We review the history of experimental work on Rayleigh–Benard convection in gases, and then describe a modern apparatus that has been used in our experiments on gas convection. This system allows for the study of patterns in a cell with an aspect ratio (cell radius/fluid layer depth) as large as 100, with the cell thickness uniform to a fraction of a μm, and with the pressure controlled at the level of one part in 105. This level of control can yield a stability of the critical temperature difference for the convective onset of better than one part in 104. The convection patterns are visualized and the temperature field can be inferred using the shadowgraph technique. We describe the flow visualization and image processing necessary for this. Some interesting results obtained with the system are briefly summarized.

Apparatus for the study of Rayleigh–Bénard convection in gases under pressure

Thermal infrared (TIR) remote sensing is recognized as a powerful tool for collecting, analyzing and modeling of energy fluxes and temperature variations. Traditional aircraft, satellite or ground TIR platforms can provide valuable regional-scale environmental information. However, these platforms have limitations, such as expensive cost, complicated manipulation, etc. In comparison, small unmanned aircraft systems (UAS) have many advantages in TIR remote sensing applications over traditional platforms. In this paper, a low-cost UAV-based TIR remote sensing platform: AggieAir-TIR is introduced. AggieAir-TIR is a small, low-cost, flexible TIR remote sensing platform, which was accomplished at the Center for Self Organizing and Intelligent Systems (CSOIS) in Utah State University (USU). The detailed introduction of AggieAir-TIR remote sensing platform is provided in the paper. Furthermore, a low-cost TIR imaging camera calibration experiment is designed, and the calibration results are provided. Based on this AggieAir-TIR remote sensing platform, many remote TIR image data collection and analysis projects can be effectively implemented.

Low-cost UAV-based thermal infrared remote sensing: Platform, calibration and applications

In this article, we present a technical description of a new type of anemometer for gas and especially liquid flows with high temporal and spatial resolution. The principle of the measurement is based on the atomic force microscope technique where microstructured cantilevers are used to detect extreme small forces. We demonstrate the working principle and the design of the sensor, as well as calibration measurements and initial measurements of turbulent flows, which were performed in air and water flows.

Laser-cantilever anemometer: A new high-resolution sensor for air and liquid flows

UAV-borne thermal imaging involves the determination of ground surface temperature from thermal infrared measurements deploying an unmanned airborne vehicle (UAV). A large variety of UAVs is available and applied for different military and civil tasks. UAV-borne thermal imaging provides spatially distributed information of the ground surface temperature. In contrast to satellite or ground based measurement, the usage of a UAV allows us to obtain spatially distributed and geometrically highly resolved information on the ground surface temperature without the need to access the ground. The area can be flat or hilly, and steep walls and hillsides can be investigated easily. However, some problems, especially tasks related to mosaicking of the images, are not fully resolved to date. We address the detection of the anomalies in ground surface temperature induced by underground burning coal seams as example and describe the challenges and opportunities of UAV-borne thermal imaging, based on our experiences in this field.

Challenges and Opportunities for UAV-Borne Thermal Imaging

Presented here is an effective low-cost method for the temperature calibration of infrared cameras, for applications in the 0–100 °C range. The calibration of image gray level intensity to temperature is achieved by imaging an upwelling flow of water, the temperature of which is measured with a thermistor probe. The upwelling flow is created by a diffuser located below the water surface of a constant temperature water bath. The thermistor probe is kept immediately below the surface, and the distance from the diffuser outlet to the surface is adjusted so that the deformation of the water surface on account of the flow is small, yet the difference between the surface temperature seen by the camera and the bulk temperature measured by the thermistor is also small. The benefit of this method compared to typical calibration procedures is that, without sacrificing the quality of the calibration, relatively expensive commercial blackbodies are replaced by water as the radiative source (e≈0.98 for the wavelengths...

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A method for the temperature calibration of an infrared camera using water as a radiative source.

In conventional infrared (IR) thermographic cameras it is normally assumed that the ambient temperatures of optical objects are the same as the temperature determined at the camera head. In increasing cases of application of thermography, this assumption is not always satisfied, and often leads to erroneous results. In this article, we propose a determination scheme of the true temperature of such objects in an explicit form of equation to be solved by combining the readout temperature of the camera with a response function of the camera to a blackbody. The equation can be used to determine optical properties of components in an IR system. It also works to evaluate the contribution coming from each element along the optical path. Though the scheme is written in a form applicable to a specific camera among commercial products, it can be modified so that conventional IR cameras are conveniently used for thermographic determination of the temperature of gray objects in exotic environments.

Thermographic temperature determination of gray materials with an infrared camera in different environments

Examination is made of the relation between the distribution function of the ions confined in a tandem mirror and the current–voltage (I–V) characteristics of the end loss ions collected on a gridded energy analyzer To do this, a model ion distribution function characterized by two parameters, an anisotropy parameter χ and a decay parameter Y is used The decay parameter represents depletion of ion distribution in the loss cone A Maxwellian distribution as the limit of Y=∞ is shown not to reproduce the measured I–V curve as an energy spectrum of the ions lost from the central cell of the GAMMA 10 tandem mirror [Phys Rev Lett 55, 939 (1985)] The ions in the central cell are subject to strong ICRH and have a highly anisotropic velocity distribution These ions are deeply trapped in the central cell and the loss cone is not fully occupied The model distribution with a small value of Y represents such features of the ion distribution From comparison between a measured loss current and calculated one, 

M. Kurata

Papers

Thermographic temperature determination of gray materials with an infrared camera in different environments

Current–voltage characteristics of the end loss ion flux from a tandem mirror collected on a gridded energy analyzer