ABSTRACT
Nanocomposite doping is an effective method to improve the dielectric properties of polyethylene. Meanwhile, the introduction of thermal conductivity groups in crosslinked polyethylene (XLPE) is also an effective way to improve the thermal conductivity. Nano-zeolite is an inorganic material with a porous structure that can be doped into polyethylene to improve the insulation performance. In this paper, hyperbranched polyarylamide (HBP) with a high thermal conductivity and an auxiliary crosslinking agent (TAIC) was grafted on the surface of ZSM-5 nano-zeolite successively to obtain functionalized nano-zeolite (TAICS-ZSM-5-HBP) (the "S" in TAICS means plural). The prepared functionalized nano-zeolite was doped in polyethylene and grafted under a thermal crosslinking reaction to prepare nanocomposites (XLPE/TAICS-ZSM-5-HBP). The structural characterization showed that the nanocomposite was successfully prepared and that the nanoparticles were uniformly dispersed in the polyethylene matrix. The space charge of the TAICS-ZSM-5-HBP 5wt% nanocomposite under a high electric field was obviously inhibited. The space charge short-circuit test showed that the porous structure of the nano-zeolite introduced more deep traps, which made the trapped charge difficult to break off, hindering the charge injection. The introduction of TAICS-ZSM-5-HBP particles can greatly improve the thermal conductivity of nanocomposites. The thermal conductivity of the XLPE/5wt% and XLPE/7wt% TAICS-ZSM-5-HBP nanocomposites increased by 42.21% and 69.59% compared to that of XLPE at 20 °C, and by 34.27% and 62.83% at 80 °C.
ABSTRACT
Tea plant is an economically important crop in China, but long-term monoculture and substantial chemical nitrogen fertilizer input cause soil acidification, which in turn affects the nutrient supply and tea quality. Intercropping has drawn more attention in tea gardens because this pattern is expected to improve soil fertility and tea quality and change the soil microbial community composition. However, the roles of some key microorganisms in rhizosphere soils have not been well characterized. Hereby, a "soybean in summer and smooth vetch in winter" mode was selected to investigate the effects of intercropped legumes in a tea garden on soil fertility, tea quality, and the potential changes in beneficial bacteria such as Bacillus. Our data showed that when soybeans were turned into soil, intercropping system exhibited higher soil organic matter (SOM), total nitrogen (TN), tea quality indices and the expression of Camellia sinensis glutamine synthetase gene (CsGS). Notably, intercropping significantly affected the bacterial communities and decreased the relative abundance of Bacillus but increased its absolute abundance. Bacillus amyloliquefaciens BM1 was isolated from intercropped soil and showed outstanding plant growth-promoting (PGP) properties when coinoculated with rhizobia. In winter, intercropping with smooth vetch had a beneficial effect on soil properties and tea quality. Comparably, coinoculation with strain BM1 and Rhizobium leguminosarum Vic5 on smooth vetch (Vicia villosa) showed huge improvements in SOM, TN and quality of tea leaves, accompanied by the highest level of amino acids and lowest levels of polyphenol and caffeine (p < 0.05). According to these results, our findings demonstrate that intercropping with some legumes in the tea garden is a strategy that increases SOM, TN and tea quality, and some PGP Bacillus species are optional to obtain an amplification effect.
ABSTRACT
The proposal of postural synergy theory has provided a new approach to solve the problem of controlling anthropomorphic hands with multiple degrees of freedom. However, generating the grasp configuration for new tasks in this context remains challenging. This study proposes a method to learn grasp configuration according to the shape of the object by using postural synergy theory. By referring to past research, an experimental paradigm is first designed that enables the grasping of 50 typical objects in grasping and operational tasks. The angles of the finger joints of 10 subjects were then recorded when performing these tasks. Following this, four hand primitives were extracted by using principal component analysis, and a low-dimensional synergy subspace was established. The problem of planning the trajectories of the joints was thus transformed into that of determining the synergy input for trajectory planning in low-dimensional space. The average synergy inputs for the trajectories of each task were obtained through the Gaussian mixture regression, and several Gaussian processes were trained to infer the inputs trajectories of a given shape descriptor for similar tasks. Finally, the feasibility of the proposed method was verified by simulations involving the generation of grasp configurations for a prosthetic hand control. The error in the reconstructed posture was compared with those obtained by using postural synergies in past work. The results show that the proposed method can realize movements similar to those of the human hand during grasping actions, and its range of use can be extended from simple grasping tasks to complex operational tasks.
