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With the rapid development of social economy and the continuous improvement of people’s living standards, the demand for foods of animal origin is also increasing. The problem of veterinary drug residues in foods of animal origin has attracted more and more attention. Meanwhile, higher requirements have been raised for the supervision and inspection of veterinary drug residues. High-resolution mass spectrometry (HRMS) is a powerful tool to retrieve compounds, which can enable the non-targeted screening and confirmation of a variety of veterinary drugs without the use of standards. HRMS is an important technical means for risk monitoring and high-throughput screening of veterinary drug residues, making up for the weaknesses of triple quadrupole mass spectrometry such as poor universality and no ability to screen unknown compounds. This review summarizes the application of liquid chromatography-high resolution mass spectrometry (LC-HRMS) in the field of veterinary drug residue detection from the year 2018 to 2021, and systematically demonstrates the advantages and characteristics of HRMS. With the popularization of HRMS and the development of detection technologies, HRMS will be widely used in the field of veterinary drug residue detection as a routine method.

With the continuous improvement of wind power penetration in the power system, the volatility and unpredictability of wind power generation have increased the burden of system frequency regulation. With its flexible control mode and fast power adjustment speed, energy storage has obvious advantages in participating in power grid frequency regulation. Therefore, this paper studies the control strategy of wind energy storage combined with primary frequency regulation and proposes a control method of wind energy storage combined with primary frequency regulation based on the operation state of wind turbines. This paper analyzes the reserve power and rotor reserve kinetic energy of wind turbines operating in different wind speed ranges, introduces the fan frequency regulation operation state coefficient to quantify the real-time frequency regulation ability of the unit, regards the fan and energy storage system as independent frequency regulation sources, and designs the control strategy of joint frequency regulation of wind and storage in different wind speed ranges. The energy storage system is employed to participate in frequency control in the low-wind-speed range, thereby addressing the "blind spot" issue of wind turbine unit frequency control alone. In the medium- and high-wind-speed ranges, the real-time complementary output of wind and energy storage power is achieved by assigning weights based on the frequency control operation status coefficient. Finally, the effectiveness of the joint frequency modulation control strategy of wind storage in low-, medium-, and high-wind-speed regions is verified in the simulation model. [ABSTRACT FROM AUTHOR]

Stepwise electrocatalysis can remarkably accelerate the kinetics of two consecutive reactions in sulfur electrochemistry. However, the significant difference between the catalysis and diffusion rates of polysulfides results in persistent shuttling in the stepwise electrocatalysts. Here, a stepwise electrocatalytic strategy of catalysis‐immobilization‐deposition is proposed for achieving the consistency of diffusion and catalysis of polysulfides. Accordingly, a sandwich‐like stepwise electrocatalyst is designed, which is composed of Co nanoparticles (Co‐NP), mesoporous SiO2, and iron single atom (Fe‐SA) (denoted as Co‐NP@SiO2@Fe‐SA), serving as catalysis core, immobilization interlayer, and deposition shell, respectively. Benefitting from the dynamic equilibrium between production and consumption of polysulfides achieved by the spatial synergistic effect of the triple sites, the S/Co‐NP@SiO2@Fe‐SA cathode delivers a high reversible capacity of 731 mAh g−1 over 500 cycles at 1 C with a small capacity decay of 0.039% per cycle. Moreover, a high areal capacity of 3.8 mAh cm−2 at a sulfur loading of 4.5 mg cm−2 is achieved with a low electrolyte/sulfur ratio of 5.9. This work sheds light on a new host design concept with high catalytic activity, stability, and selectivity to enable high performance lithium‐sulfur batteries. [ABSTRACT FROM AUTHOR]

Due to the high complexity and huge difference in sulfur electrochemistry, single-atom (SA) catalysts with a single component cannot satisfy the urgent need for accelerating the complex redox process of lithium–sulfur batteries (LSBs). Herein, a dual-metal Zn–Co single-atom catalyst loaded on a double-shelled nitrogen-doped carbon material (Zn–Co SA@DNC) is designed to enable the efficient physicochemical confinement and catalytic conversion of lithium polysulfides (LiPSs). Benefiting from the synergistic effect of dual-redox sites and ingenious double-shelled structure of Zn–Co–N8–C, the catalytic energy barrier and outward diffusion of polysulfides are effectively reduced compared with the single-component counterparts (Zn SA@DNC and Co SA@DNC). When utilized as a sulfur host, the Zn–Co SA@DNC/S cathode exhibits satisfactory sulfur electrochemistry, including an excellent reversible performance of 732 mA h g−1 under 1C with a small capacity decay of 0.034% per cycle after 800 cycles and a superior areal capacity of 4.3 mA h cm−2 with a low electrolyte/sulfur ratio of 9. This work would provide a profound understanding of the catalysis mechanism of dual-metal SAs on accelerating sulfur conversion in LSBs. [ABSTRACT FROM AUTHOR]

In order to successfully study the condensation and separation of a steam–CO2 mixture, a boundary layer model was applied to the mixture condensation of steam and CO2 on horizontal and vertical plates. The modified condensation boundary layer model of steam and CO2, given the CO2 solubility in the condensate, was established, numerically solved, and verified with existing experimental data. Different condensation data of steam–air and steam–CO2 mixtures were compared, and the effect of CO2 solubility on the mixed gas condensation was analyzed under multiple pressure conditions (1 atm–10 MPa). The simulation data show that the presence of CO2 will deteriorate the condensation heat transfer, just like air. Given that CO2 is slightly soluble, some CO2 can pass through the gas–liquid interface to enter the condensate film and reduce the accumulated CO2 on the gas–liquid interface, which improves the condensation. However, the solubility of CO2 is only significant under high-pressure conditions, inducing its effects on condensation. A comparison of the condensation coefficients of the steam–CO2 mixture shows the lower impact of CO2 condensation on the horizontal plate compared to that on the vertical plate. For most conditions, the steam–CO2 mixture gas condensation heat transfer coefficient on the vertical plate surface is still larger than that on the horizontal plate surface, and the improvement in the condensation heat transfer coefficient caused by low CO2 solubility (2 or 10%) at 10 MPa on the vertical plate is also larger than that of the horizontal plate. [ABSTRACT FROM AUTHOR]

In many aeronautics and marine applications, the unsteady forces generated by propulsion rotors due to turbulence ingestion are a significant source of noise and create serious concerns. The understanding of rotor turbulence ingestion and the rotor noise generation mechanisms is vital to achieve an optimal design or apply noise control strategy. The current study is the first attempt to numerically investigate an underwater rotor ingesting grid-generated turbulence by large eddy simulation combined with the Ffowcs-Williams and Hawkings equation. The flow characteristics of two directly simulated turbulence grids with a mesh spacing of 4 and 6 in. are investigated and proved to be adequate for the rotor turbulence ingestion study. The simulated unsteady force spectra of the rotor show better agreement with the experimental results in terms of amplitudes and frequency ranges of the first haystack and broadband components compared to previous theoretical and numerical studies. The unsteady forces and noise of the rotor downstream of the 4-in. grid are slightly higher than those downstream of the 6-in. grid. A far-field noise prediction approach based on the time derivatives of the rotor axial and radial unsteady forces are investigated and validated. The far-field noise spectra and the rotor noise directivities predicted by the time derivative approach agree well with the Ffowcs-Williams and Hawkings equation in the main frequency range of underwater rotor noise. The noise directivities are found to be dominated by axial force related dipole sources. [ABSTRACT FROM AUTHOR]

The right-angled constrained channel with square-section is a typical channel configuration in many engineering fields. However, due to the high curvature of the right-angled constrained channel, the flow field parameters are not uniformly distributed, which has an adverse effect on resource utilization or reaction efficiency of the industrial process. To address the above matters, the modeling and solving method for impinging disturbance-based flow field regulation are proposed to regulate the flow field distribution. According to the design criteria of the disturbance channel, a numerical model of impinging disturbance is set up based on the mixture multiphase model and realizable k - ε turbulence model. And the pressure–velocity coupling solution strategies are conducted to quickly solve the impinging disturbance mechanism. The distribution law of the flow field parameters at different disturbance velocities is obtained to reveal the turbulence variation mechanism caused by impinging disturbance. These research results show that the disturbance vortex produced by the collision between the disturbance flow and the mainstream can affect the parameter distribution characteristics of the flow field in the constrained channel together with the backflow vortex, dean vortex, and the secondary vortex. The disturbance flow can effectively interfere with or control the vortex structure and indirectly regulate the flow field parameters to improve uniformity and energy utilization by actively regulating the disturbance velocity. [ABSTRACT FROM AUTHOR]

We experimentally studied the inscription of fiber Bragg gratings by using femtosecond (fs) laser point-by-point (PbP) technology. The effects of the focusing geometry, grating order, laser energy and grating length on the spectral characteristics of the PbP FBG were investigated. After optimizing these parameters, a high-quality first-order PbP FBG with a reflectivity > 99.9% (i.e., Bragg resonance attenuation of 37.7 dB) and insertion loss (IL) of 0.03 dB was successfully created. Moreover, taking advantage of the excellent flexibility of the fs laser PbP technology, high-quality FBGs with various Bragg wavelengths ranging from 856 to 1902.6 nm were inscribed. Furthermore, wavelength-division-multiplexed (WDM) FBG arrays consisting of 10 FBGs were rapidly constructed. Additionally, a Fabry-Perot cavity was realized by using two high-quality FBGs, and its birefringence could be reduced from 3.04 × 10−5 to 1.77 × 10−6 by using a slit beam shaping-assisted femtosecond laser PbP technology. Therefore, such high-quality FBGs are promising to improve the performance of optical fiber sensors, lasers and communication devices. [ABSTRACT FROM AUTHOR]

Rational design of cost-effective and efficient bifunctional oxygen electrocatalysts for sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is urgently desired for rechargeable metal–air batteries and regenerative fuel cells. Here, the Fe3C nanoparticles encapsulated in N and F codoped and simultaneously etched graphene/CNTs architecture catalyst (Fe3C@N-F-GCNTs) was synthesized by a simple yet cost-effective strategy. The as-prepared Fe3C@N-F-GCNTs exhibited excellent ORR and OER performances, with the ORR half-wave potential positive than that of Pt/C by 14 mV, and the OER overpotential lowered to 432 mV at the current density of 10 mA·cm−2. In addition, the ΔE value (oxygen electrode activity parameter) increased to 0.827 V, which is comparable to the performance of the best nonprecious metal catalysts reported to date. When it was applied in a Zn–air battery as a cathode, it achieved a peak power density of 130 mW·cm−2, exhibiting the potential for large-scale applications. [ABSTRACT FROM AUTHOR]

High-accuracy temperature measurement plays a vital role in biomedical, oceanographic, and photovoltaic industries. Here, a highly sensitive temperature sensor is proposed and demonstrated based on cascaded polymer-infiltrated Mach–Zehnder interferometers (MZIs), operating near the dispersion turning point. The MZI was constructed by splicing a half-pitch graded index fiber (GIF) and two sections of single-mode fiber and creating an inner air cavity based on femtosecond laser micromachining. The UV-curable polymer-infiltrated air cavity functioned as one of the interference arms of MZI, and the residual GIF core functioned as the other. Two MZIs with different cavity lengths and infiltrated with the UV-curable polymers, having the refractive indexes on the different sides of the turning point, were created. Moreover, the effects of the length and the bending way of transmission SMF between the first and the second MZI were studied. As a result, the cascaded MZI temperature sensor exhibits a greatly enhanced temperature sensitivity of −24.86 nm/°C based on wavelength differential detection. The aforementioned result makes it promising for high-accuracy temperature measurements in biomedical, oceanographic, and photovoltaic applications. [ABSTRACT FROM AUTHOR]

When the traditional TEB (time elastic band) algorithm is used to plan the path in a complex dynamic environment, path vibrations caused by the unsmooth speed control amount will occur, which will bring greater impact to the robot and prone to collisions. Aiming at the above problems, the traditional TEB algorithm is improved. The detected irregular obstacles are expansion treatment and regional classification strategy, and the driving route in the safe area is given priority to make the robot run more safely and smoothly in the complex environment. Adding the obstacle distance to the speed constraint in the algorithm can effectively reduce the vibration amplitude and the impact of the robot during the path driving process caused by the speed jump after the robot approaches the obstacle, so as to ensure the safety of the robot during operation. A large number of comparative simulations in the ROS environment show that in a complex dynamic environment, the path planned by the improved TEB algorithm is safer and smoother, which can effectively reduce the impact of the robot. [ABSTRACT FROM AUTHOR]

Unmanned ground vehicles (UGVs) are important elements in the future intelligent transportation system (ITS), which is supposed to conduct various tasks for human beings. Obviously, the traditional edge-side (vehicle-side) dynamics control system strictly limits the performance improvement of multifunctional UGVs in various applications. Therefore, this article proposes a future ITS with multifunctional UGVs and a cloud-edge combined, big-data-driven dynamics control approach for UGVs to improve safety. The proposed cloud-edge combined control method is achieved based on big data machine learning optimization in the cloud-side controller and feedforward-feedback lateral dynamics control in the edge-side controller. In the cloud-side controller, the big data generated during the operation of the UGVs are stored and mined by the cloud brain control center to optimize the controller parameters of the edge-side controller to improve the dynamic performance and safety of the UGVs. Finally, the proposed cloud-edge combined controller is validated based on the experiments of a real UGV testbed. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) have become an important research topic due to their wide range of applications and potential to meet the future air transportation demands. In many configurations of UAVs, the rotors interact with the wake of upstream bodies, which is of pivotal importance to the aerodynamic and aeroacoustic performance. The studies of flow structures and noise sources for rotors interacting with adjacent upstream bodies at Reynolds numbers lower than 105, which is the operating condition of most small UAVs, are limited. In the current study, numerical simulations are conducted to investigate the interaction between a rotor and the wake of an airfoil at low Reynolds numbers around 104 using the Spalart–Allmaras delayed detached eddy simulation method and acoustic analogy based on Farassat's formulation 1 A. The results show that the axial forces and the surface pressure perturbations of the airfoil are closely coupled with the rotor rotation. The effect of interaction on the rotor blades depends on the relative angle of attack. Furthermore, an analysis of the surface pressure fluctuations corresponding to the noise sources shows that the tonal noise at the blade passing frequency and its harmonics is mainly caused by periodical interaction, and the high-frequency noise is produced by the shedding vortex at the trailing edge of the rotor. [ABSTRACT FROM AUTHOR]

Inferior specific capacity and sluggish redox kinetics are the most stubborn problems lithium-ion and lithium-sulfur batteries (LIBs and LSBs) are facing, respectively. Here we report a facile fabrication of self-supported hollow Co 3 O 4 @carbon nanotubes on carbon cloth (H-Co 3 O 4 @CNT/CC) through a mild pyrolysis-oxidation process. The additive- and binder-free H-Co 3 O 4 @CNT/CC shows excellent electrochemical performances as both LIBs and LSBs electrodes. As a robust integrated anode for LIBs, the areal capacities are 2.72 mAh cm−2 at the current density of 0.5 C over 1000 cycles. While as a durable cathode host for LSBs, favorable areal capacities of 2.37 mAh cm−2 are maintained with a low capacity decay of 0.11 % per cycle at the sulfur loading of 6 mg cm−2 and current density of 1 C after 400 cycles. Electrochemical technology, ex situ Raman spectroscopy and DFT calculations are performed to comprehensively analyze H-Co 3 O 4 @CNT/CC via thermodynamics and kinetics. It is demonstrated that the hierarchically hollow interior structure, strong adsorb ability of Co 3 O 4 toward polysulfides and three-dimensional (3D) inter-connected conductive carbon framework are responsible for the high areal capacity, fast redox kinetics and cycling durability. [Display omitted] • The integrated electrode possesses the merits of hollow nanostructured Co 3 O 4 and 3D inter-connected conductive network. • Electrochemical technology and DFT calculations are performed to comprehensively analyze H-Co 3 O 4 @CNT/CC. • H-Co 3 O 4 @CNT/CC delivers high areal capacities of 2.72 mAh cm-2 after 1000 cycles at 0.5 C as anode. [ABSTRACT FROM AUTHOR]

In recent decades, the Timed Elastic Band (TEB) algorithm is widely used for the AGV local path panning because of its convenient and efficiency. However, it may make a local detour when encountering a curve turn and cause excessive energy consumption. To solve this problem, this paper proposed an improved TEB algorithm to make the AGV walk along the wall when turning, which shortens the planning time and saves energy. Experiments were implemented in the Rviz visualization tool platform of the robot operating system (ROS). Simulated experiment results reflect that an amount of 5% reduction in the planning time has been achieved and the velocity curve implies that the operation was relatively smooth. Practical experiment results demonstrate the effectiveness and feasibility of the proposed method that the robots can avoid obstacles smoothly in the unknown static and dynamic obstacle environment. [ABSTRACT FROM AUTHOR]