Focus control of wide-angle metalens based on digitally encoded metasurface

Based on the principle of super-symmetric lens with quadratic phase gradient transformation, combined with the principle of digital coding of metasurface, we propose a wide-angle coded metalens for focusing control in two-dimensional space. This metalens achieves focus shift in the x-direction by changing the oblique incidence angle of the incident wave,and focus control in the y-direction by combining with the convolution principle of the digitally coded metasurface to achieve flexible control of light focusing in the two-dimensional plane. The metasurface unit is mainly composed of threelayer of metal structure and two layers of medium, and the transmission phase is obtained by changing the middle layer of metal structure, which in turn obtains the required phase distribution of the metalens. The design of the metalens realizes the function of the lens with a large viewing angle at the x-polarized incidence, and realizes two-dimensional focus control. Experimentally, we prepared the designed coding metalens and tested the focus control function of the wide-angle coding metalens. The experimental results are in good agreement with the design results.

A wide-angle wave control method of reducing torque ripple for brushless DC motor

In order to deal with torque pulsation problem caused by traditional control method for brushless DC （BLDC） motor and to achieve high precision and good stability, a novel control strategy is proposed. Compared with the traditional control scheme, by using phase voltage as a control objective and making waveform of phase current approximately quasi-sinusoidal, torque ripple of BLDC motor is reduced from the original 14% to 3.4%, while toque is increased by 3.8%. Furthermore, by detecting zero-crossings of back electromotive force （BEMF） with non-conducting phases, sensorless control is realized. The new control strategy is simple. It can minimize torque ripple, increase torque, and realize sensorless control for BLDC motor. Simulation and experiments show good performance of BLDC motor by using the new control method.

Wide-angle incidence and P-wave transmission

Polarity reversals may occur to transmitted P waves if the incidence angle is greater than the critical incidence angle. We analyze the characteristics of reflection and transmission coefficients under the condition of wide incidence angle based on Zoeppritz equations. We find that for specific conditions, as the incidence angle increases, the characteristic curve of the transmitted P-wave coefficient enters the third quadrant from the first quadrant through the origin, which produces a transition in the transmitted P wave and the corresponding coefficient experiences polarity reversal. We derive the incidence angle when the transmitted P-wave coefficient is zero and verify that it equals zero by using finite-difference forward modeling for a single-interface model. We replace the water in the model reservoir by gas and see that the reservoir P-wave velocity and density decrease dramatically. By analyzing the synthetic seismogram of the transmitted P wave in the single-interface model, we show that the gas-saturated reservoir is responsible for polarity reversal.

Comparison of scleral buckling using wide-angle viewing systems and indirect ophthalmoscope for rhegmatogenous retinal detachment

AIM：To compare the effects of scleral buckling using wide-angle viewing systems（WAVS） with that using indirect ophthalmoscope for the treatment of rhegmatogenous retinal detachment.METHODS：The study was a retrospective analyses of the medical records of 94 eyes（94 patients） with rhegmatogenous retinal detachment.Among them,47 eyes underwent scleral buckling using WAVS with endoiiluminator（Group W）,and 47 eyes underwent scleral buckling using indirect ophthalmoscope（Group I）.Surgical durations,primary success rate,best-corrected visual acuities（BCVA）,delayed subretinal fluid absorptions and surgical complications were compared between the two groups.RESULTS：At baseline,there were no statistical differences between the two groups in patient＇s age（P=0.997）,gender（P=0.853）,symptom duration（P=0.216）,BCVA（P=0.389）,refractive error（P=0.167）,intraocular pressure（P=0.595）,the number of retinal breaks（P=0.832）,the extent of retinal detachment（P =0.246）,subretinal demarcation line（P=0.801）,and macular detachment（P=0.811）.The follow-up period was 12 mo.The surgical durations in Group W（with or without encircling buckling） were significant shorter than those in Group I（P〈0.001 respectively）.The primary success rate was94.27%in Group W,which was similar to that in Group I（92.38%,P=0.931）.The BCVA in Group W was better than that in Group I（P〈0.001） at 1-month follow-up visit.However,there were no significant differences between the two groups at 3-month（P=0.221）,6-month（P =0.674）,and 12-month（P=0.363） follow-up visits respectively.Delayed subretinal fluid absorptions were more common in Group I than in Group W at 1-month（P=0.045） follow-up visit,but there were no significant differences between the two groups at 3-month（P=0.111）,6-month（P =1.000） and 12-month follow-up visits respectively.CONCLUSION：Scleral buckling using WAVS can be an alternative choose for rhegmatogenous retinal detachment

Crustal structure of the eastern Dabie orogenic belt from the seismic tomography and wide-angle reflection studies

The studies of seismic tomography and wide-angle reflection have been carried out to reveal the velocity structUrebeneath the eastern Dabie orogenic belt. The result from the seismic tomography shows the high velocity bodiesmight be positioned to a depth of only about 1 .5 km below sea level within the Dabie ultra-high pressure metamorphic (UHPM) belt; the fan-profile shows the Shuihou-Wuhe fault, the demarcation between the South Dabieand the North Dabie, slopes to the south-west at a dip angle of about 45° in the bottom of upper crust. The wideangle reflection shows the middle crustal boundaries and the complex features from the lower crust.

Velocity structure in the South Yellow Sea basin based on first-arrival tomography of wide-angle seismic data and its geological implications

The South Yellow Sea basin is filled with Mesozoic-Cenozoic continental sediments overlying pre-Palaeozoic and Mesozoic-Palaeozoic marine sediments.Conventional multi-channel seismic data cannot describe the velocity structure of the marine residual basin in detail,leading to the lack of a deeper understanding of the distribution and lithology owing to strong energy shielding on the top interface of marine sediments.In this study,we present seismic tomography data from ocean bottom seismographs that describe the NEE-trending velocity distributions of the basin.The results indicate that strong velocity variations occur at shallow crustal levels.Horizontal velocity bodies show good correlation with surface geological features,and multi-layer features exist in the vertical velocity framework(depth:0–10 km).The analyses of the velocity model,gravity data,magnetic data,multichannel seismic profiles,and drilling data showed that high-velocity anomalies(>6.5 km/s)of small(thickness:1–2 km)and large(thickness:>5 km)scales were caused by igneous complexes in the multi-layer structure,which were active during the Palaeogene.Possible locations of good Mesozoic and Palaeozoic marine strata are limited to the Central Uplift and the western part of the Northern Depression along the wide-angle ocean bottom seismograph array.Following the Indosinian movement,a strong compression existed in the Northern Depression during the extensional phase that caused the formation of folds in the middle of the survey line.This study is useful for reconstructing the regional tectonic evolution and delineating the distribution of the marine residual basin in the South Yellow Sea basin.

Crustal wide-angle reflection imaging along Lianxian-Gangkou profile in Guangdong province,China

A 400 km-long wide-angle seismic experiment along Lianxian-Gangkou profile in South China was carried out to study contact relationship between southeast continental margin of Yangtze block and northwest continental margin of Cathaysia block. We reconstructed crustal wide-angle reflection structure by the depth-domain pre-stack migration and the crustal velocity model constructed from the traveltime fitting. The wide-angle reflection section shows different reflection （from crystalline basement and Moho） pattern beneath the Yangtze and Cathaysia blocks, and suggests the Wuchuan-Sihui fault is the boundary between them. A cluster of well-developed reflections on Moho and in its underlying topmost mantle probably comes from alternative thin layers, which may be seismic signature of strong interaction between crust and mantle in the tectonic environment of lithosphere extension.

Characteristics of crustal variation and extensional break-up in the Western Pacific back-arc region based on a wide-angle seismic profile

The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 545-kmlong active-source ocean bottom seismometer(OBS)wide-angle reflection/refraction profile in the East China Sea.The P wave velocity model shows that the Moho depth rises significantly,from approximately 30 km in the East China Sea shelf to approximately 16 km in the axis of the Okinawa Trough.The lower crustal high-velocity zone(HVZ)in the southern Okinawa Trough,with V_(p) of 6.8-7.3 km/s,is a remarkable manifestation of the mantle material upwelling and accretion to the lower crust.This confirms that the lower crustal high-velocity mantle accretion is developed in the southern Okinawa Trough.During the process of back-arc extension,the crustal structure of the southern Okinawa Trough is completely invaded and penetrated by the upper mantle material in the axis region.In some areas of the southern central graben,the crust may has broken up and entered the initial stage of seafloor spreading.The discontinuous HVZs in the lower crust in the back-arc region also indicate the migration of spreading centers in the back-arc region since the Cenozoic.The asthenosphere material upwelling in the continent-ocean transition zone is constantly driving the lithosphere eastward for episodic extension,and is causing evident tectonic migration in the Western Pacific back-arc region.

Accuracy Analysis of Low Altitude Photogrammetry with Wide-angle Camera

Firstly,the relationship between the accuracy of low altitude aerial photogrammetry and the field angle of camera is made by a quantitative analysis from the theory.The conclusion that the low altitude photogrammetry should use wide-angle camera as much as possible is done.Then,the limitation of the single lens camera to expand field angle and the combined wide-angle camera existing on the market not suitable for light load of low altitude UAV(Unmanned Aerial Vehicle)due to excessive weight are pointed out.The characteristics of combined wide-angle low altitude light camera with self-calibration and self-stabilization developed by the author are described,especially the principle of self-calibration for the combination of static error and dynamic error.Based on the practice of large scale mapping,a technical procedure in aerial photography by taking with wide-angle camera and large overlap simultaneously for improving the accuracy of low altitude photogrammetry is proposed.The typical engineering produced data is used to verity the above theoretical analysis.A technical route for increasing accuracy of low altitude photogrammetry with combined wide-angle camera is expounded.

基于区间Pythagorean模糊WA算子的TOPSIS多属性群决策研究

针对区间Pythagorean模糊的混合型多属性群决策问题,构建基于区间Pythagorean模糊集的WA算子模型,并提出了一种基于区间Pythagorean模糊TOPSIS决策方法。首先,基于决策者权重与属性权重完全未知的基础下,将区间Pythagore-an模糊应用到TOPSIS群决策中;其次,利用区间Pythagorean模糊数WA算子将多个决策者评价矩阵集合成综合评价矩阵,并基于TOPSIS决策方法计算各个方案的相对贴近度;最后,通过产业与高校耦合创新算例分析解释验证了本文方法的合理性与有效性。

Wide-angle and broadband graded-refractive-index antireflection coatings

The design and fabrication of graded-refractive-index （GRIN） antireflection （AR） coatings with wide-angle and broadband characteristics are demonstrated. The optimization of the graded-index profiles with a genetic algorithm is used in the design of the GRIN AR coatings. The average reflectance over a wavelength range from 400 nm to 800 nm and angles of incidence from 0° to 80° could be reduced to only 0.1% by applying an optimized AR coating onto BK7 glass. The optimization of step-graded GRIN AR coating is then further investigated in detail. A two-layer AR coating was deposited by electron beam evaporation with glancing angle deposition technology, and the positional homogeneity was improved by depositing the film from two opposite directions. The microstructure of the AR coating was investigated by scanning electron microscopy, and the residual reflectances of the coating sample are in agreement with theoretical calculations. The optimized GRIN AR coatings are beneficial to increasing the efficiency of light utilization.

A flexible ultra-broadband metamaterial absorber working on whole K-bands with polarization-insensitive and wide-angle stability

For potential military applications, a flexible metamaterial absorber(MMA) working on whole K-bands with totalthickness of 3.367 mm, ultra-broadband, polarization-insensitive, and wide-angle stability is presented based on frequencyselective surface(FSS). The absorber is composed of polyvinyl chloride(PVC) layer, polyimide(PI) layer, and poly tetra fluoro ethylene(PTFE) layer, with a sandwich structure of PVC–PI–PTFE–metal plate. Periodic conductive patterns play a crucial role in the absorber, and in traditional, it is designed on the upper surface of PI layer to form LC resonance. Different from commonly absorber, all the patterns are located on the lower surface of the PI layer in this work, and hence the impedance matching and absorptivity are improved in this purposed absorber. The flexible absorber with patterns on lower surface of the PI layer is compared with that on upper surface of the PI layer, the difference and the reasons are explained by absorption mechanism based on equivalent circuit model, and surface current density and electric field distribution are used to analyze resonance peaks. Absorptivity is greater than 90% in a frequency range of 10.47 GHz–45.44 GHz with relative bandwidth of 125.1%, covering the whole Ku, K, Ka, and some of X, U bands, especially containing the whole K bands from 12 GHz to 40 GHz. Radar cross section(RCS) is reduced at least 10 dB in 11.48 GHz–43.87 GHz frequency ranges,and absorption remained about 90% when the incident angle changed from 0°to 55°. The purposed absorber is fabricated,measured, and experiment results show good agreement with theoretical analysis and numerical simulation. After bonded on outer surface of different cylinders with diameters of 200 mm and 100 mm, the absorption of MMA is approximately reduced 10% and 20% respectively, which shows good conformal character with surface of various curvatures. Due to the attractive performance on strong absorption in the whole K-bands, flexible and easy conformal, our design exhibits broad potential application in radar stealth and sensors.

存量语境中的再造日常——2023WA中国建筑奖获奖作品观察

本文对2023年WA中国建筑奖的获奖作品进行了综合评述。通过对各获奖项目的分析,展示了建筑界在面对当代挑战时的多重探索,突出了建筑在社会、文化和环境方面的重要作用。在可持续发展日益重要的今天,建筑不仅仅是为了满足当下的需求,更是为了创造持久而有意义的空间,为未来的发展提供可能性与指引。

18Cr2Ni4WA钢渗碳工艺的确定

18Cr2Ni4WA为航空常用合金渗碳钢,渗碳质量的稳定性直接影响到产品的可靠性与使用寿命。通过工艺试验确定出18Cr2Ni4WA钢不同渗碳层深度时的渗碳温度、渗碳时间、碳势等工艺参数。结果表明:随渗碳时间的增加,渗碳层深度呈抛物线规律增加,渗碳试样进行等温淬火后,采用金相测定法可更快速地测定渗碳层深度。

18Cr2Ni4WA钢渗碳后的渗层深度测定

研究了18Cr2Ni4WA钢渗碳后其渗层深度的测定方法,280℃等温淬火后采用金相法测定渗层深度时,容易获得渗层和心部间的清晰边界,最有利于渗层深度的测量;淬火和回火处理后也可以采用金相法测定其渗层深度,但较难识别其过渡区。采用维氏硬度法测定18Cr2Ni4WA钢渗层深度的流程较为复杂,且受材料、热处理工艺的影响,但能够反映经最终热处理后该钢的性能。

NPU-WA系列风力机翼型设计与风洞实验

针对兆瓦级大型风力机,研究发展了以具有更优良高雷诺数和高升力气动性能为特点的NPU-WA翼型族,风洞实验表明,该翼型族达到了在高雷诺数、高升力条件下实现高升阻比和外侧翼型对粗糙度不敏感的主要设计要求,为我国自主研发大型风力机提供了可以实际使用的翼型几何数据和雷诺数范围内1.0×106～5.0×106的风洞实验数据。

基于walkaway VSP下行P波的TTI各向异性参数反演

本文基于弱各向异性(WA)介质的正反演公式和qP波的坐标变换,推导了利用qP波反演任意倾斜对称轴的横向各向同性(TTI)介质的各向异性参数和对称轴方向的公式.理论和数值实验表明,利用2个相互正交的变井源距垂直地震剖面(walkaway VSP)可以完全确定钻井中TTI介质qP波的3个WA参数和对称轴的2个方向参数.我们完成了几个由不同数量剖面组成的walkaway VSP模拟实验,使用TTI模型和一般各向异性模型对模拟数据进行了反演,证明了反演公式的正确性和可靠性.使用这些公式,对来自Java Sea的由3条剖面组成的walkaway VSP观测数据进行了各向异性反演,获得了钻井中接收点处介质的WA参数.

Wa株轮状病毒感染昆明小鼠乳鼠腹泻模型的建立及影响因素考察

目的:建立人源性Wa株轮状病毒感染昆明小鼠乳鼠腹泻动物模型。方法:采用不同接种方式(口服、注射)、不同滴度、不同剂量的Wa株轮状病毒感染4 d龄昆明小鼠乳鼠,观察昆明小鼠乳鼠的体征反应、腹泻率和腹泻程度;选择腹泻率和腹泻程度较高的条件进行模型的稳定性考察,观察体征反应、腹泻率、腹泻程度、小肠形态学等指标改变。结果:采用强饲法,Wa株轮状病毒滴度为10-3.3/25μL TCID50,被轮状病毒攻击24 h后出现腹泻表现,低剂量(50μL/只)病毒组及中剂量(100μL/只)病毒组腹泻率及腹泻程度较低,高剂量(200μL/只)病毒组感染后第1天(1 dpi)腹泻率可达80%,腹泻程度达3.0,连续4 d保持腹泻状态,在各剂量组中腹泻率和腹泻程度最高;采用高剂量病毒组的实验方法,扩大造模动物的数量进行验证,1 dpi乳鼠腹泻率为80.0%,腹泻程度达3.1,并连续4 d保持腹泻状态。结论:4 d龄昆明小鼠乳鼠被Wa株轮状病毒经口攻击后,病毒能够使昆明小鼠乳鼠出现腹泻表现,且腹泻率和腹泻程度与病毒滴度、剂量相关。所建模型方法简便、重现性好,可作为比较理想的动物模型用于抗RV感染的药物治疗效果评价。

北半球冬季WA遥相关型影响东亚初夏季风的可能途径

通过 SVD和滞后相关分析 ,研究了北半球冬季 WA遥相关型与后期初夏东亚季风的联系及可能的影响途径。结果表明 ,北半球冬季 WA型与东亚初夏季风存在密切的联系 ,其影响东亚初夏季风的过程可概述为 :在北半球冬季 ,WA型强弱可引起西北大西洋海温异常 ,由于海温具有很好的持续性 ,这种海温异常可一直持续到春季和初夏 6月份 ;而春季和初夏 6月份 ,北大西洋海温异常又反过来对大气环流产生影响 ,引起欧亚中高纬大气环流异常 ,特别是初夏 6月西北欧以及乌拉尔山和鄂霍茨克海附近的大气环流的异常 。

基于WA方法的2013年夏秋越南东南外海暖涡初步分析

使用WA涡旋自动识别方法对2013年夏秋两季越南东南外海暖涡进行识别和追踪,同时利用同期CTD资料对该暖涡的内部结构和性质进行分析。结果显示:该暖涡于2013年夏初初步形成、呈单核结构,主要体现在跃层之下、100 m以深处,受暖涡影响的水体呈高温、低盐、低密特性,温盐等值线明显下凹。经过整个夏季的发展壮大,该暖涡在8—9月达到强盛且演化为双核结构,其西侧涡核强于东侧涡核,东侧涡核发育更快。发育最充分时涡旋纬向直径可达427 km,中心海平面高度异常达28.75 cm,最大振幅达6.04 cm,最大涡动能为384 cm2/s2,而涡旋强度则在涡旋形成之初达到最大值1.59×10-2cm2/s2km2。与夏初相比,秋季该暖涡的垂向上界提升到40 m,且在90—100 m最为显著。在100 m以浅,双核结构中西侧涡核更加强大、发育更加充分;从110 m层开始,西侧涡核中心北移且强度开始减弱,东侧涡核有所加强;在140 m层以下海域,西侧涡核基本消失,但东侧涡核仍然继续存在,其对盐度的影响持续到190 m层,对温度和密度的影响在200 m层仍可见。