Search

Near-equiaxed β grain was achieved in the near-α Ti60 (Ti-5.7Al-4.0Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C) titanium alloy via laser directed energy deposition (LDED). The microstructural evolution along the building direction and the room-temperature tensile properties along the horizontal and vertical directions (building direction) were systematically studied through SEM and OM. EBSD and XRD were utilized to accurately demonstrate the texture of the α and β phases. The results showed that the α phase presented a low texture intensity, which was ascribed to the weak textured β grain with near-equiaxed morphology, since there are Burgers orientation relationships during the β→α transition. In addition, numerical simulation, combined with the CET curve of Ti60 alloy considering the effect of multi-composition, was utilized to elucidate the formation mechanism of the near-equiaxed β grains. Furthermore, according to the solidification theory, we proposed that the solidification temperature range Δ T f was more accurate than the growth restriction factor Q in predicting the formation tendency of equiaxed β grain in different titanium alloys. Tensile results showed that the horizontal and vertical samples had similar strength, while the former exhibited larger elongation than the latter. The effect of the near-equiaxed β grain and the internal α phase on mechanical properties were revealed at last.

Although TiO2 is a wide band gap semiconductor, it demonstrates photodegradation activity under visible light irradiation after dye sensitization. Compared with esterification between the surface hydroxyl group of TiO2 and the carboxylic group of dyes, electrostatic interaction between TiO2 and dye shows better photosensitized performance. In this work, Bi/Al co-doping anatase titania (Ti1-xBi2x/3Al2x/3O2 (0 ≤ x ≤ 0.3)) is designed to enhance the electrostatic interaction. The effect of Al ions is to enhance the solubility of Bi3+ into titania nanocrystals. A new band gap is generated after high concentration of Bi element doping, which not only promotes the absorption of visible light, but also improves the utilization of photogenerated carriers. Based on the results of transmission electron microscopy, light absorption, photodegradation activity and density functional theory calculations, it is found that bismuth dopant is the electron capture site. It first accumulates electrons through photocatalytic degradation reaction to enhance electrostatic adsorption between the catalyst and the positively charged dye molecules, and finally realizes high-efficiency photosensitization degradation of Rhodamine B. In addition, the sensitized titania has excellent photodegradation recyclability.

The detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is crucial for preventing and controlling infectious diseases and disease treatment. In this work, a Au@Ti3C2@PEI-Ru(dcbpy)32+ nanocomposite-based electrochemiluminescence (ECL) biosensor was rationally designed, which realized sensitive detection of the RNA-dependent RNA polymerase (RdRp) gene of SARS-CoV-2. In addition, a DNA walker was also used to excise the hairpin DNAs under the action of Nb.BbvCI endonuclease. Furthermore, model DNA–Ag nanoclusters (model DNA–AgNCs) were used to quench the initial ECL signal. As a result, the ECL biosensor was used to sensitively detect the SARS-CoV-2 RdRp gene with a detection range of 1 fM to 100 pM and a limit of detection of 0.21 fM. It was indicated that the ECL biosensor had a great application potential for clinical medical detection. Furthermore, the DNA walker amplification also played a reliable candidate strategy for other detection methods.

Summary Accurately predicting wax deposits in a crude pipeline through empirical formulas or numerical modeling is unreliable because of the incomplete mechanism and the time-dependent unsteady actual operating conditions. With the help of the data collected by the supervisory control and data acquisition system of pipelines, wax deposit prediction is made possible by developing the time-dependent data mining method. In this article, the data from a typical long-distance crude pipeline in China operating over a 4-year time period was investigated. The inlet temperature prediction was first conducted by developing the long short-term memory (LSTM)-recurrent neural networks (RNNs) model, during which the feature sequencing, overfitting problems, and optimal hyperparameters were fully considered. Because of the time sequence cell, the accuracy of the LSTM-RNN model, as well as the time consumption, is much better than the RNN model when dealing with a great deal of data over a long period of time. Taking the inlet temperature prediction results as input features, the prediction model of average wax deposit thickness was established based on the backpropagation (BP) neural network and optimized by the particle swarm optimization (PSO), chaos particle swarm optimization (CPSO), and adaptive chaos particle swarm optimization (ACPSO) algorithms. The conclusions and associated algorithm from this article help to determine the reasonable pigging circle of long-distance pipelines practically. It could also be applied to guide the wax deposit prediction in the wellbore or oil-gatheringpipes.

We demonstrate a facile and seedless wet chemical process to deposit RuO2 thin film on a glass slide. The process entails the use of dopamine and its oxidized form, polydopamine (PDA), as the reducing and chelating agent, as well as the adhesive agent bonding the RuO2 and glass slide. The formula starts with the oxidation of K2RuCl5 to prepare RuO4 solution, followed by its reduction by dopamine to form chelated RuO2 colloids for the deposition of amorphous RuO2 thin film containing 26.5 at% hydrous RuO2 and 73.5 at% RuO2. After a mild Ar annealing, the RuO2 thin film exhibits a rutile phase with (110) preferred orientation. Elemental analysis indicates incomplete pyrolysis of PDA. Results from X-ray absorption spectroscopy confirm the presence of RuO4 and its transformation to RuO2. Electrochemical analysis of the adsorbed dopamine molecules on an ITO substrate validates the oxidative behavior of dopamine. The bonding strength of RuO2 thin film is determined by a tape-peeling test in which both the as-deposited and annealed RuO2 thin films show robust adhesion to the glass substrate.

Herein, we exploited the double-stranded DNA (dsDNA) binding property of transcription factor (TF), combined with the trans cleavage characteristic of CRISPR-Cas12a, for the detection of NF-κB p50.

Exhaust-plume-induced plasma from solid rocket engines absorbs electromagnetic (EM) waves and may cause communication interruptions. Previous articles have proposed both physical phenomena and propagation models for this problem, but few articles have analyzed random fluctuations of EM waves propagating through plumes from a communications perspective. This article attempts to attach these fluctuations, which are caused by the plume-induced turbulent plasma spread medium, to the communications channel characteristics. A multi-parameter stochastic model is established to characterize the exhaust plume channel in which the first-order and the second-order statistical properties are presented. Accordingly, a ground firing test was conducted to validate the EM wave propagation characteristics and the channel characteristics. The experimental results are in good consistence with the theoretical results. The results indicated that the time-varying envelope of the transmitted EM waves obeys a log-normal distribution, whereas the time-varying phase shift obeys a normal distribution. Moreover, the time–frequency analysis method was applied to evaluate the EM–plume interactions in the time–frequency domain. These results are critical for designing the rocket communication systems and evaluating the systems performance.

Developing antibiotics-independent antibacterial agents is of great importance since antibiotic therapy faces great challenges from drug resistance. Graphene oxide (GO) is a promising agent due to its natural antibacterial mechanisms, such as sharp edge-mediated cutting effect. However, the antibacterial activity of GO is limited by its negative charge and low photothermal effect. Herein, the amino-functionalized GO nanosheets (AGO) with unique three-in-one properties were synthesized. Three essential properties (positive charge, strong photothermal effect, and natural cutting effect) were integrated into AGO. The positive charge (30 mV) rendered AGO a strong interaction force with model pathogen Streptococcus mutans (330 nN). The natural cutting effect of 100 µg·mL−1 AGO caused 27% loss of bacterial viability after incubation for 30 min. Most importantly, upon the near-infrared irradiation for just 5 min, the three-in-one properties of AGO caused 98% viability loss. In conclusion, the short irradiation period and the tunable antibacterial activity confer the three-in-one AGO a great potential for clinical use.

The properties of gold nanoparticles, such as conductivity, half-life, catalytic nature, improved solubility efficiency, chemical stability, and its mechanism in binding with bacterial cell wall to induce cell death, have increased its medicinal applications. This study investigated the antibacterial property of gold nanoparticles (AuNPs) synthesized from Garcinia kola pulp extract. The ripe fruits of Garcinia kola were obtained, and the pulps were removed, air dried, pulverized, extracted, and mixed with gold chloride solution following standard procedure. The synthesized AuNPs were characterized using ultraviolet visible spectrophotometer (UV-visible), Fourier transform infrared (FTIR) spectrophotometer, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX). The antibacterial examination was carried out on four clinical isolate bacteria using agar diffusion technique. The UV-visible analysis confirmed the formation of stable AuNPs at pH 7 in the wavelength region of 564 nm. The FTIR analysis confirmed that the secondary metabolites with –OH functional groups serve as the reducing agent for the synthesis of AuNPs. The morphological assessment of the synthesized AuNPs revealed spherical-shaped particles. The zones of inhibition of the synthesized AuNPs against test bacteria ranges from 3 to 13 mm while that of the control was in the range of 14 to 22 mm. This study provided an environmentally friendly approach in the synthesis of AuNPs from Garcinia kola pulps and also ascertained the medicinal application of the synthesized AuNPs as an antibacterial agent.

This paper designs an improved model predictive control (MPC) strategy for the flow field in a transonic wind tunnel to quickly mitigate the overshoot and smooth the input and output signals under model uncertainty. A flow field control model is established first, followed by model discretization and the general MPC structure. Then, an MPC robust tuning approach is presented, which includes a bending temporal matrix design, and an adaptive robust temporal tuning algorithm. The bending temporal matrix is proposed to reduce the variability in the input profile in the temporal domain by penalizing high-frequency components, thus indirectly smoothing the input and output trajectories. The proposed adaptive robust temporal tuning algorithm can obtain an optimal tuning ratio by maximizing the control performance index of the system under model uncertainty. Simulation results show that the improved MPC controller yields better performance than a traditional MPC controller in mitigating the overshoot and smoothing the input profiles.

A 3-D total-field/scattered-field (TF/SF) plane-wave source was developed for the analysis of the plane wave propagation characteristics in the reentry plasma sheath. Owing to the dynamic variation in the surrounding flow field, the plasma sheath during the reentry process presents various 3-D inhomogeneous structures, such as dynamic plasma turbulence and considerable metal ablation particles. The proposed 3-D model can be efficiently applied to simulate the scattering effects of the 3-D inhomogeneous structures on the electro-magnetic (EM) signals. The proposed model utilizes a 3-D TF/SF boundary to introduce the plane wave source into the simulation domain, and six pairs of 2-D auxiliary propagators are created to generate the incident field on the TF/SF boundary based on the phase matching and the current density convolution finite-difference time-domain (JEC-FDTD) method. The uniaxial anisotropy perfectly matched layer (UPML) is modified as the absorbing boundary condition of the 2-D propagators. Implementation issues such as stability and dispersion are also discussed. The accuracy and efficiency of the proposed scheme are validated by admirable numerical simulation results and excellent agreement with the transmission line analogy method.

In this paper, a novel ethylene-vinyl acetate copolymer (EVA)/amino-functionalized polymethylsilsesquioxane (PAMSQ) composite wax inhibitor (WI) was prepared through melt blending, and the rheological and wax depositing properties of the doped crude oil were studied. The EVA/PAMSQ composite can strongly crystallize with wax molecules and trigger the formation of compact wax flocs, which greatly improve the rheological properties of crude: compared to the pure EVA at the same dosage, the composite can further decrease the gel point and apparent viscosity (25 °C) by 14.6 °C and 92.0%, respectively. The wax deposition can also be inhibited by adding the composite: adding EVA inhibits the mass of the wax deposit at 24 h by 62.3%, and this number is suppressed by 77.9% after adding the EVA/PAMSQ composite, but the wax molecule diffusion is accelerated and the wax content in the wax deposit rises because of the improved crude oil rheological characteristics. Here, we develop the gel structure theory to consider the wax deposition process affected by the WI. Adding the WI contributes little to the wax precipitation temperature but decreases the gel structural strength of the oil a lot, and thus, the oil near the pipe wall can only form the wax deposit with a higher wax content to resist the pipe wall shearing. Therefore, the crude oil added EVA/PAMSQ composite possesses not only the lowest wax deposit rate and the highest aging rate but also the highest wax content in the wax deposit.

Direct C(sp3)-H functionalization of N-unprotected aliphatic amines represents one of the most efficient and straightforward strategies for amine synthesis. Despite some recent progress in this field, the NH2-directed γ-C(sp3)-H arylation of primary aliphatic amines except α-amino esters remained an unmet challenge. In this report, we established a simple and efficient method for site-selective C(sp3)-H arylation of primary aliphatic amines by aryl iodides. In the presence of only 5 mol% Pd(OAc)2, a wide range of aliphatic amines including O-benzyl and O-silyl amino alcohols were arylated at γ- or δ-positions by aryl iodides containing a broad scope of functional groups. The synthetic application of this method had also been demonstrated by large-scale synthesis, the synthesis of a fingolimod analogue, and the conjugation with natural d -menthol and fluorescent 1,8-naphthalimide.

In the crude oil production, comb-like octadecyl acrylate (OA) polymers are usually added into the well as flow improver, causing the existence of OA polymers in the produced fluid. OA polymers and...

Large and rapidly changing Doppler shift poses a huge challenge on fast carrier acquisition for hypersonic vehicle communications. In this study, a novel Doppler shift acquisition method is proposed to increase the acquisition probability and reduce the acquisition time simultaneously. Firstly, the Doppler rate is estimated with a proposed fast blind estimation algorithm. The order of Doppler shift is reduced though twice instantaneous delay autocorrelation operation on the received signal and the modulated information is cancelled, and the Doppler rate can be obtained by the corresponding spectrum analysis. Secondly, the received signal is compensated by the estimated Doppler rate. Finally, the maximum value of the average power spectrum of the compensated result over multiple symbols is detected, and the Doppler shift and Doppler rate can be jointly determined. Furthermore, to improve the acquisition speed, a corrected narrower range, which is determined by the flight conditions of the hypersonic vehicles, is proposed to constrain the search range of the power spectrum peak. Simulation results indicate that, under typical hypersonic flight conditions, the acquisition probability of the Doppler rate increases from 0.52 to 0.86 under − 20 dB. The processing speed can be improved by 75.47% when the length of the combined symbols is 1000.

We developed a predictive model for the pipeline friction in the 520–730 m3/h transmission range using the multi-layer-perceptron–back-propagation (MLP–BP) method and analyzing the unit friction data after the pigging of a hot oil pipeline. In view of the shortcomings of the MLP–BP model, two optimization methods, the genetic algorithm (GA) and mind evolutionary algorithm (MEA), were used to optimize the MLP–BP model. The research results were applied to the standard friction prediction of three sections of a hot oil pipeline. After the GA and MEA optimizations, the average errors of the three sections were 0.0041 MPa for the GA and 0.0012 MPa for the MEA, and the mean-square errors were 0.083 and 0.067, respectively. The MEA-BP model prediction results were characterized by high precision and small dispersion. The MEA-BP prediction model was applied to the analysis of the wax formation 60 and 90 days after pigging. The analysis results showed that the model can effectively guide pipe pigging and optimization. There was little sample data for the individual transmission and oil temperature steps because the model was based on actual production data modeling and analysis, which may have affected the accuracy and adaptability of the model.

We propose and demonstrate a cladding-pumped, erbium-ytterbium co-doped fiber amplifier (EYDFA) scheme based on dual wavelength auxiliary signal injection technique to solve the issue of the backward Yb-ASE self-lasing under strong pumping for the high-power fiber amplification of 1.5-μm kHz-linewidth linearly-polarized laser signal. With the dual wavelength auxiliary signal of 1030 and 1040 nm injection, the allowable maximum pump power without triggering the backward Yb-ASE self-lasing can be greatly increased due to the relieving effect on the inhomogeneous gain broadening. For an EYDFA with 3.8-m erbium-ytterbium co-doped double-clad fiber, the net output power is improved to 13.8 W, while the linewidth of the amplified single-transverse-mode linearly-polarized 1560 nm laser signal is still only 3.5 kHz. The SBS effect is observed to be trivial during the fiber amplification.

As a kind of enhanced oil recovery technology, CO2 flooding is being employed more and more widely in oil fields. In CO2 flooding produced fluid, crude oil, water, and CO2 are transported simultane...

Asphaltenes are natural pour point depressants, and the effect of asphaltene polarity on the low-temperature rheology of waxy oils has been well studied. In this paper, the influence of asphaltene ...

Among various processing methods for growing perovskite thin layers, dual-source vacuum deposition was once regarded as the most economical and high throughput method. However, co-evaporation of MAI and PbI2 often leads to an inevitable PbI2 interfacial layer formed by the initial growth of evaporation resulting in a compromised efficiency of vacuum deposited MAPbI3 solar cell. Here, two modified growth methods based on vacuum co-evaporation, namely solution-vacuum hybrid method (SVHM) and soaking-assistant fully-vacuum method (SAFVM), are developed to grow a completely converted MAPbI3 perovskite layer at the interface prior to the co-evaporation of MAPbI3 perovskite layer. Upon these two methods, the unwanted PbI2 layer can be removed from the interface resulting in much improved power conversion efficiency up to 14.35%. Our result shows that, while unwanted interfacial PbI2 layer is the main cause of low performing co-evaporated perovskite solar cell devices, by removing the PbI2 interfacial layer we can unlock the full potential of vacuum-based perovskite solar cells to industrial mass production.

Rare earth (RE) metals are now being widely applied in new material industries with rapidly increasing production. However, there is limited research on greenhouse gas emission factors from RE metals production by electrolysis and currently no method exists to account for this industry’s CO2 emissions in the ‘2006 IPCC Guidelines for National Greenhouse Gas Inventories’. This study employed two independent methods to determine direct carbon emission factors for industrial rare earth metals production by molten-salt electrolysis: continuous emissions monitoring by FTIR and time-integrated sampling with offline lab analysis, both measuring CO2 and CO concentrations in the exhaust gases from Pr-Nd, Dy-Fe and La potlines in three companies in China. The study confirmed that CO2 contributes >97% of the total carbon emission factor. Direct carbon emissions per tonne RE metal electrolysis is equivalent to one tenth to a half of the emission factor for aluminum production (due to much lighter molar mass of Al) but is similar on a mole basis (carbon emissions per mole metal). Emission factors vary with the type of rare earth metal or alloy produced and from one facility to another, ranging from 165.0 to 672.4 kg/t-RE metal for CO2, 3.00 to 8.23 kg/t-RE metal for CO and 46.4 to 186.8 kg/t-RE metal for total carbon. Direct CO2 and CO emission factors from the two exhaust gas monitoring methods agreed well considering the uncertainties.

For the pipeline transportation of waxy crude oil, pour point depressants (PPDs) have been developed and used to improve its flowability at low temperature. As supercritical CO2 (scCO2) flooding becomes a common technique to improve oilfield recovery, how the sensitivity of PPD changes due to the degassed crude oil treated by CO2 should be studied. In this work, the effect of scCO2 extraction on the performance of EVA in improving the flowability of Changqing degassed crude oil is investigated by means of a self-developed scCO2 treating equipment, SARA/HTGC analysis, SEM analysis, pour point test, rheological measurement, asphaltene precipitation test, particle size analysis, DSC test, and microscopic observation. The results show that without EVA addition, scCO2 extraction aggravates the flowability of the crude oil at low temperature. The scCO2 extraction extracts light components from asphaltene aggregates causing asphaltenes to precipitate, which inhibits the asphaltenes on playing a role as the natur...

During hypersonic flight, the communication link is affected by the multipath effect and plasma sheath. As a result, envelopes and phases of the wireless signals fluctuate with time. In this paper, an integrated channel model is proposed based on geometric propagation theory. The statistical characteristics of the plasma sheath channel are carefully studied. The probability density functions, the correlation coefficient between envelope and phase, the autocorrelation function, the level-crossing rate, and the average fade duration are derived and detailed based on electromagnetic propagation theory. Two numerical examples are also used to demonstrate the effectiveness of the model. All statistical curves agree with the theoretical curves. The proposed model comprehensively considers the multipath effect, the Doppler effect, and the plasma sheath effect. It is crucial to plausibly understand the blackout problem to facilitate performance evaluations of hypersonic vehicle communication systems.

In this article, poly(aminopropyl/methyl)silsesquioxane (PAMSQ) microspheres with different polarities were first synthesized and characterized. The polarity of the PAMSQ microspheres is progressively enhanced by increasing the aminopropyl molar ratios (1–25 mol%). Then, the effect of PAMSQ microspheres with different polarities on the flowability of the model waxy oils with/without asphaltenes was studied through rheological tests, DSC analyses, microstructure observation and asphaltenes precipitating measurement. The results indicated the PAMSQ microspheres alone could spacially hinder the interactions among the precipitated paraffin crystals, thus slightly improving the flowability of the model waxy oil without asphaltenes (MO-1). The improving ability of PAMSQ microspheres deteriorates with the polarity increasing, and the MO-1 shows the best flowability after adding 200 ppm PAMSQ-1 microsphere (with the aminopropyl molar ratio at 1 mol%). To our surprise, adding PAMSQ microspheres can significantly improve the flow behavior of the model waxy oil with 0.75 wt% asphaltenes (MO-2). Based on the asphaltenes precipitation data, the PAMSQ microspheres could adsorb asphaltenes to form the PAMSQ/asphaltene composite particles in MO-2. The composite particles can play a role of the heterogeneous nucleation templates for paraffin molecules and facilitate the formation of larger and more compact wax floccules, thus enhancing the flowability of MO-2 at low temperatures. The flow improving ability of the PAMSQ microspheres for MO-2 increases with increasing the polarity of the microspheres due to the increased interactions between the microspheres and asphaltenes. The MO-2 exhibits the best flowability after adding 200 ppm PAMSQ-3 microsphere (with aminopropyl molar ratio at 15 mol%). When the polarity of the microspheres is too strong (PMASQ-4 microsphere), however, the microspheres cannot dispersed in waxy oil stably, thus inhibiting the interactions between the microspheres and asphaltenes and deteriorating the flow improving ability of the microspheres for MO-2.

A scheme for fiber-type infrared optical comb based on the difference frequency generation (DFG) method is proposed and demonstrated. All-polarization-maintaining nonlinear pulse fiber amplifications are used to generate the nearly transform-limited two-color fundamental pulses, such that precise temporal synchronization for the broadband spectra between the fundamental pulses can be stably achieved. The 3-dB bandwidth of the DFG comb achieved is $2.05~\mu \text{m}$ near $9~\mu \text{m}$ . The DFG comb can be widely tuned from 7 to $10.5~\mu \text{m}$ , where the bandwidth for any tuning position is close to the theoretical limit. Moreover, we show that it is essential to suppress the amount of the fundamental pump pulse chirp and narrow the transform-limited fundamental signal pulse for achieving the broadband and efficient DFG comb.

Despite rapid progress in DNA biosensors by employing various materials as well as techniques, most of the reported sensors are based on specific recognition of a DNA fragment, however can not perform universal measurement of DNA molecules (i.e. genomic DNA). In this work, we proposed a novel DNA biosensing method based on instantaneously electrostatic attraction (IEA) between hexaammineruthenium (III) and DNA molecules. The current variation of freely diffused Ru(NH3)63+ caused by its quick and strong static interaction with phosphate backbones was employed as a universal probe to detect DNA molecules in solution, with no need for immobilization of capture probes on the electrode. After optimization, 30 μL of 300 μM Ru(NH3)63+ solution was added onto the gold electrode with a working electrode diameter of 2 mm, and a detection limit of 3.8 ng/μL was achieved, which is equivalent to NanoDrop™ One spectrometer, the commonly used instrument for DNA quantification. Using reusable and inexpensive gold electrode, the approach provided an easy-operated sequence-independent DNA detection method, and was proved to be able to detect genomic and plasmid DNA directly.

The degradation of pharmaceuticals and personal care products (PPCPs) by the UV/H2O2 and UV/chlorine processes was compared at practical concentrations in simulated drinking water and wastewater. In pure water, the UV/chlorine process performed better than the UV/H2O2 process for the degradation of 16 PPCPs among the investigated 28 PPCPs under neutral conditions. Interestingly, the UV/chlorine approach was superior to the UV/H2O2 approach for the removal of all PPCPs in simulated drinking water and wastewater at the same molar oxidant dosage. The radical sink by oxidants and/or H2O was 2–3 orders of magnitude higher in UV/chlorine than UV/H2O2 in pure water. Thus, the UV/chlorine process was less affected by the water and wastewater matrices than UV/H2O2. In UV/chlorine, the concentration of ClO• was calculated to be ∼3 orders of magnitude greater than that of HO• in pure water, and the reactivities of ClO• with some PPCPs were as high as > 108 M−1 s−1. ClO• was mainly scavenged by the effluent organic matter (EfOM) with a rate constant of 1.8 × 104 (mg L−1)−1 s−1 in wastewater. Meanwhile, secondary radicals such as Br•, Br2•-, ClBr•- and CO3•- further contributed to PPCP degradation by the UV/chlorine process in wastewater, whose concentrations were at least 2 orders of magnitude higher than that in UV/H2O2. Compared with the UV/H2O2 process, the UV/chlorine process saved 3.5–93.5% and 19.1%–98.1% electrical energy per order (EE/O) for PPCP degradation in simulated drinking water and wastewater, respectively.

A novel nanoparticle-based fluorescence probe was developed for NF-κB transcription factor detection and in situ imaging via steric hindrance. The probe contains gold nanoparticles (AuNPs) to quench fluorescence, and nucleic acids immobilized on the surface of AuNPs to output fluorescence. In the basal state, Cy5 labeled DNA1 folds its long chain into a hairpin structure and quenches fluorescence by forcing the Cy5 fluorophore close to the surface of AuNPs. After the probe enters the cell, the NF-κB transcription factor can bind to the κB site in the DNA duplex of the nucleic acids. The steric hindrance caused by NF-κB leads to the extension of the long chain of DNA1 and the removal of the Cy5 fluorophore from the surface of AuNPs, thereby restoring the fluorescence of the probe. By measuring NF-κB in cell lysis in vitro, the probe obtains a detection limit of 0.38 nM and the linear range from 0.5 to 16 nM. Repeated measurements showed the recovery in the cell nuclear extract was between 93.38 and 109.32%, with relative standard deviation less than 5%. By monitoring the sub-localization of the Cy5 fluorophore in single cell, the probe system can effectively distinguish active NF-κB (nucleus) and inactive NF-κB (cytoplasm) through in situ imaging. The well-designed probe will make up for the shortcomings of the existing technology, and reveal the regulatory role of transcription factors in many disease processes.

An aircraft that moves through the atmosphere at hypersonic speed is covered by plasma sheath, which causes random and fast time-varying amplitude attenuation and phase fluctuation in received signals. This paper comprehensively analyzes the mechanism of the amplitude attenuation effects on a traditional phase-locked loop (PLL), which is always ignored in traditional scenarios (such as satellite telemetry and vehicle communication). Simulation results and theoretical analysis showed that traditional PLL does not work reliably for signal carrier tracking with the severe time-varying amplitude attenuation of the plasma sheath channel. In this paper, an unconventionally designed Kalman filter (KF) tracking loop that is aware of phase dynamics and amplitude attenuation fluctuation for hypersonic vehicles is proposed. To introduce time-varying amplitude attenuation into the proposed KF-based tracking loop, the amplitude attenuation is first modeled with an autoregressive model. The statistical characteristics of the amplitude and phase fluctuation are then incorporated into the state equation and observation equation. Simulation results indicate that the proposed tracking loop is stable when the signal-to-noise ratio is &minus, 10 dB with the Ka band, even in the most severe flight environment for hypersonic vehicles.

In the continuous development process, robot technology based on multimedia interactions has been widely used in aerospace, medical, education and service industries. The relationship between robots and humans is getting closer. The improvement of robot intelligence is a process of continuously learning the outside world. Since 1959, multimedia human–computer interaction technology has provided more and more technical support for human research robots. In this paper, we firstly study the characteristics of badminton competition, including the technical characteristics, tactics characteristics, and the collection requirements about on-site training. The technical description of the badminton doubles station is also completed. Furthermore, in terms of the digitalization of the gait-based sensation, the automated acquisition of the gait technology, the simultaneously with the video, and the high-speed imaging system, the system implement information is integrated. After that, badminton multimedia techniques and tactics are designed based on the extensive statistical analysis. The skills and tactics of athletes are expressed in the form of video, graphics and text. Finally, the operators can carry out the technical and tactical analysis processes through good human–computer interactions. This increases the end user’s game information. The related attention and understanding can strengthen the strength and depth of technical and tactical ability analysis. Thus, we propose the station optimization plan for badminton doubles.

The accurate initial rotor position of a permanent magnet synchronous motor (PMSM) is necessary for starting the motor, and for the position sensorless control method adopted by a PMSM control system under some working conditions. This paper presents a new method to detect the initial rotor position of a permanent magnet synchronous motor (PMSM). The method does not need a low-pass filter, and has strong robustness and a simple calculation method. According to the relationship between high-frequency current response and rotor position angle &theta, the rotor position angle can be obtained by arctangent and linear formulae. Finally, the magnetic polarity of the rotor is distinguished according to the change of inductance. In this method, the arctangent function is used to eliminate the filtering process and reduce the influence of the parameter deviation of the motor system on the detection accuracy of the initial position. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the method.

We demonstrate a facile fabrication scheme for Co3O4@CoO@Co (gradient core@shell) nanoparticles on graphene and explore their electrocatalytic potentials for an oxygen evolution reaction (OER) and an oxygen reduction reaction (ORR) in alkaline electrolytes. The synthetic approach begins with the preparation of Co3O4 nanoparticles via a hydrothermal process, which is followed by a controlled hydrogen reduction treatment to render nanoparticles with radial constituents of Co3O4/CoO/Co (inside/outside). X-ray diffraction patterns confirm the formation of crystalline Co3O4 nanoparticles, and their gradual transformation to cubic CoO and fcc Co on the surface. Images from transmission electron microscope reveal a core@shell microstructure. These Co3O4@CoO@Co nanoparticles show impressive activities and durability for OER. For ORR electrocatalysis, the Co3O4@CoO@Co nanoparticles are subjected to a galvanic displacement reaction in which the surface Co atoms undergo oxidative dissolution for the reduction of Pt ions from the electrolyte to form Co3O4@Pt nanoparticles. With commercial Pt/C as a benchmark, we determine the ORR activities in sequence of Pt/C &gt, Co3O4@Pt &gt, Co3O4. Measurements from a rotation disk electrode at various rotation speeds indicate a 4-electron transfer path for Co3O4@Pt. In addition, the specific activity of Co3O4@Pt is more than two times greater than that of Pt/C.

The reliability of DC-link capacitors in urban rail transit is considered as a major challenge because of significant maintenance impact. In this article, the DC-link capacitor reliability is researched in metro traction drive system. In the small timescale of control level, the current harmonics of multiple operating conditions and different control methods in the DC-link capacitor are discussed. The power loss is simulated by the capacitor harmonics of current and equivalent series resistance (ESR) in multioperating conditions. Considering electrothermal coupling, the time-ordered and continuity of thermal stress are analyzed to evaluate the hot spot temperature dynamic conformed to the reality. Combining with the analysis of electrical stress and thermal stress, a multitimescale capacitor reliability evaluation method is proposed. It is divided into four steps: the discrete small timescale, the single route timescale, the daily operation timescale, and the whole lifetime cycle. In the different timescales, the lifetime distribution changes with the dynamics of the complex mission profiles, so as to estimate the lifetime bottleneck of the DC-link capacitor banks with different control methods by the Weibull distribution. In addition, experimental validation is provided to verify the accuracy of the proposed method.

Background: There is a great demand for convenient and quantitative assessment of upper-limb traumatic peripheral nerve injuries (PNIs) beyond their clinical routine. This would contribute to improved PNI management and rehabilitation. Objective: The aim of this study was to develop a novel surface EMG examination method for quantitatively evaluating traumatic upper-limb PNIs. Methods: Experiments were conducted to collect surface EMG data from forearm muscles on both sides of seven male subjects during their performance of eight designated hand and wrist motion tasks. All participants were clinically diagnosed as unilateral traumatic upper-limb PNIs on the ulnar nerve, median nerve, or radial nerve. Ten healthy control participants were also enrolled in the study. A novel framework consisting of two modules was also proposed for data analysis. One module was first used to identify whether a PNI occurs on a tested forearm using a machine learning algorithm by extracting and classifying features from surface EMG data. The second module was then used to quantitatively evaluate the degree of injury on three individual nerves on the examined arm. Results: The evaluation scores yielded by the proposed method were highly consistent with the clinical assessment decisions for three nerves of all 34 examined arms (7 × 2 + 10 × 2), with a sensitivity of 81.82%, specificity of 98.90%, and significate linear correlation (p < 0.05) in quantitative decision points between the proposed method and the routine clinical approach. Conclusion: This study offers a useful tool for PNI assessment and helps to promote extensive clinical applications of surface EMG.

The influence of thermal treatment temperature on the flowability and wax deposition characteristics of Changqing waxy crude oil was researched in detail through pour point/rheological tests, a cylindrical Couette wax deposition experimental device, DSC analyses, asphaltenes stability tests, and microscopic observations. It is found that the flowability of the crude oil can be greatly improved through increasing the thermal treatment temperature. Meanwhile, the wax deposition rate of the crude oil can be outstandingly inhibited with the increase of thermal treatment temperature from 50 to 70 °C. Moreover, the flow regime can also influence the wax deposition characteristics. Under cold flow regime (22 °C/12 °C), the structure of formed wax deposits is homogeneous while the aging of the wax deposits is not obvious. Under hot flow regime (30 °C/20 °C), the aging of the wax deposits is obvious, but a heterogeneous two-layer structure exists in the formed wax deposits at the thermal treatment temperatures 50 ...

The annual changes of sediment deposition-scour on the riverbed in the Sanhuhekou-Toudaoguai Reach of the upper Yellow River during the years 1952–2010 were investigated based on runoff and sediment transport observations from the Sanhuhekou and Toudaoguai hydrological stations. Multiple influencing factors such as reservoir operations, tributary inflows, as well as runoff and sediment loads from the Shidakongdui area were analyzed. The results show that even though the sediment loads from the major sources, the Shidakongdui area as well as the upstream tributaries such as the Qingshui River and the Zuli River have reduced especially since the 2000s as a result of enhanced water-soil conservation measures and improvement of vegetation cover, the study reach was still generally in a status of cumulative aggradation. This is mainly due to the joint operations of the Liujiaxia Reservoir and the Longyangxia Reservoir, which significantly reduced the annual runoff and sediment loads at the Sanhuhekou Crosssection. The reservoirs also remarkably altered the summer flood characteristics of the study reach, inducing the shape of the annual flow curve changing from a ‘single-peak’ into a ‘double-peak’. These alternations sharply decreased the sediment transport capacity of flooding in the summer flood season which yields more than 90% of the sediment loads, leading to an unbalanced relation between the water and sediment. In addition, the estimated incoming sediment coefficient of the Sanhuhekou Crosssection ranged from 0.003 to 0.014 kg s/m6, of which 0.004 kg s/m6 was suggested as a rough critical value to determine the scour or deposition status of the study reach.

Epoxy asphalt is a thermosetting paving material that can provide higher strength, stiffness, adhesion, high-temperature stability, and service life compared to conventional asphalt; howeve...

In CO2 flooding, the dissolution of CO2 in produced fluid may change the stability of crude oil emulsion, thereby affecting the design/operation of the gathering pipeline and oil–water separation. The purpose of this study is to investigate the stability change of crude oil emulsion and its mechanisms after the dissolution of CO2. The stability of the CO2-dissolved crude oil emulsions is determined with a self-made apparatus. The mechanisms of the stability change are uncovered from interfacial properties and bulk viscosity. It is found that the stability of the crude oil emulsions is visibly reduced with an increasing dissolved quantity of CO2. This is partly attributed to the fact that dissolved-state CO2 can lessen the interfacial dilational modulus and increase the loss angle markedly, thus lowering the structural strength and elasticity of the interface. Meanwhile, the dissolution of CO2 in crude oil can reduce its viscosity, resulting in easier collision of droplets. In view of these experimental re...

The direct shear tests were conducted to study the shear performance of steel-asphalt interface by taking epoxy asphalt (EA) as waterproofing adhesive layer (WAL) material when considering temperature and relative humidity (RH) coupling. The temperatures of 30 and 60 °C and RH of 30, 50, 70 and 95% for each temperature were chosen and the steel-WAL interface, WAL-pavement interface and composite structure specimens were cured under specified temperature and RH. The research results show that the influence of RH on the shear strength of the steel-asphalt composite structure without considering the effects of temperature and RH on interfaces is negligible and the traditional shear test method should be updated. However, the interface shear strength decreases with increased RH when it exceeds 70% by considering the effects of temperature and RH on interfaces.

The effects of plasma sheath on communication signals are not only power attenuation but also multiplicative noise addition because of the sheath's instability. The fluctuation properties of time-varying electron density are crucial to comprehensively understand the blackout problem. In this paper, the fluctuation laws of time-varying electron density are first comprehensively revealed in space–time–frequency domain. A layered fluctuation model of time-varying electron density is then proposed based on these fluctuation laws. The effects of dynamic plasma sheath on electromagnetic (EM) waves at Ka band are calculated by Monte Carlo quasistatic EM numerical method. Results show that the amplitude and phase of time-varying transmission coefficient both follow Gaussian distribution, whereas the spectrum curves follow a bi-Gauss function because of the effect of second mode instability in the hypersonic boundary layer. Furthermore, the means of amplitudes increase with the increasing of the incident EM wave frequency and the decreasing of the peak electron density, while the standard deviations decrease with the increasing of incident EM wave frequency, the decreasing of the peak electron density and the decreasing of electron density standard deviation.

Hydrogenation has recently been proposed for use in modulating the magnetic properties of Pd-rich ferromagnetic (FM) alloy films. This study successfully fabricated Pd-rich Mn/MnPd/Fe antiferromagnetic/FM films with an established exchange bias field at RT, and determined that hydrogenation can enhance the exchange bias coupling in such films. Specifically, magnetic hysteresis loops revealed that the magnetic state of the Pd-rich Mn/MnPd/Fe films was gradually changed from an unbiased state to an exchange-biased state upon exposure to a hydrogen environment; moreover, hydrogenation engendered a larger magnitude of the exchange bias field than conventional field cooling. This phenomenon can be attributed to the enhanced long-range antiferromagnetic ordering of the Pd-rich MnPd film upon uptake of hydrogen atoms.

Recently, studies on the use of polymer nanomaterial composites as pour-point depressants (PPD) have drawn much attention, but the crystallization properties and improved rheological performance of waxy crude oils using nanoclay-based composite PPDs have rarely been reported. In this paper, montmorillonite (Mnt) was first organically modified using octadecyltrimethylammonium chloride (C21H46NCl, or stearyltrimethylammonium chloride) in aqueous solution. Then, the organically modified Mnt (OMnt) material was dispersed into a polyoctadecylacrylate (POA) matrix to prepare a POA/OMnt composite PPD by melt blending. The composition, structure, and morphology of Mnt, OMnt, and the POA/OMnt composite PPDs were investigated. The results showed that the OMnt and POA were compatible and that the OMnt was exfoliated into several sheets in the POA matrix. Subsequently, the isothermal crystallization kinetics of the POA/OMnt composite PPDs showed that small amounts of OMnt had a dramatic impact on POA chain motion during crystallization and facilitated POA crystallization. After it was added to a waxy crude oil, the POA/OMnt composite PPDs produced better rheological properties and performance than identical concentrations of the neat POA. The POA/OMnt composite PPDs can act as wax nucleation sites for wax molecule precipitation and result in larger and more compact wax crystal flocs, which adversely affect the formation of a wax crystal network and, thus, favor the improvement of waxy crude oil rheology.

Aim: Recently, nano–bio interactions and their biomedical impacts have drawn much attention, but nano–bacteria interaction and its function are unknown. Herein, we aim to synthesize drug-free and cationic nanoparticles (CNPs) and investigate CNP–bacteria interaction and its antibiofilm effect. Materials & methods: The bioactivity of CNPs against Streptococcus mutans was examined by colony-forming units counting and scanning electron microscopy. CNP–bacteria interaction force was measured by atomic force microscopy. Results: CNPs (217.7 nm, 14.7 mv) showed a concentration-dependent activity against bacteria. Particularly, CNPs at 200 μg/ml completely inhibited planktonic bacterial growth and biofilm formation, and disrupted ∼70% mature biofilm. CNP–bacteria interaction force was up to 184 nN. Conclusion: CNPs have great potentials for convenient local use for prevention and treatment of bacteria-related oral diseases.

In the previous work, we have reported that small dosages of the polymethylsilsesquioxane (PMSQ) microsphere can effectively improve the performance of the EVA pour point depressant (PPD) and the amount of EVA PPD adsorbed on the microsphere evidently influences the efficiency of the EVA/PMSQ composite particle. To further promote the adsorption of EVA on the microsphere and enhance the efficiency of the composite particle, here, the amino-functionalized PMSQ microspheres with different amino molar ratios (PAMSQ) are first synthesized and characterized. The flow behavior, exothermic crystallization and microstructure of the waxy crude oil undoped/doped with EVA, EVA/PMSQ and EVA/PAMSQ are systemically investigated. Results show that 50 ppm EVA PPD can greatly improve the flow behavior of the oil and small dosages (2.5 ppm) of PMSQ microsphere can significantly improve the performance of the EVA PPD. After the amino-functionalization, the flow improving efficiency of EVA/PAMSQ is further enhanced: the gelation point, G′, G″, apparent viscosity and yield stress of the oil sample decrease to a lower value. The best performance is found at adding 50 ppm EVA + 2.5 ppm PAMSQ-2 (with amino molar ratios at 15%). Compared to EVA/PMSQ, the EVA/PAMSQ exhibits a stronger nucleation effect to increase the WAT of the oil sample slightly, and outstandingly modifies the morphology of the precipitated wax crystals into larger and more compact flocs. The amino-functionalization facilitates more EVA PPDs adsorbing and concentrating on the PAMSQ microsphere, causing the formation of the EVA/PAMSQ composite particles. The composite particles provide stronger nucleation effect for the wax precipitation, resulting in larger and more compact wax microstructures and then further improving the flow behavior of the oil. The rheological improving performance of EVA/PAMSQ for the waxy crude oil increases with the increase of amino molar ratio and the efficiency of EVA/PAMSQ-2 reaches the best. When the amino molar ratio is too high (PMASQ-3), the PAMSQ-3 microsphere is unstable in oil phase and aggregates into large particle flocs, which inhibits the EVA adsorption on the PAMSQ-3 microsphere and then weakens the rheological improving efficiency of the EVA/PAMSQ-3 composite particle.

The blackout problem caused by plasma sheath is a serious obstacle to the communication system of hypersonic vehicles. The uplink relay transmission method is an effective means of mitigating serious attenuation caused by plasma sheath. This paper proposes a Ka-band $2\times2$ dual-polarization multiple-input multiple-output (MIMO) scheme by adopting a left-/right-hand circular polarized antenna to increase channel capacity and signal quality. The relay dual-polarized MIMO channel model between the hypersonic vehicle and satellite is established by emphasizing the plasma sheath effect, especially the cross-polar coupling and polar correlation under plasma sheath. Useful numerical results on the relay dual-polarized MIMO ergodic channel capacity are analyzed. Thus, significant capacity gains with respect to the conventional single-input single-output case are illustrated based on this analysis. Simulation results show that the relay dual-polarized MIMO method can increase the channel ergodic capacity by 1.9–2 times under most circumstances, and the angle between the selected relay satellite and the vehicle normal direction should be minimal. This statistical channel model can be applied to the wireless communication system design and evaluation for hypersonic vehicles.

Here, we reported that by adjusting the stirring speed, condensation pH value, precursor concentration and reaction temperature, the morphologies of the polymethylsilsesquioxane (PMSQ) microsphere could be well controlled through the two-step sol-gel synthesis. Because of the specific structural property and strong hydrophobicity, the obtained PMSQ microsphere dispersed well in the ethylene-vinyl acetate copolymer (EVA) matrix to form EVA/PMSQ hybrid. Subsequently, the thermal properties of both EVA and EVA/PMSQ hybrid were investigated through the TGA and DSC tests. The presence of PMSQ microsphere generates a significant delay in the thermal degradation processes of EVA, thus improving the thermal stability of EVA. The PMSQ microsphere also obviously increases the onset crystallization temperature and the crystallization rate of EVA, meaning that adding PMSQ microsphere enhances the crystallization ability of EVA. Finally, by applying rheological tests and microscopic observation, EVA/PMSQ hybrid was found to further improve the flow behavior of Qinghai waxy crude oil than the neat EVA did. The EVA/PMSQ hybrid can act as heterogeneous nucleation templates of wax crystals, and favor the formation of wax crystal flocs with increased size and compactness, thus inhibiting the continuous wax crystal network structure and further improving the flow behavior of the waxy crude oil.

In part 1 (10.1021/acs.energyfuels.7b03657), the synergistic effect of ethylene–vinyl acetate copolymer (EVA) pour point depressant (PPD) and rensin-stabilized asphaltenes on improving the flowability of synthetic waxy oil has been verified. This paper is a continuous work studying the effect of the asphaltene content (0.01–3 wt %) on the synergistic effect between EVA PPD and resin-stabilized asphaltenes. The results showed that, in the absence of EVA and with the increase of the asphaltene content, the precipitated wax crystals of the waxy oil tend to grow gradually from initial big needle-like to smaller and more regular (spherical-like) particles with a larger amount; therefore, adding aphaltenes can only decrease the apparent viscosity of waxy oil at the temperature range slightly lower than the wax precipitation temperature (WPT) (the precipitated wax crystal amount is low), and the temperature range is broadened by increasing the asphaltene content. When the temperature is decreased far below the W...

In this paper, the effect of POA PPD together with resin-stabilized asphaltenes on the flow behavior of model waxy oils was investigated through rheological test, DSC, microscopic observation and a...

Both polymeric pour point depressants (PPDs) and asphaltenes can improve the flowability of waxy oils. However, the effect of polymeric PPDs together with asphaltenes on the flowability of waxy oils is not clear. In this paper, the synergistic effect of ethylene–vinyl acetate (EVA) PPD (100 ppm) and resin-stabilized asphaltenes (0.75 wt %) on the flow behavior of model waxy oils (10–20 wt % wax content) was investigated through rheological tests, DSC analysis, microscopic observation, and asphaltenes precipitation tests. The results showed that the asphaltenes disperse well in the xylene/mineral oil solvent as small aggregates (around 550 nm) with the aid of resins. The EVA or asphaltenes alone moderately improve the flow behavior of waxy oils by changing the wax crystals’ morphology from long and needlelike to a large, radial pattern or fine particles, respectively. The wax precipitation temperatures (WPTs) of waxy oils are also slightly decreased by adding EVA or asphaltenes, meaning that the cocrystall...

In real crude-oil pipelines, the formed wax deposits could be heterogeneous along the radial or axial directions. However, studies on this aspect are scarce. In this paper, the effect of the polyoctadecyl acrylate (POA) wax inhibitor on the wax deposition of 10 wt % model waxy oil was investigated with the aid of an in-house wax deposition device, differential scanning calorimetry test, high-temperature gas chromatography–Fourier transform infrared analysis, and microscopic observation. The results showed that adding POA in the model waxy oil greatly modifies the morphology of precipitated wax crystals, thus greatly changing the wax deposition behavior of the oil. For oil sample 1 (without POA), the precipitated wax crystals (needle-like) more easily form porous network structures, causing the formation of a thick and porous wax deposit with relatively low WAT, wax conten,t and critical carbon number (CCN). With the increase of POA concentration (oil samples 2–5), the precipitated wax crystals become more...