14,898 research outputs found
Modeling Individual Cyclic Variation in Human Behavior
Cycles are fundamental to human health and behavior. However, modeling cycles
in time series data is challenging because in most cases the cycles are not
labeled or directly observed and need to be inferred from multidimensional
measurements taken over time. Here, we present CyHMMs, a cyclic hidden Markov
model method for detecting and modeling cycles in a collection of
multidimensional heterogeneous time series data. In contrast to previous cycle
modeling methods, CyHMMs deal with a number of challenges encountered in
modeling real-world cycles: they can model multivariate data with discrete and
continuous dimensions; they explicitly model and are robust to missing data;
and they can share information across individuals to model variation both
within and between individual time series. Experiments on synthetic and
real-world health-tracking data demonstrate that CyHMMs infer cycle lengths
more accurately than existing methods, with 58% lower error on simulated data
and 63% lower error on real-world data compared to the best-performing
baseline. CyHMMs can also perform functions which baselines cannot: they can
model the progression of individual features/symptoms over the course of the
cycle, identify the most variable features, and cluster individual time series
into groups with distinct characteristics. Applying CyHMMs to two real-world
health-tracking datasets -- of menstrual cycle symptoms and physical activity
tracking data -- yields important insights including which symptoms to expect
at each point during the cycle. We also find that people fall into several
groups with distinct cycle patterns, and that these groups differ along
dimensions not provided to the model. For example, by modeling missing data in
the menstrual cycles dataset, we are able to discover a medically relevant
group of birth control users even though information on birth control is not
given to the model.Comment: Accepted at WWW 201
Criticality Aware Soft Error Mitigation in the Configuration Memory of SRAM based FPGA
Efficient low complexity error correcting code(ECC) is considered as an
effective technique for mitigation of multi-bit upset (MBU) in the
configuration memory(CM)of static random access memory (SRAM) based Field
Programmable Gate Array (FPGA) devices. Traditional multi-bit ECCs have large
overhead and complex decoding circuit to correct adjacent multibit error. In
this work, we propose a simple multi-bit ECC which uses Secure Hash Algorithm
for error detection and parity based two dimensional Erasure Product Code for
error correction. Present error mitigation techniques perform error correction
in the CM without considering the criticality or the execution period of the
tasks allocated in different portion of CM. In most of the cases, error
correction is not done in the right instant, which sometimes either suspends
normal system operation or wastes hardware resources for less critical tasks.
In this paper,we advocate for a dynamic priority-based hardware scheduling
algorithm which chooses the tasks for error correction based on their area,
execution period and criticality. The proposed method has been validated in
terms of overhead due to redundant bits, error correction time and system
reliabilityComment: 6 pages, 8 figures, conferenc
Anatomy of extreme events in a complex adaptive system
We provide an analytic, microscopic analysis of extreme events in an adaptive
population comprising competing agents (e.g. species, cells, traders,
data-packets). Such large changes tend to dictate the long-term dynamical
behaviour of many real-world systems in both the natural and social sciences.
Our results reveal a taxonomy of extreme events, and provide a microscopic
understanding as to their build-up and likely duration.Comment: 8 pages, 4 figures. Now with Postscript figure
Development of an integrated BEM approach for hot fluid structure interaction: BEST-FSI: Boundary Element Solution Technique for Fluid Structure Interaction
As part of the continuing effort at NASA LeRC to improve both the durability and reliability of hot section Earth-to-orbit engine components, significant enhancements must be made in existing finite element and finite difference methods, and advanced techniques, such as the boundary element method (BEM), must be explored. The BEM was chosen as the basic analysis tool because the critical variables (temperature, flux, displacement, and traction) can be very precisely determined with a boundary-based discretization scheme. Additionally, model preparation is considerably simplified compared to the more familiar domain-based methods. Furthermore, the hyperbolic character of high speed flow is captured through the use of an analytical fundamental solution, eliminating the dependence of the solution on the discretization pattern. The price that must be paid in order to realize these advantages is that any BEM formulation requires a considerable amount of analytical work, which is typically absent in the other numerical methods. All of the research accomplishments of a multi-year program aimed toward the development of a boundary element formulation for the study of hot fluid-structure interaction in Earth-to-orbit engine hot section components are detailed. Most of the effort was directed toward the examination of fluid flow, since BEM's for fluids are at a much less developed state. However, significant strides were made, not only in the analysis of thermoviscous fluids, but also in the solution of the fluid-structure interaction problem
Advanced information processing system for advanced launch system: Avionics architecture synthesis
The Advanced Information Processing System (AIPS) is a fault-tolerant distributed computer system architecture that was developed to meet the real time computational needs of advanced aerospace vehicles. One such vehicle is the Advanced Launch System (ALS) being developed jointly by NASA and the Department of Defense to launch heavy payloads into low earth orbit at one tenth the cost (per pound of payload) of the current launch vehicles. An avionics architecture that utilizes the AIPS hardware and software building blocks was synthesized for ALS. The AIPS for ALS architecture synthesis process starting with the ALS mission requirements and ending with an analysis of the candidate ALS avionics architecture is described
Capturing Evolution Genes for Time Series Data
The modeling of time series is becoming increasingly critical in a wide
variety of applications. Overall, data evolves by following different patterns,
which are generally caused by different user behaviors. Given a time series, we
define the evolution gene to capture the latent user behaviors and to describe
how the behaviors lead to the generation of time series. In particular, we
propose a uniform framework that recognizes different evolution genes of
segments by learning a classifier, and adopt an adversarial generator to
implement the evolution gene by estimating the segments' distribution.
Experimental results based on a synthetic dataset and five real-world datasets
show that our approach can not only achieve a good prediction results (e.g.,
averagely +10.56% in terms of F1), but is also able to provide explanations of
the results.Comment: a preprint version. arXiv admin note: text overlap with
arXiv:1703.10155 by other author
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