A new detection method of weak signal mixed in strong noise is proposed. The method includes theory scheme, hardware and software. It detects and processes signal by using the instrument magnifying technology and single-chip microcomputer control. By means of virtual instrumentation simulation and display, this design provides effective methods to detect µA-level weak signal in piezoelectric infrared detector. Through the experiment of simulate low frequency weak signal detection, the system fully reveals its practicality and superiority in the field of lower S/N signal detection.
Reversible addition fragmentation transfer (RAFT) polymerization is of key significance for its suitability for most monomer and well-studied reaction mechanism. Herein, a serial of mesoporous silica (MS) materials, including rod-liked and spherical SBA-15, spherical MCM-41, and MCM-48, were successfully synthesized and modified by silane coupling agent γ-aminopropyltriethoxysilane (KH550). The modified MS was utilized as a microreactor for reversible addition–fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) using a xanthate as a chain transfer agent and AIBN as an initiator. Note that modified MS had lower specific surface area and pore volume while maintained the original morphological structure. Owing to the confinement effects, poly(methyl methacrylate) (PMMA) prepared from internal mesoporous channels featured with higher molecule weight and initial thermal decomposition temperature than these from conventional RAFT polymerization. More importantly, the PMMA obtained from the spherical SBA-15 and modified MCM-48 exhibited the highest molecule weight. This work provided a novel approach to design of polymer microstructure for a wider application, such as in drug release.
A serial of mesoporous materials (MS), i.e., rod-liked and spherical SBA-15, spherical MCM-41 and MCM-48 were successfully synthesized and modified by silane coupling agent KH550 then utilized as a microreactor for reversible addition–fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) using a xanthate as a chain transfer agent and AIBN as an initiator. The structures, morphologies and properties of the obtained polymers and composites were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption and desorption, thermogravimetry analysis, gel permeation chromatograph, and hydrogen nuclear magnetic resonance. Results showed that compared with conventional MS, modified MS featured with lower specific surface area and pore volume while maintained the original morphological structure. Owing to confinement effects, PMMAs obtained from internal mesoporous channels featured with higher molecule weight and initial thermal decomposition temperature than these from conventional RAFT polymerization, especially, the PMMA obtained from the spherical SBA-15 and modified MCM-48 exhibited the highest molecule weight.
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