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Linear guides are essential components of precision equipment, such as computer numerical control machine tools and coordinate measuring machines. The key to improving their accuracy is to conduct high-precision measurements and effectively compensate for the six degrees of freedom errors that emerge during motion. However, the roll is a difficult parameter for achieving high-precision measurements in laser measurements, and it has yet to be effectively addressed. This study presents a high-precision and high-sensitivity roll measurement method based on the laser polarization state. The method employs a quarter-wave plate as the roll angle sensitive component. Firstly, the feasibility of this method was assessed through the Jones matrix and Zemax simulations. Subsequently, both theoretical and experimental analyses were conducted to evaluate the impact of using a corner cube reflector as a retroreflector on roll measurements. Finally, a corresponding measurement device was developed, and a series of comprehensive experiments were executed. The experimental findings indicate a measurement sensitivity of 7 mV/arcsec for this method. In comparison to commercial autocollimators, the contrast deviation within ± 100 arcsec is ± 1 arcsec. The repeatability of measurements on the air-floating guide rail is 1.3 arcsec, with a maximum contrast deviation of 2.5 arcsec compared to the electronic level. Thus, the proposed method offers the advantages of high precision, simple structure, and low cost and provides a new technique for high-precision roll measurement. [ABSTRACT FROM AUTHOR]

Railway transportation has experienced significant growth worldwide, offering numerous benefits to society. Most railway accidents are caused by wheelset faults so it's significant to monitor wheelset conditions. Therefore, we need to collect wheelset images, repaint them, extract laser stripe centerlines, construct 3D contour, and measure their geometric parameters to judge the wheelset's conditions. Deep learning can fulfill the tasks satisfyingly because it's adaptable, robust, and generalize compared with traditional methods. To train the deep learning models effectively, we need rich and high-quality wheelset datasets. So far, there are no applicable public train wheelset datasets available, which greatly hinders the research on train wheelsets. Thus we construct a publicly available Wheelset Laser Image Dataset (WLI-Set). WLI-Set consists of four sub-datasets, Original, Inpainting, Segmentation, and Centerline. The dataset contains abundant annotated multiline laser stripe images that can facilitate the research on train wheelsets effectively. [ABSTRACT FROM AUTHOR]

We report a tunable single-longitudinal-mode laser based on a wedged Nd:YVO4 gain medium and a YVO4 wave-plate. By taking advantage of the natural birefringence of YVO4 and adopting different cutting methods, a wedged Nd:YVO4 crystal acts as an ideal polarizer by the alignment sensitivity of the optical resonator, and a YVO4 crystal is used as a wave-plate by adjusting the temperature. A theoretical analysis of the single- longitudinal-mode operation of such a laser configuration is presented. The wavelength can be continuously tuned by the temperature at approximately 0.025 nm/°C, and the temperature tuning ranges of single-longitudinal-mode operation at pump powers of 1 W and 2 W are from 12 °C to 30 °C and from 11 °C to 26 °C, respectively. The maximum single-longitudinal-mode output power with linear polarization is 762 mW at a pump power of 2.2 W with a slope efficiency of 40%. [ABSTRACT FROM AUTHOR]

Error compensation has become an important means of improving the manufacturing and processing accuracy of computer numerical control (CNC) machine tools. Quick and precise measurement of the various geometric motion errors (GMEs) of CNC machine tools is crucial. We propose a novel laser method for the efficient and direct high-precision measurement of the 21 GMEs of a three-axis CNC machine tool, or three linear axes of a five-axis tool. A corresponding system was developed, comprising a fiber-coupled laser unit, sensor head, target unit, and beam-steering unit. The beam-steering unit was designed to perform high-accuracy 90° rotation of the measuring beam, and the target unit was designed to be sensitive to 18 GMEs of the three linear axes. Stability, repeatability, and comparison experiments were conducted to verify the performance of the proposed system. The results showed that the stability of the position error measurement is ± 6.3 nm. For straightness error measurement, the stability, repeatability error, and residual are within ± 60.3 nm, ± 0.5 μm, and ± 0.7 μm, respectively. These are within ± 0.12 arcsec, ± 0.5 arcsec, and ± 0.5 arcsec for the pitch and yaw measurements, and within ± 0.37 arcsec, ± 1.5 arcsec, and ± 1.0 arcsec for the roll measurements, respectively. For squareness error measurement, the repeatability error and residual are within ± 0.6 arcsec and ± 1.6 arcsec, respectively. Compared with a laser interferometer, the proposed system can measure the 21 GMEs of a three-axis machine tool with one-step installation. Without accuracy loss, the measurement efficiency is approximately 45 times higher than that of a laser interferometer, thus providing a new quick and accurate measurement method of GMEs and error compensation of CNC machine tools. [ABSTRACT FROM AUTHOR]

A broadband, nano-vibration measuring method based on the photoelectromotive force (photo-EMF) effect of semiconductor crystal is presented. A He-Ne-laser homodyne interferometer system is used as a light source and a GaAs crystal is used as a photodetector. The signal beam, which is modulated by the vibration, interferes with the reference beam, and a vibrating interference pattern is created on the surface of the GaAs crystal. Due to the photo-EMF effect, an alternating current signal, which relates to the vibration, is produced. We found the optimum parameters for the measurements by adjustments of the intensity ratio of the two beams, the angle between the beams and the interelectrode spacing on the GaAs crystal. The system can detect the vibration amplitude about several nanometers. The results of measurements of the vibrations of the PZT sample are well coincided with those obtained by TEMPO200 (Bossa Nova Technologies, America) system. [ABSTRACT FROM AUTHOR]

Purpose: Overuse of chemical fertilizer in agriculture has caused serious nitrogen (N) loss and water pollution problems in China. Biochar has the potential ability to reduce N loss and increase crop yield. However, there is still limited knowledge of the impacts of different biochars on N loss and crop yield over agriculturally relevant time frames. In this study, we compared the effects of amendment with bamboo biochar and rice straw biochar on the N retention and rice productivity in paddy fields, over an agriculturally relevant time span of 2 years. Materials and methods: A 2-year field study was conducted to investigate the effects of bamboo biochar and rice straw biochar amendment at a rate of 22.5 t ha (with or without urea) on N retention and rice growth. Total nitrogen (TN), ammonia (NH-N), and nitrate (NO-N) in soil and surface water were determined after biochar application. Stem lengths and rice yield were monitored during the experiment. Results and discussion: Amendment with rice straw biochar resulted in higher rice yields than in paddy soils that had bamboo biochar amendments. Incorporating rice straw biochar into a paddy field increased the rice yield by 19.8 % in 2009 and 21.6 % in 2010 without urea ( P < 0.05) and by 11.3 % in 2009 ( P < 0.05) and 14.4 % in 2010 with urea, compared with their corresponding control treatments. Although there were no significant impacts on the surface water N runoff potential, biochar amendment did result in a significant increase in the NO-N content of rhizosphere soil-121.2-135.7 % with urea and 89.7-102.2 % without urea, respectively, at the tillering stage in the first year ( P < 0.05). Conclusions: These results show that carbonizing rice straw residue into biochar and incorporating it into soil has the potential to enhance rice productivity and N retention in a paddy field. [ABSTRACT FROM AUTHOR]

Conversion of rice straw into biochar for soil amendment appears to be a promising method to increase long-term carbon sequestration and reduce greenhouse gas (GHG) emissions. The stability of biochar in paddy soil, which is the major determining factor of carbon sequestration effect, depends mainly on soil properties and plant functions. However, the influence of plants on biochar stability in paddy soil remains unclear. In this study, bulk and surface characteristics of the biochars incubated without rice plants were compared with those incubated with rice plants using a suite of analytical techniques. Results showed that although rice plants had no significant influence on the bulk characteristics and decomposition rates of the biochar, the surface oxidation of biochar particles was enhanced by rice plants. Using 13C labeling we observed that rice plants could significantly increase carbon incorporation from biochar into soil microbial biomass. About 0.047% of the carbon in biochar was incorporated into the rice plants during the whole rice growing cycle. These results inferred that root exudates and transportation of biochar particles into rice plants might decrease the stability of biochar in paddy soil. Impact of plants should be considered when predicting carbon sequestration potential of biochar in soil systems. [ABSTRACT FROM AUTHOR]