The end linking of difunctional poly(dimethylsiloxane) with trifunctional cross linkers in the bulk has been simulated with a computer. A random array of primary chains with a Gaussian end-toend distribution is generated in an image container on the computer. By joining chain ends at nearby junctions, inter-and intramolecular reactions occur in all species, allowing formation of cyclic structures of any size. At high extents of reaction, the sol components extracted from the spanning forest thus constructed consist of a substantial amount of cycles such as cyclic dimers. The effect of intramolecular reaction increases the extent of reaction by several percent for molecular weights in the range of thousands. Structural statistics of various types of network imperfections and the cycle ranks of the networks are reported. The gels obtained at complete conversions contain loop defects, their populations increasing with lower molecular weights of the prepolymers. The elastic activities of nonstoichiometric systems are compared and discussed.
Weak-to-strong confinement transition of semi-flexible macromolecules in slit and in channel J. Chem. Phys. 136, 024902 (2012) Communication: Quantum polarized fluctuating charge model: A practical method to include ligand polarizability in biomolecular simulations J. Chem. Phys. 135, 231101 (2011) Proton-driven spin diffusion in rotating solids via reversible and irreversible quantum dynamics JCP: BioChem. Phys. 5, 10B606 (2011) Proton-driven spin diffusion in rotating solids via reversible and irreversible quantum dynamics J. Chem. Phys. 135, 134509 (2011) Spectroscopy and thermochemistry of a jet-cooled open-shell polyene: 1,4-pentadienyl radical J. Chem. Phys. 135, 124306 (2011) Additional information on J. Chem. Phys. Sol-gel distributions at high conversions, simulated by computer with spatial constraints on the distribution of chain ends, are reported for end-linked tetrafunctional systems. The composition of the sol is found to be uniquely dependent upon the functionality f of the cross linker: for f = 4, it mainly consists of linear monomers and oligomers containing one saturated cross linker. The molecular weight distribution of the sol exhibits a shoulder at the trimer due to the relative abundance of the "bow-tie" molecule. The populations of various types of dangling ends and loop defects in the gel are given and discussed. Our simulations reveal empirically that the single-loop probability varies with the -3/8 power of the molecular weight of the prepolymers. The powerlaw dependence of the loop formation on chain length of the prepolymers and the nonrandom nature of the cross-linking reaction is discussed.
The random polycondensation of telechelic linear chains cured with triand tetrafunctional cross-linkers has been simulated. Calculations are done for both bulk and solution reactions; critical points are located by different methods, with results in good agreement with experiment. Critical exponents ß and 7 vary from system to system, with average values ß = 0.300 ± 0.024 and 7 = 1.77 ± 0.16. The average value C_/C+ = 13.58 ± 3.50 is slightly larger than that from standard percolation.
Nowadays, the virtual reality (VR) market has made significant strides. VR is widely used in different applications, and education and training are one of the leading areas which are expected to grow to US $2.2 billion in revenue by 2023. Mixed reality (MR) is also known as hybrid reality that encompasses both VR and augmented reality. It allows interaction and feedback from the users, which is particularly important to enhance the experience in teaching and learning. MR not only merges the real and virtual worlds into a new environment, which combines physical and digital content, but also allows users to interact with the digital content dynamically in real time. In support of teaching and training, MR technology has been applied in diverse manufacturing and industrial sectors to visualize the digital models. Nevertheless, most of these MR projects are mainly focused on users' experience. The effectiveness in comprehending product design is seldom investigated. Therefore, in this project, an MR application is developed for teaching product design to university students. The application is developed on the HoloLens system. A practicable application has been designed that allows students to visualize the geometry of 3-D objects as well as the exploded diagrams of selected components. The students can command the system through the command manual or can signal the system through gazing, gesturing, and voice to implement instructions. To investigate the effectiveness of the MR application in teaching product design, a pretest and a posttest of similar difficulties were designed to access students' abilities in five main areas: the ability of students in comprehending design, understanding product functions, visualizing 3-D geometry, understanding geometric relationship, and students' creativity. In the investigation, 45 students were participated in the tests. Experimental results show that the proposed design positively improves students' understanding in geometric relationships and creativity. In the future, more features will be added to the MR application to further improve students' abilities in learning and training in other aspects.
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