一维光子晶体能带结构的电光特性研究

采用有限元法对一维掺镧锆钛酸铅光子晶体的能带特性进行分析。当给一维掺镧锆钛酸铅光子晶体施以外加电场时,由于介质掺镧锆钛酸铅的电光效应引起折射率变化,使得一维掺镧锆钛酸铅光子晶体的能带结构发生变化。详细分析了外加电场变化对一维掺镧锆钛酸铅光子晶体的禁带结构特性的影响,禁带的中心波长及禁带宽度的变化量与电场呈四次函数关系。

MnO_(2) cathode materials with the improved stability via nitrogen doping for aqueous zinc-ion batteries

The research and exploration of manganese-based aqueous zinc-ion batteries have been controversial of cycle stability and mechanism investigation,thus improving the stability and exploring storage mechanism are still the most main issue.Defect engineering has become an effective method to improve cycle stability.Herein,a nitrogen-doped ε-MnO_(2)(MnO_(2)@N)has been prepared using electrochemical deposition and heat treatment under nitrogen atmosphere.As the cathode for zinc-ion batteries,the capacity retention rate of MnO_(2)@N cathode is close to 100%after 500 cycles at 0.5 A g^(-1),while the capacity retention rate for the initial MnO_(2) cathode is 62%.At 5 A g^(-1),the capacity retention rate of MnO_(2)@N cathode is 83%after 1000 cycles,which is much higher than the 27%capacity retention rate for the original MnO_(2) cathode.And it can be found that the oxygen vacancies increase after nitrogen doping,which can improve the conductivity of the MnO_(2)@N cathode.Also,there is Mn-N bond in MnO_(2)@N,which can enhance the electrochemical stability of MnO_(2)@N cathode.In addition,the electrochemical mechanism of MnO_(2)@N cathode has been explored by the CV,GCD and GITT tests.It is found that nitrogen doping promotes the intercalation of H^(+) and the corresponding capacity contribution.Compared with the original MnO_(2) cathode,the diffusion coefficient of H^(+) and Zn^(2+) in MnO_(2)@N cathode increases.Also,the reactions during the charging and discharging process are explored through the ex-situ XRD test.And this work may provide some new ideas for improving the stability of manganese-based zinc-ion batteries.

Current climate overrides past climate change in explaining multi-site beta diversity of Lauraceae species in China

Background:We aimed to characterise the geographical distribution of Sørensen-based multi-site dissimilarity(β_(sor))and its underlying true turnover(β_(sim))and nestedness(βsne)components for Chinese Lauraceae and to analyse their relationships to current climate and past climate change.Methods:We used ensembles of small models(ESMs)to map the current distributions of 353 Lauraceae species in China and calculated β_(sor) and its β_(sim) and β_(sne) components.We tested the relationship between β_(sor),β_(sne) and β_(sim) with current climate and past climate change related predictors using a series of simultaneous autoregressive(SAR_(err))models.Results:Spatial distribution of β_(sor)of Lauraceae is positively correlated with latitude,showing an inverse rela-tionship to the latitudinalα-diversity(species richness)gradient.High β_(sor) occurs at the boundaries of the warm temperate and subtropical zones and at the Qinghai-Tibet Plateau due to high β_(sne).The optimized SAR_(err) model explainsβ_(sor) andβ_(sne) well,but notβ_(sim).Current mean annual temperature determinesβ_(sor) and β_(sne) of Lauraceae more than anomalies and velocities of temperature or precipitation since the Last Glacial Maximum.Conclusions:Current low temperatures and high climatic heterogeneity are the main factors explaining the high multi-siteβ-diversity of Lauraceae.In contrast to analyses of the β-diversity of entire species assemblages,studies of single plant families can provide complementary insights into the drivers of β-diversity of evolutionarily more narrowly defined entities.

An analytical poroelastic model for laboratorial mechanical testing of the articular cartilage (AC)

The articular cartilage(AC) can be seen as a biphasic poroelastic material.The cartilage deformation under compression mainly leads to an interstitial fluid flow in the porous solid phase.In this paper,an analytical poroelastic model for the AC under laboratorial mechanical testing is developed.The solutions of interstitial fluid pressure and velocity are obtained.The results show the following facts.(i) Both the pressure and fluid velocity amplitudes are proportional to the strain loading amplitude.(ii) Both the amplitudes of pore fluid pressure and velocity in the AC depend more on the loading amplitude than on the frequency.Thus,in order to obtain the considerable fluid stimulus for the AC cell responses,the most effective way is to increase the loading amplitude rather than the frequency.(iii) Both the interstitial fluid pressure and velocity are strongly affected by permeability variations.This model can be used in experimental tests of the parameters of AC or other poroelastic materials,and in research of mechanotransduction and injury mechanism involved interstitial fluid flow.

A fluid flow model in the lacunar-canalicular system under the pressure gradient and electrical field driven loads

The lacunar-canalicular system(LCS)is acknowledged to directly participate in bone tissue remodeling.The fluid flow in the LCS is synergic driven by the pressure gradient and electric field loads due to the electro-mechanical properties of bone.In this paper,an idealized annulus Maxwell fluid flow model in bone canaliculus is established,and the analytical solutions of the fluid velocity,the fluid shear stress,and the fluid flow rate are obtained.The results of the fluid flow under pressure gradient driven(PGD),electric field driven(EFD),and pressure-electricity synergic driven(P-ESD)patterns are compared and discussed.The effects of the diameter of canaliculi and osteocyte processes are evaluated.The results show that the P-ESD pattern can combine the regulatory advantages of single PGD and EFD patterns,and the osteocyte process surface can feel a relatively uniform shear stress distribution.As the bone canalicular inner radius increases,the produced shear stress under the PGD or P-ESD pattern increases slightly but changes little under the EFD pattern.The increase in the viscosity makes the flow slow down but does not affect the fluid shear stress(FSS)on the canalicular inner wall and osteocyte process surface.The increase in the high-valent ions does not affect the flow velocity and the flow rate,but the FSS on the canalicular inner wall and osteocyte process surface increases linearly.In this study,the results show that the shear stress sensed by the osteocyte process under the P-ESD pattern can be regulated by changing the pressure gradient and the intensity of electric field,as well as the parameters of the annulus fluid and the canaliculus size,which is helpful for the osteocyte mechanical responses.The established model provides a basis for the study of the mechanisms of electro-mechanical signals stimulating bone tissue(cells)growth.

骨细胞方向对负荷诱导的骨内液体流动和营养物质运输的影响

与年龄或某些骨骼疾病相关的骨细胞空间排列方向的变化引起了研究者们的广泛关注.本研究的目的是通过建立骨细胞相对于骨内流体流动轴偏转0°、30°、45°、60°和90°的骨单元多孔弹性力学模型,证明骨细胞方向对骨内流体流动的影响.我们假设骨陷窝-小管网络规则排列且均匀分布,且将骨单元定义为由微观尺度水平上的代表性立方周期单元(CPUC)组成.通过计算骨细胞周围骨小管的数量和3D分布来估算骨单元的微观结构参数(渗透率、孔隙率等),并建立骨单元孔隙弹性有限元模型,研究不同边界条件和载荷形式下负载诱导的骨内间质流体流动和骨内营养物质运输.结果表明,在接近正常生理活动的载荷条件下,骨细胞方向对骨单元最大流体压力(p)、最大流体速度(v)和最大流体剪切应力(τ)都有显著的影响.p值和τ值在骨单元壁内呈现不均匀分布,这说明骨细胞方向和骨小管三维分布是预测骨陷窝-小管系统渗透性各向异性程度的重要参数,但骨细胞方向对骨内营养物质运输影响很小.此外,载荷形式和骨陷窝-小管弯曲度对骨单元的液体流动行为的影响大于骨细胞方向对其的影响.这项研究的结果将有助于人们准确量化骨内液体流动行为,并增强对骨的力传导机制的理解.

一种新型设计的个性化椎间融合器及其生物力学分析

椎间融合器在临床上经常用于脊柱感染性和退行性疾病的治疗,然而,进一步的临床应用通常受到一些缺陷的困扰,如应力遮挡和融合器沉降.本研究旨在提出一种新的脊柱融合器个性化设计理念:从微观到宏观的多尺度联合设计方法,创建与腰椎骨终板弹性模量和手术形式皆匹配的脊柱融合器.具体而言,引入三周期极小曲面来模拟聚醚醚酮(PEEK)融合器的多孔结构,通过调整孔隙参数以实现定制的宏观力学性能和孔隙结构的渗透性能。接着,针对经皮内镜下腰椎后路椎间融合术(PE-PLIF)进行多目标(屈伸、弯曲和扭转)拓扑优化,得到二次设计的新型多孔拓扑融合器。最后,将临床常用的钛融合器、PEEK融合器和本文设计的新型融合器进行基于有限元方法的生物力学对比分析。结果表明,与其他两种融合器相比,新型多孔拓扑融合器有着较低的骨-融合器界面应力和较高的内部移植骨应力和应变能密度,证明其有着较低的融合器沉降率和应力屏蔽的风险.总之,新型多孔拓扑融合器由于其良好的生物力学性能成为椎间融合术的理想选择.本文所提出的融合器设计思路和理念也可用于指导其他不同椎间融合术.

四棱锥型钉头内固定系统用于治疗Pauwels Ⅲ型股骨颈骨折

目前治疗股骨颈骨折的临床选择包括传统的空心螺钉内固定、动力髋螺钉内固定、髋关节置换和最新的股骨颈系统(FNS).股骨颈系统因表现出优良的机械性能而受到关注和欢迎.在本研究中,采用三维有限元法对股骨颈系统进行了分析,并根据分析结果对四种不同螺钉头的新型内固定进行了优化设计.在对FNS的分析结果中,植入股骨头内的螺钉部分受力较小,移位较大,由于这里使用了两个螺钉,材料消耗增加.钢板和锁定螺钉的结构使内固定物和股骨上的内应力更加均匀.在四种类型的螺钉头内固定中,四棱锥型螺钉头内固定的机械性能更为均衡.在四棱锥型螺钉头内固定与股骨颈系统的比较中,四棱锥型螺钉头内固定的应力和位移数据都显示出其优越性.股骨颈系统的单一尺寸设计对股骨尺寸偏离平均值较大的人群没有起到最佳的治疗效果,可调节长度和角度的新型内固定可以得到更广泛的应用.

猪关节软骨三层力-电特性的实验研究

力-电特性是关节软骨中众所周知的特性之一.然而目前还不清楚软骨组织不同区域的力-电特性.因此,本文的目的是研究关节软骨各区域的力-电特性及其相关影响因素.施加载荷后,力-电特性产生的电压信号沿软骨厚度方向由浅表层向深层逐渐增加,并且这种机制只有在应力产生明显相对变化时才能表现出来.此外,关节软骨的力-电特性产生的电压信号会随着载荷峰值和加载速率的增加而明显增加.我们通过将实验结果与指数函数进行拟合,得出了软骨各区的力-电特性的电压变化规律.研究结果表明,软骨组织不同区域的力-电特性差异在很大程度上取决于胶原纤维的排列分布.另外,软骨的内部结构和外部加载条件对关节软骨的力-电特性也有重要影响.这可为组织工程学中人工植入压电材料治疗骨关节炎提供重要参考.

不同碳源对生防荧光假单胞菌2P24产抗生素2,4-二乙酰基间苯三酚的影响

【目的】包括碳源代谢等不同环境因子可调控生防菌株生防相关因子表达,进而影响其防病效果。荧光假单胞菌2P24可防治多种植物病原真菌、细菌引起的土传病害,抗生素2,4-二乙酰基间苯三酚(2,4-diacetylphoroglucinol,2,4-DAPG)是其主要生防因子之一。本文利用平板对峙法及遗传学方法研究不同碳源对菌株2P24产生2,4-DAPG的影响及相关的调控途径。【方法】利用平板对峙法检测了菌株2P24在添加葡萄糖、果糖和蔗糖等碳源的土豆浸液培养基中对棉花立枯丝核菌(Rhizoctonia solani)的拮抗能力及菌株2P24中影响2,4-DAPG产生的相关基因的表达。另外,利用Tn5转座子对含有2,4-DAPG合成基因phl A报告质粒p970Gm-phl Ap的野生型菌株2P24进行随机突变,在果糖土豆浸液培养基中筛选提高phl A基因表达的突变菌株。【结果】平板对峙实验表明,菌株2P24以葡萄糖为碳源时其抑菌活性最强,蔗糖次之,而以果糖等为碳源时菌株2P24无抑菌活性;转录融合实验进一步表明葡萄糖可促进phl A基因的表达,果糖则不影响phl A基因的表达。在果糖土豆浸液培养基中,转座子随机突变实验获得了5株可明显提高phl A基因表达的突变菌株。Tn5插入位点和序列分析显示其中一个突变体是Tn5破坏了che B基因。转录检测表明与野生菌株相比,che B突变体中phl A基因的表达和2,4-DAPG的前体物质间苯三酚(phloroglucinol,PG)产量都显著提高。游动性实验发现突变che B基因可显著降低该菌株的游动性。【结论】上述结果表明菌株2P24中不同碳源在转录水平上可影响phl A基因的表达,进而影响2,4-DAPG产生。遗传学结果也显示,che B基因参与调控2,4-DAPG生物合成过程。

Review and Development of Electric Motor Systems and Electric Powertrains for New Energy Vehicles

This paper presents a review on the recent research and technical progress of electric motor systems and electric powertrains for new energy vehicles.Through the analysis and comparison of direct current motor,induction motor,and synchronous motor,it is found that permanent magnet synchronous motor has better overall performance;by comparison with converters with Si-based IGBTs,it is found converters with SiC MOSFETs show significantly higher efficiency and increase driving mileage per charge.In addition,the pros and cons of different control strategies and algorithms are demonstrated.Next,by comparing series,parallel,and power split hybrid powertrains,the series-parallel compound hybrid powertrains are found to provide better fuel economy.Different electric powertrains,hybrid powertrains,and range-extended electric systems are also detailed,and their advantages and disadvantages are described.Finally,the technology roadmap over the next 15 years is proposed regarding traction motor,power electronic converter and electric powertrain as well as the key materials and components at each time frame.

硫空位修饰的CoNi2S4纳米片用于电化学性能增强的非对称超级电容器

如何安全、高效、简便地制备出具有优异电化学性能的超级电容器电极材料是当前人们十分关注的问题.这些特性通常与电极中的空位和杂质有关.为了研究空位对超级电容器阴极材料性能的影响,我们采用一步水热法制备了具有硫空位的CoNi2S4(r-CoNi2S4)纳米片结构电极材料.利用拉曼光谱、X射线光电子能谱(XPS)等手段对硫空位的形成进行了表征.作为超级电容器的电极,r-CoNi2S4纳米片在电流密度为1 A g-1时具有1918.9 F g-1的高容量、优异的倍率性能(在电流密度为20 A g-1时,相对于1 A g-1的保持率为87.9%)和超常的循环稳定性.与原始的CoNi2S4纳米片电极(1 A g-1时容量为1226 F g-1)相比,r-CoNi2S4电极的性能显著提高.基于r-CoNi2S4正极和活性炭负极的不对称超级电容器具有较高的能量密度.通过点亮三种不同颜色的发光二极管(LED)灯,成功证明了该器件在实际应用中的可行性和巨大潜力.

COVID-19 Super Spreading Event Amongst Elderly Individuals—Jilin Province,China,January 2021

Summary What is already known on this topic?Clusters of COVID-19 cases often happened in small settings(e.g.,families,offices,school,or workplaces)that facilitate person-to-person virus transmission,especially from a common exposure.What is added by this report?On January 10 and 11,2021,an individual gave three product promotional lectures in Tonghua City.

Multi-scale mechanotransduction of the poroelastic signals from osteon to osteocyte in bone tissue

In order to quantify the poroelastic mechanical signals conduction and evaluate the biomechanical effectiveness of functional units(osteocyte processes,canaliculi and lacuna)in lacunar-canalicular system(LCS),a multiscale poroelastic finite element model was established by using the Comsol Multiphysics software.The poroelastic mechanical signals(pore pressure,fluid velocity,von-Mises stress,strain)were analyzed inside the osteon-osteocyte system.The effects of osteocyte(OCY)’s shape(ellipse and circle),long axis directions(horizontal and vertical)and mechanical properties(Elastic modulus and permeability)on its poroelastic responses were examined.It is found that the OCY processes is the best mechanosensor compared with the OCY body,lacunae and canaliculi.The mechanotransduction ability of the elliptic shaped OCY is stronger than that of circular shaped.The pore pressure and flow velocity around OCYs increase as the elastic modulus and permeability of OCY increase.The established model can be used for studying the mechanism of bone mechanotransduction at the multiscale level.

Mn,N co-doped Co nanoparticles/porous carbon as air cathode for highly efficient rechargeable Zn-air batteries Hide Author's Information

Oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)are generally catalyzed by precious metals(Pt)and metal oxides(IrO_(2))which still have many shortages including expensive price,poor selectivity and undesirable stability.In this work,we report a Mn0-doped CoN_(x) on N-doped porous carbon(Mn-CoN_(x)/N-PC)composite from carbonizing metal-organic framework(MOF)derivative as the dual-functional catalyst to boost both the ORR and OER performances.Owing to the strong coordination effect between nitrogen and metal elements,the introduction of N can obviously improve the content of Co-N-C active sites for ORR.Meanwhile,the Mn-doping significantly regulates the electronic structure of the Co element and increases the content of Co^(0) which provide efficient OER active sites.Mn-CoN_(x)/N-PC catalyst delivers super dual-functional activity with a half-wave potential of 0.85 V,better than the 20%Pt/C catalyst(0.82 V).When used in Zn-air batteries for testing,Mn-CoN_(x)/N-PC electrocatalyst shows a high power density(145 mW·cm^(−2))and good cycle performance.

Review of DC-DC Converter Topologies Based on Impedance Network with Wide Input Voltage Range and High Gain for Fuel Cell Vehicles

The development of fuel cell vehicles(FCVs)has a major impact on improving air quality and reducing other fossil-fuel-related problems.DC-DC boost converters with wide input voltage ranges and high gains are essential to fuel cells and DC buses in the powertrains of FCVs,helping to improve the low voltage of fuel cells and“soft”output characteristics.To build DC-DC converters with the desired performance,their topologies have been widely investigated and optimized.Aiming to obtain the optimal design of wide input range and high-gain DC-DC boost converter topologies for FCVs,a review of the research status of DC-DC boost converters based on an impedance network is presented.Additionally,an evaluation system for DC-DC topologies for FCVs is constructed,providing a reference for designing wide input range and high-gain boost converters.The evaluation system uses eight indexes to comprehensively evaluate the performance of DC-DC boost converters for FCVs.On this basis,issues about DC-DC converters for FCVs are discussed,and future research directions are proposed.The main future research directions of DC-DC converter for FCVs include utilizing a DC-DC converter to realize online monitoring of the water content in FCs and designing buck-boost DC-DC converters suitable for high-power commercial FCVs.

Biomechanical evaluation of two fusion techniques based on finite element analysis:Percutaneous endoscopic and minimally invasive transforaminal lumbar interbody fusion

As a novel minimally invasive technique,percutaneous endoscopic transforaminal lumbar interbody fusion(PETLIF)has been widely used in the treatment of lumbar degenerative diseases.The purpose of this study was to analyze these two operation types’biomechanical performances of PE-TLIF and traditional minimally invasive transforaminal lumbar interbody fusion(MIS-TLIF)using the finite element(FE)method.The intact FE models of L4-L5 were established and validated based on the CT images.On this basis,the FE models of MIS-TLIF and PETLIF were established and analyzed.It is demonstrated that for lumbar interbody fusion with the oblique asymmetrically implanted cage under bilateral pedicle screws and rods fixation,such as MIS-TLIF and PE-TLIF,different degrees of articular process resection have no significant effect on the cage subsidence,and the surgical segment can achieve similar stability.In addition,the maximum stress of the L4 inferior endplate of MIS-TLIF and PE-TLIF is greater than that of the L5 superior endplate,which indicates that MIS-TLIF and PE-TLIF can cause cage subsidence in the L4 inferior endplate.

压力与电场协同作用下具有初级纤毛和胶原小丘的骨细胞的力学响应研究

骨细胞内的力学传感器是骨细胞感知周围力学环境变化的最重要的细胞器.为了评估骨陷窝骨小管系统(LCS)内胶原小丘、细胞突触和初级纤毛作为力学传感器的生物力学效应,我们利用COMSOL Multiphysics软件开发了一种压力-电场-结构相互作用的骨细胞模型,以描述在流体流动和电场刺激下LCS中胶原小丘,初级纤毛以及细胞突触作为骨细胞中力学传感器的力学感应效果.分析了LCS中的力学信号(孔隙压力、流体速度、应力、变形)并且研究了胶原小丘弹性模量的变化、细胞突触的数量和.位置、初级纤毛的长度和位置对骨细胞内力学传感器的力学敏感性以及骨细胞总体多孔弹性响应的影响.结果表明,初级纤毛和.胶原小丘的存在将会导致骨细胞部分位置产生明显的应力集中(比骨细胞体其他位置的应力大1-2个数量级).相比于细胞突触沿骨细胞短轴方向生长,沿长轴方向生长可以刺激骨细胞产生更大的应力.当初级纤毛位于骨细胞顶部时,初级纤毛基底的应力比初级纤毛位于骨细胞底部时大8 Pa.然而,胶原小丘和初级纤毛的存在并不影骨细胞整体的力学信号分布.所建立的模型可用于在多尺度水平上研究骨力学信号的传导机制.