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Background Although several systematic reviews and meta-analyses have been conducted to assess the relationship between fruit intake and health outcomes, the results of the relationship are inconclusive. Scope and approach We conducted an umbrella evaluation of existing research on the relationship between fruit intake and various health outcomes in humans. We used A Measurement Tool to Assess Systematic Reviews 2 and Grade of Recommendations, Assessment, Development and Evaluation to comprehensively evaluate the methodological quality and evidence quality of the research. We also performed a subgroup analysis based on the study design. Key findings and conclusions The umbrella review covered 59 qualified studies, which included 77 meta-analyses and 66 health outcomes. No adverse relationships between fruit intake and health outcomes were found. Moderate-quality evidence suggested that one serving increment of fruit per day could decrease the risks of cardiovascular disease (RR: 0.97, 95% CI: 0.95 to 0.99), stroke (RR: 0.92, 95% CI: 0.88 to 0.96), coronary heart disease (RR: 0.96, 95% CI: 0.93 to 0.99), and oral cancer (OR: 0.51, 95% CI: 0.40 to 0.65). And moderate-quality evidence presented that 200 g increment of fruit intake per day was associated with lower risk of breast cancer (RR: 0.94, 95% CI: 0.89 to 0.99), and the risk of type 2 diabetes mellitus could be reduced by 8%-12% when the fruit intake increasing to 100-500 g/d. For the remaining studies, the quality of evidence was either low or very low. We also found that the study design could influence the significance of the association between fruit intake and health outcomes. Large-sample, multi-center, and multi-country randomized controlled trials or prospective studies are required to verify our results.

With the development of new energy, hydrogen fuel engines have become a research boom in the automotive field. But there are abnormal problems such as backfire and pre-ignition during the combustion of hydrogen engines. This paper is based on the Ant Colony Optimization-Back Propagation (ACO-BP) algorithm to study the influence of different speed and load conditions on the ignition advance angle, so as to optimize the control of the hydrogen engine. The experimental system is established on a hydrogen engine converted from a 492Q gasoline engine. The prediction of the optimal ignition advance angle was obtained through experiments, and the optimal ignition MAP diagram of the hydrogen engine is constructed. The optimal ignition advance angle under different working conditions can effectively avoid the occurrence of hydrogen engine pre-ignition. The accuracy reaches 0.0018209 when the training reaches 14 times, the fitness between the actual value and the predicted value of ACO-BP training is 0.99921, the verification accuracy reaches 0.99913, and the test accuracy reaches 0.99932. Compared with the three optimization methods, the convergence speed and error accuracy of ACO-BP are significantly better than the BP neural networks and Genetic Algorithm-Back Propagation (GA-BP). This method realized the model of the nonlinear mapping model from hydrogen engine speed and load to optimal ignition advance angle, which is of great significance for solving the problem of abnormal combustion in hydrogen engine.

OBJECTIVE The study aimed to determine the safety and efficacy of intrathecally administered isoniazid (INH) and prednisolone in addition to systemic anti-TB therapy and compare it with systemic anti-TB therapy alone in adult patients with tuberculous meningitis (TBM). METHODS In this retrospective study, patients were categorized into two groups: Group A patients received systematic anti-TB therapy alone, Group B patients received IT INH (50 mg) and prednisolone (25 mg) twice a week together with the same standard systemic anti-TB therapy as Group A, in addition to the standard systemic anti-TB therapy. Functional outcomes were compared between the two groups in a prosperity-matched cohort using propensity score matching (PSM) method. RESULTS A total of 198 patients with TBM were enrolled. After PSM, 30 patients from each group were analyzed, so that there was no significant difference in the characteristics of the two groups. Mortality at follow-up was significantly lower among patients receiving additional IT therapy (4/30, 13.3%) compared with matched patients receiving systemic anti-TB therapy alone (11/30, 36.7%, P value = 0.037). CONCLUSIONS In this propensity score-matched cohort, the addition of IT INH and prednisolone to systemic anti-TB therapy could be effective for the better outcome among adult TBM patients. Further large-scale, prospective, and randomized controlled trials are warranted to the best timing and indication of IT therapy.

As a special phenomenon under transverse magnetic field (TMF) contacts, vacuum arc rotation deserves more attention. In this article, rotation characteristics of three typical TMF contacts, i.e., swastika-type, cup-shaped, and double-TMF contacts, are systematically studied. According to arc images, recorded by a high-speed camera, physical terms related to arc rotation such as rotation duration and rotation speed are clearly defined. The magnetic field and Lorentz force are calculated and the force balance of the moving arc is analyzed. On this basis, the effects of arc ignition mode, peak current, and contact type on arc rotation are investigated. Arc voltage noise as well as arc splashing outside caused by rotation is also discussed. The results show that the duration from ignition to rotation in two-point arc ignition (TPAI) mode is usually the shortest because of the rapidest constructed column formation. As the peak current increases, arc rotation becomes easier. Due to stronger TMF, the arc under double-TMF contacts has the longest rotation duration and the highest rotation speed.

The modeling and reconstruction of radar sea clutter (RSC) based on fractal theory is studied in this article. With theoretical derivation and quantitative analysis, the radar clutter reconstruction model based on singularity power spectrum (SPS) and instantaneous singularity exponent (ISE) distribution is proposed. The proposed ISE–SPS model consists of two coupling channels: power measure channel and dimension measure channel. The former is controlled by SPS to characterize the power distribution of signals in the SE domain, while the latter is determined by ISE function to characterize the statistical distribution of ISE. The multiscale wavelet coefficients are estimated based on the coupling of the two channels to reconstruct the RSC. The proposed ISE–SPS method is tested on RSC data in different sea state, from the ice multiparameter imaging X-band (IPIX) radar. Experimental and simulation based on the IPIX radar data set indicates that the proposed method performs better than the $N$ -partitioned random multiplicative model (NRMM) method and SPS-multifractal spectrum (MFS) method, and exceeds the traditional methods by nearly 35% in terms of correlation coefficient and normalized mean square error of MFS and SPS.

Background: Both acupoint injection and sacral canal injection are widely adopted in the treatment of lumbar disc herniation, but there are still doubts about the effectiveness and safety of the two methods. Therefore, the objective of the randomized controlled trial is to evaluate the effectiveness and safety of acupoint injection and sacral canal injection in the treatment of lumbar disc herniation. Method: This is a prospective randomized controlled trial to study the effectiveness and safety of acupoint injection and sacral canal injection in the treatment of lumbar disc herniation. With the approval by the clinical research ethics committee of our hospital, patients were randomly included into one of two treatment protocols: (A) acupoint injection group and (B) sacral canal injection group. Patients, doctors, nurses and research assistants responsible for collecting data were blinded to group allocation. Main outcome observation indicator: visual analogue scale; secondary outcome observation indicator: Oswestry Disability Index (ODI) scores; paresthesia score; adverse reactions. Data were analyzed using the statistical software package SPSS version 25.0 (Chicago, IL). Discussion: The effectiveness and safety of acupoint injection and sacral canal injection in the treatment of lumbar disc herniation were evaluated in this study, and the results of this trial would establish clinical evidence for the adoption of acupoint injection or sacral canal injection to treat lumbar disc herniation.

Solid oxide cells (SOCs) can switch between fuel cell and electrolysis cell modes, which alleviate environmental and energy problems. In this study, the La0.3Sr0.7Fe0.9Ti0.1O3-δ (LSFTi 91) perovskite is innovatively used as a symmetric electrode for solid oxide electrolysis cells (SOECs) and solid oxide fuel cells (SOFCs). LSFTi 91 exhibits a pure perovskite phase in both oxidizing and reducing atmospheres, and the maximum conductivity in air and 5% H2/Ar is 150 and 1.1 S cm-1, respectively, which meets the requirement of the symmetric electrode. The polarization resistance (Rp) at 1.5 V is as low as 0.09 Ω cm2 in the SOEC mode due to the excellent CO2 adsorption capacity. The current density can reach 1.9 A cm-2 at 1.5 V and 800 °C, which is the highest electrolytic performance in the reported single-phase electrodes. LSFTi 91 also exhibits eminent oxygen reduction reaction and hydrogen oxidation reaction (ORR and HOR) activities, with Rp of 0.022 and 0.15 Ω cm2 in air and wet H2, respectively. The peak power density of SOFC could reach 847 mW cm-2 at 800 °C. In addition, good reversibility is confirmed in the cyclic operation of SOFC and SOEC.

We demonstrate a distributed feedback (DFB) semiconductor laser based on i-line lithography and surface periodic current injection technologies with a lasing wavelength of 795 nm, which corresponds to the D1 spectrum of Rb and has many applications with respect to alkali vapor lasers and atomic clocks. The maximum output power, side mode suppression ratio (SMSR), and single-longitudinal-mode tunable range of our device are 50.89 mW (at 20 °C), 34.56 dB, and 12.792 nm, respectively. The rate of change in wavelength with temperature of the laser is 0.401 nm/°C, which is equivalent to that of a Fabry-Perot (FP) laser and much better than that of a general DFB device. This device has a cavity the same as an FP laser without any etching gratings, meanwhile the lasing spectrum behaves a single longitudinal mode characteristic as a DFB laser.

For radio telescope array applications, the precise time and frequency reference predominantly determines the quality of the observation. In this paper, we demonstrate an integrated dissemination system which can achieve ultra-stable frequency dissemination, time synchronization and data transfer simultaneously over a single optical fiber link. The test of this integrated system was carried out on the 48-km fiber link, which consisted of 28-km buried fibers, and 20-km fiber spool in laboratory. It has been experimentally demonstrated that the frequency transfer stability is $2.6 \times {10^{ - 14}}/s$ and $3.0 \times {10^{ - 16}}/{10^4}s$. The time synchronization with 100-ps accuracy and the error bit ratio of data transfer at the level of 10-8 are also demonstrated.

Developing a simple method to qualitatively and quantitatively assess food quality is essential. Available methods primarily rely on nanotechnology and offer high selectivity and sensitivity. In this study, we aimed to develop a sensitive nano-probe, and to this end, a double-stranded DNA-encased HiPco carbon nanotube (dsDNA-HiPco) hybrid was prepared and used to evaluate the antioxidant potential of Chinese tea against H2O2, using a range of irradiation wavelengths. The morphology and dispersion of dsDNA-HiPco hybrids were analysed using atomic force microscopy, which showed a homogeneous dispersion of the rod-shaped tubes. The antioxidant effect of the hybrid was evaluated by near-infrared absorption and photoluminescence. The experimental results revealed that the tea exerted excellent antioxidant effects when the dsDNA-HiPco hybrid was pre-treated with 0.03 wt.% H2O2. Catechin contained in the Chinese tea played a pivotal role in exerting the antioxidant effect. Therefore, the simple detection method proposed herein can be successfully applied in various fields, including biology, medicine, and the food industry.

Solid oxide electrolysis cells (SOECs) are a new type of high-efficiency energy conversion device that can electrolyze CO2 efficiently and convert electricity into chemical energy. However, the lack of efficient and stable cathodes hinders the practical application of CO2 electrolysis in SOECs. Herein, a novel perovskite oxide La0.5Sr0.5Fe0.95Mo0.05O3−δ (LSFMo) is synthesized and used as a cathode for SOECs. The introduction of Mo significantly improves the CO2 tolerance of the material in a reducing atmosphere and solves the problem of SrCO3 generation in the La0.5Sr0.5FeO3−δ material. Mo ion doping promotes the conductivity in a reducing atmosphere and increases the oxygen deficiencies of the material, which lowers the ohmic resistance (Rs) of the material and significantly improves the CO2 adsorption and dissociation in the middle-frequency of polarization resistance (Rp). For example, Rp decreases from 0.49 to 0.24 Ω cm2 at 800 °C under 1.2 V. Further, the reduction of Rs and Rp increases the performance improvement, and the current density is increased from 1.56 to 2.13 A cm−2 at 800 °C under 2 V. Furthermore, LSFMo shows reasonable short-term stability during the 60 h stability test.

The specific heat of aqueous graphene+Al2O3 (1:1) hybrid nanofluid was measured using the cooling method. The influence of nanoparticle mass fraction and temperature on the specific heat capacity of the hybrid nanofluids was investigated, the specific heat of the hybrid nanofluid was compared with that of aqueous graphene oxide nanofluid and Al2O3 nanofluid. A fitted formula of the specific heat of the hybrid nanofluid was proposed based on the experimental data. It indicates that the specific heat reduction ratio increases with increase of nanoparticle fraction and the maximum reduction ratio is 7% at 0.15 wt.% at 20?C. The mass fraction of nanoparticle affects the specific heat of hybrid nanofluid more significantly at lower temperature. Temperature impacts the specific heat more distinctly than the nanoparticle fraction. The specific heat increases with temperature and the maximum specific heat reduction ratio of the hybrid nanofluid diminishes from 7% at 20?C to 2% at 70?C at the mass fraction of 0.05%.

Semiconductor optical amplifiers (SOAs) offer direct electrical injection, power consumption, integration, and anti-radiation advantages over optical fiber amplifiers. However, saturation output power and gain bandwidth have been limited in traditional structure SOAs. We demonstrate a monolithic integrated SOA with broad spectrum, high power, high gain, and small spectral linewidth expansion. The device adopts a two-stage amplified large optical cavity structure, and a lower optical field confinement factor is obtained by adjusting the thickness of the waveguide layer. The lower optical field confinement factor is conducive to improving the coupling efficiency and the maximum output power. Our device, fabricated only by standard i-line lithography with micron-scale precision, obtains excellent and stable performance. When the input power is set to 1 mW, the output power is 419 mW with a gain of 26.23 dB. When the input power is set to 25 mW at 25 °C, the output power increases to 600 mW with a gain of 13.8 dB. The corresponding gain bandwidth of 3 dB measures at least 70 nm. The spectral linewidth after the SOA is 1.15 times wider than that of the seed laser.

In this article, the model including cathode spot process and deuterium desorption process on zirconium deuterium cathode is developed. Five kinds of particle fluxes on cathode surface and three mechanisms affecting deuterium diffusion in cathode are considered. The model not only describes the deformation of cathode metal, but also describes the variation of deuterium concentration with time. On pure zirconium cathode, the mean charge state is larger but on zirconium deuterium cathode, the total ion number density is larger since there are additional deuterium ions, and simulation results show the discharge currents are very close on the two cathodes, the energy flux density on ZrD0.66 cathode is larger so cathode spot crater develops faster on ZrD0.66 cathode. Ablation rates caused by different mechanisms are calculated and the results show in cathode spot development process, mass loss caused by evaporation is ignored, most of the liquid metal will resolidify on cathode surface, and droplets are the main reason for cathode ablation. The ablation rates due to the ejection of droplets are close to experimental results. The ratios of deuterium ion from different mechanisms in this process are also calculated and it is 93.5% in simulation. Simulation results are in agreement with the other researchers’ works.

Tailings from the vanadium extraction process are discarded each year as waste, which contain approximately 30wt% of Fe. In our previous work, we extracted Fe and Mn from vanadium slag, and Fe and Mn existed in the form of FeCl2 and MnCl2 after chlorination by NH4Cl to achieve effective and green usage of waste containing Fe and Mn. In this work, square wave voltammetry (SWV) and cyclic voltammetry (CV) were applied to investigate the electrochemical behaviors of Fe2+ and Mn2+ in NaCl-KCl melt at 800°C. The reduction processes of Fe2+ and Mn2+ were found to involve one step. The diffusion coefficients of FeCl2 and MnCl2 in molten salt of eutectic mixtures NaCl-KCl molten salt were measured. The electrodeposition of Fe and Mn were performed using two electrodes at a constant cell voltage. The Mn/Fe mass ratio of the electrodeposited product in NaCl-KCl-2.13wt%FeCl2-1.07wt%MnCl2 was 0.0625 at 2.3 V. After the electrolysis of NaCl-KCl-2.13wt%FeCl2-1.07wt%MnCl2 melted at 2.3 V, the electrolysis was again started under 3.0 V and the Mn/Fe mass ratio of the electrodeposited product was 36.4. This process provides a novel method to effectively separate Fe and Mn from simulated chlorinated vanadium slag.

Vertical-cavity surface-emitting lasers that can be controlled to emit hollow laser beam in certain LP21 mode are proposed and fabricated. A circular inverted surface relief with precisely designed diameter and thickness is introduced through theoretical simulation. The fabricated device shows a stable single LP21 mode operation with excellent robustness of mode and power to temperature. Preliminary analysis attribute the excellent performance of the device to the inverted surface relief, leading to hollow near-field spot distribution.

In this paper, we present a detailed investigation of three types of tapered distributed feedback (DFB) quantum cascade lasers (QCLs) emitting at $7.2~\mu \text{m}$ . The sampling gratings with different sampling duty cycles were fabricated by holographic lithography combined with the conventional optical photolithography. High output power of more than 550mW with excellent beam quality was achieved in continuous-wave operation at 293K for a 2.5-mm-long DFB-QCL with sampling duty cycles of 0.25 and 0.5 in the tapered region and uniform region, respectively. Stable single-mode emission with a side-mode suppression ratio above 25dB was obtained in the temperature range of 283-318K. The demonstrated tapered DFB QCL structure with asymmetric coupling coefficient can effectively achieve high performance with low fabrication cost, which is beneficial for many applications.

The effects of parboiling processing (121 °C for 10, 15, and 20 min, 0.1 MPa) on thermal properties, color value, morphological properties, and crystallinity of highland barley were studied. During 20 min parboiling processing, the color values Chroma B*, b* values increased, and L* values decreased; the crystallinity of parboiled barley illustrated A, B, and V-style polymorphs; the heat enthalpy (ΔH) and onset, peak, conclusion temperature of gelatinization, and range of gelatinization (To, Tp, Tc, and Tc-To) was decreased; the internal structure of highland barley was destroyed. Meanwhile, the crystallinity was observed to be significantly correlated to color values and thermal properties during different degrees of processing.

Aim To evaluate the intraocular pressure (IOP)-lowering efficacy and safety of tafluprost 0.0015% eye drops [benzalkonium chloride (BAK) 0.1 mg/mL] compared with that of latanoprost 0.005% eye drops (BAK 0.2 mg/mL) for primary open angle glaucoma (POAG) and ocular hypertension (OHT). Methods All the randomized controlled trials (RCTs) about treating POAG and OHT comparing tafluprost and latanoprost were collected by searching PubMed, Embase, Cochrane Library, CNKI and VIP. The outcomes of interest to evaluate the clinical efficacy and adverse effects included IOP and patient-related drop discomfort. Results Five RCTs involving 888 glaucoma patients were included. The results showed that, 1) at the end of the study, no statistically significant differences were observed in IOP reduction [standard mean difference (SMD) =0.48, 95%CI 0.07 to 0.88, P=0.085] between tafluprost and latanoprost; 2) No statistically significant differences were observed in adverse events of foreign-body sensation [relative risk (RR) =0.62, 95%CI 0.26 to 1.46, P=0.269], eye irritation (RR=1.16, 95%CI 0.49 to 2.75, P=0.744), eye pain (RR=2.000, 95%CI 0.949 to 4.216, P=0.07), iris hyper-pigmentation (RR=0.741, 95%CI 0.235 to 2.334, P=0.61), dry eye (RR=1.154, 95%CI 0.409 to 3.256, P=0.79) and eye pruritus (RR=1.600, 95%CI 0.536 to 4.774, P=0.4) between tafluprost and latanoprost. However, tafluprost showed more reported incidence of conjunctival hyperaemia than latanoprost (RR=2.11, 95%CI 1.24 to 3.59, P=0.006). Conclusion Tafluprost 0.0015% eye drops (BAK 0.1 mg/mL) and latanoprost 0.005% eye drops (BAK 0.2 mg/mL) are comparable in lowering IOP for open angle glaucoma (OAG) and OHT. It does not differ in the incidence of foreign-body sensation, eye irritation, eye pain, iris hyper-pigmentation, dry eye and eye pruritus, but tafluprost shows less ocular tolerability because of more incidence of conjunctival hyperaemia.

Amelotin (AMTN) as a matrix protein exerts a direct effect on biomineralization by modulating apatite (HAP) formation during the dental enamel maturation stage through the specific interaction of a potentially phosphorylated Ser-Ser-Glu-Glu-Leu (SSEEL) peptide fragment with calcium phosphate (Ca-P) surfaces. However, the roles of (non)phosphorylation of this evolutionarily conserved subdomain within AMTN remain poorly understood. Here, we show, by time-resolved atomic force microscopy (AFM) imaging of in situ HAP crystallization via the HPO42--rich amorphous calcium phosphate (acidic ACP), the on/off switching of the phase transformation process through a nonphosphorylation-to-phosphorylation transition of the SSEEL motif. Using high-resolution transmission electron microscopy (HRTEM), we observed that the acidic ACP phase is stabilized by the phosphorylated SSEEL motif, delaying its transformation to HAP, whereas the nonphosphorylated counterpart promotes HAP formation by accelerating the dissolution-recrystallization of the acidic ACP substrate. Dynamic force spectroscopy measurements demonstrate greater binding energies of nonphosphorylated SSEEL to the acidic ACP substrate by the formation of molecular peptide-ACP bonding, explaining the enhanced dissolution of the acidic ACP substrate by stronger complexion with surface Ca2+ ions. Our findings demonstrate direct evidence for the switching role of (non)phosphorylation of an evolutionarily conserved subdomain within AMTN in controlling the phase transition of growing enamel and designing tissue regeneration biomaterials.

The substitution of elements has attracted great interest to enhance the electrochemical properties of sodium-ion batteries (SIBs). Herein, the P2–Na0.67Co0.35Ti0.20Mn0.45–xLaxO2 electrode samples were prepared via a solid-state route. The effect of La3+ substitution was researched as high-rate SIBs cathode. The Na0.67Co0.35Ti0.20Mn0.44La0.01O2 exhibits a superior initial specific capacity of 162.7 and 125.9 mA·h/g after 50 cycles at 0.1C rate, and the initial specific discharge capacity of 115.2 mA·h/g with 60.6% capacity retention after 100 cycles at 1C. In addition, the Na0.67Co0.35Ti0.20Mn0.44La0.01O2 sample shows an excellent rate capacity of 91.9 and 60.4 mA·h/g with 46.9% and 50.9% capacity retentions even at 8C and 10C rate after 100 cycles, respectively. The promising La-substituted P2-type Na0.67Co0.35Ti0.20Mn0.45–xLaxO2 material provides a new strategy for designing high-rate performance of SIBs.

Co-free La0.6Sr0.4FeO3-δ (LSFNb0) and La0.6Sr0.4Fe0.9Nb0.1O3-δ (LSFNb0.1) perovskite oxides were prepared by a standard solid-state reaction method. The structural stability and electrochemical performance of La0.6Sr0.4Fe0.9Nb0.1O3-δ as both cathode and anode were studied. Nb dopant in LSFNb0 significantly enhances the structural and chemical stability in anode condition. At 800 °C, the polarization resistances (Rp) of LSFNb0.1 symmetric electrode based on YSZ electrolyte are 0.5 and 0.05 Ω cm2 in H2 and air, respectively. The peak power densities of LSFNb0.1 based on LSGM electrolyte-supported SSOFCs are 934 and 707 mW cm−2 at 850 °C in H2 (3% H2O) and dry CO, respectively. Moreover, the symmetric cell exhibits reasonable stability in both H2 and CO fuel, suggesting that La0.6Sr0.4Fe0.9Nb0.1O3-δ may be a potential symmetric electrode material for hydrogen and carbon monoxide SOFCs.

We demonstrate InP-based buried grating coupled surface-emitting distributed feedback (DFB) lasers designed to operate at a wavelength of 2004 nm. The laser structure consists of three InGaAsSb/InGaAs QWs, with a 5 $\mu \text{m}$ wide double-channel ridge waveguide. A second-order semiconductor/semiconductor grating is used for in-plane feedback and vertical out-coupling. The single longitudinal mode emission wavelength of the fabricated laser can be adjusted from 2002.7 to 2006 nm without any mode hopping. High side-mode suppression ratio (SMSR) of at least 35 dB is achieved under all injection currents and temperature conditions. The edge output power reaches 19 mW, measured in continuous-wave (CW) mode at 10 °C. Simultaneously, the output power of surface emission reaches 8 mW.

High power semiconductor disk lasers (SDLs) with near-diffraction limited beam quality were demonstrated. The influence of the incident angle, operation temperature, cavity length and curvature radius of the output coupler mirror on the beam quality were investigated. The condition for near-diffraction limited beam quality was analyzed. Choosing the pump spot size 10%–20% smaller than the fundamental mode size is the roughly optimized condition for achieving near-diffraction limited beam quality in SDLs. Finally, the SDL with an output power of 12.9 W and M2

Vanadium slag contains several critical elements like V, Ti, Cr, Fe and Mn. In our previous work, V and Cr have been enriched by selective chlorination, increasing from 10.05% to 14.95% and 5.84%–8.69% separately. V and Cr still maintain the trivalence state in molten salt. In the current work, the electrodeposition behaviors of V3+ and Cr3+ in NaCl–KCl molten salt at 800 °C were investigated using cyclic voltammetry (CV) and square wave voltammetry (SWV) with a tungsten electrode. It was found that the reduction processes of V3+ and Cr3+ consist of two steps, M3+/M2+, M2+/M. The diffusion coefficients of V3+ and Cr3+ in NaCl–KCl molten salt were measured by CV. The effect of VCl3/CrCl3 mass ratio on VCr alloy was investigated by a two-electrode under constant voltage. Pure Cr can be obtained at 2.8 V in the NaCl–KCl molten salt, while VCr alloy (3.71 mass % V-94.28 mass% Cr-2.01 mass % O) was obtained when electrolysis voltage was controlled to 2.8 V at 800 °C. The composition of VCr alloy can be designed by changing the molten salt composition. This method can be applied for direct preparation of VCr alloy from vanadium slag, thus offering the use of low cost raw materials with direct environmental benefits.

A dual-wavelength quantum cascade laser (QCL) with two shallow-etched distributed Bragg reflectors is designed and fabricated. Based on a heterogeneous active region within a single waveguide, single-mode emission at 7.6μm and 8.2μm was achieved. The two wavelengths can be independently controlled by selective current injection on different regions of the device, which are electrically isolated. High optical powers of about 275mW and 218mW at room temperature were obtained for the single-mode emission at 7.6μm and 8.2μm, respectively. The presented design concept for high power, dual-wavelength switchable, mid-infrared QCLs is significant in developing miniaturized multi-species gas detection systems.

Terahertz nondestructive testing technology is a technology widely used in samples evaluation with the merit of on-site and surface-damage free. Terahertz waves have low quantum energy and are transparent to most non-polar substances, thus, terahertz nondestructive testing has gradually become a research hotspot over the years. However when a femtosecond laser in used as a terahertz excitation source, the excess pump light in the system may cause radiation damage to the measured object. In order to eliminate the impact of residual pump light in the system on the measured object, we designed the spectral filter elements of reflect and terahertz band transmission in the wave bands of 0.80 μm and 1.56 μm, by using Nb2O5 and SiO2 as high and low refractive index materials, respectively. Then we prepared the filter membrane system electron beam evaporation through an ion beam assisted deposition. The influence of annealing process on the growth structure of the films was analyzed according to the AFM test results of Nb2O5 monolayer films under different process conditions, and the annealing process parameters were optimized to reduce the influence of surface roughness on the film spectrum. Based on the KIM vibration model (Lorentz extension model), the optical constant dispersion distributions of NB2O5 thin flims prepared under different processing conditions were accurately fitted. The influence of temperature on the refractive index and absorption of Nb2O5 thin films were analyzed. The deposition temperature was optimized to reduce the absorption of the filter in the wave bands of 0.8 μm and 1.560 μm. By using PE Lambda 1050, the reflectivity of the prepared filter in the wave bands of 0.8 μm and 1.560 μm were tested. The prepared filter was scanned by focusing point by point using a built-up transmission terahertz time domain spectral system. The transmittance of the quartz coated sample relative to the reference signal was calculated by analyzing signals in the frequency domain. The average reflectivity of the prepared spectral filter was 99.9% in both the band of 0.9 μm and 1.560 μm. The transmittance of terahertz frequency 2 THz was 68%, which was almost consistent with the theoretical design values, and could meet the requirements for the terahertz nondestructive testing system's application.

Er 3+-doped fluoroaluminate glasses with different concentrations were prepared by using melt-quenching method. Under a 638 nm laser diode pumping, efficient 3.5 μm emission was observed in the 18 mol% Er 3+ doped sample, which was ascribed to the Er 3+: 4F 9/2 → 4I 9/2 transition. The fluorescence properties such as radiative transition probability, energy level lifetime and branch ratio were predicted by the well-known Judd-Ofelt theory, while the emission and absorption cross-sections were calculated using the Füchtbauer-Ladenburg and McCumber theories, respectively. Both simulated and experimental results show that Er 3+-doped fluoroaluminate material is a promising gain medium for 3.5 μm laser applications.

This work investigates the transient arc behavior during the anode spot mode with CuCr25 electrodes theoretically and experimentally. In the simulation, a 2D transient magneto-hydro-dynamic (MHD) model considering multi-component plasma is used to calculate the arc parameters. Then, the energy flux is obtained to calculate the anode temperature in next time step. Simulation results show that when the anode temperature is high enough, the anode vapor density increases significantly. Therefore, ions from the cathode are decelerated by the anode vapor when arriving at the ionization layer, leading to changes in the ion temperature. Then, the arc current is more likely to flow to the edge of the atom vapor area instead of the anode center. Thus, the energy flux to the anode begins to heat the area around the anode spot, leading to a more uniform anode temperature distribution and a larger anode spot. The maximum anode temperature occurs after the peak current due to the thermal inertia. Experiments using optical methods for anode temperature determination are also conducted to verify the simulation results.

In this work, the plasma initiation and development in the vacuum gap with CuCr50 cathode are investigated with a two-dimensional particle-in-cell/Monte Carlo collisional model, in which the distributions of electric field and charged particles are calculated by the Poisson’s equation and Newton’s law in the two-dimensional cylindrical coordinate respectively. Particles including electrons, neutrals and various copper ions and chromium ions are traced as super particles, and collisions between these particles are processed with Monte Carlo collisional method. Results show that the plasma quickly forms near the cathode and propagates towards the anode in a hemi-spherical shape with the external voltage applied. The space charge in the discharge features three different layers in the calculation region and results distortion in the potential distribution, which counts for the high ion velocity. Compared with the discharge in vacuum gap with pure copper cathode in the previous work, the plasma initiates and propagates faster, the neutral and plasma density are higher, the distortion of electron potential is more significant and the charged particle velocities are larger with CuCr cathode in this work.

In a superconducting Tokamak, superconducting coils play crucial roles in generating desired magnetic field profile and confining high-temperature plasma. When quench occurs inside superconducting magnet, tremendous energy stored in the coil has to be dissipated in time before any damage to the magnet caused by heat or electric stress. In this paper, a quench protection switch (QPS) based on forced current zero is investigated experimentally. The first current commutation process from the bypass switch (BPS) to the main circuit breaker (MCB) is presented. The second current commutation process from the MCB to the discharging resistor is mainly studied. In this stage, experimental current in the MCB, which uses vacuum interrupter (VI), is forced to zero by a high-frequency countercurrent, which is a typical approach of DC interruption. The interruption performance and influence of contacts structure, countercurrent frequency and contacts stroke are discussed. The evolution of vacuum arc in this process is investigated as well.

We report a terahertz quantum cascade laser frequency comb (THz QCL FC) with low threshold current density, high power, and wide current dynamic range. The active region design with the semi-insulated surface plasma waveguide is beneficial to optimize the gain dispersion value and temperature stability. At 10K, the comb with 3-mm-long and 150-µm-wide is capable of emitting 22mW with the threshold current density Jth = 64.4 A·cm−2. The total spectral emission is of about 300 GHz centered around 4.6 THz. Without any extra dispersion compensation measures, the intermode beatnote map reveals stable frequency comb operating within a current dynamic range more than 97% and the narrowest beatnote linewidth is 7.2 kHz. The stable FC operation of a free-running THz QCL makes our device an ideal source for further development of dual-comb spectroscopy.

As a compact light source with high output power, quantum cascade laser has excellent performance in the range of 1-5THz. By using THz QCL optical comb spectrum in this frequency range, drugs and industrial waste gas can be quickly and effectively detected and identified. In this paper, we report a semi-insulating surface-plasmon waveguide THz QCL emitting at 5 THz operating in continuous-wave mode at 4K. For the device with 3-mm-long cavity and 150-µm-wide ridge, the continuous peak power is up to 13mW and the total spectral range is about 5cm-1. Furthermore, the stable optical comb is achieved in the range of 0.93-1.11A.

The nanosecond-level pulse-operation characteristics of photonic-crystal surface-emitting lasers (PCSELs) with ultralow divergence were investigated in detail. We demonstrate a maximum peak output power of 14 W for a current pulse width of 9 ns, which is about 28 times the saturated power under continuous wave (CW) operation. The full width at half maximum (FWHM) of the optical response pulse is about 3 ns wider than the current pulse. The maximum repetition frequency reaches 400 kHz at 10 A without significant degradation of output power while the value is 100 kHz at 40 A. Moreover, the multimode behavior of the PCSEL at a high peak current was analyzed.

In this paper, we report a spectral beam combining technique based on discrete quantum cascade lasers at l~ 4.8 mm. Good beam qualities of M 2 < 1.3 for both fast and slow axes are obtained. The entire spectrum span is approximately 29.1 cm -1 , which is consistent with the theoretical results of grating equation. Maximum beam combining efficiency of 58.9% with output power exceeding 1 W is demonstrated under continuous wave operation at room temperature. The limit of beam combining efficiency is theoretically investigated. The independent temperature control for the discrete lasers circumvented the issue of thermal crosstalk between the lasers on an array and pave the way to high power and high efficiency laser spectral beam combining.

The advancement in analytical imaging techniques, including atomic force microscopy (AFM) and scanning and transmission electron microscopies (SEM and TEM), has allowed us to observe processes occurring at mineral surfaces in situ at a nanoscale in real space and time and hence giving the possibility to elucidate reaction mechanisms. Classical crystal growth theories have been established for well over 100 years and while they can still be applied to explain crystal growth in many growth scenarios, we now know that these models are not always an accurate description of the mechanism of all crystal/mineral growth processes, especially where nanoparticle formation is observed. Consequently there is a current challenge at the forefront of understanding crystal/mineral growth mechanisms. This work describes experimental observations of non-classical crystallization processes at the nanoscale. Using AFM as well as SEM and TEM imaging, we demonstrate that many minerals commonly grow by the attachment of nanoparticles on an existing mineral surface, often resulting from the coupling of dissolution of a parent phase and the precipitation of a new product mineral. Through varied examples of crystal/mineral growth, including calcite and other carbonates, barite, brucite, and apatite, we define the importance of the mineral-fluid interface and the aqueous fluid interfacial (boundary) layer in the control of crystal growth. Whether a crystal will grow by classical monomer attachment resulting in step advancement or by the formation, aggregation and merging of nanoparticles, will be controlled by the aqueous fluid composition at the mineral-fluid interface. The processes described also allow for the development of porosity within the new mineral and hence have important consequences for fluid movement and element mobility within the Earth. Additionally an understanding of natural mineral growth has implications for geomimetic applications for the manufacture of functional engineered materials.

Modeling and numerical simulation is an important tool for the research of the physical mechanisms of the vacuum arc (VA). Compared with the experiments of the VA, numerical simulation is more efficient and economical. Axial magnetic fields (AMFs) are also the most popular control technology in vacuum interrupters and other application fields. First, the model of VA was reviewed from a relatively simple zero-order one to 2-D one, and then a 3-D one, which gives us a more comprehensive understanding of VA. Second, the influence of spatial distribution of magnetic fields on VA behavior is also studied. VA behavior under different commercial AMF contacts was simulated and compared based on 3-D magnetohydro-dynamic model. Influence of the radial slots and magnetic field generated by adjacent phase and bus bar on arc characteristics has been reviewed. Third, the VA modeling with active anode is reviewed and discussed. Anode vapor can cool arc plasma, and leads to changed distribution of current density and plasma parameters. Model and simulation technology of anode activity have also been reviewed in this paper, from 1-D, 2-D, to 3-D, and then the deformation of anode melting pool is considered. Deformation of anode melting pool will make anode temperature more reasonable. Finally, the challenge and research direction of VA modeling is also given and discussed.

The Robson drift phenomenon is a macroscopic reflection of the movement of a cathode spot (CS) in oblique magnetic field (OMF). Although it was discovered many years ago, its physical mechanism remains unclear. In this paper, the influence of OMF on the Robson drift of CS motion is simulated. A 2-D stepwise model of the movement of a single CS in OMF is established. It is assumed that the probability of generating a new spot in directions of Amperian force, anti-Amperian force, and directions perpendicular to Amperian force, is proportional to the magnetic pressure around the old spot. The drift angle and velocity of the CS in OMF are simulated. The simulation results show that the drift angle of the CS in OMF has liner relationship with the inclination angle of magnetic field, and it has no obvious relationship with the strength of the applied magnetic field and the amplitude of the arc current, which are in a good agreement with the experimental results. Besides, under the same angle of magnetic field, the velocity of spot motion increases linearly with the strength of OMF. Moreover, the simulation results show that the transverse magnetic field component has a much more predominant influence on the CS velocity than the axial magnetic field component, which are also in agreement with the experimental results.

A quench protection switch (QPS) is indispensable to protect the magnet coils from the damage of quench in a superconducting Tokamak. In this paper, a QPS based on artificial current zero is involved. The vacuum circuit breaker (VCB), which is driven by a high-speed electromagnetic repulsion mechanism, is used as the main circuit breaker (MCB). Two kinds of commercial vacuum interrupters (VIs), which have contacts generating axial magnetic field (AMF) and transverse magnetic field (TMF), respectively, are applied. The breaking current with an amplitude of 10~25 kA is generated by an LC oscillating circuit. The countercurrent with frequency in the range of 500–3000 Hz is provided by a commutation branch. The interruption performance of the two kinds of VIs under different breaking current and countercurrent frequencies is investigated. The experimental results indicate that the differences in interruption performance under the two types of contacts are increasing with larger frequencies of countercurrents.

In order to obtain narrow linewidth semiconductor laser around 1564 nm, we design a distributed Bragg reflector (DBR) laser with high-order Bragg gratings (HOBGs) using butterfly encapsulation. The DBR laser is fabricated only by i-line lithography technology with grating period of 4. 84 μ m , groove width of 1. 5 μ m and grating length of 72 μ m on a strip width of 4 μ m . The 1mm-long devices achieved an output power of 9.9 mW and a side mode suppression ratio (SMSR) more than 30 dB without facet coating at an injection current of 80 mA. The lasers showed ultra-narrow Lorentz linewidth of 70 kHz. This paper provides a simple method for large-scale production of narrow linewidth semiconductor lasers.

P2-type Na2/3Co0.25Mn0.705Si0.045O2 (Si-NCM) high-rate cathode was designed by using silicon of the nonmetallic element as dopant and developed by the simple solid-state route for sodium-ion batteries. XRD refinements confirm the P2-type hexagonal structure with space group (SG: P63/mmc), in which Si4+ ions substitute the Mn site of P2-Na2/3Co0.25Mn0.75O2 (NCM) lattice without any impurity phases of Si-related substances. Si-NCM delivers the initial capacity of 144 mAh g−1 at 0.1 C with the capacity retention of 80.1% after 100 cycles, and the discharge capacity of 120 mAh g−1 at 1 C with 83.4% retention at 200th cycle. Particularly, excellent capacity retentions of 90.2% after 260 cycles and 85.8% after 500 cycles at 5 C have been achieved. Si-doping can expedite the superior cycle stability of Si-NCM compared to NCM, which is attributed to the more powerful Si–O, TM–O and O–O bonds, more stable occupancy rate in the Nae site of unit cell and particularly ascribed to the reversible two-phase transition of P2–P3–P2 in the process of Na+ extraction and intercalation. Hence, SiO2 as dopant is a novel strategy with regard to the development of high-rate cathode materials for SIBs.

In this paper, we demonstrate a regrowth-free double-tapered gain-coupled distributed feedback semiconductor laser. It is designed based on periodic surface current injection to reach a high-power and single-longitudinal mode. A continuous-wave output power of over 1.2 W/facet is achieved at 4 A. High single-longitudinal-mode output power reaches up to 0.9 W/facet at 3 A at each uncoated facet. The side mode suppression ratio is nearly 30 dB at 980 nm. The 3 dB spectral width is less than 2.7 pm. The lateral far field divergence angle is only 14.5°, the beam quality factor M2 is 1.7, achieving a near-diffraction-limit emission. Our device, produced by standard i-line lithography, enhances the output power while obtaining the pleasurable spectral and spatial properties. It has great potential in widespread commercial applications such as high efficiency pumping sources for its low-cost, easy fabrication technique and excellent performance.

A narrow-strip single-longitudinal-mode gain-coupled distributed feedback semiconductor laser with a central wavelength of approximately 670 nm is demonstrated. We fabricate a novel micro-scale regrowth-free gain-coupled grating with an island-like shape without nanoscale gratings by i-line lithography only. The maximum output power from the fiber of the device with butterfly package is 48.1 mW at 100 mA and its slope efficiency is 0.79 W/A. The laser can be continuously tuned from 670.750 to 670.784 nm with a side-mode suppression ratio of over 40 dB, covering the absorptive peak of lithium atoms. Our easily fabricated devices have great potential as light sources in many applications such as lithium atom detectors.

P2-Na0.67Co0.25Mn0.75-xNbxO2 (x = 0, 0.015, 0.030, 0.045) cathode materials were obtained by a simple solid-state method. The Nb5+-doped effects on ameliorating the structural and electrochemical properties of the Na0.67Co0.25Mn0.75O2 parent material for sodium-ion batteries have been investigated. XRD measurements confirm a hexagonal main phase (P63/mmc) and some trace of orthorhombic NaNbO3 (P21ma). Rietveld refinements exhibit the higher lattice parameters and the bigger c/a values due to Nb5+ doping into the parent Na0.67Co0.25Mn0.75O2. The optimized 3.0 at.% Nb5+-doped P2-Na0.67Co0.25Mn0.75O2 sample delivers the initial discharge capacity of 126.7 mAh g−1 at 0.1 C in the voltage range of 1.8–4.0 V, and its capacity retention is 75.3% after 100 cycles, which is 63.7% higher than that of the pristine. Whereas at 10 C rate, the optimized sample presents the maximal discharge capacity of 72.8 mAh g−1 with an excellent high-rate cycling stability of 91.6% retention after 100 cycles, correspondingly the pristine shows 61.4 mAh g−1 and 73.1% retention. These excellent electrochemical performances are ascribed to better structural stability, and lower charge transfer resistance and higher Na+ diffusion coefficient after Nb5+ doping. Therefore, the Nb5+-doped P2-type cathode materials can be deemed as a beneficial improvement for researches on sodium-ion batteries.

High-power, low-threshold stable single-mode operation buried distributed feedback quantum cascade laser by incorporating sampled grating emitting at λ ~ 4.87 μm is demonstrated. The high continuous wave (CW) output power of 948 mW and 649 mW for a 6-mm and 4-mm cavity length is obtained at 20 °C, respectively, which benefits from the optimized optical field distribution of sampled grating. The single-mode yields of the devices are obviously enhanced by controlling cleaved positions of the two end facets precisely. As a result, stable single-mode emission and mode tuning linearly without any mode hopping of devices are obtained under the different heat sink temperatures or high injection currents.

A novel thermal-optical phase modulation structure based on polymer/silica hybrid waveguide is proposed. Patterned graphene strip is introduced as electric nanoheater in the structure. Finite element method simulation is performed on both thermal and optical field analysis. Results show that response speed is improved by a factor of three and power consumption is reduced by half, in comparison with conventional state-of-art polymer-based phase shifter. This proposed structure is compatible with current complementary metal-oxide-semiconductor power supply standard and has very large design robustness. It shows great application potential on low-power optical switch, modulator and polymer thermal-optical phase arrays.

High power semiconductor disk lasers (SDLs) were demonstrated based on the thermal management using pre-metalized diamond heat-spreader. The processing of pre-metallization using Cu-Sn alloy was developed. The resultant and influence of pre-metallization on the thermal performance of SDLs were investigated. It was found that the pre-metalized diamond heat-spreader was able to improve effectively not only the thermal resistance but also the bonding quality. 38% decrease on the thermal resistance of SDL was realized. The CW power exceeding 27 W, limited by the available pump power, was demonstrated.

Polarization-stable vertical-cavity surface-emitting lasers (VCSELs) with a simple fabrication process are presented. The gratings fixing the polarization are defined by a two-step exposure technology taking advantage of the displacement Talbot lithography technique. This enables grating lines to remain within the inner circle mesa of the VCSELs. These surface grating VCSELs with different periods are theoretically modeled and experimentally verified. Most of these VCSELs exhibit full polarization stability as predicted theoretically. For VCSELs with grating periods larger than the emission wavelength we found a weak orthogonal polarization suppression ratio, thereby deviating from those grating VCSELs with smaller periods.

We demonstrated a method of transverse mode selection of vertical-cavity surface-emitting lasers (VCSELs). A ring-shaped anti-phase SiO2 layer was introduced to filter the modes whose intensity distribution overlapped with the extra layer. The effective index method considering the size of the oxide aperture was applied to decide the inner/outer radius of the ring. Conventional reference device and two-round of confirmatory studies of ring-shaped SiO2 VCSEL were fabricated and characterized. In comparison with the spectra of the conventional VCSEL, the VCSELs with ring-shaped SiO2 layer emitted two stable transverse modes over the entire current range. This method may offer a new idea to solve the device request for the few-mode optical communications in the future.

Vacuum interrupter is widely used in the medium-voltage power system. Controlling the arc by the magnetic field is an effective method to improve the breaking capacity. The transverse magnetic field (TMF) forces the constricted arc to rotate to reduce local overheating. In this paper, three kinds of TMF contacts, which are Swastika-type contact, cup-shaped contact, and double-TMF contact that combines Swastika-type and cup-shaped contacts coaxially, are investigated in a demountable vacuum chamber with a high-speed camera. The arc voltage and current are also recorded. The experiments were conducted with circuit currents from 5 to 20 kA (root mean square) with a frequency of 50 Hz. There are four current levels in the experiment, which are 5, 10, 15, and 20 kA, and at least three tests are taken for each current level. The results showed that under low current (I = 10 kA), the arc of the three TMF contacts did not rotate. Under high current (I = 20 kA), it was observed that the arc of Swastika-type and double-TMF contacts rotated in the gap. The arc speed of double-TMF contacts is higher than that of Swastika-type contacts. The cup-shaped contacts have the highest arc voltage and noise among the three TMF contacts. The Swastika-type contacts were eroded most seriously. The simulation results show the force distribution of the arc on different locations. The resultant force makes the arc rotate counterclockwise.