A historical overview of nano-optics:From near-field optics to plasmonics

Nano-optics is an emergent research field in physics that appeared in the 1980s,which deals with light–matter optical interactions at the nanometer scale.In early studies of nano-optics,the main concern focus is to obtain higher optical resolution over the diffraction limit.The researches of near-field imaging and spectroscopy based on scanning near-field optical microscopy(SNOM)are developed.The exploration of improving SNOM probe for near-field detection leads to the emergence of surface plasmons.In the sense of resolution and wider application,there has been a significant transition from seeking higher resolution microscopy to plasmonic near-field modulations in the nano-optics community during the nano-optic development.Nowadays,studies of nano-optics prefer the investigation of plasmonics in different material systems.In this article,the history of the development of near-field optics is briefly reviewed.The difficulties of conventional SNOM to achieve higher resolution are discussed.As an alternative solution,surface plasmons have shown the advantages of higher resolution,wider application,and flexible nano-optical modulation for new devices.The typical studies in different periods are introduced and characteristics of nano-optics in each stage are analyzed.In this way,the evolution progress from near-field optics to plasmonics of nano-optics research is presented.The future development of nano-optics is discussed then.

Modeling Near-Field Impulsive Waves Generated by Deformable Landslide Using the HBP Model Based on the SPH Method

Landslide-generated impulsive waves(LGWs)in reservoir areas can seriously threaten waterway safety as well as hu-man life and properties around the two side slopes.The risk reduction and mitigation of such a hazard require the accurate prediction of near-field wave characteristics,such as wave amplitude and run-up.However,near-field LGW involves complicated fluid-solid interactions.Furthermore,the wave characteristics are closely related to various aspects,including the geometry and physical features of the slide,river,and body of water.However,the empirical or analytical methods used for rough estimation cannot derive accurate results,especially for deformable landslides,due to their significant geometry changes during the sliding process.In this study,the near-field waves generated by deformable landslides were simulated by smoothed particle hydrodynamics(SPH)based on multi-phase flow.The deformable landslides were generalized as a kind of viscous flow by adopting the Herschel-Bulkley-Papanastasiou(HBP)-based nonNewtonian rheology model.The HBP model is capable of producing deformable landslide dynamics even though the high-speed sliding process is involved.In this study,an idealized experiment case originating from Lituya LGW and a practical case of Gongjiafang LGW were reproduced for verification and demonstration.The simulation results of both cases show satisfactory consistency with the experiment/investigation data in terms of landslide movement and near-field impulsive wave characteristics,thus indicating the applicability and accuracy of the proposed method.Finally,the effects of the HBP model’s rheological parameters on the landslide dynamics and near-field wave characteristics are discussed,providing a parameter calibration method along with sug-gestions for further applications.

Influence of substrate effect on near-field radiative modulator based on biaxial hyperbolic materials

Relative rotation between the emitter and receiver could effectively modulate the near-field radiative heat transfer(NFRHT)in anisotropic media.Due to the strong in-plane anisotropy,natural hyperbolic materials can be used to construct near-field radiative modulators with excellent modulation effects.However,in practical applications,natural hyperbolic materials need to be deposited on the substrate,and the influence of substrate on modulation effect has not been studied yet.In this work,we investigate the influence of substrate effect on near-field radiative modulator based onα-MoO_(3).The results show that compared to the situation without a substrate,the presence of both lossless and lossy substrate will reduce the modulation contrast(MC)for different film thicknesses.When the real or imaginary component of the substrate permittivity increases,the mismatch of hyperbolic phonon polaritons(HPPs)weakens,resulting in a reduction in MC.By reducing the real and imaginary components of substrate permittivity,the MC can be significantly improved,reaching 4.64 forε_(s)=3 at t=10 nm.This work indicates that choosing a substrate with a smaller permittivity helps to achieve a better modulation effect,and provides guidance for the application of natural hyperbolic materials in the near-field radiative modulator.

Experimental study of the effect of gas discharge on ionic liquid electrospray

Ionic liquid electrospray(ILE) in an atmospheric environment is often accompanied by the gas discharge phenomenon. It interferes with the normal operation of the electrospray and the measurement of experimental parameters. In this study, electrospray experiments were conducted on the ionic liquid EMI-BF4. The observations revealed that the operating modes of the ionic liquid depend on the voltage polarity at high voltages. Additionally, a correspondence between the operating mode of ILE and the current signal in the circuit was established. The shape of the liquid cone formed at the needle tip bore a striking resemblance to the plume of corona discharge, suggesting that the motion trajectory of electrons influenced the curvature of the liquid cone. Steamer theory provided a clear explanation for the change in curvature as the voltage increased.

Near-field radiative heat transfer between nanoporous GaN films

Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer,leading to a substantial enhancement of near-field radiative heat transfer(NFRHT).Being a direct bandgap semiconductor,GaN has high thermal conductivity and stable resistance at high temperatures,and holds significant potential for applications in optoelectronic devices.Indeed,study of NFRHT between nanoporous GaN films is currently lacking,hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT.In this work,we delve into the NFRHT of GaN nanoporous films in terms of gap distance,GaN film thickness and the vacuum filling ratio.The results demonstrate a 27.2%increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5.Moreover,the spectral heat flux exhibits redshift with increase in the vacuum filling ratio.To be more precise,the peak of spectral heat flux moves fromω=1.31×10^(14)rad·s^(-1)toω=1.23×10^(14)rad·s^(-1)when the vacuum filling ratio changes from f=0.1 to f=0.5;this can be attributed to the excitation of surface phonon polaritons.The introduction of graphene into these configurations can highly enhance the NFRHT,and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio,which can be explained by the excitation of surface plasmon polaritons.These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control,management and thermal modulation.

Localization for mixed near-field and far-field sources under impulsive noise

In order to solve the problem that the performance of traditional localization methods for mixed near-field sources(NFSs)and far-field sources(FFSs)degrades under impulsive noise,a robust and novel localization method is proposed.After eliminating the impacts of impulsive noise by the weighted out-lier filter,the direction of arrivals(DOAs)of FFSs can be estimated by multiple signal classification(MUSIC)spectral peaks search.Based on the DOAs information of FFSs,the separation of mixed sources can be performed.Finally,the estimation of localizing parameters of NFSs can avoid two-dimension spectral peaks search by decomposing steering vectors.The Cramer-Rao bounds(CRB)for the unbiased estimations of DOA and range under impulsive noise have been drawn.Simulation experiments verify that the proposed method has advantages in probability of successful estimation(PSE)and root mean square error(RMSE)compared with existing localization methods.It can be concluded that the proposed method is effective and reliable in the environment with low generalized signal to noise ratio(GSNR),few snapshots,and strong impulse.

Near-Field Wireless Power Transfer, Sensing and Communication with Bessel Beams

The Bessel beam,characterized by its unique non-diffracting properties,holds promising applications.In this paper,we provide a detailed introduction and investigation into the theory and research of the Bessel beam,with a special focus on its generation and applications in the near-field region.We provide an introduction to the concepts,properties,and foundational theories of the Bessel beam.Additionally,the current study on generating Bessel beams and their applications is categorized and discussed,and potential research challenges are proposed in this paper.This review serves as a solid foundation for researchers to understand the concept of the Bessel beam and explore its potential applications.

Towards Near-Field Communications for 6G:Challenges and Opportunities

Extremely large-scale multiple-input multiple-output(XL-MIMO)and terahertz(THz)communications are pivotal candidate technologies for supporting the development of 6G mobile networks.However,these techniques invalidate the common assumptions of far-field plane waves and introduce many new properties.To accurately understand the performance of these new techniques,spherical wave modeling of near-field communications needs to be applied for future research.Hence,the investigation of near-field communication holds significant importance for the advancement of 6G,which brings many new and open research challenges in contrast to conventional far-field communication.In this paper,we first formulate a general model of the near-field channel and discuss the influence of spatial nonstationary properties on the near-field channel modeling.Subsequently,we discuss the challenges encountered in the near field in terms of beam training,localization,and transmission scheme design,respectively.Finally,we point out some promising research directions for near-field communications.

Near-Field Beam Training for Holographic MIMO Communications: Typical Methods, Challenges and Future Directions

Holographic multiple-input multiple-output(HMIMO)has become an emerging technology for achieving ultra-high frequency spectral efficiency and spatial resolution in future wireless systems.The increasing antenna aperture leads to a more significant characterization of the spherical wavefront in near-field communications in HMIMO scenarios.Beam training as a key technique for wireless communication is worth exploring in this near-field scenario.Compared with the widely researched far-field beam training,the increased dimensionality of the search space for near-field beam training poses a challenge to the complexity and accuracy of the proposed algorithm.In this paper,we introduce several typical near-field beam training methods:exhaustive beam training,hierarchical beam training,and multi-beam training that includes equal interval multi-beam training and hash multi-beam training.The performances of these methods are compared through simulation analysis,and their effectiveness is verified on the hardware testbed as well.Additionally,we provide application scenarios,research challenges,and potential future research directions for near-field beam training.

Identification,structure elucidation and origin of a common pyridinium-thiocyanate intermediate in electrospray mass spectrometry among the benziamidazole-class proton pump inhibitors

During the analysis of benziamidazole-class irreversible proton pump inhibitors,an unusual mass spectral response with the mass-to-charge ratio at[Mt10]t intrigued us,as it couldn't be assigned to any literature known relevant structure,intermediate or adduct ion.Moreover,this mysterious mass pattern of[Mt10]t has been gradually observed by series of marketed proton pump inhibitors,viz.omeprazole,pantoprazole,lansoprazole and rabeprazole.All the previous attempts to isolate the corresponding component were unsuccessful.The investigation of present work addresses this kind of signal to a pyridinium thiocyanate mass spectral intermediate(10),which is the common fragment ion of series of labile aggregates.The origin of such aggregates can be traced to the reactive intermediates formed by acid-promoted degradation.These reactive intermediates tend to react with each other and give raise series of complicated aggregates systematically in a water/acetonitrile solution by electrospray ionization.The structure of the corresponding pyridinium thiocyanate species of omeprazole(10a)has been eventually characterized with the help of synthetic specimen(10a′).Our structural proposal as well as its origin was supported by in situ nuclear magnetic resonance,chemical derivatization and colorimetric experiments.

Rapid authentication of different herbal medicines by heating online extraction electrospray ionization mass spectrometry

The rapid and accurate authentication of traditional Chinese medicines(TCMs)has always been a key scientific and technical problem in the field of pharmaceutical analysis.Herein,a novel heating online extraction electrospray ionization mass spectrometry(H-oEESI-MS)was developed for the rapid and direct analysis of extremely complex substances without the requirement for any sample pretreatment or pre-separation steps.The overall molecular profile and fragment structure features of various herbal medicines could be completely captured within 10–15 s,with minimal sample(<0.5 mg)and solvent consumption(<20μL for one sample).Furthermore,a rapid differentiation and authentication strategy for TCMs based on H-oEESI-MS was proposed,including metabolic profile characterization,characteristic marker screening and identification,and multivariate statistical analysis model validation.In an analysis of 52 batches of seven types of Aconitum medicinal materials,20 and 21 key compounds were screened out as the characteristic markers of raw and processed Aconitum herbal medicines,respectively,and the possible structures of all the characteristic markers were comprehensively identified based on Compound Discoverer databases.Finally,multivariate statistical analysis showed that all the different types of herbal medicines were well differentiated and identified(R^(2)X>0.87,R^(2)Y>0.91,and Q^(2)>0.72),which further verified the feasibility and reliability of this comprehensive strategy for the rapid authentication of different TCMs based on H-oEESI-MS.In summary,this rapid authentication strategy realized the ultra-high-throughput,low-cost,and standardized detection of various complex TCMs for the first time,thereby demonstrating wide applicability and value for the development of quality standards for TCMs.

Modular Extremely Large-Scale Array Communication:Near-Field Modelling and Performance Analysis

This paper investigates the wireless communication with a novel architecture of antenna arrays,termed modular extremely large-scale array(XLarray),where array elements of an extremely large number/size are regularly mounted on a shared platform with both horizontally and vertically interlaced modules.Each module consists of a moderate/flexible number of array elements with the inter-element distance typically in the order of the signal wavelength,while different modules are separated by the relatively large inter-module distance for convenience of practical deployment.By accurately modelling the signal amplitudes and phases,as well as projected apertures across all modular elements,we analyse the near-field signal-to-noise ratio(SNR)performance for modular XL-array communications.Based on the non-uniform spherical wave(NUSW)modelling,the closed-form SNR expression is derived in terms of key system parameters,such as the overall modular array size,distances of adjacent modules along all dimensions,and the user's three-dimensional(3D)location.In addition,with the number of modules in different dimensions increasing infinitely,the asymptotic SNR scaling laws are revealed.Furthermore,we show that our proposed near-field modelling and performance analysis include the results for existing array architectures/modelling as special cases,e.g.,the collocated XL-array architecture,the uniform plane wave(UPW)based far-field modelling,and the modular extremely large-scale uniform linear array(XL-ULA)of onedimension.Extensive simulation results are presented to validate our findings.

电喷雾推力器单发射点电流模型及稳定性分析

为促进对纯离子模式下电喷雾推力器的深入理解,分析了电喷雾推力器单发射点受力、供液及离子蒸发行为,建立了发射电流理论模型,明确了电压、供液装置流阻等参数对发射电流的影响规律。所得结果与现有实验数据吻合良好。基于所得模型,进而对单发射点顶端用于发射离子的凸起结构进行了瑞利稳定性分析,得到了单发射点稳定发射的电流上限,并分析了流阻对电流上限的影响。结果表明:发射电流为外加电压的二次函数,与供液装置的流阻成反比关系;纯离子模式存在一个稳定发射电流上限,超过此上限,凸起结构便会破碎;流阻越大,发射电流上限越大。

声振和静电场耦合作用下漏电介质平面液膜的线性不稳定性

在超声电喷推力器中,声振与电场力共同作用使得液膜界面失稳破裂,进而发射液滴并产生推力.为了揭示超声电喷推力器中液膜初始失稳的物理机制,针对超声与电场力耦合作用下液膜的线性不稳定性进行了理论研究.基于Floquet理论,对声振和静电场耦合作用下漏电介质平面液膜进行了线性不稳定性分析,求解了扰动增长率、频率与波数之间的色散关系,通过绘制色散曲线,获得电学、振荡及物性参数对线性失稳的影响规律.结果表明,根据极板间距与液膜厚度之比的不同,液体电导率和介电常数对不稳定性的影响规律会发生改变.当参数不稳定区域增长率较大时,电场力的增强会促进失稳,而当参数不稳定区域增长率较小时,电场力的增强会抑制失稳.

宽范围微牛顿量级场致发射电推力器设计

针对空间引力波探测任务卫星无拖曳控制对微牛顿量级场发射电推力器的宽、稳、准、快、久指标要求,需突破宽范围可调与分辨率和推力噪声之间的相互限制,从场发射推力产生的原理出发,并利用高精度单摆对模型精度进行标定,建立了基于流量、电压主动调节策略的推力调控模型,结合调控分辨率与响应速度的需求,提出的反馈控制策略使推力器在更宽推力范围内维持低推力噪声水平。最后对研制的推力器样机开展了性能表征,实现了0.86~83.54μN、<0.1μN的推力分辨率、在毫赫兹频段<0.1μN/Hz^(1/2)的推力噪声和定工质流量下<10 ms的推力响应时间。

离子液体电喷推力器工作机理研究进展

离子液体电喷推力器易于小型化,具有比冲高、推力精度高的特点,适用于微小卫星、太空引力波探测等领域,具有较大发展潜力。对电喷工作机理的认识与研究,不仅能够促进离子液体电喷推力器在工程中的应用,同时也为未来的进一步发展奠定基础。基于此,本文首先回顾了电喷推力器的发展历程及现状;其次以离子液体电喷推力器3个基础工作过程为出发点,对其锥射流形成及发射机理、束流模式及引出特性、羽流自中和机制进行了基础理论介绍与研究现状的总结;最后对离子液体电喷推力器未来的工作机理研究方向和工程应用发展方向提出展望。

电流体雾化双液滴电聚结行为研究

电流体喷印技术具有分辨率高,溶液参数适应性广等优点,是新型显示制造工艺创新突破的重要载体之一,可用于OLED微米厚度有机TFE膜高效制造。为深入探索电流体雾化技术制备微纳液膜过程,解决现阶段对液膜制备过程中各因素作用机理了解不清的问题,基于相场方法建立了液滴电聚结两相流耦合模型,分析了制备过程中“双液滴电聚结”单元。研究外加电压、基板接触角、液滴间隙和直径对液滴聚结的影响,并总结了液滴可聚结工艺参数相图。研究结果表明,外加电压越大、液滴隙径比越小,聚结后液滴高径比越大,聚结越快;基板接触角越大,聚结后高径比越大,聚结越慢,甚至可能使液滴无法聚结。在亲水基板上外加适当电压或增加液滴密度缩短液滴间隙有助于促成基板上液滴电聚结.该研究结论和工艺相图可应用与电流体雾化制膜时工艺参数调控。

无鞘流毛细管电泳-电喷雾串联质谱用于面粉中荧光增白剂的高灵敏检测

食品中残留的过量荧光增白剂(FWAs)对人体健康存在潜在威胁,因此,开发准确、高灵敏的FWAs检测方法在食品安全监测方面具有重要意义。本工作提出了利用无鞘流接口的毛细管电泳-电喷雾串联质谱(CE-ESI-MS/MS)的方法,以实现面粉样品中6种FWAs的高灵敏检测。实验采用超声辅助液相萃取法进行样品前处理,以减小复杂样品中基质效应的干扰。以氯仿-甲醇(3∶2,v/v)溶液作为萃取剂,在30℃下对样品中的FWAs进行萃取。萃取完成后,经离心、氮气吹干后用氯仿-甲醇(1∶4,v/v)复溶后检测。无鞘流CE-ESI-MS/MS方法采用正离子(ESI+)和多反应监测(MRM)模式,利用二级质谱对6种目标物同时进行定性定量分析,从而提高方法的检测通量和灵敏度。结果显示,本方法具有较宽的线性范围、良好的线性关系和较低的方法检出限(0.04~0.67 ng/g),在实际样品中3个水平下的加标回收率良好(86.2%~103.7%),日间和日内重复性(RSD)分别不大于11.5%和10.2%。上述研究表明,本方法适用于复杂基质中多种FWAs的准确、高灵敏检测,在面粉样品的质量评估和FWAs的污染监控方面具有潜在的应用价值。

基于核壳结构微囊构建三维牙髓细胞球及初步体外研究

目的:利用同轴静电液滴技术设计并制备一种用于牙髓干细胞(DPSCs)三维细胞球体构建、培养的核壳微囊。方法:获取临床收集DPSCs并通过流式细胞仪进行细胞鉴定;构建核壳微囊,调节内外相溶液浓度、流速和细胞密度等参数,对比微囊形貌及尺寸筛选最佳制备条件;活/死染色和CCK-8实验检测微囊内的细胞球的细胞活性,免疫荧光染色观察细胞骨架。结果:成功分离培养DPSCs,构建以海藻酸钠(Alg)为壳层和羧甲基纤维素(CMC)为核层的载细胞微囊。当细胞密度为1×108个/mL时,微囊内的DPSCs在24 h内能自发形成直径为(101.93±10.11)μm的单一球体。活/死染色显示培养7 d内细胞存活率未明显降低(P>0.05),CCK-8显示培养4 d时细胞增殖率增加至(114.91±7.70)%(P<0.05),7 d时增长至(169.05±5.29)%(P<0.001)。细胞在微囊内形成致密结构。结论:该方法制备的核壳微囊可以促进DPSCs形成三维细胞球并长期存活。

Impacts of Model Mismatch and Array Scale on Channel Estimation for XL-HRIS-Aided Systems

Extremely large-scale hybrid reconfigurable intelligence surface(XL-HRIS),an improved version of the RIS,can receive the incident signal and enhance communication performance.However,as the RIS size increases,the phase variations of the received signal across the whole array are nonnegligible in the near-field region,and the channel model mismatch,which will decrease the estimation accuracy,must be considered.In this paper,the lower bound(LB)of the estimated parameter is studied and the impacts of the distance and signal-tonoise ratio(SNR)on LB are then evaluated.Moreover,the impacts of the array scale on LB and spectral efficiency(SE)are also studied.Simulation results verify that even in extremely large-scale array systems with infinite SNR,channel model mismatch can still limit estimation accuracy.However,this impact decreases with increasing distance.