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The carbonation process in alkali-activated slag cement concrete is more complicated. This paper reviews the research progress of carbonation resistance of alkali-activated slag cement concrete at home and abroad and summarizes the existing research on carbonation. The focus is on the carbonation mechanism, test methods, influencing factors and the effect of carbonation on the performance of alkali-activated slag cement concrete. The problems existing in the current research on the anti-carbonation property of alkali-activated slag cement concrete and the issues for further research are proposed.

Based on the SEIR model, which takes into account prevention and control measures, prevention and control awareness, and economic level and medical level indicators, this paper proposes an infectious disease model of “susceptible-exposed-infected-removed-asymptomatic-isolated” (short for SEIR-AQ) to assess and predict the development of the COVID-19 pandemic with different prevention and control strategies. The kinetic parameters of the SEIR-AQ model were obtained by fitting, and the parameters of the SEIR-AQ model were solved through the Euler method. Furthermore, the effects of different countries’ prevention and control strategies on the number of infections, the proportion of isolation, the number of deaths, and the number of recoveries were also simulated. The theoretical analysis showed that measures such as isolation for prevention and control and medical tracking isolation had a significant inhibitory effect on the development of the COVID-19 pandemic, among which stratified treatment and enhanced awareness played a key role in the rapid regression of the peak of COVID-19-infected patients. Conclusion of the Simulation. The SEIR-AQ model can be used to evaluate the development status of the COVID-19 epidemic and has some theoretical value for the prediction of COVID-19.

In this work, the effect of nitric acid modification on activated carbon (AC) and on properties of Mn/AC ozone catalysts was studied. In addition, the ozone catalytic performance of toluene on catalysts modified with different concentrations of nitric acid was investigated. It was found that nitric acid could greatly increase the oxygen content of the AC support and the acidic oxygenated groups content of the catalysts. The acid-modified catalysts had a higher Mn loading compared to an unmodified sample, and the overall valence of the Mn element increased with the degree of modification. The Mn/AC catalysts modified by fuming nitric acid had a higher toluene conversion rate (84–87%) than the concentrated nitric acid-modified (conversion rate of 63%) and unmodified catalysts (conversion rate of 61%). Among these catalysts, the sample with fuming nitric acid of 43 vol% in acetic anhydride during modification had the highest CO2 and ozone conversion rates compared to catalysts with higher (50 vol%) or lower (33 vol%) nitric acid modification concentration. Furthermore, a new toluene catalytic ozonation intermediates conversion and accumulation mechanism at low temperature is proposed.

The adhesive strength in a coating-substrate system is of primary importance for the coating lifetime in service. However, the underlying mechanism is not fully understood due to the complex internal structure of composite coatings. In this study, the effect of substrate roughness on the adhesive strength of WC-Co coatings was investigated by experiment and simulation. Results show that the adhesive strength is significantly affected by the roughness. In the case of the Ra＜2 μm, the adhesive strength is approximately 35–46 MPa. When the Ra is 4 μm, the adhesive strength increases to nearly 60 MPa. A finite element model was developed to correlate the roughness with adhesive strength. It is found that the predicted values are well consistent with the experimental data. In addition, with the increase of the roughness, the residual stress would be changed from concentrated state to widespread state, which decreases the critical stress to result in crack propagation. That’s why a larger roughness can cause a higher adhesive strength. This study gives understanding on the mechanism of adhesive strength affected by roughness, which contributes to the parameter optimization with better performance.

The improvements of cyclability and rate capability of lithium ion batteries with spinel LiMn2O4 as cathode are imperative demands for the large-scale practical applications. Herein, a nickel (Ni) and magnesium (Mg) co-doping strategy was employed to synthesize LiNi0.03Mg0.05Mn1.92O4 cathode material via a facile solid-state combustion approach. The effects of the Ni-Mg co-doping on crystalline structure, micromorphology and electrochemical behaviors of the as-prepared LiNi0.03Mg0.05Mn1.92O4 are investigated by a series of physico-chemical characterizations and performance tests at high-rate and elevated-temperature. The resultant LiNi0.03Mg0.05Mn1.92O4 has the intrinsic spinel structure with no any impurities, and exhibits an elevated average valence of manganese in comparison to the pristine LiMn2O4. Owing to the Ni and Mg dual-doped merits, the LiNi0.03Mg0.05Mn1.92O4 sample demonstrates a robust spinel structure and high first discharge specific capacity of 112.3 mAh g−1, whilst undergoing a long cycling of 1000 cycles at 1 C. At a high current rate of 20 C, the capacity of 91.2 mAh g−1 with an excellent retention of 77% is obtained after 1000 cycles. Even at 10 C under 55 °C, an excellent capacity of 97.6 mAh g−1 is also delivered. These results offer a new opportunity for developing high-performance lithium ion batteries with respect to the Ni-Mg co-doping strategy.

Tungstotellurate(VI)-coated magnetic nanoparticles (MNP) were prepared by immobilization of tungstotellurate(VI) salt onto the surface of branched polyethyleneimine (PEI)-modified magnetic nanoparticles via electrostatic interaction. The structure and composition of TeW@MNP were confirmed by characterization with FT-IR, EDS and SEM. The obtained TeW@MNP composite had proven to be a promising adsorbent for the adsorption of ovalbumin in egg whites. Approximately 0.5 mg of TeW@MNP composite gave rise to a maximum adsorption efficiency of 91.6% for 100 μg mL–1 ovalbumin in 200 mL of sample solution at pH 4.0 (BR buffer). The retained ovalbumin was readily recovered by using 0.1% SDS as a stripping reagent, providing a recovery of 98.1%. The adsorption behavior of ovalbumin fitted Langmuir model, corresponding to a theoretical adsorption capacity of 373 mg g–1. The TeW@MNP composite was practically applied to the selective isolation of ovalbumin from egg whites, and SDS-PAGE assay results clearly indicated that the ovalbumin with high purity was obtained. The above experimental results illustrated the great application potentials of polyoxometalates for protein isolation and purification and extended the application scope of polyoxometalates in life science field.

The hierarchical organization of building blocks is an important characteristic of self-assembly. Herein, we report a series of triangular hierarchical assemblies formed by C3-symmetric 5,10,15-triethyl-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazole-2,7,12-tricarbaldehyde (M1) on the graphite surface. The molecule assembles into a hexagonal array on the graphite surface at room temperature with a trimeric assembly motif as the basic building block of the hierarchical assembly. With the increase of annealing temperature, the sizes of triangles in hierarchical assemblies vary from large to small with the presence of antiparallelly arranged molecular dimers as building blocks at the triangular boundaries. The hierarchical-order-level-dependent intermolecular interaction and molecule–substrate interaction were modeled, and the entropy contributions of alkyl substitution at different temperatures were proposed to account for the observed structural evolution process. This work provides a new example of hier...

In this study, humic acid coated biochar (HA-BC) and chitosan were combined to prepare an adsorbent with enhanced reactivity for the removal of ciprofloxacin (CIP). With initial CIP concentrations of 250 mg/L, the maximum adsorbed amount was 154.89 mg/g. Removal rates reached equilibrium after 12 h, obeying the pseudo second-order kinetic model. Adsorption isotherm data was better fitted to the Langmuir isotherm model. The sorption capacity of humic acid-biochar/chitosan hydrogel beads (HBCB) decreased by 11.42%, 6.66%, 9.32%, and 23.92% in the presence of NaCl, NaNO3, Na2SO4, and Na3PO4, respectively. A complex mechanism was found to be responsible for the adsorptive removal of CIP including, hydrogen bonding, π-π electron donor–acceptor (EDA) interactions and hydrophobic interactions. After four regeneration steps, sorption capacity remained sufficient (61.23 mg/g). These removal results indicate that HBCB is durable and effective for long term CIP removal.

The three-dimensional sono-elasticity method recently developed by Zou et al. [1,2] is employed to model the coupled acoustic radiation of the submarine induced by the propeller-shaft system. Vibration isolators are widely used to control the vibration and acoustic radiation induced by machines. Nevertheless, they are not seen in the control of propeller-shaft-hull coupled vibration and acoustic radiation induced by the propeller-shaft system. The relationship between the stiffness of isolator for shaft and the characteristic frequency of coupled acoustic radiation is clearly identified. The mechanism of how the stiffness of isolator for shaft affects the coupled acoustic radiation is discussed. Furthermore, the influence of the input impedance of the base for thrust bearing upon the coupled acoustic radiation is investigated. A new vertically symmetrical base with high input impedance for thrust bearing is proposed. To realize impedance mismatch, the isolator with low stiffness and the new base for thrust bearing are applied to the propeller-shaft-hull system. The coupled acoustic radiation of the submarine induced by the propeller-shaft system is effectively reduced.

Background Fire-needle acupuncture, an important kind of acupuncture therapy, has been clinically used to treat upper limb spastic paralysis (ULSP) after stroke. Clinical experience has indicated that fire-needle acupuncture treatment takes less time, requires fewer visits, and has more rapid results and fewer side effects compared to chemical medicine alternatives. This study will evaluate the effects of fire-needle acupuncture for ULSP in the context of standardized clinical research and provide high-quality data to inform clinical procedures and future study design. Methods/Design A randomized controlled trial will be carried out to evaluate the effects of fire-needle acupuncture therapy in patients with ULSP from stroke. ULSP patients (n = 120) will be recruited at Changhai Hospital in Shanghai, China. Patients will be randomly divided into three groups, including fire-needle acupuncture group (FAG), filiform-needle acupuncture group (FFAG) and rehabilitation treatment group (RTG). During the 3-week treatment, the FAG will be treated every two days, while FFAG and RTG will be treated 5 d in a row and then rest for 2 d. The Simplified Fugl-Meyer Motor Function Scale and Modified Ashworth Scale will be used as the primary outcome measures. Statistical analysis will be conducted by an independent statistician. Discussion Through this study, the utility of fire-needle acupuncture in treating ULSP after stroke will be tested, and some specific claims of fire-needle acupuncture therapy will be evaluated, such as relieving spasm and muscular tension, improving activities of daily living, rapidity of response and less frequency of treatment compared with other treatments. Trial registration Chinese Clinical Trial Registry (identifier: ChiCTR-IOR-17013875; registration date: 28 December 2016).

Given the increasing use of glass mat-reinforced thermoplastic (GMT) composites, the formability of GMT sheets is currently a topic of research. A new sheet forming process for solidified GMT was developed. In this process, a GMT sheet was sandwiched by dummy metallic sheets during deep drawing. The dummy metallic sheets acted as protective materials and media for heating the GMT sheet. In this study, tensile tests of GMT specimens were carried out under different temperature conditions. The effect of temperature on the tensile deformation was analyzed. The effect of temperature on the deep drawing process of GMT sheets with dummy sheets was further investigated. Finite element method (FEM) was conducted to simulate the deep drawing process. In the drawing force rising stage, the law of drawing force with the depth of the drawing was analyzed using FEM and experiments.

The luminescence mechanism of Nd3+: B2O3-Al2O3-CaO glasses with different amounts of B2O3 were investigated based on their electron paramagnetic resonance spectra and luminescence properties. The results of the echo-detection field sweep exhibited two different maxima indicating that Nd3+ ions occupy two different sites. 27Al and 11B signals in two-dimensional hyperfine sublevel correlation spectra were observed in the (+, +) quadrant, indicating that both 27Al and 11B are located in the second or higher order Nd3+ coordination shell. In addition, the fraction of the 11B nucleus present in the Nd3+ coordination sphere increased with an increase in the amount of B2O3. The continuous changes in the hypersensitive transition intensity and luminescence properties are strong indicators for the change in the Nd3+ coordination environment.

ZSM-5 (core)/SAPO-11 (shell) composite molecular sieve was synthesized by the hydrothermal method in order to combine the advantages of ZSM-5 and SAPO-11 materials for the methylation of naphthalene with methanol. For comparison, the catalytic performance of mechanical mixture of ZSM-5 and SAPO-11 was also evaluated. The characterization results proved that ZSM-5/SAPO-11 composite has a core-shell structure. The pore size of the composite was between that of ZSM-5 and SAPO-11. The composite had fewer acid sites than ZSM-5 and mechanical mixture, but more acid sites than SAPO-11. The experimental results indicated that the composite exhibited good catalytic performance in the methylation of naphthalene with methanol.

Using an ultrasonication-assisted liquid exfoliation method, we have synthesized PtS2 nanosheets with good reproducibility. Herein, intrinsic peroxidase-like activity was for the first time demonstrated for PtS2 nanosheets, which can catalyze H2O2 oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to generate a colored solution. The catalytic mechanism of PtS2 nanosheets was investigated, which indicated that acceleration of the electron transfer between TMB and H2O2 was the main reason for the peroxidase-like activity of PtS2 nanosheets. Based on these observations, we exploited PtS2 nanosheets integrated into dopamine-functionalized hyaluronic acid (HA-DA) hydrogel microspheres by droplet microfluidics to construct PtS2 nanosheet– and PtS2@HA-DA microsphere–based sensors for highly sensitive determination of H2O2. When coupled with glucose oxidase, we further developed two glucose sensors based on the above two methods. Among them, the linearity of the PtS2 nanosheet–based spectrophotometry was in the range of 0.5 to 150 μM and the limit of detection as low as 0.20 μM. The linearity of the microsphere-based colorimetry was in the range 200 to 12,000 μM with a detection limit of 29.95 μM. Both of the glucose sensors can be applied to the determination of glucose in human serum with reliable results and reproducibility.

Visual navigation is developing rapidly and is of great significance to improve agricultural automation. The most important issue involved in visual navigation is extracting a guidance path from agricultural field images. Traditional image segmentation methods may fail to work in paddy field, for the colors of weed, duckweed, and eutrophic water surface are very similar to those of real rice seedings. To deal with these problems, a crop row segmentation and detection algorithm, designed for complex paddy fields, is proposed. Firstly, the original image is transformed to the grayscale image and then the treble-classification Otsu method classifies the pixels in the grayscale image into three clusters according to their gray values. Secondly, the binary image is divided into several horizontal strips, and feature points representing green plants are extracted. Lastly, the proposed double-dimensional adaptive clustering method, which can deal with gaps inside a single crop row and misleading points between real crop rows, is applied to obtain the clusters of real crop rows and the corresponding fitting line. Quantitative validation tests of efficiency and accuracy have proven that the combination of these two methods constitutes a new robust integrated solution, with attitude error and distance error within 0.02° and 10 pixels, respectively. The proposed method achieved better quantitative results than the detection method based on typical Otsu under various conditions.

Artificial intelligence is a bellwether of today’s new technological revolution. As a branch of artificial intelligence, machine learning faces two main problems in practical application: 1) data owned by most enterprises are difficult to aggregate; and, 2) big data owners pay more and more attention to data privacy and security, which leads to the problem of data island. Federated learning (FL), as a distributed FL paradigm, which can enable all parties to achieve the purpose of co-building models while ensuring data privacy and exposure, provides a possible solution to the mentioned problems of machine learning. The FL takes full advantage of participants’ data and computing power and builds a more robust machine learning model without sharing the data. In an environment with strict data regulation, the FL can effectively solve the key problems, such as those related to data privacy and data rights. However, most of the existing FL-based frameworks do not pay attention to the impact of data source distribution on FL training. Therefore, this paper proposed a data-oriented FL framework called the Federated AI Engine(FAE), which can solve FL problems without leaving the data in control. The proposed framework provides a method that can be used to verify FL quickly for researchers who intend to try federal learning.

Air source heat pumps (ASHPs) have been widely used for space heating in cold winter. When it operates in frosting environment, defrosting is necessary to maintain the system performance resulting in a discontinuous space heating. The defrosting time is an important parameter to evaluate the performance of different defrosting methods. At present, the widely applied ways for defrosting are the standard reverse-cycle defrosting and hot-gas bypass defrosting methods. For the two defrosting methods, the biggest problem is that no heat source is available for the defrosting cycle which leads to a long defrosting time. For the past few years, study on the use of heat exchangers with phase change material (PCM-HE) to storage heat for the defrosting receives lots interest. This paper presents a review of these reported defrosting methods using PCM-HE. The ASHPs with PCM-HE and their defrosting principles are introduced. Furthermore, the frequently-used phase change materials together with structure of PCM-HE are also summarized. Finally, the further research direction to realize effective defrosting and continuous heating of air-source heat pump products is discussed.

The relationship between the luminescence properties and the glass structure of Nd3+-doped CaO-Al2O3-(B2O3, SiO2, or Ga2O3) glasses are investigated. The luminescence properties of CaO-Al2O3-B2O3 system are twice as much as that of the CaO-Al2O3-(SiO2 or Ga2O3) system. The glass structure and the coordination environment of the Nd3+ ions were investigated using nuclear magnetic resonance, Raman and electron paramagnetic resonance spectroscopy. All Al, Ga, and Si atoms are four coordinated. The B atoms have three- and four-coordinated boron units, however, most of them are three coordinated. The hyperfine sublevel correlation spectra reveal that the Al and B nuclei are in the coordination sphere of Nd3+ ions for aluminoborate glasses; however, only 27Al signals could be observed for aluminosilicate and aluminogallate glasses. Owing to the increased number of AlO4-BO3 connections and 11B nuclei around the Nd3+ ions, B has a significant effect on the luminescence properties of the Nd3+ ions. The increase in GaO4 or SiO4 does not change the three dimensional-tetrahedral network, and the coordination environment of Nd3+ ions varies slightly. Thus, the effect of Ga2O3 and SiO2 on the luminescence properties of the Nd3+ ions is not as great as that of B2O3.

A strategy is employed to address the coupling among propeller, shaft, hull and its contribution to acoustic radiation using the three-dimensional sono-elasticity method (Zou et al., 2010, 2014). Different from our previous work, the local resonance of the elastic propeller is taken into account which makes a significant difference in the response. Further, its impact on acoustic radiation is also analyzed. Through numerical discussion, it is indicated that the coupled acoustic radiation has peaks at the frequencies of the longitudinal modes of the hull, the longitudinal mode of the shaft system, and the umbrella mode of the propeller. The propeller damping could affect the coupled acoustic radiation significantly. This work would lend itself to further acoustic optimization of ships driven by propellers through relatively long shafts.

A detailed study structure and luminescence properties of Nd3+: Ga2O3-Al2O3-PbO-CaO laser glasses was conducted. The network structure was mainly dominated by Al (IV) or Ga (IV). With the increase of the Al2O3 content, the Al (IV) content increases, whereas the Ga (IV) content decreases. Hyperfine sublevel correlation (HYSCORE) spectra reveal 27Al and 207Pb weak hyperfine coupling, which indicates that these nuclei are in the second- or higher-order Nd3+ coordination sphere. No 69Ga or 71Ga signals can be detected in the three-pulse electron spin echo envelope modulation (3P-ESEEM) and HYSCORE spectra. For germanate glass, the local environment of the Nd3+ ions is characterized by the Pb ligand, for aluminum gallium glasses, the Nd3+ ions are surrounded by Al3+ and Pb2+ ions, and for aluminum glass, Nd3+ ions are mainly surrounded by 27Al cations. The change in the structure and in the local environment of Nd3+ ions results in a change in the luminescence properties of glasses.

In this study, the effect of waste glass powder as a potential cementitious material on the strength, drying shrinkage and sulfate attack resistance of slag mortar activated by the mixture of water glass and sodium hydroxide was evaluated. Also, Central composite design and response surface method were used for the optimisation of the alkali content (sodium oxide equivalent) and replacement ratio of waste glass powder by maximising flexural and compressive strengths. The results of analysis of variance (ANOVA) indicated that the accuracy of the developed strength models based on response surface method was satisfactory. The optimal alkali content and replacement ratio of waste glass powder were found to be 8.31% and 14.57%, respectively. Under this condition, the experimental values of 3-, 7- and 28-day flexural strengths and 3-, 7- and 28-day compressive strengths of alkali-activated slag/glass powder mortar were 6.6 MPa, 7.1 MPa and 8.4 MPa, respectively and 49.2 MPa, 52.9 MPa and 66.4 MPa, respectively, which agreed closely with the predicted values since the percentages of error were negligible in the range of 0–2.38%. When the alkali content was 8.31%, the addition of 14.57% waste glass powder in alkali-activated slag mortar could improve the 3-, 7- and 28-day flexural and compressive strengths, reduce the dry shrinkage by up to 15.8% at 1 day and 20.3% at 120 days, and increase the resistance to sulfate attack.

Exhaust hot water (EHW) is widely used for various industrial processes. However, the excess heat carried by EHW is typically ignored and discharged into the environment, resulting in heat loss and heat pollution. An organic Rankine cycle (ORC) is an attractive technology to recycle heat from low-temperature energy carriers. Herein, ORC was used to recycle the heat carried by EHW. To investigate the energy and exergy recovery effects of EHW, a mathematical model was developed and a parametric study was conducted. The energy efficiency and exergy efficiency of the EHW-driven ORC system were modeled with R245fa, R113 and R123 as the working fluids. The results demonstrate that the EHW and evaporation temperatures have significant effects on the energy and exergy efficiencies of the EHW-driven ORC system. Under given EHW conditions, an optimum evaporation temperature exists corresponding to the highest exergy efficiency. To further use the low-temperature EHW, a configuration retrofitted to the ORC by combining with flash evaporation (FE) was conducted. For an EHW at 120 °C and 0.2 MPa, the maximum exergy efficiency of the FE-ORC system is 45.91% at a flash pressure of 0.088 MPa. The FE-ORC performs better in exergy efficiency than the basic FE and basic EHW-driven ORC.

AC Half-Wavelength transmission in UHV stage is an alternate for the long distance and large capacity power transmission, because of its unique characteristics. The characteristics half-wavelength transmission lines and conventional transmission lines are quite different. In this paper, digital simulation and dynamic simulation are carried out to study the electrical characteristics of half-wavelength AC transmission lines. Simulation results are compared and analyzed. The model and parameters of assumed half-wavelength transmission system are presented in this paper. The steady-state and transient characteristics of the half-wavelength AC transmission line are studied by digital simulation and dynamic simulation. The simulation results are given and analyzed. The validity of the digital simulation model was verified by the comparison of results of digital simulation and dynamic simulation.

Grain refinement is a critical approach to improve the strength of materials without damaging the toughness. The grains of deformation-induced ferrite are considerably smaller than those of proeutectoid ferrite. Grain refinement is crucial to the application of deformation-induced ferrite. The composition of ferrite and bainite or martensite is important in controlling the performance of X70HD pipeline steel, and cooling significantly influences the control of their ratio and grain size. By analyzing the static and dynamic phase-transition points using Gleeble-3800 thermal simulator, thermal simulations were performed through two-stage deformations in the austenite zone. Ferrite transformation rules were studied with thermal simulation tests under different deformation and cooling parameters based on the actual production of cumulative deformation. The influence of deformation parameters on the microstructure transformation was analyzed. Numerous fine-grain deformation-induced ferrites were obtained by regulating various parameters, including deformation temperature, strain rate, cooling rate, final cooling temperature and other parameters. Results of metallographic observation and microtensile testing revealed that the selection of appropriate parameters can refine the grains and improve the performance of the X70HD pipeline steel.

A series of single-crystal polyhedra spinel LiAlxMn2-xO4 (x = 0, 0.05, 0.10, 0.15 and 0.20) cathode materials have been rapidly prepared by a solution combustion technique using HNO3 solution as an auxiliary oxidant. The crystal structure and phase identification of as-prepared samples were characterized through X-ray diffraction (XRD), which shows that all samples present the characteristic diffraction peaks of spinel LiMn2O4. The morphology and particle size of as-prepared samples were observed by field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM), which indicate that all samples have single-crystal polyhedra morphology and good crystallinity. The cycling performances of as-prepared samples were evaluated by galvanostatic charge/discharge cycling performance tests, which demonstrate that LiAl0.10Mn1.90O4 exhibits the optimal cycling and rate properties. It delivers a capacity retention rate of 60.7% after 2000 cycles with an initial discharge specific capacity of 99.5 mAh g−1 at 10 C (1 C = 148 mAh g−1) and 25 °C, while the capacity retention rate of pristine LiMn2O4 is only 9.6% with an initial discharge specific capacity of 81 mAh g−1 at the same conditions. The Al-doped samples show better elevated temperature cycling stability than pristine LiMn2O4. LiAl0.10Mn1.90O4 sample shows a capacity retention rate of 81.5% with a discharge specific capacity of 91.3 mAh g−1 after 500 cycles at 1 C and 55 °C, which is much superior compared with the capacity retention rate of 18.5% for pristine LiMn2O4. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests certify that LiAl0.10Mn1.90O4 presents the better electrode reversibility, more rapidly charge-transfer and Li+ diffusion kinetics processes.

Rationally designed synthesis strategy for well-defined morphology which can endow the catalysts with unexpectedly enhanced catalytic properties remains a significant challenge in heterogeneous cat...

Dextransucrase is the enzyme that catalyzes the synthesis of dextran from sucrose. Though dextran is an unwanted deterioration product in the sugar industry, it is being widely used in medicine, cosmetics, and several food areas. Currently, the natural enzyme activity of dextransucrase is low. Thus, it is of great interest to understand how to improve the dextransucrase activity. In the study, Leuconostoc mesenteroides (L.M.CICC-20724) were cultured in a glucose-based solid medium (glucose was the sole carbon source) and then transferred to a sucrose-based solid medium (sucrose was the sole carbon source) for rejuvenation. It was observed that the dextransucrase production was inhibited when L.M.CICC-20724 using the glucose-based solid medium. After 3 months of acclimation, the activity of dextransucrase produced by the acclimated L. mesenteroides (Glu-L.M.) achieved a stable level at approximately 4.20 U/mL. The dextransucrase activity (approximately 1–2 U/mL) increased more than two times with L.M.CICC-20724 in comparision with original one. Dextran products generated from Glu-L.M. and L.M.CICC-20724 were studied using Fourier transform infrared spectroscopy and results showed that both dextrans had a consistent structural composition. The kinetics of sucrose consumption was studied. Under the condition of 0.5 U/mL dextransucrase activity, the consumption of relative low initial sucrose concentrations (0.1, 0.2 and 0.4 M) more fitted to the first-order reaction kinetics, while the consumption of relative high initial sucrose concentrations (0.6 and 0.8 M) was fitted better to the second-order reaction kinetics.

A new redox graphene/copper–nickel solid solution/polyaniline (RGO/Cu–Ni/PANI) composite as a supercapacitor electrode is designed and successfully prepared by a flexible two-step method: first nano copper–nickel is supported on the surface of the oxide graphene, forming the RGO/Cu–Ni composite, followed by PANI is coated on RGO/Cu–Ni via in-situ polymerization process. The structure of the ternary composite is characterized by X-ray power diffraction, X-ray photoelectron spectroscopy, fourier transform infrared and scanning electron microscope. The RGO/Cu–Ni/PANI composite material shows better electrochemical performances than the pure PANI. The results show that the RGO/Cu–Ni/PANI composite have a great specific capacitance 674.7 F g−1 at 1 A g−1 current density and good cyclic stability of 90.1% over 1000 charge–discharge cycles, which can be attributed to the synergistic effect between RGO, Cu–Ni and PANI. Thus, the RGO/Cu–Ni/PANI composite is excellent electrode material in supercapacitor with high specific capacitance and the long-term cycle stability, and that is helpful in developing new kinds of portable energy storage devices.

In this paper, the effect of the powder particle structure and substrate hardness during vacuum cold spraying (VCS) of Al 2 O 3 is investigated. Our results help understand the underlying deposition mechanism during VCS in more detail and enable the tailoring and improving of the resulting coatings. Two structurally different alumina feedstocks were used for this study. We find that the loosely agglomerated powder bonds to the substrate primarily through coordinated deformation of the nano-sized powder particles. The sintered powder, on the other hand, bonds to the substrate through severe fracture and deformation of the particles. High-resolution transmission electron microscopy (HR-TEM) was employed to observe details in the interfacial microstructure of the coatings on the two substrates with differing hardness. The hard steel substrate facilitates particle fracture, which leads to cohesive particle/particle-bonding in the coating region close to the substrate. The softer aluminum substrate leads to strong interfacial coating/substrate-bonding because the particles are embedded into the substrate. In summary, the fracture and deformation of the feedstock as well as the substrate hardness affect both adhesion (coating/substrate bonding) and cohesion (particle/particle bonding) considerably.

There is large amount of waste heat resources in industrial processes. However, most low-temperature waste heat is directly discharged into the environment. With the advantages of being energy-efficient, enabling investment-savings and being environmentally friendly, the Organic Rankine Cycle (ORC) plays an important role in recycling energy from low-temperature waste heat. In this study, the ORC system driven by industrial low-temperature waste heat was analyzed and optimized. The impacts of the operational parameters, including evaporation temperature, condensation temperature, and degree of superheat, on the thermodynamic performances of ORC system were conducted, with R113 used as the working fluid. In addition, the ORC-based cycles, combined with the Absorption Refrigeration Cycle (ARC) and the Ejector Refrigeration Cycle (ERC), were investigated to recover waste heat from low-temperature flue gas. The uncoupled ORC-ARC and ORC-ERC systems can generate both power and cooling for external uses. The exergy efficiency of both systems decreases with the increase of the evaporation temperature of the ORC. The net power output, the refrigerating capacity and the resultant exergy efficiency of the uncoupled ORC-ARC are all higher than those of the ORC-ERC for the evaporation temperature of the basic ORC >153 °C, in the investigated application. Finally, suitable application conditions over other temperature ranges are also given.

Various nickel and magnesium dual-doped LiNixMg0.08Mn1.92−xO4 (x ≤ 0.15) were synthesized via a modified solid-state combustion method. All as-prepared samples show typical spinel phase with a well-defined polyhedron morphology. The Ni-Mg dual-doping obviously decreases the lattice parameter that gives rise to the lattice contraction. Owing to the synergistic merits of metal ions co-doping, the optimized LiNi0.03Mg0.08Mn1.89O4 delivers high initial capacity of 115.9 and 92.9 mAh·g−1, whilst retains 77.1 and 69.7 mAh·g−1 after 1000 cycles at 1 C and high current rate of 20 C, respectively. Even at 10 C and 55 °C, the LiNi0.03Mg0.08Mn1.89O4 also has a discharge capacity of 92.2 mAh·g−1 and endures 500 cycles long-term life. Such excellent results are contributed to the fast Li+ diffusion and robust structure stability. The anatomical analysis of the 1000 long-cycled LiNi0.03Mg0.08Mn1.89O4 electrode further demonstrates the stable spinel structure via the mitigation of Jahn-Teller effect. Hence, the Ni-Mg co-doping can be a potential strategy to improve the high-rate capability and long cycle properties of cathode materials.

In order to improve the power level and efficiency, combined with the advantages of T-type three-level converter, a parallel T-type three-level PCS topology is proposed. In order to solve the resonance problem, the system impedance model of LCL filter is established and the mathematical expression is set up. Then, the infulence of the current oscillation is analyzed from the excitation. The relationship between the number of parallel stations and the number and frequency of the resonace points is obtained with the spectrum charts simulated by Matlab. A coordinated control strategy of parallel T-type three-leve PCS based on capacitor voltage active dampling is proposed to suppress the resonace of the system. Finally, a 500 kW PCS prototype is developed. The Matlab simulation comparison and the experimental results show the correctness of the theoretical analysis, and the effectiveness of the proposed control scheme.

Soybean variety is connected to stress resistance ability, as well as nutritional and commercial value. Near-infrared hyperspectral imaging was applied to classify three varieties of soybeans (Zhonghuang37, Zhonghuang41, and Zhonghuang55). Pixel-wise spectra were extracted and preprocessed, and average spectra were also obtained. Convolutional neural networks (CNN) using the average spectra and pixel-wise spectra of different numbers of soybeans were built. Pixel-wise CNN models obtained good performance predicting pixel-wise spectra and average spectra. With the increase of soybean numbers, performances were improved, with the classification accuracy of each variety over 90%. Traditionally, the number of samples used for modeling is large. It is time-consuming and requires labor to obtain hyperspectral data from large batches of samples. To explore the possibility of achieving decent identification results with few samples, a majority vote was also applied to the pixel-wise CNN models to identify a single soybean variety. Prediction maps were obtained to present the classification results intuitively. Models using pixel-wise spectra of 60 soybeans showed equivalent performance to those using the average spectra of 810 soybeans, illustrating the possibility of discriminating soybean varieties using few samples by acquiring pixel-wise spectra.

In this paper, the hydraulic efficiency optimization calculation method of a ten-stage centrifugal pump is researched. According to the hydraulic loss model, a multi-objective optimization calculation method based on surrogate models is proposed. In order to study the highly nonlinear relationship between key design variables and centrifugal pump external characteristic values, this paper builds the quadratic response surface, the radial basis Gaussian response surface, and Kriging three surrogate models using computer fluid dynamics (CFD) simulation analysis. Two types of calculation models (hydraulic loss model and three surrogate models) combined NSGA-Π genetic algorithm are applied to optimize the key design variables and to find the optimal solution of each model. The accuracy and effectiveness of the efficiency optimization methods based on the two types of calculation models are compared and analyzed. The results show that the calculation method of hydraulic loss model based on the semitheoretical and semi-empirical formula is less time-consuming but inaccurate. In contrast, the optimization method based on surrogate models using CFD simulation is accurate. What's more, comparing the surrogate models, the results based on the complete quadratic response surface model which make the efficiency of the first stage centrifugal pump reach 77.26% are more accurate.

The on-surface synthesis of single-layered covalent organic frameworks (sCOFs) has been investigated by employing a 3-fold symmetric monomer 1 carrying aldehyde groups and the ditopic diamine building block 2 on a highly oriented pyrolytic graphite surface. The self-assembly of molecule 1 is persistently observed at the stoichiometric ratio of the reactive groups. The growth of sCOF network is observed, however, only at the excess of diamine monomers. By investigating the growth process of the sCOF network, the role of excessive diamine monomers can be understood by two aspects. Increasing the molar ratio of diamine monomer provides the driving force for the structural transition from the monomer self-assembly to the formation of the sCOF network. On the other hand, the excess diamine monomers provide basic environment for the transimination reaction and promote the formation of highly ordered sCOFs. The present work provides molecular understanding of the role of transimination reaction in imine-based COF synthesis.

Yttrium (Y) is an engineering material used in refinement, and the physical properties of Y2O3 nanomaterials play key roles in thermal-effect of refinement. In this study, the experimental thermal-efficiencies induced by dimension of Y2O3 nanomaterials and their influence on microstructures and tensile performances of graded stainless steel coatings were investigated. To this end, 16Cr2NiSiMo stainless steel coatings were fabricated by laser metal deposition (LMD) technology in the presence of small amounts (

In this work, Caenorhabditis elegans was employed as an in vivo model to determine the toxic effects of atrazine at different concentrations. After the exposure period from the larval stage L1 to adulthood day 1, atrazine (10 mg/L) significantly decreased the body length and lifespan of nematodes. In addition, exposure to ≥0.01 mg/L atrazine remarkably increased the intestinal reactive oxygen species (ROS) levels and reduced locomotion behavior of nematodes, while exposure to ≥ 1 mg/L atrazine decreased the brood size of nematodes. Moreover, atrazine (0.001–0.1 mg/L) upregulated the expression levels of hsp-6::GFP and hsp-6/60 in nematodes, indicating the activation of mitochondrial unfolded protein response (mtUPR). On the contrary, atrazine (1–10 mg/L) downregulated the expression levels of hsp-6::GFP and hsp-6/60 in nematodes. Furthermore, mtUPR induction governed by the RNAi knockdown of atfs-1 could increase the vulnerability of nematodes against atrazine toxicity. Overall, our findings highlighted the dynamic responses of nematodes toward different concentrations of atrazine, which could be monitored using different sublethal endpoints as bioindicators.

Fumaric acid production from industrial waste by microorganism was regarded as an available method. Glycerol as the by-product of biodiesel was a suitable feed stock for fumaric acid production co-fermented with glucose. In this work, the influence of glycerol on the co-fermentation process was explored on the basis of fermentation optimization. It was indicated that the optimum addition level of glycerol was 40 g/L, under which the efficiency of glucose conversion and fumaric acid titer was certainly preferable. After comparing the permeability and fatty acids of the cell membrane, Rhizopus arrhizus cells membrane in co-fermentation process showed a better permeability and a reasonable fatty acids composition, which caused the improvement of fumaric acid emission, leading to the promotion of glucose conversion. Identification of key metabolites combining with feeding strategies was further illustrated the superiority of co-fermentation, which had a potential development advantages in organic acid production process.

A significant amount of research on the vibration and sound radiation of the cylindrical shell has been carried out and reported. The cylindrical shell was usually assumed to be submerged in an infinite fluid. However, the fluid region surrounding the cylindrical shell is bounded. Free vibration and forced vibration characteristics of finite cylindrical shells semi-submerged are studied in this paper, based on energy functional variational principle. The combined form of the triangular series and the Fourier series is used for the displacement of the cylindrical shell, then the orthogonality can be used to eliminate the other two directions after the variation, and only the radial displacement is kept. The relationships between the amplitudes of fluid load and the amplitudes of the radial displacement are established by the orthogonal processing of the continuous conditions of the solid-liquid coupling contact surface and the boundary conditions of the free liquid surface. Finally, the fluid structure coupling control equation is obtained. The results show that the method is correct and effective, in addition, providing a new thought for solving similar problem.

We have studied the self-assembly structure of meso-diphenyltetrathia [22]-annulene [2,1,2,1] (DPTTA) on highly oriented pyrolytic graphite (HOPG), Au(111), and single-layer graphene (SLG) modified Au(111) substrates. High resolution scanning tunneling microscopy (STM) reveals that DPTTA molecules pack into one dimensionally ordered row structure on graphene and HOPG surfaces, while assemble into two dimensional close-packed structure on Au(111) surface. We ascribe this difference to the effect of the substrate. The addition of C60 molecules on these DPTTA modified substrates further reveals that the structural difference in DPTTA adlayer can affect its ability to form donor-acceptor (D-A) hierarchical structure with C60 molecules. The results provide an example of substrate effect in self-assemblies of functional molecules, which is significant for the design of molecular based devices.

In this Technical Note, the use of a liquid metal, i.e., a low melting point Pb–Sn–In–Bi alloy, as the phase change material (PCM) in thermal energy storage-based heat sinks is tested in comparison to an organic PCM (1-octadecanol) having a similar melting point of ∼60 °C. The thermophysical properties of the two types of PCM are characterized, revealing that the liquid metal is much more conductive while both have nearly identical volumetric latent heat of fusion (∼215 MJ/m3). By using at the same volume of 80 mL, i.e., the same energy storage capacity, the liquid metal is shown to outperform significantly over the organic PCM under the various heating powers up to 105.3 W/cm2. During the heating period, the use of the liquid metal leads to a remarkable extension of the effective protection time to nearly twice longer as well as a reduction of the highest overheating temperature by up to 50 °C. The cool-down period can also be shortened significantly by taking advantage of the much higher thermal conductivity of the liquid metal. These findings suggest that liquid metals could serve as a promising PCM candidate for particular applications where the volume limit is very rigorous and the penalty in weight increment is acceptable.

A novel adsorbent, tartaric acid modified graphene oxide (GO-TA), was successfully prepared by a simple esterification reaction and applied to remove Cu(II) and Pb(II) metal ions from aqueous solutions. The obtained composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and transmission electron microscopy (TEM). Batch experiments were carried out to investigate the effect of pH value, contact time, concentration of metal ions and temperature on Cu(II) and Pb(II) adsorption. The maximum adsorption capacities for Cu(II) and Pb(II) are 374.53 mg g−1 and 125.63 mg g−1, respectively, which were higher than those of pristine graphene oxide (GO). The obtained experimental data showed a good correlation with the Langmuir adsorption model. The adsorption kinetics of Cu(II) and Pb(II) onto GO-TA composite was found to be well fit for the pseudo-second-order model. Moreover, thermodynamic parameters including ΔGθ 0 and ΔSθ> 0, indicating that the adsorption of Cu(II) and Pb(II) onto GO-TA composite was spontaneous and endothermic in nature. All these results indicated that GO-TA composite with such high adsorption efficiency and fast adsorption equilibrium could be used to clean up heavy metal pollution in the future.

An extensional method for existing business processes is proposed to adapt new environments based on process variants in this paper. The core processes describing maximal commonalities of process variants are introduced according to inheritance relation. Then, extensional business processes are defined based on the core processes. The algorithms of the core processes and extensional business are given and proved. And the soundness of two kinds of processes is justified. An example shows that extensional business processes can adapt to the new environment better than the original process.

Soluble strong bases such as NaOH or CH3ONa were industrially applied in production of multiple carbonates via the transesterification route. However, the catalytic efficiency decreased significantly after recycling and insoluble solids were formed, leading to a complicated and non-eco-friendly manufacture process. In this study, the influence of Na-based soluble basic catalysts (C4H9ONa, C2H5ONa, CH3ONa, NaOH, Na2CO3, and NaHCO3) structures, amounts, reusability, reaction atmospheres, and different reactants treatment were systematically studied for in-depth understanding the deactivated processes and mechanism. The results indicated dimethyl carbonate (DMC) was responsible for the deactivation and with decreasing the pKb (alkalinity coefficient) value, the alkali strength, nucleophilicity, and catalyst efficiency increased. The properties of fresh, DMC-treated and recycled NaOH or CH3ONa samples were characterized by means of XRD, FT-IR, Raman, TG, and SEM. Nearly all the characterizations proved that the final deactivation species was Na2CO3 after long-time treatment or recycle. A possible deactivation mechanism of soluble bases during the transesterification process was proposed. The presence of trace H2O was the induction of CH3ONa deactivation, whereas the interaction between DMC and NaOH led to the formation of Na2CO3. This finding will contribute to the development of strategies to design homogeneous catalysts with high activity and stability for carbonate transesterification.

A structure-property model with a highly fitting degree (R2 > 0.95) for phosphogermanate glass was established, based on the structural units extracted by O-1s X-ray photoelectron spectroscopy (XPS). The model can predict density and optical properties (e.g., refractive index, Stark splitting, and emission cross section. The verification error was less than those of the traditional addition method and mathematical statistics method. The corresponding parameters indicated that density and refractive index may be largely influenced by non-bridging oxygens (NBOs), while Stark splitting and emission cross section may be greatly affected by the structural units related to germanium and the NBOs related to phosphorus, respectively. Numerical simulation suggested that the increase in Yb3+ may be neglected for the spectroscopic properties of phosphogermanate glass when GeO2

Human drivers have rich and diverse driving characteristics on curved roads. Finding the characteristic quantities of the experienced drivers during curve driving and applying them to the steering control of autonomous vehicles is the research goal of this article. We first recruited 10 taxi drivers, 5 bus drivers, and 5 driving instructors as the representatives of experienced drivers and conducted a real car field experiment on six curves with different lengths and curvatures. After processing the collected driving data in the Frenet frame and considering the free play of a real car’s steering system, it was interesting to observe that the shape enclosed by steering wheel angles and the coordinate axis was a trapezoid. Then, we defined four feature points, four feature distances, and one feature steering wheel angle, and the trapezoidal steering wheel angle (TSWA) model was developed by backpropagation neural network with the inputs were vehicle speeds at four feature points, and road curvature and the outputs were feature distances and feature steering wheel angle. The comparisons between TSWA model and experienced drivers, model predictive control, and preview-based driver model showed that the proposed TSWA model can best reflect the steering features of experienced drivers. What is more, the concise expression and human-like characteristic of TSWA model make it easy to realize human-like steering control for autonomous vehicles. Lastly, an autonomous vehicle composed of a nonlinear vehicle model and electric power steering (EPS) system was established in Simulink, the steering wheel angles generated by TSWA model were tracked by EPS motor directly, and the results showed that the EPS system can track the steering angles with high accuracy at different vehicle speeds.

Graphene oxide (GO) or reduced graphene oxide (RGO) is an excellent promoter to improve the photodegradation activity of a hybridized photocatalyst in advanced oxidation processes (AOPs). However, the identification of active sites remains a challenge due to the complexity of GO surface with different oxygen functionalities and defects coexisted. In this work, we synthesized different GO/polythiophene (GO/PTh) composites via in-situ polymerization of thiophene monomers on different GO supports with controlled content of oxygen functionalities such as carboxyl, hydroxyl and epoxide bonds. GO-COOH/PTh shows the highest performance in the degradation of methylene blue (MB) and phenol under visible light among all GO/PTh catalysts. We find the degradation rate is determined by the amount of hydroxyl free radicals ( OH) via the reaction of photoelectrons with H2O2. Different oxygen groups on GO surface results in different photoelectron conversion efficiency (η, the ratio of degradation rate to photocurrent). More importantly, we find that η correlates linearly with the amount of COOH in the catalysts, indicating COOH groups act as active sites for OH generation during photodegradation. This study provides a deep understanding of active sites for H2O2 decomposition in photo-assisted Fenton-like systems over GO containing photocatalysts.

The separation of oil/water emulsion has become a pressing worldwide problem. In this study, a novel type of photoinduced separation membrane was prepared via layer-by-layer (LBL) method of ZIF-8/GO composite. By integrating the unique physical and chemical properties of ZIF-8 and GO, the ZIF-8/GO membrane exhibits superior superoleophobicity under visible light and underwater anti-fouling for efficient oil rejection from water. We found that the ZIF-8/GO membrane permeation flux was 110 ± 6 L m−2 h−1 under light irradiation, which was higher than the permeation flux of membranes without irradiation (50 ± 6 L m−2 h−1). For toluene, the removal rate was about 100% at the first time, with new benzyl alcohol and benzaldehyde products detected in the filtrate, indicating that toluene was degraded on the ZIF-8/GO membrane surface. Continuous separation performed using filtration apparatus demonstrates a high separation capacity, with long-term membrane stability. The high water flux, high separation capacity and capacity for large-scale preparation of the ZIF-8/GO membrane, shows great potential for industrial application in the treatment of oil-containing wastewater.