Synthesis and Characterization of Naphthalene End-Capped Divinylbenzene for OTFT

An organic field-effect transistor was fabricated based on a thin film of 1,4-bis-(2-naphthalen-2-ylvinyl)benzene (BNDV). The organic semiconductor was deposited via thermal evaporation on a chemically modified silicon dioxide surface. The thermal, optical, electronic, and surface properties of the BNDV compound were investigated by thermogravimetric analysis, differential scanning calorimetry, ultraviolet–visible (UV–vis) absorption, photoluminescence spectroscopies, cyclic voltammetry, x-ray diffraction, and atomic force microscopy. The BNDV had good oxidation stability and exhibited a field-effect performance with a mobility of 0.062 cm²/V s, a subthreshold slope of 0.4 V, and an on/off ratio of 2.45 × 10⁵.     

Photonic quantum ring laser of 3D whispering cave mode

A new whispering cave mode (WCM), a three-dimensional (3D) case of Lord Rayleigh's 2D whispering gallery modes, based upon 3D total internal reflection is presented, where GaAs quantum well (QW) near-vertical microdisk resonators exhibit a strong carrier-photon coupling for the QW carriers located in the Rayleigh band, generating 2D-to-1D carrier phase transitions of photonic quantum ring (PQR). It is a ‘photonic’ quantum corral effect (PQCE), whose simulation work produces a tangled web pattern of imminent recombinant carriers in picoseconds timescale. The PQCE is responsible for the ultralow threshold currents below 300 nA for a single mode GaAs PQR laser, and a prototype GaN PQR laser with a threshold near and below 1 μA.     

Catching resource-devouring worms in next-generation wireless relay systems: two-way relay and full-duplex relay - [topics in radio communications]

In spite of their potential to improve the performance of wireless communication systems, relay-based communication systems face significant challenges, resource wastage. In this article we discuss resource efficiency in relay systems, particularly in two-way and full-duplex relay systems that utilize multiple antennas and improved duplexing to enhance system efficiency. We compare in detail the features, frame structures, performances, advantages and disadvantages, and technical challenges associated with TWRs and FDRs. Using illustrations of quantitative performance, we demonstrate that both of these approaches can efficiently reduce resource wastage in relay-based communication systems.     

Inverted-load network for high-power Doherty amplifier

In this article, a high-power, high-efficiency inverted Doherty power amplifier (PA), having a more compact load network than that of the conventional Doherty amplifier, was designed and implemented for wide-band code-division multiple access (WCDMA) base-station applications. Its configuration and working principle are compared with the conventional Doherty amplifier. For experimental verification, we implemented an inverted Doherty amplifier, using a 190 W peak-envelope-power (PEP) laterally diffused metal-oxide-semiconductor (LDMOS) field-effect transistors (FETs). Using a four-carrier down-link WCDMA signal, we achieved a high power-added efficiency (PAE) of 32% and an average output power level as high as 46.3 dBm at a given adjacent channel leakage ratio (ACLR) level of -30 dBc. This is a 9.5% improvement in efficiency and 1 dB improvement in output power under the same ACLR conditions from those of the balanced class-AB operation using the same devices.     

Size control of Pb-based glass powders between 38 and 84 nm in the flame spray pyrolysis

Nano-sized Pb-based glass powders with different mean size, ranging from 38 to 84 nm were prepared by flame spray pyrolysis. The mean sizes of the glass powders were controlled by changing the concentration of spray solution. The glass powders prepared by flame spray pyrolysis from the spray solutions with different concentration had broad peaks at around 28° in the XRD patterns. The dielectric layers formed from the glass powders with the mean size of 38 nm had dense inner structures at firing temperatures of 480 and 520°C. On the other hand, the dielectric layer formed from the glass powders with the mean size of 84 nm had some voids inside the layer. The transmittances of the dielectric layer formed from the glass powders with the mean sizes of 38 and 84 nm were each 91% and 74% at firing temperature of 480°C.     

Mη对Ps静电纺丝及超细纤维膜拉伸性能的影响

采用乳液聚合制备了不同相对分子质量的聚苯乙烯(PS),研究了相对分子质量对静电纺丝过程和超细纤维膜形态和性能的影响。使用乌氏粘度计测定PS的粘均相对分子质量(Mη),使用高速摄相机观察射流分裂行为,通过扫描电镜,万能拉伸机对制得的PS超细纤维膜形态和力学性能进行分析测试。结果表明:聚合所得不同Mη的PS都具有可纺性,超细纤维形态优良,Mη增大,稳定射流越长,平均直径从0.3μm增至3.0μm。纤维膜断裂强度也随Mη增大而增大。     

对城市建筑群火灾自动报警系统室外联网的探讨

阐述了城市建筑群火灾自动报警系统室外联网几种形式,及具体施工内容和注意事项.     

Sulfonated polyaniline–titanium dioxide nanocomposites synthesized by one-pot UV-curable polymerization method

Sulfonated polyaniline–titanium dioxide (SPAni–TiO₂) hybrid composites have been synthesized by using a new strategy in one-pot system of UV-cured polymerization method. Aqueous solution of aniline and orthoanilinic acid comonomers, a free-radical oxidant and titania precursor were irradiated by UV rays. Hydrolysis and reprecipitation of the titania precursor in aqueous aniline and orthoanilic acid lead to the formation of titanium dioxide particles which in turn catalyze oxidation of comonomers to sulfonated polyaniline. The resultant SPAni–TiO₂ composites were characterized by using different spectroscopy analyses like X-ray diffraction, UV–visible (UV–vis) and infrared spectroscopy. The UV–vis absorption bands revealed that SPAni–TiO₂ nanocomposites are optically active and the blue-shifted peaks due to the presence of titania within the SPAni matrix. Scanning electron microscopy and transmission electron microscopy of the nanocomposite showed a uniform size distribution with spherical and granular morphology. Thermogravimetric analysis revealed that the SPAni–TiO₂ composites have a good thermal stability than the pristine SPAni.     

Combination of hot extrusion and spark plasma sintering for producing carbon nanotube reinforced aluminum matrix composites

Aluminum (Al)/carbon nanotube (CNT) composites with nanoscale dispersion and regular orientation of the CNTs were fabricated by a combination of some advanced powder processes. The CNTs were well dispersed onto the Al particles by a nanoscale dispersion method. Moreover, the highly densified CNT composites were prepared by spark plasma sintering and subsequent hot extrusion. Microstructural observations by optical, field-emission scanning electron, and high-resolution transmission electron microscopies confirmed that the sintered Al/CNT compact and extruded bulk material had a good dispersion of oriented CNTs. Raman spectroscopy showed that the processing did little damage to the CNTs. As a result, the composites exhibited tensile strengths that were thrice larger than pure aluminum because of the CNT reinforcement.     

Electrospun hydrophilic fumed silica/polyacrylonitrile nanofiber-based composite electrolyte membranes

Hydrophilic fumed silica (SiO₂)/polyacrylonitrile (PAN) composite electrolyte membranes were prepared by electrospinning composite solutions of SiO₂ and PAN in N,N-dimethylformamide (DMF). Among electrospinning solutions with various SiO₂ contents, the 12 wt% SiO₂ in PAN solution has highest zeta potential (−40.82 mV), and exhibits the best dispersibility of SiO₂ particles. The resultant 12 wt% SiO₂/PAN nanofiber membrane has the smallest average fiber diameter, highest porosity, and largest specific surface area. In addition, this membrane has a three-dimensional network structure, which is fully interconnected with combined mesopores and macropores because of a good SiO₂ dispersion. Composite electrolyte membranes were prepared by soaking these porous nanofiber membranes in 1 M lithium hexafluorophosphate (LiPF₆) in ethylene carbonate (EC)/dimethyl carbonate (DMC) (1:1 vol%). It is found that 12 wt% SiO₂/PAN electrolyte membrane has the highest conductivity (1.1 × 10⁻² S cm⁻¹) due to the large liquid electrolyte uptake (about 490%). In addition, the electrochemical performance of composite electrolyte membranes is also improved after the introduction of SiO₂. For initial cycle, 12 wt% SiO₂/PAN composite electrolyte membrane delivers the discharge capacity of 139 mAh g⁻¹ as 98% of theoretical value, and still retains a high value of 127 mAh g⁻¹ as 89% at 150th cycle, which is significantly higher that of pure PAN nanofiber-based electrolyte membranes.