RGB-T tracking involves the use of images from both visible and thermal modalities. The primary objective is to adaptively leverage the relatively dominant modality in varying conditions to achieve more robust tracking compared to single-modality tracking. An RGB-T tracker based on a mixed-attention mechanism to achieve a complementary fusion of modalities (referred to as MACFT) is proposed in this paper. In the feature extraction stage, we utilize different transformer backbone branches to extract specific and shared information from different modalities. By performing mixed-attention operations in the backbone to enable information interaction and self-enhancement between the template and search images, a robust feature representation is constructed that better understands the high-level semantic features of the target. Then, in the feature fusion stage, a modality shared-specific feature interaction structure was designed based on a mixed-attention mechanism, effectively suppressing low-quality modality noise while enhancing the information from the dominant modality. Evaluation on multiple RGB-T public datasets demonstrates that our proposed tracker outperforms other RGB-T trackers on general evaluation metrics while also being able to adapt to long-term tracking scenarios.

This paper reports an improved current-modulated cavity ring-down spectroscopy (CRDS) method. A vehicle-mounted device based on this method is used to carry out a field test of urban natural gas leak inspections. In the current-modulated CRDS of this paper, a direct current (DC) component of the laser current is constant, and only a modulation component is scanned for mode matching, and is to be turned off in order to stop the laser injection into the cavity. The feedback of matching points in the modulation component can be used to monitor a working state of the device, and help to increase the measurement frequency. The device exhibits a detection limit of 0.8 ppbv for CH4 in 60 s averaging time and a detection limit of 10 ppbv for C2H6 in 16 s averaging time. Measurement precision for 1ppmv CH4 standard gas is achieved as 7.9 ppbv@10 Hz, and for 1ppmv C2H6 standard gas, the measurement precision is achieved as 51.0 ppbv@10 Hz. A typical leak site finds the process is used to introduce the field test in Beijing. A leak site found during the field test has been repaired by the gas company.

Concise open-path continuous-wave cavity ring-down spectroscopy (CW-CRDS) with a bow-tie cavity structure is demonstrated in the single- and dual-optical-path experiments for multicomponent gas detection, e.g., greenhouse gas concentration evaluation in ambient air. Owing to its features of optical feedback suppression and small free spectral range (FSR), the bow-tie configuration shows its special advantages in the realization of both a compact arrangement and two counter-propagating non-interference optical paths. The minimum of the Allan deviation reaches $1.6\times {10}^{-10}{\mathrm{cm}}^{-1}$ for an integration time of 100 s, corresponding to the noise equivalent absorption coefficient of $1.6\times {10}^{-9}{\mathrm{cm}}^{-1}{\mathrm{Hz}}^{-1/2}$. The detection sensitivity of methane is deduced to be 0.9 ppbv with its absorption cross section of $1.48\times {10}^{-20}{\mathrm{cm}}^2/\text{molecule}$ in the 512 decays averaging mode. A wavelength-correction method is proposed to reduce by about 30% the uncertainty in the measurements caused by the deviation in the wavelength resonance between incident laser and ring-down cavity. The concentrations of greenhouse gases in ambient air are measured by the open-path CW-CRDS with the uncertainties of 0.02, 100, and 10 ppmv for ${\mathrm{CH}}_4$, ${\mathrm{H}}_2\mathrm{O}$, and ${\mathrm{CO}}_2$, respectively.

Spot overlapping acts as one of the main concerns in getting ideal results in the laser paint stripping operations. In order to describe the process of paint removal with repetitively pulsed lasers in a scanning scheme, a simplified three-dimensional numerical model is developed and demonstrated to be able to present paint stripping results obtained with movable laser pulses. The influences of spatial overlapping between neighboring pulsed laser spots on the thermal distribution and on the corresponding paint removal are discussed. A series of experiments is designed, and the results agree well with the numerical simulation. It is found that a spot overlapping ratio higher than 50% is able to give uniformly heated zones and hence leads to no paint residues within the stripped region. An experimental linear dependence of laser paint stripping depth on the incident laser energy density is also obtained and may provide a guide for the parameter selection in the laser paint removal operations.

We studied the influences of the number of sub-pulses within a burst on the surface morphology of Al thin films deposited by picosecond pulsed laser. It can be demonstrated that with an increasing number of sub-pulses within a burst, both the thin film morphology and the surface roughness are gradually improved. Several physical mechanisms are proposed to explain the reduction in the size of particulates inside and on the film surface. The burst mode not only alleviates the inherent particulates generation of ultra-short pulsed laser deposition also provides a higher degree of freedom in the tunability of the film surface.

An approach to achieve co-axial picosecond laser pulsed pair is proposed. Instead of introducing additional optical devices, this method involves the adjustment of switching-out dynamics in the regenerative amplification process. Experimental results concerning the dependence of laser output behavior on the duration of the quarter-wave voltage applied on the Pockels cell are reported. The influence of ablation mode (single pulse or double pulse) on the morphology of deposited Nickel-films is studied. A significant improvement in the surface morphology with the double-pulse mode is observed. Fewer nanoparticles are observed and the thin film appears to be smoother with lower roughness.