Accuracy Assessment on Drone Measured Heights at Different Height Levels

The advancement in unmanned aerial system (UAS) technology has made it possible to attain an aerial unit, commonly known as a drone, at an affordable price with increasing precision and accuracy in positioning and photographing. While aerial photography is the most common use of a drone, many of the models available in the market are also capable of measuring height, the height of the drone above ground, or the altitude above the mean sea level. On board a drone, a barometer is used to control the flight height by detecting the atmospheric pressure change; while a GPS receiver is mainly used to determine the horizontal position of the drone. While both barometer and GPS are capable of measuring height, they are based on different algorithms. Our study goal was to assess the accuracy of height measurement by a drone, with different landing procedures and GPS settings

Unjamming of Granular Packings due to Local Perturbations: Stability and Decay of Displacements

We study the mechanical response generated by local deformations in jammed packings of rigid disks. Based on discrete element simulations we determine the critical force of the local perturbation that is needed to break the mechanical equilibrium and examine the generated displacement field. Displacements decay as a power law of the distance from the perturbation point. The decay exponent and the critical force exhibit nontrivial dependence on the friction: Both quantities are nonmonotonic and have a sharp maximum at the friction coefficient 0.1. We find that the mechanical response properties are closely related to the problem of force-indeterminacy where similar nonmonotonic behavior was observed previously. We establish direct connection between the critical force and the ensemble of static force networks.Comment: 4 pages, 4 figure

Defending the Homeland: Historical Perspectives on Radicalism, Terrorism,and State Responses

Defending the Homeland is not about homeland defense as defined by the De- fense Department—the military defense of U.S. territory from external attack. Rather, what the editors provide is a wide-ranging examination of, first, how the United States has responded to a va- riety of internal and external threats over its history and, second, how soci- etal reactions to terrorism may unin- tentionally encourage the terrorist mind-set. The volume comprises nine academic essays from among those sub- mitted to the 2005 Senator Rush D. Holt History Conference at West Vir- ginia University

Evaluating Changes in Visible to Short-Wave Infrared Spectral Reflectance of Arctic Mosses in Response to Experimental Drying to Find the Best Predictors of Moisture Content

Mosses are a dominant understory component in the Arctic and because of sparse canopy cover, contribute to spectral signals used in remote sensing estimates of various ecologically important characteristics such as productivity, phenology, and vegetation mapping. However, little is known about their contributions to community level spectra or how moisture content influences those spectral signals. Unlike vascular plants, mosses cannot actively regulate moisture content and are highly susceptible to desiccation. Previous research has shown that moss reflectance is sensitive to tissue moisture content. Here, a lab-controlled drying experiment was conducted to identify the best spectral predictors of moisture content of moss as well as distinguishing characteristics of their spectral profile compared to vascular plants. Additionally, a pilot study tested whether moss could drive community-level reflectance in situ in response to short-term moisture changes. Significant changes in the near infrared and short-wave infrared regions of moss spectra were observed in response to moisture content fluctuations and could be used to determine moisture content. Moisture indices derived from spectral reflectance were able to predict moisture content with a high degree of certainty. The red edge inflection point and slope obtained from derivative spectra were found to be good distinguishing characteristics between moss and vascular plant spectra for the purpose of classification. Lastly, moisture content of moss was shown to significantly drive community-level spectra where moss and vascular plants were interspersed. These findings demonstrate the need to consider whether mosses are present in a spectrally mixed signal and to be aware of moisture content and its effects on overall spectra. Given the influence that both mosses and moss moisture have on overall spectra, incorporating this once semi-forgotten understory component will be critical for better predictions and modeling of the changing Arctic ecosystem

The non-linearity between <ln A> and <Xmax> induced by the acceptance of fluorescence telescopes

The measurement of the average depth of the shower maximum is the most commonly used observable for the possible inference of the primary cosmic-ray mass composition. Currently, different experimental Collaborations process and present their data not in the same way, leading to problems in the comparability and interpretation of the results. Whereas is expected to be proportional to in ideal conditions, we demonstrate that the finite field-of-view of fluorescence telescopes plus the attenuation in the atmosphere can introduce a non-linearity into this relation, which is specific for each particular detector setup

Extent of force indeterminacy in packings of frictional rigid disks

Static packings of frictional rigid particles are investigated by means of discrete element simulations. We explore the ensemble of allowed force realizations in the space of contact forces for a given packing structure. We estimate the extent of force indeterminacy with different methods. The indeterminacy exhibits a nonmonotonic dependence on the interparticle friction coefficient. We verify directly that larger force-indeterminacy is accompanied by a more robust behavior against local perturbations. We also investigate the local indeterminacy of individual contact forces. The probability distribution of local indeterminacy changes its shape depending on friction. We find that local indeterminacy tends to be larger on force chains for intermediate friction. This correlation disappears in the large friction limit.Comment: 5 pages, 6 figure

Examining the Factors of a Technology Professional Development Intervention

This article discusses technology integration literature used to guide the design and implementation of a technology professional development intervention (TPDI) for secondary education teachers. Qualitative multiple-case research methods were used to examine teachers’ perceptions of the TPDI factors to provide a deeper understanding of which factors teachers’ perceived to be beneficial to the quality of the TPDI. A content analysis methodology was used to compare teachers’ perceptions at two different phases throughout the study: • Phase 1: while participating in the TPDI and, • Phase 2: after transferring the knowledge and skills taught in the TPDI to teaching practice. The results demonstrated seven beneficial factors to include when designing technology curriculum for adult learners: relevant, learning, access, reactions, interactions, clear and easy, and instructor. While this study examined a specific TPDI, the instructional design incorporated factors rooted in constructivist design principles, making the implications of the findings relevant to the instructional design of technology learning environments for higher education and business environments

Current Care and Investigational Therapies in Achondroplasia.

The goal of this review is to evaluate the management options for achondroplasia, the most common non-lethal skeletal dysplasia. This disease is characterized by short stature and a variety of complications, some of which can be quite severe. Despite several attempts to standardize care, there is still no widely accepted consensus. This is in part due to absence of concrete data on the incidence of sudden unexplained death in infants with achondroplasia and the best investigation for ascertaining which individuals could benefit from foramen magnum decompression surgery. In this review, we identify the different options of care and management for the various orthopedic, neurologic, and respiratory complications. In parallel, several innovative or drug repositioning therapies are being investigated that would restore bone growth but may also prevent complications. Achondroplasia is the most common non-lethal skeletal dysplasia. It is characterized by short stature and a variety of complications, some of which can be quite severe. Despite several attempts to standardize care, there is still no widely accepted consensus. This is in part due to absence of concrete data on the incidence of sudden unexplained death in infants with achondroplasia and the best investigation for ascertaining which individuals could benefit from foramen magnum decompression surgery. In this review, we identify the different options of care and management for the various orthopedic, neurologic, and respiratory complications. In parallel, several innovative or drug repositioning therapies are being investigated that would restore bone growth but may also prevent complications