2,278 research outputs found
Spectrum Sharing Dynamic Protection Area Neighborhoods for Radio Astronomy
To enforce incumbent protection through a spectrum access system (SAS) or
future centralized shared spectrum system, dynamic protection area (DPA)
neighborhood distances are employed. These distances are distance radii, in
which citizen broadband radio service devices (CBSDs) are considered as
potential interferers for the incumbent spectrum users. The goal of this paper
is to create an algorithm to define DPA neighborhood distances for radio
astronomy (RA) facilities with the intent to incorporate those distances into
existing SASs and to adopt for future frameworks to increase national spectrum
sharing. This paper first describes an algorithm to calculate sufficient
neighborhood distances. Verifying this algorithm by recalculating previously
calculated and currently used neighborhood distances for existing DPAs then
proves its viability for extension to radio astronomy facilities. Applying the
algorithm to the Hat Creek Radio Observatory (HCRO) with customized parameters
results in distance recommendations, 112 kilometers for category A (devices
with 30 dBm/10 MHz max EIRP) and 144 kilometers for category B (devices with 47
dBm/10MHz max EIRP), for HCRO's inclusion into a SAS and shows that the
algorithm can be applied to RA facilities in general. Calculating these
distances identifies currently used but likely out-of-date metrics and
assumptions that should be revisited for the benefit of spectrum sharing.Comment: 6 pages, 5 figures, 5 tables, published to WCNC 202
Non-Intrusive Sensor for In-Situ Measurement of Recession Rate of Ablative and Eroding Materials
A non-intrusive sensor for in-situ measurement of recession rate of heat shield ablatives. An ultrasonic wave source is carried in the housing. A microphone is also carried in the housing, for collecting the reflected ultrasonic waves from an interface surface of the ablative material. A time phasing control circuit is also included for time-phasing the ultrasonic wave source so that the waves reflected from the interface surface of the ablative material focus on the microphone, to maximize the acoustic pressure detected by the microphone and to mitigate acoustic velocity variation effects through the material through a de-coupling process that involves a software algorithm. A software circuit for computing the location off of which the ultrasonic waves scattered to focus back at the microphone is also included, so that the recession rate of the heat shield ablative may be monitored in real-time through the scan-focus approach
Aging, cellular senescence, and progressive Multiple Sclerosis
Aging is one of the most important risk factors for the development of several neurodegenerative diseases including progressive multiple sclerosis (MS). Cellular senescence (CS) is a key biological process underlying aging. Several stressors associated with aging and MS pathology, such as oxidative stress, mitochondrial dysfunction, cytokines and replicative exhaustion are known triggers of cellular senescence. Senescent cells exhibit stereotypical metabolic and functional changes, which include cell-cycle arrest and acquiring a pro-inflammatory phenotype secreting cytokines, growth factors, metalloproteinases and reactive oxygen species. They accumulate with aging and can convert neighboring cells to senescence in a paracrine manner. In MS, accelerated cellular senescence may drive disease progression by promoting chronic non-remitting inflammation, loss or altered immune, glial and neuronal function, failure of remyelination, impaired blood-brain barrier integrity and ultimately neurodegeneration. Here we discuss the evidence linking cellular senescence to the pathogenesis of MS and the putative role of senolytic and senomorphic agents as neuroprotective therapies in tackling disease progression
A Robust Controller for Stable 3D Pinching using Tactile Sensing
This paper proposes a controller for stable grasping of unknown-shaped
objects by two robotic fingers with tactile fingertips. The grasp is stabilised
by rolling the fingertips on the contact surface and applying a desired
grasping force to reach an equilibrium state. The validation is both in
simulation and on a fully-actuated robot hand (the Shadow Modular Grasper)
fitted with custom-built optical tactile sensors (based on the BRL TacTip). The
controller requires the orientations of the contact surfaces, which are
estimated by regressing a deep convolutional neural network over the tactile
images. Overall, the grasp system is demonstrated to achieve stable equilibrium
poses on various objects ranging in shape and softness, with the system being
robust to perturbations and measurement errors. This approach also has promise
to extend beyond grasping to stable in-hand object manipulation with multiple
fingers.Comment: 8 pages, 10 figures, 1 appendix. Accepted for publication in IEEE
Robotics and Automation Letters and in IEEE/RSJ International Conference on
Intelligent Robots and Systems (IROS 2021). Supplemental video:
https://youtu.be/rfQesw3FDA
Ethnic identity, consumer ethnocentrism, and purchase intentions among bi-cultural ethnic consumers: "divided loyalties" or “dual allegiance”?
Consumer ethnocentrism has been studied extensively in international marketing in the context of one's country of residence. This paper investigates for the first time the notion of "dual ethnocentrism", which may be encountered among ethnic consumers who have an allegiance toward, or divided loyalties between, two countries: One with which they are ethnically linked, or "home", and one where they presently live and work, or "host". The study examines the relationship between ethnic identity, dual ethnocentrism, and purchase intentions among ethnic consumers, a market segment of growing importance in research and practice. The analysis focuses on differences in the respondents' home- and host-related ethnocentrism and finds that indeed ethnocentric feelings and their effects differ depending on the country of reference. In this light, the study suggests that ethnocentrism is a considerably more complex construct than previously thought, advances our understanding of ethnicity and ethnocentrism, and discusses the theoretical and managerial implications arising from dual ethnocentrism
Experiments on Surface Reconstruction for Partially Submerged Marine Structures
Over the past 10 years, significant scientific effort has been dedicated to the problem of three-dimensional (3-D) surface reconstruction for structural systems. However, the critical area of marine structures remains insufficiently studied. The research presented here focuses on the problem of 3-D surface reconstruction in the marine environment. This paper summarizes our hardware, software, and experimental contributions on surface reconstruction over the past few years (2008–2011). We propose the use of off-the-shelf sensors and a robotic platform to scan marine structures both above and below the waterline, and we develop a method and software system that uses the Ball Pivoting Algorithm (BPA) and the Poisson reconstruction algorithm to reconstruct 3-D surface models of marine structures from the scanned data. We have tested our hardware and software systems extensively in Singapore waters, including operating in rough waters, where water currents are around 1–2 m/s. We present results on construction of various 3-D models of marine structures, including slowly moving structures such as floating platforms, moving boats, and stationary jetties. Furthermore, the proposed surface reconstruction algorithm makes no use of any navigation sensor such as GPS, a Doppler velocity log, or an inertial navigation system.Singapore-MIT Alliance for Research and Technology. Center for Environmental Sensing and Modelin
Infrastructure for 3D model reconstruction of marine structures
3D model reconstruction of marine structures, such as dams, oil-rigs, and sea caves, is both important and challenging. An important application includes structural inspection. Manual inspection of marine structures is tedious and even a small oversight can have severe consequences for the structure and the people around it. A robotic system that
can construct 3D models of marine structures would hopefully reduce the chances of oversight, and hence improve the safety of marine environment. Due to the water currents and wakes, developing a robotic system to construct 3D models of marine structures is a challenge, as it is difficult for a robot to reach the desired scan configurations and take a scan of the environment while remaining stationary. This paper presents our preliminary work in developing a robotic and software system for construction of 3D models of marine structures. We have successfully tested our system in a sea water environment in the Singapore Straits
Phase II Study of Paclitaxel in Patients With Soft Tissue Sarcomas
Purpose. Patients with soft tissue sarcoma (STS) who have previously received standard chemotherapy including
adriamycin (doxorubicin), ifosfamide, cyclophosphamide and DTIC (dacarbazine) have very limited therapeutic options.
It is important to identify new drugs with some activity in this disease and we therefore undertook this trial to determine
the antitumor activity of paclitaxel (Taxol)
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