123 research outputs found
PIKS: A Technique to Identify Actionable Trends for Policy-Makers Through Open Healthcare Data
With calls for increasing transparency, governments are releasing greater
amounts of data in multiple domains including finance, education and
healthcare. The efficient exploratory analysis of healthcare data constitutes a
significant challenge. Key concerns in public health include the quick
identification and analysis of trends, and the detection of outliers. This
allows policies to be rapidly adapted to changing circumstances. We present an
efficient outlier detection technique, termed PIKS (Pruned iterative-k means
searchlight), which combines an iterative k-means algorithm with a pruned
searchlight based scan. We apply this technique to identify outliers in two
publicly available healthcare datasets from the New York Statewide Planning and
Research Cooperative System, and California's Office of Statewide Health
Planning and Development. We provide a comparison of our technique with three
other existing outlier detection techniques, consisting of auto-encoders,
isolation forests and feature bagging. We identified outliers in conditions
including suicide rates, immunity disorders, social admissions,
cardiomyopathies, and pregnancy in the third trimester. We demonstrate that the
PIKS technique produces results consistent with other techniques such as the
auto-encoder. However, the auto-encoder needs to be trained, which requires
several parameters to be tuned. In comparison, the PIKS technique has far fewer
parameters to tune. This makes it advantageous for fast, "out-of-the-box" data
exploration. The PIKS technique is scalable and can readily ingest new
datasets. Hence, it can provide valuable, up-to-date insights to citizens,
patients and policy-makers. We have made our code open source, and with the
availability of open data, other researchers can easily reproduce and extend
our work. This will help promote a deeper understanding of healthcare policies
and public health issues
A system for exploring big data: an iterative k-means searchlight for outlier detection on open health data
The interactive exploration of large and evolving datasets is challenging as
relationships between underlying variables may not be fully understood. There
may be hidden trends and patterns in the data that are worthy of further
exploration and analysis. We present a system that methodically explores
multiple combinations of variables using a searchlight technique and identifies
outliers. An iterative k-means clustering algorithm is applied to features
derived through a split-apply-combine paradigm used in the database literature.
Outliers are identified as singleton or small clusters. This algorithm is swept
across the dataset in a searchlight manner. The dimensions that contain
outliers are combined in pairs with other dimensions using a susbset scan
technique to gain further insight into the outliers. We illustrate this system
by anaylzing open health care data released by New York State. We apply our
iterative k-means searchlight followed by subset scanning. Several anomalous
trends in the data are identified, including cost overruns at specific
hospitals, and increases in diagnoses such as suicides. These constitute novel
findings in the literature, and are of potential use to regulatory agencies,
policy makers and concerned citizens.Comment: 2018 International Joint Conference on Neural Networks (IJCNN
Building predictive models of healthcare costs with open healthcare data
Due to rapidly rising healthcare costs worldwide, there is significant
interest in controlling them. An important aspect concerns price transparency,
as preliminary efforts have demonstrated that patients will shop for lower
costs, driving efficiency. This requires the data to be made available, and
models that can predict healthcare costs for a wide range of patient
demographics and conditions. We present an approach to this problem by
developing a predictive model using machine-learning techniques. We analyzed
de-identified patient data from New York State SPARCS (statewide planning and
research cooperative system), consisting of 2.3 million records in 2016. We
built models to predict costs from patient diagnoses and demographics. We
investigated two model classes consisting of sparse regression and decision
trees. We obtained the best performance by using a decision tree with depth 10.
We obtained an R-square value of 0.76 which is better than the values reported
in the literature for similar problems.Comment: 2020 IEEE International Conference on Healthcare Informatics (ICHI
Spin Decoherence from Hamiltonian dynamics in Quantum Dots
The dynamics of a spin-1/2 particle coupled to a nuclear spin bath through an
isotropic Heisenberg interaction is studied, as a model for the spin
decoherence in quantum dots. The time-dependent polarization of the central
spin is calculated as a function of the bath-spin distribution and the
polarizations of the initial bath state. For short times, the polarization of
the central spin shows a gaussian decay, and at later times it revives
displaying nonmonotonic time dependence. The decoherence time scale dep ends on
moments of the bath-spin distribuition, and also on the polarization strengths
in various bath-spin channels. The bath polarizations have a tendency to
increase the decoherence time scale. The effective dynamics of the central spin
polarization is shown to be describ ed by a master equation with non-markovian
features.Comment: 11 pages, 6 figures Accepted for publication in Phys.Rev
A classification scheme for visual defects arising in semiconductor wafer inspection
In this paper we describe a novel scheme to characterize surface defects and flaws that arise in semiconductor wafer processing. This is done by analyzing the texture of an image of the defect. We have developed a taxonomy for textures, which classifies textures into the broad classes of disordered, strongly ordered and weakly ordered. Disordered textures are described in terms of their fractal dimension, strongly ordered textures are by the placement of primitives, and weakly ordered textures by the underlying orientation field. We have developed an algorithm to measure the fractal dimension of a given texture. We use the qualitative theory of differential equations to devise a symbol set for the weakly ordered textures in terms of singularities. We have devised an algorithm to process an image of a defect and extract qualitative descriptions based on this theory.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28525/1/0000322.pd
Computing oriented texture fields
The first step is the analysis of oriented texture consists of the extraction of an orientation field. The orientation field is comprised of the angle and coherence images, which describe at each point the dominant local orientation and degree of anisotropy, respectively. A new algorithm for computing the orientation field for a flow-like texture is presented. The basic idea behind the algorithm is to use an oriented filter, namely the gradient of Gaussian, and perform manipulations on the resulting gradient vector field. The most important aspect of the new algorithm is that it is provably optimal in estimating the local orientation of an oriented texture. An added strength of the algorithm is that it is simpler and has a better signal-to-noise ratio than previous approaches, because it employs fewer derivative operations. We also propose a new measure of coherence, which works better than previous measures. The estimates for orientation and coherence are related to measures in the statistical theory of directional data. We advocate the use of the angle and coherence images as intrinsic images. An analysis of oriented textures will require the computation of these intrinsic images as a first step. In this sense, the computation of the orientation field, resulting in the intrinsic images, is indispensible in the analysis of oriented textures. We provide results from several experiments to indicate the usefulness of the angle and coherence intrinsic images. These results show that the notion of scale plays an important role in the interpretation of textures. Further, measures defined on these intrinsic images are useful for the inspection of surfaces.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29428/1/0000509.pd
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