Plane wave scattering from a rough surface with correlated large and small scale orders of roughness

Plane wave scattering from rough surface with correlated large and small scale orders of roughnes

Support for Instructional Leadership: Supervision, Mentoring, and Professional Development for U.S. School Leaders - Findings from the American School Leader Panel

With school leadership second only to teaching among school-related influences on student learning, principals can play an important role in school success. But how do their districts promote their effectiveness, especially in improving teaching? Based on a survey of the American School Leader Panel, a representative sample of principals from across the United States, this report explores the prevalence and quality of three important on-the-job supports for school leaders: supervision, mentorship and professional development (as defined by at least a day focused on principals). The good news is that two-thirds of principals report receiving some support. The bad news is that more than two thirds (68 percent) report that they don't receive all three sources of help. Mentoring, for example, is typically available only to first- or second-year principals or those encountering difficulties on the job, and only a minority of principals report that their districts require mentoring, even for first-year (49 percent of respondents) or struggling principals (21 percent). Also, the prevalence of support a principal receives may depend on the size of his or her school district. Both mentoring and professional development are more readily available in larger and medium-sized districts than smaller ones. The value principals place on the support they receive is linked to whether the support emphasizes the key aspect of principals' job—improving teachers' instruction. For example, all of the principals (100 percent) who reported that their mentors focused on instruction to a great extent also said that they prized the mentoring. That compares with a minority (40 percent) of principals who said their mentors devoted little to no time to instruction

The KSU Acoustic Simulator for Radar Studies

Equipment and instrumentation for acoustic simulation of electromagnetic wave propagation and radar systems design studie

Designing graduate training programs in conservation medicine-producing the right professionals with the right tools.

New challenges to human, animal, and ecosystem health demand novel solutions: New diseases are emerging from new configurations of humans, their domestic animals and wildlife; new pressures on once robust and resilient ecosystems are compromising their integrity; synthetic compounds and engineered organisms, new to the natural world, are spreading unpredictably around the globe. Globalization provides opportunities for infectious organisms to gain access to new hosts, changing in distribution and virulence. What type of training should be developed to provide professionals with the right tools to meet these challenges? In this article, we offer recommendations for developing academic programs in conservation medicine. We discuss the need for, and the advantages to, using a conservation medicine approach to address real world situations and present illustrations of how this is applied today. We suggest a core set of skills that are needed in a conservation medicine practitioner, and recommend key considerations for designing new conservation medicine training programs. We review existing programs that offer conservation medicine content, and provide examples of where opportunities exist for those interested in pursuing a conservation medicine career

Laser Doppler dust devil measurements

A scanning laser doppler velocimeter (SLDV) system was used to detect, track, and measure the velocity flow field of naturally occurring tornado-like flows (dust devils) in the atmosphere. A general description of the dust devil phenomenon is given along with a description of the test program, measurement system, and data processing techniques used to collect information on the dust devil flow field. The general meteorological conditions occurring during the test program are also described, and the information collected on two selected dust devils are discussed in detail to show the type of information which can be obtained with a SLDV system. The results from these measurements agree well with those of other investigators and illustrate the potential for the SLDV in future endeavors

Faster k-Medoids Clustering: Improving the PAM, CLARA, and CLARANS Algorithms

Clustering non-Euclidean data is difficult, and one of the most used algorithms besides hierarchical clustering is the popular algorithm Partitioning Around Medoids (PAM), also simply referred to as k-medoids. In Euclidean geometry the mean-as used in k-means-is a good estimator for the cluster center, but this does not hold for arbitrary dissimilarities. PAM uses the medoid instead, the object with the smallest dissimilarity to all others in the cluster. This notion of centrality can be used with any (dis-)similarity, and thus is of high relevance to many domains such as biology that require the use of Jaccard, Gower, or more complex distances. A key issue with PAM is its high run time cost. We propose modifications to the PAM algorithm to achieve an O(k)-fold speedup in the second SWAP phase of the algorithm, but will still find the same results as the original PAM algorithm. If we slightly relax the choice of swaps performed (at comparable quality), we can further accelerate the algorithm by performing up to k swaps in each iteration. With the substantially faster SWAP, we can now also explore alternative strategies for choosing the initial medoids. We also show how the CLARA and CLARANS algorithms benefit from these modifications. It can easily be combined with earlier approaches to use PAM and CLARA on big data (some of which use PAM as a subroutine, hence can immediately benefit from these improvements), where the performance with high k becomes increasingly important. In experiments on real data with k=100, we observed a 200-fold speedup compared to the original PAM SWAP algorithm, making PAM applicable to larger data sets as long as we can afford to compute a distance matrix, and in particular to higher k (at k=2, the new SWAP was only 1.5 times faster, as the speedup is expected to increase with k)

Integrable and Nonintegrable Classical Spin Clusters: Integrability Criteria and Analytic Structure of Invariants

The nonlinear dynamics is investigated for a system of N classical spins. This represents a Hamiltonian system with N degrees of freedom. According to the Liouville theorem, the complete integrability of such a system requires the existence of N independent integrals of the motion which are mutually in involution. As a basis for the investigation of regular and chaotic spin motions, we have examined in detail the problem of integrability of a two-spin system. It represents the simplest autonomous spin system for which the integrability problem is nontrivial. We have shown that a pair of spins coupled by an anisotropic exchange interaction represents a completely integrable system for any values of the coupling constants. The second integral of the motion (in addition to the Hamiltonian), which ensures the complete integrability, turns out to be quadratic in the spin variables. If, in addition to the exchange anisotropy also single-site anisotropy terms are included in the two-spin Hamiltonian, a second integral of the motion quadratic in the spin variables exists and thus guarantees integrability, only if the model constants satisfy a certain condition. Our numerical calculations strongly suggest that the violation of this condition implies not only the nonexistence of a quadratic integral, but the nonexistence of a second independent integral of motion in general. Finally, as an example of a completely integrable N-spin system we present the Kittel-Shore model of uniformly interacting spins, for which we have constructed the N independent integrals in involution as well as the action-angle variables explicitly

Glasslike Arrest in Spinodal Decomposition as a Route to Colloidal Gelation

Colloid-polymer mixtures can undergo spinodal decomposition into colloid-rich and colloid-poor regions. Gelation results when interconnected colloid-rich regions solidify. We show that this occurs when these regions undergo a glass transition, leading to dynamic arrest of the spinodal decomposition. The characteristic length scale of the gel decreases with increasing quench depth, and the nonergodicity parameter exhibits a pronounced dependence on scattering vector. Mode coupling theory gives a good description of the dynamics, provided we use the full static structure as input.Comment: 14 pages, 4 figures; replaced with published versio

Constraints on regional drivers of relative sea-level change around Cordova, Alaska

New records of paleoenvironmental change from two lakes near Cordova, south central Alaska, combined with analysis of previously reported sediment sequences from the adjacent Copper River Delta, provide quantitative constraints on a range of Earth system processes through their expression in relative sea-level change. Basal sediment ages from Upper Whitshed Lake indicate ice-free conditions by at least 14,140 – 15,040 cal yr BP. While Upper and Lower Whitshed Lakes provide only upper limits to relative sea-level change, interbedded layers of freshwater peat and intertidal silt extending more than 11 m below present sea level in Copper River Delta indicate net submergence over the last 6000 years and multiple earthquake deformation cycles. In contrast, Lower Whitshed Lake, situated just above present high tide level, records only one episode of marine sedimentation, commencing AD 1120 – 1500, that we interpret as the result of isostatic subsidence due to Little Ice Age mass accumulation of the Chugach Mountain glaciers. Lower Whitshed Lake also records isostatic uplift at the end of the Little Ice Age before the end of marine sedimentation caused by ~1.5 m coseismic uplift in the great Alaska earthquake of AD 1964. We successfully explain the records of relative sea-level change from both Copper River Delta and the Whitshed Lakes by integrating the effects of eustatic sea-level rise, glacial isostasy, earthquake deformation cycles, sediment loading, sediment compaction and late Holocene changes in glacier mass into a single model. This approach provides initial quantitative constraints on the individual contributions of these processes. Taking reasonable estimates of eustasy, post-Last Glacial Maximum and Neoglacial glacial isostatic adjustment and a simple earthquake deformation cycle, we demonstrate that sediment loading and sediment compaction are both contributors to relative sea-level rise at Copper River Delta, together producing subsidence averaging approximately 1.2 mm yr-1 over the mid to late Holocene. Further isolation basin studies have the potential to greatly improve our understanding of the individual contributions of these processes in this highly dynamic region

Classical Spin Clusters: Integrability and Dynamical Properties

A pair of exchange‐coupled classical spins with biaxial exchange and single‐site anisotropy represents a Hamiltonian system with two degrees of freedom for which the integrability question is nontrivial. We have found that such a system is completely integrable if the model parameters satisfy a certain condition. For the integrable cases, the second integral of the motion (in addition to the Hamiltonian), which guarantees integrability, is determined explicitly. It can be reconstructed numerically by means of time averages of dynamical variables over all trajectories. In the nonintegrable cases, the existence of the time averages is still guaranteed, but they no longer define an analytic invariant, and their determination is subject to long‐time anomalies. Our numerical calculation of time averages for two lines of initial conditions reveals a number of interesting features of such nonanalytic invariants