多脉冲励磁下铁氧体及非晶磁环的磁特性

感应脉冲加速器的磁芯通常为铁氧体或非晶材料,而感应腔磁芯在工作脉冲下的磁性能是决定感应加速脉冲波形好坏的重要因素。搭建了低压多脉冲实验平台对铁氧体和非晶小磁环分别进行MHz重复频率的多脉冲励磁,对励磁线圈上的电压电流波形进行监测,绘制了多脉冲励磁下磁环的磁化曲线,并结合含磁芯线圈动态电感量的递推公式计算出磁环在多脉冲励磁过程中磁导率的变化曲线;在高压三脉冲实验平台上对铁氧体磁芯和非晶磁芯实验感应腔进行了高压三脉冲实验,得到的磁芯多脉冲磁化规律与低压实验的结果一致。最后对两种磁环在多脉冲励磁下的磁性能差异进行了对比分析。     

具有混合边界透水条件的多孔饱和半空间上刚性圆板的垂直振动

用积分变换和积分方程研究多孔饱和半空间上刚性圆板的垂直振动问题.首先应用逐次解耦方法求解多孔饱和固体的动力基本方程-Biot波动方程.然后考虑混合边界透水条件(半空间表面与圆板的接触面是不透水的,而其余表面是透水的),建立了多孔饱和半空间上刚性圆板垂直振动的对偶积分方程,并化对偶积分方程为第二类Fredholm积分方程.     

HL-2M 支撑系统制造工艺研究

在 HL-2M 装置支撑组件的研制中,采用了特制控氮不锈钢、结合 GMS310 焊丝和 Ar(96%)+N2(4%) 保护气体的焊接工艺以及低速和大进给量的机加方式把磁导率控制在≤1.03 的设计范围内。为保障 HL-2M 装置装 配时线圈系统的精确定位和安装,在研制阶段对极向场线圈支撑子系统进行了预装。     

聚吡咯/聚苯乙烯混合膜/电解质溶液体系的介电谱解析——电解质种类和浓度对膜透过性的影响

测量了混入聚吡咯粒子的聚苯乙烯混合膜在不同浓度的氯化钠、氯化钾、氯化钙及氯化镁体系的介电谱, 在40 Hz~11 MHz, 发现了显著的双介电弛豫现象(Double-relaxation phenomena). 基于Maxwell-Wagner理论讨论了弛豫产生的机制, 将体系进行了模型化, 并利用Hanai理论方法对介电谱进行了解析, 从获得的内部参数对混合后的膜荷电性质以及混合膜对离子的透过性进行了详细的讨论, 进而利用Donnan平衡理论推导的膜电位的表达式拟合, 获得了混合膜的固定电荷等参数.     

Significant improving H+/VO2+ permselectivity of Nafion membrane by modification with PDDA in aqueous isopropanol

The modification of Nafion® membranes with poly(diallyldimethylammonium chloride) (PDDA) in aqueous solutions of isopropanol has been investigated. A remarkable decrease in vanadyl ion permeability (by 3.5 orders of magnitude), accompanied by a decrease in proton conductivity sixfold at most, was found for Nafion membranes modified in 30–35 wt% isopropanol solutions providing a high swelling of the membranes. The Bradford reagent has been used for the detection of PDDA on the membrane surface.     

A Recurrent Neural Network model to predict blood–brain barrier permeability

The rapid development of computational methods and the increasing volume of chemical and biological data have contributed to an immense growth in chemical research. This field of study is known as “chemoinformatics,” which is a discipline that uses machine-learning techniques to extract, process, and extrapolate data from chemical structures. One of the significant lines of research in chemoinformatics is the study of blood–brain barrier (BBB) permeability, which aims to identify drug penetration into the central nervous system (CNS). In this research, we attempt to solve the problem of BBB permeability by predicting compounds penetration to the CNS. To accomplish this goal: (i) First, an overview is provided to the field of chemoinformatics, its definition, applications, and challenges, (ii) Second, a broad view is taken to investigate previous machine-learning and deep-learning computational models to solve BBB permeability. Based on the analysis of previous models, three main challenges that collectively affect the classifier performance are identified, which we define as “the triple constraints”; subsequently, we map each constraint to a proposed solution, (iii) Finally, we conclude this endeavor by proposing a deep learning based Recurrent Neural Network model, to predict BBB permeability (RNN-BBB model). Our model outperformed other studies from the literature by scoring an overall accuracy of 96.53%, and a specificity score of 98.08%. The obtained results confirm that addressing the triple constraints substantially improves the classification model capability specifically when predicting compounds with low penetration.     

Changes in Ion Selectivity Following the Asymmetrical Addition of Charge to the Selectivity Filter of Bacterial Sodium Channels

Voltage-gated sodium channels (NaVs) play fundamental roles in eukaryotes, but their exceptional size hinders their structural resolution. Bacterial NaVs are simplified homologues of their eukaryotic counterparts, but their use as models of eukaryotic Na⁺ channels is limited by their homotetrameric structure at odds with the asymmetric Selectivity Filter (SF) of eukaryotic NaVs. This work aims at mimicking the SF of eukaryotic NaVs by engineering radial asymmetry into the SF of bacterial channels. This goal was pursued with two approaches: the co-expression of different monomers of the NaChBac bacterial channel to induce the random assembly of heterotetramers, and the concatenation of four bacterial monomers to form a concatemer that can be targeted by site-specific mutagenesis. Patch-clamp measurements and Molecular Dynamics simulations showed that an additional gating charge in the SF leads to a significant increase in Na⁺ and a modest increase in the Ca²⁺ conductance in the NavMs concatemer in agreement with the behavior of the population of random heterotetramers with the highest proportion of channels with charge −5e. We thus showed that charge, despite being important, is not the only determinant of conduction and selectivity, and we created new tools extending the use of bacterial channels as models of eukaryotic counterparts.     

Test methods for the characterization of gas and vapor permeability in polymers for food packaging application: A review

The assessment of the transport properties of different substances in polymeric materials is of crucial importance for the evaluation of packaging performances, aiming to protect packed food products and ensure a prolonged shelf-life. The most relevant substances for such application can be identified in O₂, CO₂ and C₂H₄ (together with N₂ as control) as permanent gases, and water vapor as condensable species. All these penetrants are able to alter significantly food properties, in term of sensory characteristics, textures, and quality in general. All relevant techniques for the experimental characterization of mass transport properties in polymeric films or packages are critically reviewed, focusing in detail on standard methods. Each technique is briefly presented in terms of apparatus requirements and general procedures, followed by a discussion on its main features.     

Multipurpose nonwoven viscose/polypropylene fabrics: Effect of fabric characteristics on sorption and dielectric properties

In this work, sorption and dielectric properties of viscose/polypropylene multipurpose nonwoven fabrics were examined. The analysis of sorption behavior showed that the changes of the water absorptive capacity, the height of capillary rise and water retention value are in a function of viscose fiber content, total porosity, the pore size and used web bonding process. It is observed that dielectric properties at frequencies from 30 Hz to 140 kHz, for samples exposed to different relative air humidity and wet samples, are dependent on viscose fiber content, web bonding process, frequency of electric field and bulk free water content. The effective dielectric permeability of wet samples rapidly decreases with an increase in frequency up to 3 kHz while spectra of the AC specific electrical conductivity showed a plateau above 13 kHz. It is also observed that the dielectric properties of wet samples increase by several orders of magnitude compared to dry samples. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 947–957