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Sintering additives and micro-powder injection molding offer an effective method to densify boron carbide (B4C) and make B4C components with complex shapes. By adjusting the proportion of three kinds of powders (SiC, Al2O3 and Y2O3), four kinds of sintering additives were prepared. The feedstock uniformity, debinding behavior, phase composition and microstructure of micro injection molded B4C components with different sintering additives were studied. The results showed that the defects such as lattice distortion and vacancy were introduced into ball milling, which increase the surface energy and benefit subsequent sintering densification. The feedstock had good uniformity and rheology that met the requirements of micro powder injection molding. After debinding, B4C components had enough strength and showed certain sintering characteristics. The addition of sintering additives was beneficial to densification and sintering temperature reduction. The addition of sintering additives formed a second phase in the B4C crystal and at the grain boundary of B4C crystal, which changed the fracture mode from transgranular fracture to mixed fracture mechanism with transgranular fracture.

This letter presents a parallel-feedback dual-frequency oscillator (DFO) with low phase noise. It is achieved based on the filter switching technique. By using four switches to control two oscillator loops with a common active device, the oscillation frequency of the proposed DFO can be switched from one to another. Due to the high isolation level of the employed switches, the two oscillator loops almost operate independently. Thus, there is no intermodulation (IM) spurs generated in the output spectrum of the proposed DFO. In the meantime, to improve the phase noise performance of the DFO, each oscillator loop utilizes a high frequency-selectivity bandpass filter with high group delay (GD) as a frequency selective element. In this way, the low phase-noise DFO is developed. For demonstration, the DFO is designed, fabricated, and tested. As seen from the measurement results, the oscillator can oscillate at 2.04 or 3.092 GHz by controlling the four switches. At 100 kHz and 1 MHz frequency offset from the carrier frequency, the phase noises are -108.5 and -129.7 dBc/Hz for 2.04 GHz, while -112.7 and -135.7 dBc/Hz for 3.092 GHz.

Benefiting from the mature technology of ceramic injection molding, Fused deposition modeling based on highly-filled ceramic-polymer granular feedstocks has been showing great potential and advantage for fabricating 3D ceramics. Herein, 3D zirconia ceramics using granular feedstock were fabricated, and typical morphology, surface quality, and effect of the thermal accumulation on 3D structure were clarified. Typical morphology of printing steps on the surface were quantitatively characterized, and determined by the surface curvature and layer height of the printed structure. Aligned triangular pores were confirmed at the junction of the deposited filaments with elliptical cross-section morphology. Simple square plates with different size were used to illustrate the influence of thermal accumulation on the morphology of 3D structure. Small printing size increased the thermal accumulation during deposition, resulting in decreased printing quality caused by the secondary over-melting of former deposited layers. Except for the pores at the junctions, dense zirconia ceramics with uniform structure and smooth surface could be achieved. A low-cost and high-quality route for the preparation of 3D ceramics was demonstrated via FDM of highly-filled granular feedstocks.

Edge computing is an emerging computing architecture. The scheduling and optimization of the tasks on the edge side of the smart factory can effectively reduce the processing delay and improve the utilization efficiency of servers. This study focuses on the problem of edge-side task scheduling with the goal of minimizing the maximum completion time of the tasks. A first-price sealed-bid auction based algorithm and a genetic algorithm with elite retention strategy are designed to solve the problem. The experimental results indicate that the auction-based scheduling algorithm has better real-time performances compared to the genetic algorithm.

Difference in lattice parameters and physical properties of core-rim structure leads to mismatch at the core-rim interfaces. In this respect, VC was adopted to shrink the lattice of rims and intended to reduce the lattice misfit. Small amount of VC (0.8 wt%) effectively decreased the grain size from 0.77 μm to 0.57 μm, with an increased lattice parameter of the core-rim phase. Higher VC content accelerated the dissolution and precipitation process, resulting in the formation of thicker rims and smaller lattice parameters of core-rim structure. The same lattice parameters of core-rim phases were achieved with 4.8 wt% of VC addition. A distortion zone with a thickness of 3–5 atomic layers was confirmed, which located at the boundary of binder and gray rim. VC induced the formation of spherical rimless grains, which were uniformly dispersed in the binder and usually attached to the coarse core-rim grains. Black ultrafine rimless grains exhibited larger lattice parameters than Ti(C,N) cores due to the increased C/N ratios. Ti(C,N)-based cermets with uniformly dispersed rimless grains were achieved, which showed effectively improved the bending strength of cermets, with in-situ formed dimples inside the binders during the fracture.

Frequency-adaptive bandpass diplexer (FA-BPD) with constant absolute bandwidths (ABWs) and two identical passbands at every state is the most useful duplexing tunable filter for the smart frequency-division duplex (FDD) system. However, it is widely considered a challenge. In this article, we propose a new synchronously tuned trimode resonator (STTR) to achieve such a type of FA-BPDs. The proposed STTR has three flexible resonant modes that are able to be synchronously tuned by only one bias with the predefined frequency spacings. The spacings between every two tunable resonant frequencies can be precisely controlled as desired. Consequently, the resultant tunable filters can be implemented with different constant ABWs and at the different center frequency, which makes it possible to achieve two frequency-adaptive bandpass filters (FA-BPFs) at different frequency ranges but with the same ABW. Based on the proposed STTR, a three-pole FA-BPF with nearly 250-MHz ABW is examined. Using the FA-BPF as basic building blocks, a 1.5–3.5-GHz FA-BPD with identical passband and constant ABW is developed finally. The simulation and measurement results confirm the proposed design method and also exhibit the merits, such as low loss, simple design, wide frequency tuning range with synchronous passband.

In this paper, we designed a three-band narrowband perfect absorber based on bulk Dirac semi-metallic (BDS) metamaterials. The absorber consists of a hollow Dirac semi-metallic layer above, a gold layer below and a photonic crystal slab (PCS) in the middle. The study found that the terahertz wave absorber achieved three perfect absorption rates of more than 95% in the range of 1 to 2.4 THz. The minimum bandwidth (FWHM) is 0.02 THz, and the maximum quality factor (Q) is 106. A reasonable explanation of high absorption can be obtained by impedance matching, electric dipole and other principles. The absorption spectra of the two polarizations show different responses at different incident angles. In addition, we also obtained the influence of the structural parameters of the upper layer of the metamaterial on the absorption performance. We defined the refractive index sensitivity (S) with a maximum sensitivity of 0.1525 THz RIU-1 and a highest quality factor (FOM) of 4.26 in the refractive index range of 1 to 1.8. The maximum adjustable range is 0.06 THz in the Fermi energy range of 60 to 140 meV. Because of its excellent characteristics, our absorber will have good development prospects in the fields of optical switching, biochemical imaging, and space detection.

This article proposes an advanced synthesis of the frequency-adaptive bandpass filter (FA-BPF) with constant absolute bandwidth (ABW). The proposed synthesis is based on the element-variable coupling matrix (EVCM), which is directly extracted from the classical filter polynomials. The extraction method is presented, investigated in detail, and confirmed by a set of numerical simulations. All frequency-dependent couplings between the resonators in an FA-BPF are uniquely modeled by the new coupling matrix, and the element variation of the EVCM directly accounts for the frequency tuning behavior of an FA-BPF. This one-to-one correspondence tackles the difficulty of the FA-BPF synthesis and design with a different center frequency tuning range (FTR), a different bandwidth (BW), and a different BW variation rate. This article also proposes the predefined coupling technique in the new synthesis. It allows both nonfrequency-dependent matrix and frequency-dependent matrix in an EVCM to be separately implemented in practice. For experimental demonstration, two four-pole/four-transmission zero (TZ) FA-BPFs with identical passband and constant ABW are implemented and then constitute a frequency-adaptive bandpass diplexer (FA-BPD) with two tunable channels that have identical passband and constant ABW. The measurement results exhibited performance superiority of the design and validated the proposed design method.

In this study, WC-Co composite powder was synthesized by two-step carbonization method using W, Co and C as raw materials. X-ray diffraction (XRD) showed that the η phase (Co6W6C) was kept at 1100 °C for 1 h under vacuum, and it could be completely carbonized into WC-Co composite powders. The surface morphology of WC-Co composite powders was analyzed by scanning electron microscope (SEM). The effects of η phase and second phase (W phase) on WC morphology and Co phase distribution were investigated. Electron backscattered diffraction (EBSD) was used to analyze WC-10 wt% Co cemented carbide particle distribution. Comparison of transverse rupture strength, hardness and fracture toughness of two kinds of WC-10 wt% Co cemented carbides synthesized by WC-Co composite powders + WC and WC + Co respectively, the cemented carbide of composite powders + WC increases the fracture toughness from 11.4 ± 0.3 MPa·m1/2 to 12.4 ± 0.3 MPa·m1/2.

In this paper , by using critical coupling theory analysis and the finite-difference time-domain (FDTD) method for simulation calculations, we indicate theoretically that the graphene-cylinder-metal arrays structure is a perfect absorber with high-sensitivity and polarization-independent in the near-infrared region. The results show that the absorber can achieve a perfect absorption of 99.14%, which is more than 43 times the absorption of bare monolayer graphene (2.3%). In the case of the same geometric parameters, whether transverse magnetic (TM) or transverse electric (TE) polarizations, the absorption and resonance peak wavelength of the absorber are equal , because the graphene-cylinder-metal arrays structure is a highly symmetric structure. Furthermore, through numerical simulation and theoretical analysis, on the one hand, the absorber has high sensitivity up to 939.30 nm/RIU. On the other hand, when the incident light source is normally incident, the absorption performance of the arrays structure does not vary with the change of the polarization angle, that is, the system has polarization-independent characteristics. We believe this work provides a good reference for studying the interaction of enhanced light with monolayer graphene, and opens up new possibilities for the practical application of new photons and optoelectronic devices (such as detectors, sensors, etc.).

In this paper, a tri-band bandpass filter design method was proposed. It is a coupling matrix synthesis method which provides a high freedom for setting zeros, order and bandwidth of each pass band for the first time. By mapping the single-band low pass prototype to the tri-band bandpass prototype using tangent function and then mapping the tri-band bandpass prototype to its practical frequency domain, a tri-band bandpass filter design can be realized finally. To validate the proposed method, a design in MATLAB was given at the end.

In order to significantly improve the absorption efficiency of monolayer molybdenum disulfide (M-MoS2), an ultra-narrowband M-MoS2 metamaterial absorber was obtained through theoretical analysis and numerical calculation using the finite difference time domain method. The physical mechanism can be better analyzed through critical coupling and guided mode resonance. Its absorption rate at λ = 806.41 nm is as high as 99.8%, which is more than 12 times that of bare M-MoS2. From the simulation results, adjusting the geometric parameters of the structure can control the resonant wavelength range of the M-MoS2. In addition, we also found that the maximum quality factor is 1256.8. The numerical result shows that the design provides new possibilities for ultra-narrowband M-MoS2 perfect absorbers in the near-infrared spectrum. The results of this work indicate that the designed structure has excellent prospects for application in wavelength-selective photoluminescence and photodetection.

High-energy ball-milled NiTiC powders were used for preparing Ti(C, N)-based cermets. Effect of NiTiC content on the morphology, composition, interface structure and mechanical properties of cermets were investigated. NiTiC binders promoted the formation of inner rims on Ti(C, N) cores and hindered their coalescence, leading to well-distributed microstructure. Binder had little effect on the composition of rims, but greatly affected the interface structure of core-rim and rim-binder. Complete inner rim could decrease the lattice mismatch between outer rim and core, forming highly coherent interface. With increasing the Ti-C in Ni, the rim-binder boundaries evolved from semi-coherent to coherent interface, due to the decreased lattice mismatch. Small difference in Vickers hardness of cermets was found, with the values ranging from 1622 to 1684 N/mm2. Bending strength of cermets increased from 1330 to 2073 MPa, with the Ti-C content from 0 to 20 wt%. Further increasing the Ti-C could lead to thick rims, resulting in decreased strength and toughness. This work showed us a way to strengthen the Ti(C, N)-based cermets via modifying the interface structure.

© 2019 IEEE. In this letter, an ultralow phase-noise differential oscillator is proposed using a balanced feedback filter based on quarter stepped-impedance resonators (QSIRs). Phase-noise performance of the designed oscillators can be significantly improved by taking advantage of high peak group delay, improved stopband suppression, and differential configuration of the proposed feedback filter. To verify the hypothesis and compare the phase-noise performance among single-ended and differential oscillators, both the prototypes are designed, fabricated, and measured. The measured results show that the designed single-ended and differential oscillators are operating at 1.953 GHz. The differential oscillator shows not only a good balanced output power of 8.29 dBm with a measured high suppression of 40.07 dB on the second harmonic but also a superior low phase-noise performance of −130.19 dBc/Hz at a frequency offset of 100 kHz. To the best of our knowledge, this is the best phase-noise performance among the state-of-the-art works designed on planar hybrid integrated circuits at a similar frequency range.

Evolution for the dynamic recrystallization (DRX) volume fraction of Ti-5Al-5Mo-5V-3Cr-1Zr near β titanium alloy during hot deformation was characterized by using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation. To determine the equation parameters, a series of thermal simulation experiments at the temperature of 1023–1098 K and strain rate of 0.001–1 s‒1 to the true strain of 0.7 were conducted to obtain the essential data about stress σ and strain ε. By further transforming the relationship of σ versus ε into the relationship of strain hardening rate dσ/dε versus σ, two characteristic strains at the beginning of DRX (critical strain εc) and at the peak stress (peak strain εp) were identified from the dσ/dε-σ curves. Sequentially, the parameters in the JMAK equation were determined from the linear fitting of the different relationships among critical strain εc, peak strain εp and deformation conditions (including temperature T, strain rate $\dot \varepsilon $ and strain ε). The as-obtained JMAK equation was expressed as XDRX=1-exp[-0.0053((ε-εc)/εc)2.1], where εc=0.6053εp and εp=0.0031$\dot \varepsilon $0.0081exp(28,781/RT). Finally, the JMAK equation was implanted into finite element program to simulate the hot compression of thermal simulation experiments. The simulation predictions and experimental results about the DRX volume fraction distribution showed a good consistency.

Ti(C, N)-based cermets with different carbon content were prepared by vacuum sintering and gas pressure sintering (Ar, 20 MPa). Effects of carbon content and sintering method on the microstructure, composition and mechanical properties of cermets were studied. Results showed average grain size and thickness of rim phase to increase with higher carbon or by gas pressure sintering, which was caused by the accelerated dissolution-precipitation process. More uniform morphology with broadened grain size distribution was obtained by gas pressure sintering, leading to improved density and properties. Cermets with 0.8 wt%C showed the best mechanical properties, i.e. 2105 MPa (TRS), 10.55 MPa m 1/2 (K IC ), and 1581 (H V 10), although containing residue Ni 2 (W, Ti) 4 C. Further increasing the carbon addition leads to thick rims and high amount of white core-grey rim phases, which can deteriorate the properties. Adequate control of size and composition of the core-rim structure plays a key role in ensuring satisfactory mechanical properties.

Toughening of (Ti, W)C-based cermets is one of the most important field to expand their application in cutting, Wear-resistant materials and equipment used in harsh environment. Modifying the morphology and composition of the ceramic grains is a highly effective measure. Here, we demonstrate a promising cermet toughened by in-situ formed WC or twinned (Ti, W)C platelets with large size around 5–8 μm. A new method is established by carbonization of synthesized η phases, via sintering of the high-energy crushed Ti W Ni C powders. Results showed that higher Ni/C ratio and temperature could boost the carbonization process, resulting in more Ni6(W1-x, Tix)6C. Only when Ni/C ratio was higher than 1.0, could WC platelets appeared in the cermets. TiC doped WC platelets with no planar defect began to be precipitated at a low temperature by two-dimension growth, along with the formation of fine spherical (Ti, W)C particles. Plate-like twinned (Ti, W)C was only formed by carbonization of Ni2(W1-y, Tiy)4C above 1200 °C, through the twin-assisted growth along {111} planes at a low supersaturation. Platelets could enhance the strength and toughness with slightly decreased hardness, via crack deflection and platelet pull out mechanisms. Compared to the conventional cermets, (Ti, W)C Ni with high fracture toughness (15.80 MPa mm1/2), satisfactory strength (1885 MPa) and hardness (88.3 HRA) were achieved. This work provided not only a new method for preparing the (Ti, W)C Ni cermets, but also a new insight to modify the final microstructure with controlled properties.

In this letter, a constantly low-phase-noise voltage-controlled oscillator (VCO) with wide frequency tuning range (FTR) (44.4%) is presented. The presented VCO is based on a four-pole tunable bandpass filter (BPF) with quasi-elliptic frequency response and constant absolute bandwidth (CABW). Because the four-pole quasi-elliptic BPF is used, the low phase noise of the VCO is obtained, and because the CABW of the filter is kept within a wide FTR, the low phase noise is maintained over the wide FTR. Based on this concept, a demonstrative VCO is designed and measured. The oscillation frequency of the demonstrative VCO is able to be tuned from 1.35 to 2.12 GHz (44.4%) and the phase noise keeps better than −101.3 dBc/Hz at 100 kHz and −127.8 dBc/Hz at 1 MHz over the FTR.

The evolution of deformation microstructure in electron beam melted Ta-2.5W alloy was investigated. The morphology of microbands appear different in different reduction levels. The microbands are relatively straight at low to medium strain and can cross the grain boundary. They become wavy when the reduction reaches 70%. The microbands are parallel with rolling direction when the reduction is up to 90%. The average inclination angles between microbands and rolling direction is about 35° at 20% reduction and get smaller and smaller with increasing strain. EPBs are developed when the reduction is 20%. Most of grains contain one or two groups of EPBs occupying almost the whole grain interiors when the reduction is larger than 30%. The EPBs are fragmented, diffused and curved in the early stages of development. When the reduction reaches 40%, the EPBs become more well-developed and homogeneous. The dislocations within EPBs tend to rearrange themselves with increasing strain in a sequence, from tangled dislocations, followed by parallel dislocations and finally into dislocation nets. The evolution of microbands is related with both the cross-slip of dislocations and the splitting of high dense dislocation walls.

A tunable terahertz (THz) narrowband absorber in view of bulk Dirac semimetal (BDS) is designed in this paper. The tunable terahertz absorber's basic unit comprises BDS, intermediate medium, and metal substrate. The BDS has good surface conductivity and the Fermi energy of that is flexible tunable, and the good surface conductivity might make controlled by Fermi energy. The absorption characteristics of the designed absorber are simulated by the finite integral time domain technique. The calculation results show that the designed absorber achieves ideal absorption in 139.97 μm, 163.52 μm, 247.76 μm bands, and the absorption rate is more than 0.96, which realizes ideal narrowband absorption and dynamic tuning. We find that the absorption peaks are flexible and adjustable by changing the Fermi energy of BDS, and the frequency adjustability of the absorber is analyzed. In addition, the effects of different structural parameters on the absorption efficiency and the absorption performance at different incident angles are studied. These results show that, compared with traditional metamaterials, Dirac semimetallic absorbing materials can tune the resonant frequency more effectively, even without reconstructing the structure, which has great application value in many fields, and provide a new reference for future research.

High-energy ball-milling and annealing processes greatly affect the grain size, composition and microstrain of the TiC powders, which play a key role in determining the final microstructure and properties of TiC-based cermets. In this work, TiC-25WC-11Mo 2 C-18(Ni-Co) cermets were fabricated with four types of TiC powders: microsized (raw), nanosized (milled) and submicron (heated in vacuum at 1350 or 1450 ℃). Effects of crushing and subsequent heat treatments on the composition and structure of TiC powders were investigated. Morphology and mechanical properties of the cermets were also studied. Annealing decreased the microstrain and oxygen content of the milled TiC, forming submicro particles with high crystallinity. Activated particles accelerated the dissolution-precipitation process and interface reaction of the core-rim phases, leading to thick rims on small TiC cores. Chemical bonded oxygen in TiC grains could only be consumed via full interface reaction of the core-rim structure, leaving small pores in ceramic grains. Spherical TiC grains with uniform and integrated inner rims were observed in samples with annealed powders. Ultrafine TiC-based cermets with high strength (1862 MPa), hardness (92.1 HRA) and satisfied toughness (11.32 MPa mm 1/2 ) were achieved using these annealed submicron TiC powders.

The TiN–WC–Ni–Co system cermets with nearly full density were successfully fabricated by conventional vacuum sintering with the addition of WC. Effect of WC addition on the microstructure and mechanical properties of TiN-based cermets was studied in this work. The results showed that WC helped to improve the wettability significantly between TiN and Ni/Co through the formation of typical core-rim structure, which is rather beneficial to obtain the cermets with full densification and homogeneous microstructure. As the addition of WC content increased from 0 wt% to 25 wt%, the microstructure had a marked trend to become denser and finer and the mechanical properties of the TiN-based cermets were enhanced greatly. When the WC content was 20 wt%, the relative density, transverse rupture strength, fracture toughness and Rockwell hardness of the cermets reached 99.5%, 1235 MPa, 12.6 MPa m 1/2 and 88.2, respectively.

In this paper, the influence of TiC addition on the microstructure and mechanical properties of TiN-based cermets fabricated through the powder metallurgical method was systematically investigated by scanning electron microscopy, X-ray diffraction and mechanical tests. The results showed that the TiC content had a significant effect on the microstructure evolution and mechanical properties of TiN-based cermets. When the added TiC content increased from 0 to 20 wt%, the transverse rupture strength, relative density and fracture toughness increased initially, exhibited a maximum and then decreased, while the hardness increased monotonically. As the TiC content was 10 wt%, the transverse rupture strength, relative density, fracture toughness and Rockwell hardness of TiN-based reached up to 2223 MPa, 99.87%, 15.7 MPa m1/2 and 88.7 HRA, respectively.

In this study, TiCN-based cermets with duel grain structure were prepared by long time milling of the microsized raw powders. The effects of coarse TiCN content on the microstructure and mechanical properties of ultrafine TiCN-based cermets were investigated. Results showed that the addition of coarse TiCN powders in ultrafine composite mixture could increase the compact density, but also resulted in increased closed pores in cermets. Coarse TiCN particles would accelerate the dissolution and precipitation reaction of the fine powders, forming more bright cores or thick inner rims on the fine TiCN grains. Grain size of the cermets gradually increased with higher coarse TiCN content. When the coarse content was more than 30%, abnormal growth of TiCN grains occurred via the coalescence of TiCN particles. Mechanical properties of the cermets were firstly increased within 10 or 20% coarse TiCN, then decreased sharply with further increasing the coarse powders. Highest strength (1940 MPa) and toughness (11.67 MPa·m 1/2 ) were achieved with 10% coarse TiCN. Coarse ceramic grains with thick rims exhibit brittleness, deteriorating the final properties of the cermets.

The evolution of dislocation microstructure in electron beam melted Ta-2.5W alloy was investigated by transmission electron microscope (TEM). Long straight dislocations and dislocation loops are formed in Ta-2.5W alloy cold-rolled by 5%. A set of long, continuous extending planar boundaries (EPBs) are formed when the reduction reaches 20%. In the early stage of development, EPBs are fragmented, diffused and curved, which are connected by non-crystallographic cells boundaries to maintain their continuity. The straight segments of EPBs are usually parallel with the trace of {110}, and incline at about 25–35° to the rolling direction (RD). Two groups of EPBs are formed in a grain when the reduction is larger than 30%. The dislocations within EPBs tend to rearrange themselves with increasing strain in a sequence, from tangled dislocations, followed by parallel long straight screw dislocations and finally into dislocation nets, which a re composed by 1/2 and [100] type dislocations. The relaxation process of dislocations and the interaction of dislocations with EPBs make EPBs appear wavy and deviate from the trace of slip planes.

Porous spherical In(OH)3 particles with controllable size were hydrothermally synthesized from aqueous In(NO3)3 solution with the help of urea and citric acid. The average size of the synthesized In(OH)3 particles decreased with the increase of the molar ratio between citric acid and In3 + concentration. Cubic In2O3 phase was obtained after a hydrothermal process at 160 °C and a calcination process at 600 °C, while mixed rhombohedral and cubic In2O3 phases were obtained by annealing the hydrothermally synthesized precursor at 180 °C. Morphology, internal structure, particle size distribution and specific surface area of the In2O3 particles were characterized. A possible mechanism was proposed to illustrate the growth of In2O3 particles. The gas sensors which prepared with porous cubic In2O3 materials displayed high sensitivity to formaldehyde.

© 2019 IEEE. This paper presents a low phase noise differential oscillator by employing a balanced feedback bandpass filter (BPF) designed with the proposed stub-loaded nested split-ring resonator (SLNSRR). The proposed balanced BPF functions as a frequency stabilization element in its feedback loop. Taking advantage of the balanced structure, a high group delay is obtained by introducing a transition zero near the upper passband of feedback loop filter. The proposed differential oscillator can present a differential output with low phase noise performance. For proof of the concept, a 2 GHz differential oscillator has been designed, fabricated and measured. The measured results show that the 180o out-of-phase differential signals are obtained with almost the same peak-peak voltage among two channels. The output power is 9.18 dBm when oscillates at 2.004 GHz with the second harmonic suppression of 40.63 dB. The measured phase noise is -126.72 dBc/Hz at 100 kHz frequency offset. The figure-of-merit (FOM) at 100 kHz is -196.19 dBc/Hz. The phase noise performance of proposed differential oscillator is one of the best among open literatures.

In this letter, a three-pole frequency-agile bandpass filter (FA-BPF) with three transmission zeros (TZs) is presented. Based on the element variable coupling matrix (EVCM), the FA-BPF consists of two varactor-loaded quarter-wavelength resonators and one half-wave length resonator with varactors loaded at the specific position from the shorted-end. By adjusting the stub length from loading position to the shorted-end and the specific coupling length between resonators, the required coupling coefficients can be obtained for the FA-BPF with constant absolute bandwidth (CABW) and predefined frequency tuning range (FTR). To improve the frequency selectivity of the FA-BPF, the cross-coupling is realized for the topology of the filter, and thus a transmission zero (TZ) appears on the edge of passband. Besides, the source-load coupling is also introduced to generate two TZs to enhance the stopband rejection level. For demonstration, the FA-BPF is designed, fabricated and measured. The measurement results show that a great agreement with simulation results based on the proposed method.

WC-TiC-Co composite powders with fine WC grains and homogeneously distributed Co and inhibitors were prepared via a two-step carburization method. η phase powders were synthesized via the carburization of the crushed mixture of W, Co, C and TiC; WC-TiC-Co composite powders were then fabricated by the carburization of the η phase powders. The effects of TiC on the carburization process and the microstructure of composite powders, sinter and mechanical properties of WC-TiC-Co cemented carbides were investigated. Co2W4C type η phase powders were confirmed via the first carburization at 1150 °C for 2 h, which were further carburized into WC-TiC-Co composite powders at 1100 °C for 1 h under the flowing hydrogen. During the carburization of η phase powders, TiC accelerated the nucleation of WC through a heterogeneous nucleation mechanism, and effectively inhibited the intrinsic grain growth, which both led to fine and non-equilibrium WC grains with a near-sphere shape. Dense WC-(Ti,W)C-Co was confirmed via low-temperature vacuum sintering of the as-synthesized composite powders, owing to the homogeneously dispersed Co and (Ti, W)C grains. This work showed a way to fabricate micro-homogeneous composite powders of cemented carbides via carburization of the η phase powders.

The Finite Difference Time Domain (FDTD) method is used for the simulation, and a new method based on critical coupling and guided resonance is proposed theoretically and numerically to realize a multi-band ideal absorber (PA) of monolayer graphene. Its physical mechanism can be more perfectly analyzed through impedance matching and coupled mode theory (CMT). Due to the guided resonance (100% transmission or reflection efficiency is obtained through the coupling of the leakage mode and the guided mode under the phase matching condition), the perfect absorber can obtain four perfect absorption peaks. The resonance wavelengths are located at λ1 = 1085.03 nm, λ2 = 1131.48 nm, λ3 = 1187 nm and λ4 = 1365.35 nm, respectively. Their absorption rates are 95.88%, 99.81%, 97.44% and 95.30%. At the same time, we can also see a phenomenon in which the spectral position and value of the absorption peak can be adjusted by changing the relevant geometric parameters in the system (the geometric size, period, and incident angle of the hexagonal air hole absorber). Meanwhile, the structure we designed has certain advantages in the field of similar absorber research by briefly calculating related values of sensing performance. The sensitivity of its four resonance peaks are 46.45, 94.35, 151 and 598.9 nm/RIU, and FOM are 5.445, 11.192, 19.895 and 85.680. So we believe that the research has huge application prospects in terms of sensors, tunable spectrum detection, environmental monitoring and medical diagnosis, modulators and optoelectronic device sensors.

A new gelling system based on the polymerization of hydantion epoxy resin and 3,3′-Diaminodipropylamine (DPTA) was successfully developed for fabricating silicon nitride (Si3N4) ceramics. The effects of pH value, the dispersant content, solid volume fraction and hydantion epoxy resin amount on the rheological properties of the Si3N4 slurries were investigated. The relative density of green body obtained from the solid loading of 52 vol% Si3N4 slurry reached up to 62.7%. As the concentration of hydantion epoxy resin increased from 5 wt% to 20 wt%, the flexural strength of Si3N4 green body enhanced from 5.3 MPa to 31.6 MPa. After pressureless sintering at 1780 °C for 80 min, the sintered samples exhibited the unique interlocking microstructure of elongated β-Si3N4 grains, which was beneficial to improve the mechanical properties of Si3N4 ceramics. The relative density, flexural strength and fracture toughness of Si3N4 ceramics reached 97.8%, 687 MPa and 6.5 MPa m1/2, respectively.

The effect of grain size on the texture and deformation microstructure of cold-rolled Ta-2.5W alloy has been investigated. The alloy with fine grains has higher microhardness than that with coarse grains under the same cold-rolling conditions. Microbands are developed when the cold-rolled reduction reach 20% and the density of microbands increases with increasing reduction. The boundaries of microbands consist of cross dislocation network when cold-rolled by 40%. Meanwhile, mature α and γ fibers are developed in these two alloys. Compared the alloy with coarse grains, the alloy with fine grains has a stronger texture intensity of γ fiber, which is mainly composed of microbands. Meanwhile, the average space between boundaries of microbands is smaller than that in alloy with coarse grains. The effect of subgrain strengthening and texture strengthening in fine-grain alloy is greater than those in coarse-grain alloy.