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This research serves to advance the development of engineering computational fluid dynamics (CFD) computing efficiency for the analysis of pressurized water reactor (PWR) core using rod-type fuel assemblies with mixing vanes (one kind of typical PWR core). In this research, a CFD scheme based on the reconstruction of the initial fine flow field (RIF CFD scheme) is proposed and analyzed. The RIF scheme is based on the quantitative regulation of flow velocities in the rod-type PWR core and the principle that the CFD computing efficiency can be improved greatly by a perfect initialization. In this paper, it is discovered that the RIF scheme can significantly improve the computing efficiency of the CFD computation for the rod-type PWR core. Furthermore, the RIF scheme also can reduce the computing resources needed for effective data storage of the large fluid domain in a rod-type PWR core. Moreover, a flow-ranking RIF CFD scheme is also designed based on the ranking of the flow rate, which enhances the utilization of the flow field with a closed flow rate to reconstruct the fine flow field. The flow-ranking RIF CFD scheme also proved to be very effective in improving the CFD efficiency for the rod-type PWR core.

Real-world data is often organized at different levels of granularity with specified concept hierarchies. Multi-scale information tables represent such a type of data set in a hierarchical form. In this paper, we aim to focus on rule extraction in multi-scale decision tables. Unlike the case of attribute reduct, we consider a type of generalization reduct in multi-scale decision tables. This approach requires both the least number of attributes and the coarsest level of scales according to different reduct standards. The present study is conducted at the three different levels, that is, generalization reducts for objects, decision rules and multi-scale decision tables, respectively. The construction of granularity trees and the selection of cuts play a crucial role. At each level, we present various types of generalization reducts according to different requirements. The relationship between them is also investigated. Moreover, a comparative study between generalization reducts and attribute reducts is also performed. Based on the notion of generalization reducts, the procedure to extract the set of optimal decision rule in multi-scale decision tables is provided and an illustrative example is also given to show the proposed approach.

Synchronization is the key part to ensure the high performance of grid-connected systems. Phase-locked loop (PLL) is one of the most popular synchronizations due to its simple implementation and robustness under certain grid variations. Particularly, in single-phase applications, PLL based on second-order generalized integrator (SOGI-PLL) is widely used because of its simple structure, certain filtering ability and frequency adaptability. The sensitivity of SOGI-PLL to the dc offset and low-order harmonics has been studied a lot in the literature and many solutions have been proposed. However, as more and more power electronic devices are integrated into the power grid recently, the grid condition becomes more complex. As a result, the nonlinear loop coupling phenomenon of SOGI-PLL is more severe and obvious and thus the performance of SOGI-PLL is degraded a lot, especially under the conditions of grid frequency variations and weak grid. A popular method is to use the frequency-fixed SOGI-PLL (FFSOGI-PLL) while how to eliminate the estimation error under frequency variations remain an important task. Though some scattered methods have been proposed, a simple yet effective strategy is still missing. Besides, it has been shown that the system stability margin will be reduced due to the negative-resistance behavior of PLL. However, the models derived in the current documents cannot accurately reveal the instabilities caused by the standard SOGI-PLL for missing the dynamics of the frequency feedback loop. Moreover, the PLL parameters are usually designed according to the PLL bandwidth to guarantee system stability under a weak grid. How to optimize the parameters is still unclear. In view of this, this article further summarizes and reviews the existing achievements of single-phase SOGI-PLL, and points out the problems to be solved and the development direction to improve the SOGI-PLL under more complex and non-ideal grid conditions.

Short-term traffic forecasting is an important part of contemporary intelligent transportation systems. In this paper, based on echo state network optimized by improved fruit fly optimization algorithm (ESN-IFOA), a model is proposed to provide a five-minute forecast of traffic volume. In IFOA, parallel searching strategy and uniform crossover operator are applied to enhance searching range and communication between swarms. Simultaneously, the source allocation strategy is proposed to calculate the number of fruit flies generated by each swarm in the next iteration. The five main parameters of ESN are optimized by the proposed IFOA. Massive of prediction results and algorithm comparisons demonstrates that ESN-IFOA has very good forecasting ability for the five-minutes forecast of traffic volume.

Transition metal compounds are attractive for their significant applications in supercapacitors and as non-noble metal catalysts for electrochemical water splitting. Herein, we develop Ni3S2 nanorods growing directly on Ni foam, which act as multifunctional additive-free Ni3S2@Ni electrode for supercapacitor and overall water splitting. Based on PVA-KOH gel electrolyte, the assembled all-solid-state Ni3S2@Ni//AC asymmetric supercapacitor delivers a high areal energy density of 0.52 mWh cm−2 at an areal power density of 9.02 mW cm−2, and exhibits an excellent cycling stability with a capacitance retention ratio of 89% after 10000 GCD cycles at a current density of 30 mA cm−2. For hydrogen evolution reaction and oxygen evolution reaction in 1 M KOH, Ni3S2@Ni electrode achieves a benchmark of 10 mA cm−2 at overpotentials of 82 mV and 310 mV, respectively. Furthermore, the assembled Ni3S2@Ni||Ni3S2@Ni electrolyzer for overall water splitting attains a current density of 10 mA cm−2 at 1.61 V. The in-situ synthesis of Ni3S2@Ni electrode enriches the applications of additive-free transition metal compounds in high-performance energy storage devices and efficient electrocatalysis.

Electro-hydrostatic actuator (EHA) is a highly integrated local hydraulic actuation system for more electric aircraft (MEA). However, the motor heating has always been the bottleneck in actual applications. In this paper, a novel energy-recovery EHA (ER-EHA) with specific hydraulic energy recovery unit is proposed to solve the problem. ER-EHA can reduce the heating of the motor, which is beneficial to improve the reliability and mean time before failure of the system. Besides, the power resistor is eliminated in the new system, so the volume of the system is reduced, and the power-to-weight ratio of the system is improved, which satisfies the needs of MEA. Simulations can prove the effect of energy recovery unit. To show the efficiency of our proposed structure, a specific test bench called redundant degree heterogeneous drives loads test bench is designed, and experiments are carried out in this paper. The results reflect its contribution to motor heating reduction.

Octahedral rotation in perovskites and their transformations have a profound influence on their properties. In this work, an easy-to-use model is proposed to reveal the nature of the oxygen octahedral rotation (OOR) changing behaviors at interfacial regions. Different from first principle simulations and symmetry analysis, we establish a general elastic model with a six angle symbol system based on the intrinsic geometry characteristics of the oxygen octahedra network. In the light of the elastic energy generated by octahedral tilting mismatches at interfaces, the systematic analysis is conducted on the changing behavior and mechanism of octahedral rotation with different OOR patterns. Consequently, it is found that there are two forms of basic component angle changing across the interface, i.e. abrupt change and gradual change, depending on the relationship between the directions of the rotational axis of basic component angles and the interface. Furthermore, the coexistence of two forms at the same interface and a special case for gradual change are investigated, which could hardly be identified or predicted by other models and analysis established previously. Generally, the model can be applied to interpret and predict the octahedral rotation changing behavior in perovskites, involving film/substrate heterostructure in epitaxial synthesized thin films, domain boundaries, etc., which agree with the practical examples. Although the model has its limitations due to the complex chemical configuration in 3D oxygen octahedra network, it is expected to be universal for perovskites. Taking the advantage of mathematical simplicity, this model can be a powerful tool for interfacial engineering in perovskites.

The existing database of the loading response of offshore pile foundations needs to be enriched, so that safety and economic considerations can be optimally balanced in design. This paper details a...

Visual imaging that can extract three-dimensional (3D) space or polarization information on the target is essential in broad sciences and technologies. The simultaneous acquisition of them usually demands expensive equipment and sophisticated operations. Therefore, it is of great significance to exploit convenient approaches for four-dimensional (3D and polarization) visual imaging. Here, we present an efficient solution based on self-assembled asymmetric liquid crystal microlenses, with freely manipulated phase profiles and symmetry-breaking properties. Accordingly, characteristics of multifocal functionality and polarization selectivity are exhibited, along with the underlying mechanisms. Moreover, with a specific sample featured by radially increased unit sizes and azimuthally varied domain orientations, the discriminability of four-dimensional information is extracted in a single snapshot

For the sake of excellent strain performance for actuator application, Sn-modified Bi0.5Na0.5TiO3–Bi0.5K0.5TiO3 (BNT–BKT) ceramics were designed and prepared by solid-state reaction method. The crystal structures and microstructures of Bi0.5(Na0.75K0.25)0.5(Ti1−xSnx)O3 (abbreviated as BNKT–xSn, x = 0, 0.02, 0.05, 0.08) were systematically investigated together with their strain performance. It is found that all the compositions possessed a single perovskite structure phase by X-ray diffraction patterns. With increasing Sn content, the ferroelectric phase with mainly tetragonal structure gradually transformed into the ergodic relaxor phase in pseudocubic structure with nanodomains further confirmed by high-resolution transmission electron microscope images. Both the P–E and I–E loops confirmed this structural change and the coexistence of ferroelectric phase and ergodic relaxor phase at x = 0.02, where a large strain of 0.37% was achieved with low hysteresis (21.8%). By analyzing the bipolar and unipolar strain curves and the origin of strain, we believe that the large strain is contributed to the phase transition from ferroelectric phase into ergodic relaxor phase, and the low hysteresis is beneficial from the existence of ergodic relaxor phase, which should pave a way for future developing high-performance actuators.

The AP1000 reactor coolant pump is a vertical shielded-mixed flow pump, is the most important coolant power supply and energy exchange equipment in nuclear reactor primary circuit system, whose steady-state and transient performance affect the safety of the whole nuclear island. Moreover, safety demonstration of reactor coolant pump is the most important step to judge whether it can be practiced, among which software simulation is the first step of theoretical verification. This paper mainly introduces the fluid-solid coupling simulation method applied to reactor coolant pump, studying the feasibility of simulation results based on workbench fluid-solid coupling technology. The study found that: for the unsteady calculations of the pure liquid media, the average head of the reactor coolant pump with bidirectional fluid-solid coupling decreases to a certain extent. And the coupling result is closer to the real experimental value. The large stress and deformation of rotor under different flow conditions are mainly distributed on impeller and idler, and the stress concentration mainly occurs at the junction of front cover plate and blade outlet. Among the factors that affect the dynamic stress change of rotor, the pressure load takes a dominant position. Keywords: Reactor coolant pump, Bidirectional fluid-solid coupling, Safety demonstration, Steady state condition, Nomenclature

By using the designed N-rich 3,6-bis(4-methyl-1H-imidazol-1-yl)pyridazine (b4mmp) and chiral d-camphoric acid (d-cam) ligands to react with cadmium acetate, a new bulk homochiral 3D metal–organic framework [Cd2(d-cam)2(b4mmp)(DMF)]n (1) has been synthesized. Compound 1 bears an uninodal 6-connected net structure with unprecedent topology, and it has a high thermostability. Moreover, the circular dichroism spectrum and photoluminescent properties for 1 were also investigated.

Toughness and tensile strength are important mechanical properties of polymers. However, it is generally very challenging to improve the toughness without an obvious decrease in the tensile strength, and vice versa, which greatly limits the applications of polymers. Here we developed a novel hydrogen bonding-based self-assembly technology for melt blending polymers to achieve a notable improvement in toughness without an obvious decrease in the tensile strength. Thermoplastic polyurethane (TPU)/polyamide 6 (PA6) blend was selected a model composite and its elongation at break increased significantly from 1150% (0 wt% PA6) to 1350% (7.5 wt% PA6) and 1375% (10 wt% PA6), without an obvious decrease in the tensile strength. We deeply investigated the relationship between microcosmic self-assembly and macroscopic mechanical properties in polymer melt blends. It was found that the hard and soft segment groups (urethane and ester) of TPU form new hydrogen bonds with the amide group of PA6 through hydrogen-bonded self-assembly during the melt blending process, while the intrinsic hydrogen bonding structure of TPU was obviously shielded and weakened. As a result, the TPU/PA6 melt blends showed a notable improvement in toughness without an obvious decrease in the tensile strength. Since most previous self-assembly studies were carried out in solution and there was little work focused on the industrial convenient melt blending method, our study paves the way for further studies on both theoretical studies and practical applications of polymer blends.

In pressurized water reactor, fretting corrosion has become the main reason for the failure of 690TT heat exchanger tubes. The effect of temperature on the fretting corrosion behavior between 690TT tube and 405 stainless steel (SS) bar has been studied during 106 fretting cycles. The overall average coefficient of friction (COF) values descends with an increase in test temperature, while the width of worn scar becomes wider. The severest fretting corrosion happens when the test temperature is at 100 °C. The wear mechanism differs at different test temperatures, from adhesive wear at room temperature to abrasive wear and delamination at 100 °C, to abrasive wear at 200 °C. Deformation slips, high residual strain concentration, and micro-cracks are found which are disadvantageous for the further service performance of the tubes.

An approach is developed to fabricate supported AuPd nanoparticles (NPs) with high catalytic activity and good separability depending on these amino-modified polymer microspheres (Fe3O4@PS-NH2). After the careful surface modification with amino groups, the selective adsorption of these magnetic polymer carriers to p-nitrophenol (4-NP) is much available for the improvement of the catalytic activity of immobilized AuPd nanoparticles. Furthermore, the catalytic activity of the bimetallic catalyst could be tunable via controlling the surface coverage of palladium on Au nanoparticles. The catalytic activity of supported AuPd NPs (S-AuPd250%) for 4-NP reduction increased 3.78 times compared with that of isolated AuPd NPs. The catalytic activity (k/mAu) even reached 479.78 min−1 mg−1 as S-AuPd150% and was selected as the catalyst. In addition, these supported AuPd nanoparticles are easily and rapidly isolated by magnetic separation. Due to its high stability, these supported AuPd NPs could be recycled for 30 runs without any loss of catalytic activity. Thus, the high catalytic activity and easy separability of this supported AuPd NPs are efficiently combined together, which is showing great potential in nanocatalysts.

A series of environment-friendly plasticizers has been synthesized from castor oil through a mild esterification/epoxidation reaction. The modified epoxy acetylated castor oil (EACO) can plastify poly(vinyl chloride) (PVC) efficiently, even better than the commercial plasticizers dioctyl terephthalate (DOTP) and epoxidized soybean oil (ESO), in terms of in tensile strength, migration stability, solvent extraction stability and thermal stability. Specifically, the tensile strength and elongation at break of a PVC sample plastified by epoxy acetylated castor oil (EACO) were 18.5 and 10.0% higher than that of DOTP, and 13.9 and 23.8% higher than that of ESO, respectively. Volatility, migration, solvent extraction and thermal stability tests indicated that the presence of carbon-carbon double bonds and hydroxy groups reduce the compatibility of a plasticizer with PVC while the presence of epoxy groups and ester bonds can improve the plasticizing effect of the plasticizer on PVC. In addition, alkyl groups can improve the plasticizing effect on PVC while benzene rings increase the rigidity of the PVC. The design strategy based on castor oil highlights a sustainable avenue for preparing cost-effective and high-efficiency plasticizers.

Various types of knowledge and features have been explored for level set-based segmentation. On the ground, the prior knowledge and carefully-designed features perform well to identify the foreground-background contrast, which improves the performance of the segmentation method for complicated and distorted data. However, this is not the case for underwater environments, since the features available on the ground are not suitable for challenging underwater environments. Thus, underwater image segmentation currently lags behind ground-based segmentation. In this paper, novel cues and a suitable model formulation for object segmentation from underwater images are proposed. We consider the special haze effect over underwater images and extract an informative feature (transmission feature) from haze condensation. The saliency feature is also used for underwater object segmentation. Consequently, in our method, the object-background difference can be presented by these features on two levels, i.e., the edge-level transmission and region-level saliency features. These two types of features are integrated into a unified level set formulation to propose a solution that handles the challenging issues in underwater object segmentation. The experimental comparisons of our method with other methods comprehensively demonstrate the satisfactory performance of our method.

Zinc-copper-indium sulfide (ZCIS)-alloyed quantum dots are emerging as a new family of low toxic I–III–VI semiconductors due to their broad and color-tunable emissions as well as large Stokes shifts. Here, we fabricated a series of ZCIS QDs with tunable PL wavelengths and band-gap energies via a facile strategy by varying the ratio of A1–3 stock (Cu+/In3+) to the B stock (Zn2+) content. The ZnS shell was formed to improve the PL emission efficiency of the core nanoparticles and the PL emission wavelength of the resulting ZCIS/ZnS NCs gradually blue-shifted with an increase in the number of shell layers, resulting in a wide range of emissions from 800 nm to 518 nm that can be tuned by the core compositions or shell layer numbers for ZCIS/ZnS. Finally, the long-chain ligands dodecanethiol/octadecylamine on the quantum dots' surface were efficiently replaced by (3-mercaptopropyl)trimethoxysilane, thus enabling their solubility in an ionic liquid, which was confirmed via GC-MS. It also benefited for the co-dissolution of the polymers and chemical binding with other materials through the reactive silanol group, which provide stable and well-distributed ZCIS/ZnS QDs composites or surface coating by the QDs.

A set of highly dispersed copper ceria catalysts were synthesized by using the CeMOF precursor featured rich nitrogen-containing ligand. Owing to the existence of coordination interactions between metal ions and nitrogen atoms, the copper ions could be adsorbed into the pore of Ce-MOF and stabilized by the ordered nitrogen atom on the pore wall. After calcinations, the generated CuO/CeO 2 catalyst featured more well-dispersed active sites, which was evidenced by varieties of characterizations such as FT-IR, UV-vis spectroscopy, PXRD, TEM, H 2 -TPR, Raman spectroscopy and XPS. The as-synthesized CuO/CeO 2 catalysts displayed outstanding catalytic activities and stabilities for preferential carbon monoxide oxidation in H 2 -rich stream.

In the Click-Through Rate (CTR) prediction scenario, user's sequential behaviors are well utilized to capture the user interest in the recent literature. However, despite being extensively studied, these sequential methods still suffer from three limitations. First, existing methods mostly utilize attention on the behavior of users, which is not always suitable for CTR prediction, because users often click on new products that are irrelevant to any historical behaviors. Second, in the real scenario, there exist numerous users that have operations a long time ago, but turn relatively inactive in recent times. Thus, it is hard to precisely capture user's current preferences through early behaviors. Third, multiple representations of user's historical behaviors in different feature subspaces are largely ignored. To remedy these issues, we propose a Multi-Interactive Attention Network (MIAN) to comprehensively extract the latent relationship among all kinds of fine-grained features (e.g., gender, age and occupation in user-profile). Specifically, MIAN contains a Multi-Interactive Layer (MIL) that integrates three local interaction modules to capture multiple representations of user preference through sequential behaviors and simultaneously utilize the fine-grained user-specific as well as context information. In addition, we design a Global Interaction Module (GIM) to learn the high-order interactions and balance the different impacts of multiple features. Finally, Offline experiment results from three datasets, together with an Online A/B test in a large-scale recommendation system, demonstrate the effectiveness of our proposed approach., 9 pages, 6 figures, WSDM2021, accepted

In the distributed power generation systems (DPGSs), ensuring the synchronization with the utility grid is crucial for the stable operation of grid-connected systems. Among various synchronization techniques, the power-based phase-locked loop (pPLL) has gained much attention due to its relatively simple implementation of the phase detector, extraordinary harmonic filtering capacity and robustness even under large grid variations. However, this kind of PLL suffers from an inherent problem called "double-frequency oscillation". The aim of the study is to review and compare the existing pPLLs. According to the difference in coping with this drawback, pPLL can be divided into two categories: cancellation with in-loop filter (CIF) and cancellation with opposite component (COC). Working principles and main characteristics of different pPLLs are then discussed. At last, some simulations and discussions are provided.

In recent years, the grid-connected inverter and its control in the weak grid case have drawn wide attentions. For the grid synchronization, a phase-locked loop (PLL) is usually needed. Typically, the delay-based PLL is widely used in the single-phase application. However, when a large grid impedance exists at the point of common coupling (PCC) in the weak grid case, the inverter with the delay-based PLL cannot work well or even be unstable. Hence, this paper aims at proposing a robust method to improve the delay-based PLL performance with the large grid impedance. First, the system modelling is established. Then, an additional grid current feedforward is proposed to add into the delay-based PLL. It has been shown that the proposed method equivalently adds an adjustable impedance in series to the original inverter output impedance, and improves the behaviors in weak grid cases. The selection of parameters has been emphasized for maintaining the high robustness. At last, comparative waveforms have verified that the single-phase inverter with the proposed method can perform well even with the large grid impedance.

Enamel coating is a novel type of coating for the corrosion protection of reinforcement in concrete. Recently, improved enamel coating was achieved using low-temperature sintering. This stu...

The effect of bromide and iodide on the transformation of humic acid (HA) and algal organic matter (AOM), and the formation of disinfection by-products (DBPs) during UV/chlorination were investigated. Experimental results indicated that the halides effectively inhibited mineralization, with multiple changes in organic molecule transformation due to differences in formation and speciation of reactive halogen species and free halogen. As a consequence, bromide and iodide also played important roles in DBP formation. The DBP yields in HA-containing water during UV/chlorination decreased in the order of iodide loaded > freshwater ≫ bromide loaded, whereas DBP formation in AOM-containing water decreased remarkably with halides added (freshwater > bromide loaded ≫ iodide loaded) at high UV fluence. Moreover, Pearson correlation analysis exhibited weaker correlation between DBPs and water parameters in AOM-containing water, while DBPs in HA-containing water exhibited better correlation with water parameters. For both simulated waters, the theoretical toxicity was calculated and peaked in bromide-containing water, whereas the calculated toxicity in iodide-containing water was comparable or slightly higher than that in freshwater. Therefore, UV/chlorine treatment may achieve good quality water with reduced DBP-associated toxicity in freshwater or iodide-containing water (iodide only), but careful consideration is needed when purifying source waters containing bromide (bromide only), especially for AOM/bromide-containing water.

In the renewable power generation systems, ensuring the synchronization of the inverter and the power grid is crucial for the stable operation of grid-connected inverters. Nowadays, the phase-locked loop (PLL) technology has become a widely used grid synchronization method because of its simple implementation and robustness under various grid conditions. Even though a lot of PLLs have been proposed, the overview and comparative analysis of multiple PLLs can be helpful for the practical applications. In addition, the weak grid condition is a great challenge for the system. Therefore, this study firstly presents an overview of the existing PLLs together with their general structures and basic working principles. Depending on the implementation of the phase detector, the PLL can be divided into three categories: power-based PLL (pPLL), orthogonal-signal-generator-based PLL (OSG-PLL) and adaptive-filter-based PLL (AF-PLL). Then, from the above classification, seven typical single-phase PLLs are selected for further study. Finally, some test results are given, and a comprehensive evaluation of the selected PLLs under different grid conditions is conducted.

Isothermal compression testing of 23% Cr low nickel duplex stainless steels, with different Mn concentrations, was investigated in the temperature range of 1173–1423 K, the strain rate range of 0.01–10 s−1 and with a height reduction of 70%. Increasing the Mn content from 6.3 to 14.1% affected the deformation dynamic softening behaviour of flow curves at lower temperature and higher strain rate. It was also observed that increasing the deformation stain rate contributed to flow softening, and was caused by dynamic recrystallization (DRX) as a function of Mn addition. Deformation microstructure analysis demonstrated that more complete austenite phase DRX occurred with 10.3% Mn addition than that with 6.3% Mn addition at 1 s−1, but an excessive Mn content of 14.1% was unfavourable due to the increase of austenite fraction and stacking fault energy enhancement. Increasing the strain rate to 10 s−1 promoted austenite phase DRX at 1323 K with the Mn addition under large strain. Meanwhile, the ferrite phase DRX occurred at 1173 K/1–10 s−1 with 6.3% Mn, and was weakened with higher Mn addition. Compared to the 6.3% and 14.1% Mn, continuous DRX occurred at 1323 K/1 s−1 with 10.3% Mn, due to the larger fraction of high angle misorientations. The values for the activation energy and Zener–Hollomon parameter decreased with Mn addition from 6.3 to 10.3%, and then increased with a higher Mn addition of 14.1%, indicating that a proper content of Mn addition can reduce the thermal deformation resistance and promote DRX. The constitutive equations for different Mn addition alloys were developed using a hyperbolic sine equation. Processing maps with different Mn addition for the strains of 0.3, 0.6 and 1.2 were established. The 10.3% Mn content sample corresponded to the lowest instability region, implying that the workability was improved with the middle Mn addition.

The adsorption of three haloforms (CHCl3, CHBr3 and CHI3) was studied using five different granular activated carbons (GACs), including acid washing carbon, coconut-shell carbon, briquetting carbon, coal and fibred carbon. The adsorption isotherms were fitted well using Freundlich model, and adsorption kinetics were fitted well using pseudo-second-order model. CHI3 was adsorbed most efficiently, followed by CHBr3 and CHCl3. Fibred carbon was the most efficient adsorbent for the studied haloforms. The adsorption capability of each GAC was calculated using the pseudo- second-order model which was then correlated to adsorbent properties. Generally, the surface area of GAC did not highly correlate to the amount of haloform adsorption. Highly positive correlations with methylene blue and iodine number were observed for CHBr3 and CHI3 adsorption capacity, but not for CHCl3. Micropores were correlated with CHCl3 adsorption capacity. Moreover, three models, including intraparticle diffusion, Byod kinetic and diffusion-chemisorption were used to illustrate the mechanisms of haloform adsorption mechanism. Film diffusion was determined to be the rate-limiting process and haloforms were adsorbed via chemical adsorption. The results of adsorption rate and capacity are crucial for practical application of haloform removal via GAC process.

Fretting corrosion fatigue behaviour of Alloy 690 was investigated in 285 °C pure water under different normal loads. With increasing the normal load applied, the fatigue life decreased, more severe surface damage and subsurface deformation were observed. The effects of normal loads on crack characteristics on the longitudinal sections across the fretting fatigue scars and corrosion fatigue fractures were examined. Possible influence of the normal loads on initiation and propagation mechanisms of the fretting corrosion fatigue cracks of Alloy 690 in high-temperature pure water are discussed.

Booster chlorination has been applied by many utilities for better chlorine-residual maintenance. In this paper, a new water-age based method for optimal location and dosage of booster disinfection has been proposed, as well as an uncertainty analysis of chlorine residuals. Chlorine-age, a novel indicator of water quality, is firstly introduced based on water age. By minimizing the total chlorine-age of nodes in a water distribution network (WDN), a new model for optimal booster location is proposed. The chlorine-age based model is independent of chlorine-decay simulation, and therefore avoids the complexity of obtaining kinetic parameters and prevents misleading results caused by inaccurate simulation of chlorine residuals. The uncertainties of chlorine residuals increase along with the distance and time consumption for delivering water. In this study, chlorine-age is employed to measure the uncertainties of nodal residuals, and optimal chlorine dosage is calculated considering the uncertainties. The proposed method has been tested on an example network and a real-life network to illustrate its validity and applicability. The results have shown that the method is feasible and reliable in practical application.

The influence of Mn addition on σ-phase precipitation kinetics and pitting corrosion of Fe-22Cr-1.9Ni-2.3Mo-0.2N-xMn low nickel type duplex stainless steel was investigated by medium- and high-temperature aging treatments of 600 °C and 800 °C. The microstructure analysis showed that the fine rod-shaped and coarsening dendritelike σ-phase precipitates formed at 600 °C and 800 °C, respectively, and the precipitate growth with the higher temperature was accelerated due to the partition of Mn, but Mn is not a strong σ-phase forming element like Cr, Mo during aging treatment at these two temperatures. At an early aging time of 800 °C, more precipitated nuclei with more Mn addition promote refinement of σ precipitates in later aging time. The kinetic behavior at 600 °C and 800 °C is related to diffusion-controlled growth of σ phase, and the σ-phase nucleation and growth are enhanced with more Mn addition and higher aging temperature due to a faster Mn diffusion rate. The difference in precipitation morphology for two aging temperatures was attributed to the different nucleation modes caused by kinetics parameter n variation. Increasing the aging temperature from 600 °C to 800 °C increased the susceptibility to pitting with higher Mn addition due to faster σ-phase precipitation kinetics.

Fretting fatigue behavior of Alloy 690 in room-temperature (RT) air and high-temperature pure water was investigated under the condition of a normal load of 100 N. Fretting fatigue life in high-temperature water reduced by about 30% compared to that in RT air due to combined effects of high-temperature water and highly localized tangential stress. The main fatigue cracks were inclined to initiate in the crevice region along the contact edges in high-temperature water, but none was observed in RT air. Related mechanisms of fretting corrosion fatigue failure of Alloy 690 in high-temperature water are discussed.

This paper deals with a class of fuzzy cellular neural networks with multi-proportional delays. By applying the contraction mapping fixed point theorem and differential inequality techniques, a set of easily verifiable sufficient conditions are established for the existence and global attractivity of a unique pseudo almost periodic solution for the model, which improve and supplement previously known researches. Moreover, a numerical example is given to illustrate the feasibility and application of the obtained results.

The evolution of microstructure and microhardness was studied in a commercial tungsten-25% rhenium (mass fraction) (W-25Re) alloy processed by the high pressure torsion (HPT) procedure under a pressure of 7.7 GPa up to 10 revolutions at different temperatures. The results show that the samples processed by 10 revolutions at room temperature could have the smallest grain size at around 0.209 μm. High saturation hardness (HV ∼1200) could be achieved after the rapid strengthening stage for samples processed by 10 revolutions both at room temperature and at 573 K. Microstructural observation and analysis from Hall–Patch relationship could reveal that grain refinement and grain boundaries strengthening are the main factors of hardening mechanism in W-25Re alloy. It is also demonstrated that sintered W-25Re sample may have brittle phase separation phenomenon after HPT processing.

Due to the shortage of natural materials, using steel slag (SS) as replacement for natural sand to manufacture mortar has attracted worldwide attention and becomes a promising technology. This study aims at employing SS as fine aggregate for natural sand substitute in cement mortar synthesis. The measurement of expansion value generated by fine SS aggregate was performed by autoclave test. On the basis of further tests, the optimum content of SS fine aggregate was 25%. The autoclave experiment results indicate that the mortar bar was seriously damaged with higher dosages of SS fine aggregate. The X-ray diffraction (XRD) technique was offered to identify the mineralogical phases of the autoclaved SS. Additionally, this work investigated the printability of 3D printing mortar by assessing its fluidity, slump and mechanical strength. The printing mortar mixed with 25% SS was used in the printing of an actual 3D structure, demonstrating its feasibility to be used in 3D printing field. The microstructure and elements distribution were characterized by scanning electron microscopy (SEM) and the energy dispersive spectroscopy (EDS) techniques. The results showed that it is feasible to incorporate SS in 3D printing mortar, which contributes to the improvement of working properties and the enhancement of mechanical strength. This study provides a novel 3D printing SS mortar with good economic and potentially great environmental benefits.

Vitreous enamel is a durable inorganic material that has been extensively used in our daily life for decoration and protection of the metallic substrates. It guarantees optimal corrosion protection to the covered substrates, but, on the other side, the brittle nature of its matrix highly limits its application. Here new enamel coatings were synthesized by adding silicon nitride with the contents of 0, 1.5, 2.5, 3.5, 5, and 7.5 wt%. Scanning electron microscope (SEM), X-ray diffraction (XRD), micro indentation, impact, thermal shock, and potentiodynamic polarization tests were conducted to evaluate the microstructure and engineering properties of the studied enamel coatings. Results showed that the addition of silicon nitride leads to a high internal porosity of the enamel coating, which consequently improves the resistances against cracking under indentation and impact loads. Especially, the silicon nitride modified enamel coatings were found to survive more than 100 cycles of thermal shocks. Despite the porosity rising, the addition of silicon nitride enhanced the corrosion resistance of enamel coatings at early immersion age, and all enamel coatings kept around 10 times lower corrosion rate than that of the uncoated steel at later immersion age. The findings of this work may provide a solution to steel protection against harsh high-temperature exposure and corrosive environments.

Lead-free (1− x )(0.75Bi 0.5 Na 0.5 TiO 3 –0.25Bi 0.5 K 0.5 TiO 3 )– x BiAlO 3 (BNT–BKT–100 x BA, x =0–0.10) ceramics were prepared by two-step sintering method and their phase structure, micro morphology and electrical properties were systematically investigated. X-ray diffraction analysis indicates a pure perovskite phase for x ≤0.06 as well as a structural evolution from a tetragonal toward a pseudocubic phase. Transmission electron microscopy study of the x =0.04 composition reveals the existence of antiferroelectric phase with a 0 a 0 c + oxygen octahedron tilting which is in the form of nano-domains. Polarization-electric field and current-electric field hysteresis loops demonstrate that the increase of BA concentration destroys the ferroelectric order and strengthens antiferroelectric order. A much enhanced energy storage density of 1.15 J/cm 3 and efficiency of 73.2% is achieved under 105 kV/cm at x =0.06. In addition, its energy storage property is found to depend weakly on temperature within the measurement range of 25–150 °C.

The impact fretting wear has largely occurred at nuclear power device induced by the flow-induced vibration, and it will take potential hazards to the service of the equipment. However, the present study focuses on the tangential fretting wear of alloy 690 tubes. Research on impact fretting wear of alloy 690 tubes is limited and the related research is imminent. Therefore, impact fretting wear behavior of alloy 690 tubes against 304 stainless steels is investigated. Deionized water is used to simulate the flow environment of the equipment, and the dry environment is used for comparison. Varied analytical techniques are employed to characterize the wear and tribochemical behavior during impact fretting wear. Characterization results indicate that cracks occur at high impact load in both water and dry equipment; however, the water as a medium can significantly delay the cracking time. The crack propagation behavior shows a jagged shape in the water, but crack extended disorderly in dry equipment because the water changed the stress distribution and retarded the friction heat during the wear process. The SEM and XPS analysis shows that the main failure mechanisms of the tube under impact fretting are fatigue wear and friction oxidation. The effect of medium(water) on fretting wear is revealed, which plays a potential and promising role in the service of nuclear power device and other flow equipments.

The impact fretting wear behavior of a 690 alloy tube affected by low-impact cycling kinetic energy was investigated. The Inconel 690 alloy specimen was clamped by cantilever and simple supported beam structures for support. The interface response was affected by the clamping situation, and material wear was affected by the change in the interface response. The energy loss, contact force versus time and frequency, energy absorption, and deformation of the material (thin wall tube) during impact were analyzed. The worn surfaces and cross-sectional morphologies were observed with an optical microscope and a 2D surface profiler to analyze the impact fretting wear mechanism under the two support structures. In the two clamping structures, wear decreased when the span increased, and material wear showed a high correlation with the peak impact force and absorbed energy. The wear mechanism of the alloy 690 specimen was delamination.

Oxidized and non-oxidized SiC particulates were mixed with Al powder respectively and the two kinds of mixed powders were consolidated at 250°C by equal channel angular pressing and torsion (ECAP-T), which belongs to severe plastic deformation. The interfacial bondings of as-consolidated composites were characterized by SEM images, corrosion morphology and fracture morphology. The results show that after severe plastic deformation, the interfacial bonding between non-oxidized SiC and Al is a kind of mechanical bonding and the consolidation is not firm enough so that the composite has a weak corrosion resistance and its tensile sample has a brittle fracture. However, the composite containing oxidized SiC has a dense microstructure, high corrosion resistance, ductile fracture due to the metallurgical interface.

Supporting density of Au nanoparticles on the surface of magnetic carrier was carefully investigated because of its great effect on the catalytic activity. Micro-sized magnetic polymer beads (Fe 3 O 4 @PMMA) were employed to immobilize Au nanoparticles due to its easy surface modification and rapid magnetic separation. By controlling the supporting density and particles size of Au NPs, the catalytic activity of immobilized Au NPs in reducing p -nitrophenol was effectively improved. When 10 nm Au NPs were employed to be immobilized on the magnetic carrier with the density of 4292 μg/g, the catalytic activity of Fe 3 O 4 @PMMA/Au even approached to that of isolated Au NPs, which indicated that suitable supporting density of Au NPs might compensate some drawbacks of heterogeneous catalysts. It meant that the catalytic activity of Au NPs was not damaged even after its immobilization. Furthermore, this magnetic supported catalyst could be easily separated and recycled. After 23 runs of recycling, no significant loss of catalytic activity was found. This catalyst also performed high catalytic activity in continuous-flow column reactors, which showed much potential in practical application.

This study aimed to investigate the impact fretting wear behavior of thin-walled tubes under different support interfaces with a novel impact wear testing rig. A tube/cylindrical contact model was used, and V-shaped fixtures with varied angles were applied. The 304 stainless steel tubes with varied lengths and a GCr15 bearing steel roller were used as the test materials. The interface deformation, impact energy absorption, and damage behavior were investigated in terms of the influence of the support angle, tube length, and the initial impact energy. After the test, the wear mechanism of the tube was investigated. The results showed that under the same lengths, when the support angle increased, the deformation displacement increased, but the contact peak force, energy absorption, and the area of worn scars decreased. The increasing length increased the contact force, energy absorption ratio, and serious damage but reduced the deformation. The increasing kinetic energy of the initial impact will decrease the energy absorption ratio. Contact fatigue spalling and oxidation are the wear mechanisms of the impact fretting wear of 304 stainless steel.

In this study, quasi-static tensile tests of high-strength steel rebars, after exposure to 20°C–1,300°C, and dynamic tensile tests at a strain rate of up to 0.25 s−1, after exposure to 20°...

The permanent magnet synchronous machine (PMSM)with variable flux hybrid rotor(VFHR) is a hot topic in reliability-critical application like aeronautical servo/drive systems. It is of great benefits to deepen the working mechanism of the permanent magnet synchronous machine with variable flux hybrid rotor for its anti-short capacity by analyzing the transient electromagnetic performance of interturn short faults in PMSM with VFHR. In this paper, the structure of PMSM with VFHR is adopted for analyzing the electromagnetic performance, the interturn short fault in PMSM with VFHR is modelled and transient magnetic analysis of no-load interturn short fault in PMSM with VFHR is carried out based on the model proposed in section II. The demagnetizing field of the interturn short fault is analyzed by comparing the electromagnetic performance before and after the interturn short fault occurs.

Fuel-cell can be a competitive energy device in the future due to the features of zero emission and high efficiency. Generally, fuel-cell will be used with other energy storage devices because of its slow dynamic response. This paper presents an optimized energy management system for fuel-cell/battery hybrid power unmanned aerial vehicle(UAV). The fuel-cell/battery hybrid system consists of fuel-cells, lithium-ion batteries, along with associated dc/dc converters. Energy management systems are used in order to distribute demand power to power sources (fuel-cell and lithium-ion batteries). State-machine strategy is proposed because of limit calculated ability of UAV and easy for engineering implementation. This paper proposed corresponding power control method for fuel-cell and lithium-ion batteries. In order to minimize the weight of hybrid power system, we take the maximum output power of fuel cell as the input variable, establish the weight model of fuel cells and batteries, found the optimal sizing of FC/BAT. This hybrid power system simulation model has been built on Simulink. The energy management strategies have been tested in a full flight load profile. Results of simulation verified that energy management could distribute demand power reasonable and maintain voltage of DC-bus stable.

Here we report on a miniaturized optical interferometer in one fiber based on two mismatched nodes. The all-fiber structure shows stable performance of temperature and humidity sensing. For temperature sensing in large ranges, from 40 to 100 &deg, C, the sensor has a sensitivity of 0.24 dB/&deg, C, and the adjusted R-squared value of fitting result reaches 0.99461 which shows a reliable sensing result. With carbon nanotubes coating the surface of the fiber, the temperature sensitivity is enhanced from 0.24561 to 1.65282 dB/&deg, C in a small region, and the performance of humidity sensing becomes more linear and applicable. The adjusted R-squared value of the linear fitting line for humidity sensing shows a dramatic increase from 0.71731 to 0.92278 after carbon nanotube coating, and the humidity sensitivity presents 0.02571 nm/%RH.

Although the immobilization of gold nanoparticles (Au NPs) on the support is a conventional method for preventing them from aggregation and improving their separability at the cost of activity loss, herein, we developed a facile method to prepare supported Au NPs with the higher catalytic activity and better separability due to the selective adsorption of its functional surface. Firstly, the multi-functional carriers (amino-modified magnetic microspheres) were synthesized to immobilize Au NPs. Depending on its surface adsorption towards the reactant (p-nitrophenol), this carrier could greatly improve the mass transfer between p-nitrophenol (4-NP) and Au NPs resulting in the improvement of catalytic activity of supported Au NPs. The catalytic activity of supported Au NPs is increased more than 6.65 times compared with that of isolated Au NPs. Then, the effects of the particle size and supporting density of Au NPs on the catalytic activity were also investigated. Turnover frequency value of supported Au NPs (3.8 nm) reaches 16,000 h−1 when its surface density is controlled to 2211 μg g−1. Furthermore, the catalyst of Au/Fe3O4@PS-NH2 showed excellent catalytic activity when various nitrobenzene derivatives were employed as substrates. Remarkably, these supported Au NPs could be easily isolated by magnetic separation in 30 s. This catalyst could be recycled for 45 times without any loss in catalytic activity. The high catalytic activity and easy separability of this supported Au NPs make it much potential in large-scale application.

Bacterial cellulose (BC) features a nanofibrillar network structure that can provide a good template for quantum dots (QDs), to overcome the fluorescence quenching-effect of QDs in polymer composites. Here, we fabricated novel fluorescent aerogels with tunable emission by covalently binding environmentally-friendly ZnS(CuInS2)/ZnS core-shell quantum dots along the nanofibrillar BC. A new ligand of 3-(mercaptopropyl)trimethoxysilane allows QDs to transfer from toluene to alcohol solvent and stably bind to the BC. After supercritical CO2 drying, the resulting BC-QDs aerogels maintain the porous nanofibrillar morphology of BC with ultra-light-weight, the QDs are well-distributed along the BC fiber surfaces without aggregation. The emission wavelength can be tuned in a wide range from 470 to 750 nm by simply adjusting the QDs core component or shell layers. This work provides a new approach for fabricating QDs-polymer hydrogels and aerogels with well distributed QDs via chemical binding that potential as smart sensor, catalysis, and 3D display applications.

In recent years solid Li+ conductors with competitive ionic conductivity to those of liquid electrolytes have been reported. However, the incorporation of highly conductive solid electrolytes into the lithium-ion batteries is still very challenging mainly due to the high resistance existing at the solid-solid interfaces throughout the battery structure. Here, we demonstrated a universal interfacial modification strategy through coating a curable polymer-based glue electrolyte between the electrolyte and electrodes, aiming to address the poor solid-solid contact and thus decrease high interfacial resistance. The liquid glue exhibits both great wettability as well as chemical/electrochemical stability to most of the electrodes, and it can be easily solidified into a polymer electrolyte layer through a "post-curing" treatment. As a result, symmetric Li batteries with the glue modification exhibit much smaller impedance and enhanced stability upon plating/stripping cycles compared to the batteries without glue modification. The all-solid-state Li-S batteries with glue modification show significantly enhanced performances. The strategy of developing glue electrolytes to improve the electrode-electrolyte interface contact provides an alternative option for improving many other solid-state batteries. Accepted version

UAVs have the advantages of long endurance, remote operation, high load capacity, high reliability, etc. Its airborne energy power system is the key core technology of the aircraft platform. Based on the research on the electrical power supply system of UAVs, a starter/generator module for the hybrid power system is designed in this paper. This module has functions such as engine electric starter, power generation, secondary power supply, uninterrupted circuit, status monitoring, fault detection and so on. Through the modeling and simulation of permanent magnet brushless DC motor system and the hardware and software circuit design based on TMS320F28035 control chip, the Principle Prototype of starter/generator module was developed. The experimental results show that the module can work normally and achieve its function. That means hybrid UAV starter/generator module has good performances.