干湿循环下木质素改良粉土抗剪强度特性

为克服粉土强度低、干湿循环性能差的特点,同时解决固体废弃物木质素的资源化利用的问题,将木质素掺入粉土中,形成木质素改良粉土。为研究木质素改良粉土抗剪强度特性及干湿循环性能,对经历干湿循环后的木质素改良粉土进行直接剪切试验和X射线衍射试验,研究了木质素掺量0、2%、5%、8%、12%、15%和干湿循环0、1、2、3、4次对改良土抗剪强度特性的影响。结果表明:掺入木质素可以显著提升粉土的抗剪强度及干湿循环性能;一定干湿循环次数下,改良土的抗剪强度及黏聚力随着木质素掺量的增加先增大后降低,内摩擦角随着木质素掺量的增加先快速增大后基本不变;当木质素掺量为8%时,改良土的抗剪强度、黏聚力和内摩擦角最高。改良土的抗剪强度、黏聚力和内摩擦角均随着干湿循环次数的增加而降低,当木质素掺量为0时,纯土试样经过1次干湿循环即崩解,强度损失率为100%;当木质素掺量为8%时,改良土的强度损失率最低,黏聚力及内摩擦角的降低幅度均较低。X射线衍射试验表明,木质素掺量为8%时,石英、方解石、白云石含量最高,黏土矿物含量较高,钠长石含量最低,这是造成改良土强度及干湿循环性能提升的直接原因。结果显示,当木质素掺量为8%时,改良土在提高抗剪强度及干湿循环性能方面具有明显优势。研究结果可为实际施工设计提供理论支撑。

基于小样本图像分类的芯片引脚缺陷检测方法

为了检测SOP芯片的引脚缺陷,提出了基于小样本图像分类的SOP芯片引脚缺检测的方法。该方法包含了芯片定位识别、芯片倾斜矫正以及芯片引脚参数测量。根据芯片塑封体与视觉系统采集的样品背景的特征进行芯片定位识别算法研究。通过提取芯片塑封体的边缘点进行直线拟合并矫正倾斜的芯片算法研究。基于Lnent-5模型构建图像分类网络,以10×10的尺寸对预处理后的图像进行切割并分类,通过分类结果确定每个引脚的位置以及边界,并根据引脚边界的分类结果计算芯片引脚的关键尺寸,判断是否存在缺陷。实验结果表明总体检测率达到99%,此方法能够满足在小样本的情况下稳定、准确地检测出SOP芯片的引脚缺陷。

3D Printed Integrated Gradient-Conductive MXene/CNT/Polyimide Aerogel Frames for Electromagnetic Interference Shielding with Ultra-Low Reflection

Construction of advanced electromagnetic interference(EMI)shielding materials with miniaturized,programmable structure and low reflection are promising but challenging.Herein,an integrated transition-metal carbides/carbon nanotube/polyimide(gradient-conductive MXene/CNT/PI,GCMCP)aerogel frame with hierarchical porous structure and gradient-conductivity has been constructed to achieve EMI shielding with ultra-low reflection.The gradient-conductive structures are obtained by continuous 3D printing of MXene/CNT/poly(amic acid)inks with different CNT contents,where the slightly conductive top layer serves as EM absorption layer and the highly conductive bottom layer as reflection layer.In addition,the hierarchical porous structure could extend the EM dissipation path and dissipate EM by multiple reflections.Consequently,the GCMCP aerogel frames exhibit an excellent average EMI shielding efficiency(68.2 dB)and low reflection(R=0.23).Furthermore,the GCMCP aerogel frames with miniaturized and programmable structures can be used as EMI shielding gaskets and effectively block wireless power transmission,which shows a prosperous application prospect in defense industry and aerospace.

发芽青稞的营养品质及降血压效果

作者以发芽前后青稞中β-葡聚糖、γ-氨基丁酸、游离氨基酸、总多酚等营养成分的质量分数以及β-葡聚糖酶、蛋白酶等酶活性为指标,并结合高血压大鼠收缩压、心率等指标的变化情况,研究萌发对青稞营养品质和其降血压效果的影响。结果发现,青稞β-葡聚糖、淀粉和蛋白质质量分数随萌发时间延长而降低,γ-氨基丁酸质量分数在萌发48 h达到最高,总多酚、总黄酮质量分数以及β-葡聚糖酶、淀粉酶和蛋白酶的活力随萌发时间延长而增加。总游离氨基酸质量分数尤其是必需氨基酸质量分数经萌发处理后显著升高(P<0.05),表明发芽能提高青稞营养价值。此外,与青稞相比,发芽青稞更利于降低高血压大鼠的收缩压、心率、血管紧张素Ⅱ和血管生成素(P<0.05),表明发芽青稞有更好的缓解高血压作用。

基于混合采样的图对比学习推荐算法

在推荐系统领域中,图卷积网络具有对于图结构数据更强的信息抽取能力。然而,现有的图卷积网络推荐算法主要关注改进模型结构,忽视了提高原始样本采样质量与挖掘用户—项目间隐式关系的重要性。针对上述问题,提出一种基于混合采样的图对比学习推荐算法。首先使用混合采样方法,提取出正样本中部分信息并将其注入负样本,从而生成全新的富含信息的难负样本;其次,通过轻量图卷积网络对难负样本进行特征提取,得到用户和项目的节点表征,采用邻域对比学习方法挖掘样本隐式关系;最后,利用多任务策略对推荐监督任务和对比学习任务进行联合优化。在真实数据集Yelp2018和Amazon-book上进行实验,采用recall和NDCG指标进行评估,实验结果表明,提出的模型相较其他基准模型取得了更好的效果。

硫胺素及溶氧对解脂亚洛酵母联产酮酸的影响

α-酮戊二酸和丙酮酸是重要的酮酸,广泛应用于食品、医药等领域。以本研究室在前期的工作中诱变选育的Yarrowia lipolytica WSH-Z06 C3为出发菌株,高效联产α-酮戊二酸和丙酮酸。在摇瓶水平上初步确定了最佳氮源浓度以及接种密度。在此基础上,重点考察了在15 L发酵罐上硫胺素浓度以及溶氧控制参数对酮酸联产的影响。结果显示,硫胺素最佳浓度为0.2μg/L,α-酮戊二酸和丙酮酸分别高达24.5、53.7 g/L。与未优化的对照相比,酮酸总产量和丙酮酸总转化率均提高了57.9%。溶氧水平控制在50%,发酵96 h酮酸总产量高达53.2 g/L。通过两阶段溶氧调控,酮酸总产量高达64.7 g/L,比未调控前提高了21.2%。通过硫胺素与溶氧水平的优化,显著提高了酮酸的产量,进一步为酮酸的工业化生产提供参考。

一种简单有效的TDOA-FDOA-AOA目标定位闭式解

针对TDOA-FDOA-AOA联合定位中目标状态求解这一难题,提出了一种简单有效的闭式求解算法.首先根据几何关系,通过测量值变换,将与目标位置、速度高度非线性的时差、频差、角度测量方程转换为关于目标状态的线性函数,再利用加权最小二乘估计求得目标状态估计.性能分析及仿真结果证明了所提算法具有较好的定位性能.

用于SAR ADC的低开销电容开关时序设计

逐次逼近型模数转换器(SAR ADC)中,数模转换器单元(DAC)是能耗和面积的主要来源之一。为了降低DAC的能耗和面积,提出了一种低开销电容开关时序,以此设计了DAC的结构,并进行逻辑实现。相比于传统型开关时序,该电容开关时序使得DAC的能耗降低了98.45%,面积减小了87.5%。基于该电容开关时序实现了一种12位SAR ADC。仿真结果表明,在1.2 V电源电压、100 kS/s采样速率的条件下,该ADC功耗为12.5μW,有效位数为11.2位,无杂散动态范围为75.6 dB。

Exponential passive filtering for a class of nonlinear jump systems

The exponential passive filtering problem for a class of nonlinear Markov jump systems with uncertainties and time-delays is studied. The uncertain parameters are assumed unknown but norm bounded, and the nonlinearities satisfy the quadratic condition. Based on the passive filtering theory, the sufficient condition for the existence of the mode-dependent passive filter is given by analyzing the reconstructed observer system. By using the appropriate Lyapnnov-Krasovskii function and applying linear matrix inequalities, the design scheme of the passive filter is derived and described as an optimization one. The presented exponential passive filter makes the error dynamic systems exponentially stochastically stable for all the admissible uncertainties, time-delays and nonlinearities, has the better abilities of state tracking and satisfies the given passive norm index. Simulation results demonstrate the validity of the proposed approach.

Robust reliable H_∞ control for discrete-time Markov jump linear systems with actuator failures

The robust reliable H∞ control problem for discrete-time Markovian jump systems with actuator failures is studied. A more practical model of actuator failures than outage is considered. Based on the state feedback method, the resulting closed-loop systems are reliable in that they remain robust stochastically stable and satisfy a certain level of H∞ disturbance attenuation not only when all actuators are operational, but also in case of some actuator failures, The solvability condition of controllers can be equivalent to a feasibility problem of coupled linear matrix inequalities （LMIs）. A numerical example is also given to illustrate the design procedures and their effectiveness.

ESD应力下改进型SCR器件设计与漏电特性优化

为探讨片上集成电路静电放电防护的易闩锁与漏电软失效问题,设计了一种内嵌MOS结构的N跨桥可控硅器件.传输线脉冲测试结果表明:与传统N跨桥改进型可控硅相比,该器件的电压回滞幅度减小了约28.6%.然而,当作用于该器件的瞬态电流从2.0A增大到3.2A时,漏电流从2.8×10^(-7) A逐渐退化至1.7×10^(-5) A,器件较易发生软失效.借助TCAD技术,仿真结果表明:在10-4 A的静电脉冲应力作用下,该器件内部晶格温度高达1 160.5K.通过优化内嵌MOS结构的N跨桥可控硅器件的版图及其金属布线,削弱器件内部的功率密度聚集效应,可使器件在相同电应力下漏电流稳定在10^(-9) A量级.因此,该版图优化方法可有效地抑制器件的局部过热,提高片上集成电路的静电放电防护方案的热稳定性.

视觉显著区域和主动轮廓结合的图像分割算法

传统区域主动轮廓模型在分割弱边缘图像时,演化曲线受背景干扰,易陷入局部极值导致演化速度缓慢;且由于局部项仅考虑空间信息,无法更好保留目标边界,影响分割精度。针对上述问题,首先利用改进的显著性检测方法,对待分割图像进行预处理操作,获取目标候选区域,自动设置初始化轮廓曲线,并将获取的目标先验信息与待分割图像中具有最大对比度的位图相结合,设计自适应符号函数,对优化LoG能量项进行加权,以线性方式融合到RSF模型中,增强模型自适应能力;其次设计新的局部灰度测度,与局部核函数相结合,改进局部能量项,提高模型在弱边缘处的敏感程度,准确定位目标边界。实验结果表明,该模型能够自动设置初始化轮廓,并有效保留目标边缘细节,视觉及定量实验结果证明了该模型优于目前一些主流的主动轮廓模型。

Enantioselective reduction of acetophenone analogues using carrot and celeriac enzymes system

The enantioselective reduction of acetophenone analogues catalyzed by carrot and celeriac was performed in moderate conversions and excellent enantiomeric excesses.The steric factors and electronic effects of the substituents at the aromatic ring were found to significantly affect the efficiency of the enantioselective reduction of acetophenone analogues,while they had a little effect on the enantioselectivity of acetophenone analogues reduction.It was also found that the conversions of acetophenone analogu...

JTE终端结构4H-SiC JBS二极管的击穿特性研究

研究了JTE终端结构4H-SiC JBS二极管的击穿特性。首先,理论模拟了JTE终端横向长度、离子注入剂量和界面电荷对击穿电压的影响。对工艺条件进行优化,制作了JTE终端结构4H-SiC JBS二极管。测试结果表明,器件的正向电压为1.52 V,特征导通电阻为2.12 mΩ·cm^(2),击穿电压为1 650 V。接着,研究器件的变温电流-电压特性发现,正向电流主要为热发射机制,而反向电流与电压、温度有很强的依赖关系。最后进行了高温反偏应力老化测试,结果表明,击穿电压呈下降趋势。

Neural network-based H∞ filtering for nonlinear systems with time-delays

A novel H∞ design methodology for a neural network-based nonlinear filtering scheme is addressed. Firstly, neural networks are employed to approximate the nonlinearities. Next, the nonlinear dynamic system is represented by the mode-dependent linear difference inclusion （LDI）. Finally, based on the LDI model, a neural network-based nonlinear filter （NNBNF） is developed to minimize the upper bound of H∞ gain index of the estimation error under some linear matrix inequality （LMI） constraints. Compared with the existing nonlinear filters, NNBNF is time-invariant and numerically tractable. The validity and applicability of the proposed approach are successfully demonstrated in an illustrative example.

^(18)F-FDG PET/CT诊断cN0头颈部肿瘤患者颈淋巴结转移的Meta分析

目的:探讨^(18)F-脱氧葡萄糖PET/CT(^(18)F-FDG PET/CT)对cN0头颈部肿瘤患者颈淋巴结转移的诊断价值。方法:对电子数据库(PubMed、EMBASE、Cochrane Library、万方、CNKI数据库)进行系统检索。诊断性试验质量评价体系用来对纳入的研究进行质量评价。应用Meta-Disc 1.4软件进行Meta分析。结果:Meta分析共纳入8项研究。对以患者数为单位的数据,18 F-FDG PET/CT的合并敏感性(SEN)、特异性(SPE)、诊断比值比(DOR)、阳性似然比(+LR)、阴性似然比(-LR)分别为0.61(95%CI 0.52~0.69)、0.74(95%CI 0.68~0.78)、9.62(95%CI 2.49~37.22)、3.22(95%CI 1.55~6.71)和0.42(95%CI 0.24~0.37)。曲线下面积为0.804 1。采用Cochrane-Q检验和I^2检验对DOR结果进行异质性分析,得到Q=21.26(P<0.05),I^2=81.2%。结论:Meta分析表明,^(18)F-FDG PET/CT没有提供比CT/MRI更优的诊断准确率来检测cN0头颈部肿瘤颈淋巴结转移。考虑到所包含研究存在的异质性较高,PET/CT的潜在价值尚需在未来的研究中得到验证。

我国不同地区重点监控合理用药药品与管理政策分析

目的分析我国不同地区(包括省、市、自治区、直辖市)重点监控合理用药药品与管理政策。方法以重点监控、合理用药等为关键词,检索各地区卫生健康部门网站和政府官网,下载整理和分析各地区重点监控合理用药药品品种及监管措施。结果共检索到28个地区重点监控合理用药药品目录及政策文件,有77种药物被纳入省级监控目录,按药物解剖学-治疗学-化学分类共涉及11个药物类别,除国家重点监控品种外,各地区共增补57种。增补品种中抗肿瘤药及免疫调节剂、内科用药的品种数和频次最高。除国家目录品种外,出现频次最高的是脾多肽、胎盘多肽和鹿瓜多肽。各地区监控措施强调要加强药品使用监测,规范临床用药,纳入考核管理,以及通过加强药事管理和发挥临床药师作用等促进合理用药。结论省级重点监控合理用药药品品种较多,覆盖面广,建议相关部门不断完善管理制度和措施。

Carbon Fiber Supported Binary Metal Sulfide Catalysts with Multi-Dimensional Structures for Electrocatalytic Nitrogen Reduction Reactions Over a Wide pH Range

Green and environmentally friendly electrocatalytic nitrogen(N_(2))fixation to synthesize ammonia(NH3)is recognized as an effective method to replace the traditional Haber-Bosch process.However,the difficulties in N_(2) adsorption and fracture of hard N≡N bond still remain major challenges in electrocatalytic N_(2) reduction reactions(NRR).From the perspectives of enhancing N_(2) adsorption and providing more catalytic sites,two-dimensional(2D)FeS_(2) nanosheets and three-dimensional(3D)metal organic framework-derived ZnS embedded within N-doped carbon polyhedras are grown on the carbon cloth(CC)template in this work.Thus,a composite NRR catalyst with multi-dimensional structures,which is signed as FeS_(2)/ZnS-NC@CC,is obtained for using over a wide pH range.The uniform distribution of hollow ZnS-NC frameworks and FeS_(2) nanosheets on the surface of CC largely increase the N_(2) enrichment efficiency and offer more active sites,while the CC skeleton acts as an independent conductive substrate and S-doping helps promote the fracture of N≡N bond during the NRR reaction.As a result,the FeS_(2)/ZnS-NC@CC electrode achieves a high Faraday efficiency of 46.84%and NH3 yield of 58.52μg h^(−1) mg^(−1) at-0.5 V vs.Ag/AgCl in 0.1 M KOH.Furthermore,the FeS_(2)/ZnS-NC@CC electrode displays excellent NRR catalytic activity in acidic and neutral electrolytes as well,which outperforms most previously reported electrocatalysts including noble metals.Therefore,this work provides a new way for the design of multi-dimensional electrocatalysts with excellent electrocatalytic efficiency and stability for NRR applications.

Cost-effectiveness analysis of malaria rapid diagnostic tests:a systematic review

Background:Rapid diagnostic tests(RDT)can effectively manage malaria cases and reduce excess costs brought by misdiagnosis.However,few studies have evaluated the economic value of this technology.The purpose of this study is to systematically review the economic value of RDT in malaria diagnosis.Main text:A detailed search strategy was developed to identify published economic evaluations that provide evidence regarding the cost-effectiveness of malaria RDT.Electronic databases including MEDLINE,EMBASE,Biosis Previews,Web of Science and Cochrane Library were searched from Jan 2007 to July 2018.Two researchers screened studies independently based on pre-specified inclusion and exclusion criteria.The Consolidated Health Economic Evaluation Reporting Standards(CHEERS)checklist was applied to evaluate the quality of the studies.Then cost and effectiveness data were extracted and summarized in a narrative way.Fifteen economic evaluations of RDT compared to other diagnostic methods were identified.The overall quality of studies varied greatly but most of them were scored to be of high or moderate quality.Ten of the fifteen studies reported that RDT was likely to be a cost-effective approach compared to its comparisons,but the results could be influenced by the alternatives,study perspectives,malaria prevalence,and the types of RDT.Conclusions:Based on available evidence,RDT had the potential to be more cost-effective than either microscopy or presumptive diagnosis.Further research is also required to draw a more robust conclusion.

Interaction and combined toxicity of microplastics and per-and polyfluoroalkyl substances in aquatic environment

Microplastics(MPs)are recognized as vectors for the transport of organic contaminants in aquatic environments in addition to their own adverse effects on aquatic organisms.Per-and polyfluoroalkyl substances(PFASs)are widely present in aquatic environments due to their widespread applications,and thus coexist with MPs.Therefore,we focus on the interaction of MPs and PFASs and related combined toxicity in aquatic environments in this work The adsorption of PFASs on MPs is critically reviewed,and new mechanisms such as halogen bonding,π-πinteraction,cation-πinteractions,and micelle formation are proposed.Moreover,the effect of MPs on the transport and transformation of PFASs in aquatic environments is discussed.Based on four typical aquatic organisms(shellfish,Daphnia,algae,and fish),the toxicity of MPs and/or PFASs at the organismal or molecular levels is also evaluated and summarized.Finally,challenges and research perspectives are proposed,and the roles of the shapes and aging process of MPs on PFAS biogeochemical processes and toxicity,especially on PFAS substitutes,are recommended for further investigation.This review provides a better understanding of the interactions and toxic effects of coexisting MPs and PFASs in aquatic environments.