7,215 research outputs found
New Records of Michigan Cicadidae (Homoptera), With Notes on the Use of Songs to Monitor Range Changes
We present records of Diceroprocta vitripennis, Tibicen chloromera, and Tibicen pruinosa (new state record) in Michigan. Monitoring geographic range changes and population size differences by song suggests several population situations for cicadas: (1) sizable populations in most areas of apparently good habitat; (2) widely separated single individuals or small populations on the edges of populated regions, representing range extensions that may be of limited duration; (3) one or a few individuals present only once, probably transferred in soil on roots, and ultimately unsuccessful. Species- specific calling songs allow sensitive measurement of species\u27 range changes
Ununfoldable Polyhedra with Convex Faces
Unfolding a convex polyhedron into a simple planar polygon is a well-studied
problem. In this paper, we study the limits of unfoldability by studying
nonconvex polyhedra with the same combinatorial structure as convex polyhedra.
In particular, we give two examples of polyhedra, one with 24 convex faces and
one with 36 triangular faces, that cannot be unfolded by cutting along edges.
We further show that such a polyhedron can indeed be unfolded if cuts are
allowed to cross faces. Finally, we prove that ``open'' polyhedra with
triangular faces may not be unfoldable no matter how they are cut.Comment: 14 pages, 9 figures, LaTeX 2e. To appear in Computational Geometry:
Theory and Applications. Major revision with two new authors, solving the
open problem about triangular face
The Outer Limits of Galaxy Clusters: Observations to the Virial Radius with Suzaku, XMM, and Chandra
The outskirts of galaxy clusters, near the virial radius, remain relatively
unexplored territory and yet are vital to our understanding of cluster growth,
structure, and mass. In this presentation, we show the first results from a
program to constrain the state of the outer intracluster medium (ICM) in a
large sample of galaxy clusters, exploiting the strengths of three
complementary X-ray observatories: Suzaku (low, stable background), XMM-Newton
(high sensitivity), and Chandra (good spatial resolution). By carefully
combining observations from the cluster core to beyond r_200, we are able to
identify and reduce systematic uncertainties that would impede our spatial and
spectral analysis using a single telescope. Our sample comprises nine clusters
at z ~ 0.1-0.2 fully covered in azimuth to beyond r_200, and our analysis
indicates that the ICM is not in hydrostatic equilibrium in the cluster
outskirts, where we see clear azimuthal variations in temperature and surface
brightness. In one of the clusters, we are able to measure the diffuse X-ray
emission well beyond r_200, and we find that the entropy profile and the gas
fraction are consistent with expectations from theory and numerical
simulations. These results stand in contrast to recent studies which point to
gas clumping in the outskirts; the extent to which differences of cluster
environment or instrumental effects factor in this difference remains unclear.
From a broader perspective, this project will produce a sizeable fiducial data
set for detailed comparison with high-resolution numerical simulations.Comment: 8 pages, 6 figures. To appear in the proceedings of the Suzaku 2011
Conference, "Exploring the X-ray Universe: Suzaku and Beyond.
A Surface Parameterization Method for Airfoil Optimization and High Lift 2D Geometries Utilizing the CST Methodology
For aerodynamic modeling and optimization, it is desirable to limit the number of design variables to reduce model complexity and the requirements of the applied optimization scheme. The Class/Shape Transformation (CST) surface parameterization method presented by Kulfan has proven to be particularly useful for this while maintaining a wide range of applications. These include everything from smooth airfoils to 3D axi-symmetric bodies and wings. However, the CST method is confined to smooth geometries. This limits the CST method in applications incorporating discontinuous surfaces such as high lift aerodynamics with circulation control (CC) slots and flaps. The trailing edge slot on a circulation control wing (CCW) airfoil is not well modeled by the CST method. A parameterization of a CCW airfoil will result in the trailing edge slot being smoothed over. Therefore, a modified CST method must be utilized. For the case of parameterizing a known CCW airfoil, this is accomplished by detecting drastic changes in curvature and beginning a new parameterization in a multi-surface parameterization method. For creating a new CCW airfoil, this is achieved by modifying the 2D CST equations to incorporate a slot thickness term that also includes the horizontal location. These two methods can then be extended into 3D to model a circulation control wing (CCW) or even a blended wing body (BWB) aircraft incorporating CCW. The multi-surface parameterization modification can also be used to model other complex geometries to further enhance the robust nature of the CST method, thus creating a valuable design tool
Stomatal Density in Leaves of Various Xerophytes: A Preliminary Study
Recent general botany and plant anatomy textbooks state that stomatal density of xerophytic leaves is higher than that found in leaves of mesophytes. In contrast, previous textbooks indicate that stomatal density in xerophyte leaves is reduced. The purpose of this study is to examine the leaves of succulent and non-succulent xerophytes to determine if opposite trends in stomatal density correlate with the xeromorphic strategy employed. The species examined were the succulents Crassula argentea, Kalanchoe blossfeldiana, K. diagremontiana, K. tubiflorum, and the non-succulents Nerium oleander, Ammophila breviligulata, and Ficus elastica. Stomatal densities of succulents were determined directly from epidermal peels. Stomatal densities of non-succulents, whose stomates occur in crypts, were determined from cross-sections using stereo logical methods. Results indicate that stomatal density is reduced in leaf succulents and increased in non-succulent types
Automated detection of galaxy-scale gravitational lenses in high resolution imaging data
Lens modeling is the key to successful and meaningful automated strong
galaxy-scale gravitational lens detection. We have implemented a lens-modeling
"robot" that treats every bright red galaxy (BRG) in a large imaging survey as
a potential gravitational lens system. Using a simple model optimized for
"typical" galaxy-scale lenses, we generate four assessments of model quality
that are used in an automated classification. The robot infers the lens
classification parameter H that a human would have assigned; the inference is
performed using a probability distribution generated from a human-classified
training set, including realistic simulated lenses and known false positives
drawn from the HST/EGS survey. We compute the expected purity, completeness and
rejection rate, and find that these can be optimized for a particular
application by changing the prior probability distribution for H, equivalent to
defining the robot's "character." Adopting a realistic prior based on the known
abundance of lenses, we find that a lens sample may be generated that is ~100%
pure, but only ~20% complete. This shortfall is due primarily to the
over-simplicity of the lens model. With a more optimistic robot, ~90%
completeness can be achieved while rejecting ~90% of the candidate objects. The
remaining candidates must be classified by human inspectors. We are able to
classify lens candidates by eye at a rate of a few seconds per system,
suggesting that a future 1000 square degree imaging survey containing 10^7
BRGs, and some 10^4 lenses, could be successfully, and reproducibly, searched
in a modest amount of time. [Abridged]Comment: 17 pages, 11 figures, submitted to Ap
Consumption-based modeling of long-horizon returns
Numerous studies have documented the failure of consumption-based pricing models to explain observed patterns in stock and bond returns. This failure has sometimes been attributed to frictions, transaction costs or durability. If such frictions are important, they should primarily affect the higher frequency components of asset returns. The long-swings, or lower-frequency comovements should be less affected. Consequently if transaction costs are important, tests of the consumption based asset pricing model which concentrate on lower-frequency components may be more successful.Consumption (Economics) ; Stock - Prices ; Bonds
Guest Editors’ Introduction On Understanding Ethical Behavior and Decision Making
Behavioral ethics is an emerging field that takes an empirical, social scientific approach to the study of business ethics. In this special issue, we include six articles that fall within the domain of behavioral ethics and that focus on three themes—moral awareness, ethical decision making, and reactions to unethical behavior. Each of the articles sheds additional light on the specific issues addressed. However, we hope this special issue will have an impact beyond that of the new insights offered in these articles, by stimulating evenmore research in this burgeoning field
Propulsion System Modeling and Takeoff Distance Calculations for a Powered-Lift Aircraft with Circulation-Control Wing Aerodynamics
The computation of takeoff distance for powered-lift aircraft is complicated because of the coupling of aerodynamic performance (lift, drag and moment coefficients) with forward speed. Cal Poly has developed an analysis procedure to capture this coupling, and the development of this procedure is continuing. In the past year, Cal Poly has completed a Phase I NRA contract from the NASA for the configuration development and modeling of CESTOL aircraft. The primary objective of this contract was to identify an aircraft configuration in enough detail to proceed into a Phase II contract to design and construct a large scale wind tunnel model followed by a wind tunnel test to measure both aerodynamic performance and noise. Four aircraft configurations have been developed, and all but one of the configurations use circulation control wing aerodynamics (CCW) to produce powered-lift aerodynamic effect for the wing. The aircraft configuration selected for the Phase II contract makes extensive use of CCW to develop high lift aerodynamics for takeoff and initial climb and again for final descent and landing.
An additional goal for the Phase I project was the CFD modeling of the aerodynamics of a CESTOL aircraft, and to use the CFD results to develop a new aerodynamic meta-model. In addition, a meta-model for propulsion performance was to be developed and the two meta-models were to be integrated into an upgraded takeoff code written in MATLAB. These models all combined were to demonstrate an up-graded version of the Cal Poly takeoff performance procedure. However, at present, the aerodynamics meta-model is not yet complete and work will continue on into Phase II. Thus, no specific takeoff performance is demonstrated in this paper. However, in this paper details of the aircraft configurations are presented, the options available to proceed high pressure air to the wing slots to produce CCW aerodynamics are discussed, the propulsion metamodel is defined, the analysis procedure for the aerodynamics meta-model is discussed and the up-graded takeoff program is discussed
- …