4,139 research outputs found
First-principles study of the Young's modulus of Si <001> nanowires
We report the results of first-principles density functional theory
calculations of the Young's modulus and other mechanical properties of
hydrogen-passivated Si nanowires. The nanowires are taken to have
predominantly {100} surfaces, with small {110} facets. The Young's modulus, the
equilibrium length and the residual stress of a series of prismatic wires are
found to have a size dependence that scales like the surface area to volume
ratio for all but the smallest wires. We analyze the physical origin of the
size dependence, and compare the results to two existing models.Comment: 5 pages, 3 figure
Study of bonding methods for flip chip and beam leaded devices
The results are presented of a comprehensive study and evaluation for the bonding of flip chip and beam leaded devices onto hybrid microcircuit substrates used in high reliability space applications. The program included the evaluation of aluminum flip chips, solder (silver/tin) bump chips, gold beam leaded devices, and aluminum beam leaded devices
First-principles calculation of mechanical properties of Si <001> nanowires and comparison to nanomechanical theory
We report the results of first-principles density functional theory
calculations of the Young's modulus and other mechanical properties of
hydrogen-passivated Si nanowires. The nanowires are taken to have
predominantly {100} surfaces, with small {110} facets according to the Wulff
shape. The Young's modulus, the equilibrium length and the constrained residual
stress of a series of prismatic beams of differing sizes are found to have size
dependences that scale like the surface area to volume ratio for all but the
smallest beam. The results are compared with a continuum model and the results
of classical atomistic calculations based on an empirical potential. We
attribute the size dependence to specific physical structures and interactions.
In particular, the hydrogen interactions on the surface and the charge density
variations within the beam are quantified and used both to parameterize the
continuum model and to account for the discrepancies between the two models and
the first-principles results.Comment: 14 pages, 10 figure
NASA micromin computer Monthly progress letter, Jan. 1967
Microminiature circuit development for flight control computer
Measuring recovery in deaf, hard-of-hearing, and tinnitus patients in a mental health care setting:validation of the I.ROC
This study was aimed at validating the Individual Recovery Outcomes Counter (I.ROC) for deaf, hard-of-hearing, and tinnitus patients in a mental health care setting. There is a need for an accessible instrument to monitor treatment effects in this population. The I.ROC measures recovery, seeing recovery as a process of experiencing a meaningful life, despite the limitations caused by illness or disability. A total of 84 adults referred to 2 specialist mental health centers for deaf, hard-of-hearing, and tinnitus adults in the Netherlands completed the Dutch version of I.ROC and 3 other instruments. A total of 25 patients refused or did not complete the instruments: 50% of patients using sign language and 18% of patients using spoken language. Participants completed the measures at intake and then every 3 months. In this sample I.ROC demonstrated good internal consistency and convergent validity. Sensitivity to change was good, especially over a period of 6 or 9 months. This study provides preliminary evidence that the I.ROC is a valid instrument measuring recovery for hard-of-hearing and tinnitus patients using spoken language. For deaf patients using sign language, specifically those with limited language skills in spoken and written Dutch, more research is needed.</p
Automated Big Text Security Classification
In recent years, traditional cybersecurity safeguards have proven ineffective
against insider threats. Famous cases of sensitive information leaks caused by
insiders, including the WikiLeaks release of diplomatic cables and the Edward
Snowden incident, have greatly harmed the U.S. government's relationship with
other governments and with its own citizens. Data Leak Prevention (DLP) is a
solution for detecting and preventing information leaks from within an
organization's network. However, state-of-art DLP detection models are only
able to detect very limited types of sensitive information, and research in the
field has been hindered due to the lack of available sensitive texts. Many
researchers have focused on document-based detection with artificially labeled
"confidential documents" for which security labels are assigned to the entire
document, when in reality only a portion of the document is sensitive. This
type of whole-document based security labeling increases the chances of
preventing authorized users from accessing non-sensitive information within
sensitive documents. In this paper, we introduce Automated Classification
Enabled by Security Similarity (ACESS), a new and innovative detection model
that penetrates the complexity of big text security classification/detection.
To analyze the ACESS system, we constructed a novel dataset, containing
formerly classified paragraphs from diplomatic cables made public by the
WikiLeaks organization. To our knowledge this paper is the first to analyze a
dataset that contains actual formerly sensitive information annotated at
paragraph granularity.Comment: Pre-print of Best Paper Award IEEE Intelligence and Security
Informatics (ISI) 2016 Manuscrip
Utility of electronic patient records for evaluating stroke secondary prevention in primary care
Use of very high resolution climate model data for hydrological modelling: estimation of potential evaporation
Climate model data are increasingly used to drive hydrological models, to assess the possible
impacts of climate change on river flows. Hydrological models often require potential evaporation
(PE) from vegetation, alongside precipitation, but PE is not usually output by climate models so has to
be estimated from other meteorological variables. Here, the Penman-Monteith formula is applied to
estimate PE using data from a 12 km Regional Climate Model (RCM) and a nested very high resolution
(1.5 km) RCM covering southern Britain. PE estimates from RCM runs driven by reanalysis boundary
conditions are compared to observation-based PE data, to assess performance. The comparison
shows that both the 1.5 and 12 km RCMs reproduce observation-based PE well, on daily and monthly
time-steps, and enables choices to be made about application of the formula using the available
data. Data from Current and Future RCM runs driven by boundary conditions from a Global Climate
Model are then used to investigate potential future changes in PE, and how certain factors affect
those changes. In particular, the importance of including changes in canopy resistance is
demonstrated. PE projections are also shown to vary to some extent according to how aerosols are
modelled in the RCMs
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