Adaptive switching mean filter using conditional morphological noise detector

The adaptive switching mean (ASM) filter is proposed to remove impulse noise. The filter first identifies the corrupted pixels using conditional morphological noise detection and then removes the detected impulses using the adaptive mean filter. Simulation results indicate that the ASM filter can suppress impulse noise effectively while preserving the details in the image very well, thus providing better restoration performance than many other switching-based filters.     

Study and formation of 2D microstructures of sapphire by focused ion beam milling

Dry etching of C-plane sapphire wafer has been studied using Ga⁺ focused ion beam milling (FIBM). Due to a much lower milling rate of sapphire compared to GaN, it has been proven that gas-assisted FIBM (GAFIBM) is a necessity. Furthermore, it needs to be determined whether XeF₂- or I₂-GAFIBM can improve the technique. We found that XeF₂-GAFIBM gave the highest milling rate. The obtained enhancement factor of the XeF₂-GAFIBM milling rate compared to FIBM rate varied from 2.3 to 1.2 for the ion beam current in the range 20 pA-1 nA. A favorable milling rate selectivity of sapphire to nickel film of about 1.5 was obtained by XeF₂-GAFIBM at 350 pA. We have successfully fabricated a variety of 2D sapphire-based submicron pillar or hole arrays in regular crystals, quasicrystals and aperiodic symmetries. The nearest neighbor distance was down to 230 nm. The depth achieved was deeper than 400 nm. The air filling factor ranged from 12% to 60%. These sapphire-based 2D microstructures were applied on flip-chip GaN-based light emitting diodes (LEDs) and more than 40% improvement in light extraction was obtained.     

Evanescent-Coupled Ge p-i-n Photodetectors on Si-Waveguide With SEG-Ge and Comparative Study of Lateral and Vertical p-i-n Configurations

Si-waveguide-integrated lateral Ge p-i-n photodetectors using novel Si/SiGe buffer and two-step Ge-process are demonstrated for the first time. Comparative analysis between lateral Ge p-i-n and vertical p-Si/i-Ge/n-Ge p-i-n is made. Light is evanescently coupled from Si waveguide to the overlaying Ge- detector, achieving high responsivity of 1.16 A/W at 1550 nm with f_{3 dB} bandwidth of 3.4 GHz for lateral Ge p-i-n detector at 5 V reverse bias. In contrast, vertical p-Si/i-Ge/n-Ge p-i-n has lower responsivity of 0.29 A/W but higher bandwidth of 5.5 GHz at -5 V bias. The higher responsivity of lateral p-i-n detectors is attributed to smaller optical mode overlap with highly doped Ge region as in vertical p-i-n configuration.     

卫星地球站上行系统测试

根据<卫星广播电视地球站工程技术验收规定>和<验收测试方案>的技术要求,结合广东卫星地球站的具体情况,讨论数字压缩DVB-S标准的卫星上行系统信源编码后的指标测试,不包括MPEG-2编码器的码流分析、系统视音频指标等项目的测试.     

Syntheses,Characterization, and Fluorescence Properties of Four Divalent Lead Coordination Polymers based on Zwitterionic Ligands

Four novel divalent lead coordination polymers based on a series of zwitterionic ligands, Pb₂Cl₄L₁ ( 1 ), [Pb₂Cl₄L₂]·2H₂O ( 2 ), Pb₂Cl₂(CH₃COO)₂L₂ ( 3 ), and Pb₃Cl₄(NO₃)₂L₃ ( 4 ) were solvothermally synthesized and successfully characterized. Single crystal structure studies reveal that compound 1 is a chain structure based on the inorganic “PbCl₂” chain motif, whereas compounds 2 – 4 are sheet structures each constructed by inorganic “PbCl₂”, “PbCl(CH₃COO)”, and “Pb₃Cl₄” chain motifs. Hydrogen bonding interactions in term of C–H ··· Cl and C–H ··· O play a key role to form supramolecular 3D structures of 1 – 4 . Additionally, studies of solid state fluorescence indicate 1 – 4 emit in the ultraviolet and visible region that can be assigned to the inter‐ligand π*–π and/or π*–n transitions.     

Guiding Uniform Li Plating/Stripping through Lithium–Aluminum Alloying Medium for Long‐Life Li Metal Batteries

The uncontrolled growth of Li dendrites upon cycling might result in low coulombic efficiency and severe safety hazards. Herein, a lithiophilic binary lithium–aluminum alloy layer, which was generated through an in situ electrochemical process, was utilized to guide the uniform metallic Li nucleation and growth, free from the formation of dendrites. Moreover, the formed LiAl alloy layer can function as a Li reservoir to compensate the irreversible Li loss, enabling long‐term stability. The protected Li electrode shows superior cycling over 1700 h in a Li|Li symmetric cell.     

Dopant‐Free Squaraine‐Based Polymeric Hole‐Transporting Materials with Comprehensive Passivation Effects for Efficient All‐Inorganic Perovskite Solar Cells

Development of high‐performance dopant‐free hole‐transporting materials (HTMs) with comprehensive passivation effects is highly desirable for all‐inorganic perovskite solar cells (PVSCs). Squaraines (SQs) could be a candidate for dopant‐free HTMs as they are natural passivators for perovskites. One major limitation of SQs is their relatively low hole mobility. Herein we demonstrate that polymerizing SQs into pseudo two dimensional (2D) p–π conjugated polymers could overcome this problem. By rationally using N,N‐diarylanilinosquaraines as the comonomers, the resulting polysquaraine HTMs not only exhibit suitable energy levels and efficient passivation effects, but also achieve very high hole mobility close to 0.01 cm^?2 V^?1 s^?1. Thus as dopant‐free HTMs for α‐CsPbI₂Br‐based all‐inorganic PVSCs, the best PCE reached is 15.5 %, outperforming those of the doped‐Spiro‐OMeTAD (14.4 %) based control devices and among the best for all‐inorganic PVSCs.     

Impact of neutral and acidic species on cycloalkenes nucleation

Non-covalent hydrogen bond interactions between the π cloud of cycloalkenes and three atmospheric common nucleation precursors (H₂S, H₂O, and MeOH) have been investigated using DFT and CCSD(T). The structures and the energies of the 1:1 and 1:2 adducts were computed with the B3LYP-D3 method. The analysis of the investigated electronic properties and geometric parameters shows that cyclohexene is a stronger hydrogen bond acceptor than cyclopentene, then followed by 1,4-cyclohexadiene and 1,3-cyclohexadiene. Comparable red shifts of the OH-/SH-stretching vibrational frequencies were noticed for the studied clusters. Increasing the ring size enhances the hydrogen bond interaction, and increasing the π delocalization decreases the hydrogen bond interactions. This is further confirmed by Bader’s quantum theory of atoms in molecules. The nonadditivity effects were observed in the trimolecular complexes. All the complexes were analyzed by energy decomposition analysis to divide the interaction energy into individual components. Furthermore, the dipole moments and atmospheric implications were also investigated.

     

Synergistic improvement of fire retardancy and mechanical properties of ferrocene‐based polymer in intumescent polypropylene composite

The ferrocene‐based polymer (PDPFDE) accompanied with traditional intumescent flame retardant (IFR) system (ammonium polyphosphate (APP)/pentaerythritol (PER) = 3/1, mass ratio) has been used as additive flame retardant in polypropylene (PP), aiming to lower the total loading amount. The thermal stability and fire retardant properties were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical combustion (UL‐94), and cone calorimetry (CONE). The fire retardant mechanism was studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The results showed that the PP1 with 25 wt% IFR only passed the UL‐94 V‐1 rating, but the PP6 loaded by 0.5 wt% PDPFDE and 22.5 wt% IFR possessed an LOI value of 28.5% and passed the UL‐94 V‐0 rating; the peak heat release rate (pHRR) and total heat release (THR) are decreased by 63% and 43%, respectively, compared with pure PP. In addition, the char residue of PP6 manifested a very compact and smooth surface, indicating a more effective barrier layer. Meanwhile, it was interesting that the addition of PDPFDE evidently improved the impact strength and elongation at break of PP/IFR composites.