A new linearly constrained minimum variance beamformer for reconstructing EEG sparse sources

Brain source imaging based on EEG aims to reconstruct the neural activities producing the scalp potentials. This includes solving the forward and inverse problems. The aim of the inverse problem is to estimate the activity of the brain sources based on the measured data and leadfield matrix computed in the forward step. Spatial filtering, also known as beamforming, is an inverse method that reconstructs the time course of the source at a particular location by weighting and linearly combining the sensor data. In this paper, we considered a temporal assumption related to the time course of the source, namely sparsity, in the Linearly Constrained Minimum Variance (LCMV) beamformer. This assumption sounds reasonable since not all brain sources are active all the time such as epileptic spikes and also some experimental protocols such as electrical stimulations of a peripheral nerve can be sparse in time. Developing the sparse beamformer is done by incorporating L1-norm regularization of the beamformer output in the relevant cost function while obtaining the filter weights. We called this new beamformer SParse LCMV (SP-LCMV). We compared the performance of the SP-LCMV with that of LCMV for both superficial and deep sources with different amplitudes using synthetic EEG signals. Also, we compared them in localization and reconstruction of sources underlying electric median nerve stimulation. Results show that the proposed sparse beamformer can enhance reconstruction of sparse sources especially in the case of sources with high amplitude spikes.     

Fox Hunting in Wild Apples: Searching for Novel Genes in Malus Sieversii

Malus sieversii is considered the progenitor of modern apple (Malus pumila) cultivars and to represent a valuable source of genetic diversity. Despite the importance of M. sieversii as a source of disease resistance, stress tolerance, and novel fruit traits, little is known about gene function and diversity in M. sieversii. Notably, a publicly annotated genome sequence for this species is not available. In the current study, the FOX (Full-length cDNA OvereXpressing) gene hunting system was used to construct a library of transgenic lines of Arabidopsis in which each transgenic line overexpresses a full-length gene obtained from a cDNA library of the PI619283 accession of M. sieversii. The cDNA library was constructed from mRNA obtained from bark tissues collected in late fall–early winter, a time at which many abiotic stress-adaptative genes are expressed. Over 4000 apple FOX Arabidopsis lines have been established from the pool of transgenic seeds and cDNA inserts corresponding to various Gene Ontology (GO) categories have been identified. A total of 160 inserts appear to be novel, with no or limited homology to M. pumila, Arabidopsis, or poplar. Over 1300 lines have also been screened for freezing resistance. The constructed library of transgenic lines provides a valuable genetic resource for exploring gene function and diversity in Malus sieversii. Notably, no such library of t-DNA lines currently exists for any Malus species.     

Physical modification of polymeric support layer for thin film composite forward osmosis membranes by metal–organic framework-based porous matrix membrane strategy

Physical modification of support layers (SLs) for thin-film composite (TFC) forward osmosis (FO) membranes is the main goal of this study. Accordingly, the strategy of metal–organic framework (MOF)-based porous matrix membrane (PMM) was used for the fabrication of controllable SLs. Fourteen different TFC FO membranes were successfully fabricated by interfacial polymerization (IP) technique over the fourteen different SLs made of polyetherimide (PEI), polyethersulfone (PES), and twelve MOF-based PMM. The controllable MOF particles, fabricated SLs, and TFC membranes were characterized by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle (CA), inductively coupled plasma (ICP), and developed SHN1 method. The results showed that the PMM strategy can lead to an increase in the degree of crosslinking of polyamide (PA) as a result of physical modification of the original SLs. Also, the PMM strategy reduced the structural parameters and hence the internal concentration polarization (ICP) was controlled. However, according to the characteristic curve, physical modification of the structure of PES and PEI by MOF-based PMM strategy caused a small and dramatic effect (respectively) on the performance of the TFC FO membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48672.     

川西彭州地区雷口坡组潮坪相薄储层辨识机理研究

川西彭州地区三叠系雷口坡组雷四上亚段潮坪相薄储层识别难度极大。围绕如何从复合地震强反射中区分并识别上、下两套储层面临的地球物理难题,采用先“分”后“合”的研究思路,基于实际地层结构及不同储层叠加样式建立正演模型,利用全波场波动方程正演模拟技术,剖析了不同主频条件下薄储层的地震响应特征,通过波形差异化分析,从复合地震响应中“剥离”出了两套储层所引起的地震响应特征及变化规律,明确了两套储层在不同频带下的地震识别标志和识别方法,为该区强反射界面干扰下两套薄互层储层辨识机理分析及精准预测奠定了基础。基于不同频带下薄储层辨识机理的分析结果,定性预测了薄储层平面展布,提出了深层潮坪相薄储层识别和预测难题的解决方案,为该区地震资料品质评价、面向薄储层的地震采集技术设计、地震资料处理及薄储层预测提供了依据和指导。     

钢结构施工变形预调值及分析方法

一般情况下钢结构的设计位形只是施工的目标位形,不能作为确定构件加工和安装位形的直接依据。为保证施工的顺利进行以及竣工时结构的位形满足设计要求,施工过程中需对结构设置变形预调值。介绍了钢结构施工变形预调值的概念,构造了钢结构施工变形预调值计算的一般迭代法、正装迭代法、倒拆迭代法和分阶段综合迭代法。其中,一般迭代法可用来计算采用满堂脚手架法施工的钢结构变形预调值。正装迭代法可用来计算各种施工方法下钢结构的变形预调值,但当结构复杂杆件比较多时,分析过程中常出现算法不收敛的问题。倒拆迭代法收敛性高,但计算工作量较大。分阶段综合迭代法可以用来计算闭环复杂结构的变形预调值,克服迭代不收敛问题,其计算工作量较小。     

上限单元技术(UBET)的基本理论及发展预测

阐述了一种在计算机、计算数学和上限法基础上发展起来的用于模拟金属塑性变形过程的上限单元技术的基本理论及应用     

缝洞型非均质体地震散射波特征正演研究

论文从地震散射波的基本原理出发,分析了散射波与模型的关系;根据缝洞的特征建立了相应的正演模型,编写了适应于这些散射模型的程序。利用这些程序计算了所设计的散射模型的地震记录。从计算结果中,对这些散射体产生的散射波特征有了进一步的认识。此外论文还对这些散射波能量作了比较,并分析了影响地震散射波能量的因素。     

基于BIM技术及三维激光扫描技术的古建筑修复保护研究

将三维激光扫描技术与BIM技术进行衔接,应用于古建筑的保护与修复,能发挥两种技术的优势。先通过三维激光扫描技术准确获取古建筑的几何信息,生成点云模型,再基于点云模型,建立BIM模型,从而实现文物古建筑修复的正向设计,为修复施工、古建筑维护、信息存档提供技术支持。     

铂扩散快恢复二极管特性的研究

描述了用直拉单晶(CZ)硅片采取铂液态源扩散的方法控制少子寿命,以达到减小快恢复二极管的反向恢复时间的目的.通过一系列的实验对铂扩散二极管的特性进行研究,分析了铂扩散二极管的反向恢复时间TRR、正向压降VF以及漏电流IR等参数之间的关系,并分析了反向恢复时间TRR的温度特性.得到TRR与VF之间的理想折衷:TRR为80～500 ns,VF控制在0.9～1.3 V.不但使TRR与VF的折衷有了较大的改善,而且在材料上采用了成本较低的直拉单晶硅片代替成本较高的外延片.分析了铂扩散温度和时间对反向恢复时间TRR和正向压降VF的影响,理论上解释了各主要参数之间相互影响的原因.