A novel multi-pin rectangular waveguide slow-wave structure based backward wave amplifier at 340 GHz

A backward wave amplifier（BWA） in a terahertz regime with a novel slow-wave structure（SWS） composed of multi parallel grating pins inside a rectangular waveguide is analyzed. The multi-pin rectangular waveguide SWS possesses good performance and is compatible with micro-fabrication technologies. The dispersion and interaction impedance of the multipin SWS are presented. The stopbands of the modes cling together in a Brillouim zone. The SWS has a high interaction impedance that is suitable for the interaction of multi cylindrical beams. The design, which is based on three parallel pins supporting the wave–beam interaction with four cylindrical beams, is verified by three-dimensional particle-in-cell simulations. A BWA with the central frequency at 340 GHz is demonstrated, and the output power is more than 100 mW.A tuning frequency range of 15 GHz（333–348 GHz） is obtained with a gain of more than 20 dB.

A novel slotted helix slow-wave structure for high power Ka-band traveling-wave tubes

A novel slotted helix slow-wave structure （SWS） is proposed to develop a high power, wide-bandwidth, and high reliability millimeter-wave traveling-wave tube （TWT）. This novel structure, which has higher heat capacity than a conven- tional helix SWS, evolves from conventional helix SWS with three parallel rows of rectangular slots made in the outside of the helix tape. In this paper, the electromagnetic characteristics and the beam-wave interaction of this novel structure operating in the Ka-band are investigated. From our calculations, when the designed beam voltage and beam current are set to be 18.45 kV and 0.2 A, respectively, this novel circuit can produce over 700-W average output power in a frequency range from 27.5 GHz to 32.5 GHz, and the corresponding conversion efficiency values vary from 19% to 21.3%, and the maximum output power is 787 W at 30 GHz.

Research of sine waveguide slow-wave structure for a 220-GHz backward wave oscillator

A watt-class backward wave oscillator is proposed, using the concise sine waveguide slow-wave structure combined with a pencil electron beam to operate at 220 GHz. Firstly, the dispersion curve of the sine waveguide is calculated, then, the oscillation frequency and operating voltage of the device are predicted and the circuit transmission loss is calculated. Finally, the particle-in-cell simulation method is used to forecast its radiation performance. The results show that this novel backward wave oscillator can produce over 1-W continuous wave power output in a frequency range from 210 GHz to 230 GHz. Therefore, it will be considered as a very promising high-power millimeter-wave to terahertz-wave radiation source.

Variational analysis of the disc-loaded waveguide slow-wave structures

The variational method is applied to calculate the dispersion characteristics of disc-loaded waveguide slow-wave structures. The parameters describing the waveguide discontinuities in disc-loaded waveguide are calculated by the variational method. Then the dispersion characteristics of slow-wave structures are obtained using lossless microwave quadrupole theory. Good agreement was observed between results of the Variational method and those of field matching method and high frequency structure simulator. In the case of broad band, results of the variational method are better than those of field matching method.

基于Swin Transformer的疟疾细胞图像识别研究

为了协助医务人员更准确、更快速地诊断疟疾,提出一种基于Swin Transformer(SwinT)的疟疾细胞图像识别方案。方案采用伪彩色图像增强算法对血片图像进行预处理,以突出图像的颜色对比度,并引入SwinT模型作为主干网络,解决下采样固定和全局信息无法交互的问题,同时引入卷积层对图像进行线性变换,构建残差网络解决梯度消失和梯度爆炸问题。实验表明,与图像量化等其他图像增强方法相比,本文方法增强了疟疾细胞图像的色彩对比度,改进后方案的准确率达到99.7%,高于现有文献方法,可以对疟疾的辅助治疗带来更有价值的支持。

Radio frequency conditioning of an S-band accelerating structure prototype for compact proton therapy facility

The development of a high-gradient accelerating structure is underway to construct a compact proton linear accelerator for cancer treatment.Extensive experiments and numerous studies are being conducted to develop compact linear accelerators for proton therapy.Optimization of the electromagnetic and mechanical design has been performed to simplify the manufacturing process and reduce costs.A novel high-gradient structure with a low relativistic proton velocity(β),v/c=0.38,was designed,fabricated,and tested at high power.The first full-scale prototype was also successfully tested with high radio frequency(RF)power,a repetition rate of 50 Hz,and pulse length of 3μs to reach a high-gradient of 46 MV/m using a 50 MW S-band klystron power supply obtained from the Shanghai Soft X-ray Free Electron Laser Facility.This is the first high-power test in China,which is in line with the expected experimental goal.This study presents preliminary high-power testing of S-band standing wave accelerating structures with 11 cells.This work aims to verify the feasibility of using a high-gradient RF accelerating structure in compact proton therapy facilities.The cold test of the prototype cavity was completed in advance.Details of the high-power RF test setup,the process of RF conditioning,and the high-power results are described.

Small-signal analysis of a rectangular helix structure traveling-wave-tube

This paper investigates the properties of traveling wave-beam interaction in a rectangular helix traveling-wave-tube （TWT） for a solid sheet electron beam. The ＂hot＂ dispersion equation is obtained by means of the self-consistent field theory. The small signal analysis,which includes the effects of the beam parameters and slow-wave structure （SWS） parameters,is carried out by theoretical computation. The numerical results show that the bandwidth and the small-signal gain of the rectangular helix TWT increase as the beam current increases;and the beam voltage not obviously influences the small signal gain. Among different rectangular helix structures,the small-signal gain increases as the width of the rectangular helix SWS increases,however,the bandwidth decreases whether structure parameters a and L or ψ and L are fixed or not.In addition,a comparison of the small-signal gain of this structure with a conventional round helix is made.The presented analysis will be useful for the design of the TWT with a rectangular helix circuit.

Investigation of a wideband folded double-ridged waveguide slow-wave system

The folded double-ridged waveguide structure is presented and its properties used for wide-band traveling-wave tube are investigated. Expressions of dispersion characteristics, normalized phase velocity and interaction impedance of this structure are derived and numerically calculated. The calculated results using our theory agree well with those obtained by using the 3D electromagnetic simulation software HFSS. Influences of the ridge-loaded area and broad-wall dimensions on the high frequency characteristics of the novel slow-wave structure are discussed. It is shown that the folded double-ridged waveguide structure has a much wider relative passband than the folded waveguide slow-wave structure and a relative passband of 67% could be obtained, indicating that this structure can operate in broad-band frequency ranges of beam-wave interaction. The small signal gain property is investigated for ensuring the improvement of bandwidth. Meanwhile, with comparable dispersion characteristics, the transverse section dimension of this novel structure is much smaller than that of conventional one, which indicates an available way to reduce the weight of traveling-wave tube.

Dispersion characteristics of a slow wave structure with a modified photonic band gap

This paper studies the dispersion characteristics of a modified photonic band-gap slow-wave structure with an open boundary by simulation and experiment. A mode launcher with a wheel radiator and a coupling probe is presented to excite a pure TM01-like mode. The cold test and simulation results show that the TM01-like mode is effectively excited and no parasitic modes appear. The dispersion characteristics obtained from the cold test are in good agreement with the calculated results.

An SCF－MS－Xα Study of the Electronic Structures of Binuclear and Trinuclear Gold（Ⅰ） Compounds

The SCF-Xα-SW molecular orbital calculations were carried out on the modelcompounds of binuclear and trinuclear gold(Ⅰ)using starting potential of Au atom and the Watson sphere.The energy level order of the frontier orbital of a binuclear gold model compound is in agreement with the experimental result.The calculated ionization potential of the binuclear model compound is consistent well with the photoelectron spectrum of Au (Me)(PMe_3).The metal-metal interactions are discussed.The calculated electronic absorption spectra of binuclear and trinuclear gold(Ⅰ)are basically in agreement with experimental results.

Upper crustal structure beneath Southwest Iberia north of the convergent boundary between the Eurasian and African plates

The 3-D P- and S-wave velocity models of the upper crust beneath Southwest Iberia are determined by inverting arrival time data from local earthquakes using a seismic tomo^raphy method. We used a total of 3085 P- and 2780 S-wave high quality arrival times from 886 local earthquakes recorded by a per- manent seismic network, which is operated by the Institute of Meteorology （IM）, Lisbon, Portugal. The computed P- and S-wave velocities are used to determine the 3-D distributions of Vp/Vs ratio. The 3-D velocity and Vp/Vs ratio images display clear lateral heterogeneities in the study area. Significant veloc- ity variations up to ~6% are revealed in the upper crust beneath Southwest lberia, At 4 km depth, both P- and S-wave velocity take average to high values relative to the initial velocity model, while at 12 km, low P-wave velocities are clearly visible along the coast and in the southern parts. High S-wave velocities at 12 km depth are imaged in the central parts, and average values along the coast; although some scattered patches of low and high S-wave velocities are also revealed. The Vp/Vs rztio is generally high at depths of 4 and 12 km along the coastal parts with some regions of high Vp/Vs ratio in the north at 4 km depth, and low Vp/Vs ratio in the central southern parts at a depth of 12 km, The imaged low velocity and high Vp/Vs ratios are related to the thick saturated and unconsolidated sediments covering the region; whereas the high velocity regions are generally associated with the Mesozoic basement rocks.

Lithostructural controls in Douala-Buea Region landscape (SW Cameroon margin):Insights from morphometric analysis

The Douala-Buea Region(DBR;4°-5°N,9°-10°30’E),a portion of the southern Cameroon passive margin,developed on the Proterozoic granito-gneissic basement and the Cretaceous to Recent volcanosedimentary cover,was explored in order to evaluate the lithology and tectonics controls on its landscape usingthequalitativeandquantitative geomorphological analyses based on 30 m resolution Digital Elevation Models(DEM)and field evidences.This area displays an uneven and complex landscape differentiated into four morphological units:Douala,Nkondjock,Kumba and Buea Units.The Douala Unit corresponds to the Coastal Plain and is extended on the Douala-Kribi/Camposedimentarybasin.The Nkondjock Unit represents a middle plateau developed on a Proterozoic granito-gneissic basement.The Kumba Unit matches with the southernmost volcanic Western Cameroon High Plateau.The Buea Unit corresponds to the Mount Cameroon stratovolcano.The relief analysis through mountain-front sinuosity(Smf,1.19–1.43)and relative relief ratio(Rr,0.10–2.31)vary from one unit to another.The drainage network analysis including drainage patterns,stepped longitudinalriverprofiles,theassociated morphometric indexes,notably the concavity index(IC,0.56–0.88),deviation(D,267–2912 m),basin asymmetry factor(A_(F),6.37–42.12),hypsometric integral(HI,0.10–0.29),valley floor width to valley height ratio(V_(f),0.36–2.75),elongation ratio(R_(e),0.30–0.50),watershed slope(S,6.88–88.88)and stream length gradient index(SL,0–3332)vary from one basin to another too.These results also show the heterogeneous and uneven DBR landscape controlled by its lithology and active tectonics.The drainage system reveals concave to concavo-convex longitudinal river profile shapes with knick points,asymmetric basins,and fault reactivations,and highlights the tectonics activity that used to occur through the time and their control on the morphology.Together,they document the lithostructural controls on the DBR landscape evolution,extendable in the whole SW Cameroon margin.

Study on the electronic structures of REBaCuO superconductors and their relation to superconductivity

Electronic structures of REBaCuO (RE=La, Pr, Nd, Sm, Gd, Dy, Ho and Er)systems were calculated by means of SCF-Xα -SW methods. Results show that there is an inner-orbitcoupling for these oxide superconductor systems. The inner-orbit coupling was resulted from theinteraction of two electronic orbits of RE 5p and O 2s, since they have similar energy state levelsand relatively larger orbital electronic clouds. Compared with experimental facts, it is also foundthat the overlap in space between the two orbits has a similar tendency to T_c and the number ofenrolling electrons has a close relation to J_c, therefore, the influence of inner-orbit coupling onsuperconductivity could not be overlooked.

英语联觉音sw-的概念结构及文化规范研究

联觉音是指语音和所构词具有某种相似含义的语素。英语联觉音sw-相关语词不仅内隐了三个概念结构“运动-扩大”“运动-大量”“运动-速和降”,而且栖息着“过度不好”和“自我膨胀不好”等文化价值规范。

细茎石斛多糖DMP4a-1的结构特性及免疫活性研究

目的研究从细茎石斛中分离纯化得到的酸性多糖DMP4a-1的结构性质,初步鉴定其免疫调节活性。方法 应用高效 凝胶渗透色谱(HPGPC),TLC,GC,GC．MS,IR,高碘酸氧化等方法进行组成结构分析,采用双抗夹心ELISA法检测巨噬细胞TNF-α 分泌水平、用CCK-8试剂进行脾淋巴细胞增殖实验。结果 细茎石斛水溶性酸性多糖DMP4a-1平均相对分子质量为3 049,主 要由葡萄糖,甘露糖,鼠李糖,阿拉伯糖和半乳糖组成,其分子摩尔数之比为2．873:2．850:1．762:1．279:l,糖链结构中存在1→ 4,1→3及1→6糖苷键,且摩尔数比为1．194:2．430:1。体外实验证明,DMP4a-1可明显刺激巨噬细胞分泌TNF-α,促进脾淋巴细 胞增殖。结论细茎石斛多糖DMP4a-1是一种β-D-吡喃杂多糖,在结构上与抗肿瘤多糖类似,富含1→3糖苷键,具有免疫增 强功能。

紧凑型L波段磁绝缘线振荡器的实验研究

设计加工了一个紧凑型L波段磁绝缘线振荡器(MILO)并进行了实验研究。该MILO具有一个新型收集极和一个新型模式转换器,射频扼流腔减为一个,同时将阴极杆设计成变阻抗结构,该MILO由一台自建的600kV,8Ω,100ns加速器SPARK 01驱动。在二极管电压为515～538kV,二极管电流为58～61kA的条件下,该MILO在实验中获得了1.76～1.78GHz,2.2～2.5GW的TM01模高功率微波辐射,功率转换效率为7.3%～7.9%。在30ns的有效电压脉宽下,实验中测得微波脉冲半高宽为15ns。实验结果与模拟结果符合得较好。

从西南天山超高压变质带多期构造变形看天山古生代构造演化

通过对西南天山阿克雅孜和木扎尔特地区高压-超高压变质带构造几何学和岩石变形相关运动学的详细剖析,厘定出高压-超高压变质岩石及其相关围岩的构造单元。详细研究表明,研究区可划分为三个构造单元:北部单元、中部单元和南部单元。确定了每个构造单元的构造几何学特征及各个构造单元之间的相互关系。通过分析岩石变形特征和叠加关系,确定了岩石所记录多期变形的运动学特征。根据研究区的多期构造变形特点,建立了阿克雅孜和木扎尔特河地区构造演化序列。共划分出四期构造可识别的事件(E1-E4),分别代表了E1:高压-超高压岩石折返过程;E2:高压-超高压岩石造山带的早期改造过程;E3:北部构造事件对高压-超高压造山带影响;E4:走滑构造对高压-超高压造山带的叠加。沿造山带系列构造分析表明,西南天山高压-超高压带中发育的四期构造事件沿中天山北缘具有很好的一致性,各期构造事件也有一定的横向可对比性。在此基础上通过对多期变形事件的构造背景的探讨,建立了整个天山在古生代的构造拼合过程,揭示我国西部洋壳相关的深俯冲造山带形成过程和参与深俯冲作用(超)高压变质岩的变形变质历史。

南海西南次海盆声呐浮标地震测深资料研究

利用声纳浮标资料 ,得到了南海西南次海盆地壳的速度结构。确定海盆中沉积物的速度为1.6～3.9km/s,基底顶面速度为4.2～6.8km/s。确定海盆中存在洋壳。海盆中基底起伏较大 ,埋深为4400～5700m ,很多地方的基底上只有一层300～500m厚的低速沉积层 ,而缺少其它上第三系的沉积物。海盆中沉积物的厚度为300～1500m ,时代为晚渐新世～第四纪 ,由此推测西南次海盆的扩张开始时间应该为早渐新世。

THz返波管圆波导梳状慢波结构的研究

该文利用三维电磁仿真软件模拟计算了THz圆波导梳状慢波结构的负1次返波的色散和耦合阻抗。结果证实:在430-570GHz频带内,慢波结构内半径为0.175mm,约为中心频率波长的0.292倍;在760-940GHz的频带内,慢波结构内半径为0.1mm,是中心频率处波长的0.392倍。该结构较大的径向尺寸有利于提高电子注通过率。这种结构负1次返波的耦合阻抗较小,基本上小于1Ω,很好解释了现有THz返波管的电子效率小于0.01%的事实。