity with all given parameters and the three significant parameters separately as two sets of model input. Regardless of either set of model inputs, these established neural network models are capable of predicting the nonlinear stiffness and damping of the oil film inside an SFD. These sensitive parameters merely require measurement, followed by the utilization of a neural network to predict stiffness and damping instead of the Reynolds equation. This process serves structural enhancement, facilitates parameter optimization in SFDs, and provides crucial support for refining the design parameters of SFDs. [ABSTRACT FROM AUTHOR]

The rotor system design is gradually becoming lighter as the thrust-weight ratio of the new generation of aeroengines improves, making the power turbine rotor structure more slender and flexible, and it is difficult to judge the axial distribution of unbalance. Meanwhile, the engine rotor's working speed is above the second critical speed and even exceeds the third-order speed. The small imbalance of the rotating shaft will cause large vibration, coupled with the influence of mode shape, resulting in difficulty in rotor dynamic balance, low efficiency and poor effect of the flexible rotor dynamic balance. Therefore, finding out the unbalance position is of great significance to determine the balance plane during rotor dynamic balance, and improve the balance efficiency and effect of flexible rotor. Firstly, the paper established the dynamic model of power turbine rotor, analyzed the vibration response law of rotor with unbalance at different positions, and found out the sensitive position of rotor unbalance. Then, a power turbine rotor unbalance position identification method, based on deep learning, one-dimensional convolution neural network (1D-CNN) is proposed. The multiple measured response data of the rotor with different unbalance positions are input into 1D-CNN for training. Finally, at subcritical speed, critical speed and supercritical speed, the accuracy of 1D-CNN method for rotor unbalance position identification is 99.5%, 99.5%, and 99.0% respectively, which verifies the effectiveness, feasibility of 1D-CNN method for rotor unbalance position identification, and provides a new solution for intelligent identification of aeroengine rotor unbalance position. [ABSTRACT FROM AUTHOR]

During the service of rotating machinery, the pedestal bolts are prone to looseness due to the vibration environment, which affects the performance of rotating machinery and generate potential safety hazard. To monitor the occurrence and deterioration of the pedestal looseness in time, this paper proposes a data-driven diagnosis strategy for the rotor-bearing system. Firstly, the finite element model of a rotor-bearing system is established, which considers the piecewise nonlinear force caused by pedestal looseness. Taking the vibration response as output and periodic unbalanced force as input, the system's NARX (Nonlinear Auto-Regressive with exogenous inputs) model is identified. Then GALEs (Generalized Associated Linear Equations) are used to evaluate NOFRFs (Nonlinear Output Frequency Response Functions) of the NARX model. Based on the first three-order NOFRFs, the analytical expression of the second-order optimal weighted contribution rate is derived and used as a new health indicator. The simulation results show that compared with the conventional NOFRFs-based health indicator, the new indicator is more sensitive to weak looseness. Finally, a rotor-bearing test rig was built, and the pedestal looseness was performed. The experiment results show that as the degree of looseness increases, the new indicator SRm shows a monotonous upward trend, increasing from 0.48 in no looseness to 0.90 in severe looseness, a rise of 89.7%. However, the traditional indicator Fe2 has no monotonicity, which further verifies the sensitivity of the first three-order NOFRFs-based second-order optimal weighted contribution rate and the effectiveness of the proposed data-driven feature extraction strategy. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to propose an index for diagnosing the rub-impact fault intuitively. Due to the slow change of some diagnostic indexes, compared with the index S proposed in this paper. Therefore, the fault degree of the system with rub-impact is studied. Methods: Both methods weighted contribution rate of nonlinear output frequency response functions and stochastic resonance are combined. The parameters of stochastic resonance are optimized by adopting genetic algorithm. And then, the nonlinear characteristics are extracted by combining stochastic resonance and weighted contribution rate of nonlinear output frequency response functions. Analyzing these characteristics indicates the diagnosis results are influenced by man-made selection of the parameter ρ. According to the parameter ρ, therefore, a reference value ρ0 is defined for users to form a new diagnosis index S. Results and Conclusion: With the definite parameter ρ0, the index reduces the influence on diagnosis caused by people to choose the parameter ρ subjectively. From the index performance, there is an approximately linear trend to identify the rub-impact faults. And it has better adaptability as the parameters change. Finally, the property of S is confirmed by the experiment. The combination of the two methods provides a new option for weak signal extraction. [ABSTRACT FROM AUTHOR]

Developing low‐cost and highly efficient hydrophobic absorbents via simple and environmentally friendly method is demanded for oil‐water separation. This paper reports the preparation of hydrophobic absorbents of porous poly(4‐tert‐butylstyrene‐co‐divinylbenzene) (poly(tBS‐co‐DVB)) via high internal phase emulsion (HIPE) template method. The effects of crosslinking degree and internal phase volume fraction on the porous structure and adsorption performance of the absorbents are investigated. As the tBS/DVB molar ratio increases from 1:1 to 4:1, the adsorption performance of poly(tBS‐co‐DVB) toward hexane first increases to a maximum at a molar ratio of 3:1 and then decreases. As the internal phase volume fraction increases, the specific surface area (SSA) and porosity of the poly(tBS‐co‐DVB)s notably increase from 33.06 m2/g and 84.07% to 102.89 m2/g and 92.94%, respectively. When the internal phase fraction is 95 vol%, the obtained poly(tBS‐co‐DVB) foam with a water contact angle of 140° shows an absorbing capacity as high as 70.21 g/g for dichloromethane. After 10 consecutive adsorption‐desorption cycles, the adsorption performance of the poly(tBS‐co‐DVB) foam shows only a slight decrease, indicating an excellent recycling ability. The obtained poly(tBS‐co‐DVB) foams exhibit the advantages of facile preparation, high oil absorption capacity and satisfactory recoverability, which enable them potential as sustainable oil adsorbents. [ABSTRACT FROM AUTHOR]

In this paper, the roller bearings partial wear due to extreme inclined load caused by poor installation is investigated. First, based on non-Hertz contact theory, a quasi-static model of roller bearing with inclined load is established by the influence coefficient method. The influence of deflection angle between the inner ring and outer ring on the non-uniform contact characteristics is discussed. The finite element model of roller bearing housing is established and optimized by the theoretical results. The double-loading zones characteristic of roller bearings caused by the inclined installation of the housing is analyzed. The influence of the extreme position of the rollers on the deformation of the bearing is also considered. The partial wear experiment of the bearing is carried out. The contact surface roughness and deformation of the outer ring are measured. Fusing the analytical analysis, finite element analysis, and experiment, the effects of external inclined loads, rollers extreme positions, and wear on the deformation of the contact surface of the outer ring are systematically studied to reveal the mechanism of partial wear. [ABSTRACT FROM AUTHOR]

The abnormal wear of a rolling element bearing caused by early failures, such as pitting and spalling, will deteriorate the running state and reduce the life. This paper demonstrates the importance of oil debris monitoring and its effective feature extraction for bearing health assessment. In this paper, a rolling bearing-rotor test rig with forced lubrication is set up and the nonferrous contaminants with higher hardness were introduced artificially to accelerate the occurrence of pitting and spalling. The early failure and abnormal wear of rolling bearings cannot be effectively detected only through the vibration signal; the temperature and oil debris monitoring data are also collected synchronously. Two features regarding the ferrous particle size distribution are extracted and fused with vibration based-features to form a feature set. The sensitive features are extracted from the features set using the Neighborhood Component Analysis method to avoid feature redundancy. Finally, the importance of the oil debris based-features for the diagnosis of abnormal bearing wear is analyzed with different machine learning algorithms. Taking SVM classifier as an example, the experiment results show that the introduction of oil debris based-features increases the diagnostic accuracy by 15.7%. [ABSTRACT FROM AUTHOR]

Constructing multi-component materials with dielectric–magnetic synergy effects has been a significant focus of recent works to enhance microwave absorption efficiency. Herein, a top-down exfoliation strategy for forming carboxylated g-C3N4 (CCN) was demonstrated to achieve rich interfaces and enhanced interface compatibility. The abundant defects and functional groups (–COOH, –OH, C–O, and C＝O) of CCN enhanced the dipole polarization. Furthermore, MWCNTs and Fe3O4 were facilely decorated onto the surface of CCN by the general co-precipitation method to form CCN/C-Fe3O4 composite absorbers with multiple heterogeneous interfaces and attenuation mechanisms. Changing the content of CCN, CN/C-Fe3O4 exhibits excellent wave absorption and impedance matching characteristics with a minimum reflection loss value (RLmin) of −51.74 dB at only 1.9 mm (11.12 GHz), and the efficient absorption bandwidth can reach up to 4.28 GHz at 1.4 mm. This work reveals how CCN enhanced the synergistic balance between the dielectric–magnetic loss in composites. It also provides a new idea for the facile synthesis of novel multi-component composites for high-performance microwave absorption. [ABSTRACT FROM AUTHOR]

The generation of cyclic carbonates by the cycloaddition of CO2 with epoxides is attractive in the industry, by which CO2 is efficiently used as C1 source. Herein, a series of catalysts were developed to efficient mediate the cycloaddition of CO2 with epoxides to generate carbonates. The catalysts were easily synthesized via the amine‐formaldehyde condensation of ethidium bromide with a variety of linkers. The newly prepared heterogeneous catalysts have high thermal stability and degradation temperatures. The surface of the catalysts is smooth and spherical in shape. The effect of temperature, pressure, reaction time and catalyst dosage on the cycloaddition of CO2 with epoxide were investigated. The results show that the catalyst with 1,3,5‐tris(4‐formylphenyl)benzene as the linker can achieve 97.4 % conversion efficiency at the conditions of 100 °C, reaction time of 12 h, and the reaction pressure of 1.2 MPa in a solvent‐free environment. Notably, the polymers serve as homogeneous catalysts during the reaction (reaction temperature above Tg) and can be separated and recovered easily as homogeneous catalysts at room temperature. In addition, the catalyst is not only suitable for a wide range of epoxide substrates, but also can be recycled many times. Furthermore, DFT calculations show that the coordination between the electrophilic center of the catalyst and the epoxide reduces the energy barrier, and the reaction mechanism is proposed based on the reaction kinetic studies and DFT calculations. [ABSTRACT FROM AUTHOR]

Two imine‐based covalent organic framework photocatalysts with different building units, TPB‐DMTA‐COF and TAT‐DMTA‐COF, for photo‐induced energy transfer reversible complexation‐mediated radical polymerization (PET‐RCMP) were developed and investigated, producing ideal polymers with accurate molecular weight and moderate dispersity under visible light irradiation. The chain extension and spatiotemporal control experiments revealed the high chain‐end fidelity of polymers and the compatibility of RCMP processes in both bulk and aqueous system. Moreover, density functional theory (DFT) calculations verified that heteroatom‐doped TAT‐DMTA‐COF exhibits higher activities for weakening C−I bond energy barrier, which promotes PET‐RCMP polymerization performance. This work demonstrates that rational adjustment of building block for constructing COF heterogeneous photocatalyst can enhance the catalytic performance of PET‐RCMP, providing a design methodology for the development of polymeric organic photoelectric semiconductor catalysts to mediate RCMP. [ABSTRACT FROM AUTHOR]

Two imine‐based covalent organic framework photocatalysts with different building units, TPB‐DMTA‐COF and TAT‐DMTA‐COF, for photo‐induced energy transfer reversible complexation‐mediated radical polymerization (PET‐RCMP) were developed and investigated, producing ideal polymers with accurate molecular weight and moderate dispersity under visible light irradiation. The chain extension and spatiotemporal control experiments revealed the high chain‐end fidelity of polymers and the compatibility of RCMP processes in both bulk and aqueous system. Moreover, density functional theory (DFT) calculations verified that heteroatom‐doped TAT‐DMTA‐COF exhibits higher activities for weakening C−I bond energy barrier, which promotes PET‐RCMP polymerization performance. This work demonstrates that rational adjustment of building block for constructing COF heterogeneous photocatalyst can enhance the catalytic performance of PET‐RCMP, providing a design methodology for the development of polymeric organic photoelectric semiconductor catalysts to mediate RCMP. [ABSTRACT FROM AUTHOR]

Kick is one of the most important drilling problems, and because its occurrence makes drilling engineering extremely complex, it is essential to predict the possibility of kick as soon as possible. In this study, k-means clustering was combined with four artificial neural networks: regularized RBFNN, generalized RBFNN, GRNN, and PNN, to estimate the kick risk. To reduce data redundancy and normalize the drilling data, which contain kick conditions, k-means clustering was introduced. The output layer weights were then determined using a brute-force search with different Gaussian function widths, resulting in a series of artificial neural networks composed of different clustering samples and different Gaussian function widths. The results showed that the prediction accuracy of regularized RBFNN + k-means model was the highest, that of the GRNN + k-means model was the lowest. The kick prediction accuracy for regularized RBFNN, generalized RBFNN, GRNN, and PNN were 75.90%, 65.20%, 51.70%, and 70.16%, respectively. This method can be used to enhance the speed and accuracy of kick risk prediction in the field while facilitating the use of and advances in risk warning technology for deep and high-temperature and high-pressure wells. [ABSTRACT FROM AUTHOR]

Heteroatom doped carbonaceous material with high specific surface area (SSA) is vital for assembling advanced supercapacitor. Here, a moderate and valid strategy is proposed to synthesize N, S co‐doped porous carbons (NSPCs) which are derived from porous resorcinol‐melamine‐formaldehyde‐thiourea (RMFT) resins via high internal phase emulsion (HIPE) template. The morphology, structure, porous characteristics and chemical ingredients of the prepared NSPCs are investigated by SEM, XRD, Raman spectra, and XPS systematically. The obtained NSPCs show typical open‐cell morphology. As the molar ratio of thiourea to melamine (T/M) increased from 0:1 to 2:1, the SSA of NSPC increases gradually from 927 to 1721 m2 g−1. Electrochemical tests show that when T/M is 2:1, the specific capacity of NSPC reaches 213.5 F g−1 at 1 A g−1. After 10,000 charge–discharge cycles at 10 A g−1, the retention ratio of specific capacitance is 99.6%, indicating an excellent cycling stability. Excellent performances together with facile preparation make NSPC via HIPE template a potential candidate as electrode of advanced supercapacitors. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are a class of promising photocatalysts for conversing light energy into chemical energy. Based on the tunable building blocks, COFs can be well‐designed as photocatalyst for mediating reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. Herein, 1,3,6,8‐tetrakis(4‐formylphenyl)pyrene (TFPPy) and 2,2″‐bipyridine‐5,5″‐diamine (Bpy) are chosen to construct imine‐based TFPPy‐Bpy‐COFs for catalyzing RAFT polymerization of methacrylates under white light irradiation. The well‐defined polymers with precise molecular weight and narrow molecular weight distribution are obtained. The switch on/off light experiments suggest excellent temporal control toward RAFT polymerization system and the chain‐extension reaction indicates high chain‐end fidelity of macro‐initiators. Mechanism study clarifies that the electron transfer between excited state of TFPPy‐Bpy‐COFs and RAFT agent can form living radicals to mediate polymerization. This methodology provides a novel platform for reversible‐deactivation radical polymerization using COFs as heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

In this paper, a pedestal looseness fault model of a rotor-bearing-seal system is established. Under two working conditions of the same direction eccentricity (Working Condition 1) and reverse eccentricity (Working Condition 2), rotor orbits, vibration waveforms, spectrum cascade, and Poincaré maps are used to study the dynamic characteristics of the system when the sliding bearing support is loosened. The influence of speed, the unbalance of two discs, the looseness clearance, and the mass of bearing support on system characteristics are analyzed. The study found that Working Condition 2 is more likely to cause looseness of the bearing support. Moreover, for the rotor system in this paper, the pedestal looseness fault is more likely to occur near the second-order critical speed. Through analysis of the spectrum, it is found that the spectrum of the looseness fault will show multiple frequencies or continuous spectra, and the rotor orbits will appear "cylindrical." [ABSTRACT FROM AUTHOR]

Carbon‐supported metal nanoparticles (NPs) play important roles in heterogeneous catalysis. In particular, supported bimetallic catalytic systems can be promising multifunctional catalysts for one‐pot tandem/cascade reactions, in which two or more successive independent reactions are realized in one pot. In this manuscript, we report the preparation of a carbon‐supported bimetallic CoCu catalytic system (Co−C@Cu−C), with Co NPs wrapped by carbon‐supported Cu NPs, from the pyrolysis of a core‐shell structured Co−MOF‐74@Cu−MOF‐74. The as‐obtained Co−C@Cu−C acts as a bifunctional catalyst for the transformation of phenylacetylene to 1, 4‐diphenyl‐1, 3‐butadiene in one pot, in which supported metallic Cu NPs and Co NPs are active for the coupling and hydrogenation reaction respectively. By tuning the reaction rates of the coupling and the hydrogenation in this tandem reaction over the Co−C@Cu−C via changing the reaction medium and the reducing agent, an efficient direct transformation of phenylacetylene to 1, 4‐diphenyl‐1, 3‐butadiene was realized. This work not only highlights the important role of MOFs in the preparation of multifunctional carbon supported metal NPs for heterogeneous catalysis, but also demonstrates the possibility of tuning the reaction rates of different catalytic steps in a tandem reaction to realize an efficient overall reaction. [ABSTRACT FROM AUTHOR]

The work reported the preparation of hierarchically porous carbons (HPCs) with adjustable pore architectures using high internal phase emulsion (HIPE) template with the presence of polyaniline-coated carbon nanotubes (PANI-CNTs). PANI-CNTs were obtained via in situ polymerization of aniline in CNT suspension as confirmed by scanning electron microscope (SEM) and thermogravimetric analysis (TGA). Porous polydivinylbenzene (PDVB) monoliths were prepared by polymerizing the continuous phase of HIPE with PANI-CNTs dispersed in the internal phase. After carbonization and activation, HPCs with variable pore architectures were obtained. As observed by SEM, the PANI-CNTs showed notable influence on the pore architectures of PDVBs and HPCs. The void size of PDVB precursor reduced with the increase of the mass ratio of PANI to CNT, as well as the content of PANI-CNTs. Nitrogen adsorption/desorption measurements indicated the coexistence of mesopores and micropores, namely, hierarchical pores. The specific surface area (SSA) of HPC increased along with the content of PANI-CNTs from 1893 to 2392 m2/g. The capability of HPCs as the electrode material of supercapacitor was evaluated via electrochemical tests. The results indicated that the HPC with optimized pore architecture showed a higher specific capacitance (168.6 F/g) than the contrast sample (130.9 F/g) at 1 A/g. The better capacitance performance of HPC obtained with the presence of PANI-CNTs could be attributed to the reasonable hierarchical pores, higher SSA, and higher graphitization degree. [ABSTRACT FROM AUTHOR]

Fault features extraction method for slight misalignment of rotor systems is researched in this paper. When a rotor system with faults is excited by harmonic inputs, system response will contain higher harmonic components. Phenomenon of these higher harmonics implies the presence of nonlinear features in a rotor system. When extracting these nonlinear features, traditional methods have certain limitations, and it is easy to ignore weak features of a rotor system. Nonlinear output frequency response functions (NOFRFs) can extract effectively nonlinear features of a rotor system from noise-containing vibration signals and are used in many fault diagnosis fields. However, as for weak damage to structures and in the early stages of a system faults, fault features reflected by high-order NOFRFs are not still obvious enough. Therefore, a new method, named variable weighted contribution rate of NOFRFs, is proposed in this paper. This method enhances the ratio of high-order output frequency response to total output response of a rotor system. Based on this method, a new index MR is proposed to detect the faults of a rotor system. In addition, lumped mass model is used in this paper to simulate misaligned rotor system with slight misalignment, and the sensitivities of the traditional methods and new index for slight misalignment fault features extraction are compared. The results indicate that the new index is more sensitive for the slight misalignment rotor system. Additionally, the rotor system with misalignment fault experiment table is built, and the effectiveness of this new index for detecting the slight misalignment fault of the rotor system is verified. [ABSTRACT FROM AUTHOR]

Rub-impact between the rotating and static parts is a more common fault. The occurrence of faults is often accompanied by the generation of nonlinear phenomena. However, it is difficult to find out because the nonlinear characteristics are not obvious at the beginning of the fault. As a new frequency domain-based method, nonlinear output frequency response functions (NOFRFs) use the vibration response to extract the nonlinear characteristics of the system. This method has a better recognition rate for fault detection. Also, it has been applied in structural damages detection, but the high-order NOFRFs have the characteristics that the signals are weak and the features are difficult to extract. On this basis, the concept of the weighted contribution rate of the NOFRFs is proposed in this paper. The variable weighted coefficients with orders are used to amplify the influence of high-order NOFRFs on the nonlinearity of the system so as to extract its fault characteristics. The new index RI is proposed based on Clenshaw–Curtis quadrature formula to eliminate the effect of artificially selected weighted coefficients on sensitivity. Especially in the early stage of the fault, the new index varies greatly with the deepening of the fault. Both simulation and experimental results verify the validity and practicability of the new index. The new index has certain guiding significance in the detection of mechanical system faults. [ABSTRACT FROM AUTHOR]

In this paper, a combination algorithm for diagnosing rotor crack fault is presented. Firstly, the nonlinear output frequency response functions (NOFRFs) are used to analyze the severity of crack damage in the rotor system qualitatively. The NOFRFs are obtained by processing the vibration signal through the nonlinear output frequency response functions. Further analysis of the NOFRFs can determine the crack depth qualitatively. Secondly, the position of the crack is then located using the crack position index (CPI) λ based on the higher harmonic response (HHR) and the dynamic compliance matrix. The simulation and experimental results show that the G2(j2wF) in NOFRFs is very sensitive to crack depth, and the crack position index (CPI) λ can determine the shaft segment effectively where the crack is located. The advantage of this combination algorithm is that it can detect the crack faults by measuring the vibration signal of the cracked rotor at two speeds, which makes the measurement process more simplified and reduces the measurement time for real-time monitoring. At each speed only the vibration response of the two nodes need to be measured, which greatly reduces the number of sensor used in the measurement process and reduces the cost of monitoring. The combination algorithm can diagnose cracked rotor faults effectively and has certain application value in the diagnosis of cracked rotor fault. [ABSTRACT FROM AUTHOR]

Polystyrene-based polyHIPEs were synthesized by RAFT polymerization and strengthened by introducing UPy groups (2-Ureido-4[1 H] pyrimidinone) into polyHIPEs. Incorporation of UPy groups into polyHIPEs has created pores and controlled the porous morphology of resulting material. Meanwhile, the incorporation of quadruple hydrogen bond introduced some pins into polyHIPE. In comparison to the polyHIPE without reinforcement through quadruple hydrogen bond, the porosity of the reinforced sample was as high as 92 % and its Young's modulus reached to 28.5 ± 3.9 MPa which was improved by 50 %. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Chitosan is considered as a promising material in the pharmaceutical and biomedical fields based on its unique biological properties. This review presents chemical modifications of chitosan via using photosensitizers, dendrimers, sugars, cyclodextrins and crown ethers as modifiers and places an emphasis on the applications of chitosan derivatives as carriers in drug delivery systems, as supporting materials for tissue engineering, as dye removing agents and as metal ion adsorbents. Recently, the progress on chemical modifications of chitosan is quite rapid and we are confident that a more extensive range of applications of chitosan derivatives could be expected in the near future. [ABSTRACT FROM PUBLISHER]

This contribution reported a facile approach to bimodal polyethylene (BMPE) with a consecutively tunable molecular weight distribution (MWD). The BMPEs were synthesized from ethylene polymerization catalyzed by α-diimine Ni complex/ rac-ethylenebis(indenyl) zirconium chloride ( rac-Et(Ind)ZrCl)/MAO in the presence of diethyl zinc (ZnEt). From GPC results, PE samples with molecular weight (MW) ranging from 78.9 kg/mol to 1.5 kg/mol and PDI varying gradually from 2.5 to 12.7 were obtained via simply adjusting the equiv. of ZnEt. The combination of Soxhlet extraction and GPC analysis indicated that the obtained BMPEs consist of soluble fractions with higher molecular weights and residual fractions with lower molecular weights. The crystallization processes and crystal morphologies of the BMPEs were recorded by polarized optical microscope (POM). Additionally, the influence of the obtained BMPE on the mechanical properties of commercial high density polyethylene (HDPE) after melt blending was studied via dynamic mechanical analysis (DMA). [ABSTRACT FROM AUTHOR]

In this article, a functional ferrocene-based metalloligand has been synthesized and used as the building block to assemble novel coordination polymer microspheres. Specifically, this metalloligand was coordinated with two different types of metal ions (Co and Mn) to fabricate two different but isostructural microspheres under solvothermal conditions. To deepen our understanding of the formation process of the coordination polymer microspheres, a growth mechanism has been proposed based on the morphology change of these spheres throughout the whole reaction process. Furthermore, the prepared multi disperse microspheres, in the form of hollow spheres with high thermostability, can be applied to store hydrogen for their promising hydrogen uptake capacity (1.84wt% for CPM-1 and 1.00 wt% for CPM-2 at 163 K under 5 MPa). Moreover, the different adsorption enthalpies of these two materials that relevant to the varied hydrogen uptake capacity have been calculated, compared and explained. [ABSTRACT FROM AUTHOR]

During its operation, a rotor system can be exposed to multiple faults, such as rub-impact, misalignment, cracks and unbalancing. When a crack fault occurs on the rotor shaft, the vibration response signals contain some nonlinear components that are considerably tougher to be extracted through some linear diagnosis methods. By combining the Nonlinear Output Frequency Response Functions weighted contribution rate (WNOFRFs) and Kullback–Leibler (KL) divergence, a novel fault diagnosis method of improved WNOFRFs is proposed. In this method, an index, improved optimal WNOFRFs (IOW), is defined to represent the nonlinearity of the faulty rotor system. This method has been tested through the finite element model of a cracked rotor system and then verified experimentally at the shaft crack detection test bench. The results from the simulation and experiment verified that the proposed method is applicable and effective for cracked rotor systems. The IOW indicator shows high sensitivity to crack faults and can comprehensively represent the nonlinear properties of the system. It can also quantitatively detect the crack fault, and the relationship between the values of IOW and the relative depth of the crack is approximately positively proportional. The proposed method can precisely and quantitatively diagnose crack faults in a rotor system. [ABSTRACT FROM AUTHOR]

This contribution explored the adjustment of polyethylene (PE) microstructures via chain transfer ethylene polymerization catalyzed by α-diimine Ni complex/methylaluminoxane (MAO) with diethyl zinc (ZnEt) as the chain transfer agent (CTA). Ethylene polymerizations were conducted in the presence of varying equivalents of ZnEt (Zn/Ni) at 5 °C, 22 °C and 32 °C, respectively. From high temperature GPC results, it was found that the molecular weight (MW) of prepared PE decreased with the increase of Zn/Ni ratio as a whole, indicating the occurrence of chain transfer to ZnEt. From C NMR spectra, the branching distributions of PE were calculated. The data indicated that the addition of ZnEt brought weak influences on the branching distribution of resultant PE. It is worthwhile to note that both the catalytic activity and branching degree reach their maximums at Zn/Ni = 100. As a significant factor, temperature showed a remarkable influence on ethylene polymerizations and on the PE microstructures. A probable mechanism for the influence of chain transfer to CTA on PE microstructures was proposed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Temperature and chain transfer agents (CTA) are two primary factors that influence the microstructure of the resultant polymer. This contribution mainly studied the effects of polymerization temperature and concentration of diethyl zinc (ZnEt2) on ethylene polymerization and chain microstructure of resultant polyethylene (PE). The polymerization temperature showed a notable influence on the catalytic activity and the molecular weight of PE. It was observed that raising polymerization temperature from 4°C to 36°C resulted in a gradual decrease of the catalytic activity and a dramatic reduction of the molecular weight. The molecular weight of the prepared PE also decreased regularly with the increase of the concentration of ZnEt2while the polydispersity did not broaden. The branching structure of PE prepared in the presence of varying concentrations of ZnEt2was investigated via13C-NMR spectroscopy. The addition of ZnEt2had a moderate influence on the total branching degree and the branching distribution of PE. A possible mechanism is proposed for the influence of ZnEt2on the microstructure of resultant PE. [ABSTRACT FROM AUTHOR]

Objective. There is no animal model that displays the features of non-alcoholic steatohepatitis (NASH) characterized by insulin resistance (IR) and fibrosing steatohepatitis. This study aimed to develop a novel IR-associated rat model of NASH. Material and methods. Male Sprague-Dawley rats were fed with the high-fat diet (HFD) supplemented with 0.25% propylthiouracil for 2, 4, 6, 8 and 12 weeks. The IR-associated metabolic parameters, histological assessment and the expression of key insulin signaling molecules were determined. The circulating and tissue pro-inflammatory factors and adipocytokines were examined. Results. In the HFD-fed rats, the systemic and multiple-organ IR was developed after 4 weeks, whereas the histological changes characterized by steatohepatitis, inflammatory response in the visceral adipose tissue and proliferative pancreatic islet β-cells appeared after 6 weeks, concomitant with altered expression of key insulin signaling molecules. In addition, the elevated levels of serum tumor necrosis factor α (TNF-α), soluble TNF receptor2, interleukin (IL)-6, CC-chemokine ligand (CCL)2 and resistin were parallel with the severity of hepatic inflammation, while the levels of serum adiponectin, leptin and TNF-α, but not resistin, were correlated with IR. Conclusions . We have developed a systemic IR-associated NASH model of rats, with impaired insulin signaling, systemic inflammation and appropriate pathology characterized by human NASH, and provided a realistic experimental model for elucidating the association between IR and the pathogenesis of NASH. [ABSTRACT FROM AUTHOR]

To summarize the pathological features of nonalcoholic liver disease (NAFLD) in China based on a histological scoring system for NAFLD designed by the Pathology Committee of NASH Clinical Research Network (NASH-CRN), the specimens of liver needle biopsies from 130 patients with NAFLD were histopathologically analyzed by haematoxylin eosin, reticular fiber and Masson trichrome stain. Immunohistochemistry staining was used to exclude non-NAFLD cases combined with clinical data. Hepatic steatosis, lobular inflammation, hepatocytic ballooning and fibrosis were presented widespread in NAFLD liver tissues. Furthermore, macrovesicular steatosis predominantly located in acinar zone 3 was the main histologic feature of NAFLD and lobular inflammation was usually presented mildly. Hepatocyte ballooning was observed in 94.6% of all 130 cases. Mild perisinusoidal fibrosis and periportal fibrosis were often observed in stage 1 cases. According to the statistic analysis, hepatic steatosis was positively correlated with lobular inflammation, hepatocytic ballooning and fibrosis ( r = 0.587, 0.488, 0.374, respectively, all P value < 0.01). The number of microgranulomas, lipogranulomas and apoptotic bodies increased following severity of steatosis, lobular inflammation and fibrosis. Meanwhile, the number of megamitochondria and glycogen nuclei was paralleveled to the degree of hepatocytic ballooning ( P value all < 0.01). We suggest that the role of portal inflammation should be emphasized besides hepatic steatosis, lobular inflammation, hepatocyte ballooning and fibrosis in diagnosis and evaluation of NAFLD. It needs to be further verified whether microgranulomas, lipogranulomas and apoptosis bodies could be used as histopathological markers of development of NAFLD. The number of megamitochondria is more frequently be found in NAFLD, while in alcoholic liver diseases was Mallory bodies. [ABSTRACT FROM AUTHOR]