Analysis of the modulation mechanisms of the electric field and breakdown performance in AlGaN/GaN HEMT with a T-shaped field-plate

A novel Al Ga N/Ga N high electron mobility transistor(HEMT) with a source-connected T-shaped field-plate(ST-FP HEMT) is proposed for the first time in this paper. The source-connected T-shaped field-plate(ST-FP) is composed of a source-connected field-plate(S-FP) and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP(S-FP HEMT) shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications.     

Kondo-Fano Effect in T-shaped Double Quantum Dots Coupled to Ferromagnetic Leads

Using an equation-of-motion technique,we theoretically study the Kondo-Fano effect in the T-shaped double quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian.We calculate the density of states in this system by solving Green function.Our results reveal that the density of states show some noticeable characteristics not only depending upon the interdot coupling t ab,the energy level ε d1 of the side coupled quantum dot QD b,and the relative angle θ of magnetic moment M,but also the asymmetry parameter α in ferromagnetic leads and so on.All these parameters greatly influence the density of states of the central quantum dot QD a.This system is a possible candidate for spin valve transistors and may have potential applications in the spintronics.     

Fast-response terahertz wave switch based on T-shaped photonic crystal waveguide

We design an ultra-fast terahertz wave switch based on T-shape photonic crystal waveguide. The polymer rod is added in the junction as a point defect, the refractive index of which can be varied by adjusting the external pump laser intensity. The transmission spectrum is calculated by finite-difference time-domain method, which shows that the output energy of the two output ports is closely related to the refractive index of the polymer rod. By continuous wave excitation of the guided mode, the simulation results show that the T-shaped photonic crystal waveguide can flexibly tune the power in two output ports. The tuning rate of the device is about 0.3 ns. These results provide a useful guide and a theoretical basis for the developments of terahertz wave functional components.     

Laser direct patterning of the T-shaped ITO electrode for high-efficiency alternative current plasma display panels

The laser direct patterning technique is one of the new methods of direct etching process to replace the conventional photolithography. In this experiment, a Q-switched diode-pumped Nd:YVO₄ (λ = 1064 nm) laser was used to produce the indium-tin oxide (ITO) patterns with a complex T-shaped structure on glass substrate. The results showed that the overlapping rate of laser beam had a major effect on the quality of the edge of the ITO electrode. When the overlapping rate was about 75%, it was possible to obtain optimum linearity in the edge of patterned ITO electrode. By using the optimum conditions of 75% overlapping rate, 500 mm/s scanning speed, and 40 kHz repetition rate, an alternative current plasma display panels (AC PDPs) with T-shaped ITO electrode was fabricated and characterized. The discharging results showed that the AC PDPs with the laser ablated T-shaped ITO electrode had a better discharging characteristics compared to the conventional sample with wet-etched stripe-type ITO electrode.     

Reaction Pathways and Redox States in α-Selective Cobalt-Catalyzed Hydroborations of Alkynes

Cobalt(II) alkyl complexes supported by a monoanionic NNN pincer ligand are pre-catalysts for the regioselective hydroboration of terminal alkynes, yielding the Markovnikov products with α:β-(E) ratios of up to 97:3. A cobalt(II) hydride and a cobalt(II) vinyl complex appear to determine the main reaction pathway. In a background reaction the highly reactive hydrido species specifically converts to a coordinatively unsaturated cobalt(I) complex which was found to re-enter the main catalytic cycle.     

SYNTHESIS AND CHARACTERIZATION OF LIQUID CRYSTAL POLYMERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNITS (Ⅱ)*

A series of liquid crystalline polymers with T-shaped two-dimensional mesogenic unitswere synthesized via low temperature solution polycondensation of 2-(4'-alkoxy-phenyl)hydroquinone with various diacyl dichlorides. The polymers were found to be nematic andshown thermotropic liquid crystalline behaviors through observations using DSC, polarizedmicroscopy and X-ray diffraction. The melting temperature T_m and the isotropizationtemperature T_i of the polymers change regularly with varying of the monomer structures.     

Synthesis and Photophysical Properties of T-Shaped Coinage-Metal Complexes

The photophysical properties of a series of T-shaped coinage d¹⁰ metal complexes, supported by a bis(mesoionic carbene)carbazolide (CNC) pincer ligand, are explored. The series includes a rare new example of a tridentate T-shaped Ag^I complex. Post-complexation modification of the Au^I complex provides access to a linear cationic Au^I complex following ligand alkylation, or the first example of a cationic square planar Au^III−F complex from electrophilic attack on the metal centre. Emissions ranging from blue (Cu^I) to orange (Ag^I) are obtained, with variable contributions of thermally-dependent fluorescence and phosphorescence to the observed photoluminescence. Green emissions are observed for all three gold complexes (neutral T-shaped Au^I, cationic linear Au^I and square planar cationic Au^III). The higher quantum yield and longer decay lifetime of the linear gold(I) complex are indicative of increased phosphorescence contribution.     

Development of a passive micromixer based on repeated fluid twisting and flattening,and its application to DNA purification

We have developed a three-dimensional passive micromixer based on new mixing principles, fluid twisting and flattening. This micromixer is constructed by repeating two microchannel segments, a “main channel” and a “flattened channel”, which are very different in size and are arranged perpendicularly. At the intersection of these segments the fluid inside the micromixer is twisted and then, in the flattened channel, the diffusion length is greatly reduced, achieving high mixing efficiency. Several types of micromixer were fabricated and the effect of microchannel geometry on mixing performance was evaluated. We also integrated this micromixer with a miniaturized DNA purification device, in which the concentration of the buffer solution could be rapidly changed, to perform DNA purification based on solid-phase extraction.     

SYNTHESIS AND CHARACTERIZATION OF LIQUID CRYSTAL POLYESTERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNITS(Ⅲ)*

A new series of liquid crystal polyesters with T-shaped two-dimensional mesogenic units weresynthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxydibenzoic acid. The polymers were characterized by using polarized microscopy, DSC and X-ray diffraction. It was realized that all the polymers have nematic thermotropic liquid crystallinecharacteristics. The melting temperature (T_m) and isotropization temperature (T_i) of the polymers changeregularly with varying lengths of the alkoxy side group and the length of the alkylene group in the main chainin company with an even-odd effect. The mesophase temperature range also varies regularly with the polymerstructure. It is shown that the mesophase range has been widened.     

带内螺旋翅片的T形翅片管传热特性研究

以钢质光滑管、T形翅片管及带内螺旋翅片的T形翅片管为元件，以氟利昂113—水为介质的单管池沸腾传热试验的结果表明，在试验范围内，带内螺旋翅片的T形翅片管的总传热系数是光滑管的1．9～2．6倍，是T形翅片管的1．21～1.29倍。用Wilson图解分析法得到的这种新管型的管内单相流体给热系数的方程为：hi＝0．0244λ／DiRe(0.8)Pr(0.3)，管外沸腾给热系数的方程为：h0＝5104．3q(0．04)。对试验结果和这种新管型的传热强化机理进行了讨论。