1,001 research outputs found
B. Cohen^
A Transversely Isotropic Biphasic Model for Unconfined Compression of Growth Plate and Chondroepiphysis Using the biphasic theory for hydrated soft tissue
Towards Inferring Mechanical Lock Combinations using Wrist-Wearables as a Side-Channel
Wrist-wearables such as smartwatches and fitness bands are equipped with a
variety of high-precision sensors that support novel contextual and
activity-based applications. The presence of a diverse set of on-board sensors,
however, also expose an additional attack surface which, if not adequately
protected, could be potentially exploited to leak private user information. In
this paper, we investigate the feasibility of a new attack that takes advantage
of a wrist-wearable's motion sensors to infer input on mechanical devices
typically used to secure physical access, for example, combination locks. We
outline an inference framework that attempts to infer a lock's unlock
combination from the wrist motion captured by a smartwatch's gyroscope sensor,
and uses a probabilistic model to produce a ranked list of likely unlock
combinations. We conduct a thorough empirical evaluation of the proposed
framework by employing unlocking-related motion data collected from human
subject participants in a variety of controlled and realistic settings.
Evaluation results from these experiments demonstrate that motion data from
wrist-wearables can be effectively employed as a side-channel to significantly
reduce the unlock combination search-space of commonly found combination locks,
thus compromising the physical security provided by these locks
Passive-performance, analysis, and upgrades of a 1-ton seismic attenuation system
The 10m Prototype facility at the Albert-Einstein-Institute (AEI) in Hanover,
Germany, employs three large seismic attenuation systems to reduce mechanical
motion. The AEI Seismic-Attenuation-System (AEI-SAS) uses mechanical
anti-springs in order to achieve resonance frequencies below 0.5Hz. This system
provides passive isolation from ground motion by a factor of about 400 in the
horizontal direction at 4Hz and in the vertical direction at 9Hz. The presented
isolation performance is measured under vacuum conditions using a combination
of commercial and custom-made inertial sensors. Detailed analysis of this
performance led to the design and implementation of tuned dampers to mitigate
the effect of the unavoidable higher order modes of the system. These dampers
reduce RMS motion substantially in the frequency range between 10 and 100Hz in
6 degrees of freedom. The results presented here demonstrate that the AEI-SAS
provides substantial passive isolation at all the fundamental mirror-suspension
resonances
Huddle test measurement of a near Johnson noise limited geophone
In this paper, the sensor noise of two geophone configurations (L-22D and L-4C geophones from Sercel with custom built amplifiers) was measured by performing two huddle tests. It is shown that the accuracy of the results can be significantly improved by performing the huddle test in a seismically quiet environment and by using a large number of reference sensors to remove the seismic foreground signal from the data. Using these two techniques, the measured sensor noise of the two geophone configurations matched the calculated predictions remarkably well in the bandwidth of interest (0.01 Hz–100 Hz). Low noise operational amplifiers OPA188 were utilized to amplify the L-4C geophone to give a sensor that was characterized to be near Johnson noise limited in the bandwidth of interest with a noise value of 10−11 m/Hz⎯⎯⎯⎯⎯√10−11 m/Hz at 1 Hz
Approximate Analytical Model for the Squeeze-Film Lubrication of the Human Ankle Joint with Synovial Fluid Filtrated by Articular Cartilage
The aim of this article is to propose an analytical approximate squeeze-film lubrication model of the human ankle joint for a quick assessment of the synovial pressure field and the load carrying due to the squeeze motion. The model starts from the theory of boosted lubrication for the human articular joints lubrication (Walker et al., Rheum Dis 27:512–520, 1968; Maroudas, Lubrication and wear in joints. Sector, London, 1969) and takes into account the fluid transport across the articular cartilage using Darcy’s equation to depict the synovial fluid motion through a porous cartilage matrix. The human ankle joint is assumed to be cylindrical enabling motion in the sagittal plane only. The proposed model is based on a modified Reynolds equation; its integration allows to obtain a quick assessment on the synovial pressure field showing a good agreement with those obtained numerically (Hlavacek, J Biomech 33:1415–1422, 2000). The analytical integration allows the closed form description of the synovial fluid film force and the calculation of the unsteady gap thickness
Measurement of Optical Response of a Detuned Resonant Sideband Extraction Interferometer
We report on the optical response of a suspended-mass detuned resonant
sideband extraction (RSE) interferometer with power recycling. The purpose of
the detuned RSE configuration is to manipulate and optimize the optical
response of the interferometer to differential displacements (induced by
gravitational waves) as a function of frequency, independently of other
parameters of the interferometer. The design of our interferometer results in
an optical gain with two peaks: an RSE optical resonance at around 4 kHz and a
radiation pressure induced optical spring at around 41 Hz. We have developed a
reliable procedure for acquiring lock and establishing the desired optical
configuration. In this configuration, we have measured the optical response to
differential displacement and found good agreement with predictions at both
resonances and all other relevant frequencies. These results build confidence
in both the theory and practical implementation of the more complex optical
configuration being planned for Advanced LIGO.Comment: 6 pages, 4 figures, for submission to Phys Rev Letter
Scanning electrochemical microscopy as a local probe of oxygen permeability in cartilage
The use of scanning electrochemical microscopy, a high-resolution chemical imaging technique, to probe the distribution and mobility of solutes in articular cartilage is described. In this application, a mobile ultramicroelectrode is positioned close (not, vert, similar1 μm) to the cartilage sample surface, which has been equilibrated in a bathing solution containing the solute of interest. The solute is electrolyzed at a diffusion-limited rate, and the current response measured as the ultramicroelectrode is scanned across the sample surface. The topography of the samples was determined using Ru(CN)64−, a solute to which the cartilage matrix was impermeable. This revealed a number of pit-like depressions corresponding to the distribution of chondrocytes, which were also observed by atomic force and light microscopy. Subsequent imaging of the same area of the cartilage sample for the diffusion-limited reduction of oxygen indicated enhanced, but heterogeneous, permeability of oxygen across the cartilage surface. In particular, areas of high permeability were observed in the cellular and pericellular regions. This is the first time that inhomogeneities in the permeability of cartilage toward simple solutes, such as oxygen, have been observed on a micrometer scale
Acoustic Response of a Layer of Spherical Inclusions with a Random or Periodic Arrangement
Starting with the classic work of Ying and Truell [1], the scattering of a plane elastic wave by an isolated elastic sphere embedded in an unbounded medium has been studied in great detail. Similarly, the propagation of an effective elastic wave in an elastic matrix containing a random or periodic distribution of inclusions has received considerable attention. By comparison, an intermediate level of microstructure — a single layer of inclusions in an elastic matrix — has received very little attention. Apart from the fact that this problem is worth studying in its own right because of its inherent value as a canonical problem in elastodynamics of materials with a microstructure, it has applications in geophysics and quantitative nondestructive evaluation
Corrections to Chiral Dynamics of Heavy Hadrons: (I) 1/M Correction
In earlier publications we have analyzed the strong and radiative decays of
heavy hadrons in a formalism which incorporates both heavy-quark and chiral
symmetries. In particular, we have derived a heavy-hadron chiral Lagrangian
whose coupling constants are related by the heavy-quark flavor-spin symmetry
arising from the QCD Lagrangian with infinitely massive quarks. In this paper,
we re-examine the structure of the above chiral Lagrangian by including the
effects of corrections in the heavy quark effective theory. The
relations among the coupling constants, originally derived in the heavy-quark
limit, are modified by heavy quark symmetry breaking interactions in QCD. Some
of the implications are discussed.Comment: PHYZZX, 45 pages, 1 figure (not included), CLNS 93/1192,
IP-ASTP-02-93, ITP-SB-93-0
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