A tough double-network (DN) ion gel composed of chemically cross-linked poly(furfuryl methacrylate-co-methyl methacrylate) (P(FMA-co-MMA)) and physically cross-linked poly(vinylidene ...fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) networks with 80 wt % of ionic liquid (IL) was fabricated via a one-pot method. This ion gel exhibits excellent mechanical strength and considerable ionic conductivity, which can be used as a solid gel electrolyte. Upon an adjustment of the weight ratio of P(FMA-co-MMA) to P(VDF-co-HFP) and the content of the cross-linker, remarkably robust DN ion gel (failure tensile stress 660 kPa, strain 268%; failure compressive stress 17 MPa, strain 85%) was obtained. The high mechanical strength is attributed to the chemical/physical interpenetrating networks. The rigid chemically cross-linked P(FMA-co-MMA) network dissipates most of the loading energy, and the ductile physically cross-linked P(VDF-co-HFP) network provides stretchability for the whole gel. More importantly, the P(FMA-co-MMA) network is formed by dynamic covalent bonds that can undergo a thermally reversible reaction, giving the gel a unique and effective thermal healing capability. Furthermore, with the high content of IL, the DN ion gel possesses a high ionic conductivity of 3.3 mS cm–1 at room temperature, which is higher than those of most solid polymer electrolytes and comparable to those of commercial organic liquid electrolytes.
•A resolved coupling model to directly simulate interaction between two-phase fluids and irregularly shaped particles.•The irregularly shaped particles are modeled by multi-sphere clumps in DEM.•A ...number of benchmark cases are conducted and compared with experimental works.•A case study of dambreak wave impact on a rock pile demonstrates the model's potential to coastal engineering.
In this paper, we develop a resolved coupling model to simulate interaction between two-phase fluids and irregularly shaped particles by using Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM). The Volume of Fluid (VoF) method is introduced to solve two-phase fluids, and irregularly shaped particles are represented by multi-sphere clumps in DEM. The resolved CFD-DEM coupling approach calculates meso-scale flow around particles, and an integration scheme is proposed to directly calculate the fluid forces on multi-sphere particles without resorting to empirical drag force models. A number of benchmark cases are conducted, including a single particle settling in a two-phase fluid, settling of two particles, disk-shaped particles and irregularly shaped particles. The numerical simulations compare well with experimental works and previous studies, showing the accuracy of this model. Finally, a case study of dambreak wave impact on a rock pile demonstrates great potential to apply this model in coastal engineering.
A series of mesogen-jacketed liquid crystalline polymers (MJLCPs) with polysiloxane backbones have been synthesized by hydrosilylation of polymethylhydrosiloxane with styrenic derivatives. Their ...properties were studied in detail by a combination of 1H NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry, polarized light microscopy, wide-angle X-ray diffraction, scanning electron microscopy, and contact angle measurements. Wide-angle X-ray diffraction results indicated that these MJLCPs based on highly flexible polysiloxane main chain could also self-assemble into supramolecular columnar nematic or smectic liquid crystalline phases compared with structurally similar MJLCPs having a polyethylene backbone, but their liquid crystalline ranges were narrowed significantly. Low contact-angle values of the MJLCPs could be attributed to the fact that the polysiloxane backbones were embedded in mesogenic side chains, which also confirmed the mesogen-jacketed model for MJLCPs.
Nonmesogenic cyclic alkylidene terephthalate is directly connected to flexible polyethylene main chain at every second carbon atom via the phenyl ring to obtain a novel vinyl polymer, poly(alkylidene ...vinylterephthalate) (PAVT-n), where n (= 10−14 and 16) denotes the number of methylene groups in the side chain. When the molecular weight is large enough, stable hexagonal columnar phases are generated from melt by the PAVT-n polymers with n = 10−13, but not by those containing 14 or 16 methylene groups. Compared with its open-ring counterpart, i.e., poly(dialkyl vinylterephthalate) (PDAVT-n) with linear side chains, PAVT-n has a glass transition temperature (T g) over 100 °C higher, a much larger persistence length, and a much lower critical molecular weight to form a mesophase. In addition, PDAVT-n enters into isotropic liquid at T g and becomes ordered at temperatures well above T g, whereas PAVT-n forms mesophases immediately above T g. The strong steric interaction between cyclic pendants and the flexible main chain, which causes PAVT-n to take an extended chain conformation, is considered as the main driving force for PAVT-n to generate mesophases. In a sharp contrast, the mesophase formation of PDAVT-n is known to be an entropy-driven process.
To solve the key problems of tunneling and excavation, deformation and rupture of surrounding rocks in TBM tunnel model test research in deep composite stratum was conducted. This research employed a ...combined strategy of physical model test and numerical simulation for studying the deformation and fracture laws of the surrounding rock in a vertical section of a TBM tunnel in deep composite strata. In this study, the main research results are 1) The "soft and hard unevenness" and "combination effect" of the composite stratum affected the overall bearing capacity of the tunnel resulting in failure at a shallower buried depth or a lower stress concentration factor. 2) When the model was only excavated and unloaded, the plastic zone was basically near the periphery of the tunnel, resulting mainly in shear failure. In the lower layer of the composite stratum tunnel, the plastic zone due to its higher strength parameters was smaller than that in the upper layer. 3) Under the premise of the axial loading and surrounding constraints, the deformation and failure mode of the TBM tunnel in the deep composite strata exhibited "X"-type failure characteristics. The vertical section of the partially excavated rock mass revealed that the rock mass at the top layer of the tunnel caused a sudden and integral shear sliding of the palm face along the oblique direction upward 50°. This research provides significant and important guidelines for solving the problems of safety in TBM tunnel construction in a deep composite stratum.
Since the dynamic nature of human–robot interaction becomes increasingly prevalent in our daily life, there is a great demand for enabling the robot to better understand human personality traits and ...inspiring humans to be more engaged in the interaction with the robot. Therefore, in this work, as we design the paradigm of human–robot interaction as close to the real situation as possible, the following three main problems are addressed: (1) fusion of visual and audio features of human interaction modalities, (2) integration of variable length feature vectors, and (3) compensation of shaky camera motion caused by movements of the robot’s communicative gesture. Specifically, the three most important visual features of humans including head motion, gaze, and body motion were extracted from a camera mounted on the robot performing verbal and body gestures during the interaction. Then, our system was geared to fuse the aforementioned visual features and different types of vocal features, such as voice pitch, voice energy, and Mel-Frequency Cepstral Coefficient, dealing with variable length multiple feature vectors. Lastly, considering unknown patterns and sequential characteristics of human communicative behavior, we proposed a multi-layer Hidden Markov Model that improved the classification accuracy of personality traits and offered notable advantages of fusing the multiple features. The results were thoroughly analyzed and supported by psychological studies. The proposed multi-modal fusion approach is expected to deepen the communicative competence of social robots interacting with humans from different cultures and backgrounds.
•Human personality trait recognition from nonverbal cues in Human–Robot Interaction.•A framework for extracting visual features of human motion with robot camera motion compensation.•Multi-modal feature fusion approach to improving personality trait classification accuracy.•A multi-layer Hidden Markov Model for autonomous nonverbal feature selection.•Analysis (and interpretation) of experimental results, reflecting on psychological studies.
Three novel allyl–maleimide monomers (i.e., A2B, AB and AB2) were designed, synthesized and thermally cured to yield a series of high-performance allyl–maleimide resins. All the monomers obtained are ...readily soluble in common organic solvents enabling an easy solution processing. The thermal properties of the three monomers were studied by the differential scanning calorimetry (DSC). A2B and AB showed fairly low melting temperature (Tm<90°C) and wide processing window ranging from 90°C to 260°C. The thermal stability of the cured allyl–maleimide resins (i.e., PA2B, PAB and PAB2) was studied by the thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) was used to investigate the dynamic mechanical properties of the composites based on the cured allyl–maleimide resins. PA2B and PAB2 showed good glass transition temperatures (Tg>270°C) and their corresponding composites showed high bending modulus (E′>1900MPa). Allyl-compound-modified BMI resins based on AB monomer were prepared. Rheometer revealed that the processability of the prepolymer (BR–AB-pre) was improved by the addition of AB monomer. The cured BMI resins (BR and BR–AB) showed good thermal stability (Td>400°C, both in nitrogen and in the air), high glass transition temperature (Tg>320°C), and good mechanical properties and low water uptake (<2.6%, 120h).
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The phase structures and transition behaviors of a series of mesogen-jacketed liquid crystalline (LC) polymers, poly{2,5-bis(4-methoxyphenyl)oxycarbonylstyrenes} (PMPCS), with different molecular ...weights (MW) and narrow MW distributions were studied using differential scanning calorimetry, polarized light microscopy, Fourier transform infrared spectroscopy, and one- and two-dimensional wide-angle X-ray diffraction experiments. The LC phase structures of this series of PMPCS samples were found to be strongly MW dependent. The PMPCS samples were amorphous when the MW is lower than a critical MW of approximately 1.0 × 104 g/mol (an apparent MW, M n a, measured by gel permeation chromatography calibrated with the polystyrene standards). For the PMPCS samples with MWs higher than this critical value, the amorphous samples cast from solution developed into a LC phase above the glass transition temperature upon the first heating. In between 1.0 × 104 g/mol < M n a < 1.6 × 104 g/mol, a columnar nematic (ΦN) phase was stabilized. Above the M n a = 1.6 × 104 g/mol, a hexatic columnar nematic (ΦHN) phase was observed. Within these two LC phases, the building blocks were cylindrical shaped, which was attributed to a cooperative assembly of the PMPCS backbone and its laterally attached mesogenic groups. The diameter of this cylindrical building block was in the vicinity of 1.6 nm as determined by WAXD experiments. All the LC phases were found to be stable up to the decomposition temperature of the PMPCS samples. The MW dependence of the LC phase diagram indicated that a critical aspect ratio (the ratio between the length and diameter of the cylinders) of the cylindrical building blocks must be required to stabilize these LC phases. On the basis of Flory's calculation, the critical aspect ratio should be 5.44, and this value corresponded to critical cylinder lengths of around 8−9 nm. Therefore, the lowest degree of polymerization which would stabilize the LC phases is ∼39−42 for this series of PMPCS samples.
A series of non-mesogenic vinyl monomers, 2,5-bis(alkoxycarbonyl)styrene, were synthesized and polymerized via free radical polymerization. The alkoxy groups were systematically varied to investigate ...the effects of their size and architecture on the thermotropic liquid-crystalline properties of the resultant polymers. Although no traditional mesogen was present in the macromolecular structure, all the polymers revealed stable hexagonal columnar liquid-crystalline phase at the temperatures well above their glass transitions when the molecular weights were high enough, as evidenced by a combinatory analysis of differential scanning calorimetry, polarized light microscopy, and one- and two-dimensional wide-angle X-ray diffraction techniques. For the polymers containing five carbon atoms in the alkoxy terminals, the temperatures of glass transition and mesophase formation decreased and the d-spacing value of mesophase increased as the methyl substituent moved away from the connecting phenyl ring. Increasing the number of methyl group or the size of the substituent had the same effect. In the case of polymers with Y-shaped alkoxy terminals, the larger the side groups, the lower the glass-transition temperature and mesophase formation temperature and the larger the d-spacing value of mesomorphic structure.
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