136,888 research outputs found
Leaf Optical Responses to Light and Soil Nutrient Availability in Temperature Deciduous Trees
Leaf optical parameters influence light availability at the cellular, leaf, and canopy scale of integration. While recent studies have focused on leaf optical responses to acute plant stress, the effects of changes in plant resources on leaf optics remain poorly characterized. We examined leaf optical and anatomical responses of five temperate deciduous tree species to moderate changes in nutrient and light availability. Spectral reflectance in the visible waveband generally increased at high light, but decreased with increased nutrient availability. Patterns of both spectral reflectance and absorptance were primarily determined by chlorophyll concentration although carotenoid concentration was also influential. While most anatomical features did not explain residual variation in reflectance, cuticle thickness was significantly related to reflectance at complementary angles compared to the angle of incidence. Absorptance did not change with light environment; however, absorption efficiency per unit biomass increased by approximately 40% under low light, due to reduced leaf mass per area. We conclude that changes in resource availability differentially influence leaf optical properties and that such changes are driven primarily by changes in pigment concentrations. The magnitude of leaf optical responses to moderate changes in resource availability was comparable to those of acute stress responses and varied among species
Phase Structure of Non-Compact QED3 and the Abelian Higgs Model
We review the phase structure of a three-dimensional, non-compact Abelian
gauge theory (QED3) as a function of the number of 4-component massless
fermions. There is a critical up to which there is dynamical fermion
mass generation and an associated global symmetry breaking. We discuss various
approaches to the determination of , which lead to estimates ranging from
to . This theory with N=2 has been employed as an effective
continuum theory for the 2D quantum antiferromagnet where the observed Neel
ordering corresponds to dynamical fermion mass generation. Thus the value of
is of some physical interest. We also consider the phase structure of the
model with a finite gauge boson mass (the Abelian Higgs model).Comment: 14 pages, corrected the normalization of the fermion condensate in
section V, corrected a typo in the reference
Input-Output Tables for Alaska's Economy: A First Look
The specific objectives of this publication are to: ( 1) present a first
look in specific detail at the input-output tables of the Alaskan
economy, thereby examining Alaskan interindustry interactions and
dependencies; and (2) indicate, via relevant examples, how the information
contained in these typical input-out tables can be used by
private and public policymakers.Geographic isolation, a subarctic climate, large size, and a regionally
diverse landscape make Alaska a unique part of the United States. The
factors that make Alaska so unique also contribute to her present lack
of industrial and agricultural production, which requires shipment into
the state of most of the goods necessary for life. In filling the need for
such goods, the state of Washington has been, and continues to be, the
principal marketing and transportation center for Alaska-associated
trade
Machine Learning Based Auto-tuning for Enhanced OpenCL Performance Portability
Heterogeneous computing, which combines devices with different architectures,
is rising in popularity, and promises increased performance combined with
reduced energy consumption. OpenCL has been proposed as a standard for
programing such systems, and offers functional portability. It does, however,
suffer from poor performance portability, code tuned for one device must be
re-tuned to achieve good performance on another device. In this paper, we use
machine learning-based auto-tuning to address this problem. Benchmarks are run
on a random subset of the entire tuning parameter configuration space, and the
results are used to build an artificial neural network based model. The model
can then be used to find interesting parts of the parameter space for further
search. We evaluate our method with different benchmarks, on several devices,
including an Intel i7 3770 CPU, an Nvidia K40 GPU and an AMD Radeon HD 7970
GPU. Our model achieves a mean relative error as low as 6.1%, and is able to
find configurations as little as 1.3% worse than the global minimum.Comment: This is a pre-print version an article to be published in the
Proceedings of the 2015 IEEE International Parallel and Distributed
Processing Symposium Workshops (IPDPSW). For personal use onl
Alaska-Washington Trade Profile: Waterborne Commerce
The overall purpose of this study was to establish a profile of
Alaska-Washington waterborne movements, emphasizing commodity
and port components that determine the needs of a physical distribution
system. Specific objectives of the report are :
1. To determine Washington's share of the total Alaska-bound,
waterborne traffic.
2. To present selected Washington-to-Alaska, waterborne movements
by commodity and destination ports.
3. To present selected Alaska-to-Washington, waterborne movements
by commodity and origination ports.
4. To determine implications of the trade profile with regard to
future transportation and marketing needs.
It should be noted that there are sizable noncommodity trade
flows between the regions, i.e., labor, capital, and services that are
not in this data base. This report contains only data on major commodity
grouping and principal ports in Alaska. Additional information is on file at the Agricultural Experiment Station, University of Alaska, and at the Department of Agricultural Economics, Washington State University
Real-time diagnostics of gas/water assisted injection moulding using integrated ultrasonic sensors
YesAn ultrasound sensor system has been applied to the mould of both the water and gas assisted
injection moulding processes. The mould has a cavity wall mounted pressure sensor and instrumentation to
monitor the injection moulding machine. Two ultrasound sensors are used to monitor the arrival of the fluid
(gas or water) bubble tip through the detection of reflected ultrasound energy from the fluid polymer
boundary and the fluid bubble tip velocity through the polymer melt is estimated. The polymer contact with
the cavity wall is observed through the reflected ultrasound energy from that boundary. A theoretically
based estimation of the residual wall thickness is made using the ultrasound reflection from the fluid (gas or
water) polymer boundary whilst the samples are still inside the mould and a good correlation with a physical
measurement is observed
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