Search

Abstract [Objective] The study aims to investigate the effects of drought stress on the photosynthetic characteristics and anatomical structure of turnip (Brassica rapa) leaves, and to provide a basis for the selection and breeding of drought-resistant germplasm and the development of cultivation measures. [Methods] Drought-resistant and drought-sensitive turnip seedlings were selected for normal water-supply and drought-stress potting experiments to analyze the changes in leaf photosynthetic characteristics and anatomical structures. [Results] Drought stress reduced chlorophyll a, chlorophyll b, and total chlorophyll contents, net photosynthetic rate, stomatal conductance, transpiration rate, stomatal limiting values, as well as maximal fluorescence, variable fluorescence, maximal photochemical efficiency, and photochemical potential activity of turnip leaves, while the inter-cellular CO2 concentration, water-use efficiency, and initial fluorescence were increased, with greater variations in drought-sensitive germplasm. Drought also reduced leaf stomatal length, width, openness, density, and tissue laxity, while leaf thickness was increased. Drought also caused swelling of chloroplasts, blurring of basal lamellae, the appearance of cavities, and an increase in osmiophilic and amylopectin granules, while mitochondria were swollen and their internal cristae blurring, while the drought-sensitive germplasm was severely damaged. [Conclusion] Drought stress reduces stomatal opening and tissue structure laxity, increases leaf thickness, impaires the morphological structure of chloroplasts and mitochondria, and reduces the chlorophyll content and photosynthetic efficiency. The drought-resistant germplasm has stronger adaptive regulation to drought stress.

【Background and Objective】 Matrix-culture has been increasingly used in vegetable production, but continuous irrigation and fertilization could result in salinization and degradation of the matrix. The purpose of this paper is to experimentally study the impact of different combinations of irrigation and nitrogen (N) fertilization on water, salt and nitrogen dynamics in sandy matrix of cucumber, as well as its consequence for cucumber yield. 【Method】 The experiment was conducted in a greenhouse and consisted of seven treatments which were designed using the secondary saturated D-optimal design methods. Each treatment had three replicates. All treatments were drip-irrigated. During the experiment, we measured the moisture content, EC, nitrate and ammonium contents at four layers in the matrix after each 20 days, as well as cucumber yield in each treatment. 【Result】 The irrigation amount controlled water movement in the matrix, and the irrigation water moved downwards in most treatments. Mulching the matrix surface with a membrane can suppress the detrimental effect of salt to some extent, but avoiding excessive irrigation and N application is the best way to reduce salt accumulation in the matrix. Water flow took nitrate and ammonium to move with it in the matrix, and there was a threshold for ammonium below which the cucumber roots were unable to take up. The cucumber yield increased with irrigation and nitrogen fertilization parabolically: increasing first and then declining after the irrigation or fertilization exceeded a threshold. 【Conclusion】 On average, in terms of moisture content, the optimal water-nitrogen coupling is to set the upper and low soil moisture content in the matrix for irrigation at 80.20%~89.40% and 60%, respectively, N application at 623~917 kg/hm2. These not only ensure sufficient water and N to the crop, but also reduce the risk of water and N leaching and secondary salinization of the matrix.

Polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) is a standard electrolyte membrane and binder material for lithium‐ion batteries (LIBs) because of the benefits of membrane formation and strong mechanical properties. Still, its use is limited due to unavoidable defects such as high crystallinity and poor electrochemical performance. In this paper, a larger specific surface area and three‐dimensional (3D) permeable lamellae carboxylated g‐C3N4 (HCN) were successfully prepared by HNO3 and introduced into the PVDF‐HFP to obtain a high‐performance composite separator. The wettability and electrolyte absorption of PVDF‐HFP separator can be improved through the carboxylated HCN. More crucially, because PVDF‐HFP has several active sites and low crystallinity, adding HCN can greatly increase the ionic conductivity of separators. The ionic conductivity of PH‐HCN at 25 °C is 0.52 S cm−1, 4.7 times higher than the initial PVDF‐HFP membrane, and the oxidation potential can reach 4.8 V. The assembled lithium‐ion batteries half‐cell has a capacity of 71 % at a 5 C rate and 94 % after 400 cycles at a 2 C rate. Therefore, the improved separator has the potential to be applied to high‐performance LIBs. [ABSTRACT FROM AUTHOR]

Additive manufacturing has been developed for decades and attracts significant research interests in recent years. Usually, the stereolithography tessellation language format is employed in additive manufacturing to represent the geometric data. However, people gradually realize the inevitable drawbacks of the stereolithography tessellation language file format, such as redundancy, inaccuracy, missing of feature definitions, and lack of integrity. In addition, it is almost impossible to apply the simple polygonal facet representation to the five-axis manufacturing strategy. Hence, there are quite few researches and applications on the five-axis additive manufacturing, in spite of its common applications in the subtractive machining. This article proposes a feature-based five-axis additive manufacturing methodology to enhance and extend the additive manufacturing method. The additive manufacturing features are defined and categorized into two5D_AM_feature and freeform_AM_feature. A feature extraction method is proposed that can automatically recognize the additive manufacturing features from the input model. Specially for the freeform_AM_feature, a five-axis path planning method is proposed and split into three stages: (1) offset the reference surface, (2) spatially slice the freeform layers, and (3) generate the toolpaths for each freeform layer. Real additive manufacturing five-axis toolpaths can be obtained using the proposed algorithm that performs as a secondary developed plug-in in the CATIA® environment. A robotic additive manufacturing system is constructed for the implementation of the five-axis additive manufacturing tasks, which are generated by the proposed algorithms and post-processed after simulation and off-line programming. Some examples are printed to validate the feasibility and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]