scholarly journals IGBT Package Design for High Power Aircraft Electronic Systems

2001 ◽  
Vol 123 (4) ◽  
pp. 338-343 ◽  
Author(s):  
Farhad Sarvar ◽  
David C. Whalley ◽  
Ming K. Low
Keyword(s):  
High Power ◽  
Semiconductor Device ◽  
Analytical Models ◽  
Electronic Systems ◽  
3D Analysis ◽  
Package Design ◽  
Evaluation Of Performance ◽  
Wide Range ◽  
Semiconductor Packages ◽  
Design Options

This paper will discuss the design of semiconductor packages having integrated air cooled heatsinks for use in high power electronic systems. It will demonstrate how simple models of the heat transfer from the heatsink fins, which are based on empirical correlations, may be utilized in combination with either simple analytical models or two-dimensional finite difference (FD) models of the heat conduction from the semiconductor die through the multilayer package structure to the base of the fins. These models allow the rapid evaluation of performance under both steady-state and transient overload conditions, and can be used to rapidly explore a wide range of design options before selecting candidate layouts for more detailed evaluation using 3D analysis tools. Wind tunnel experiments, which will also be reported, have been carried out to verify the modeling results for different semiconductor device layouts. These trials demonstrate excellent agreement between the models and experimental results.

scholarly journals A New 4500-HP Gas Turbine for Pipeline Industrial Service

1970 ◽  
Author(s):  
R. R. Oliver ◽  
F. Fraschetti
Keyword(s):  
Gas Turbine ◽  
Mechanical Design ◽  
Maximum Efficiency ◽  
Heavy Duty ◽  
Cooperative Effort ◽  
Package Design ◽  
Wide Range ◽  
Industrial Service ◽  
Design Options ◽  
Regenerative Cycle

This paper describes the performance and mechanical design of a 4500-hp, two shaft heavy duty simple or regenerative cycle gas turbine. This machine resulted from an international cooperative effort of the joint authors’ respective companies. Initially planned for gas pipelines and process applications, a line of load compressors has been integrated into the single package design. Options include indoor or outdoor models and geared or direct mechanical output for applications not served by the integral compressor models. A variable area load turbine nozzle assures maximum efficiency over a wide range of load, speed, and amibient conditions.

The Effects of Material Properties on Heat Dissipation in High Power Electronics

1998 ◽  
Vol 120 (3) ◽  
pp. 280-289 ◽  
Author(s):  
T. J. Lu ◽  
A. G. Evans ◽  
J. W. Hutchinson
Keyword(s):  
Thermal Conductivity ◽  
Power Electronics ◽  
High Power ◽  
Heat Dissipation ◽  
Substrate Material ◽  
High Thermal Conductivity ◽  
Analytical Models ◽  
Wide Range ◽  
Power Densities

The role of the substrate in determining heat dissipation in high power electronics is calculated, subject to convective cooling in the small Biot number regime. Analytical models that exploit the large aspect ratio of the substrate to justify approximations are shown to predict the behavior with good accuracy over a wide range of configurations. The solutions distinguish heat spreading effects’ that enable high chip-level power densities from insulation effects that arise at large chip densities. In the former, the attributes of high thermal conductivity are apparent, especially when the substrate dimensions are optimized. Additional benefits that derive from a thin layer of a high thermal conductivity material (such as diamond) are demonstrated. In the insulating region, which arises at high overall power densities, the substrate thermal conductivity has essentially no effect on the heat dissipation. Similarly, for compact multichip module designs, with chips placed on both sides of the substrate, heat dissipation is insensitive to the choice of the substrate material, unless advanced cooling mechanisms are used to remove heat around the module perimeter.

Structural and electronic properties of defects in semiconductors

1995 ◽  
Vol 53 ◽  
pp. 4-5
Author(s):  
J.L. Batstone
Keyword(s):  
Semiconductor Device ◽  
Chemical Vapor ◽  
Misfit Strain ◽  
Organic Chemical ◽  
Extended Defects ◽  
Transmission Electron ◽  
Semiconductor Thin Films ◽  
Wide Range ◽  
Metal Organic ◽  
Film Substrate

The development of growth techniques such as metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy during the last fifteen years has resulted in the growth of high quality epitaxial semiconductor thin films for the semiconductor device industry. The III-V and II-VI semiconductors exhibit a wide range of fundamental band gap energies, enabling the fabrication of sophisticated optoelectronic devices such as lasers and electroluminescent displays. However, the radiative efficiency of such devices is strongly affected by the presence of optically and electrically active defects within the epitaxial layer; thus an understanding of factors influencing the defect densities is required.Extended defects such as dislocations, twins, stacking faults and grain boundaries can occur during epitaxial growth to relieve the misfit strain that builds up. Such defects can nucleate either at surfaces or thin film/substrate interfaces and the growth and nucleation events can be determined by in situ transmission electron microscopy (TEM).

scholarly journals Universal mobility characteristics of graphene originating from charge scattering by ionised impurities

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jonathan H. Gosling ◽  
Oleg Makarovsky ◽  
Feiran Wang ◽  
Nathan D. Cottam ◽  
Mark T. Greenaway ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Carrier Density ◽  
Carrier Mobility ◽  
Carrier Transport ◽  
Analytical Models ◽  
Pristine Graphene ◽  
High Electron ◽  
Boltzmann Transport ◽  
Transport Parameters ◽  
Wide Range

AbstractPristine graphene and graphene-based heterostructures can exhibit exceptionally high electron mobility if their surface contains few electron-scattering impurities. Mobility directly influences electrical conductivity and its dependence on the carrier density. But linking these key transport parameters remains a challenging task for both theorists and experimentalists. Here, we report numerical and analytical models of carrier transport in graphene, which reveal a universal connection between graphene’s carrier mobility and the variation of its electrical conductivity with carrier density. Our model of graphene conductivity is based on a convolution of carrier density and its uncertainty, which is verified by numerical solution of the Boltzmann transport equation including the effects of charged impurity scattering and optical phonons on the carrier mobility. This model reproduces, explains, and unifies experimental mobility and conductivity data from a wide range of samples and provides a way to predict a priori all key transport parameters of graphene devices. Our results open a route for controlling the transport properties of graphene by doping and for engineering the properties of 2D materials and heterostructures.

scholarly journals Development of Permeability Models for Saturated Fluid Flow across Arrays of Fibre Clusters

2002 ◽  
Vol 11 (3) ◽  
pp. 096369350201100
Author(s):  
E.M. Gravel ◽  
T.D. Papathanasiou
Keyword(s):  
Analytical Models ◽  
Dual Porosity ◽  
Hydraulic Permeability ◽  
Fibrous Media ◽  
Fibre Bundles ◽  
Hexagonal Packing ◽  
Composites Manufacturing ◽  
Starting Point ◽  
Wide Range ◽  
Flow Through

Dual porosity fibrous media are important in a number of applications, ranging from bioreactor design and transport in living systems to composites manufacturing. In the present study we are concerned with the development of predictive models for the hydraulic permeability ( Kp) of various arrays of fibre bundles. For this we carry out extensive computations for viscous flow through arrays of fibre bundles using the Boundary Element Method (BEM) implemented on a multi-processor computer. Up to 350 individual filaments, arranged in square or hexagonal packing within bundles, which are also arranged in square of hexagonal packing, are included in each simulation. These are simple but not trivial models for fibrous preforms used in composites manufacturing – dual porosity systems characterised by different inter- and intra-tow porosities. The way these porosities affect the hydraulic permeability of such media is currently unknown and is elucidated through our simulations. Following numerical solution of the governing equations, ( Kp) is calculated from the computed flowrate through Darcy's law and is expressed as function of the inter- and intra-tow porosities (φ, φt) and of the filament radius ( Rf). Numerical results are also compared to analytical models. The latter form the starting point in the development of a dimensionless correlation for the permeability of such dual porosity media. It is found that the numerically computed permeabilities follow that correlation for a wide range of φ i, φt and Rf.

A LOW DROPOUT REGULATOR WITH LOW QUIESCENT CURRENT AND HIGH POWER SUPPLY REJECTION OVER WIDE RANGE OF FREQUENCY FOR SOC

2011 ◽  
Vol 20 (01) ◽  
pp. 1-13 ◽  
Author(s):  
CHENCHANG ZHAN ◽  
WING-HUNG KI
Keyword(s):  
High Power ◽  
Power Supply ◽  
Cmos Process ◽  
High Loop ◽  
Wide Range ◽  
Quiescent Current ◽  
Low Dropout Regulator ◽  
Output Capacitor ◽  
Large Output ◽  
Supply Rejection

A CMOS low quiescent current low dropout regulator (LDR) with high power supply rejection (PSR) and without large output capacitor is proposed for system-on-chip (SoC) power management applications. By cascoding a power NMOS with the PMOS pass transistor, high PSR over a wide frequency range is achieved. The gate-drive of the cascode NMOS is controlled by an auxiliary LDR that draws only 1 μA from a small charge pump, thus helping in reducing the quiescent current. Adaptive biasing is employed for the multi-stage error amplifier of the core LDR to achieve high loop gain hence high PSR at low frequency, low quiescent current at light load and high bandwidth at heavy load. A prototype of the proposed high-PSR LDR is fabricated using a standard 0.35 μm CMOS process, occupying an active area of 0.066 mm2. The lowest supply voltage is 1.6 V and the preset output voltage is 1.2 V. The maximum load current is 10 mA. The measured worst-case PSR at full load without using large output capacitor is -22.7 dB up to 60 MHz. The line and load regulations are 0.25 mV/V and 0.32 mV/mA, respectively.

scholarly journals The metabolic response of the Bradypus sloth to temperature

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5600 ◽  
Author(s):  
Rebecca Naomi Cliffe ◽  
David Michael Scantlebury ◽  
Sarah Jane Kennedy ◽  
Judy Avey-Arroyo ◽  
Daniel Mindich ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Energy Expenditure ◽  
High Power ◽  
Metabolic Response ◽  
Metabolic Responses ◽  
Metabolic Depression ◽  
Wide Range ◽  
Energetic Constraints ◽  
Power Costs

Poikilotherms and homeotherms have different, well-defined metabolic responses to ambient temperature (Ta), but both groups have high power costs at high temperatures. Sloths (Bradypus) are critically limited by rates of energy acquisition and it has previously been suggested that their unusual departure from homeothermy mitigates the associated costs. No studies, however, have examined how sloth body temperature and metabolic rate vary with Ta. Here we measured the oxygen consumption (VO2) of eight brown-throated sloths (B. variegatus) at variable Ta’s and found that VO2 indeed varied in an unusual manner with what appeared to be a reversal of the standard homeotherm pattern. Sloth VO2 increased with Ta, peaking in a metabolic plateau (nominal ‘thermally-active zone’ (TAZ)) before decreasing again at higher Ta values. We suggest that this pattern enables sloths to minimise energy expenditure over a wide range of conditions, which is likely to be crucial for survival in an animal that operates under severe energetic constraints. To our knowledge, this is the first evidence of a mammal provisionally invoking metabolic depression in response to increasing Ta’s, without entering into a state of torpor, aestivation or hibernation.

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