2,984 research outputs found
Improving GDP Measurement: A Forecast Combination Perspective
Two often-divergent U.S. GDP estimates are available, a widely-used expenditure side version, GDPE, and a much less widely-used income-side version, GDPI . We propose and explore a "forecast combination" approach to combining them. We then put the theory to work, producing a superior combined estimate of GDP growth for the U.S., GDPC. We compare GDPC to GDPE and GDPI, with particular attention to behavior over the business cycle. We discuss several variations and extensions.National Income and Product Accounts, Output, Expenditure, Economic Activity, Business Cycle, Recession
Improving GDP measurement: a forecast combination perspective
Two often-divergent U.S. GDP estimates are available, a widely-used expenditure-side version GDPE, and a much less widely-used income-side version GDI . The authors propose and explore a "forecast combination" approach to combining them. They then put the theory to work, producing a superior combined estimate of GDP growth for the U.S., GDPC. The authors compare GDPC to GDPE and GDPI , with particular attention to behavior over the business cycle. They discuss several variations and extensions.Business cycles ; Recessions ; Expenditures, Public
Fully Autonomous Reproduction Robotic System
Self-reproduction robotics systems are capable of producing other robotic systems; such that the resulting systems are fully functional and autonomous. In this poster, a novel method for producing modular robotic systems is presented, where the resulting robots consist of Cubelets - modular robots kit - and the producing robot is built using Lego Mindstorms EV3
Gaussian Markov random fields for discrete optimization via simulation:framework and algorithms
We consider optimizing the expected value of some performance measure of a dynamic stochastic simulation with a statistical guarantee for optimality when the decision variables are discrete, in particular, integer-ordered; the number of feasible solutions is large; and the model execution is too slow to simulate even a substantial fraction of them. Our goal is to create algorithms that stop searching when they can provide inference about the remaining optimality gap similar to the correct-selection guarantee of ranking and selection when it simulates all solutions. Further, our algorithm remains competitive with fixed-budget algorithms that search efficiently but do not provide such inference. To accomplish this we learn and exploit spatial relationships among the decision variables and objective function values using a Gaussian Markov random field (GMRF). Gaussian random fields on continuous domains are already used in deterministic and stochastic optimization because they facilitate the computation of measures, such as expected improvement, that balance exploration and exploitation. We show that GMRFs are particularly well suited to the discrete decision–variable problem, from both a modeling and a computational perspective. Specifically, GMRFs permit the definition of a sensible neighborhood structure, and they are defined by their precision matrices, which can be constructed to be sparse. Using this framework, we create both single and multiresolution algorithms, prove the asymptotic convergence of both, and evaluate their finite-time performance empirically
The Stripe 82 Massive Galaxy Project II: Stellar Mass Completeness of Spectroscopic Galaxy Samples from the Baryon Oscillation Spectroscopic Survey
The Baryon Oscillation Spectroscopic Survey (BOSS) has collected spectra for
over one million galaxies at over a volume of 15.3 Gpc (9,376
deg) -- providing us an opportunity to study the most massive galaxy
populations with vanishing sample variance. However, BOSS samples are selected
via complex color cuts that are optimized for cosmology studies, not galaxy
science. In this paper, we supplement BOSS samples with photometric redshifts
from the Stripe 82 Massive Galaxy Catalog and measure the total galaxy stellar
mass function (SMF) at and . With the total SMF in hand,
we characterize the stellar mass completeness of BOSS samples. The
high-redshift CMASS ("constant mass") sample is significantly impacted by mass
incompleteness and is 80% complete at only in
the narrow redshift range . The low redshift LOWZ sample is 80%
complete at for . To construct
mass complete samples at lower masses, spectroscopic samples need to be
significantly supplemented by photometric redshifts. This work will enable
future studies to better utilize the BOSS samples for galaxy-formation science.Comment: 18 pages, 17 figures, 5 table
Streaming Graph Challenge: Stochastic Block Partition
An important objective for analyzing real-world graphs is to achieve scalable
performance on large, streaming graphs. A challenging and relevant example is
the graph partition problem. As a combinatorial problem, graph partition is
NP-hard, but existing relaxation methods provide reasonable approximate
solutions that can be scaled for large graphs. Competitive benchmarks and
challenges have proven to be an effective means to advance state-of-the-art
performance and foster community collaboration. This paper describes a graph
partition challenge with a baseline partition algorithm of sub-quadratic
complexity. The algorithm employs rigorous Bayesian inferential methods based
on a statistical model that captures characteristics of the real-world graphs.
This strong foundation enables the algorithm to address limitations of
well-known graph partition approaches such as modularity maximization. This
paper describes various aspects of the challenge including: (1) the data sets
and streaming graph generator, (2) the baseline partition algorithm with
pseudocode, (3) an argument for the correctness of parallelizing the Bayesian
inference, (4) different parallel computation strategies such as node-based
parallelism and matrix-based parallelism, (5) evaluation metrics for partition
correctness and computational requirements, (6) preliminary timing of a
Python-based demonstration code and the open source C++ code, and (7)
considerations for partitioning the graph in streaming fashion. Data sets and
source code for the algorithm as well as metrics, with detailed documentation
are available at GraphChallenge.org.Comment: To be published in 2017 IEEE High Performance Extreme Computing
Conference (HPEC
Neuroinflammation and white matter alterations in obesity assessed by Diffusion Basis Spectrum Imaging
Human obesity is associated with low-grade chronic systemic inflammation, alterations in brain structure and function, and cognitive impairment. Rodent models of obesity show that high-calorie diets cause brain inflammation (neuroinflammation) in multiple regions, including the hippocampus, and impairments in hippocampal-dependent memory tasks. To determine if similar effects exist in humans with obesity, we applied Diffusion Basis Spectrum Imaging (DBSI) to evaluate neuroinflammation and axonal integrity. We examined diffusion-weighted magnetic resonance imaging (MRI) data in two independent cohorts of obese and non-obese individuals (Cohort 1: 25 obese/21 non-obese; Cohort 2: 18 obese/41 non-obese). We applied Tract-based Spatial Statistics (TBSS) to allow whole-brain white matter (WM) analyses and compare DBSI-derived isotropic and anisotropic diffusion measures between the obese and non-obese groups. In both cohorts, the obese group had significantly greater DBSI-derived restricted fraction (DBSI-RF; an indicator of neuroinflammation-related cellularity), and significantly lower DBSI-derived fiber fraction (DBSI-FF; an indicator of apparent axonal density) in several WM tracts (all correcte
SNP Assay Development for Linkage Map Construction, Anchoring Whole-Genome Sequence, and Other Genetic and Genomic Applications in Common Bean.
A total of 992,682 single-nucleotide polymorphisms (SNPs) was identified as ideal for Illumina Infinium II BeadChip design after sequencing a diverse set of 17 common bean (Phaseolus vulgaris L) varieties with the aid of next-generation sequencing technology. From these, two BeadChips each with >5000 SNPs were designed. The BARCBean6K_1 BeadChip was selected for the purpose of optimizing polymorphism among market classes and, when possible, SNPs were targeted to sequence scaffolds in the Phaseolus vulgaris 14× genome assembly with sequence lengths >10 kb. The BARCBean6K_2 BeadChip was designed with the objective of anchoring additional scaffolds and to facilitate orientation of large scaffolds. Analysis of 267 F2 plants from a cross of varieties Stampede × Red Hawk with the two BeadChips resulted in linkage maps with a total of 7040 markers including 7015 SNPs. With the linkage map, a total of 432.3 Mb of sequence from 2766 scaffolds was anchored to create the Phaseolus vulgaris v1.0 assembly, which accounted for approximately 89% of the 487 Mb of available sequence scaffolds of the Phaseolus vulgaris v0.9 assembly. A core set of 6000 SNPs (BARCBean6K_3 BeadChip) with high genotyping quality and polymorphism was selected based on the genotyping of 365 dry bean and 134 snap bean accessions with the BARCBean6K_1 and BARCBean6K_2 BeadChips. The BARCBean6K_3 BeadChip is a useful tool for genetics and genomics research and it is widely used by breeders and geneticists in the United States and abroad
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