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In this article, a 1-THz traveling-wave tube (TWT) based on flat-roofed sine waveguide (SWG) slow wave structure (SWS) has been studied theoretically and experimentally, and parts of the component have been fabricated. First, the flat-roofed SWG SWS has been optimized for working at 1 THz, the normalized phase velocity is around 0.287, and the interaction impedance is over $3.5~\Omega $ in the frequency range of 1.02–1.04 THz. Meanwhile, the performance of the designed TWT has been simulated, whose saturated output power is 720 mW and the corresponding gain is 28.57 dB. What is more, to decrease the transmission loss of the high-frequency structure, the input and output structures have been designed and a transition structure that transforms the waveguide to standard rectangular waveguide has been proposed. The simulation results show that the reflection coefficient of the novel proposed transmission system is less than −20 dB, and the insertion losses of the transition structure with the input and output waveguides are 2.45 and 1.68 dB, respectively. Finally, the designed SWS has been fabricated by deep reactive-ion etching (DRIE) and tested; ${S}_{{11}}$ is generally less than −10 dB in the frequency range of 1020–1040 GHz.

The $W$ -band flat-roofed sine waveguide (SWG) slow wave circuit was designed and processed in this article. Considering the limitations on present practical fabrication level, sensitivity analysis was performed on the potential influencing factors for the performance of the flat-roofed SWG slow wave structure (SWS). As indicated by the calculation results, the gap between the SWSs and the side-wall strips could have a significant impact on the dispersion, interaction impedance, and the transmission of the entire slow wave circuit. Based on the theoretical analysis, two types of $W$ -band flat-roofed SWG slow wave circuits were fabricated and tested. The side-wall strips of the two circuits are processed with/without rounded corner. The circuit without rounded corner may cause a large gap and severe reflection. In comparison, the other one with rounded corners can make the parts fit tighter, thus minimizing the potential gap. The test results demonstrate that the $W$ -band flat-roofed SWG traveling-wave tube (TWT) possesses a voltage standing wave ratio less than 1.8, which is basically consistent with the simulation results.

To meet the ever-upgrading sulfur-content standard of fuel oil, aerobic oxidative desulfurization (AODS) of fuel has become a research focus for its advantages of high efficiency and low cost. Herein, monodisperse polyoxometalate (POM) clusters immobilized by poly(ionic liquid) (PIL) have been successfully supported on graphene through a one-step bottom-up strategy and used as robust catalysts for AODS with air as oxygen source. Systematical characterizations were applied to investigate the structural features and formation mechanism. The catalyst synthesized via non-covalent interactions possessed high specific surface area and large mesoporous size. POM anionic clusters were uniformly monodispersed on the surface of the material, which endowed the catalyst with excellent heterogeneous catalytic performance. Detailed experiments for desulfurization of model fuel were subsequently performed to explore the influence of crucial parameters. The optimal catalyst achieved complete conversion of sulfides under mild condition, which could be reused at least six times without noticeable decreases of the catalytic performance. Based on the obtained results, the POM/PIL/Gr composite is expected to serve as efficient, robust and recyclable catalysts for ultra-deep oxidative desulfurization.

In this article, a potentially pseudoperiodic slow wave structure (SWS) for a broadband, high-power, helix traveling-wave tube (TWT) is studied. The structure considered here suppresses the back-wave oscillations caused by a large working current. These oscillations do not have conventional uniform pitch distributions in the radial dimension; rather, the two configurations studied in this article are a uniform pitch gradient and a conical helix. Through a reasonable design and a large number of calculations, the entire tube consists of four tapered, pitch-varying SWSs. In addition, to achieve an 8–18-GHz broadband, high-power output, a double-ridged waveguide window output coupler is designed, fabricated, and tested. The 3-D electromagnetic simulation software CST STUDIO SUITE is used to verify the performance of the tube. The simulation results show that the potentially pseudoperiodic SWS can adequately suppress the backward-wave oscillations, and the tube is capable of achieving an output power of over 6 kW, even with a very wide bandwidth of 8–18 GHz. Additionally, the electronic efficiency varies from 21.5% to 25.8%. The maximum output power is 7.45 kW, corresponding to an electronic efficiency of 25.8% at 14 GHz.

O2 activation for the green conversion of chemicals has attracted a great deal of attentions in the field of chemistry. Developing catalysts for aerobic oxidation with both prominent instinct activ...

It is extremely important to explore the synthesis methodology and application scope of functional polymer brush-based nanocomposites. In this work, an ultrasensitive sandwich-type electrochemical immunosensor based on a polymer brush/graphene oxide (GO) nanoprobe was designed for the quantitative detection of alpha fetoprotein (AFP). As the backbone of the polymer brush, polyacrylonitrile-g-GO (PAN-g-GO) was efficiently prepared via surface-initiated atom transfer radical polymerization (SI-ATRP). Benefiting from the large number of nitrile groups in PAN, the poly(vinyltetrazole-co-hydroxyethyl methacrylate)-g-GO (P(VT-co-HEMA)-g-GO) was synthesized through nitrile click chemistry. Furthermore, the immunosensor reached the design requirements of a high sensitivity as the P(VT-co-HEMA)-g-GO was connected to plenty of signal labels. Importantly, the designed immunosensor showed a wide range (2.5 × 101–5 × 104 pg mL−1) (R2 = 0.993) and a low detection limit (LOD, ∼0.183 pg mL−1) with a high selectivity, good reproducibility and excellent stability. Therefore, these polymer brush-based nanocomposites can provide potential applications for determining tumor markers (TMs) with robust signal amplification capability.

This paper explores the thermal characteristics of a helix traveling wave tube (TWT) in the Ka-band (26.5-40 GHz) based on rectangular semi-metallic rods formed by welding boron nitride and copper. The results reveal that the maximum temperature of the helix during TWT operation for this supporting rod structure is 339.2°C. A comparison of the thermal characteristics about this structure with those of a conventional dielectric rod shows that the helix temperature of the former is about 40°C lower than that of the latter during operating conditions.

Driven by success in areas such as computer vision and natural language processing, attempts have been made in this work to combine deep learning with the large signal of the Traveling Wave Tube (TWT) to assist in predicting the output performance of the tube and advancing the pre-design of TWT. By feeding the trained artificial neural network with several feature parameters, the output power with the tube length can be predicted.

The development of a 340GHz modified sine waveguide vacuum electron amplifier is presented here. Output power from this structure is predicated to exceed 10W with a pencil beam electron gun at 17 kV and 38mA. Design, fabrication and test of slow wave structure (SWS) and pillbox window are discussed respectively. The cold test results show a good agreement with the simulation, which verified the properties of low loss and wide bandwidth of the high frequency system.

Wearable strain sensors have received widespread attention in research fields due to their applications in human motion detection. In this manuscript, the fabrication of functionalized Janus graphene oxide (GO) nanosheets were used by Pickering emulsion template. Polypyrrole (PPy) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) were asymmetrically grafted on the two sides of GO (GO@PPy/PDMAEMA Janus NS), which successfully applied to synthesize Janus NS/guar gum-poly(acrylic acid) (GG-PAA) self-healing nanocomposite hydrogels. The outstandingly improved self-healing efficiency (92.8% for 2 h) and mechanical properties (strength of 4.12 MPa and toughness of 873.8%) of nanocomposite hydrogels were mainly supported by the collaborative effect of reversible electrostatic interactions, multiple hydrogen bonds and metal-ligand coordination. Moreover, the hydrogels exhibited strain sensitivity and could be able to monitor a variety of human motions, which have outstanding application prospects in wearable flexible sensors.

In this paper, a functional nanoprobe based on graphene oxide (GO) composites was successfully prepared for detection of mercury ion (Hg(II)) with high sensitivity. GO as a substrate was modified and used for the growth of polymer chains to synthesize polyacrylonitrile-grafted GO (PAN-g-GO) by activator generated by electron transfer atom transfer radical polymerization (AGET ATRP). Under the condition of visible light shines, the PAN-g-GO was further modified to prepare [poly(acrylonitrile-co-vinyl(diphenyl pyridine))]-grafted GO (P(AN-co-PHPY)-g-GO) nanomaterial by one-step synthesis. Finally, P(AN-co-PHPY)-g-GO as a nanoprobe was dropped to the surface of the glassy carbon electrode and assembled to the electrochemical sensor. Moreover, it can effectively improve the enrichment capacity of mercury ions and increase the electron transfer rate on the electrode surface. Differential pulse anodic stripping voltammetry (DPASV) was used to evaluate the electrochemical performance. Under optimum conditions, the response of Hg(II) at this resulting sensor was linear in the range of 2.0 μM~0.1 nM with a detection limit of 0.06 nM. Additionally, this sensor showed excellent reproducibility, selectivity and stability.

A label-free DNA Y junction sensor for amplified detection of Hg2+ has been demonstrated by using thymine-Hg2+-thymine (T-Hg2+-T) recognition, cascade toehold-mediated DNA strand displacement and dye staining double-stranded DNA (dsDNA). In our work, assistant DNA could bind with the first hairpin DNA with toehold domains by the help of thymine-Hg2+-thymine (T–Hg2+–T) base pairs recognition. The second hairpin DNA with toehold domains will then hybridize with the complementary sequences in first hairpin DNA, which again initiates a new toehold domains to open the third hairpin DNA, triggering a cascade strand displacement reaction. Exonuclease III (Exo III) was added to digest the three hairpin DNA with recessed 3′ ends in the absence of Hg2+ to reduce the background signal. As a comparison, Exo III is replaced by GO to reduce the background signal because single-strand DNA (ssDNA), three hairpin DNAs with intercalated dye could be adsorbed onto the surface of GO and lead to quenched fluorescence. The method, designed in a simple “mix, incubate, and detect” format, can detect concentrations of Hg2+ as low as 0.031 nM, and exhibit good selectivity and practical application.

Hydrogels with the properties of self-healing, toughness, stiffness and strength have great potential for use in smart materials. Herein, self-healing and tough hydrogels were successfully prepared after adding modified graphene oxide (GO) composites, which grafted the functional polymers onto the surface of GO. GO@polyacrylonitrile (GO@PAN) was synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP) using GO@BiBB as the ATRP initiator. The nitrile group on GO@PAN was converted to pyridine, for which 2,4,6-triphenylpyrylium tetrafluoroborate (TPPT) was used as the photocatalyst. The prepared GO composite was added into polyacrylic acid (PAA) hydrogels formed by in situ radical polymerization. These tough hydrogels not only have high mechanical strength, but also show excellent self-healing performance. This strategy can provide a novel and universal route for the fabrication of smart hydrogels in biomedical and engineering fields.

In order to make the design results of the traveling wave tube (TWT) coincide with the experiments very well, we need to build a bridge between the actual electron situation and the beam-wave interaction. In this paper, considering the actual magnetic field distribution, the macro particle data at the waist position is processed by MATLAB to meet the needs of the interaction calculation model, so as to realize the integrated design of electron gun, magnetic system and interaction calculation using CST studio suite.

In this paper, the high frequency characteristics of Trapezoidal Staggered Grating Slow-wave Structure for 1THz Traveling Wave Tube has been studied. The transmission structure has been simulated, the reflection coefficient is less than -20dB in the frequency of 1015GHz to 1055GHz and the loss of the structure is over 58dB. The PIC simulation shows that the saturation output power is 405mW at the frequency of 1030GHz, and the corresponding gain is 19.08dB.

This paper describs a fan-shaped metal loaded helix traveling wave tube working at Ka–band. It has the gain of 37.3-48.7dB, electronic efficiency of 15.18%-19.42% and output power is greater than 286W when it works at a voltage of 9KV and a current of 210mA. The simulation results of VSWR for its coaxial energy coupler are below 1.35, and the test results of it is below 2.1 at the working frequency range.

In order to predict the saturation output power of traveling wave tubes rapidly, analytical expression has been worked out. This theory is verified by comparison with two of large signal theory.

The high frequency characteristics and beam wave interaction characteristics of a Ka-band (26-40GHz) helix traveling wave tube (TWT) with rectangular semi-metallic rod are presented. The design results show that the TWT has the gain of more than 42dB, the output power of more than 220W and the electronic efficiency of more than 19% in the working bandwidth. Now the high frequency structure of the TWT are manufactured, the preparation for the transmission test is in progress.

This paper introduces a high-stability electron optical system for millimeter wave traveling wave tubes. Firstly, a circular electronic injection Pierce electron gun is designed. The electron channel radius is 0.2mm, the current is 90mA. Then the immersed flow method was used to design a ppm focusing system with a magnetic field period of 7.3 mm and a peak value of 4900 Gauss. The stability of the immersed flow electron gun is compared with the gun under a conventional ppm magnetic field in consideration of thermal deformation and assembly errors.

A W-band multi-beam traveling-wave tube (TWT) based on sine slow-wave structure is designed. The cold bandwidths of the fundamental and higher-order modes in the slow-wave circuit are analyzed using HFSS software. Through reasonable structural design, the fundamental mode and low-order mode are suppressed. The beam-wave interaction capability of the multi-beam TWT is analyzed based on the high-order mode transmission design. At the voltage of 11.7 kV, the current density of the sheet electron beam is 96 A/cm2 which can be produced by the non-convergent electron gun, and the output power is over 150 W in the operating frequency 90 GHz-100 GHz.

COVID-19 has become a global pandemic. However, the impact of the public health interventions in China needs to be evaluated. We established a SEIRD model to simulate the transmission trend of China. In addition, the reduction of the reproductive number was estimated under the current forty public health interventions policies. Furthermore, the infection curve, daily transmission replication curve, and the trend of cumulative confirmed cases were used to evaluate the effects of the public health interventions. Our results showed that the SEIRD curve model we established had a good fit and the basic reproductive number is 3.38 (95% CI, 3.25–3.48). The SEIRD curve show a small difference between the simulated number of cases and the actual number; the correlation index (H2) is 0.934, and the reproductive number (R) has been reduced from 3.38 to 0.5 under the current forty public health interventions policies of China. The actual growth curve of new cases, the virus infection curve, and the daily transmission replication curve were significantly going down under the current public health interventions. Our results suggest that the current public health interventions of China are effective and should be maintained until COVID-19 is no longer considered a global threat.

Next generation optical storage based on photostimulated luminescence (PSL) materials is a significant data storage technology for the information age. For a better signal durability and resolution, it is necessary to develop PSL phosphors with deep traps in a narrow distribution. Accordingly, in this short letter, we report a unique Y2GeO5:Pr3+ PSL phosphor with a narrow trap distribution (0.3 eV) and a trap depth of 1.31 eV, which is presently the deepest value. After charging by ultraviolet (254 nm) irradiation (data writing), the PSL of Pr3+ can be stimulated by an 808 nm (1.53 eV) laser (data reading). This finding reveals that electrons stored in the deep traps are sufficiently stable under a thermal disturbance at room temperature and even under stimulation by a 980 nm (1.26 eV) laser. Additionally, the deep traps are isolated and demonstrate little interference with the shallow traps. Therefore, the deep-trap Y2GeO5:Pr3+ phosphor shows potential applications in optical data storage.

A sine waveguide (SWG) traveling-wave tube with sheet electron beam tunnel is proposed to amplify the high-frequency terahertz wave. In this study, the slow wave characteristics including the dispersion properties and interaction impedances have been investigated by using the eigenmode solver in the 3D electromagnetic simulation software Ansoft HFSS. The truncated SWG slow wave structure possesses the relatively large average coupling impedance. The beam–wave interaction characteristics of truncated SWG with sheet electron beam tunnel are calculated by high-frequency simulation software CST. From the particle-in-cell simulation results, this beam–wave interaction circuit can produce >490 mW ranging from 0.845 to 0.855 THz with a corresponding gain over 22 dB.

A sensitive sandwich-type electrochemical immunosensor based on polyacrylonitrile-g-poly(hydroxyethyl methacrylate) (PAN-g-PHEMA)/graphene oxide (GO) composites was prepared for the ultrasensitive detection of tumor markers (alpha fetal protein, AFP as a model). The functional polymer brush was efficiently prepared by the union of cyano click chemistry and controlled/“living” radical polymerization (CRP). The designed immunosensor showed a low limit of detection (LOD, ∼0.285 pg mL−1), with a wide detection range (2.5 × 101 to 2.5 × 104 pg mL−1) (R2 = 0.9876). The electrochemical immunosensor also exhibited high sensitivity, favorable stability, excellent reproducibility and good selectivity towards AFP. Moreover, the immunosensor could be applied to the analysis of AFP in serum samples with satisfactory results. This present work may provide a general model for the detection of tumor markers based on sandwich-type immunosensors.

A novel strategy based on nanoprobes for signal amplification was introduced in an electrochemical immunoassay platform. The nanoprobes based on poly(2-hydroxyethyl methacrylate)-r-poly(acrylic acid) (PHEMA-r-PAA) and graphene oxide (GO) have the effect of double signal amplification. The resulting sandwich-type electrochemical immunosensor was able to detect the tumor marker alpha fetal protein (AFP) with high sensitivity and high selectivity. A good linear relationship could be observed in the AFP concentration range of 3.5 pg mL−1 to 35 ng mL−1 (R2 = 0.9898), and the minimum detection limit was 0.106 pg mL−1. In addition, the electrochemical immunosensor exhibited good stability and could be applied to AFP detection in clinical serum.

Aerobic oxidative desulfurization (AODS) is a vital development aspect for the deep desulfurization of fuel, which requires catalysts with high performance to efficiently convert thiophenic sulfides to sulfones. Here CoFeMo mixed metal oxides (MMOs) were synthesized through the calcination of molybdate (MoO42-) intercalated CoFe layered double hydroxides (LDHs), which can serve as a robust and durable catalyst for AODS. The catalysts were synthetically characterized by using a range of techniques to identify its chemical and morphological properties, which showed that the content and electronic structure of Mo sites can be regulated by altering the intercalation content of MoO42-, and ultimately affect their catalytic performance. The optimal catalyst was capable of efficiently catalyzing the aerobic oxidative conversion of various thiophenic compounds into sulfones at 100 °C, and exhibited an excellent reusability by keeping the unchanged activity and chemical structure in repeated uses. This study would develop a feasible method to synthesize the highly efficient MMO catalysts for AODS of fuels.

Honeycomb ordered NaNi 2/3 Sb 1/3 O 2 (NNSO) is synthesized via a conventional solid-state approach and investigated as cathode material for sodium ion batteries. The effect of sintering temperature is clearly unraveled by combination with electrochemical measurements and in-situ XRD tests in detail. The temperature dependence of Na + (de)intercalation on NaNi 2/3 Sb 1/3 O 2 electrodes is pioneeringly evaluated. It is suggested that the appropriate operating temperature will facilitate the formation of well-crystallized honeycomb structure and improve the electrochemical performance effectively. The as-prepared NaNi 2/3 Sb 1/3 O 2 obtained at the optimal temperature of 950 °C delivers a high capacity of 113.8 mAh g −1 at 0.1C and a good retention performance of 65 mAh g −1 at 0.5C after 100 cycles. The results reveal that the structure transformation and electrochemical property, as well as thermal stability of NaNi 2/3 Sb 1/3 O 2 cathode are strongly dependent on sintering temperatures, which provide an insight into the preparation of newly electrodes with excellent Na + ion storage property.

A novel slow-wave structure (SWS), named ridge-loaded sine waveguide (RLSWG), has been proposed to develop the wideband high-power terahertz traveling-wave tube (TWT). The slow-wave characteristics of the RLSWG SWS, including dispersion properties and interaction impedance, are analyzed by using the 3-D electromagnetic simulation software Ansoft high frequency structure simulator (HFSS). From our calculation, the average interaction impedance of the RLSWG SWS at 0.22 THz is 42.2% higher than the conventional SWG SWS. Meanwhile, the simulation results demonstrate that the RLSWG SWS possesses low ohmic losses and reflection. Moreover, the particle-in-cell (PIC) simulation results reveal that, with the cylindrical electron beam of 20.9 kV and 45 mA, the output power and electron efficiency of the RLSWG TWT at the typical frequency of 0.22 THz can reach 52.1 W and 5.54%, respectively. In addition, the 3-dB bandwidth of the RLSWG TWT exceeds 25 GHz. Compared with the SWG TWT, the RLSWG TWT has the shorter tube length and can generate the larger output power.

An electrochemical immunosensor based on poly(2-hydroxyethyl methacrylate) (PHEMA)/graphene oxide (GO) nanocomposite was designed in a simple way for the ultrasensitive detection of tumor makers (alpha-fetoprotein, AFP as a model). PHEMA with excellent biocompatibility, provides a large number of sites for connecting signal molecules. After modification with signal molecules, the functional PHEMA significantly improved the sensitivity of electrochemical detection. In order to immobilize antibodies, GO was introduced and used to construct a nanocomposite as a substrate. The designed AFP immunosensor showed favorable selectivity and excellent stability. Meanwhile, it has a low detection limit of 0.403 pg mL−1. Furthermore, the immunosensor was used to detect target AFP in human serum, demonstrating the feasibility of clinical diagnosis.

In this paper, multiphysics field simulation is applied to analyze the temperature distribution of Ka-band U-shaped microstrip line planar TWT considering the thermal losses induced by ohmic loss and electron collision losses. The beam-wave interaction of the planar TWT is analyzed by using CST particle-in-cell (PIC) solver, at the same time the thermal losses distribution is recorded, which will be the heat source. The simulation results show that the high temperature with a peak value of 263 °C.

AIM RCT-18 is a recombinant fusion protein that interferes with the selection and survival of mature B-lymphocytes by inhibiting B-lymphocyte stimulator and a proliferation-inducing ligand. METHODS This single blind, randomized, placebo controlled, clinical pharmacological study explored the short term efficacy and safety of RCT-18 in 21 rheumatoid arthritis (RA) patients with three different dosing regimens. The pharmacological behaviour of RCT-18 was also characterized through a six level biomarker cascade approach to identify potential predictors for clinical responses. RESULTS Nine out of 10 patients (>80%) experienced moderate to good EULAR response at the end of 3 months with once or twice weekly doses of 180 mg RCT-18, whereas weekly administration of 360 mg RCT-18 or placebo, however, only resulted in moderate improvement in one patient in each group. Absence of IgM-type rheumatoid factor reduction, recovery of IgM 2 weeks after drug cessation, lack of decrease in the count of CD27(+) B-lymphocytes and a DAS28 change from baseline

A novel ridge-loaded staggered single-slot rectangular coupled-cavity traveling-wave tube (CC-TWT) operating at $X$ -band is presented. It features large interaction impedance and good thermal dissipation with a moderate bandwidth. Compared with the existing staggered single-slot rectangular CC-TWT and Hughes-type TWT, this structure has the advantage of large coupled impedance and high electron efficiency, which makes it potentially useful for miniaturization in CC-TWT. The electromagnetic characteristics and the beam–wave interaction based on this slow-wave structure are investigated. The calculation results predict that it potentially could provide saturated output power over 20 kW from 8.5 to 9.8 GHz when the cathode voltage is set from 25.4 to 26.4 kV and the beam current is 5 A, respectively. The corresponding saturated gain and the electron efficiency can reach over 34.4 dB and 15.2%. From 8.6 to 9.5 GHz, the gain is even over 38.6 dB, and the electron efficiency is more than 16.9%. The cold test results show that the voltage standing wave ratio of the high-frequency structure is below 2 at the range of 8.5–10 GHz.

A V-band traveling-wave tube (TWT) prevails nowadays as an amplifier device for satellite communication and electronic countermeasures. The folded waveguide (FW) is a promising slow-wave structure for V-band TWT with advantages of high power and considerable bandwidth. A novel FW periodically loaded with right-angled rectangular grooves is analyzed for the purpose of gaining higher power within a shorter circuit. The radio-frequency characteristics are investigated by numerical simulation, and the nonlinear large-signal performance of such a TWT is analyzed by a 3-D particle-in-cell code MAGIC. Compared with normal circuits, a relatively higher continuous-wave power (60–80 W) and a similar bandwidth (5 GHz) at V-band are predicted by simulation. Meanwhile, the novel circuit is also shorter when the output power becomes saturated. It, therefore, will favor the miniaturized design of a broadband and high-power V-band TWT.

A two-section Folded rectangular groove waveguide (FRGWG) Slow wave structure (SWS) Traveling wave tube (TWT) with large dimension of beam tunnel is studied. Compared with the Folded waveguide (FWG) under the same size parameters conditions, the interaction impedance and center frequency of the FRGWG are higher. The advantage is that a beam tunnel with large dimension can be applied to the FRGWG without the influence caused by signal decrease, reflection and oscillation. The microwave amplification capability based on beam-wave interaction is obtained through the particle-in-cell method. This circuit structure can produce an output power of over 100W ranging from 136 to 142GHz when the operation voltage and beam current are set as 18.4kV and 150mA, respectively, for a 95mm long circuit.

In this manuscript, self-healable nanocomposite hydrogels were successfully fabricated by combining surface-initiated photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP) with mussel-inspired chemistry. Using these efficient and eco-friendly methods, poly(4-vinylpyridine) (P4VP) was initiated on the surface of graphene oxide (GO) via PET-ATRP with polydopamine (PDA) as the anchor and 10-phenylphenothiazine (PhPTZ) as organic photocatalyst, respectively. After in-situ polymerization of acrylic acid, self-healing nanocomposite hydrogels were successfully obtained, and they had excellent tensile strength (about 6.94 MPa), toughness (605%) performance as well as self-healing efficiency (94.9% after 8 h).

Janus nanomaterials can be highlighted to design a series of smart materials with the remarkable characteristic of two different properties or constituents. In this manuscript, functional Janus graphene oxide-type (GO-type) nanomaterials were fabricated by Pickering emulsion template and successfully applied to develop of dual self-healing nanocomposite hydrogels. Asymmetric functionalization of Janus nanosheets were achieved in typical oil-in-water Pickering emulsion by atom transfer radical polymerization (ATRP) and mussel-inspired chemistry. Poly(2-(acryloyloxy)ethyl ferrocenecarboxylate) (PMAEFc) and polydopamine (PDA) were unsymmetrically grafted on the two sides of GO (Janus GO-PMAEF/PDA (JGNs)), which successfully applied in self-healing nanocomposite hydrogels. The collaborative effect of metal-ligand coordination and host-guest interaction make the dual self-healing hydrogels have excellent self-healing properties (self-healing efficiency can reach to 93.4% within 1 h) and mechanical strength (tensile strength of 0.94 MPa and strain of 508.5%). Therefore, these chemical asymmetric JGNs have outstandingly application prospect in the development of smart materials.

A green strategy by integrating surface-initiated metal-free photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP) with mussel-inspired polydopamine (PDA) chemistry, was used to fabricate multi-walled carbon nanotubes (MWCNTs)/poly(4-vinylpyridine) (P4VP) nanocomposites. Self-healing nanocomposite hydrogels were facilely designed with these nanocomposites through dynamic supramolecular interactions. Using mussel-inspired PDA chemistry from MWCNTs, nanocomposites (MWCNTs@PDA-P4VP) were successfully prepared by metal-free PET-ATRP with MWCNTs@PDA-Br as an initiator, rhodamine B as photocatalyst, 4-vinylpyridine (4VP) as monomer, respectively. Importantly, the obtained nanocomposite hydrogels had high mechanical strength (2.9 MPa), prior fracture strain (633.8%) and excellent self-healing property (90.6%). These methodologies will provide opportunities for the design of eco-functional materials or flexible biosensors.

A wideband coaxial line to double-ridge waveguide window for broadband high power THz TWT has been studied in this paper, which can cover the 270–370 GHz with a ultra-bandwidth over 0.1 THz. Based on the mode conversion theories and impedance matching techniques, the broadband transition of coaxial line to double ridge waveguide is designed. In addition, the diamond is adopted to design the broadband double ridged waveguide window. The characteristics of the transition are analyzed by using the full-wave analysis software. According to the simulated results, the reflection coefficient is less than −20 dB and the VSWR is less than 1.2 in the 270–370 GHz.

A 0.65 THz traveling-wave tube was designed based upon truncated sine waveguide slow-wave structure. The high frequency characteristics and transmission characteristics are analyzed and calculated by Ansoft High frequency simulation software. We have also studied and simulated the beam-wave interaction of this truncated sine waveguide traveling-wave tube. The results show that the peak output power is 270 mW from 640 GHz to 660 GHz with synchronous voltage of 18.9 kV, operation current of 11 mA and input power of 1.25 mW.

This paper reported a Q-band sheet beam slot-line backward wave oscillator (BWO). The characteristics of slot-line slow wave structure (SL-SWS) has been investigated and the result shows that it's much more suitable to be designed as a BWO than a traveling wave tube (TWT). The slot-line backward wave oscillator is driven by a 0.19A sheet beam whose rectangular cross section is 0.9mm*0.12mm. While the beam voltage ranges from 6000V to 10000V, the frequency of output signal varies from 40.275GHz to 43.925GHz, and the output power is over 40W.

A W-band phase-velocity-taper Sine waveguide traveling wave tube (TWT) with sheet electron beam is proposed to amplify the millimeter wave. In this paper, the high frequency characteristics of sine waveguide with sheet electron beam tunnel are simulated by 3-D high frequency simulation software. The simulation results also show that the tube with phase taper structure can produce over 235W output power and 32dB gain at typical frequency 94GHz with an operating voltage of 20.3 kV, a current of 0.2A, and an input power of 150mW. The corresponding gain is more than30dB from 90GHz to 100GHz. The particle-in-cell simulation results indicate that the phase-velocity-tapered sine waveguide structure can increase the output power 46% at 94 GHz.

A 0.38THz Traveling Wave Tube (TWT) based on the sine waveguide and sheet beam tunnel is proposed to amplify the terahertz wave. In this paper, the high frequency characteristics of sine waveguide with sheet beam tunnel are calculated by 3-D high frequency simulation software. From the particle-in-cell simulation results, this beam-wave interaction can produce output power 13W at 0.38THz, and the corresponding gain reaches 34.15dB. In addition, the 3-dB bandwith of the sine waveguide TWT exceeds 36GHz.

The paper describes the design of an X-band coupled-cavity traveling-wave tube (CC-TWT) based on the reentrant double-staggered ladder coupled-cavity slow wave structure (SWS) using High Frequency Structure Simulator (HFSS) and particle-in-cell (PIC) code in Computer Simulation Technology (CST) Particle Studio. When the cathode voltage and cathode current are 25.9 kV and 5 A, respectively, the PIC simulation results show that the corresponding saturated output power is over 20kW from 8.6 to 9.7 GHz, the maximum output power can reach 28.8 kW at 9.2 GHz, and the electronic efficiency and the gain can reach over 15.6% and 40 dB.

A new type of folded frame slow-wave structure (SWS) is introduced and used in the design of a low-voltage, high-efficiency, and widebandwidth millimeter-wave traveling-wave tube (TWT). The high-frequency characteristics of the folded frame structure, including dispersion properties, coupling impedances, and reflection characteristics are investigated. The beam-wave interaction of the TWT with the folded frame SWS working at the millimeter-wave frequency range is also calculated using 3-D particle-in-cell algorithms. The simulation results reveal that with sheet electron beam parameters of 6000 V and 0.2 A, the average output power and electron efficiency can reach 196 W and 16.3%, respectively. Compared with the symmetric double V-shaped microstrip meander-line SWS, the folded frame SWS has larger coupling impedances and can generate higher output power.

A novel ridge-loaded folded waveguide slow-wave structure has been firstly employed to manufacture a W-band continuous wave traveling wave tube (TWT). This letter reports the processes of the design and experimental test for this TWT. From the experimental results, over 25-W output power are produced within the operation bandwidth from 93.1 to 94.8 GHz, which is in accordance with the simulation results.

The design and analysis of a high power and high e-ciency helix traveling-wave tube operating in the Ka-band are presented. First, a double-slotted helix slow-wave structure is proposed and employed in the interaction circuit. Then, negative phase-velocity tapering technology is used to improve electronic e-ciency. From our calculations, when the design voltage and beam current are set to be 18.45kV and 0.2A, respectively, this tube can produce average output power over 800W ranging from 28GHz to 31GHz. The corresponding conversion e-ciency varies from 21.83% to 24.16%, and the maximum output power is 892W at 29GHz.

A novel slotted helix slow-wave structure (SWS) is proposed to develop high power, wide-bandwidth, high reliability millimeter-wave traveling-wave tube (TWT). This structure, which can improve the heat dissipation capability of the helix SWS, evolves from conventional helix SWS with three parallel rows of rectangular slots made in the outside of the helix. In this paper, thermal stress analysis, the electromagnetic characteristics and the beam-wave interaction of this structure are investigated. The conclusions of this paper will be a great help for the design of millimeter-wave traveling-wave tube.

A novel folded-wave guide (FWG) slow-wave structure (SWS) with sheet-beam tunnel is presented for the high-power and considerable bandwidth in terahertz (THz) wave band. Its electromagnetic characteristics and nonlinear interaction between the electron beam and the electromagnetic field were investigated. A novel input and output coupler was proposed that could produce good input and output matches. The particle-in-cell simulation results revealed that the tube can be expected to produce over 100 W of average power in the range from 141 to 146 GHz, assuming an RF input signal with an average power of 45 mW. Compared with the conventional folded-waveguide traveling-wave tube (FWGTWT) at 140 GHz, the novel FWGTWT had a 48% higher output power, and the novel FWGTWT can operate at same frequency band with larger dimensional parameters. Meanwhile, the novel FWG was also much shorter than the normal FWG with good performance at the working frequencies. It, therefore, will favor the miniaturized design of a high...

Theoretical studies of the growth rate in a Cherenkov Free-Electron Laser with two beams are presented in this paper. The spatial growth rate is derived based on the dispersion equation with electron beams at the operating point and is calculated numerically. The results show that the introduction of the second beam significantly improve the growth rate.