Dynamic 3-D shape measurement using Fourier method

Fourier transform method has been widely sued on fringe analysis in optical metrology, including the structured illumination metrology and the interference metrology. The Fourier transform profilometry is one of the popular non-contact 3-D shape measurement methods, where a Ronchi grating or sinusoidal grating is projected onto a 3-D diffuse surface, and the resulting deformed grating image is detected by a CCD camera and processed by a computer. This method requires only one frame of the deformed fringe pattern to retrieve the surface of measured object, so it has obvious advantage for real-time data acquisition and 3-D measurement of dynamic process. In this paper, we review some dynamic 3-D shape measurement methods mainly proposed in our Lab based on Fourier fringe analysis, discuss some important problems, including sampling and frequency spectra overlapping, phase calculation, phase unwrapping, and 3-D reconstruction of dynamic process. When the measured dynamic object is spatially isolated or breaking into several isolated parts (e. g. an impact process), it will bring some difficulties for phase unwrapping. We embedded a special mark into the projected sinusoidal gratings to identify the fringe order, and at the same time the mark will not affect the Fourier spectra of the deformed fringe. In this paper we discuss some applications in the different fields. The applications include 3-D shape and deformation measurement of rotating object, the measurement for the vibrated shape, dynamic measurement of vortex shape, the 3-D shape measurement for breaking object surface and so on. With the development of computer hardware and software and availability of high frame rate CCD camera, the dynamic 3-D shape measurement using Fourier method will be a promising one for acquiring 3-D data of dynamic object

Effects of salinity and driving pressure on water imbibition during shale formation

During the construction stage of underground engineering projects, the engineering fluids used often carry a certain level of pressure, and rock formations in the subsurface invariably contain fluids with a certain degree of salinity. Both the driving pressure in engineering fluids and the high degree of salinity in the original subsurface fluids will inevitably impact the entire imbibition process; however, despite the high relevance to actual engineering situations, these effects have not been systematically studied in traditional researches on imbibition. In this study, imbibition experiments under varying engineering conditions, such as water salinity, driving pressure and initial water saturation, are conducted to detect the actual imbibition phenomenon in underground engineering projects. In addition, a modified Handy model considering the above three factors is proposed to better predict the imbibition law of shale under actual engineering conditions. The results show that salinity and driving pressure have significant effects on water imbibition, while the modified model, possessing exceptionally high fitting accuracy, effectively characterizes the forced imbibition patterns of shale. This study provides new insights into investigating fluid imbibition phenomena in the development stage of underground engineering.Document Type: Original articleCited as: Shao, X., Wang, K., Zhao, L., Su, C., Zhang, D., Gao, W. Effects of salinity and driving pressure on water imbibition during shale formation. Capillarity, 2024, 11(3): 70-80. https://doi.org/10.46690/capi.2024.06.0

Limits on light WIMPs from the CDEX-1 experiment with a p-type point-contact germanium detector at the China Jingping Underground Laboratory

We report results of a search for light Dark Matter WIMPs with CDEX-1 experiment at the China Jinping Underground Laboratory, based on 53.9 kg-days of data from a p-type point-contact germanium detector enclosed by a NaI(Tl) crystal scintillator as anti-Compton detector. The event rate and spectrum above the analysis threshold of 475 eVee are consistent with the understood background model. Part of the allowed regions for WIMP-nucleus coherent elastic scattering at WIMP mass of 6-20 GeV are probed and excluded. Independent of interaction channels, this result contradicts the interpretation that the anomalous excesses of the CoGeNT experiment are induced by Dark Matter, since identical detector techniques are used in both experiments.Comment: 5 pages, 5 figure

Host genetic background rather than diet-induced gut microbiota shifts of sympatric black-necked crane, common crane and bar-headed goose

IntroductionGut microbiota of wild birds are affected by many factors, and host genetic background and diet are considered to be two important factors affecting their structure and function.MethodsIn order to clarify how these two factors influence the gut microbiota, this study selected the sympatric and closely related and similar-sized Black-necked Crane (Grus nigricollis) and Common Crane (Grus grus), as well as the distantly related and significantly different-sized Bar-headed Goose (Anser indicus). The fecal samples identified using sanger sequencing as the above three bird species were subjected to high-throughput sequencing of rbcL gene and 16S rRNA gene to identify the feeding types phytophagous food and gut microbiota.ResultsThe results showed significant differences in food diversity between black-necked cranes and Common Cranes, but no significant differences in gut microbiota, Potatoes accounted for approximately 50% of their diets. Bar-headed Geese mainly feed on medicinal plants such as Angelica sinensis, Alternanthera philoxeroides, and Ranunculus repens. Black-necked cranes and Common Cranes, which have a high-starch diet, have a similar degree of enrichment in metabolism and synthesis functions, which is significantly different from Bar-headed Geese with a high-fiber diet. The differences in metabolic pathways among the three bird species are driven by food. The feeding of medicinal plants promotes the health of Bar-headed Geese, indicating that food influences the functional pathways of gut microbiota. Spearman analysis showed that there were few gut microbiota related to food, but almost all metabolic pathways were related to food.ConclusionThe host genetic background is the dominant factor determining the composition of the microbiota. Monitoring the changes in gut microbiota and feeding types of wild birds through bird feces is of great reference value for the conservation of other endangered species