The first geocenter estimation results using GPS measurements

The center of mass of the Earth is the natural and unambiguous origin of a geocentric satellite dynamical system. A geocentric reference frame assumes that the origin of its coordinate axes is at the geocenter, in which all relevant observations and results can be referred and in which geodynamic theories or models for the dynamic behavior of Earth can be formulated. In practice, however, a kinematically obtained terrestrial reference frame may assume an origin other than the geocenter. A fast and accurate method of determining origin offset from the geocenter is highly desirable. Global Positioning System (GPS) measurements, because of their abundance and broad distribution, provide a powerful tool to obtain this origin offset in a short period of time. Two effective strategies have been devised. Data from the first Central and South America (Casa Uno) global GPS experiment were studied to demonstrate the ability of recovering the geocenter location with present-day GPS satellites and receivers

Deriving a geocentric reference frame for satellite positioning and navigation

With the advent of Earth-orbiting geodetic satellites, nongeocentric datums or reference frames have become things of the past. Accurate geocentric three-dimensional positioning is now possible and is of great importance for various geodetic and oceanographic applications. While relative positioning accuracy of a few centimeters has become a reality using very long baseline interferometry (VLBI), the uncertainty in the offset of the adopted coordinate system origin from the geocenter is still believed to be on the order of 1 meter. Satellite laser ranging (SLR), however, is capable of determining this offset to better than 10 cm, but this is possible only after years of measurements. Global Positioning System (GPS) measurements provide a powerful tool for an accurate determination of this origin offset. Two strategies are discussed. The first strategy utilizes the precise relative positions that were predetermined by VLBI to fix the frame orientation and the absolute scaling, while the offset from the geocenter is determined from GPS measurements. Three different cases are presented under this strategy. The reference frame thus adopted will be consistent with the VLBI coordinate system. The second strategy establishes a reference frame by holding only the longitude of one of the tracking sites fixed. The absolute scaling is determined by the adopted gravitational constant (GM) of the Earth; and the latitude is inferred from the time signature of the Earth rotation in the GPS measurements. The coordinate system thus defined will be a geocentric Earth-fixed coordinate system

Application of GPS tracking techniques to orbit determination for TDRS

In this paper, we evaluate two fundamentally different approaches to TDRS orbit determination utilizing Global Positioning System (GPS) technology and GPS-related techniques. In the first, a GPS flight receiver is deployed on the TDRSS spacecraft. The TDRS ephemerides are determined using direct ranging to the GPS spacecraft, and no ground network is required. In the second approach, the TDRSS spacecraft broadcast a suitable beacon signal, permitting the simultaneous tracking of GPS and TDRSS satellites from a small ground network. Both strategies can be designed to meet future operational requirements for TDRS-2 orbit determination

Law Enforcement Agencies in Disaster Response in Nepal: Analyzing the Competency of the Nepal Police and the Armed Police Force

Although Nepal Police and Armed Police Force are the key responding tools of disaster response in Nepal, their response competency does not suffice the need for effective response. Applying quantitative research methodology, this research has in-depth investigated the fundamental and technical knowledge, and preparedness activities of such police personnel. Ultimately it was discovered that their knowledge and preparedness are not adequate to meet the need. On the other hand, the practice of the usage of disaster untrained police personnel in response operations is prevalent in the country. And this tendency is not only risking the life of the disaster victims but also putting the responders’ lives at stake. Amidst such bleakness, during the investigation, the perception of the police personnel on their engagement in disaster response was found highly aspiring. Indeed this tendency will work as the force multiplier if their capacity is enhanced properly. The study has further investigated that the lethargic national investment in the disaster response capacity building process is the fundamental problem in terms of the competency building process. Heavy reliance on foreign aids and national and international non-government agencies has not only increased the dependency on capacity building process but also mired the national mechanism turning responsible authorities and institutions lethargic

Use of global positioning system measurements to determine geocentric coordinates and variations in Earth orientation

Geocentric tracking station coordinates and short-period Earth-orientation variations can be measured with Global Positioning System (GPS) measurements. Unless calibrated, geocentric coordinate errors and changes in Earth orientation can lead to significant deep-space tracking errors. Ground-based GPS estimates of daily and subdaily changes in Earth orientation presently show centimeter-level precision. Comparison between GPS-estimated Earth-rotation variations, which are the differences between Universal Time 1 and Universal Coordinated Time (UT1-UTC), and those calculated from ocean tide models suggests that observed subdaily variations in Earth rotation are dominated by oceanic tidal effects. Preliminary GPS estimates for the geocenter location (from a 3-week experiment) agree with independent satellite laser-ranging estimates to better than 10 cm. Covariance analysis predicts that temporal resolution of GPS estimates for Earth orientation and geocenter improves significantly when data collected from low Earth-orbiting satellites as well as from ground sites are combined. The low Earth GPS tracking data enhance the accuracy and resolution for measuring high-frequency global geodynamical signals over time scales of less than 1 day

Corrective saccades influence velocity judgements and interception

In daily life we often interact with moving objects in tasks that involve analyzing visual motion, like catching a ball. To do so successfully we track objects with our gaze, using a combination of smooth pursuit and saccades. Previous work has shown that the occurrence and direction of corrective saccades leads to changes in the perceived velocity of moving objects. Here we investigate whether such changes lead to equivalent biases in interception. Participants had to track moving targets with their gaze, and in separate sessions either judge the targets' velocities or intercept them by tapping on them. We separated trials in which target movements were tracked with pure pursuit from trials in which identical target movements were tracked with a combination of pursuit and corrective saccades. Our results show that interception errors are shifted in accordance with the observed infuence of corrective saccades on velocity judgments. Furthermore, while the time at which corrective saccades occurred did not afect velocity judgments, it did infuence their efect in the interception task. Corrective saccades around 100ms before the tap had a stronger efect on the endpoint error than earlier saccades. This might explain why participants made earlier corrective saccades in the interception task

A Study on Fish Classification Techniques using Convolutional Neural Networks on Highly Challenged Underwater Images

Underwater Fish Species Recognition (UFSR) has attained significance because of evolving research in underwater life. Manual techniques to distinguish fish can be tricky and tedious. They might require enormous inspecting endeavours, but they can be costly. It results in limited data and a lack of human resources, which may cause incorrect object identification. Automating the fish species detection and recognition utilizing technology would assist sea life science to evolve further. UFSR in wild natural habitats is difficult because the images open natural habitat, complex background, and low luminance. Species Visualization can assist us with deep knowledge of the movements of the species underwater. Automation systems can help to classify the fish accurately and consistently. Image classification has been emerging research with the advancement of deep learning systems. The reason is that the convolutional neural networks (CNNs) don't require explicit feature extraction methods. The vast majority of the current object detection and recognition mechanisms are based on images in the outdoor environment. This paper mainly reviews the strategies proposed in the past years for underwater fish detection and classification. Further, the paper also presents the classification of three different underwater datasets using CNN with evaluation metrics

EFFECT OF C-GLYCOSYL FLAVONE FROM URGINEA INDICA ON ANTIBIOTIC INDUCED MICROBIAL CELL DEATH

Objective: The aim of the present study was to isolate and characterize C-glycosyl flavone from Urgenia. indica bulb and to evaluate its effect on microbial cell growth.Methods: Methanolic extract of U. indica bulb was prepared using Soxhlation. Isolation was performed using silica gel column chromatography, and characterization was done based on IR, NMR and mass spectral data. The effect of C-glycosyl flavone was evaluated on microbial growth inhibition C-glycosyl flavone in terms of cytotoxicity, cell membrane damage, and cell death.Results: The results indicates that O-glycosyl flavanone (5,41-di hydroxyl-31-methoxy-7-O-[(α-L-rhamnosyl-(1[11]1-6[11])-β-D-glucopyranosyl)] flavanone), O-glycosyl flavone (5,41-dihydroxy-31-methoxy-7-O-β-D-glucopyranosyl flavone) and C-glycosyl flavone (5,7-dihydroxy-2-[41-hydroxy-31-(methoxymethyl) phenyl]-6-C-β-glucopyranosyl flavones) showed significantly sensitivity against Staphylococcus aureus, Bacillus subtilis, Rhizopus oryzae and Aspergillus niger. Synergism of C-glycosyl flavone on antibacterial activity of ciprofloxacin with the FIC index of 0.3 against S. aureus and 0.5 against B. subtilis. Antifungal activity of clotrimazole with the FIC index 0.3 against R. oryzae and 0.48 against A. niger. C-glycosyl flavone increased the ciprofloxacin-induced cytotoxicity from 63 to 91% against S. aureus and 56 to 89% against B. subtilis, whereas clotrimazole is induced cytotoxicity from 36 to 49% against R. oryzae and 23 to 41% against A. niger. C-glycosyl flavone increased the ciprofloxacin-induced cell death in S. aureus and B. subtilis and clotrimazole induced cell death in R. oryzae and A. niger as evident by propidium iodide staining, Tunel positive cells, and cytoplasmic membrane damage.Conclusion: The present investigation provides scientific and rationalism for the folkloric use of U. indica as an antimicrobial agent.Keywords: Antimicrobial, Synergism, Cytotoxicity, Cytoplasmic membrane damage and cell deathÂ

Simulation-based flood fragility and vulnerability analysis for expanding cities

Accurately quantifying flood-induced impacts on buildings and other infrastructure systems is essential for risk-sensitive planning and decision-making in expanding urban regions. Flood-induced impacts are directly related to the physical components of assets damaged due to contact with water. Such components include building contents (e.g., appliances, furniture) and other non-structural components whose damage/unavailability can severely impact the buildingsﾒ functionality. Conventional fragility analysis approaches for flooding do not account for the physical damage to the individual components, mostly relying on empirical methods based on historical data. However, recent studies proposed simulation-based, assembly-based fragility models that account for the damage to the building components. Such fragility models require developing detailed inventories of vulnerable components of households and identifying building archetypes to be considered in a building portfolio for the region of interest. Content inventories and building portfolios have so far been obtained for specific socio-economic contexts such as the United States of America. However, building types and their content can significantly differ between countries, making the available fragility models and computational frameworks unsuitable for flood vulnerability analysis in rapidly expanding cities characterised by extensive informal settlements, such as low- and middle-income countries. This paper details how to adapt the available methodologies for flood vulnerability assessment to the context of formal and informal settlements of expanding cities in the global south. It also details the development of content inventories for households in these cities using field surveys. The proposed survey is deployed in various areas vulnerable to floods in Kathmandu, Nepal. Based on the survey results, each component within the household is associated with a corresponding flood capacity (resistance) distribution (in terms of water height and flood duration). These distributions are then employed in a simulation-based probabilistic framework to obtain fragility relationship and consequence models. The relevant differences between the results obtained in this study and those from previous studies are then investigated for a case-study building type. In addition, the influence of socio-economic factors (e.g., household income) and past flood experience (possibly resulting in various flood-risk mitigation strategies at a household level) on the resulting flood impacts is also included in the model