50,363 research outputs found
CMOL: Second Life for Silicon?
This report is a brief review of the recent work on architectures for the
prospective hybrid CMOS/nanowire/ nanodevice ("CMOL") circuits including
digital memories, reconfigurable Boolean-logic circuits, and mixed-signal
neuromorphic networks. The basic idea of CMOL circuits is to combine the
advantages of CMOS technology (including its flexibility and high fabrication
yield) with the extremely high potential density of molecular-scale
two-terminal nanodevices. Relatively large critical dimensions of CMOS
components and the "bottom-up" approach to nanodevice fabrication may keep CMOL
fabrication costs at affordable level. At the same time, the density of active
devices in CMOL circuits may be as high as 1012 cm2 and that they may provide
an unparalleled information processing performance, up to 1020 operations per
cm2 per second, at manageable power consumption.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Investigation of Micro Porosity Sintered wick in Vapor Chamber for Fan Less Design
Micro Porosity Sintered wick is made from metal injection molding processes,
which provides a wick density with micro scale. It can keep more than 53 %
working fluid inside the wick structure, and presents good pumping ability on
working fluid transmission by fine infiltrated effect. Capillary pumping
ability is the important factor in heat pipe design, and those general
applications on wick structure are manufactured with groove type or screen
type. Gravity affects capillary of these two types more than a sintered wick
structure does, and mass heat transfer through vaporized working fluid
determines the thermal performance of a vapor chamber. First of all, high
density of porous wick supports high transmission ability of working fluid. The
wick porosity is sintered in micro scale, which limits the bubble size while
working fluid vaporizing on vapor section. Maximum heat transfer capacity
increases dramatically as thermal resistance of wick decreases. This study on
permeability design of wick structure is 0.5 - 0.7, especially permeability (R)
= 0.5 can have the best performance, and its heat conductivity is 20 times to a
heat pipe with diameter (Phi) = 10mm. Test data of this vapor chamber shows
thermal performance increases over 33 %.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Design, Fabrication and Characterization of a Piezoelectric Microgenerator Including a Power Management Circuit
We report in this paper the design, fabrication and experimental
characterization of a piezoelectric MEMS microgenerator. This device scavenges
the energy of ambient mechanical vibrations characterized by frequencies in the
range of 1 kHz. This component is made with Aluminum Nitride thin film
deposited with a CMOS compatible process. Moreover we analyze two possible
solutions for the signal rectification: a discrete doubler-rectifier and a full
custom power management circuit. The ASIC developed for this application takes
advantage of diodes with very low threshold voltage and therefore allows the
conversion of extremely low input voltages corresponding to very weak input
accelerations. The volume of the proposed generator is inferior to 1mm3 and the
generated powers are in the range of 1W. This system is intended to supply
power to autonomous wireless sensor nodes.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
Mechanical Fatigue on Gold MEMS Devices: Experimental Results
The effect of mechanical fatigue on structural performances of gold devices
is investigated. The pull-in voltage of special testing micro-systems is
monitored during the cyclical load application. The mechanical collapse is
identified as a dramatic loss of mechanical strength of the specimen. The
fatigue limit is estimated through the stair-case method by means of the
pull-in voltage measurements. Measurements are performed by means of the
optical interferometric technique.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
The Hot-Spot Phenomenon and its Countermeasures in Bipolar Power Transistors by Analytical Electro-Thermal Simulation
This communication deals with a theoretical study of the hot spot onset (HSO)
in cellular bipolar power transistors. This well-known phenomenon consists of a
current crowding within few cells occurring for high power conditions, which
significantly decreases the forward safe operating area (FSOA) of the device.
The study was performed on a virtual sample by means of a fast, fully
analytical electro-thermal simulator operating in the steady state regime and
under the condition of imposed input base current. The purpose was to study the
dependence of the phenomenon on several thermal and geometrical factors and to
test suitable countermeasures able to impinge this phenomenon at higher biases
or to completely eliminate it. The power threshold of HSO and its localization
within the silicon die were observed as a function of the electrical bias
conditions as for instance the collector voltage, the equivalent thermal
resistance of the assembling structure underlying the silicon die, the value of
the ballasting resistances purposely added in the emitter metal
interconnections and the thickness of the copper heat spreader placed on the
die top just to the aim of making more uniform the temperature of the silicon
surface.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Model Based Sensor System for Temperature Measurement in R744 Air Conditioning Systems
The goal is the development of a novel principle for the temperature
acquisition of refrigerants in CO2 air conditioning systems. The new approach
is based on measuring the temperature inside a pressure sensor, which is also
needed in the system. On the basis of simulative investigations of different
mounting conditions functional relations between measured and medium
temperature will be derived.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
Nanostructures, Magnetic Semiconductors and Spinelectronics
A short overview is given of recent advances in the field of
nanosemiconductors, which are suitable as materials for spin polarized
transport of charge carriers. On the basis of last theoretical and experimental
achievements it is shown that development of diluted and wide forbidden zone
semiconductors with controlled disorders as well as their molecular structures
is the very prospective way for magnetic semiconductors preparation.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Electromechanical Reliability Testing of Three-Axial Silicon Force Sensors
This paper reports on the systematic electromechanical characterization of a
new three-axial force sensor used in dimensional metrology of micro components.
The siliconbased sensor system consists of piezoresistive mechanicalstress
transducers integrated in thin membrane hinges supporting a suspended flexible
cross structure. The mechanical behavior of the fragile micromechanical
structure isanalyzed for both static and dynamic load cases. This work
demonstrates that the silicon microstructure withstands static forces of 1.16N
applied orthogonally to the front-side of the structure. A statistical Weibull
analysis of the measured data shows that these values are significantly reduced
if the normal force is applied to the back of the sensor. Improvements of the
sensor system design for future development cycles are derived from the
measurement results.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Development of EHD Ion-Drag Micropump for Microscale Electronics Cooling Systems
In this investigation, the numerical simulation of electrohydrodynamic (EHD)
ion-drag micropumps with micropillar electrode geometries have been performed.
The effect of micropillar height and electrode spacing on the performance of
the micropumps was investigated. The performance of the EHD micropump improved
with increased applied voltage and decreased electrode spacing. The optimum
micropillar height for the micropump with electrode spacing of 40m and
channel height of 100m at 200V was 40m, where a maximum mass flow
rate of 0.18g/min was predicted. Compared to that of planar electrodes, the 3D
micropillar electrode geometry enhanced the overall performance of the EHD
micropumps.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
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