2,473 research outputs found
Status of MICROSCOPE, a mission to test the Equivalence Principle in space
MICROSCOPE is a French Space Agency mission that aims to test the Weak
Equivalence Principle in space down to an accuracy of . This is two
orders of magnitude better than the current constraints, which will allow us to
test General Relativity as well as theories beyond General Relativity which
predict a possible Weak Equivalence Principle violation below . In
this communication, we describe the MICROSCOPE mission, its measurement
principle and instrument, and we give an update on its status. After a
successful instrument's commissioning, MICROSCOPE is on track for on-schedule
launch, expected in 2016.Comment: Proceedings of LISA Symposium X; accepted for publication in Journal
of Physics: Conference Serie
Imaging material properties of biological samples with a Force Feedback Microscope
Mechanical properties of biological samples have been imaged with a
\textit{Force Feedback Microscope}. Force, force gradient and dissipation are
measured simultaneously and quantitatively, merely knowing the AFM cantilever
spring constant. Our first results demonstrate that this robust method provides
quantitative high resolution force measurements of the interaction The little
oscillation imposed to the cantilever and the small value of its stiffness
result in a vibrational energy much smaller than the thermal energy, reducing
the interaction with the sample to a minimum. We show that the observed
mechanical properties of the sample depend on the force applied by the tip and
consequently on the sample indentation.
Moreover, the frequency of the excitation imposed to the cantilever can be
chosen arbitrarily, opening the way to frequency-dependent studies in
biomechanics, sort of spectroscopic AFM investigations
Out of equilibrium anomalous elastic response of a water nano-meniscus
We report the observation of a transition in the dynamical properties of
water nano-menicus which dramatically change when probed at different time
scales. Using a AFM mode that we name Force Feedback Microscopy, we observe
this change in the simultaneous measurements, at different frequencies, of the
stiffness G'(N/m), the dissipative coefficient G''(kg/sec) together with the
static force. At low frequency we observe a negative stiffness as expected for
capillary forces. As the measuring time approaches the microsecond, the dynamic
response exhibits a transition toward a very large positive stiffness. When
evaporation and condensation gradually lose efficiency, the contact line
progressively becomes immobile. This transition is essentially controlled by
variations of Laplace pressure
Resource allocation model for sensor clouds under the sensing as a service paradigm
The Sensing as a Service is emerging as a new Internet of Things (IoT) business model for sensors and data sharing in the cloud. Under this paradigm, a resource allocation model for the assignment of both sensors and cloud resources to clients/applications is proposed. This model, contrarily to previous approaches, is adequate for emerging IoT Sensing as a Service business models supporting multi-sensing applications and mashups of Things in the cloud. A heuristic algorithm is also proposed having this model as a basis. Results show that the approach is able to incorporate strategies that lead to the allocation of fewer devices, while selecting the most adequate ones for application needs.FCT (Foundation for Science and Technology) from Portugal within CEOT (Center for Electronic, Optoelectronic and Telecommunications)
UID/MULTI/00631/2019info:eu-repo/semantics/publishedVersio
On the Angular Dependence of InP High Electron Mobility Transistors for Cryogenic Low Noise Amplifiers in a Magnetic Field
The InGaAs-InAlAs-InP high electron mobility transistor (InP HEMT) is the
preferred active device used in a cryogenic low noise amplifier (LNA) for
sensitive detection of microwave signals. We observed that an InP HEMT
0.3-14GHz LNA at 2K, where the in-going transistors were oriented perpendicular
to a magnetic field, heavily degraded in gain and average noise temperature
already up to 1.5T. Dc measurements for InP HEMTs at 2K revealed a strong
reduction in the transistor output current as a function of static magnetic
field up to 14T. In contrast, the current reduction was insignificant when the
InP HEMT was oriented parallel to the magnetic field. Given the transistor
layout with large gate width/gate length ratio, the results suggest a strong
geometrical magnetoresistance effect occurring in the InP HEMT. This was
confirmed in the angular dependence of the transistor output current with
respect to the magnetic field. Key device parameters such as transconductance
and on-resistance were significantly affected at small angles and magnetic
fields. The strong angular dependence of the InP HEMT output current in a
magnetic field has important implications for the alignment of cryogenic LNAs
in microwave detection experiments involving magnetic fields
Internet protocol over wireless sensor networks, from myth to reality
Internet Protocol (IP) is a standard network layer protocol of the Internet architecture, allowing communication among heterogeneous networks. For a given network to be accessible from the Internet it must have a router that complies with this protocol. Wireless sensor networks have many smart sensing nodes with computational, communication and sensing capabilities. Such smart sensors cooperate to gather relevant data and present it to the user. The connection of sensor networks and the Internet has been realized using gateway or proxy- based approaches. Historically, several routing protocols were specifically created, discarding IP. However, recent research, prototypes and even implementation tools show that it is possible to combine the advantages of IP access with sensor networks challenges, with a major contribution from the 6LoWPAN Working Group. This paper presents the advantages and challenges of IP on sensor networks, surveys the state-of-art with some implementation examples, and points further research topics in this area
- …