scholarly journals Deviation of Cup and Propeller Anemometer Calibration Results with Air Density

Energies ◽  
2012 ◽  
Vol 5 (3) ◽  
pp. 683-701 ◽  
Author(s):  
Santiago Pindado ◽  
Alfredo Sanz ◽  
Alain Wery
Keyword(s):  
Air Density ◽  
Propeller Anemometer

scholarly journals Elevational niche-shift migration: Why the degree of elevational change matters for the ecology, evolution, and physiology of migratory birds

The Auk ◽  
2021 ◽  
Author(s):  
Jessie L Williamson ◽  
Christopher C Witt
Keyword(s):  
Partial Pressure ◽  
Bird Species ◽  
Seasonal Migration ◽  
Critical Examination ◽  
Niche Shift ◽  
Migratory Connectivity ◽  
Migratory Species ◽  
Arterial Blood ◽  
Air Density ◽  
Elevational Migration

Abstract Elevational migration can be defined as roundtrip seasonal movement that involves upward and downward shifts in elevation. These shifts incur physiological challenges that are proportional to the degree of elevational change. Larger shifts in elevation correspond to larger shifts in partial pressure of oxygen, air density, temperature, and ultraviolet (UV) exposure. Although most avian examples of elevational migration involve subtle shifts that would have minimal impacts on physiology, shifts of any magnitude have previously been considered under the broad umbrella of “elevational migration”. Here, we consider extreme seasonal elevational movements (≥2,000 m), sufficient to shift the elevational dimension of the eco-climatic niche. Migratory bird populations typically maintain inter-seasonal stability in the temperature, precipitation, and elevational aspects of their climatic niches, a tendency that likely reflects genetic physiological specialization on environmental conditions such as atmospheric pressure. A shift of ≥2,000 m involves a ≥20% change in air density and oxygen partial pressure, sufficient to incur functionally impactful declines in arterial blood-oxygen saturation and require compensatory shifts in respiratory physiology. We refer to this phenomenon as elevational niche-shift migration (ENSM). In this review, we analyzed >4 million occurrence records to identify 105 populations, representing 92 bird species, that undergo complete or partial ENSM. We identified key ecological and evolutionary questions regarding the causes and consequences of ENSM. Our synthesis reveals that ENSM has evolved independently in at least 29 avian families spanning 10 orders. Nonetheless, ENSM is rare relative to other forms of seasonal migration, consistent with the general tendency of seasonal niche conservatism by migratory species and evolutionarily conserved elevational range limits. For many migratory species and populations, within-species patterns of migratory connectivity are not sufficiently understood to determine ENSM status. ENSM is distinguished by its scale within the broader phenomenon of elevational migration. Critical examination of ENSM illustrates fundamental constraints on the ecology and evolution of migration systems, topographical influences on geographic patterns of migratory connectivity, and the remarkable metabolic flexibility of certain bird species that allows them to occupy disparate elevations across different seasons.

scholarly journals AIR PRESSURE CONTROLLED MASS MEASUREMENT SYSTEM

2013 ◽  
Vol 24 ◽  
pp. 1360002
Author(s):  
RUILIN ZHONG ◽  
JIAN WANG ◽  
CHANGQING CAI ◽  
HONG YAO ◽  
JIN'AN DING ◽  
...  
Keyword(s):  
Measurement System ◽  
Pressure Range ◽  
Mass Measurement ◽  
Air Pressure ◽  
Air Density ◽  
Airtight Chamber ◽  
And Control ◽  
Automatic Mass ◽  
Pressure Controlled ◽  
Control Part

Mass measurement is influenced by air pressure, temperature, humidity and other facts. In order to reduce the influence, mass laboratory of National Institute of Metrology, China has developed an air pressure controlled mass measurement system. In this system, an automatic mass comparator is installed in an airtight chamber. The Chamber is equipped with a pressure controller and associate valves, thus the air pressure can be changed and stabilized to the pre-set value, the preferred pressure range is from 200 hPa to 1100 hPa. In order to keep the environment inside the chamber stable, the display and control part of the mass comparator are moved outside the chamber, and connected to the mass comparator by feed-throughs. Also a lifting device is designed for this system which can easily lift up the upper part of the chamber, thus weights can be easily put inside the mass comparator. The whole system is put on a marble platform, and the temperature and humidity of the laboratory is very stable. The temperature, humidity, and carbon dioxide content inside the chamber are measured in real time and can be used to get air density. Mass measurement cycle from 1100 hPa to 200 hPa and back to 1100 hPa shows the effective of the system.

scholarly journals Light-induced levitation of ultralight carbon aerogels via temperature control

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Reo Yanagi ◽  
Ren Takemoto ◽  
Kenta Ono ◽  
Tomonaga Ueno
Keyword(s):  
Carbon Nanotubes ◽  
Heat Capacity ◽  
Porous Materials ◽  
Temperature Control ◽  
Light Absorption ◽  
Carbon Aerogel ◽  
Carbon Aerogels ◽  
Halogen Lamp ◽  
Absorption Properties ◽  
Air Density

AbstractWe demonstrate that ultralight carbon aerogels with skeletal densities lesser than the air density can levitate in air, based on Archimedes' principle, when heated with light. Porous materials, such as aerogels, facilitate the fabrication of materials with density less than that of air. However, their apparent density increases because of the air inside the materials, and therefore, they cannot levitate in air under normal conditions. Ultralight carbon aerogels, fabricated using carbon nanotubes, have excellent light absorption properties and can be quickly heated by a lamp owing to their small heat capacity. In this study, an ultralight carbon aerogel was heated with a halogen lamp and levitated in air by expanding the air inside as well as selectively reducing its density. We also show that the levitation of the ultralight carbon aerogel can be easily controlled by turning the lamp on and off. These findings are expected to be useful for various applications of aerogels, such as in communication and transportation through the sky.

scholarly journals High-Energy Emissions Induced by Air Density Fluctuations of Discharges

2018 ◽  
Vol 45 (10) ◽  
pp. 5194-5203 ◽  
Author(s):  
C. Köhn ◽  
O. Chanrion ◽  
T. Neubert
Keyword(s):  
High Energy ◽  
Density Fluctuations ◽  
Air Density ◽  
Energy Emissions

scholarly journals Air Density Climate of Two Caribbean Tropical Islands and Relevance to Wind Power

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Xsitaaz Twinkle Chadee ◽  
Ricardo Marcus Clarke
Keyword(s):  
Wind Turbine ◽  
Electrical Energy ◽  
Dew Point ◽  
Energy Output ◽  
Small Island ◽  
Air Density ◽  
Wind Turbine System ◽  
Island State ◽  
The Difference ◽  
Small Island State

The standard air density of 1.225 kg m−3 is often used in determining the energy output of a wind turbine although the energy output is dependent on a site's air density. By using measurements of temperature, dew-point temperature, and pressure, we calculate the monthly air density of moist tropical climates at two sites in the small-island state of Trinidad and Tobago. In addition, we calculate the energy output of a BOREAS 30 kW small wind turbine using the 10 m level wind speed distribution extrapolated to hub height. The average air densities at Crown Point and Piarco were 1.156 kg m−3 and 1.159 kg m−3, respectively, and monthly air densities at both sites were at most 6% less than standard air density. The difference in energy output of the BOREAS 30 kW calculated using standard air density over that using the local site's air density could provide electrical energy for the continuous monthly operation of 6 light bulbs rated at 50 W at Crown Point and 4 light bulbs at Piarco. Thus, communities interested in implementing wind turbine technologies must use the local air density of the site when sizing a wind turbine system for its needs.

scholarly journals Abnormally High Power Output of Wind Turbine in Cold Weather: A Preliminary Study

2003 ◽  
Vol 9 (1) ◽  
pp. 23-33 ◽  
Author(s):  
Christophe Leclerc ◽  
Christian Masson
Keyword(s):  
Wind Turbine ◽  
Air Temperature ◽  
High Power ◽  
Power Output ◽  
Cold Weather ◽  
Air Density ◽  
High Power Output ◽  
Wind Velocities ◽  
Preliminary Study ◽  
Narrow Bands

According to popular belief, air temperature effects on wind turbine power output are produced solely by air density variations, and power is proportional to air density. However, some cases have been reported, all involving stall-controlled wind turbines, in which unexpected high power output was observed at very low temperatures.As a preliminary study, this article intends to quantify the influence of air temperature on the power production of the Tacke TW600 wind turbine installed in Tiverton, Ontario, Canada. Increases in power output due to air temperature variation are stratified by wind velocity, showing that these increases are below the theoretical limits of air density variations during operation in low winds and are comparable to and beyond those theoretical limits at higher wind velocities. At – 9°C and 0°C, narrow bands of power at distinct levels are observed in the stall regime of the turbine; they are typical of many stall phenomena observed on stall-controlled rotors, but these levels have been found to be independent of any parameters recorded.

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