Enhancement of trace gas detectability using photoacoustic spectroscopy requires the effective suppression of strong background noise for practical applications. An upgraded infrared broadband trace gas detection configuration was investigated based on a Fourier transform infrared (FTIR) spectrometer equipped with specially designed T-resonators and simultaneous differential optical and photoacoustic measurement capabilities. By using acetylene and local air as appropriate samples, the detectivity of the differential photoacoustic mode was demonstrated to be far better than the pure optical approach both theoretically and experimentally, due to the effectiveness of light-correlated coherent noise suppression of non-intrinsic optical baseline signals. The wavelet domain denoising algorithm with the optimized parameters was introduced in detail to greatly improve the signal-to-noise ratio by denoising the incoherent ambient interference with respect to the differential photoacoustic measurement. The results showed enhancement of sensitivity to acetylene from 5 ppmv (original differential mode) to 806 ppbv, a fivefold improvement. With the suppression of background noise accomplished by the optimized wavelet domain denoising algorithm, the broadband differential photoacoustic trace gas detection was shown to be an effective approach for trace gas detection.

Received XX Month XXXX; revised XX Month, XXXX; accepted XX Month XXXX; posted XX Month XXXX (Doc. ID XXXXX); published XX Month XXXX A robust method and strategy for efficient full field-ofview and depth separation optical imaging through scattering media regardless of the three-dimensional (3D) optical memory effect are proposed. In this method, the problem of imaging de-aliasing, decomposition, and separation of speckle patterns are solved taking advantages of the spatial decorrelation characteristics of speckles by employing randomly modulated illumination strategy and independent component analysis methods. Full field-of-view imaging of multi-targets locate at diverse spatial positions behind a scattering layer are realized and observed experimentally, for the first time, to the best of our knowledge. The method and strategy provide a potentially useful means for incoherent imaging through scattering in a wide class of fields such as optical microscopy, biomedical imaging, and astronomical imaging.

A series of modified bentonite (MBT)/polyurethane (PU) composites were synthesized from MBT, isocyanate, and soybean oil-based polyols by in-situ polymerization to coat urea granules for slowing nitrogen (N) release. Bentonite (BT) was modified by intercalation of polyethylene glycol inside the interlayer space, expanded the BT layer spacing and improved the performance of composites. The MBT and MBT/PU composites were characterized in terms of their structure, thermal stability, mechanical strength, surface wettability, and the urea slow-release performance. With the addition of 5.0 wt% MBT, its tensile strength is 13.53 MPa and breaking elongation is 20.66%, increased by 27.52% and 67.97%, compared with pure PU, respectively. The release duration of the PU-5%-MBT composites coated urea was 74 days. The results indicated that the modified films are suitable for the slow release fertilizers. POLYM. COMPOS., 00:000-000,