Rheology of Cellulose/Alginic Acid Blends with 1-Allyl-3-Methylimidazolium Chloride as Solvent

In this study, cellulose/alginic acid blend solutions were prepared with 1-allyl-3-methylimidazolium chloride as solvent. The effect of cellulose/alginic acid blend ratios on the rheological properties was studied. It was found that the viscosity and dynamic modulus decreased with the increase of alginic acid ratio. And the calculated viscosity values, which were obtained from the log-additivity rule, are less than the experimental viscosity values. This may be caused by the hydrogen bonding interaction between cellulose and alginic acid, which is beneficial to the miscibility of the blends. In order to prove the rheological result, cellulose/calcium alginate films were prepared from the solution, the hydrogen bonding between cellulose and alginate were investigated, which was related to the good miscibility of the blend solutions. POLYM. ENG. SCI., 60: 243–249, 2019. © 2019 Society of Plastics Engineers     

文化的园林转译与表达—以焦作七贤园为例

正位于河南省西北部的焦作市,北依太行,南临黄河。长期以来,煤炭产业为焦作带来了持续的经济增长和长久的社会繁荣。然而,经过不断地开采,焦作的煤炭资源几近枯竭,环境也遭受了极大的污染。曾经辉煌的大小煤窑和矿山,成为焦作土地上难以愈合的疤痕。转型,成为焦作城市形象更新的重要课题。2017年9月,第十一届中国国际园林博览会在郑州召开。焦作作     

A tunable dynamic vibration absorber for unbalanced rotor system

A tunable dynamic vibration absorber for unbalanced rotor system which is made up of coil springs and magnetic spring is presented. The structure of the absorber is introduced and the stiffness tuning mechanism of the magnetic spring is explained. A finite element model of the rotor-absorber system was built and the influencing factors to the appearance of the absorber were studied numerically. Finally, experiments were carried out to verify the numerical results, and PID control strategy was tested. The numerical and experimental results show that the present absorber is effective for vibration suppression of an unbalanced rotor system, and the control strategy is effective.     

Investigation on the anti-reduction mechanism of Ti4+ in high dielectric constant system Ca0.9La0.067TiO3 by doping with Al2O3

Ca_0.9La_0.067TiO₃ (abbreviated as CLT) ceramics doped with different amount of Al₂O₃ were prepared via the solid state reaction method. The anti-reduction mechanism of Ti⁴⁺ in CLT ceramics was carefully investigated. X-ray diffraction (XRD) was used to analyze the phase composition and lattice structure. Meanwhile, the Rietveld method was taken to calculate the lattice parameters. X-ray photoelectron spectroscopy (XPS) was employed to study the valence variation of Ti ions in CLT ceramics without and with Al₂O₃. The results showed that Al³⁺ substituted for Ti⁴⁺ to form solid solution and the solid solubility limit of Al³⁺ is near 1.11 mol%. Furthermore, the reduction of Ti⁴⁺ in CLT ceramics was restrained by acceptor doping process and the Q × f values of CLT ceramics were improved significantly. The CLT ceramic doped with 1.11 mol% Al₂O₃ exhibited good microwave dielectric properties: ε_r = 141, Q × f = 6848 GHz, τ_f = 576 ppm/°C.     

Determination of a suitable index for a solvent via two-column extractive distillation using a heuristic method

The traditional approach to solvent selection in the extractive distillation process strictly focuses on the change in the relative volatility of light-heavy components induced by the solvent. However, the total annual cost of the process may not be minimal when the solvent induces the largest change in relative volatility. This work presents a heuristic method for selecting the optimal solvent to minimize the total annual cost. The functional relationship between the relative volatility and the total annual cost is established, where the main factors, such as the relative volatility of the light-heavy components and the relative volatility of the heavy-component solvent, are taken into account. Binary azeotropic mixtures of methanol-toluene and methanol-acetone are separated to verify the feasibility of the model. The results show that using the solvent with the minimal two-column extractive distillation index, the process achieves a minimal total annual cost. The method is conducive for sustainable advancements in chemistry and engineering because a suitable solvent can be selected without simulation verification.     

基于关键拓扑变动项辨识的调度操作潮流校核方法

为解决传统调度操作潮流校核中的有效性问题，定义了一种面向调度操作的关键拓扑变动概念，提出并实现了基于关键拓扑变动辨识的调度操作潮流校核方法。首先，剖析了调度操作安全校核的实施目的，围绕其运行断面潮流校验的校核目的，定义了面向调度操作的关键拓扑变动概念，并基于网络拓扑连接关系设计了其辨识方法。在此基础上，提出了基于关键拓扑变动项辨识的调度操作潮流校核方法，明确了其实施流程和要点。最后基于当前电网调度自动化系统实际，构建了其实施框架，并介绍了其在某电网的实施效益。     

Halogenation effect promoted low bandgap polymers based on asymmetric isoindigo unit with low energy loss

To optimize the energy levels of the structural framework of isoindigo polymers, a series of asymmetric isoindigo based low bandgap polymers with chlorine, fluorine and thiazole substituents was constructed and their optical, electrochemical and photovoltaic properties were comparatively evaluated for the impact of different substitutions. In comparison with the polymer based on 2,2'‐bithiophene and isoindigo unit (PTi) with non‐substituted bithiophene as the donor moiety, the highest occupied molecular orbital energy level for the newly synthesized polymers is significantly decreased, and in turn an improvement of the open‐circuit voltage (V_OC) is noted in the corresponding photovoltaic devices. More importantly, combined with a low bandgap of 1.32 eV, the energy losses (E_loss) could be reduced to 0.61 eV for polymer based on chlorinated 2,2'‐bithiophene and isoindigo unit (PCl). In addition, the halogen moieties are observed to be superior in device fabrication and give better values than the thiazole substituent. Both fluorinated and chlorinated polymer donors exhibited improved performance compared with the original polymer PTi. Consequently, this work not only presents the influence of different electron withdrawing substituents on the physicochemical and photovoltaic performance, but also backs the concept of how to reduce the energy loss via the heteroatom effect. © 2020 Society of Chemical Industry     

Designing fixed-time tracking consensus protocols for networked Euler-Lagrangian systems with directed graphs

Science China Technological Sciences - In this paper, a class of disturbed networked Euler-Lagrangian systems is investigated to track a general virtual signal under a general directed...     

Recycling of Polyethylene Bags into High-Strength Yarns Without Using Melt Processing

A critical issue facing mankind is how to effectively recycle plastic grocery bags. Currently, the most proven practice for bag recycling is to create numerous returning sites throughout the nation. However, the success is compromised by the voluntary nature of such activities. In this work, we investigate an alternative approach to bag returning, by diverting recycling activities directly to consumers or end users at home. Specifically, a simple process for converting waste bags into high-strength fibers and yarns is designed and tested in an experimental feasibility study. The results from tensile testing and thermal analysis demonstrate that by a combined process sequence of cutting, knotting, twisting, hot drawing, and heat setting, high-strength polyethylene yarns with mechanical properties comparable to those of melt-spun polyethylene fibers can be produced. Without the involvement of melt processing, yarns made of a waste high-density polyethylene grocery bag material were hot drawn and heat set to achieve a tensile strength of 330 MPa. Yarns with such ternacity are expected to find numerous applications in textile, flooring, and leisure products. This may open up a new paradigm in plastic bags recycling and allow part of the recycling burden to be shifted to local residential communities. POLYM. ENG. SCI., 60: 281–287, 2019. © 2019 Society of Plastics Engineers     

Toward an understanding of how red phosphorus and expandable graphite enhance the fire resistance of expandable polystyrene foams

Flame retardant expandable polystyrene (EPS) foams were prepared by coating method. Red phosphorus (RP) and expandable graphite (EG) were chosen as the flame retardants to be coated on the surface of expanded PS beads. By the presence of 33 phr RP/EG with a mass ratio of 1:1, the limiting oxygen index of EPS foam could reach up to 26.9%, with V-0 rating obtained in UL-94 test. The peak heat release rate could also decrease to 180.67 kW/m², which was 72.9% lower than that of neat EPS sample. Thermogravimetric analysis revealed an obvious increase of thermal stability and residue char amount by the presence of RP and EG. From the observation and analysis of char residue, it could be proposed that there existed a significant synergistic effect between RP and EG. RP could be oxidized and further react with graphite by the presence of oxygen at high temperature, forming isolated char layer and releasing nonflammable gases. Moreover, P radicals were generated at high temperature and could capture the radicals formed during the combustion of polystyrene and eliminate the burning chain reactions.