[en] A new strategy for the facile synthesis of very stable and mono-dispersed silver (Ag) quantum dots (QDs) is developed by laser fragmentation of bulk Ag in water using polysorbate 80 as a dispersing and stabilizing agent. The surfactant plays an important role in the formation of size-controlled Ag nano-structures. The Ag QDs have excellent photo-stability of ∼500 h and enhanced photoluminescence (PL) at 510 nm. This has significant implications for selective and ultrasensitive PL probes. Based on laser fragmentation in the biocompatible surfactant solution, our results have opened up a novel paradigm to obtain stable metal QDs directly from bulk targets. This is a breakthrough in the toxicity problems that arise from standard chemical fabrication. (paper)

[en] Highlights: • A novel evacuated tube solar high temperature air heater is designed. • The solar air heater system consists of 30 linked collecting units. • Every unit consisted of a evacuated tube, a simplified CPC and concentric tube. • The flow air is heated over temperature of 200 °C. - Abstract: A set of evacuated tube solar high temperature air heaters with simplified CPC (compound parabolic concentrator) and concentric tube heat exchanger is designed to provide flow air with a temperature of 150–230 °C for industrial production. The solar air heater system consists of 30 linked collecting units. Each unit includes a simplified CPC and an all-glass evacuated tube absorber with a concentric copper tube heat exchanger installed inside. A stainless steel mesh layer with high thermal conductivity is filled between the evacuated tube and the concentric copper tube. Air passes through each collecting unit, and its temperature increases progressively. An experimental investigation of the thermal performance of the air heater is performed, and the experimental results demonstrate the presented high-temperature solar air heater has excellent collecting performance and large output power, even in the winter. The measured thermal efficiency corresponding to the air temperature of 70 °C reaches 0.52. With the increase of air temperature, thermal efficiency reaches 0.35 at an air temperature of 150 °C, and 0.21 at an air temperature of 220 °C.

[en] A composite film based on K₈P₂W₁₆V₂O₆₂·18H₂O decorated by Au–Pd nanoparticles was prepared by the layer-by-layer self-assembly method. This composite film exhibits enhanced electrocatalytic performance, repeatability and long-term stability for the simultaneous determination of dopamine and ascorbic acid at biological pH (pH 7.0). The proposed electrochemical sensing film for simultaneous detecting dopamine and ascorbic acid shows rather low detection limit of 8.3 × 10⁻⁷ and 4.3 × 10⁻⁷ M and a linear response range from 2.1 × 10⁻⁶ to 2.06 × 10⁻³ M and 1.2 × 10⁻⁶ to 1.61 × 10⁻³ M, as well as no interference from the common interfering species at an applied potential. -- Abstract: A novel composite film based on Dawson-type phosphovanadotungstate K₈P₂W₁₆V₂O₆₂·18H₂O (P₂W₁₆V₂) decorated by Au–Pd alloy nanoparticles (Au–Pd) was fabricated on quartz, silicon and ITO using the layer-by-layer self-assembly method. The composite film was characterized by UV–vis spectroscopy, X-ray photoelectron spectra, atomic force microscopy, Scanning electronic microscope, cyclic voltammetry and differential pulse voltammetry. The composite film can be employed for sensitive and simultaneous determination of dopamine and ascorbic acid at biological pH (pH 7.0). Linear analytical curves were obtained in the ranges from 2.1 × 10⁻⁶ to 2.06 × 10⁻³ M and 1.2 × 10⁻⁶ to 1.61 × 10⁻³ M for dopamine and ascorbic acid by DPV methods, respectively. The low detection limit for dopamine and ascorbic acid were 8.3 × 10⁻⁷ and 4.3 × 10⁻⁷ M, as well as no interference was observed from the common interfering species such as glucose, uric acid, L-cysteine, CH₃OH, CH₃CH₂OH and H₂O₂. The composite film was used for dopamine and ascorbic acid determinations in real samples with satisfactory results. With high sensitivity and selectivity, the proposed electrochemical sensor would provide a simple method for simultaneous determination of dopamine and ascorbic acid in practical applications

[en] This paper considers an LG–Holling type II diseased predator ecosystem with Lévy noise and white noise. In this prey–predator system, assuming that the predator population is infected by disease and divided into two classes: susceptible predator and infected predator, we show that the system has a unique global positive solution. We investigate the persistence in the mean and extinction for the population, obtain threshold conditions of extinction, persistence in the mean by Itô’s formula and a comparison theorem for the stochastic system. In addition, we discuss the uniform boundedness of pth moment with $p>0$ and reveal the stochastically ultimate boundedness of the system. Finally, some numerical simulations are introduced to illustrate our analytical findings.

[en] With the continuous development of electric vehicles, a large number of electric vehicles have connected to the grid. This impacts the security and economic operation of power systems deeply. When large-scale electric vehicles are charging, it will bring the problem of electricity load growth and cause the peak-valley difference of power grid. The paper analyzes the impact of electric vehicles quick charge on power quality. According to Monte Carlo method, the daily load curve of quick charging mode in Beijing in 2030 is set up. Newton Raphson method and forward-backward substitution method are used to analyze the voltage deviation and power loss of each node in the typical power system. (paper)

[en] In the framework of the circular restricted three-body problem, the center manifolds associated with collinear libration points contain all the bounded orbits moving around these points. Semi-analytical computation of the center manifolds and the associated canonical transformation are valuable tools for exploring the design space of libration point missions. This paper deals with the refinement of reduction to the center manifold procedure. In order to reduce the amount of calculation needed and avoid repetitive computation of the Poisson bracket, a modified method is presented. By using a polynomial optimization technique, the coordinate transformation is conducted more efficiently. In addition, an alternative way to do the canonical coordinate transformation is discussed, which complements the classical approach. Numerical simulation confirms that more accurate and efficient numerical exploration of the center manifold is made possible by using the refined method. (paper)

[en] A megawatt-level subterahertz surface wave oscillator (SWO) is proposed to obtain high conversion efficiency by using separated overmoded slow wave structures (SWSs). Aiming at the repetitive operation and practical applications, the device driven by electron beam with modest energy and current is theoretically analyzed and verified. Then, the functions of the two SWS sections and the effect of the drift tube are investigated by using a particle-in-cell code to reveal how the proposed device achieves high efficiency. The mode analysis of the beam-wave interaction region in the device is also carried out, and the results indicate that multi-modes participate in the premodulation of the electron beam in the first SWS section, while the TM₀₁ mode surface wave is successfully and dominantly excited and amplified in the second SWS section. Finally, a typical simulation result demonstrates that at a beam energy of 313 keV, beam current of 1.13 kA, and guiding magnetic field of above 3.5 T, a high-power subterahertz wave is obtained with an output power of about 70 MW at frequency 146.3 GHz, corresponding to the conversion efficiency of 20%. Compared with the results of the previous subterahertz overmoded SWOs with integral SWS and similar beam parameters, the efficiency increases almost 50% in the proposed device. (paper)

[en] Enantiomeric separations of the adrenergic compounds adrenaline, noradrenaline, and isoprenaline were studied. Electromigrative separations were performed in uncoated fused silica capillaries using streptomycin-modified gold nanoparticles (ST-AuNPs) as an additive to the background electrolyte. The ST-AuNPs are shown to serve as an effective chiral selector. The modified AuNPs were characterized in terms of size and zeta potential, and by IR and UV-vis spectra. The effects of ST-AuNP concentration, pH value, temperature, and separation voltage on the separations were systematically studied. Under optimized experimental conditions, racemic mixtures of the respective adrenergic drugs were baseline-separated within 7 min with a resolution of up to 7.5. The relative standard deviations of the resolution in inter-day and intra-day studies (n = 5) were generally <5%. .

[en] Highlights: • A review on the cold energy storage. • The classification of cold storage technologies and applications are introduced. • The phase change materials are introduced. • The main work is focused on cold storage technologies or applications in air conditioning. -- Abstract: Cold energy storage technology using solid–liquid phase change materials plays a very important role. Although many studies have covered applications of cold energy storage technology and introductions of cold storage materials, there is a relatively insufficient comprehensive review in this field compared with other energy storage technologies such as hot energy storage. This review introduced the air condition with cold storage devices, conducted a classified study on various cold storage technologies or applications and introduced these cold storage technologies and phase change materials whose phase change temperatures are in the range of 7–14 °C in detail. Meanwhile, the key issues to be solved in further research on cold storage technology are proposed. The results of the limited available references have shown that cold storage technology using PCMs has great potential in various fields; however, the present research work is still in its initial stage and requires further development.

[en] The net-baryon number is essentially transported by valence quarks that probe the saturation regime in the target by multiple scattering. The net-baryon distributions, nuclear stopping power and gluon saturation features in the SPS and RHIC energy regions are investigated by taking advantage of the gluon saturation model with geometric scaling. Predications are made for the net-baryon rapidity distributions, mean rapidity loss and gluon saturation features in central Pb + Pb collisions at LHC.