Software-based analysis is one of the main methods for detecting and locating a leak from pipelines without the need for extensive instrumentation. However, software-based methods are generally sensitive to process disturbances, which cause the method to fail. In order to deal with these disturbances without increasing the number of measurements, an observer is designed for leak detection in natural gas pipelines as a case study. The proposed design implements a linear unknown input observer with time delays that considers changes of temperature and pressure as unknown inputs and includes measurement noise in the process. The unknown input observer found in the literature is modified for an application of leak detection. Nonisothermal modeling and simulation of a natural gas pipeline with time-variant consumer usage are performed to test the proposed method. Effects of pressure drop and temperature change on observer estimation are simulated and compared to a simulated leak event.
A novel magnetic polymer microsphere with amide groups and carboxyl groups was synthesized and reported here. The azidocarbonyl groups were derived from amide groups and linked to the proteins to investigate their immobilization capacity. The morphology, size, functional groups and magnetic properties of magnetic microspheres were characterized by optical microscopy, particle size analyzer, atom force microscopy, magnetic force microscopy, fourier transform infrared spectrometer, vibrating-sample magnetometer and thermal gravimetric analysis. The results indicated that the magnetic polymer microspheres had a well spherical shape with the size ranging from 1 to 10 lm, highly reactive functional groups, superparamagnetism and strong magnetic responsibility with saturation magnetization of 18.443 emu/g and Fe 3 O 4 content around 21%. The immobilization capacity (g) was over 70%. The novel azidocarbonyl magnetic polymer microspheres showed potentials to be a good magnetic support and promising applications in bioseparation and biomedical fields.
Poly(styrene-acrylamide-acrylic acid) copolymer fluorescent microspheres (PSAAFMs) with improved surface hydrophilicity were synthesized through an improved soap-free emulsion copolymerization method, in which the proportion of acrylamide on the surface of the microspheres was increased. Azidocarbonyl groups, which can be rapidly coupled with proteins under mild conditions, were introduced onto the PSAAFMs using an azido reaction. The PSAAFMs were characterized using a fluorescence microscope, an ultraviolet/visible spectrometer, a Fourier transforms infrared spectrometer, a transmission electron microscope (TEM), a size analyzer, and a fluorescence spectrophotometer. Furthermore, covalent linking through the azidocarbonyl groups and physical nonspecific attachments of bovine serum albumin (BSA), trypsin, and human chorionic gonadotropin (HCG) onto the surface of the microspheres were also determined to evaluate the influence of improved surface hydrophilicity on nonspecific protein adsorption. Results from the TEM and size analyzer showed that the PSAAFMs maintained spherical shapes with an average diameter of 2.5 ± 0.22 µm. Fluorescence measurement indicated that the maximum emission wavelength underwent a slight blue shift from 514 to 512 nm. Environmental factors, such as pH value, imposed certain effects on fluorescence intensities. The linear relationship between fluorescence intensity and microspheres' concentration, which ranged from 1 × 10−3 to 10 × 10−3 g L−1, suggest their quantitative application. The significant decrease in the physical nonspecific adsorption of BSA, trypsin, and HCG in comparison with the microspheres without improved hydrophilicity suggest the increased amount of acrylamide on the surface of the microspheres. The protein covalent immobilization experiments revealed significant increases in BSA and HCG immobilization in comparison with the nonspecific physical attachment. The combination of high hydrophilicity and electrostatic repulsion could severely inhibit nonspecific protein attachment onto the surface of the microspheres.
A novel two‐step modified seeded polymerization method for the preparation of AFDFMs with a core/shell structure is developed. Their morphology is characterized by means of TEM and SEM, further characteristics are studied using FT‐IR, fluorescence microscopy, laser confocal fluorescence microscopy, and fluorescence spectroscopy. TEM and SEM images provide clear proof of a core/shell structure. Fluorescence spectroscopy shows that AFDFMs exhibit tunable fluorescence characteristics with one or two emission wavelengths (515 and 575 nm) depending on the excitation wavelengths. Amido and carboxy groups on the AFDFM shell layer allow the formation of linkages with biomolecules for biological imaging or molecule detection, opening opportunities for biomedical applications.
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