结构/隐身一体化宽频聚甲基丙烯酰亚胺吸波泡沫的制备与性能

由于泡沫夹芯型结构复合材料具有轻质、宽频、高效、兼容等优点,是雷达吸波材料的理想选择。新型聚甲基丙烯酰亚胺泡沫因具有良好的力学性能、热变形温度和化学稳定性,受到高性能夹层结构复合材料领域的广泛关注。为了使聚甲基丙烯酰亚胺(PMI)泡沫具有吸波功能,在制备PMI泡沫的过程中需要加入吸波剂,但是吸波剂通常密度较大、易沉淀。若没有在制备方法中使用防沉淀技术或均匀分散技术,吸波剂在聚合过程中会出现严重沉降,吸波剂难以发挥最大功效,且泡沫原有的力学性能降低严重。因此,文中通过对聚甲基丙烯酰亚胺吸波泡沫制备工艺的改进,系统研究了增黏剂、交联剂及吸波剂含量对泡沫结构与性能的影响,通过二氧化硅增黏工艺,使吸波剂在泡沫中分散均匀,成功制备了力学性能及吸波性能优异的吸波泡沫,高温压缩强度到达0.7MPa以上,并且可在2~18GHz实现全频吸收,获得了具有结构/隐身一体化宽频聚甲基丙烯酰亚胺吸波泡沫的制备方法。

The Estimation of the Spot Volatility for Diffusion Process

In this paper, we propose a Gasser-Müller type spot volatility estimator (abbreviated as GM type estimator) for diffusion process, which is weighted by integrals, it is different from the kernel spot volatility estimator discussed by Kristensen (2010). Under more general conditions, the asymptotic unbiasedness and the asymptotic normality of the GM type estimator are derived. The simulation results show that the GM type spot volatility estimator has good estimation effect, and its mean square error tends to be less than that of the kernel spot volatility estimator discussed by Kristensen (2010), so it provides a selection method for estimating the spot volatility in high frequency data environment.

A seismic model for crustal structure in North China Craton

We present a digital crustal model in North China Craton(NCC). The construction of crustal model is based on digitization of original seismic sounding profiles, and new results of three-dimensional structure images of receiver functions. The crustal model includes seismic velocity and thickness of crustal layers. The depths to Moho indicate a thinning crust ~30 km in the east areas and a general westward deepening to more than 40 km in the west. The P wave velocity varies from 2.0 to 5.6 km/s in the sedimentary cover,from 5.8 to 6.4 km/s in the upper crust, and from 6.5 to 7.0 km/s in the lower crust. By analyzing regional trends in crustal structure and links to tectonic evolution illustrated by typical profiles, we conclude that:(1) The delimited area by the shallowing Moho in the eastern NCC represents the spatial range of the craton destruction. The present structure of the eastern NCC crust retains the tectonic information about craton destruction by extension and magmatism;(2) The tectonic activities of the craton destruction have modified the crustal structure of the convergence boundaries at the northern and southern margin of the NCC;(3) The Ordos terrene may represent a relatively stable tectonic feature in the NCC, but with the tectonic remnant of the continental collision during the assembly of the NCC in the north-east area and the response to the lateral expansion of the Tibetan Plateau during the Cenozoic in the south-west.

Plasma-assisted Ru/Zr-MOF catalyst for hydrogenation of CO2 to methane

As an important type of metal-organic framework(MOF),Zr-MOF shows excellent CO2 adsorption performance.In this work,a Zr-MOF was synthesized by a solvothennal method and adopted to support Ru through simple incipient-wetness impreg nation.Then the Ru/Zr-MOF was applied for CO2 hydrogenation(Vh2:VCO2=4:1)with the assistance of dielectric banner dischai'ge(DBD)plasma.The hydrogenation of Cd2 results showed that methane was produced selectively under the synergistic effect between plasma and the Ru/Zr-MOF catalyst,and the selectivity and yield of methane reached 94.6%and 39.1%,respectively.The XRD and SEM analyses indicate that the basic crystalline phase structure and morphology of the Zr-MOF and Ru/Zr-MOF remained the same after DBD plasma treatment,suggesting that the catalysts are stable in plasma.The guest molecules in the pores of the Zr-MOF are removed and the Ru"ions are reduced to metallic Ru()in the reduction atmosphere according to the BET and XPS results,which are responsible for the high performance of plasma with the Ru/Zr-MOF catalyst.In situ optical emission spectra of pure plasma,plasma with Zr-MOF,and plasma with Ru/Zr-MOF were measured,and the active species of C,H and CH for CO2 hydrogenation were detected.The plasma-assisted Ru/Zr-MOF exhibited high catalytic activity and stability in CO2 hydrogenation to methane,and it has great guiding significance for CO2 hydrogenation by using plasma and MOF materials.

柔性宽频铁硅铝/芳纶纳米纤维纳米复合薄膜吸波性能

片状铁硅铝(FeSiAl)粉末由于具有较高的磁损耗和饱和磁强度而具有宽频、强吸收的电磁波吸收特性。但是,FeSiAl片层厚度较大且呈刚性的本征特性致使其在搭接时,片与片之间的相互作用力极差,因此其薄膜的力学强度和柔韧性较差,极大地限制了其在现代柔性电子器件中的应用。文中将少量水加入到芳纶纳米纤维(ANF)溶液中,诱导ANF分子链之间形成分子间氢键。通过调节水的添加量使其形成柔性水合芳纶纳米纤维网络。并将该柔性的ANF网络通过简单溶液共混的方式引入到FeSiAl薄膜中提升其力学性能和柔韧性。结果表明,当ANF的质量分数为60%时,该纳米复合薄膜兼具良好的电磁波吸收性能和柔韧性,此时,万能拉伸机测得纳米复合薄膜的力学强度高达136.88 MPa、断裂伸长率为4.72%。采用电磁参数测试仪结合仿真计算得到在纳米复合薄膜的厚度仅为3 mm时,有效吸收带宽为2.84 GHz,最大吸收强度为-46.81 dB。此外,该纳米复合薄膜在反复折叠之后仍保持良好的柔韧性。这种纳米复合薄膜简单且绿色的制备方式使其在下一代柔性电子器件的吸波领域具有良好的应用场景。

Survey of 3D modeling using depth cameras

Three-dimensional(3D)modeling is an important topic in computer graphics and computer vision.In recent years,the introduction of consumer-grade depth cameras has resulted in profound advances in 3D modeling.Starting with the basic data structure,this survey reviews the latest developments of 3D modeling based on depth cameras,including research works on camera tracking,3D object and scene reconstruction,and high-quality texture reconstruction.We also discuss the future work and possible solutions for 3D modeling based on the depth camera.

Functional Analysis of Dunaliella salina Calmodulin Kinase Gene

[Objectives] This study was conducted to investigate the function of Dunaliella salina calmodulin kinase(CaM K) gene.[Methods] The sense and antisense gene fragments(223 bp) and spacer sequence(129 bp) of D.salina calmodulin kinase gene were cloned and inserted into the downstream part of the35 S promoter of the eukaryotic expression vector pM DCMGN-Cat.The siRNA expression system of CaM K gene was successfully constructed.The p CaM K-RNAi expression vector was transformed into D.salina cells by the LiA c/PEG-mediated method,giving transgenic D.salina.The expression of CaM K gene was then analyzed by real-time fluorescence quantitative PCR.[Results]The expression of CaM K gene in the transgenic D.salina was significantly reduced,by 70% compared with the control group,suggesting that the expression of CaM K gene was significantly inhibited.The examination of the growth status of D.salina showed that D.salina cell division and proliferation were also affected.It is proved that CaM K gene has a positive regulation effect on the division and proliferation of D.salina cells.[Conclusions] The study provides important information for further elucidating the function and action mechanism of D.salina calmodulin kinase gene.

The Effection Analysis of Geotechnical Investigation on Foundation Pit Supporting Construction

With the continuous development of the construction industry,the density of engineering construction and the difficulty of underground construction are also increasing.As an important construction protection measure,foundation pit support construction is widely used in underground construction.Starting from the characteristics of foundation pit support construction,this paper analyzes the influence of geotechnical investigation on foundation pit support construction,and analyzes the problems that need to be paid attention to in the survey process.

Nonstoichiometric In-S group yielding efficient carrier transfer pathway in In_(2)S_(3) photoanode for solar water oxidation

The construction of high-efficiency photoanodes is essential for developing outstanding photoelectrochemical(PEC)water splitting cells.Furthermore,insufficient carrier transport capabilities and sluggish surface water oxidation kinetics limit its application.Using a solvothermal annealing strategy,we prepared a nonstoichiometric In-S(NS)group on the surface of an In_(2)S_(3) photoanode in situ and unexpectedly formed a type II transfer path of carrier,thereby reducing the interfacial recombination and promoting the bulk separation.Firstprinciples calculations and comprehensive characterizations demonstrated NS group as an excellent oxygen evolution cocatalyst(OEC)that effectively facilitated carrier transport,lowered the surface overpotential,increased the surface active site,and accelerated the surface oxygen evolution reaction kinetics by precisely altering the rate-determining steps of*to*OH and*O to*OOH.These synergistic effects remarkably enhanced the PEC performance,with a high photocurrent density of 5.02 mA cm^(−2)at 1.23 V versus reversible hydrogen electrode and a negative shift in the onset potential by 310 mV.This work provides a new strategy for the in situ preparation of high-efficiency OECs and provides ideas for constructing excellent carrier transfer and transport channels.

Vulnerability Assessment of Distributed Load Shedding Algorithm for Active Distribution Power System Under Denial of Service Attack

In order to deal with frequency deviation andsupply-demand imbalance in active distribution power system, inthis paper a distributed under frequency load shedding (UFLS)strategy is proposed. Different from conventional centralizedUFLS schemes, no centralized master station gathering all thebuses’ information is required. Instead, each bus decides itsown load shedding amount by only relying on limited peer-topeer communication. However, such UFLS strategy may sufferfrom some unexpected cyber-attacks such as integrity attacksand denial of service (DoS) attack. The latter DoS attack aimsto degrade the system performance by jamming or breakingthe communication, which is of high probability to happen inpractical power system. To assess the vulnerability of proposeddistributed UFLS algorithm, the effect of DoS attack on distributed average consensus algorithm is theoretically derived,which indicates that the final consensus value can be estimatedby a given attack probability. It is also investigated that such DoSattack does harm to the load shedding amount and finally affectsthe system frequency performance in the active distributionpower system. Several case studies implemented on an IEEE33-bus active distribution power system are conducted to verifythe effectiveness of the theoretical findings and investigate thevulnerability of the considered power system.

光学卫星相机在轨调制传递函数检测方法

调制传递函数(Modulation Transfer Function,MTF)是光学卫星相机成像质量评价的重要参数之一,在轨MTF检测关系到遥感数据的应用和未来遥感相机的发展。针对目前对地观测中广泛应用的光电成像系统,以反射点源阵列、辐射状靶标和大面积刃边靶标等便于数学描述的特殊点线面目标作为参照,依据MTF的物理定义,通过亚像元位置检测与参数化模型拟合等,对卫星相机进行了在轨MTF检测。实验结果表明:点源法是最严密的检测方法,可以全面表征遥感相机的成像能力;方波法在大面积靶标配合下,能直接获取成像系统在奈奎斯特频率处的MTF值;刃边法是光学相机常用的检测方法,但是仅能获取沿轨与垂轨方向的MTF。三种方法所得的在轨MTF的检测结果具有较好的一致性,最大相对误差优于6.00%。这些方法各有特点,其适用性存在一定差异。

AGRI中太阳漫反射板反射率衰减监测仪的角度因子在轨校验研究

太阳漫反射板反射率衰减监测仪(后简称比辐射计,SDRDM)被用来监测漫反射板反射率的变化。其太阳观测端口的透过率和太阳漫射板的相对双向反射分布函数(BRDF)是随角度变化的变量,因此比辐射计观测信号会受到入射光线角度的影响,该影响因子被叫作比辐射计角度因子(简称角度因子)。提出一种使用星上数据计算角度因子的方法,该方法被使用的前提是太阳漫射板在轨前期不发生衰退。采用相同太阳角度比值计算,在不使用比辐射计角度因子的前提下验证了太阳漫反射板在轨前期的稳定性。随后计算SDRDM的角度因子,并与实验室测量结果进行比对。结果显示星上计算值与实验室测量值偏差小于0.5%,发射前测量的角度因子可以用于计算太阳漫反射板的退化因子。

Harmonic frequency mixing using high T_c superconductor Josephson junction mounted on pulse tube cryocooler

A frequency mixing system including microwave coupling and intermediate frequency (IF) measurement arrangements is designed. In lieu of liquid nitrogen, a pulse tube cryocooler is used to cool the whole system. With YBa2Cu3O7/Yttrium stabilized zirconia (YBCO/YSZ) bicry-stal Josephson junction as the mixing element, 36th harmonic frequency mixing at the 8 mm waveband is obtained.

The effects of water depth on the growth and reproduction of Potamogeton crispus in an in situ experiment

Aims Water level is one of the most important determinants of the distri-bution and composition of submersed aquatic vegetation in shal-low lakes.Without changes in nutrient loading,large-scale declines in submerged macrophytes in shallow lakes are largely attributed to strong external or internal forces,including changes in water level.As a winter-active submerged macrophyte,Potamogeton crispus has important functions in aquatic ecosystem.The objec-tives of our study were to reveal the effects of water depths on the germination,growth,reproduction and morphological changes of P.crispus under natural environmental conditions;identify the optimum water depth range for colonization of P.crispus;and pre-dict the succession course for P.crispus in Lake Taihu.Methods A long-term in situ experiment was performed to study the effects of water depth on the growth and morphology of P.crispus across the entire life cycle.Plants were grown in the improved cross type of rhizotrons for 30 weeks at three different water depths(60,120 and 200 cm)in Dongtaihu Bay of Lake Taihu.We measured the plant height,root length,the length and width of leaves and counted the numbers of leaves,ramets,turion spikes and roots of each plant on each observation day during the experiment.Important Findings Water depths ranging from 60 to 120 cm were favourable for above-ground vegetation growth,root tissue growth and the reproductive ability of P.crispus.At water depth of 200 cm or beyond,the distri-bution of P.crispus will be limited in the following year because of the lack of turion formation and the severe inhibition of ramet pro-duction.The relationship between above-ground biomass and growth time at three different water depths fits a logistic growth curve well(P<0.001).The rapid growth and distribution with high density of P.crispus at water depth near 60 cm during the reproductive stage is not favourable for growth of other submerged species.So a continuous water depth of~60-120 cm is the optimum growth depth range for the conservation and restoration of P.crispus in Lake Taihu.In addi-tion,the morphological parameters values acquired can replace or provide the ranges for the value of GmaxSB(the maximum growth rate of submerged plants,in the unit of d^(−1))obtained via calibration in the control equations of submerged plant growth in the Eco-Taihu model,which is a three-dimensional ecological model of Lake Taihu.

How do water depth and harvest intensity affect the growth and reproduction of Elodea nuttallii(Planch.)st.John?

Aims both high and low densities of macrophyte vegetation can impair its ecosystem service function.Harvesting is often applied to macrophyte vegetation to maintain an appropriate density.Vegetation harvesting has occasionally gone awry and caused catastrophes,such as vegetation disappearance and cyanobacterial dominance in waterways and lakes.because water depth influences macrophyte density at all life stages,the simultaneous influences of harvesting and water depth should be carefully examined.Thus,this study aims to quantify the effects of differently harvesting Elodea nuttal-lii on its growth and reproduction at different water depths in field experiments.Methods Four harvest intensities(harvesting E.nuttallii plant heights equal to 25%,50%,75%and 100%of the water depth)were applied to E.nuttallii growing at four different water depths(60,90,120 and 150 cm).Plant length and root length were measured.The node number,root number of each plant and number of floating plants were counted before harvesting.The harvested plant were dried to a constant weight for dry weight determination.Important Findings The rate of increase in the length and shoot number of E.nuttallii varied from−0.012 to 0.440 day^(−1) and from−0.020 to 0.639 day^(−1),respec-tively.Water depth>150 cm would limit E.nuttallii growth.Elodea nuttallii responded to increasing water depths and low-intensity har-vesting by increasing internodal length and decreasing shoot number.The larger internodal length of E.nuttallii observed in relatively deeper water was also induced by the physical strain generated by its buoy-ancy as its specific gravity was less than water’s.The physical mecha-nism of removing the plant canopy by harvesting decreased E.nuttallii buoyancy and prevented floating.Harvesting increased plant produc-tion in shallow waters<90 cm deep.moreover,it is also necessary to perform three medium-intensity harvests at a water depth of 120 cm and one low-intensity harvest or no harvesting at a water depth of 150 cm to achieve longer lifetimes and less biomass near the water surface when the plants reach or approach the water surface.

A survey on fast simulation of elastic objects

Elastic simulation plays an important role in computer graphics and has been widely applied to film and game industries. It also has a tight relationship to virtual reality and computational fabrication applications. The balance between accuracy and performance are the most important challenge in the design of an elastic simulation algorithm. This survey will begin with the basic knowledge of elastic simulation, and then investigate two major acceleration techniques for it. From the viewpoint of deformation energy, we introduce typical linearization and reduction ideas for accelerating. We also introduce some recent progress in projective and position-based dynamics, which mainly rely on special numerical methods. Besides, optimal control for elastic objects and typical collision resolving techniques are discussed. Finally, we discuss several possible future works on integrating elastic simulation into virtual reality and 3D printing applications.

Adenovirus-mediated tissue inhibitor of metalloproteinase-3 gene transfection inhibits rabbit intervertebral disc degeneration in vivo

The aim of this study was to investigate the inhibitory effects of recombinant adenovirus vector carrying tissue inhibitor of metalloproteinase-3(RAd-TIMP-3)against degeneration of rabbit intervertebral disc.Thirty Japanese white rabbits of 4 months old were randomly divided into 5 groups.Mild or moderate rabbit lumbar disc degeneration model was constructed with the controllable axial loading device by imposing 98 N pressure at the discs for 2 weeks.Various doses of virus were injected into the degenerated discs as follows:20μL of normal saline in group 1;20μL of RAd66(an empty adenovirus vector,1.0�1010 OPU/mL)in group 2;and 20,10,and 5μL of RAdTIMP-3(1.0�1010 OPU/mL)in groups 3,4,and 5,respectively.Two weeks after the injection,the discs were collected for investigations,including assessment of degeneration degrees according to the Thompson’s grading system,reverse-transcription polymerase chain reaction(RT-PCR)assay for TIMP-3 gene,Safranin O-Fast green staining,and immunohisto-chemical staining for TIMP-3 and type II collagen.According to Thompson’s criteria,the degeneration of groups 3,4,and 5,especially group 3,was alleviated as compared with groups 1 and 2.RT-PCR revealed that the expression of TIMP-3 in groups 3,4,and 5,especially in group 3,was significantly enhanced as compared with group 1(P<0.01).Both Safranin O-Fast green staining and type II collagen staining demonstrated better reserved integrity of disc matrix in groups 3,4,and 5 than in groups 1 and 2.TIMP-3 staining exhibited an obvious increase of positive-staining rate in groups 3,4,and 5 as compared with group 1.The positive-staining rate in group 3(79.42%�1.35%)was about 3 times that of group 1(25.47%�5.46%,P<0.01).RAdTIMP-3 can effectively protect the matrix of rabbit intervertebral disc against overloading-induced degeneration in a dose-dependent manner,resulting in the alleviation of disc degeneration.

Risk factors and a prediction model for sepsis: A multicenter retrospective study in China

Background:Sepsis is typically associated with poor outcomes.There are various risk factors and predictive mod-els for sepsis based on clinical indicators.However,these models are usually predictive of all critical patients.This study explored the risk factors for 28-day outcomes of patients with sepsis and developed a prognosis prediction model.Methods:This was a multicenter retrospective analysis of sepsis patients hospitalized in three intensive care units(ICUs)from September 1st 2015,to June 30th 2020.Demographic,clinical history,and laboratory test data were extracted from patient records.Investigators explored the risk factors affecting 28-day sepsis prognosis by univariate analysis.The effects of confounding factors were excluded by multivariate logistic regression analysis,and new joint predictive factors were calculated.A model predicting 28-day sepsis prognosis was constructed through data processing analysis.Results:A total of 545 patients with sepsis were included.The 28-day mortality rate was 32.3%.Risk factors including age,D-dimer,albumin,creatinine,and prothrombin time(PT)were predictive of death from sepsis.The goodness-of-fit value for this prediction model was 0.534,and the area under the receiver operating characteristic curve was 0.7207.Further analysis of the immune subgroups(n=140)revealed a significant decrease in CD3+,CD4+CD8-,and CD4+CD29+memory effector T lymphocytes and an increase in CD56+natural killer(NK)cells in the hypoalbuminemia group compared with the normal albumin group(65.5 vs.58.3,P=0.005;41.2 vs.32.4,P=0.005;21.8 vs.17.1,P=0.029;12.6 vs.17.6,P=0.004).Conclusions:Risk factors for 28-day sepsis mortality include age,D-dimer,creatinine,PT,and albumin.A decrease in albumin level may exacerbate immunosuppression in patients with sepsis.This study establishes a prediction model based on these indicators,which shows a good degree of calibration and differentiation.This model may provide good predictive value for clinical sepsis prognosis.

Heterogeneous oxidation of SO_2 by O_3-aged black carbon and its dithiothreitol oxidative potential

Ozone（O3） is an important atmospheric oxidant. Black carbon（BC） particles released into the atmosphere undergo an aging process via O3 oxidation. O3-aged BC particles may change their uptake ability toward trace reducing gases such as SO2 in the atmosphere,leading to different environmental and health effects. In this paper, the heterogeneous reaction process between O3-aged BC and SO2 was explored via in-situ diffuse reflectance infrared Fourier transform spectroscopy（DRIFTS）. Combined with ion chromatography（IC）,DRIFTS was used to qualitatively and quantitatively analyze the sulfate product. The results showed that O3-aged BC had stronger SO2 oxidation ability than fresh BC, and the reactive species/sites generated on the surface had an important role in the oxidation of SO2.Relative humidity or 254 nm UV（ultraviolet） light illumination enhanced the oxidation uptake of SO2 on O3-aged BC. The oxidation potentials of the BC particles were detected via dithiothreitol（DTT） assay. The DTT activity over BC was decreased in the process of SO2 reduction, with the consumption of oxidative active sites.

Dynamics of a qubit—TLS system under resonant microwave driving

We demonstrate the effect of different coupling strengths between a microscopic two-level system(TLS)and a microwave field on the dynamics of a qubit—TLS system when the bipartite system is subject to resonant microwave driving.Rabi beating with a different TLSmicrowave coupling strength is demonstrated in simulations.Entanglement,quantified by the concurrence between the qubit and TLS,both for pure states and mixed states,is simulated.When decoherence is considered,entanglement of the bipartite system oscillates with damping and exhibits entanglement sudden death and/or entanglement sudden death and revival.