Many research studies have focused on fire evacuation planning. However, because of the uncertainties in fire development, there is no perfect solution. This research proposes a fire evacuation management framework which takes advantage of an information-rich building information modeling (BIM) model and a Bluetooth low energy (BLE)-based indoor real-time location system (RTLS) to dynamically push personalized evacuation route recommendations and turn-by-turn guidance to the smartphone of a building occupant. The risk score (RS) for each possible route is evaluated as a weighted summation of risk level index values of all risk factors for all segments along the route, and the route with the lowest RS is recommended to the evacuee. The system will automatically re-evaluate all routes every 2 s based on the most updated information, and the evacuee will be notified if a new and safer route becomes available. A case study with two testing scenarios was conducted for a commercial office building in Tianjin, China, in order to verify this framework.

The increasing demand for monodispersed cross-linked polymers in high-quality applications requires continuous improvement in their preparation process. In this study, an appropriate amount of a chain transfer agent was added to a traditional crosslinking system, resulting in the preparation by one-step dispersion polymerization of cross-linked polystyrene (PS) microspheres with a particle size of 3.867 μm and a diameter coefficient of variation of 0.011. The particles were characterized using scanning electron microscopy (SEM) and an Ubbelohde viscometer. The results show that the tertiary dodecyl mercaptan (TDDM) chain transfer during nucleation increases the oligomer concentration, promotes the aggregation of the oligomers, increases the primary particle size, and reduces the cross-linking effect. This controls the volume of cross-linked chains in the primary particles, thus avoiding the problem of poor dispersion of the polymer microspheres due to the introduction of divinylbenzene (DVB). This study produces a preparation method for cross-linked microspheres.KEYWORDS chain transfer, cross-linking, monodisperse, one-step method | INTRODUCTIONMicron-sized polymer particles are widely used in the ink and coatings industries, in medical immunology, and in analytical chemistry due to their size. Some cutting-edge technologies such as packing materials for columns, conductive adhesives, spacers for display screens, and materials for biomedical analysis have very strict particle size distribution and cross-linking requirements. 1,2The most common methods for preparing micron-sized polymer spheres are seed emulsion polymerization and dispersion polymerization. However, seed emulsion polymerization is cumbersome, and the amounts of monomer and emulsifier are not easy to control, which reduces the industrial production efficiency and increases the production cost. 3 Dispersion polymerization is a relatively simple and traditional method for preparing monodisperse polymer latex particles because dispersion polymerization involves adding all the reagents to the reaction vessel at the beginning of the reaction. When the system is heated to the decomposition temperature of the initiator, the free radicals formed by the decomposition of the initiator react with the free monomers to form short chains. 4 When the short chains reach the critical length, they precipitate from the continuous phase, tangle with each other, and aggregate into nuclei. 5 Then, they further absorb the monomers and aggregate until they form stable polymer microspheres. 6 The operating process and mechanism of dispersion polymerization are relatively uncomplicated. Thus, dispersion polymerization is the preferred method for preparing cross-linked microspheres. However, it has been shown that the dispersion of the prepared cross-linked particles decreases after a critical amount of the cross-linking agent is added to the dispersion polymerization system. 7 For example, Tseng et al added less than 0.3 wt% divinylbenzene (DVB) to a system and obtained mon...

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In this research, monodispersed polystyrene (PS) microspheres were prepared by dispersion polymerization. PS microspheres decorated with silver nanoparticles (PS/Ag composite microspheres) were synthesized by a modified chemical plating method with water as the synthesis medium. The microspheres at each stage were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), UV–visible spectroscopy (UV–vis), field‐emission scanning electron microscopy (FESEM), and energy‐dispersive spectrometer (EDS). The reduction of methylene blue (MB) was carried out with PS/Ag composite microspheres as a catalyst and NaBH4 as a reducing agent. The results showed that the MB dye was reduced to colorless within 180 s. The reduction of the MB dye followed pseudo‐first‐order kinetics with an apparent rate constant (Kapp) value of 0.01425 s−1. Control experiments were also carried out by adding microspheres from each chemical plating pretreatment stage to the MB, without PS/Ag composite microspheres. The catalytic activity of the PS/Ag composite microspheres was high after five consecutive cycles of recovery, showing promising reusability. The catalytic activity of the prepared PS/Ag catalysts was superior to other catalysts for the reduction of MB.

The epidemic has caused heavy losses to the catering industry, and many catering enterprises have been forced to close or transform. In this study, through the investigation, we can understand the development status of the catering industry under the epidemic situation, what difficulties have been encountered, what measures have been taken, especially for the special period of the Spring Festival, whether there is any innovation. In the survey, the potential direction of the future upgrading of catering industry and the impact on other related industries are discussed. Our findings will help catering enterprises survive and operate better under the epidemic, realize their own transformation and upgrading, which will drive other related industries to reduce the negative impact of the epidemic as soon as possible.