65,175 research outputs found
Environmental impacts of grazed clover/grass pastures
peer-reviwedGrazed clover/grass pastures are important for animal production systems and the clover
component is critical for its contribution to N inputs via biological fixation of atmospheric
N2. The resource efficiency and environmental emissions for clover/grass pastures can
differ from that of N-fertilised grass-only pastures. Fixation of N2 by clover uses photosynthetically-
fixed carbon, whereas fertiliser N production consumes fossil fuels and
has net greenhouse gas (GHG) emissions. Clover has a higher phosphorus (P) requirement
than grass and where extra P fertiliser is used for clover/grass pastures the risk of
P loss to waterways is greater than for grass-only pastures. Nitrogen leaching from
grazed pasture increases exponentially with increased N inputs and urinary-N contributes
70 to 90% of total N leaching. However, the few studies comparing clover/grass and
N-fertilised grass-only pastures at similar total N inputs indicated similar N leaching
losses. Nitrous oxide emissions from grazed pastures due to N-cycling of excreta are
similar for clover/grass and N-fertilised grass-only pastures at similar total N inputs.
However, grass-only pasture requires the application of N fertiliser, which will result in
additional specific losses that don’t occur from clover-fixed N. Thus, total N2O emissions
are generally higher for N-fertilised grass pastures than for clover/grass pastures. A summary
of various whole-system and life cycle assessment analyses for dairy farms from
various countries indicated that at similar total N inputs, clover/grass pasture systems
can be more efficient than N-fertilised grass systems per kilogram of milk produced from
an energy use and GHG perspective whereas results for nutrient losses to waterways were
mixed and appear to be similar for both pasture types. In practice, other management
practices on farm, such as crop integration, supplementary feeding strategy and winter
management, can have a larger overall effect on environmental emissions than whether
the N input is derived from fertiliser N or from N2 fixation
Thermodynamical quantities of lattice full QCD from an efficient method
I extend to QCD an efficient method for lattice gauge theory with dynamical
fermions. Once the eigenvalues of the Dirac operator and the density of states
of pure gluonic configurations at a set of plaquette energies (proportional to
the gauge action) are computed, thermodynamical quantities deriving from the
partition function can be obtained for arbitrary flavor number, quark masses
and wide range of coupling constants, without additional computational cost.
Results for the chiral condensate and gauge action are presented on the
lattice at flavor number , 1, 2, 3, 4 and many quark masses and coupling
constants. New results in the chiral limit for the gauge action and its
correlation with the chiral condensate, which are useful for analyzing the QCD
chiral phase structure, are also provided.Comment: Latex, 11 figures, version accepted for publicatio
The Differences of Star Formation History Between Merging Galaxies and Field Galaxies in the EDR of the SDSS
Based on the catalog of merging galaxies in the Early Data Release (EDR) of
the Sloan Digital Sky Survey (SDSS), the differences of star formation history
between merging galaxies and field galaxies are studied statistically by means
of three spectroscopic indicators the 4000-\r{A} break strength, the Balmer
absorption-line index, and the specific star formation rate. It is found that
for early-type merging galaxies the interactions will not induce significant
enhancement of the star-formation activity because of its stability and lack of
cool gas. On the other hand, late-type merging galaxies always in general
display more active star formation than field galaxies on different timescales
within about 1Gyr. We also conclude that the mean stellar ages of late-type
merging galaxies are younger than those of late-type field galaxies.Comment: 9 pages, 4 figures, accepted for publication in PAS
Authorization and access control of application data in Workflow systems
Workflow Management Systems (WfMSs) are used to support the modeling and coordinated execution of business processes within an organization or across organizational boundaries. Although some research efforts have addressed requirements for authorization and access control for workflow systems, little attention has been paid to the requirements as they apply to application data accessed or managed by WfMSs. In this paper, we discuss key access control requirements for application data in workflow applications using examples from the healthcare domain, introduce a classification of application data used in workflow systems by analyzing their sources, and then propose a comprehensive data authorization and access control mechanism for WfMSs. This involves four aspects: role, task, process instance-based user group, and data content. For implementation, a predicate-based access control method is used. We believe that the proposed model is applicable to workflow applications and WfMSs with diverse access control requirements
Novel thick-foam ferroelectret with engineered voids for energy harvesting applications
This work reports a novel thick-foam ferroelectret which is designed and engineered for energy harvesting applications. We fabricated this ferroelectret foam by mixing a chemical blowing agent with a polymer solution, then used heat treatment to activate the agent and create voids in the polymer foam. The dimensions of the foam, the density and size of voids can be well controlled in the fabrication process. Therefore, this ferroelectret can be engineered into optimized structure for energy harvesting applications
A Tri-band-notched UWB Antenna with Low Mutual Coupling between the Band-notched Structures
A compact printed U-shape ultra-wideband (UWB) antenna with triple band-notched characteristics is presented. The proposed antenna, with compact size of 24×33 mm2, yields an impedance bandwidth of 2.8-12GHz for VSWR<2, except the notched bands. The notched bands are realized by introducing two different types of slots. Two C-shape half-wavelength slots are etched on the radiating patch to obtain two notched bands in 3.3-3.7GHz for WiMAX and 7.25-7.75GHz for downlink of X-band satellite communication systems. In order to minimize the mutual coupling between the band-notched structures, the middle notched band in 5-6GHz for WLAN is achieved by using a U-slot defected ground structure. The parametric study is carried out to understand the mutual coupling. Surface current distributions and equivalent circuit are used to illustrate the notched mechanism. The performance of this antenna both by simulation and by experiment indicates that the proposed antenna is suitable and a good candidate for UWB applications
Linear and Non Linear Effects on the Newtonian Gravitational Constant as deduced from the Torsion Balance
The Newtonian gravitational constant has still 150 parts per million of
uncertainty. This paper examines the linear and nonlinear equations governing
the rotational dynamics of the torsion gravitational balance. A nonlinear
effect modifying the oscillation period of the torsion gravitational balance is
carefully explored.Comment: 11 pages, 2 figure
Matrix convex functions with applications to weighted centers for semidefinite programming
In this paper, we develop various calculus rules for general smooth matrix-valued functions and for the class of matrix convex (or concave) functions first introduced by Loewner and Kraus in 1930s. Then we use these calculus rules and the matrix convex function -log X to study a new notion of weighted convex centers for semidefinite programming (SDP) and show that, with this definition, some known properties of weighted centers for linear programming can be extended to SDP. We also show how the calculus rules for matrix convex functions can be used in the implementation of barrier methods for optimization problems involving nonlinear matrix functions.matrix convexity;matrix monotonicity;semidefinite programming
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