High Injection Velocity Research Articles

Interaction of a galactic wind with halo gas and the origin of multiphase extraplanar material

We study the interaction of galactic wind with hot halo gas using hydrodynamical simulations. We find that the outcome of this interaction depends crucially on the wind injection density and velocity. Various phases of the extraplanar media such as high velocity clouds (HVCs), outflowing clouds, and OVI regions can originate in the interaction zones of wind with the halo gas, depending on the injection velocity and density. In our simulations the size of the HVCs is of the order of 100 pc. The total mass contained in the clouds is 10^5 -- 10^7 M_sun and they have a normal distribution of velocities in the galactic standard of rest frame, similar to HVCs. For high injection density and velocity, a significant number of clouds move outwards and resemble the case of cold neutral outflows. Furthermore a 10^5 -- 10^6 K phase is formed in our simulations which has a column density ~ 10^{18} cm^{-2}, and resembles the observed OVI regions. The injection velocity and density are linked with the mass loading factor of the outflow, efficiency of energy injection due to supernovae and the SFR. Comparison of the predicted morphology of extraplanar gas with observations can serve as a useful diagnostic for constraining feedback efficiency of outflows.

Velocity and turbulence effects on high intensity distributed combustion

High intensity distributed combustion assists to provide substantial performance improvement for gas turbine applications for our quest to simultaneously seek improved pattern factor, ultra-low emission of NOx and CO, low noise, enhanced stability, fuel flexibility and higher efficiency. In such combustion method, controlled mixing between the injected air, fuel and hot reactive gases from within the combustor prior to mixture ignition must occur to achieve distributed reactions in the entire combustion chamber. Near zero emission of NO and CO has been achieved using methane as the fuel under distributed combustion conditions at high heat (energy) release intensity of 22–36MW/m3atm. The conditions to form distributed reaction in the combustor are further investigated through variation of air injection velocity with the output parameters focused on pollutants emission and combustor performance. The isothermal flowfield is examined using particle image velocimetry (PIV) to determine key features associated with the flowfield and its effects on pollutants emission and stability. The results showed higher entrainment and turbulence at increased injection velocity. Increase in injection velocity decreased NO emissions by some 20–48% with minimal impact on CO emission under premixed fuel–air condition. Less than 4ppm of NO was achieved at an injection velocity of 46m/s at an equivalence ratio of 0.7 and heat (energy) release intensity of 31.5MW/m3atm using normal temperature air. High injection velocity at the same operating condition decreased NO emission by some 20% to 3.2ppm. Higher injection velocity under preheated inlet air condition further decreased NO to 2ppm (48% reduction) at an equivalence ratio of 0.5. The results under non-premixed combustion conditions showed similar behavior. The reduction of NO with single injection parameter is attributed to improved distributed reaction condition from direct entrainment and rapid mixing of reactive species present in the combustion zone under high intensity combustion conditions.

Current Status of Slurries and Cleans for CMP of III-V Device Fabrications – a Critical Review

With the growth of cloud computing market, the need for logic and memory chips for data centers have been steadily growing which require low power and high performance. Another area of growing semiconductor application is mobile products which require increasingly higher performance without sacrificing power. The above two requirements can only be achieved by scaling supply voltage(Vdd).III-V materials enable Vdd scaling to address power without sacrificing performance due to the very high electron injection velocity at virtual source compared to Si. For example, Vinj (InGaAs) > 2 Vinj (Si) at less than half VDD. The development at Intel on InGaAs and at IMEC on Ge based FinFET structures have made it possible to conceive the integration scheme such as depicted in http://www.compoundsemiconductor.net/csc/features-details/19732136/Uniting-III-Vs-and-germanium-for-CMO.html . In order to enable such CMOS fabrication, development of CMP slurry, post CMP clean and modification of the presently available process tools need to be done. While new slurries and cleans will be needed to planarize III-V film layer(s) without compromising the film composition (and functionality), modification of the process tool will be needed to address potential release of toxic waste water into the the waste stream after planarization.At this time, published results show some academic works in addressing various issues related to CMP of III-V materials but there are not many reports in the public domain from the industry to address the need which is essential to successfully integrate CMP as an enabling step in the manufacturing of III-V CMOS devices.In this paper, the status of development of CMP processes, slurries and post CMP cleans will be reviewed and the critical needs to enable for the future III-V device integration will be analyzed.

Tight-binding study of quantum transport in nanoscale GaAs Schottky MOSFET

This paper explores the band structure effect to elucidate the feasibility of an ultra-scaled GaAs Schottky MOSFET (SBFET) in a nanoscale regime. We have employed a 20-band sp3d5 s* tight-binding (TB) approach to compute E — K dispersion. The considerable difference between the extracted effective masses from the TB approach and bulk values implies that quantum confinement affects the device performance. Beside high injection velocity, the ultra-scaled GaAs SBFET suffers from a low conduction band DOS in the Γ valley that results in serious degradation of the gate capacitance. Quantum confinement also results in an increment of the effective Schottky barrier height (SBH). Enhanced Schottky barriers form a double barrier potential well along the channel that leads to resonant tunneling and alters the normal operation of the SBFET. Major factors that may lead to resonant tunneling are investigated. Resonant tunneling occurs at low temperatures and low drain voltages, and gradually diminishes as the channel thickness and the gate length scale down. Accordingly, the GaAs (100) SBFET has poor ballistic performance in nanoscale regime.

Simulation Study of Thin-Body Ballistic n-MOSFETs Involving Transport in Mixed $\Gamma$-L Valleys

Transistor designs based on using mixed Γ-L valleys for electron transport are proposed to overcome the density of states bottleneck while maintaining high injection velocities. Using a self-consistent top-of-the-barrier transport model, improved current density over Si is demonstrated in GaAs/AlAsSb, GaSb/AlAsSb, and Ge-on-insulator-based single-gate thin-body n-channel metal-oxide-semiconductor field-effect transistors. All the proposed designs successively begin to outperform strained-Si-on-insulator and InAs-on-insulator (InAs-OI) in terms of ON-state currents as the effective oxide thickness is reduced below 0.7 nm. InAs-OI still exhibits the lowest intrinsic delay (τ) due to its single Γ valley.

Extrinsic and Intrinsic Performance of Vertical InAs Nanowire MOSFETs on Si Substrates

This paper presents dc and RF characterization as well as modeling of vertical InAs nanowire (NW) MOSFETs with L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> =200 nm and Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> high-κ dielectric. Measurements at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> =0.5 V show that high transconductance (g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> =1.37 mS/μm), high drive current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> =1.34 mA/μm), and low ON-resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> =287 Ωμm) can be realized using vertical InAs NWs on Si substrates. By measuring the 1/f-noise, the gate area normalized gate voltage noise spectral density, S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">VG</sub> ·L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> ·W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> , is determined to be lowered by one order of magnitude compared with similar devices with a high-κ film consisting of HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> only. In addition, with a virtual source model we are able to determine the intrinsic transport properties. These devices (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> =200 nm) show a high injection velocity (v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">inj</sub> =1.7×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> cm/s) with a performance degradation for array FETs predominantly due to an increase in series resistance.

Orientation and Shape Effects on Ballistic Transport Properties in Gate-All-Around Rectangular Germanium Nanowire nFETs

The electron transport properties of square and rectangular cross-sectional germanium nanowire (GeNW) field-effect transistors (FETs) with [001], [110], [111], and [112] crystal orientations are investigated. The electronic states of GeNWs are calculated by using an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sp</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s*</i> tight-binding model coupled to a Poisson equation self-consistently. A semiclassical ballistic FET model is used to evaluate the electron transport characteristics. For the square cross section, electron injection velocity dominates the drive current in GeNW FETs because the inversion electron density in the GeNW channels is mainly determined by the capacitance of the gate insulator, and a [110] GeNW FET achieves the highest drive current of all the orientations. In the case of rectangular cross section, the electron density in GeNWs is dependent on their orientations and cross-sectional geometries due to the small quantum capacitance, and the difference of the density of states of GeNWs significantly affects the drive current. A [112] GeNW FET on a (11̅0) face exhibits the highest injection velocity of all the calculated FETs but low drive current because of its insufficient density of states. As a result, a [110] GeNW FET on a (001) face, which has both large density of states and high injection velocity, achieves the highest drive current.

Coupled Level-Set/Volume-of-Fluid Method for Simulation of Injector Atomization

This paper presents results of a multiphase computational fluid dynamics code using a coupled level-set/volume-of-fluid method to simulate liquid atomization. This interface-capturing approach combines the mass conservation properties of the volume-of-fluid method with the accurate surface reconstruction properties of the level-set method, and it includes surface tension as a volume force calculated with second-order accuracy. Developed by one of the authors, the multiphase code builds upon the combined level-set/volume-of-fluid methodology to enable bubbly flow, liquid breakup, and phase-change simulations. The extension presented in this paper couples a Lagrangian dispersed phase model for postbreakup tracking of droplets with block-structured adaptive mesh refinement on the Eulerian grid. Under an appropriate set of criteria, the transfer of droplets representation from the Eulerian to the Lagrangian discretization enables the simulation of sprays on larger domains and for longer physical times without degrading the overall accuracy of the calculation. A demonstration for like-on-like jet impingement of relevance to cold startup of liquid rocket engines is presented here at low, moderate, and high injection velocities, including validation with experimental data.

Numerical Modeling of Injection of Shear-Thinning Gel Propellants Through Plain-Orifice Atomizer

A series of axisymmetric Navier–Stokes simulations were performed to study the mean and unsteady characteristics of gel propellant orifice flows at conditions representative of rocket injectors. The rheology of the gel was simulated assuming a shear-thinning fluid behaving in accordance with the Carreau–Yasuda model. The effects of Reynolds number (flow velocity), orifice L=D, fluid rheology, and orifice inlet chamfering were studied in a series of 200 independent simulations. Unsteady conditions were observed in most cases, due to the high injection velocities typical of rocket injection conditions. The magnitude and frequency of pulsations were characterized in these cases. In general, steady flows were obtained for lower Reynolds numbers and smoother inlet (i.e., greater chamfering) conditions. Mean discharge coefficients were computed for all cases to support design studies and engineering analyses.

Rheocasting an Engine Mounting Bracket in Commercial 7075

Wrought aluminium alloys are prone to hot tearing when cast into near-net shapes. This problem can be overcome by the novel casting technique of rheo-processing combined with high pressure die casting. An industrial engine mounting bracket is produced by rheo-process commercial 7075 with the patented CSIR-RCS and subsequent high pressure die casting. Section thickness changes and constraining geometry make this a difficult component to rheocast. X-ray radiography is used to evaluate hot tearing over the component and is correlated to piston injection shot profile velocities. Gross hot tearing is significantly reduced by a higher injection velocity but turbulent flow entraps air. Faster injection allows more time for flow before final solidification.

Effects of Surface Orientation on the Performance of Idealized III–V Thin-Body Ballistic n-MOSFETs

Ballistic on-currents of thin-body n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs) are compared across group IV (Si, Ge) and III-V (InAs, In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> As, GaAs, GaSb) materials for different body thickness values, surface orientations, and transport directions under several idealization assumptions. Previous simulation studies have shown that, as oxide capacitance increases, typical III-V channels with (100) surface perform worse than Si in the ballistic limit due to the degraded density-of-states (DOS). In this letter, simulation results based on tight-binding band structure calculations verify a recent proposal that confined III-V n-MOSFETs with small Γ-L separations overcome the DOS bottleneck and deliver high injection velocities, boosting on-current performance. By using the quantized L-valleys, GaSb with (100) or (111) surface orientations shows the best ballistic performance, outperforming all other materials. Although GaAs (100) and InAs or In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> As with any surface orientation suffer from the DOS bottleneck, GaAs (111) gives higher ballistic on -currents than Si does.

Mobility and Velocity Enhancement Effects of High Uniaxial Stress on Si (100) and (110) Substrates for Short-Channel pFETs

An experimental study of mobility and velocity enhancement effects is reported for highly strained short-channel p-channel field-effect transistors (pFETs) using a damascene-gate process on Si (100) and (110) substrates. The relationship between the mobility and the saturation velocity of hole under a compressive stress over 2.0 GPa is discussed. The local channel stress of 2.4 GPa is successfully measured with ultraviolet-Raman spectroscopy for the 30-nm-gate-length device with top-cut compressive-stress SiN liner and embedded SiGe. Mobility and saturation-velocity enhancements of (100) substrate are larger than those of (110) under the high channel stress. In consequence, the saturation current on (100) is larger than that on (110) for the pFETs with higher channel stress and shorter gate length. Moreover, the large enhancement rate of saturation velocity to mobility by the uniaxial stress suggests high injection velocity for the pFETs with the stressors since the high channel stress is induced near the potential peak of the source by using the damascene-gate technology.

Effects of shroud gas injection on material properties of tungsten layers coated by plasma spraying

Coated tungsten layers on stainless steel substrates were are produced by atmosphere plasma spraying. A shroud gas injection method was employed to reduce the ambient air entrainment into the plasma jets. The effects of shroud gas on the material properties of the tungsten layers were investigated by finding the dependence of oxide content, coating thickness and porosity on the injection velocity, shielding width, and mass flux of the shroud gas. The high injection velocity was more effective than thick shroud shielding in protecting the plasma jets from ambient air engulfment, and the mass flux of the shroud gas showed negligibly small effects on the suppression of air entrainment. Therefore, in order to produce a thick tungsten coating with low porosity and oxide contents, high injection velocity with a limited flow rate is a desirable operating condition for shroud gas injection in atmospheric plasma spraying.

Powstawanie obszarow laczenia strumieni tworzywa w wypraskach z wielogniazdowej formy wtryskowej

The results of investigations of weld lines locations in polyacetal moldings, prepared in 16-cavity injection mold with parallel cavities lay-out, were presented (Fig. 1, 3, 4). A method of melt flow visualization was used to record the weld line location on the surface of molding prepared at the proper injection conditions (method of "record grooves effect" formation control) (Fig. 2, 5). Despite using the geometrically balanced runners the cavities were not filled simultaneously (Fig. 6) and asymmetrical flow front of the polymer in the cavities led to weld lines shifts in relation to expected locations (Fig. 8-11). These results were obtained for both small and high injection velocities (Table 1). The reason of the weld line shift is the polymer melt movement in the runners, determined by runners' configuration. The results presented can be used in design of runners' sets in multicavity injection molds allowing preparation of moldings with no deterioration of mechanical strength in weld line area.

Influence of powder particle injection velocity on the microstructure of Al–12Si/SiC p coatings produced by laser cladding

The influence of powder particle injection velocity on the microstructure of coatings consisting of an Al–Si matrix reinforced with SiC particles prepared by laser cladding from mixtures of powders of Al–12 wt.% Si alloy and SiC was investigated both experimentally and by modeling. At low injection velocities SiC particles react with the molten aluminum alloy. Only a small fraction of SiC remains in the microstructure, which contains large amounts of particles of the reaction products Al 4SiC 4 and Si dispersed in the α-Al + Si eutectic matrix. By contrast, at high injection velocities chemical reactions between SiC and molten aluminum are almost entirely suppressed and the resulting microstructure consists only of SiC particles dispersed in the matrix. To investigate whether this behavior could be explained by the different temperatures reached by the injected particles as they fly through the laser beam, a physical–mathematical model describing the interaction between the laser beam and the powder stream in the off-axis blown powder laser cladding process was developed and applied to calculate the temperature attained by the powder particles as a result of their interaction with an Nd:YAG laser beam ( λ = 1.06 µm). At an injection velocity of 1 m/s the maximum temperature attained by SiC and Al–12Si particles is 3150 and 180 ºC, respectively. This result demonstrates that particle injection velocity is a major parameter affecting the microstructure of coatings produced by laser cladding, and must be carefully controlled.

Analytical solution to evaluate salt precipitation during CO 2 injection in saline aquifers

Carbon dioxide sequestration in deep saline aquifers is a means of reducing anthropogenic atmospheric emissions of CO 2. Among various mechanisms, CO 2 can be trapped in saline aquifers by dissolution in the formation water. Vaporization of water occurs along with the dissolution of CO 2. Vaporization can cause salt precipitation, which reduces porosity and impairs permeability of the reservoir in the vicinity of the wellbore, and can lead to reduction in injectivity. The amount of salt precipitation and the region in which it occurs may be important in CO 2 storage operations if salt precipitation significantly reduces injectivity. Here we develop an analytical model, as a simple and efficient tool to predict the amount of salt precipitation over time and space. This model is particularly useful at high injection velocities, when viscous forces dominate. First, we develop a model which treats the vaporization of water and dissolution of CO 2 in radial geometry. Next, the model is used to predict salt precipitation. The combined model is then extended to evaluate the effect of salt precipitation on permeability in terms of a time-dependent skin factor. Finally, the analytical model is corroborated by application to a specific problem with an available numerical solution, where a close agreement between the solutions is observed. We use the results to examine the effect of assumptions and approximations made in the development of the analytical solution. For cases studied, salt saturation was a few percent. The loss in injectivity depends on the degree of reduction of formation permeability with increased salt saturation. For permeability-reduction models considered in this work, the loss in injectivity was not severe. However, one limitation of the model is that it neglects capillary and gravity forces, and these forces might increase salt precipitation at the bottom of formation particularly when injection rate is low.

Effects of quantum coupling on the performance of metal-oxide-semiconductor field transistors

Based on the analysis of the three-dimensional Schrodinger equation, the effects of quantum coupling between the transverse and the longitudinal components of channel electron motion on the performance of ballistic MOSFETs have been theoretically investigated by self-consistently solving the coupled Schrodinger-Poisson equations with the finite-difference method. The results show that the quantum coupling between the transverse and the longitudinal components of the electron motion can largely affect device performance. It suggests that the quantum coupling effect should be considered for the performance of a ballistic MOSFET due to the high injection velocity of the channel electron.

Influence of injection molding parameters on the electrical resistivity of polycarbonate filled with multi-walled carbon nanotubes

Two polycarbonate (PC) composites with 2 and 5 wt% multi-walled carbon nanotube (MWNT) content were injection molded using a two-level, four-factor factorial design to evaluate the influences of holding pressure, injection velocity, mold temperature, and melt temperature on the electrical surface and volume resistivities. For both composites variations in resistivity of the injection-molded plates up to six orders of magnitude were found. The highest impact was determined for the injection velocity followed by the melt temperature and the interaction of both. The resistivity varied also locally within the plates showing differences up to five orders of magnitude for 2 wt% and up to two orders for 5 wt% MWNT. Thereby, areas of equal resistivity are formed in a semicircular shape with values increasing with the flow path. Transmission electron microscopy (TEM) investigations indicated a skin layer with highly oriented nanotubes in case of high injection velocity and low melt temperature, but a network-like structure even in the skin area at low injection velocity and high melt temperature.

Performance Limitations of Si Bulk CMOS and Alternatives for future ULSI

A channel material with high mobility and therefore high injection velocity can increase on current and reduce delay. Currently, strained-Si is the dominant technology for high performance MOSFETs and increasing the strain provides a viable solution to scaling. However, looking into future scaling of nanoscale MOSFETs it becomes important to look at higher mobility materials, like Ge and III-V materials together with innovative device structures which may perform better than even very highly strained Si. For both Ge and III-V devices problems of leakage need to be solved. Novel heterostructures will be needed to exploit the promised advantages of Ge and III-V based devices.

경사노즐 선회분사기의 가솔린 미립화 및 분무 내부 압력 분포

The static pressure distribution, atomization characteristics and velocity distribution of tapered nozzle swirl spray is analyzed and then compared with original swirl spray. The static pressure distribution inside the swirl spray is measured using a piezoresistive pressure transducer. Phase Doppler anemometry (PDA) is applied to measure and analyze the droplet size and velocity distribution of tapered nozzle and original swirl spray. The static pressure inside the spray shows the lower value compared to the atmospheric pressure and this pressure drop is getting attenuated as the taper angle is increased. The droplet size of tapered nozzle spray shows similar value compared to the original swirl spray at the horizontal mainstream while it shows increased value at vertical mainstream. The deteriorated atomization characteristics of tapered nozzle spray is improved by applying high fuel temperature injection without causing the spray collapse. The velocity results show that the larger portion of fuel is positioned with higher injection velocity, and the smaller portion of fuel is positioned with lower injection velocity with causing spatially non-uniform mixture distribution.