Correcting for digital image correlation speckle inversion at high temperature using color cameras.

Digital image correlation (DIC) is a popular, noncontacting technique to measure full-field deformation by using cameras to track the motion of an applied surface pattern. Because it is noncontacting, DIC can be performed for extreme temperature applications (e.g., hot-fire rocket testing of carbon composite rocket nozzles) under harsh conditions during which bonded gauges are damaged. Speckle pattern inversion is a phenomenon that sometimes occurs while performing high-temperature DIC. During speckle pattern inversion, portions of the surface pattern that were initially darker at room temperature (e.g., graphite) may emit more light due to blackbody radiation than the portions that were initially paler, thereby producing images in which the pattern appears inverted at high temperature relative to the initial pattern at room temperature. This phenomenon can prevent the correlation algorithm from being able to resolve the displacements between images. This work compares three methods to mitigate speckle pattern inversion: (A) the subtraction method, a recently-published technique in which two high-temperature images are subtracted to remove unwanted light; (B) the filtering method, a popular technique in which optical bandpass filters screen out unwanted light; and (C) the histogram rescaling method, a proposed new method that pairs a color camera with a blue light source and uses information from the green sensor of the camera to correct against inversion in the blue sensor through postprocessing. The histogram rescaling method is shown to successfully eliminate speckle pattern inversion and has the added advantages that it does not require quasi-static loading to be able to compensate for speckle pattern inversion, nor does it impose thick-glass distortions caused by the optical filter.

High speed ultraviolet digital image correlation (UV-DIC) for dynamic strains at extreme temperatures.

Digital Image Correlation (DIC) is a camera-based method of measuring full-field displacements and strains from the surface of a deforming object. It can be applied at any length scale (determined by the lenses) and any time scale (determined by the camera), and because it is non-contacting, it can also be used at temperatures much higher than can be withstood by bonded strain gauges. At extreme temperatures, materials emit light in the form of blackbody radiation, which can saturate the camera sensor. It has previously been shown that the emitted light can be effectively screened by using ultraviolet (UV) cameras, lenses, and filters; however, commercially available UV cameras are relatively slow, which limits the speed of combined UV-DIC measurements. In this study, a UV intensifier was paired with a high-speed camera, and its ability to perform UV-DIC at high temperature and high speed was investigated. The system was compared over three different experiments: (A) a quasi-static thermal expansion test at high temperature, (B) a vibration test at room temperature, and (C) the same vibration test repeated at high temperature. The system successfully performed DIC up to at least 1600 °C at frame rates of 5000 fps, which is more than 100 times faster than other examples of UV-DIC in the literature. In all cases, measurements made using the UV intensifier were much noisier than those made without the intensifier, but the intensifier enabled measurements at temperatures well above those which an unfiltered high-speed camera otherwise saturates.

Disseminated cryptococcosis and hemochromatosis: clues to diagnosis.

Hepatic cirrhosis, diabetes mellitus and iron overload can each independently predispose to cryptococcosis. Hereditary hemochromatosis leads to all three of these predispositions. This report is the case of a patient with chronic hepatitis B virus infection and cirrhosis, who had markedly elevated serum ferritin and 99% transferrin saturation, and developed a leukemoid reaction. Autopsy revealed disseminated cryptococcosis for which the leukemoid reaction was a clue and possible hereditary hemochromatosis of which elevated ferritin and transferrin saturation can be clues. Hereditary hemochromatosis is an important diagnosis clinicians should never miss because early treatment with phlebotomy can be life-saving. Disseminated cryptococcosis can be rapidly diagnosed with serum cryptococcal antigen test and is treatable.

Disseminated cryptococcosis and hemochromatosis: clues to diagnosis

Hepatic cirrhosis, diabetes mellitus and iron overload can each independently predispose to cryptococcosis. Hereditary hemochromatosis leads to all three of these predispositions. This report is the case of a patient with chronic hepatitis B virus infection and cirrhosis, who had markedly elevated serum ferritin and 99% transferrin saturation, and developed a leukemoid reaction. Autopsy revealed disseminated cryptococcosis for which the leukemoid reaction was a clue and possible hereditary hemochromatosis of which elevated ferritin and transferrin saturation can be clues. Hereditary hemochromatosis is an important diagnosis clinicians should never miss because early treatment with phlebotomy can be life-saving. Disseminated cryptococcosis can be rapidly diagnosed with serum cryptococcal antigen test and is treatable.