- 标题
- 摘要
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- 实验方案
- 产品
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In-situ synthesis of mullite-SiCw composite ceramics in Li2O-Al2O3-SiO2 ternary system for solar heat transmission pipeline
摘要： Nano-SiC whiskers (nano-SiCw) were in-situ synthesized in Li2O-Al2O3-SiO2 ternary system for preparing highly densified mullite-SiCw composite ceramics used for solar heat transmission pipeline. Mechanisms on the in-situ synthesis of nano-SiCw in the ternary system were investigated and the impact of nano-SiCw on the performances of the composites had been studied. Results showed that the growth processes of nano-SiC whiskers in Li2O-Al2O3-SiO2 ternary system were dominated by liquid-solid (LS) mechanism and the Li2CO3 additive could improve the SiCw yield through increasing the content of liquid phase and lowering the liquid viscosity. Sample BS3 (with 2.22 wt% Li2CO3 additive) sintered at 1440 °C obtained the highest SiC content of 47.9%. Nano-SiC whiskers with a diameter of 20e30 nm were interlocking with rod-like mullite crystals to improve the mechanical properties of the composites, and sample BS1 sintered at 1420 °C showed the highest bending strength of 115.4 MPa. The in-situ synthesized SiCw also shew significant effects on improving the thermophysical properties of the composites and sample BS1 exhibited a 3.6 times higher thermal conductivity than that of blank sample B1 without the introduction of nano-SiCw.
关键词： Li2O-Al2O3-SiO2 ternary system,Thermal conductivity,Mullite-SiCw composite ceramics,Solar heat transmission pipeline,SiC whiskers
更新于2025-09-23 15:23:52
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Distributed Small-signal Equivalent Circuit Model and Parameter Extraction for SiGe HBT
摘要： In this paper, we present an improved high frequency small-signal distributed model for SiGe HBTs under forward-active mode based on the transmission line theory. The distributed nature of the transistor structure is taken into account in the proposed model. The single SiGe HBT is considered to be a cascade of many infinitesimal transistors, connected with the intrinsic base resistance. The closed-form solutions of admittance parameters for the distributed model are derived by solving the transmission line equation. With reasonable approximation and simplification, the model parameters are then directly extracted based on the nonlinear rational function fitting. The new improved distributed model and parameter extraction technique are validated with a 1×1.2×30 μm2 SiGe HBT from 100 MHz to 20.89 GHz. The simulated S-parameters in the proposed transmission line model are in close agreement with the measured data, and the frequency characteristics of the transistors are well predicted.
关键词： parameter extraction,rational function fitting,transmission line,SiGe HBT,Device modeling,small-signal model
更新于2025-09-23 15:23:52
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Spin-Selective Transmission in Chiral Folded Metasurfaces
摘要： Controlling the spin angular momentum of light (or circular polarization state) plays a crucial role in the modern photonic applications such as optical communication, circular dichroism spectroscopy, and quantum information processing. However, the conventional approaches to manipulate the spin of light require naturally occurring chiral or birefringent materials of bulky sizes due to the weak light-matter interactions. Here we experimentally demonstrate an approach to implement spin-selective transmission in the infrared region based on chiral folded metasurfaces that are capable of transmitting one spin state of light while largely prohibiting the other. Due to the intrinsic chirality of the folded metasurface, a remarkable circular dichroism as large as 0.7 with the maximum transmittance exceeding 92% is experimentally demonstrated. The giant circular dichroism is interpreted within the framework of charge-current multipole expansion. Moreover, the intrinsic chirality can be readily controlled by manipulating the folding angle of the metasurface with respect to the cardinal plane. Benefiting from its strong chirality and spin-dependent transmission characteristics, the proposed folded metasurface may be applied to a range of novel photon-spin selective devices for optical communication technologies and bio-photonics.
关键词： sub-wavelength optics,Folded metasurface,intrinsic chirality,spin-selective transmission
更新于2025-09-23 15:23:52
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Uncertainty analysis for ac–dc difference measurements with the AC Josephson voltage standard
摘要： A detailed analysis of the uncertainties obtained in ac–dc difference measurements with an AC Josephson voltage standard (ACJVS) is presented. For audio frequencies and for voltages less than 200 mV, ac–dc transfers with the ACJVS may reduce the combined uncertainty by factors of 2–10, compared with conventional methods based on thermal converters. Type A uncertainties are predominantly limited by the thermal transfer standard (TTS), or the digital voltmeter used to acquire the output voltage from the TTS. In agreement with earlier work, the transmission line is the primary contributor to Type B errors for frequencies above 10 kHz. A Monte Carlo sensitivity analysis is used to demonstrate how the uncertainties of transmission line impedance and on-chip inductance impact the accuracy of the rms amplitude conveyed to the TTS.
关键词： ac voltage metrology,transmission line analysis,Josephson junction arrays,quantum voltage standards,uncertainty analysis
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Wide-Angle Frequent Scanning Metamaterial Leaky Wave Antenna Array for Automotive Radars
摘要： This paper designs a wide-angle frequency scanning metamaterial (MTM) leaky wave antenna (LWA) array for automotive radars. The gap capacitors and the vialess open stub-loaded resonators are used to construct the frequency scanning MTM LWA array. The propagation constant of the MTM LWA array is able to change from negative to positive values as the frequency is increased, resulting in backward to forward beam scanning. Compared to mechanical beam scanning arrays and phased arrays, the frequency scanning MTM LWA arrays have advantages of reducing the system complexity, light weight and low cost. The presented MTM LWA array has a maximum gain of 13 dB and wide scanning angle from -60° to +80° as the frequency varies from 23.5 to 25.6 GHz which is well suited for automotive radar applications.
关键词： frequency scanning antenna,composite right/left-handed transmission line,Antenna array,metamaterial,leaky wave antenna
更新于2025-09-23 15:22:29
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Compact Wideband Reflective/Absorptive Bandstop Filter With Multitransmission Zeros
摘要： Novel wideband re?ective bandstop ?lters (RBSFs) and absorptive bandstop ?lters (ABSFs) with high stopband rejection (SR) and good frequency selectivity are proposed. Based on a coupled line (CL) with an open-circuited stub, a broad stopband response with three transmission zeros (TZs) is implemented in a compact circuit con?guration. Two modi?ed CL structures are loaded at the ports resulting in two additional TZs. In addition, a grounded resistor is introduced to absorb unwanted signals in the stopband. For demonstration, the ?ve-zero RBSFs and three-zero ABSFs operating at 2 GHz are designed and built. The re?ective ?lter shows a 35-dB SR with 79.5% relative bandwidth (RB). The absorptive ?lter with 69.5% RB of 24-dB SR achieves an all-passband 12.2-dB return loss. Good agreements between simulated and measured results are observed.
关键词： Compact,transmission zeros (TZs),wideband,re?ective bandstop ?lters (RBSFs) and absorptive bandstop ?lters (ABSFs),coupled line (CL)
更新于2025-09-23 15:22:29
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System Design for High-Capacity Unrepeatered Optical Transmission
摘要： By basing the figure of merit on the joint evaluation of signal BER and OSNR, the design of single-carrier 400G unrepeatered optical systems using remote optically-pumped amplifiers (ROPAs) with dedicated delivery fiber is discussed and analyzed in this work. Simulation results show very good agreement with experimental measurements, proving the effectiveness of the proposed approach in critical transmission situations.
关键词： remote optically-pumped amplifier (ROPA),distributed Raman amplifier (DRA),optical system design,Unrepeatered coherent transmission
更新于2025-09-23 15:22:29
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DESIGN OF DUAL- AND QUAD-BAND E-CRLH-TLS WITH ARBITRARY PHASE CHARACTERISTICS
摘要： In this paper, extended composite right/left-handed (E-CRLH) transmission line (TL) metamaterial structures, with two left-handed (backward) and two right-handed (forward) pass bands, are investigated. Also, design procedures in order to design dual- and quad-band E-CRLH-TLs are presented in detail and the parameters of these structures are extracted by clean formulas, while satisfying arbitrary phase shifts at the operating frequencies. Finally, the dispersion and characteristic impedances of these transmission lines are derived and plotted. The results of this paper can be applied to any type of TL-based dual- and quad-band microwave component.
关键词： microwave component,metamaterial,phase shift,dual-band,E-CRLH,quad-band,transmission line
更新于2025-09-23 15:22:29
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Light Transmission of Glasses Synthesized on the Basis of Quartz Sand of Different Deposits
摘要： Container and sheet glass are synthesized from various batches with the equivalent addition of complexing decolorizers. The effect of ceria and potassium nitrate on the light transmission coefficient is investigated. Measurement of optical characteristics of the glasses shows that light transmittance increases up to 90–93% (λ = 500–750 nm). It is determined that an increase in the concentration of ceria and potassium nitrate up to particular values in the case of each composition results in the increase in hydrolytic stability, TLCE, and the light transmission coefficient.
关键词： discoloration,iron oxide,light transmission coefficient,chemical stability,quartz sand,synthesis of glass,raw materials
更新于2025-09-23 15:22:29
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Implications of Distributed Link Polarization Dependent Loss on Bit-Wise Achievable Information Rates for Probabilistically Shaped and Uniform DP 64-QAM
摘要： The statistical behaviours of bit-wise achievable information rates (BW AIRs) and effective signal-to-noise ratios (SNRs) due to polarization dependent loss (PDL) are experimentally characterized for probabilistically shaped and uniform dual-polarization 64-ary quadrature amplitude modulation (DP 64-QAM) with a bit rate of 250 Gb/s. A single-span recirculating loop is used to emulate distributed link PDL. Histograms for the BW AIR and effective SNR following offline signal processing resemble shifted, mirror-image Maxwell probability density functions for both constellations and two different per-loop PDL values. For a transmission distance of 1200 km and a per-loop PDL of 1.3 dB, the outage probabilities for the shaped and uniform constellations are estimated to be 1.1 × 10?3 and 4.4 × 10?1, respectively. Moreover, for an outage probability ≤ 4.0 × 10?3, the increase in transmission distance due to shaping is reduced by 50% compared to that for PDL free transmission.
关键词： Probabilistic shaping,coherent optical fiber transmission systems,polarization dependent loss
更新于2025-09-23 15:22:29