The vapor-liquid equilibrium (VLE) properties for the binary and ternary mixtures of CH4, C2H4 and iso-C4H10 are of great importance in the recovery of ethylene from mixture containing CH4 and C2H4 with iso-C4H10 as solvent. Hence, Gibbs ensemble Monte Carlo (GEMC) simulations were used to estimate vapor-liquid equilibrium for the binary and ternary mixtures of CH4, C2H4 and iso-C4H10 with the united atom potential NERD model. The selected simulation conditions are based on the experiment in the literature. The results of this work were shown to be in satisfactory agreement with available experimental data and predictions of Peng-Robinson equation of state. The structure of simulated liquid phase is also characterized by radial distribution function (RDF), which contributes to further understanding of the VLE curve of these systems. RDF is not sensitive to the pressure and temperature range. With the increase of pressure or the decrease of temperature, the molecules tend to gather together.
The dipping method was devised to deposit Pd onto carbon nanotube as supported catalyst (Pd/CNT) for the copolymerization of carbon monoxide (CO) and styrene(ST) towards the formation of polyketone (PK). The Pd/CNT was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The construction and crystallization property of PK were evaluated by Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance(NMR) and XRD, respectively. The catalyst showed excellent activity and reusability in promoting the fabrication of PK. It can be recycled 14 times with the highest total catalytic activity of 4 239.64 gPK/ (gPd·h) at Pd content of 8.63wt%. The results indicate that the prepared catalyst is effective to catalyze the copolymerization of CO and styrene.
The pyrolysis behaviors of corn stalk (CS) and pine sawdust (PS) were investigated with thermogravimetry-mass spectroscopy (TG-MS). The peak temperature of PS was higher and the main decomposition region shifted to higher temperature compared with CS, which implied that the hemicellulose and cellulose of PS were more thermally stable than those of CS. However, the hemicellulose and cellulose of PS were more easily decomposed into gaseous products than those of CS during pyrolysis. The pyrolysis process of biomass can be described by a two-step independent first-order kinetic model. This fundamental study provides a basic insight into the biomass pyrolysis, which is beneficial for understanding the pyrolysis mechanism of biomass and developing an advanced thermal process for effective utilization of biomass.
In the present work, hierarchical nanostructured titanium dioxide (TiO2) films were fabricated on Ti-25Nb-3Mo-2Sn-3Zr (TLM) alloy for biomedical applications via one-step anodization process in ethylene glycolbased electrolyte containing 0.5wt% NH4F. The nanostructured TiO2 films exhibited three distinct types depending on the anodization time: top irregular nanopores (INP)/beneath regular nanopores (RNP), top INP/middle regular nanotubes (RNT)/bottom RNP and top RNT with underlying RNP. The evolution of the nanostructured TiO2 films with anodization time demonstrated that self-organizing nanopores formed at the very beginning and individual nanotubes originated from underlying nanopore dissolution. Furthermore, a mod`ified two-stage self-organizing mechanism was introduced to illustrate the growth of the nanostructured TiO2 films. Compared with TLM titanium alloy matrix, the TiO2 films with special nano-structure hold better hydrophilicity and higher specific surface area, which lays the foundation for their biomedical applications.
Microcapsules of volatile oil containing Herba Schizonepetae (VOHS) were prepared by emulsion solvent diffusion method to improve the drug loading and reduce the amount of pharmaceutical excipients. Orthogonal assay was applied to optimize the preparation condition of microcapsulation, and the results illustrated that the ratio of ethyl cellulose (EC) to VOHS influenced the property of VOHS microcapsule significantly. GC-MS analysis indicated that some volatile components with low concentration in VOHS were lost after microencapsulation. The microcapsules prepared with optimum condition had good fluidity, and the holes on the surface of the microcapsules contributed to the release of VOHS. The particles of the microcapsule conformed to a normal distribution with the diameter of 45–220 μm. In the simulated intestinal fluid containing 0.2% sodium dodecyl sulfate, pulegone in VOHS microcapsule showed a certain degree of slow release. Compared with β-cyclodextrin method, the microencapsulation used in the present work could reduce the amount of excipients and increase the drug loading. It was beneficial to reduce the dose of Chinese medicines containing volatile oils.
A droplet undergoes spreading, rebounding or splashing when it impacts solid boundary, which is a typical phenomenon of free surface flow that exists widely in modern industry. Smoothed particle hydrodynamics (SPH) method is applied to numerically study the dynamical behaviors of the droplet impacting solid boundary, and both the spreading and rebounding phenomena of the droplet are reproduced in the simulation. The droplet deformation, flow fields and pressure fields inside the droplet at different moments are analyzed. Two important factors, the initial velocity and diameter, are discussed in determining the maximum spreading factor, revealing that the maximum spreading factor increases with the increase of the impact velocity and droplet diameter respectively.
It is important and difficult to control the temperature of mass concrete structure during high arch dam construction. A new method with decision support system is presented for temperature control and crack prevention. It is a database system with functions of data storage, information inquiry, data analysis, early warning and resource sharing. Monitoring information during construction can be digitized via this system, and the intelligent analysis and dynamic control of concrete temperature can be conducted. This method has been applied in the construction of the Dagangshan Arch Dam in China and has proven to be very convenient. Based on the decision support of this system and the dynamic adjustment of construction measures, the concrete temperature of this project is well-controlled.
An example of using ultrasonic method to detect the compactness of complicated concrete-filled steel tube in certain high-rise building was discussed in this study. Because of the particularity of the complicated concrete-filled steel tubular column, the plane detection method and embedded sounding pipe method were adopted in the process of effectively detecting the column. According to the results of the plane detection method and embedded sounding pipe method, the cementing status of steel tube and concrete can be concluded, which cannot be judged by the hammering method in the rectangular steel tube-reinforced concrete.
Experiments were conducted using cohesionless sand particles with median diameter of 0.48 mm to investigate the time variation of sediment transport rate under the influence of local downward seepage. The experimental results show that the bedload transport rate in terms of volumetric sediment transport rate per unit width increased rapidly with time in the presence of suction, eventually reaching a peak beyond which it started to decrease. The trend of reduction was significantly reduced beyond 8 400 s after the test started. The analytical expression was derived in terms of dimensionless sediment transport rate and dimensionless time. The hypothesized relationships were compared with the experimental data, indicating a good agreement with each other.
In order to detect and assess the muscle fatigue state with the surface electromyography (sEMG) characteristic parameters, this paper carried out a series of isometric contraction experiments to induce the fatigue on the forearm muscles from four subjects, and recorded the sEMG signals of the flexor carpi ulnaris. sEMG’s median frequency (MDF) and mean frequency (MF) were extracted by short term Fourier transform (STFT), and the root mean square (RMS) of wavelet coefficients in the frequency band of 5–45 Hz was obtained by continuous wavelet transform (CWT). The results demonstrate that both MDF and MF show downward trends within 1 min; however, RMS shows an upward trend within the same time. The three parameters are closely correlated with absolute values of mean correlation coefficients greater than 0.8. It is suggested that the three parameters above can be used as reliable indicators to evaluate the level of muscle fatigue during isometric contractions.
A portable 4-channel electrochemical noise (EN) test system with high precision was developed. The modular instrument cRIO was used as its core and the signal conditioning module included zero resistance ammeter (ZRA), fly line, screening box and shielded wire. The EN data were acquired from two Q235 carbon steel specimens placed in 0.5 mol/L H2SO4 solution and 0.1 mol/L NaCl solution. The experimental result shows that this system can achieve an accuracy of 10 pA and 10 μV, and it can be applied to on-site multi-channel EN test.
The growth and evolution of the knowledge network in supply chain can be characterized by dynamic growth clustering and non-homogeneous degree distribution. The networks with the above characteristics are also known as scale-free networks. In this paper, the knowledge network model in supply chain is established, in which the preferential attachment mechanism based on the node strength is adopted to simulate the growth and evolution of the network. The nodes in the network have a certain preference in the choice of a knowledge partner. On the basis of the network model, the robustness of the three network models based on different preferential attachment strategies is investigated. The robustness is also referred to as tolerances when the nodes are subjected to random destruction and malicious damage. The simulation results of this study show that the improved network has higher connectivity and stability.