[en] In this literature, we propose an active terahertz 1D photonic crystal, which consists of silicon layers and air layers. A graphene sheet is embedded at the interface between dielectric and air. Tunable photonic band gap is realized by changing the Fermi level of graphene. Transmission Matrix Method is utilized to explain the influence of the graphene layer. We also demonstrate that a dielectric slab attached with a thin sheet made of single-negative metamaterial acts like a pure dielectric slab with a thinner thickness. A tunable blue shift of the band gap can be realized by simply applying different chemical potentials on the graphene sheet. This feature can be utilized for the design of tunable high-gain antenna array and force generator in terahertz band. - Highlights: • A novel PhC embedded with grapheme sheets is presented, tunable defect is realized. • The mechanism of the tunable defect is explained using the change of equivalent thickness. • The electromagnetic force of a slab is calculated, which indicates the structure can serve as a tunable force generator.

[en] Highlights: • Novel metamaterial based on the coupling effect of a dielectric trimer is proposed. • The phenomenon of vanishing mode is explained by the zero-sum effect. • Due to the vanishing mode, the bandwidth of the dielectric trimer has been expanded to 37%. - Abstract: In this paper, a novel periodic 2D all-dielectric metamaterial based on dielectric trimer is proposed. The electromagnetic responses are explained by the corrected equations of motion using coupled mode theory (CMT). An abnormal vanishment mode phenomenon is also discovered and explained using the zero-sum effect of magnetic dipole, by which the relative bandwidth of the metamaterial has been improved significantly compared with other structures. The presented design is easy for fabrication and can be applied in microwave region by scaling the dimensions of the cubes.

[en] Nitrogen and silicon co-incorporated DLC (N-Si-DLC) films were deposited by RF-CVD method, and the humidity effect on the tribological properties was investigated by a ball-on-disk type reciprocating tribometer in air environments at the relative humidity of 15, 45 and 75%. The chemical state of the elements and the bonding configurations were determined by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. Nano-indentation tests were performed to measure the hardness and modulus. The internal stress of the films was calculated by the Stoney equation. The characterization results showed that the N and Si contents were in the range of 4.4–10.3 at.% and 7.5–8.7 at.%, respectively. By co-doping N and Si, the internal stress of the films was reduced markedly, although with a slight reduction in the hardness and modulus. The N-Si-DLC films co-doped with a small amount of N exhibited lower friction and wear compared with the Si-DLC films without doping N. Also, these films showed low frictional sensitivity to the environmental humidity. The formation of C=N and C≡N groups with strong electron withdrawing ability is thought to contribute to reducing the friction and wear, since they are strong electron acceptors which can reduce the electron density and nucleophilic reactivity of the dangling bonds formed on the film surface during sliding. - Highlights: • Internal stress of diamond-like carbon (DLC) films is markedly reduced by N and Si co-doping. • Co-doping small amount of N is beneficial for reducing friction and wear of the films. • N and Si co-doped DLC films show low frictional sensitivity to air humidity. • CN groups act as electron accepter to reduce the activity of dangling bonds.

[en] At present, the constant-power heating belt used in domestic uranium enrichment plant needs temperature control system. This system is complex. Whether the temperature control or temperature measurement link is abnormal, it may pose a threat to system safety. Through investigation and related experiments, the feasibility of the application of self-regulation heating belt in uranium enrichment plant is proved. Provide reference for the future work. (authors)

[en] As an important pressure regulating device in the cascade system, the electric control valve directly determines whether the entire cascade system can be economically and stably operated. The design performance of electric control valve includes many aspects, but the research on improving its control performance mainly focuses on control algorithm optimization. At present, the electric control valves in the cascade system are all using a single closed-loop PID control algorithm. However, the PID control algorithm has poor control effect on nonlinear and time-varying system. Therefore, this article proposes to use the RBF-PID control algorithm, which can adjust the PID control parameters online according to the input amount, to improve the control performance of the electric control valve. The simulation results show that the RBF-PID algorithm can control the system to enter the steady state more quickly, and the amplitude of the controlled pressure fluctuation is small. (authors)

[en] Starting from the practical production and operation of centrifugal cascade, based on the value function formula, the expression of separation work loss due to abundance fluctuation in concentrate receiving container is drawn, which indicates that the abundance fluctuation will lead to the separation work loss in the concentrate container, and has a linear relationship with the total weight of concentrate, whereas a quadratic function relationship with the abundance fluctuation. It is also analyzed whether the variation of various factors causing the fluctuation of concatenated concentrate abundance will cause the change of separation work loss in cascade. The analysis shows that the parameter of change will influence the pressure and the flow rate of cascade internal unit, which will be readjusted automatically and enter a new steady state. As a result, the cascade deviates from the ideal condition, the separation capacity decreases and the mixed separation power loss increases accordingly. Therefore, the optimization strategy for the abundance control of concentrate flow products is put forward. In the actual operation in the future, the abundance fluctuation should be controlled in a given range, and the variation of parameters affecting the abundance of the product should be diminished as much as possible in order to reduce the loss of separation work. (authors)

[en] Dielectric barrier discharge in helium at atmospheric pressure was studied by taking fast images of the discharge during one current pulse using an intensified charge couple device. It was observed that there appears a weakly luminous layer close to the anode at the very beginning of the discharge, then the luminous area gradually expands into the entire gap as the anode layer moves toward the cathode, and finally a highly luminous layer forms close to the cathode at the time around the maximum of the current pulse. The evolution of the discharge pattern indicates a transition from Townsend discharge to glow discharge

[en] Objective: To investigate the feasibility and plan quality of the image-guided volumetric modulated arc therapy (VMAT) based voluntary deep exhale breath-holding technique in the stereotactic ablative body radiotherapy (SABR) for liver tumors. Methods: Fifteen patients with liver tumors were involved in this study. All patients were immobilized with voluntary deep exhale breath hold (vDEBH) combined with real-time position management (RPM) respiratory gating system. Treatment was planned using VMAT with 2 modified partial arc and re-planned using intensity modulated radiation therapy (IMRT) technique for comparison. Dosimetric parameters were calculated for plan quality assessment. Quality assurance studies included absolute dose and multiple planar dose verifications, total monitor units and delivery time analysis. Daily cone beam computed tomography imaging was used to verify the motions. Results: There were no significant dosimetric differences between VMAT and conventional IMRT plans(P > 0.05). Both techniques were able to minimize doses to organs at risk including normal liver, kidneys, spinal cord, and stomach. However, the average monitor units with VMAT were significantly lower 28.1% than those with IMRT(t = 3.064, P < 0.05). The average beam-on time in VMAT plans was 31.6% shorter than that in IMRT plans(t = 2.278, P < 0.05). Conclusions: The utilization of VMAT in the treatment planning of SABR for liver tumors under breath control mode has better dosimetrics. In comparison to conventional IMRT plans, VMAT plans have higher efficiency and feasibility. (authors)

[en] Highlights: • Construction noble-metal-free heterojunction. • highly stable and efficient photocatalytic hydrogen production under visible light irradiation. • The mechanism in hydrogen production was proposed. Using photocatalysts to produce hydrogen from photocatalytic water splitting is a green approach for producing renewable energy with minimum environmental impact. The key to the success of this technology is to develop an efficient hydrogen production catalyst with stable performance. In this work, we report a simple two-step preparation of zinc carbonate modified with Cd_0.5Zn_0.5S/Ni(HCO₃)₂ composite. The participation of Ni(HCO₃)₂ co-catalyst improved the visible light activity, which also irreversibly inhibited the recombination of holes and electrons. Meanwhile, the novel 0D and 2D heterojunctions are responsible for the excellent catalytic performance with superior stability. The catalytic hydrogen production reached the best rate of 64 mmol/g/h with the cumulative hydrogen production of 320 mmol/g in 5 h, which is even better than that from the photocatalysts activated with the precious metal, Pt. The underlying mechanism was rationalized by the hydrogen evolution kinetics analysis. The excellent hydrogen production performance, presented in this work, demonstrated that the composite of zinc carbonate modified with Cd_0.5Zn_0.5S/Ni(HCO₃)₂ is a promising, economical and efficient choice of the photocatalyst.

[en] Introducing oxygen vacancies is an effective way to promote photocatalytic performance of catalysts. Numerous explorations on metallic oxides and their composites were aimed at promoting visible light efficiency by narrowing bandgap and enhancing charge separations. In this work, we designed and synthesized the zinc oxide/graphitic carbon nitride (ZnO/g-C₃N₄) composites with diverse content of surface oxygen vacancies. We investigated the possible correlations between the surface defects and energy band structure using ultraviolet–visible (UV–vis) absorption spectra, Mott-Schottky plots and X-ray photoelectron spectroscopy. The results show that the surface oxygen vacancies in ZnO/g-C₃N₄ were responsible for the narrowing of the bandgap derived from the lower conduction band of ZnO. Composites of ZnO/g-C₃N₄ with more surface oxygen vacancies had significantly increased transient photocurrent with higher photocatalytic activity under visible light. The improved photocatalytic activity was demonstrated through photocatalytic organic degradation kinetics. Moreover, the introduction of surface oxygen vacancies in composite was originated from the formation of Zn-C bonds at heterojunctions between ZnO and g-C₃N₄.