A phenomenological model of the fundamental power coupler for a superconducting resonator

In this study,a phenomenological model of the radio frequency(RF)behavior of a superconducting cavity fundamental power coupler is proposed by analyzing the simulation results of a transient beam-loading process in an extremely overcoupled superconducting cavity.Using this phenomenological model,the calculation of the transient reflected power from a superconducting cavity under beam loading can be mathematically simplified to algebraic operations without solving the differential equation governing the transient beam-loading process,while maintaining the calculation accuracy.Moreover,this phenomenological model can facilitate an intuitive understanding of the significant surge in the time evolution of reflected power from a superconducting cavity in certain beam-loading processes.The validity of this phenomenological model was carefully examined in various beam-loading processes and cavity conditions,and the method based on this phenomenological model was utilized in the transient RF analysis of the superconducting cavity system of the CAFe Linac,achieving satisfactory results.

Design study on medium beta superconducting half-wave resonator at IMP

A 325-MHz superconducting half-wave resonator has been designed with β = 0.51. Three shapes of the inner conductors(race track, ring shape and elliptical shape) were optimized to decrease the peak electromagnetic fields and minimize the dissipated RF power on the cavity walls. In order to suppress the operation frequency shift caused by fluctuations of the helium pressure and maximize the tuning ranges, the frequency shifts and mechanical properties were studied on the electric and magnetic areas. The helium vessel was designed to keep the mechanical structure as robust as possible.

Ion track-based nanowire arrays with gradient and programmable diameters towards rational light management

Integrating nanowires with nonuniform diameter and random spatial distribution into an array can afford unconventional and additional means for modulating optical response.However,experimental realization of such a nanowire array is quite challenging.In this work,we propose a new fabrication strategy which takes advantage of ion track technology,via sequential swift heavy ion irradiation and ion track etching.Based on this strategy,we unprecedentedly realize nanowire arrays,using gold as an example,with gradient and programmable diameters in a controlled manner.We further demonstrate that such nanowire arrays can support broadband,tunable,and enhanced plasmonic responses.We believe that our new type of nanowire arrays will find great potential in applications such as light management and optoelectronic devices.

单根金纳米锥的空间分辨等离激元特性

具有不对称形状和渐变尺寸的纳米锥在宽光谱响应方面具有广阔的应用前景。其中,单根纳米锥在表面等离激元引起的吸收/散射增强以及表面增强光谱等方向应用潜力巨大。在本工作中,我们利用快重离子辐照模板,再通过径迹蚀刻和电沉积工艺成功制备出直径渐变的单根金纳米锥结构。随后,利用扫描电子显微镜、透射电子显微镜和光学暗场成像对金纳米锥进行了形貌和结构表征。进一步的暗场散射光谱表明,单根金纳米锥具有良好的宽带响应特性和多种偏振模式。同时,FDTD(时域有限差分)数值模拟结果表明,宽带等离激元响应主要源于单根金纳米锥直径的渐变和其导致的表面等离激元共振模式的渐变。本项工作为制备高质量的金纳米锥提供了一种创新的方法,也为深入研究单根金属纳米锥的宽带响应特性提供了较为系统的理论和实验证据。

Nonreciprocal unconventional photon blockade in a spinning optomechanical system

We propose how to achieve quantum nonreciprocity via unconventional photon blockade(UPB) in a compound device consisting of an optical harmonic resonator and a spinning optomechanical resonator. We show that, even with very weak single-photon nonlinearity, nonreciprocal UPB can emerge in this system, i.e., strong photon antibunching can emerge only by driving the device from one side but not from the other side. This nonreciprocity results from the Fizeau drag, leading to different splitting of the resonance frequencies for the optical counter-circulating modes. Such quantum nonreciprocal devices can be particularly useful in achieving backaction-free quantum sensing or chiral photonic communications.

Comparison of three remotely sensed drought indices for assessing the impact of drought on winter wheat yield

Agricultural drought threatens food security.Numerous remote-sensing drought indices have been developed,but their different principles,assumptions and physical quantities make it necessary to compare their suitability for drought monitoring over large areas.Here,we analyzed the performance of three typical remote sensing-based drought indices for monitoring agricultural drought in two major agricultural production regions in Shaanxi and Henan provinces,northern China(predominantly rain-fed and irrigated agriculture,respectively):vegetation health index(VHI),temperature vegetation dryness index(TVDI)and drought severity index(DSI).We compared the agreement between these indices and the standardized precipitation index(SPI),soil moisture,winter wheat yield and National Meteorological Drought Monitoring(NMDM)maps.On average,DSI outperformed the other indices,with stronger correlations with SPI and soil moisture.DSI also corresponded better with soil moisture and NMDM maps.The jointing and grain-filling stages of winter wheat are more sensitive to water stress,indicating that winter wheat required more water during these stages.Moreover,the correlations between the drought indices and SPI,soil moisture,and winter wheat yield were generally stronger in Shaanxi province than in Henan province,suggesting that remote-sensing drought indices provide more accurate predictions of the impacts of drought in predominantly rain-fed agricultural areas.

Human activity and climate change triggered the expansion of rocky desertification in the karst areas of Southwestern China

It is conducive to the sustainable development of human beings in karst regions to research the mechanism of karst rocky desertification(KRD)expansion.Whether the large-scale KRD in southwestern China is caused by climate change or human activities is still controversial.In this study,the evolution of the KRD in southwestern China over the past 2000 years was reconstructed through the high-precisionδ^(13)C record of stalagmites from Shijiangjun(SJJ)Cave,Guizhou Province,China.Theδ^(13)C of the stalagmites from SJJ Cave exhibited heavy values from the Medieval Warm Period(MWP)to the Little Ice Age(LIA).Furthermore,theδ^(13)C records of other stalagmites and tufa from southwestern China also showed the same significant heavy trend.Because the stalagmiteδ^(13)C could record the change of ecological environment,it indicated that the consistent change of the stalagmitesδ^(13)C may record the process of KRD expansion in the karst regions of southwestern China.During the MWP,the stronger Asian summer monsoon and the northward movement of the rain belt led to a dry period in southwestern China and a wet period in northern China.In contrast,it was wet in southwestern China and dry in northern China during the LIA.In addition,after the Jing-Kang event(JK event,AD1127)occurred at the end of the Northern Song dynasty,the political and economic center of China migrated to southern China for the first time,which changed the population distribution pattern of larger population in the north and smaller population in the south.Therefore,the expansion of KRD in southwestern China was exacerbated in the MWP due to the change of climate in southwestern China,the migration of a large number of people,wars,the large-scale reclamation of arable land,and the cultivation of large areas of crops.

High Performance Top-Emitting Organic Light-Emitting Diodes for Super Video Graphics Array Monochromatic Microdisplays Application

We have demonstrated a high perlbrmance top-emitting organic light-emitting diode （TEOLED） achieving a brightness of 1000 cd/m^2 at a low voltage of 3.4 V, a power efficiency of 55.2 lm/W at a brightness of 611cd/m^2. and a low efficiency roll-off 5.1% calculated from the maximum efficiency value to that of 5000 cd/m^2. Such im- proved properties are controlled by electron injection from 7-diphenyl-1,10-phenanthroline （BPhen） into and trans- port by the 2,4,6-tris[3＇-（pyridin-3-yl）biphenyl-3-yl]-l,3,5-triazine （TmPPPyTz） layer along with hole injection from 4,4＇,4＂-tris（N-carbazolyl）diphenylamine （TcTa） directly into the fac-tris（2-phenylpyridine）iridium [lr（ppy）3] highest occupied molecular level （HOMO）, leading to direct carrier recombination and excitons formation on the phosphor dopants. Eventually we integrated our high performance TEOLEDs on complementary metal oxide semi- conductor （CMOS） substrates to realize super video graphics array （SVGA） OLED microdisplays.