Dynamic behavior of outburst two-phase flow in a coal mine T-shaped roadway:The formation of impact airflow and its disaster-causing effect

The study of the dynamic disaster mechanism of coal and gas outburst two-phase flow is crucial for improving disaster reduction and rescue ability of coal mine outburst accidents.An outburst test in a T-shaped roadway was conducted using a self-developed large-scale outburst dynamic disaster test system.We investigated the release characteristics of main energy sources in coal seam,and obtained the dynamic characteristics of outburst two-phase flow in a roadway.Additionally,we established a formation model for outburst impact flow and a model for its flow in a bifurcated structure.The results indicate that the outburst process exhibits pulse characteristics,and the rapid destruction process of coal seam and the blocking state of gas flow are the main causes of the pulse phenomenon.The outburst energy is released in stages,and the elastic potential energy is released in the vertical direction before the horizontal direction.In a straight roadway,the impact force oscillates along the roadway.With an increase in the solid–gas ratio,the two-phase flow impact force gradually increases,and the disaster range extends from the middle of the roadway to the coal seam.In the area near the coal seam,the disaster caused by the two-phase flow impact is characterized by intermittent recovery.In a bifurcated roadway,the effect of impact airflow on impact dynamic disaster is much higher than that of two-phase flow,and the impact force tends to weaken with increasing solid-gas ratio.The impact force is asymmetrically distributed;it is higher on the left of the bifurcated roadway.With an increase in the solid-gas ratio,the static pressure rapidly decreases,and the bifurcated structure accelerates the attenuation of static pressure.Moreover,secondary acceleration is observed when the shock wave moves along the T-shaped roadway,indicating that the bifurcated structure increases the shock wave velocity.

Influences of fillet radius and draft angle on local loading process of titanium alloy T-shaped components

In order to study influences of geometric parameters on the T-shaped components local loading process, a new mathematical model considering the fillet radius and draft angle was established by using the slab method. The results obtained by the mathematical model agree with the data form experiment and numerical simulation, and the results are closer to the experimental and simulation results. The influence of draft angle may be neglected under the forming conditions used. The influence of fillet radius is notable, especially in the case that the ratio of fillet radius to rib width is less than 0.75.

Performance of a Self-Aligned InP/GaInAs SHBT with a Novel T-Shaped Emitter

A self-aligned InP/GalnAs single heterojunction bipolar transistor（HBT） is investigated using a novel T-shaped emitter. A U-shaped emitter layout,selective wet etching,laterally etched undercut, and an air-bridge are applied in this process. The device, which has a 2μm×12μm U-shaped emitter area,demonstrates a common-emitter DC current gain of 170,an offset voltage of 0.2V,a knee voltage of 0.5V, and an open-base breakdown voltage of over 2V. The HBT exhibits good microwave performance with a current gain cutoff frequency of 85GHz and a maximum oscillation frequency of 72GHz, These results indicate that these InP/InGaAs SHBTs are suitable for low-voltage,low-power,and high-frequency applications.

Improved design of special boundary elements for T-shaped reinforced concrete walls

This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design method. Comparison of the design provisions of the GB 50011-2010 code and those of the American code ACI 318-14 indicates a possible deficiency in the T-shaped wall design provisions in GB 50011-2010. A case study of a typical T-shaped wall designed in accordance with GB 50011-2010 also indicates the insufficient extent of the boundary element at the non-flange end and overly conservative design of the flange end boundary element. Improved designs for special boundary elements ofT-shaped walls are developed using a displacement-based method. The proposed design formulas produce a longer boundary element at the non-flange end and a shorter boundary element at the flange end, relative to those of the GB 50011-2010 provisions. Extensive numerical analysis indicates that T-shaped walls designed using the proposed formulas develop inelastic drift of 0.01 for both cases of the flange in compression and in tension.

Numerical investigation of flow pattern and components of three-dimensional velocity around a submerged T-shaped spur dike in a 90° bend

Spur dike is one of the river training structures. This work presented a numerical simulation of flow field and three-dimensional velocity around a T-shaped spur dike located in bend using SSIIM model. The main objective of this work is to investigate the three-dimensional velocities and streamlines at transverse and longitudinal sections and plan views around the T-shaped spur dike in different submergence ratios(0, 5%, 15%, 25% and 50%). It is concluded that by increasing the submergence ratio from 5% to 50%, the maximum of scour is reduced; the maximum of longitudinal velocity increases by 7.7% and occurs at the water surface in spur dike axis. Near the bed, the maximum of vertical velocity occurs at the end of spur wing. By analyzing the streamlines at transverse sections, the followings were deduced for different submergence ratios: different dimensions and different positions of vortices around the spur dike.

Formation dynamics and size prediction of bubbles for slurry system in T-shape microchannel

The bubble formation dynamics and size manipulation in the slurry of polystyrene microspheres in the microfluidic T-junction were visually investigated by a high-speed camera.Based on the evolution of the bubble neck with time,the formation process of bubbles is divided into three stages:filling,squeezing and pinch-off.The particle concentration has an obvious effect on the squeezing stage,while less impact on the filling and pinch-off stages.In the squeezing stage,the evolution of the dimensionless minimum neck width of bubbles with time could be described by a power-law relationship.The increase of the particle concentration or continuous phase flow rate could lead to the increase of body flow of the continuous phase and the enhancement of the squeezing force acted on the bubble neck,correspondingly,the power-law index a in the squeezing stage enlarges.Moreover,the bubble size increases with the increase of the gas phase flow rate and the decrease of the particle concentration and continuous phase flow rate.However,the effect of the particle concentration on the bubble size weakens with the increase of the continuous phase flow rate.In addition,a new prediction correlation of the bubble size for the slurry system in a T-shape microchannel was proposed with good prediction accuracy.

Static and dynamic responses of a microcantilever with a T-shaped tip mass to an electrostatic actuation

In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The electrostatic force is generated by applying an electric voltage between the horizontal part of T-shaped tip mass and an opposite electrode plate. The cantilever microbeam is modeled as an Euler-Bernoulli beam. The T-shaped tip mass is assumed to be a rigid body and the nonlinear effect of electrostatic force is considered. An equation of motion and its associated boundary conditions are derived by the aid of combining the Hamilton principle and Newton’s method. An exact solution is obtained for static deflection and mode shape of vibration around the static position. The differential equation of nonlinear vibration around the static position is discretized using the Galerkin method. The system mode shapes are used as its related comparison functions. The discretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. In addition, effects of mass inertia, mass moment of inertia as well as rotation of the T-shaped mass, which were ignored in previous works, are considered in the analysis. It is shown that by increasing the length of the horizontal part of the T-shaped mass, the amount of static deflection increases, natural frequency decreases and nonlinear shift of the resonance frequency increases. It is concluded that attaching an electrode plate with a T-shaped configuration to the end of the cantilever microbeam results in a configuration with larger pull-in voltage and smaller nonlinear shift of the resonance frequency compared to the configuration in which the electrode plate is directly attached to it.

Analytical Modeling of Fluid Sloshing in A 2D Rectangular Container with A Bottom-Mounted T-Shaped Baffle

An analytical procedure is presented to evaluate the fluid sloshing characteristics in a two-dimensional(2D)rectangular container with a bottom-mounted T-shaped baffle.The fluid region is divided into several sub-domains with hypothetical interfaces and the velocities and pressures of the fluid on adjacent interfaces should be identical.The separation of variables in conjunction with the superposition principle is employed to formulate the velocity potential of each sub-domain.The Fourier series expansion is used to derive the eigenvalue equation by substituting the velocity potential solutions into the free surface conditions and the continuity conditions on adjacent interfaces.Under the horizontal base excitation,the total velocity potential of fluid is decomposed of the impulsive and perturbed velocity potentials.The orthogonality of the sloshing modes is demonstrated by implementing Gauss formula.The dynamic response equation is established by incorporating the total velocity potential solution into the surface wave equation.Excellent agreements are achieved between the present results and those from the reported literature and finite element code.Numerical results are exhibited to reveal the effect of the baffle parameters and excitation frequency on sloshing characteristics and responses of liquid.

Variation of hydraulic parameters with different wing of a T-shape spur dike in bend channels

In the present research,by using a numerical model,some analyses were performed on flows around a T-shape spur dike and a support structure located at its upstream under different wing to length ratios of T-shape spur dike in the order of 0.25,0.50,0.75 and 1.00.In order to verify numerical model,physical model data were used in presence of a single T shape spur dike.Results from numerical model are desirably in agreement with those of physical one because the regression between both data is 0.86 up to 0.92.In this research,all hydraulic parameters of flows,streamlines and dimensions of flow separation zones were studied in order to select the most practical model.Increased W/L results in 7%–12%increase in the length of flow separation zone and in 2%increase in the width of this zone compared to W/L=0.25.

Instability of parasitic capacitance in T-shape-gate enhancementmode AlGaN/GaN MIS-HEMTs

Parasitic capacitances associated with overhangs of the T-shape-gate enhancement-mode(E-mode)GaN-based power device,were investigated by frequency/voltage-dependent capacitance-voltage and inductive-load switching measurements.The overhang capacitances induce a pinch-off voltage distinguished from that of the E-mode channel capacitance in the gate capacitance and the gatedrain capacitance characteristic curves.Frequency-and voltage-dependent tests confirm the instability caused by the trapping of interface/bulk states in the LPCVD-SiNx passivation dielectric.Circuit-level double pulse measurement also reveals its impact on switching transition for power switching applications.

Stresses due to an adhesion crack in T-shaped junction of two orthotropic plates

The general solution of stresses is derived for a T-shaped junction of two thin plates with an adhesion crack. The plates are orthotropic. A shear force is applied on the crack surface. The analysis is based on the supposition that the stresses in each plate can be approximated by a plane stress condition. The results obtained are verified by numerical calculation of FEM.

SYNTHESIS OF LIQUID CRYSTALLINE COPOLYESTERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNIT AND CROWN ETHER CYCLE

A novel series of liquid crystalline copolyesters with T-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4′-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4′-(α,ω-hexanedioyloxy)dibenzoyl dichloride(M_1),2-(4′-ethoxyphenyl)hydroquinone(M_2)and cis-4,4′-bis(4- hydroxyphenylazo)dibenzo-18-crown-6(M_3).The molecular weights of copolyesters are not high,and the intrinsic viscosity [η]of copolyesters ranges from 0.29-0.43.The monomers ...

Vertical polarization-induced doping InN/InGaN heterojunction tunnel FET with hetero T-shaped gate

A novel vertical InN/InGaN heterojunction tunnel FET with hetero T-shaped gate as well as polarization-doped source and drain region(InN-Hetero-TG-TFET)is proposed and investigated by Silvaco-Atlas simulations for the first time.Compared with the conventional physical doping TFET devices,the proposed device can realize the P-type source and N-type drain region by means of the polarization effect near the top InN/InGaN and bottom InGaN/InN heterojunctions respectively,which could provide an effective solution of random dopant fluctuation(RDF)and the related problems about the high thermal budget and expensive annealing techniques due to ion-implantation physical doping.Besides,due to the hetero T-shaped gate,the improvement of the on-state performance can be achieved in the proposed device.The simulations of the device proposed here in this work show ION of 4.45×10^(-5)A/μm,ION/IOFF ratio of 10^(13),and SS_(avg)of 7.5 mV/dec in InN-Hetero-TG-TFET,which are better than the counterparts of the device with a homo T-shaped gate(InN-Homo-TG-TFET)and our reported lateral polarization-induced InN-based TFET(PI-InN-TFET).These results can provide useful reference for further developing the TFETs without physical doping process in low power electronics 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 tab, the energy level eal of the side coupled quantum dot QDb, and the relative angle θ of magnetic moment M, but also the asymmetry parameter a in ferromagnetic leads and so on. All these parameters greatly influence the density of states of the eentral quantum dot QDa. This system is a possible candidate for spin valve transistors and may have potential applications in the spintronies.

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 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.

Design and Implementation of T-Shaped Planar Antenna for MIMO Applications

This paper proposes,demonstrates,and describes a basic T-shaped Multi-Input and Multi-Output(MIMO)antenna with a resonant frequency of 3.1 to 10.6 GHz.Compared with the U-shaped antenna,the mutual coupling is minimized by using a T-shaped patch antenna.The T-shaped patch antenna shapes filter properties are tested to achieve separation over the 3.1 to 10.6 GHz frequency range.The parametric analysis,including width,duration,and spacing,is designed in the MIMO applications for good isolation.On the FR4 substratum,the configuration of MIMO is simulated.The appropriate dielectric material ε_(r)=4.4 is introduced using this contribution and application array feature of the MIMO systems.In this paper,FR4 is used due to its high dielectric strength and low cost.For 3.1 to 10.6 GHz and 3SRR,T-shaped patch antennas are used in the field to increase bandwidth.The suggested Tshaped MIMO antenna is calculated according to the HFSS 13.0 program simulation performances.The antenna suggested is,therefore,a successful WLAN candidate.

CPW Fed Double T-Shaped Array Antenna with Suppressed Mutual Coupling

A compact CPW-fed double T-Shaped antenna is proposed for dual-band wireless local area network (WLAN) operations. For the proposed antenna, the -10 dB return loss bandwidth could reach about 25.5% for the 2.4 GHz band and 5.7 % for the 5 GHz band, which meet the required bandwidth specification of WLAN standard. To reduce the mutual coupling and get high isolation between two dual-band antennas, we proposed the novel electromagnetic band gap (EBG) structures. When the EBG structure is employed, a -13dB and -30dB mutual coupling reduction is achieved at 2.4 and 5.2 GHz. It shows that the features of small size, uniplanar structure, good radiation characteristics and small mutual coupling are promising for multi-input multi-output (MIMO) applications.

A method for coastal oil tank detection in polarimetric SAR images based on recognition of T-shaped harbor

To automatically detect oil tanks in polarimetric synthetic aperture radar（SAR） images, a coastal oil tank detection method is proposed based on recognition of T-shaped harbor. First of all, the T-shaped harbor is detected to locate the region of interest（ROI） of oil tanks. Then all suspicious targets in the ROI are extracted by the segmentation of strong scattering targets and the classifier of H/α. The template targets are selected from the suspicious targets by the combination of a proposed circular degree parameter and the similarity parameter（SP） of the polarimetric coherency matrix. Finally, oil tanks are detected according to the statistics of the similarity parameter between each suspicious target and template targets in ROI. Polarimetric SAR data acquired by RADARSAT-2 over Berkeley and Singapore areas are used for testing. Experiment results show that most of the targets are correctly detected and the overall detection rate is close to 80%.The false rate is effectively reduced by the proposed algorithm compared with the method without T-shaped harbor recognition.

Novel Preparation of Magnetic Microcapsules by Using T-Shaped Microchannel Reactor

Traditional preparation of magnetic microcapsules involves cumbersome processes and often results in irregular-shaped products. Due to the stable laminar flow of reaction solution and the moderate reaction conditions, the T-shaped microchannel (T-MC) reactor is supposed to yield microcapsules with regular shape. In this paper, magnetic particles of ferroferric oxide modified by oleic acid (OA-Fe3O4) and dispersed in tetrachloroethylene were used as core material. Polymethyl methacrylate (PMMA) was used as shell material. Magnetic microcapsules were prepared by using a T-MC reactor. Factors that influenced the encapsulated reaction were investigated in details, which included the velocity ratio of aqueous phase to oil phase, the length and the inner diameter of the microchannel. The morphology, composition, and magnetic responsiveness of the magnetic microcapsules were analyzed and characterized by SEM, FTIR, XRD, TGA, and vibrating sample magnetometer (VSM). The results confirmed that magnetic microcapsules prepared by T-MC reactor were regular in shape.