RESUMEN
Digital shearography is a non-contact, whole-field, and high-accuracy laser-based optical interferometric method. It is widely used in the field of non-destructive testing and material evaluation. Dual-shearing DS, as the state-of-the-art method, can detect defects or measure the derivative of deformation in two sensitive directions. Most existing dual-shearing DS is realized with a bulky Michelson or Mach-Zehnder interferometer; recently, the usage of a spatial light modulator (SLM) in DS offers a new approach to designing a simple and light shearographic system. However, prior proposed SLM-based DS requires multiple shots for the phase map acquisition, with the classic temporal phase-shift (TPS) technique severely limiting its applications. This paper proposes a novel, to our best knowledge, one-shot dual-shearing DS by creating a dual-stripe pattern in the SLM. Two separate phase maps, with different sensitive directions, were acquired simultaneously via the spatial phase-shift technique. The measurement can be easily done within a single shot in its compact and light body. Moreover, the shearing amount of the two sensitive directions can be set independently and precisely. These advantages promote that the proposed system can be applied in various applications, especially for dynamic and complicated composite material testing. A detailed theory and experimental validation are described.
RESUMEN
To address the loss of measurement information caused by limitation of the field of view in fringe projection profilometry, a 3D full-field measurement based on imaging view transformation with a mirror auxiliary is proposed in this work. In this system, the principle of ideal specular reflection is applied to create a symmetrical structure between the real and virtual images for subsequent imaging view transformation. The phase of images is obtained by a multifrequency and multiple phase-shift sinusoidal fringe projection algorithm, and the real and virtual point clouds of measured objects are obtained by system calibration. The specular reflection matrix is obtained by calculating the relationship between virtual and real corner points. As a result, incomplete real point clouds can be compensated with virtual point clouds for the 3D full-field measurement by imaging view transformation. Compared to the standard ladder, the mean absolute error and the maximum relative error are 0.0706 mm and 0.9834%, respectively.
RESUMEN
BACKGROUND: Acupuncture is an effective way to relieve pain, but the mechanism by which electroacupuncture (EA) decreases the visceral pain state still remains unclear. This study aimed to evaluate the effects of pre-electroacupuncture on pain behaviors, p38 phosphorylation, and c-Fos protein and mRNA expression in both the colonic wall and spinal dorsal horn of rats suffering from visceral pain. This study also investigated the probable signaling regulatory mechanism of the analgesic effect induced by electroacupuncture. METHODS: All rats were randomized into the control (Con) group, the Con + EA group, the visceral pain (VP) group, and VP + EA group (n = 8 for all groups). The visceral pain model was established using 40 microl of 5% formalin solution injected into the colon of rats. EA was applied to the bilateral Jiaji acupoints for 20 minutes before application of visceral pain. Parameters for EA were set at a continuous wave (20 Hz) and intensity where the rats shook their whiskers but did not scrabble (< or = 1 mA). The visceral pain score was recorded and the expressions of p38 and c-Fos protein were detected using Western blotting. Real-time quantitative PCR was also used to determine the expression of c-Fos mRNA. RESULTS: Rats in the VP group immediately presented with obvious visceral pain behaviors after being injected with formalin. p38 activity and c-Fos protein and mRNA expression in both the colonic wall and spinal dorsal horn were higher in the VP group than in the Con group (P < 0.05). By contrast, visceral pain behaviors were delayed in rats from the VP + EA group. p38 activity and c-Fos protein and mRNA expression were lower in the VP + EA group than that in the VP group (P < 0.01). CONCLUSIONS: Pre-electroacupuncture of the Jiaji acupoint has prophylactic analgesic effects on rats suffering from visceral pain. The p38 signal transduction pathway may be partly involved in the regulatory mechanism of this analgesic effect.