scholarly journals Southern Hemisphere Meteor Stream Determinations

1975 ◽  
Vol 28 (5) ◽  
pp. 591 ◽  
Author(s):  
G Gartrell ◽  
WG Elford
Keyword(s):  
Southern Hemisphere ◽  
Continuous Wave ◽  
Radar System ◽  
Radio Observations ◽  
Meteor Stream ◽  
Long Period ◽  
Pulse Radar ◽  
Comprehensive Search ◽  
Meteor Trails ◽  
System Operating

Meteor orbits have been deduced from radio observations of meteor trails carried out at Adelaide (latitude 35� S.), using a combined multi-station continuous wave and pulse radar system operating at 27 MHz. Observations were made for one week each month during the period December 1968 to June 1969, and also during October 1969. The orbits of 1667 meteors have been determined down to a limiting radio magnitude of + 8. The data have been systematically searched for stream meteors, and the significance of minor associations has been appraised. Altogether 40� 4 % of the orbits were found to be associated with at least one other orbit, and 29� 8 % with two or more. Numerous minor streams with high inclination and low eccentricity have been found at deep, southern declinations from December to March, with little activity in this quarter during June and October. In addition to confirming several previously established cometary associations, a comprehensive search has indicated that 34 of the meteor associations found may be related to 17 comets. Associations between several long-period comets and low-eccentricity high-inclination streams appear to be indisputable, and they confirm the origin of at least some of the 'toroidal group' meteors, previously a matter of some doubt.

CW (Continuous Wave) Measurement System. Operating Manual

1982 ◽  
Author(s):  
J. E. Bridge ◽  
IV. Burns ◽  
Gagliano J. ◽  
Reinman G. A. ◽  
R. B.
Keyword(s):  
Measurement System ◽  
Continuous Wave ◽  
Wave Measurement ◽  
System Operating

scholarly journals Energetic and exergetic analyses of carbon dioxide transcritical refrigeration systems for hot climates

2015 ◽  
Vol 19 (3) ◽  
pp. 905-914 ◽  
Author(s):  
Farivar Fazelpour
Keyword(s):  
Carbon Dioxide ◽  
Heat Pumps ◽  
Climatic Conditions ◽  
Exergy Efficiency ◽  
Refrigeration System ◽  
Long Period ◽  
Operation Conditions ◽  
Scientific Papers ◽  
System Operating

In the last two decades many scientific papers and reports have been published in the field of the application of the carbon dioxide as a refrigerant for refrigeration systems and heat pumps. Special attention has been paid to the transcritical cycle. However, almost no papers discussed such cycles for hot climates, i.e., when the temperature of the environment is higher than 40?? during a long period of time. This paper deals with the energetic and exergetic evaluation of a CO2 refrigeration system operating in a transcritical cycle under hot climatic conditions. The performance and exergy efficiency of the CO2 refrigeration system depend on the operation conditions. The effect of varying these conditions is also investigated as well as the limitations associated with these conditions.

Seasonal Change in the Deep Atmosphere of Uranus, 1981 to 2012

2021 ◽  
Author(s):  
Mark Hofstadter ◽  
Alexander Akins ◽  
Byran Butler
Keyword(s):  
Southern Hemisphere ◽  
Late Summer ◽  
Circulation Pattern ◽  
Giant Planets ◽  
Radio Observations ◽  
Data Set ◽  
Time Line ◽  
Very Large Array ◽  
Planetary Scale ◽  
Water Cloud

<p>Our team is using radio observations of Uranus, collected with the Very Large Array (VLA) telescope, to track seasonal changes in the deep troposphere of Uranus between 1981 and the present.  We previously reported on changes between 1981 and 1994, as the Southern Hemisphere moved from mid- to late-summer (Hofstadter and Butler 2003, Icarus 165, https://doi.org/10.1016/S0019-1035(03)00174-X).  During that time, the distribution of opacity sources in the atmosphere (now thought primarily to be H<sub>2</sub>S) changed in such a way as to suggest an increase in the strength of the planetary-scale circulation pattern in the 5 to 50 bar region of the atmosphere.  More specifically, using wavelengths from 1 to 20 cm, we found that regions poleward of 45 degrees latitude in the Southern Hemisphere are significantly depleted in absorbers compared to more equatorial latitudes, down to a pressure of about 50 bars (which is near the top of where a liquid water cloud is expected to form).  This opacity distribution could be explained by a planetary-scale circulation pattern, with absorber rich air parcels moving upward in equatorial regions, being depleted in absorbers by condensation at higher altitudes, and then moving poleward and descending, keeping the pole depleted in absorbers.  We found that the opacity difference between the pole and equator increased between the 1980's and the 1990's, suggesting a strengthening of the assumed circulation pattern.  Radio observations by our group and others since 1994 have shown that the Northern Hemisphere is roughly symmetric with the Southern, and that smaller-scale latitudinal banding exists (e.g., Molter et al. 2020 https://arxiv.org/abs/2010.11154).  </p><p>We are currently analyzing additional Uranus data collected at the VLA, and will present results from a subset of those observations taken in 2012 (during Southern Fall).  We will also discuss plans for extending the time line to the present.  The complete data set will span half a uranian year, allowing all seasons to be observed.  We will also discuss how the composition and chemistry of the ice giant planets (Uranus and Neptune) differ from those of the gas giants (Jupiter and Saturn).</p>

scholarly journals Novel specular meteor radar systems using coherent MIMO techniques to study the mesosphere and lower thermosphere

2019 ◽  
Vol 12 (4) ◽  
pp. 2113-2127 ◽  
Author(s):  
Jorge Luis Chau ◽  
Juan Miguel Urco ◽  
Juha Pekka Vierinen ◽  
Ryan Andrew Volz ◽  
Matthias Clahsen ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Lower Thermosphere ◽  
Atmospheric Parameters ◽  
Angle Of Arrival ◽  
Independent Observations ◽  
Mesosphere And Lower Thermosphere ◽  
Meteor Trails ◽  
Transmitting Antenna ◽  
Mlt Region

Abstract. Typical specular meteor radars (SMRs) use one transmitting antenna and at least a five-antenna interferometric configuration on reception to study the mesosphere and lower thermosphere (MLT) region. The interferometric configuration allows the measurement of the angle-of-arrival (AOA) of the detected meteor echoes, which in turn is needed to derive atmospheric parameters (e.g., mean winds, momentum fluxes, temperatures, and neutral densities). Recently, we have shown that coherent MIMO configurations in atmospheric radars, i.e., multiple input (transmitters) and multiple output (receivers), with proper diversity in transmission can be used to enhance interferometric atmospheric and ionospheric observations. In this study we present novel SMR systems using multiple transmitters in interferometric configuration, each of them employing orthogonal pseudorandom coded transmitted sequences. After proper decoding, the angle of departure (AOD) of the detected meteor echoes with respect to the transmitter site are obtained at each receiving antenna. We present successful bistatic implementations of (1) five transmitters and one receiver using coded continuous wave (CW) (MISO-CW), and (2) five transmitters and five receivers using coded CW (MIMO-CW). The latter system allows simultaneous independent observations of the specular meteor trails with respect to the transmitter (AOD) and with respect to the receiver (AOA). The quality of the obtained results is evaluated in terms of the resulting mean winds, the number of detections and the daily diffusion trail vs. altitude behavior. We show that the proposed configurations are good alternatives to explore the MLT region. When combined with multi-static approaches, they can increase the number of meteor detections, thereby improving the quality of atmospheric estimates and allowing the measurement of new atmospheric parameters (e.g., horizontal divergence, vorticity), The use of multiple collocated transmitters for interferometric AOD determination makes building a multi-static radar network easier logistically, as only one receiver per receiving site antenna is sufficient.

scholarly journals A dataset of clinically recorded radar vital signs with synchronised reference sensor signals

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Sven Schellenberger ◽  
Kilin Shi ◽  
Tobias Steigleder ◽  
Anke Malessa ◽  
Fabian Michler ◽  
...  
Keyword(s):  
Continuous Monitoring ◽  
Continuous Wave ◽  
Vital Signs ◽  
Radar System ◽  
Tilt Table ◽  
Non Invasive ◽  
Impedance Cardiogram ◽  
Wave Radar ◽  
Reference Device ◽  
Sensor Signals

Abstract Using Radar it is possible to measure vital signs through clothing or a mattress from the distance. This allows for a very comfortable way of continuous monitoring in hospitals or home environments. The dataset presented in this article consists of 24 h of synchronised data from a radar and a reference device. The implemented continuous wave radar system is based on the Six-Port technology and operates at 24 GHz in the ISM band. The reference device simultaneously measures electrocardiogram, impedance cardiogram and non-invasive continuous blood pressure. 30 healthy subjects were measured by physicians according to a predefined protocol. The radar was focused on the chest while the subjects were lying on a tilt table wired to the reference monitoring device. In this manner five scenarios were conducted, the majority of them aimed to trigger hemodynamics and the autonomic nervous system of the subjects. Using the database, algorithms for respiratory or cardiovascular analysis can be developed and a better understanding of the characteristics of the radar-recorded vital signs can be gained.

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