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2.
Appl Opt ; 60(36): 11066-11074, 2021 Dec 20.
Article in English | MEDLINE | ID: mdl-35201095

ABSTRACT

When measuring the form deviation of the gear tooth flank with laser interferometry, due to the limitation of the depth of field of the lens, focused and defocused regions exist in the interferogram simultaneously. The introduced errors that were generated by these defocused regions decrease the measurement accuracy. Therefore, the evaluation of definition for interferograms is necessary for image processing. However, the gradient of gray, which performs by fringes, makes it difficult for traditional algorithms to evaluate its definition. This paper proposes a method based on nonsubsampled contourlet transformation (NSCT) combined with fringe direction as weighting coefficients to solve the problem. First, the information about the directions of these fringes in interferograms was evaluated. Then, the NSCT method was applied to interferograms so that several sub-images in different scales and directions can be achieved. Based on these sub-images and directions information, an improved function for definition evaluation was conducted. Lastly, a series of simulations and experiments was carried out to verify its feasibility and accuracy.


Subject(s)
Algorithms , Image Processing, Computer-Assisted , Image Processing, Computer-Assisted/methods , Interferometry
3.
Opt Express ; 28(12): 17881-17897, 2020 Jun 08.
Article in English | MEDLINE | ID: mdl-32679990

ABSTRACT

Phase unwrapping in regions of abnormal fringes remains an unresolved issue. In this paper, we present an approach that combines an image-inpainting strategy based on an adaptive window which is obtained according to the density and orientation of fringe patterns and a quality-guided algorithm for phase unwrapping. First, a threshold is set to a quality map to detect the target region. Second, the target region is filled with new phase values by the adaptive image-inpainting method. Then, a quality-guided phase unwrapping algorithm is applied to this newly generated wrapped phase map. Finally, postprocessing of the unwrapped result is performed. The method is validated through several simulation and experiments. The results demonstrate that the proposed algorithm is effective in the presence of abnormal fringes.

4.
Mol Ther Nucleic Acids ; 19: 827-840, 2020 Mar 06.
Article in English | MEDLINE | ID: mdl-31981860

ABSTRACT

Gastric cancer (GC) is one of the leading causes of cancer-related deaths worldwide. Accumulating evidence reveals the significance of long non-coding RNAs (lncRNAs) in various cancers. The current study aimed to evaluate the role of GATA6 antisense RNA 1 (GATA6-AS1) in the epithelial-mesenchymal transition (EMT) and lymph node metastasis (LNM) in GC. GC-related microarray datasets were initially retrieved from the GEO with differentially expressed lncRNAs screened, followed by evaluation of the regulatory relationship between Frizzled 4 (FZD4) and GATA6-AS1. The detailed regulatory mechanism by which GATA6-AS1 influences the Wnt/ß-catenin signaling pathway and GC cell biological behaviors was investigated by treating SGC7901 cells with overexpressed GATA6-AS1, specific antisense oligonucleotide against GATA6-AS1, and lithium chloride (LiCl; activator of the Wnt/ß-catenin signaling pathway). Finally, xenograft nude mice were used to assay tumor growth and LNM in vivo. GATA6-AS1 was poorly expressed, but FZD4 was highly expressed in GC tissues and cells. Elevated GATA6-AS1 reduced FZD4 expression by recruiting enhancer of zeste homolog 2 (EZH2) and trimethylation at lysine 27 of histone H3 (H3K27me3) to the FZD4 promoter region via the inactivated Wnt/ß-catenin signaling pathway, whereby cell invasion, migration, and proliferation, tumor growth, and LNM in nude mice were reduced. Taken together, overexpressed GATA6-AS1 downregulated the expression of FZD4 to inactivate the Wnt/ß-catenin signaling pathway, which ultimately inhibited GC progression.

5.
Sensors (Basel) ; 20(2)2020 Jan 09.
Article in English | MEDLINE | ID: mdl-31936564

ABSTRACT

In a high accuracy strapdown inertial navigation system (SINS), the ring laser gyroscope's (RLG) bias changes and the performance decreases due to factors in the RLG's self-heating and changes in ambient temperature. Therefore, it is important to study the bias temperature drift characteristics of RLGs in high, low, and variable temperature environments. In this paper, a composite temperature calibration scheme is proposed. The composite temperature model introduces the derivative term and the temperature derivative cross-multiplier on the basis of the static model and sets the overlap regions for the piecewise least squares fitting. The results show that the composite temperature model can compensate the bias trend term well at ambient temperature, improve the fitting accuracy, and smooth the output curve. The compensation method has a small amount of calculations and flexible parameter design. The precision of the laser gyros in one SINS is improved by about 64.9%, 15.7%, and 3.6%, respectively, which has certain engineering application value.

6.
Rev Sci Instrum ; 86(6): 065001, 2015 Jun.
Article in English | MEDLINE | ID: mdl-26133862

ABSTRACT

As common high-precision inertial sensors, quartz flexure accelerometers have a wide application prospect in low-cost inertial navigation systems. To ameliorate their resolution performance restricted by differential capacitance detection, we proposed a modified type of quartz flexure accelerometer based on an emerging optical technique named laser self-mixing interferometry, which is utilized to sense the displacement of a quartz pendulous reed, and then an equal and opposite force is accordingly produced to maintain the reed motionless relative to the inertial frame. The configuration and working principle of the improved accelerometer have been introduced and analyzed. The preliminary experiments indicate that its bias stability reaches 0.75-0.85 µg, which shows some progress when compared to the traditional type. Further improvements are mainly limited by the characteristics of the laser diode and the multiple reflections from the pendulous reed.

7.
Appl Opt ; 53(27): 6280-6, 2014 Sep 20.
Article in English | MEDLINE | ID: mdl-25322108

ABSTRACT

Self-mixing interferometry (SMI), as an extremely simple and compact laser range finding technique, is especially appropriate to develop minitype sensors for narrow space and small precision parts. In order to enhance the distance resolution performance of this technique, we described the mechanism of nonlinearity in laser frequency under injected current tuning, and proposed a current reshaping method to linearize the laser frequency to attain higher resolution in the scheme of SMI. The proof of nonlinearity was obtained through numerical simulation by considering the change of temperature and carrier concentration and experiment by complex wavelet analysis. The current reshaping method, based on the experimental data of wavelength versus injected current, was proposed to suppress the nonlinearity and improve the distance resolution to better than 20 µm over the range of 2.4-20.4 cm. The influence of tuning parameters and other sources of error was discussed additionally.

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