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The radio limb sounding or occultation technique is capable of deriving accurate vertical profiles of atmospheric refractivity. This has been shown by very promising results of the first active GPS limb sounding GPS/MET experiment on Microlab 1. In this paper we report early results of ionospheric radio occultation (IRO) measurements carried out onboard the German satellite mission CHAMP (CHAllenging Minisatellite Payload) that contributes also to essential improvements of gravity and magnetic field models of the Earth.  First radio occultation measurements of the ionosphere were carried out by CHAMP on 11 April 2001.  Fortunately, ionospheric radio occultation measurements were switched on during the High Rate GPS/GLONASS  measuring campaign (HIRAC) initiated by the International GPS Service (IGS) and supported by COST 271 activities. So a comprehensive analysis of coordinated measurements will be possible within COST 271 cooperation in the near future.  The achieved accuracy of the retrieved electron density profiles is estimated by comparing them with independent ionosonde data.

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Estimation of precipitable water vapor (PWV) in the atmosphere using ground based GPS (Global Positioning System) data requires an appropriate model for computation of zenith hydrostatic delay (ZHD). Presented herein is a site-specific ZHD model (SSM) for a station at New Delhi, India. The model has been developed by regressing one-year atmospheric vertical profile data collected through radiosonde. The model based on surface atmospheric pressure at the station, has been validated invoking data of three more years. The ZHD values estimated through the model disagree at the 0.3 mm level with ZHD values obtained from raytracing of radiosonde data. Further, Saastamoinen ZHD model provides an error about 0.23 mm rms while about 0.19 mm by the developed model (SSM). Thus, developed SSM can be used for precise estimation of PWV.

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Abu-Dabbab area is characterized by high seismicity and complex tectonic setting, for these facts, a local geodetic network consisting of eleven geodetic benchmarks has been established. The crustal deformation data in this area are collected using the GPS techniques. Five campaigns of GPS measurements have been collected, processed and adjusted to get the more accurate positions of the GPS stations. The horizontal velocity vectors, the dilatational, the maximum shear strains and the principal strain rates were estimated. The magnitude of the movements is distributed inhomogeneous over the area and it varies in average between 3 and 6 mm/yr. The results of the deformation analyses indicate a significant contraction and extension across the southern central part of the study area which is characterized by high seismic activity represented by the clustering shape of the microearthquakes that trending NE-SW direction. The north and north-eastern parts are characterized by small strain rates. This study is an attempt to provide valuable information about the present state of the crustal deformation and its relationship to seismic activity and tectonic setting at Abu-Dabbab area.

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Abstract  

Isomalt, a commercial sugar alcohol widely used as a sweetener, is approximately a 1:1 mixture of two diastereomers, -D-glucopyranosyl-1-6-mannitol (GPM) and -D-glucopyranosyl-1-6-sorbitol (GPS). A calorimetric investigation has been carried out on mixtures of isomalt with GPS, in the (molar) composition range 0.45<x GPS<1, for both crystalline and amorphous states.The GPS-rich portion of the solid-liquid GPM/GPS phase diagram was established and discussed in light of the existing literature. New evidence was given for the non-ideality of GPM/GPS mixtures, by indicating excess interactions in the melt and/or in the solid state. The commonly accepted hypothesis of a simple GPM/GPS eutectic forming isomalt was refuted in favour of more complicated mixture behaviour with possible formation of a complex.Glass transition and physical ageing of isomalt and GPS were re-visited, with peculiar attention given to the measurement conditions. Standard thermal histories were adapted to each sample and the fictive temperature was used for the characterisation of the structural glass states. A linear increase of the fictive temperature was found upon passing from pure GPS to x GPS=0.45. GPS showed a slightly higher enthalpy relaxation rate than isomalt.

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A Global Positioning System (GPS) permanent station has been established as a reference point at the Department of Civil Engineering of Indian Institute of Technology Bombay (IITB), by the IITB GPS group, and is continuously operating since January 2002. The station is being operated under a research project funded by the Department of Science and Technology (DST), Government of India, under the “National GPS Programme for Earthquake Studies”. A brief description of the station set up, the strategy used in determining its precise position, and some sample results are presented in this paper.

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The EGM96 geopotential model has been developed by NASA, NIMA and Ohio State University. By means of this model, the geoid undulation of a point can be calculated if its latitude and longitude are known in WGS84 datum. A local geoid solution TG99 for Turkey has been developed by the General Command of Mapping in order to obtain orthometric height from GPS observation for Turkey. In this study, geoid undulations of 75 points have been obtained in an area of about 1700 km2 between the latitudes 39º 39'-40º 06' and longitudes 32º 25'-32º 57' by using EGM96, TG99 and GPS/Leveling and results were then compared. Geoid undulation differences have been obtained in the range between -12.8 cm and 61.3 cm for EGM96 and GPS/Leveling comparison and -17.2 cm and 18.2 cm for TG99 and GPS/Leveling comparison.

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Abstract

Some ethical and practical aspects of the therapeutic use of placebos among Hungarian GPs (N = 94) were investigated in a questionnaire study. The majority of the responding GPs had already used placebos in their praxis. Placebo therapy was held effective on subjective symptoms by 52.7% of the responding physicians, and on both subjective and objective symptoms by 41.8%. The symptoms most commonly and successfully treated were anxiety, fatigue, sleep disorders and functional problems. GPs usually use vitamins, complementary medicines and sedatives as placebos. Most commonly, the therapy was considered ethically permissible if it was for the patient’s benefit (83.7%). Most of the physicians suggested formulating an official proposal on the therapeutic use of placebos to help in everyday medical practice. As recent research findings also support the efficacy of the placebo therapy in various conditions, its total prohibition clearly needs reconsideration.

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The effects of three geomagnetic storms on the ionospheric F region and the influence of the G condition on TEC estimates have been analysed by using ionospheric data from INTA El Arenosillo Atmospheric Sounding Station (37.1N, 353.3E) and GPS TEC measurements obtained at the IGS station of San Fernando (36.5N, 353.8E). The results stress the importance of these perturbations and the need of using edited ionograms.

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The ionosphere region plays an active role in the complex space weather relationships. So a permanent monitoring of the ionospheric state on global scale is required. The world-wide use of Global Navigation Satellite Systems (GNSS) such as GPS and GLONASS offer the unique chance for a permanent monitoring of the total ionization (Total Electron Content -- TEC) of the global ionosphere/plasmasphere up to about 20000 km height.  In this paper we focus on space weather phenomena on 6--7 April 2000 in the ionosphere based on GPS, GLONASS and ionosonde measurements over Europe and over the northern polar cap. Depending on the density of the actual ground station distribution the horizontal resolution of the derived TEC maps is in the order of 500--1000 km. While discussing the special space weather event on 6--7 April 2000 it will be shown that TEC is very sensitive to perturbation induced dynamic forces such as particle precipitation, electric fields and meridional thermospheric winds. We suppose that the strong impact on the magnetosphere/ionosphere systems is due to the southward direction of the interplanetary magnetic field in the evening hours of 6 April. The ionosphere impact on navigation signals is demonstrated by analyzing 1Hz sampled data of GPS and GLONASS satellites. The derived signal phase irregularities due to ionospheric irregularities that degrade navigation and positioning applications indicate highly variable horizontal  structures.

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Presented is a new operational model for real-time reconstruction of the vertical electron density distribution from concurrent GPS-based total electron content and ionosonde measurements. The model is developed on the basis of a novel approach for deducing the topside ion scale heights assuming Exponential, Epstein, or Chapman type of vertical density distribution. The required input data are submitted on-line to an operational centre where processing is carried out immediately and the electron density profile is derived. The method is suitable for use at middle and high latitude locations where ionosonde measurements are available. Several tests have been carried out and preliminary results have been presented and discussed.

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