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In this paper, a novel nonsingular finite-time backstepping controller is constructed for trajectory tracking of marine vessel subject to unknown external disturbances. Firstly, in the presence of disturbances, a disturbance observer (DO) is proposed to estimate and compensate the disturbances exactly in finite time. Secondly, a finite-time tracking controller is designed in the classical backstepping procedure, however, the inevitable singularity appears in calculating the derivative of virtual control. Furthermore, for overcoming this singularity, a nonsingular finite-time backstepping controller is designed by adopting a finite-time command filter to estimate the derivative, instead of calculating it directly. Theoretical analysis demonstrates the closed-loop system is finite-time stable. Finally, simulation results and comparisons illustrate the effectiveness of the proposed method.

Reduced graphene oxide wrapped hollow molybdenum trioxide nanorods (MoO 3 @rGO) have been fabricated by a facile process. The MoO 3 @rGO shows improved lithium storage performance. It could deliver a high reversible capacity (842 mAh/g at 0.1 A/g), excellent cycling stability (778 mAh/g at 0.1 A/g after 200 cycles) and excellent rate capability (455 mAh/g at 2 A/g). The excellent electrochemical performance could be attributed as the special core (MoO 3 )/sheath (rGO) structure, which could accommodate the volume change of MoO 3 during lithiation/delithiation process. In addition, the rGO coating layer could improve the electronic conductivity of MoO 3 .

This project uses the Peltier effect to optimize the temperature control system of the thermostat, uses semiconductors to generate temperature differences, and then forms a heat pump, uses the conversion between high and low taste energy to replace the compressor for refrigeration and temperature adjustment, and at the same time uses the gas vortex characteristics to exchange gas and Adapt and improve the heat dissipation and other aspects. The incubator designed in this project is more excellent in terms of energy saving, low noise and service life, and improves the utilization of energy and resources. At the same time, the temperature control of the incubator has the advantages of stability and accuracy, which can effectively solve the problem of food and medical the deterioration and loss of supplies.

Heteroatom-doped carbon nanomaterials with well-defined porous are used as anode materials for SIBs due to their exceptional structural characteristics. In this work, porous N-doped carbon networks composed with ultrathin carbon nanosheets were synthesized via the direct pyrolysis of Vitamin B5. The content of nitrogen, specific surface area, porous structure of the N-doped carbon nanosheet networks were adjusted by changing reaction temperatures. The formation mechasim of the ultrathin N-doped carbon nanosheet networks was also proposed. The generation of calcium carbonate/calcium oxide used as a self-template renders the formation of the porous structure via thermal treatment. The optimized samples possess a superior lithium and sodium storage: 1534 mAh g −1 at 100 mA g −1 vs. Li/Li + and 335 mAh g −1 at 100 mA g −1 vs. Na/Na + , with nearly 100% cycling Coulombic efficiency, remarkable cycling retention and high rate capacity. Additionally, good electrocatalytic activity for ORR via a 4e −1 pathway determines that the resulting primary Zn-air battery showed high discharge power energy density (80 mW cm −2 ), high reversibility and stability over continuous cycles.

An experimental study on a rotating detonation engine model using hydrogen/air mixture as propellant was conducted to analyze the initiation characteristics of detonation wave. Three ignition methods, including the ordinary spark plug, high-energy spark plug and thermal-jet tube, were used in the tests. The initiation process of rotating detonation wave was recorded and analyzed by a high frequency pressure measurement system and high-speed photographs. Operating range of the model engine was determined by series of experiments. Results indicate that the model engine could be successfully run by all the three ignition methods. Although the detonation formation time using spark plugs is quite stochastic, increasing the ignition energy can reduce the formation time of the detonation wave. Among the three ignition methods, thermal-jet provides the shortest detonation formation time. It is also found that the operating characteristic of the model engine is independent of the ignition device in the same operating condition. Three operation modes of the engine model have been observed, which are failed initiation of the detonation, unstable detonation and continuous rotating detonation. The experimental results show that the stable operating range can be extended by increasing the fuel mass flow rate.

This paper uses DPM model in Fluent to divide the mesh and conduct fluid analysis for the existing family filter, by using the Rosin - Rammler distribution simulated reality of different diameter of the plastic particles’ distribution in the water. Secondly, using particle tracking algorithm to calculate the distribution of particle diameter of the export, so as to check the existing household filter’s ability for the different plastic particle diameter.

A hollow cathode configuration was designed for a Grimm-type glow discharge atomic emission spectrometer (GD-AES). The operating conditions including the hollow cathode dimension, applied pulsed voltage and argon pressure, were optimized. The 10-μs pulses at 1.8 kV in a 3-torr discharge worked best. A pulsed hollow cathode Grimm discharge (HCG) offers several advantages: efficient excitation and ionization; high sensitivity; temporal spectral resolution; and rapid sample interchange. The capability of this source for the determination of elemental composition in metals, alloys and in solution residues is investigated. Samples used in this study included copper and steel standards.

The already established technique of pulsed glow discharge spectroscopy is extended in these studies to the application of a second pulse applied at a variable delay after a first pulse. The net discharge then consists of a series of double pulses in which each second pulse in the series enhances the emission intensity of the analyte atoms produced by the first pulse. A copper hollow cathode is used to show high emission enhancement for atom and ion lines of the sputtered species and the neon discharge gas species. The technique shows promise for further study by both atomic emission and mass spectrometry.

A high voltage, microsecond regime, pulsed glow discharge has been applied to a standard Grimm type source on a LECO SA-2000 multichannel optical spectrometer. The spectrometer system has been equipped with fast time-resolved electronics in order to study the temporal response of the elemental emission lines. The aim of the research was to investigate possible gains in signal-to-background ratio (S/B) and detection limits compared to a conventional direct current (dc) mode of operation. It was found that the high instantaneous pulse power in itself gives approximately a factor 2 increase in S/B. By utilising time-resolved detection, gains in the range 5–10 are achieved. For nitrogen, it was found that the background from leakage of air could be reduced to approximately 1/3 compared with the dc mode. Another interesting observation was that certain nearly non-conducting materials, which cannot be run in dc mode, could be run in the microsecond pulsed mode.

A high voltage, microsecond regime pulse dc glow discharge was applied to a standard Grimm source on a modified LECO SA-2000 direct reader spectrometer and to a duplicate Grimm source coupled to a scanning monochromator. The effects of experimental conditions, including pulse voltage, pulse frequency, pulse width and Ar pressure, on Cu atomic and ionic emission intensities were examined and compared with continuous discharge results. The pulsed Grimm source has a higher sputtering rate, greater signal intensity and lower detection limits. The pulsed signal for atomic lines shows a different temporal response from ionic lines. Pulsed Grimm GD-AES also offers control features advantageous in the measurement of thin surface layers.

A thermospray nebulizer was used as a sample introduction device for microwave plasma torch (MPT) atomic emission spectrometry (AES). Experimental parameters, including the power supplied to the MPT, the flow rates of support and carrier gases, the observation height, the sample uptake rate, the thermospray working temperature, the temperature of the aerosol spray chamber and cooling water were optimized. Under optimum conditions, the relative standard deviation (RSD) of 10 measurements for 21 elements is in the range 0.3–2.0%. The detection limits were improved in comparison with the ultrasonic nebulizer as sample introduction technique for MPT–AES. The inclusion of 20% methanol into the MPT showed there is no effect on the stability of MPT discharge. The technique can thus be held to have the potential for interface to reverse-phase HPLC systems.

Palladium salts can be used as a coprecipitation carrier for the preconcentration of trace elements from natural water prior to their measurement by atomic spectrometry (AAS). The palladium is subsequently reduced by the introduction of hydrogen gas into the sample solution. The procedure is applied to the determination of Cu, Pb and Cd in seawater (enrichment factor 50) and synthetic water samples. Operating conditions have been optimized for the analysis of real samples. With the technique established an enrichment factor (500 fold) is feasible in synthetic samples. The recoveries of Cu, Cd and Pb from seawater are 95, 103 and 100%, respectively. This simple and rapid method can be applied in a wide pH-range and with complex matrices.

The determination of metal concentrations in fish with ICP-AES and FAAS was performed. Based on the metal concentrations found in fish collected from four regions of south China, principal component analysis was applied to a bioindicator study. The relationships between metal concentrations in fish tissues and those in seawater were studied by a simulated experiment. Using these relationships, the accumulation factors were determined, and the mean concentrations of Zn, Cd, Cu, and Pb in the coastal seawater of Min Jiang estuary, Dong Shan island, Me Zhuong island, and Hai Tan island were estimated.

Based on the M 2 -factor concept and the equivalence between a beam generated by a gaussian Schell-model (GSM) source and a mixed-mode laser (MML) beam, a simple method is presented to estimate the number of effectively oscillating modes and the corresponding weighting factors of MML beams simultaneously.

A flexible and free-standing porous carbon nanofibers/selenium composite electrode (Se@PCNFs) is prepared by infiltrating Se into mesoporous carbon nanofibers (PCNFs). The porous carbon with optimized mesopores for accommodating Se can synergistically suppress the active material dissolution and provide mechanical stability needed for the film. The Se@PCNFs electrode exhibits exceptional electrochemical performance for both Li-ion and Na-ion storage. In the case of Li-ion storage, it delivers a reversible capacity of 516 mAh g−1 after 900 cycles without any capacity loss at 0.5 A g−1. Se@PCNFs still delivers a reversible capacity of 306 mAh g−1 at 4 A g−1. While being used in Na-Se batteries, the composite electrode maintains a reversible capacity of 520 mAh g−1 after 80 cycles at 0.05 A g−1 and a rate capability of 230 mAh g−1 at 1 A g−1. The high capacity, good cyclability, and rate capability are attributed to synergistic effects of the uniform distribution of Se in PCNFs and the 3D interconnected PCNFs framework, which could alleviate the shuttle reaction of polyselenides intermediates during cycling and maintain the perfect electrical conductivity throughout the electrode. By rational and delicate design, this type of self-supported electrodes may hold great promise for the development of Li-Se and Na-Se batteries with high power and energy densities.

In this paper, a thin-disk laser with the output power of kW level is demonstrated. The laser used is Nd:YAG laser medium for easiness to reach the threshold power densities of the pump and less heat to dissipate from the crystal. The thin disk of 1 mm thickness with 1.5-at. % Nd doped and a simple 4-pass pump coupling system is designed to fulfill the total absorption of the pump light. 2D-stacks diode array works as the pump source and a conventional optics is used for efficient and uniform pumping.

A diode-laser side-pumped E-O Q-switched TEM00 Nd:YAG slab laser that uses a large N.A. cylindrical lens and a thin slab pumping geometry has been investigated. The pumping scheme has the ability to match well the pump beam to the laser's fundamental transverse mode in two axes. Approximately 1.1 times diffraction limited laser beam is obtained. The slope efficiency is 31% and 18.9% at long-pump and Q-switched operation, respectively.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The diode laser side pumped E-O Q-switch Nd:YAG laser was described that produced energy O.36-mJ/pulse. 7-nspulse width ,pulse repetition rates 50-Hz, TEM00 mode.The laser has a zigzag slab geometry, side pumped with a quasi- cw 15Wdiode bar. We used a 1 .1%Nd:YAG Brewster-cut seven-bounce thin trapezoidal slab that was 1 .2mm thick.Using a cylindrical lens (f=1 .6nim),it made the diode laser couple in the slab. The laser resonator was a plane-concavecavity, radius of mirror curvature was 3m. The cavity length was about 20cm. The plane output mirror transitivity was T=0. 1 . Wedecided to the beam quality M2=1 . 1 . Q-switchlaser slope efficiency was 19%. keyword solid-state lasers, side pumped, diode laser, single transverse mode 1 .INTRODUCTION Diode-laser(LD) pumped solid-state lasers have been one ofthe most interesting and significant developments in laserengineering in recent years1. LD pumping offered high reliability, efficiency and compactness. Side pumping has been togenerate the fundamental transverse mode efficiently2. Recently a side pumping technique used in Q-switch cavity-dumpedand E-O Q-switch laser3 demonstrated efficiency side-pumped operation while still maintaining TEM00 operation. Wereported on a E-O Q-switched laser that used a numerical aperture(NA>1) and short focus length (f=1 .6mm) cylindricallens coupler thin Nd:YAG thin trapezoidal slab and generated 0.36-mJ, 7-ns, TEMo0. pulse repetition rates 50Hz whileusing