Ultrafine Vacancy-Rich Nb_(2)O_(5)Semiconductors Confined in Carbon Nanosheets Boost Dielectric Polarization for High-Attenuation Microwave Absorption

The integration of nano-semiconductors into electromagnetic wave absorption materials is a highly desirable strategy for intensifying dielectric polarization loss;achieving high-attenuation microwave absorption and realizing in-depth comprehension of dielectric loss mechanisms remain challenges.Herein,ultrafine oxygen vacancy-rich Nb_(2)O_(5)semiconductors are confined in carbon nanosheets(ov-Nb_(2)O_(5)/CNS)to boost dielectric polarization and achieve high attenuation.The polarization relaxation,electromagnetic response,and impedance matching of the ov-Nb_(2)O_(5)/CNS are significantly facilitated by the Nb_(2)O_(5)semiconductors with rich oxygen vacancies,which consequently realizes an extremely high attenuation performance of-80.8 dB(>99.999999%wave absorption)at 2.76 mm.As a dielectric polarization center,abundant Nb_(2)O_(5)–carbon heterointerfaces can intensify interfacial polarization loss to strengthen dielectric polarization,and the presence of oxygen vacancies endows Nb_(2)O_(5)semiconductors with abundant charge separation sites to reinforce electric dipole polarization.Moreover,the three-dimensional reconstruction of the absorber using microcomputer tomography technology provides insight into the intensification of the unique lamellar morphology regarding multiple reflection and scattering dissipation characteristics.Additionally,ov-Nb_(2)O_(5)/CNS demonstrates excellent application potential by curing into a microwave-absorbing,machinable,and heat-dissipating plate.This work provides insight into the dielectric polarization loss mechanisms of nano-semiconductor/carbon composites and inspires the design of high-performance microwave absorption materials.

Noiseless linear amplification for the single-photon entanglement of arbitrary polarization–time-bin qudit

Single-photon entanglement(SPE) is an important source in quantum communication. In this paper, we put forward a single-photon-assisted noiseless linear amplification protocol to protect the SPE of an arbitrary polarization–time-bin qudit from the photon transmission loss caused by the practical channel noise. After the amplification, the fidelity of the SPE can be effectively increased. Meanwhile, the encoded polarization–time-bin features of the qudit can be well preserved. The protocol can be realized under the current experimental conditions. Moreover, the amplification protocol can be extended to resist complete photon loss and partial photon loss during the photon transmission. After the amplification, we can not only increase the fidelity of the target state, but also solve the decoherence problem simultaneously. Based on the above features, our amplification protocol may be useful in future quantum communication.

Linear polarization output performance of Nd:YAG laser at 946 nm considering the energy-transfer upconversion

A theoretical model of quasi-three-level laser system is developed, in which both the thermally induced depolarization loss and the effect of energy-transfer upconversion are taken into account. Based on the theoretical investigation of the influences of output transmission and incident pump power on thermally induced depolarization loss, the output performance of 946 nm linearly polarized Nd：YAG laser is experimentally studied. By optimizing the transmission of output coupler, a 946 nm linearly polarized continuous-wave single-transverse-mode laser with an output power of 4.2 W and an optical-optical conversion efficiency of 16.8% is obtained, and the measured beam quality factors are M2 = 1.13 and My2 = 1.21. The theoretical prediction is in good agreement with the experimental result.

Apelin-13抑制巨噬细胞M1极化缓解全身炎症性骨丢失

背景:Apelin-13因具有抗炎和抗氧化等生物活性,在神经炎症、心血管损伤和肺炎等临床常见疾病中发挥着有效的治疗作用,然而对于Apelin-13在治疗炎症性骨丢失中是否同样具有良好的疗效目前尚无相关基础研究。目的:探究Apelin-13对炎症性骨丢失的治疗作用及其机制,以期探究治疗炎症性骨丢失的潜在药物。方法:①体外实验:将RAW264.7细胞分为3组:对照组,脂多糖组和治疗组。对照组只加入DMEM完全培养基;脂多糖组加入脂多糖(100 ng/mL)诱导炎症DMEM培养基;治疗组加入10 nmol/L Apelin-13+脂多糖诱导炎症DMEM培养基。诱导炎症24 h后,使用Western Blot检测M1型巨噬细胞的标志蛋白诱导型一氧化氮合酶和CD86的表达,并使用细胞免疫荧光染色检测诱导型一氧化氮合酶的表达。并在对照组、脂多糖组和治疗组中同时加入等量的核因子κB受体活化因子配体(50 ng/mL)诱导破骨细胞,诱导6 d后使用抗酒石酸酸性磷酸酶染色和F-actin染色评估破骨细胞诱导的结果。②体内实验:将18只C57BL/6雄性小鼠随机分为3组:假手术组、脂多糖组、治疗组。假手术组连续1周在小鼠腹腔内注射0.1 mL的PBS;脂多糖组注射0.1 mL含脂多糖(5 mg/kg)的PBS稀释液;治疗组注射0.1 mL含脂多糖(5 mg/kg)+Apelin-13(100μg/kg)的PBS稀释液。3组小鼠连续腹腔注射7 d,于第8天处死小鼠,收集每只小鼠的2个股骨,一半进行micro-CT扫描和骨参数分析,另一半进行苏木精-伊红染色。结果与结论:①体外实验:Western Blot结果显示,脂多糖组诱导型一氧化氮合酶和CD86的表达较对照组明显增多,而Apelin-13能够显著抑制脂多糖诱导的巨噬细胞M1极化,细胞免疫荧光的结果也显示治疗组诱导型一氧化氮合酶的表达较脂多糖组减少,同时抗酒石酸酸性磷酸酶染色和F-actin染色结果显示Apelin-13抑制脂多糖诱导的破骨细胞异常活化及骨吸收能力。②体内实验:micro-CT结果显示全身炎性导致股骨远端骨质出现明显丢失,而Apelin-13则能够显著抑制骨质的流失,苏木精-伊红染色结果也表明Apelin-13能够有效缓解炎症诱导的小鼠股骨远端骨质流失。③结果表明:Apelin-13能够通过抑制巨噬细胞M1极化,抑制破骨细胞的异常激活和骨吸收能力,缓解全身炎症诱导的骨丢失。

微波化学动力学

微波促进化学反应具有加热速度快、效率高、选择性加热等优势,对于节能减排具有重要的意义,但在工程应用过程中存在微波功率反射大、加热不均匀和热失控等问题,限制了微波能的进一步应用。为了解决以上问题,设计出高效的微波化学反应器,必须在宏观上深入研究微波促进化学反应的动力学过程,将电磁场方程、热传导方程和反应动力学方程等多个微分方程相互耦合。然而,现有研究一直缺乏以上方程之间的严格耦合关系。因此,本文介绍了化学反应的极化及微波在化学反应中的耗散,建立了微波促进化学反应过程的宏观动力学耦合模型。首先,梳理了微波化学的宏观动力学耦合模型,并对该模型存在的挑战进行了总结,即现有模型缺乏微波在化学反应中的极化过程及耗散过程。其次,针对微波在化学反应中极化过程的挑战,引入了新的介电特性表征,结果表明,反应体系的介电特性由反应物浓度和生成物浓度的概率分布函数对应的1阶勒让德多项式展开式的系数决定。然后,针对微波在化学反应中耗散过程的挑战,根据能量守恒,引入了新的耗散功率公式,结果表明,微波在反应体系中的耗散由微波在反应物中的耗散、在生成物中的耗散及生成物和反应物耦合产生的耗散等部分组成。最后,通过实例,阐述了微波促进化学反应的宏观动力学应用,以推动微波化学工程化的进一步发展。

全反射棱镜式谐振腔中高斯光束角度误差对本征模式偏振损耗的影响

本文引导学生将“激光原理与技术”课程中所学的高斯光束特性与布儒斯特定律相结合,以全反射棱镜式(TRP:Total Reflection Prism)谐振腔为例,研究了高斯光束在TRP面传输过程中入射角度误差对腔内本征模式偏振损耗的影响,并讨论了腔内本征模式入射角度误差、束腰位置(即束腰到棱镜面的距离)z_(0)和焦参数f等对偏振损耗的影响。结果表明:在一定范围内,随着角度误差的增加,s、p分量偏振损耗增大,最后趋于稳定。同时,对于同一角度误差而言,随着z_(0)和f的增大,s、p分量的偏振损耗减少,且相同的z_(0)和f的增量会引起更小的s、p分量偏振损耗。本文研究结果可对TRP腔内本征模式偏振损耗的降低、腔体结构设计及优化提供一定的理论依据。

Interface Engineering of Titanium Nitride Nanotube Composites for Excellent Microwave Absorption at Elevated Temperature

Currently,the microwave absorbers usually suffer dreadful electromagnetic wave absorption(EMWA)performance damping at elevated temperature due to impedance mismatching induced by increased conduction loss.Consequently,the development of high-performance EMWA materials with good impedance matching and strong loss ability in wide temperature spectrum has emerged as a top priority.Herein,due to the high melting point,good electrical conductivity,excellent environmental stability,EM coupling effect,and abundant interfaces of titanium nitride(TiN)nanotubes,they were designed based on the controlling kinetic diffusion procedure and Ostwald ripening process.Benefiting from boosted heterogeneous interfaces between TiN nanotubes and polydimethylsiloxane(PDMS),enhanced polarization loss relaxations were created,which could not only improve the depletion efficiency of EMWA,but also contribute to the optimized impedance matching at elevated temperature.Therefore,the TiN nanotubes/PDMS composite showed excellent EMWA performances at varied temperature(298-573 K),while achieved an effective absorption bandwidth(EAB)value of 3.23 GHz and a minimum reflection loss(RLmin)value of−44.15 dB at 423 K.This study not only clarifies the relationship between dielectric loss capacity(conduction loss and polarization loss)and temperature,but also breaks new ground for EM absorbers in wide temperature spectrum based on interface engineering.

Harnessing the synergy of perfusable muscle flap matrix and adipose-derived stem cells for prevascularization and macrophage polarization to reconstruct volumetric muscle loss

Muscle flaps must have a strong vascular network to support a large tissue volume and ensure successful engraftment.We developed porcine stomach musculofascial flap matrix(PDSF)comprising extracellular matrix(ECM)and intact vasculature.PDSF had a dominant vascular pedicle,microcirculatory vessels,a nerve network,well-retained 3-dimensional(3D)nanofibrous ECM structures,and no allo-or xenoantigenicity.In-depth proteomic analysis demonstrated that PDSF was composed of core matrisome proteins(e.g.,collagens,glycoproteins,proteoglycans,and ECM regulators)that,as shown by Gene Ontology term enrichment analysis,are functionally related to musculofascial biological processes.Moreover,PDSF􀀀human adipose-derived stem cell(hASC)synergy not only induced monocytes towards IL-10􀀀producing M2 macrophage polarization through the enhancement of hASCs’paracrine effect but also promoted the proliferation and interconnection of both human skeletal muscle myoblasts(HSMMs)and human umbilical vein endothelial cells(HUVECs)in static triculture conditions.Furthermore,PDSF was successfully prevascularized through a dynamic perfusion coculture of hASCs and HUVECs,which integrated with PDSF and induced the maturation of vascular networks in vitro.In a xenotransplantation model,PDSF demonstrated myoconductive and immunomodulatory properties associated with the predominance of M2 macrophages and regulatory T cells.In a volumetric muscle loss(VML)model,prevascularized PDSF augmented neovascularization and constructive remodeling,which was characterized by the predominant infiltration of M2 macrophages and significant musculofascial tissue formation.These results indicate that hASCs’integration with PDSF enhances the cells’dual function in immunomodulation and angiogenesis.Owing in part to this PDSF-hASC synergy,our platform shows promise for vascularized muscle flap engineering for VML reconstruction.

Simultaneous optimization of conduction and polarization losses in CNT@NiCo compounds for superior electromagnetic wave absorption

Polarization and conduction losses are the two most crucial dielectric loss mechanisms for carbon-based composites,but their synergistic effects in different frequency bands need to be further revealed.More importantly,for polarization and conduction losses,the strengthening of one party always comes at the expense of the other,which inevitably limits the overall performance of the absorbers.Herein,we have developed a composite of CNT and NiCo hybrid particles via a scalable wet chemical process and an-nealing method.Through the adjustment of the precursor and the annealing temperature,the conduction and polarization losses of the composite are optimized simultaneously.The optimized samples achieved the full absorption of the X and Ku bands under conditions of low filling rate and thin thickness.Further theoretical and experimental studies have revealed conduction loss and polarization loss laws at different frequency ranges.The synergistic effect of conductive loss and magnetic loss in the low-frequency region ensures that the sample exhibits high microwave dissipation performance.However,in the medium and high-frequency part,the magnetic loss can be almost ignored and the timely replenishment of polar-ization loss keeps the wave-absorbing performance at a high level.The excellent multi-band absorption characteristics make the as-obtained absorbers meet the needs of future applications.

Interplay of polarization,strength,and loss in dielectric films for capacitive energy storage:Current status and future directions

Energy-storage dielectric capacitors have emerged as one of the key technologies for high-power systems such as green energy generation,hybrid/electrical vehicles,pulsed power devices,etc.[1]The high-power feature of dielectric capacitors originates from the fast electrostatic polarization.This is in contrast with the slower electrochemical processes in batteries and supercapacitors.

双频圆极化器

本文提出了一种新型的双频圆极化器,可以在22.1~24.2和30.1~33.2 GHz将入射电磁波分别转化为左旋圆极化波和右旋圆极化波。这两个通道正好覆盖了大气遥感中(23.8±0.2)和(31.4±0.1)GHz的两个观测通道,且此圆极化器在遥感观测通道内的插入损耗小于1 dB,轴比优于1.26,完全满足现有大气遥感在(23.8±0.2)和(31.4±0.1)GHz两个通带中的探测要求。该圆极化器使用了电路谐振的理论构建通带,以等效电路的方式进行初步分析,使用电磁仿真软件进行优化,最终完成了设计。

大入射角双极化频率选择表面设计

频率选择表面(FSS)在多频接收系统中具有广泛的应用,并在不少情形下需要大角度入射和分极化接收。采用十字金属线和贴片设计了一款双极化工作的FSS,能够实现在45°角入射的情况下,透射(55±5)GHz、同时反射(33±5)GHz的信号;且透射的(55±5)GHz信号为垂直极化,反射的(33±5)GHz信号为平行极化,实现了双频带和双极化接收。利用印制电路板技术对该FSS进行样品加工,采用自由空间法进行测试。测试结果与仿真结果具有很好的吻合度。

Record Arctic Ozone Loss in Spring 2020 is Likely Caused by North Pacific Warm Sea Surface Temperature Anomalies

Record ozone loss was observed in the Arctic stratosphere in spring 2020.This study aims to determine what caused the extreme Arctic ozone loss.Observations and simulation results are examined in order to show that the extreme Arctic ozone loss was likely caused by record-high sea surface temperatures(SSTs)in the North Pacific.It is found that the record Arctic ozone loss was associated with the extremely cold and persistent stratospheric polar vortex over February-April,and the extremely cold vortex was a result of anomalously weak planetary wave activity.Further analysis reveals that the weak wave activity can be traced to anomalously warm SSTs in the North Pacific.Both observations and simulations show that warm SST anomalies in the North Pacific could have caused the weakening of wavenumber-1 wave activity,colder Arctic vortex,and lower Arctic ozone.These results suggest that for the present-day level of ozone-depleting substances,severe Arctic ozone loss could form again,as long as certain dynamic conditions are satisfied.

Arctic ozone loss in early spring and its impact on the stratospheretroposphere coupling

The tropospheric impact of Arctic ozone loss events is still debatable.In this study we investigate that question,using the ERA5 reanalysis and long-term integration by a climate-chemistry coupled model(CESM2-WACCM).We begin with the frequency of Arctic ozone loss events.On average,such events occur once in early spring every 14−15 years in ERA5 data and in the model,both of which estimate that roughly 40%of the strong polar vortex events in March are coupled with Arctic ozone loss,the remaining 60%being uncoupled.The composite difference between the two samples might be attributed to the pure impact of the Arctic ozone loss-that is,to ozone loss alone,without the concurrent impact of strong polar vortices.Arctic ozone loss is accompanied by an increase in total ozone in midlatitudes,with the maximum centered in the Central North Pacific.Contrasting Arctic ozone loss events with pure strong polar vortex events that are uncoupled with ozone loss,observations confirm that the stratospheric Northern Annular Mode reverses earlier for the former.For pure strong vortex events in early spring(without Arctic ozone loss),the cold anomalies can extend from the stratosphere to the middle troposphere;when such events are strong,the near surface warm anomalies are biased toward the continents.In contrast,during the other 40%of strong early-spring polar vortex events,those coupled with ozone loss,a concurrent and delayed warming of the near surface over the Arctic and its neighboring areas is observed,due to vertical redistribution of solar radiation by the change in the ozone.

Phenomena in Polarized Disperse Systems Caused by Exchange-Correlation Interaction between Particles

We have studied the self-consistent states of nano- and micro-particle polarized powders and structures consisting of parallel particle chains and have determined conditions under which the static dielectric permittivity of a disperse system is negative. It has been shown that in such system an electric current runs without ohmic losses. We present the arguments for the physics of spontaneous emergence of the electric field in disperse systems made up of electrically neutral particles. It has been determined the influence the phase boundaries of a disperse system has on the origin of spontaneous polarization state. The structures consisting of parallel chains of dielectric particles can exhibit spontaneous polarization. In this case the properties of the spherical structure are similar to those of the ball lightning. It has been established correspondence of the obtained theoretical results with the experimental data available in the literature.

本征耐高温电极化储能聚合物电介质研究进展

具有高能量密度、高耐热性和低介电损耗的介电聚合物是先进电力电子应用的理想材料,例如用于电容器的高温储能薄膜。由于高极化和低介电损耗是两个相互矛盾的性质,因而只能在高介电常数(εr)和较低的损耗之间争取最佳的平衡。对于本征型聚合物电介质,介电常数源于电子、原子和偶极极化。然而由于聚合物分子链的性质,碳氢基电介质的电子和原子极化的介电常数被限制在5以下,偶极极化提高固有介电常数是有效的。为此围绕实现本征偶极玻璃聚合物高介电常数获得高储能密度的同时降低介电损耗的设计策略展开,从主链和侧链角度分析冻结链动力学阻止电子传导降低介电损耗的可行性,同时从电子结构角度揭示抑制传导电流的机制,在保持高εr和高玻璃化转变温度(tg)的同时实现高温下高的储能密度,最后对薄膜电容器用极性聚合物研发的难点和重点进行总结和展望。

压应力对铜铝复合板腐蚀行为的影响

为了获得铜铝复合板在压应力作用下的腐蚀规律,采用螺栓加载方式令铜铝复合板承受不同程度压应力,利用盐雾腐蚀箱对不同压应力下的铜铝复合板进行了腐蚀实验,采用扫描电镜、能谱仪和X射线衍射仪对腐蚀形貌与产物进行了分析,研究了盐雾条件下压应力对铜铝复合板腐蚀形貌、腐蚀失重、腐蚀产物和电化学腐蚀性能的影响,并分析了压应力作用下铜铝复合板的腐蚀机制.结果表明:施加压应力后铜铝复合板腐蚀得到抑制,其腐蚀程度与压应力大小有关.在弹性变形区间内,存在一个压应力最佳值.压应力通过改变界面优先腐蚀倾向影响复合板腐蚀行为.压应力引起塑性变形时,应力释放可以减轻复合板腐蚀程度.铜铝复合板盐雾腐蚀条件下的腐蚀产物为Al_(2)O_(3)、Al(OH)_(3)和AlO(OH).

输电线路中污秽复合绝缘子异常发热研究

以110 kV复合绝缘子为研究对象,开展复合绝缘子表面污秽对异常发热的影响研究。首先,对3支全尺寸复合绝缘子开展不同污秽程度下的红外检测,分析污秽复合绝缘子的红外图谱特征;其次,对硅橡胶平板试样开展吸水性实验,分析污秽对绝缘子吸湿特性、介电性能的影响;最后,在人工气候室中对6种污秽等级的带护套短样开展测试,分析泄漏电流对温升的影响,并基于有限元法分析污秽对绝缘子表面电场分布的影响。研究结果表明:污秽会引起并加剧复合绝缘子异常发热,在高湿度环境下全尺寸样品的污秽等级超过b级后,绝缘子发热温度超过0.5℃,污秽对材料老化的复合绝缘子影响更为显著;污秽复合绝缘子表面电场呈现出‘U’型分布规律,发热区域主要集中在端部护套高场强区域,污秽湿润状态对复合绝缘子场强影响较大,场强最大值由原来的4.8 kV/cm增大为6.2 kV/cm。污秽复合绝缘子异常温升的主要原因是护套及污秽吸水后产生的极化损耗,表面阻性泄漏电流影响较小。该文研究内容可为在线红外诊断工作以及抑制污秽复合绝缘子异常发热问题提供理论参考。

极化效应对Bohr速度能区O^(5+)离子在低密度氢等离子体中的能损影响

基于HIRFL加速器装置的低能束实验平台,实验测量了1.07 MeV(~66.9 keV/u)高电荷态O^(5+)离子穿过中性氢气和部分电离的低密度氢等离子体靶后的能量损失,观测到等离子体中离子能损减小的新实验现象.分别考虑部分电离等离子体对炮弹离子的电荷屏蔽效应以及靶区原子的极化效应(Barkas修正),重新计算了离子能损,讨论了离子能损减小的可能物理机制.研究结果表明:在部分电离的低密度等离子体中,靶区的原子极化效应将显著影响Bohr速度能区离子的能量损失过程.