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.

Infrared Fault Detection Method for Dense Electrolytic Bath Polar Plate Based on YOLOv5s

Electrolysis tanks are used to smeltmetals based on electrochemical principles,and the short-circuiting of the pole plates in the tanks in the production process will lead to high temperatures,thus affecting normal production.Aiming at the problems of time-consuming and poor accuracy of existing infrared methods for high-temperature detection of dense pole plates in electrolysis tanks,an infrared dense pole plate anomalous target detection network YOLOv5-RMF based on You Only Look Once version 5(YOLOv5)is proposed.Firstly,we modified the Real-Time Enhanced Super-Resolution Generative Adversarial Network(Real-ESRGAN)by changing the U-shaped network(U-Net)to Attention U-Net,to preprocess the images;secondly,we propose a new Focus module that introduces the Marr operator,which can provide more boundary information for the network;again,because Complete Intersection over Union(CIOU)cannot accommodate target borders that are increasing and decreasing,replace CIOU with Extended Intersection over Union(EIOU),while the loss function is changed to Focal and Efficient IOU(Focal-EIOU)due to the different difficulty of sample detection.On the homemade dataset,the precision of our method is 94%,the recall is 70.8%,and the map@.5 is 83.6%,which is an improvement of 1.3%in precision,9.7%in recall,and 7%in map@.5 over the original network.The algorithm can meet the needs of electrolysis tank pole plate abnormal temperature detection,which can lay a technical foundation for improving production efficiency and reducing production waste.

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.

Integration of Electrical Properties and Polarization Loss Modulation on Atomic Fe–N‑RGO for Boosting Electromagnetic Wave Absorption

Developing effective strategies to regulate graphene’s conduction loss and polarization has become a key to expanding its application in the electromagnetic wave absorption(EMWA)field.Based on the unique energy band structure of graphene,regulating its bandgap and electrical properties by introducing heteroatoms is considered a feasible solution.Herein,metal-nitrogen doping reduced graphene oxide(M–N-RGO)was prepared by embedding a series of single metal atoms M–N_(4) sites(M=Mn,Fe,Co,Ni,Cu,Zn,Nb,Cd,and Sn)in RGO using an N-coordination atom-assisted strategy.These composites had adjustable conductivity and polarization to optimize dielectric loss and impedance matching for efficient EMWA performance.The results showed that the minimum reflection loss(RL_(min))of Fe–N-RGO reaches−74.05 dB(2.0 mm)and the maximum effective absorption bandwidth(EAB_(max))is 7.05 GHz(1.89 mm)even with a low filler loading of only 1 wt%.Combined with X-ray absorption spectra(XAFS),atomic force microscopy,and density functional theory calculation analysis,the Fe–N_(4) can be used as the polarization center to increase dipole polarization,interface polarization and defect-induced polarization due to d-p orbital hybridization and structural distortion.Moreover,electron migration within the Fe further leads to conduction loss,thereby synergistically promoting energy attenuation.This study demonstrates the effectiveness of metal-nitrogen doping in regulating the graphene′s dielectric properties,which provides an important basis for further investigation of the loss mechanism.

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.

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。

基于极化-去极化电流法的老化PVC电缆绝缘性研究

电缆老化会使绝缘失效,导致短路乃至火灾事故的发生。为研究低压电缆老化后的绝缘性能,对电缆中采用的聚氯乙烯(PVC)绝缘材料进行加速老化实验,通过对样本极化-去极化的电流数据进行分析,得到直流电导率、低频介质损耗因数等参数的变化规律,并利用热失重和傅里叶红外光谱测试老化样本的理化性能。结果表明,随着老化时间的增加,极化电流、去极化电流、电导率和低频介质损耗因数均增大。热失重分析和傅里叶红外光谱分析结果则进一步表明,长时间的高温老化会使PVC电缆绝缘的氯含量减少,阻燃性降低,PVC分子链断裂,羟基、甲基、亚甲基和C=C等官能团含量增加,电缆老化加剧,最终导致电缆的绝缘性下降。

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。

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.

高频方波电场-温度场作用下环氧树脂介电特性劣化协同效应

高频变压器环氧树脂固封绝缘系统长期承受高频方波电压应力和热应力,环氧树脂在高频方波电压应力和热应力下的绝缘性能劣化严重制约着高频变压器的运行可靠性。以往研究多在交流正弦电场与温度场作用下对环氧树脂介电特性进行分析,缺乏环氧树脂在高频方波电场-温度场作用下介电特性变化的研究。搭建高频方波电压与温度联合老化实验平台,对不同老化电场强度、温度条件下环氧树脂样片进行介电特性研究,并将电热联合老化结果与单独热老化、电老化结果进行对比分析。实验结果表明,电热联合老化对环氧树脂介电特性的影响更显著,且大于电、热的叠加作用,即电热联合老化过程中存在着协同效应。通过构建环氧树脂在高频方波电压下的极化损耗计算模型,阐明了在高频方波电场作用下,由环氧树脂极化损耗引起的样片温度升高是加剧环氧树脂介电特性劣化的重要原因。该研究结果可为高频变压器绝缘状态评估提供参考。

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。

4.5m极轨气象卫星接收系统典型故障分析与解决

本文介绍了极轨气象卫星接收系统4.5 m天线的FY-3气象卫星资料接收系统的组成以及功能,对4.5 m天线在接收过程中出现的极化问题、AGC电平过低以及用自动跟踪功能接收信号出现丢帧的现象的问题进行了详细的分析。通过一系列的测试准确定位故障的原因,并针对故障提出了解决方案,有效地提高了卫星云图的接收质量,明显减少了数据包的丢帧数,提高了业务水平。

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.