分类： 力学 >> 力学其他学科 提交时间： 2024-08-13 合作期刊: 《应用力学学报》
摘要： Nb3Sn超导相转变中的力电耦合效应给超导磁体装备的电磁性能指标和安全运行带来不利影响。鉴于Nb3Sn具有立方相和四方相两种相结构,建立了Nb3Sn立方相、四方相和混合相晶体力学模型,以及考虑变形-临界温度退化和变形-正常态电阻率变化的力电耦合响应模型。研究结果表明,相结构会导致单晶体弹性力学性能有所区别,但静水压作用下不同相结构的Nb3Sn多晶体,其局部应力状态与相结构无关,仅取决于晶粒形貌和取向。由于不同的相结构在外载下的费米面上电子态密度的演变规律基本一致,使得变形诱导的临界温度退化行为对相结构没有依赖性。对于混合相Nb3Sn正常态电阻率变化而言,温度低于马氏体相变温度时,可以采用基于电子-电子散射假设得到的T2规律来描述; 当温度高于马氏体相变温度时,由于四方相向立方相的转变,需要考虑电-声子耦合作用对正常态电阻率的贡献,可以采用拓展的Woodard-Cody电阻率模型来描述宏观电阻率的应变效应。研究结果提高了对不同相的临界性能退化机理的认识。
分类： 力学 >> 力学其他学科 提交时间： 2024-08-13 合作期刊: 《应用力学学报》
摘要： 为推动竹结构的发展,展开基于拓扑优化的竹结构设计新方法开发及相应的静力对比试验研究。首先,探讨了运用渐进结构优化指导竹结构设计的系统性方法; 然后结合工程实例,选用面向承压型结构和受拉型结构进化的两种优化可行域,分别开展双车道桥梁结构优化设计并完成静力对比试验。结果表明:基于优化设计的桥梁结构与Michell型桁架结构较吻合,同体积下结构刚度显著高于经验设计构件; 在正常使用状态下,承压型的拓扑拱结构刚度约为受拉型的拓扑悬索结构的3倍,但承载力相较略低。可见,基于渐进结构优化的新设计方法,可以针对不同的承载力和刚度设计要求,构建合适的优化可行域以指导设计出不同的方案,为工程竹结构提供了一种可自动化分析计算的最优化设计方法。
分类： 医学、药学 >> 预防医学与公共卫生学 提交时间： 2024-08-13
摘要： 背景 类风湿因子（RF）是原发性干燥综合征（pSS）患者中常见的自身抗体，其在疾病中的具体作用尚不完全清楚。目的 探索不同水平RF在 pSS中的临床特点及意义。方法 采用调查研究的方法，纳入2018年12月—2022年9月于中日友好医院中医风湿病科就诊的 262 例 pSS 患者为研究对象。依据 RF 水平将患者分为3组：阴性组137例（RF60 U/mL）。采集 3 组pSS 患者的临床资料，包括一般资料、临床表现、症状评分、血液学指标，采用 χ2 、非参数及趋势检验分析组间差异。结果 262 例 pSS 患者 RF 阳性率为 47.7%（125/262），其中男 14 例（5.3%）、女 248 例（94.7%），中位年龄 57.0（49.0，63.0）岁，平均发病年龄（48.7±11.6）岁，中位病程 60.0（24.0，120.0）个月；3 组 pSS 患者性别、年龄、发病年龄、病程比较，差异均无统计学意义（P>0.05）。pSS 患者常见临床表现前 3 位的依次为：口干 257 例、眼干 247 例、乏力 235 例；高滴度阳性组血液系统受累、关节炎发生率高于阴性组（P<0.05）；随着 RF 滴度的增加，pSS 患者血液系统受累（χ2 趋势 =6.992，P 趋势 =0.008）、关节炎（χ2 趋势 =10.918，P 趋势 =0.001）发生率呈上升趋势。随着 RF 滴度的增加，pSS 患者抗核抗体≥ 1 ∶ 160（χ2 趋势 =40.691，P 趋势 <0.001）、抗干燥综合征相关抗原 A 抗体阳性（χ2 趋势 =26.138，P 趋势 <0.001）、抗 Ro52 核糖核蛋白抗体阳性（χ2 趋势 =31.426，P 趋势 <0.001）、抗干燥综合征相关抗原 B 抗体阳性（χ2趋势 =23.682，P 趋势 <0.001）、红细胞沉降率升高（χ2 趋势 =40.132，P 趋势 <0.001）、免疫球蛋白（Ig）A 升高（χ2 趋势 =7.508，P 趋势 =0.006）、IgG 升高（χ2 趋势 =71.570，P 趋势 <0.001）、补体 3 降低（χ2 趋势 =7.452，P 趋势 =0.006）、中性粒细胞计数降低（χ2 趋势 =8.364，P 趋势 =0.004）、血红蛋白降低（χ2 趋势 =6.390，P 趋势 =0.011）的比例呈上升趋势。结论 随着RF 滴度升高，pSS 患者血清免疫异常、腺体外受累的比例增加；RF 滴度升高对关节炎、血液系统受累具有预测价值。
分类： 医学、药学 >> 预防医学与公共卫生学 提交时间： 2024-08-13
摘要： 背景 骨关节疾病是老年人群常见、多发的慢性疾病，其与更高的死亡率、更多的残疾、功能状态的下降和较低的生命质量显著相关，产生巨大的疾病负担。目前尚无河南省该病流行情况及其影响因素的研究。目的 了解河南省老年人群骨关节疾病流行特征及其影响因素，为其实施精准防控提供科学依据。方法 采用多阶段随机整群抽样方法，通过调查问卷、医学体检、实验室检测等方法，获取 2018 年河南省≥ 18 岁常住居民人口学特征、既往疾病史、身体活动及身体指标等，本研究纳入 1 055 名≥ 60 岁人为研究对象。运用基于复杂抽样构建的多因素Logistic 回归分析河南省不同特征老年人群骨关节疾病特征及其影响因素。结果 2018 年河南省老年人群骨关节疾病患病率（加权后）为 28.13%（95%CI=28.10%~28.15%）。其中女性、城市、超重或肥胖、中心性肥胖、血脂异常或高脂血症、无吸烟史、有打鼾史、中等强度活动的老年人群骨关节疾病患病率更高，差异均有统计学意义（P<0.05）。多因素 Logistic 回归分析显示，男性（OR=0.717，95%CI=0.550~0.933，P=0.013）是老年人群骨关节疾病的保护因素；超重或肥胖（OR=1.329，95%CI=1.050~1.684，P=0.018）、中心性肥胖（OR=1.305，95%CI=1.047~1.626，P=0.018）是老年人群骨关节疾病的危险因素。结论 河南省老年人群骨关节疾病与性别、BMI 和中心性肥胖相关，应对老年人群中女性、超重或肥胖和中心性肥胖者开展针对性健康教育及综合干预。
分类： 物理学 >> 核物理学 分类： 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间： 2024-08-09
摘要： Scanning magnets are devices responsible for deflecting particles to specific locations in particle therapy utilizing spot scanning techniques. To ensure the distortion of the scanned beams’ shapes remains within an acceptable level, it is necessary to guarantee that the homogeneity of the field integrals is sufficiently high in the two transversal directions within the good field region. Typically, this is accomplished by adding shims on both sides of magnet poles. In this study, we innovatively proposed a method to perform multi-objective optimization of shim parameters and excitation currents by the state-of-the-art evolutionary algorithm Non- dominated Sorting Genetic Algorithm-III (NSGA-III). Furthermore computer vision (CV) was implemented to automatically evaluate both the beam shape distortions and the centroids of the scanned beam spots at the target plane to assist efficient optimization process. With this method, optimal parameters of scanning magnets which have capability of scanning a carbon beam of 400 MeV/u beam energy across a 20 cm × 20 cm field size with a source-to-axis distance of 255 cm were obtained successfully. Meanwhile, we also conducted eddy current and temperature rise analysis, laminated steel plates with 19 slits cut near the pole gaps were used to reduce eddycurrents due to rapid variation of magnetic fields during the scanning process. Based on the optimized magnetsparameters, eddy current and temperature analyses were performed and the temperature rises were found to be near 40°C and 54°C for the Y and X magnets respectively at the designed scanning speeds, which meets the requirements for normal operation. This proposed procedure of optimization is expected to facilitate efficient and sophisticated design of various magnets applied to charged particle accelerators.
分类： 核科学技术 >> 核科学技术其他学科 提交时间： 2024-02-01
摘要： Betavoltaic nuclear batteries show promise as compact and enduring power sources for microelectromechanical systems (MEMS). Current theoretical calculations often overlook practical diode characteristics like surface recombination (S), bulk recombination within the space-charge region (R-SCR), series resistance (Rs) and shunt resistance (Rsh), resulting in significant gaps between theoretical predictions and experimental results, with differences in JSC, VOC, or converter efficiency up to tenfold. To address this, a Practical Diode Model, integrating these practical characteristics, is developed via Monte Carlo and Physics-Based Compact Model Co-Simulation.We quantitatively analyze the differential impacts and synergistic effects of these practical characteristics on JSC, VOC, FF, and Pout, highlighting the detrimental effects of S, R-SCR, and Rs, while emphasizing the beneficial role of Rsh. Further analysis of the degree of influence of S, Rs, and Rsh on output power reveals a priority ranking order of Rs, S, and Rsh for Si-based batteries, and S, Rsh, and Rs for SiC-based batteries. This approach effectively bridges the theoretical-experimental gap, evidenced by J-V curves closely matching tested batteries and negligible relative errors of -0.8% to 0.6% between Pout values and their tested counterparts, emphasizing its accuracy in predictions. We predict output performance across material qualities, obtaining achievable powers of 16.82 and 73.90 nW/cm2 for planar Si- and SiC-based batteries, and evaluate the quality levels of existing batteries. Furthermore, our model can forecast the performance of 3D batteries by incorporating an extended electron-hole pair generation rate model into 3D structures, achieving 28 W/cm3 for the 63Ni-Si-based multi-layer battery, surpassing planar silicon and suitable for MEMS applications.
分类： 农、林、牧、渔 >> 土壤学 提交时间： 2024-08-14 合作期刊: 《干旱区科学》
摘要： Wind erosion is a geomorphic process in arid and semi-arid areas and has substantial implications for regional climate and desertification. In the Columbia Plateau of northwestern United States, the emissions from fine particles of loessial soils often contribute to the exceedance of inhalable particulate matter (PM) with an aerodynamic diameter of 10 μm or less (PM10) according to the air quality standards. However, little is known about the threshold friction velocity (TFV) for particles of different sizes that comprise these soils. In this study, soil samples of two representative soil types (Warden sandy loam and Ritzville silt loam) collected from the Columbia Plateau were sieved to seven particle size fractions, and an experiment was then conducted to determine the relationship between TFV and particle size fraction. The results revealed that soil particle size significantly affected the initiation of soil movement and TFV; TFV ranged 0.304–0.844 and 0.249–0.739 m/s for different particle size fractions of Ritzville silt loam and Warden sandy loam, respectively. PM10 and total suspended particulates (TSP) emissions from a bed of 63–90 μm soil particles were markedly higher for Warden sandy loam than for Ritzville silt loam. Together with the lower TFV of Warden sandy loam, dust emissions from fine particles (<100 μm in diameter) of Warden sandy loam thus may be a main contributor to dust in the region's atmosphere, since the PM10 emissions from the soil erosion surfaces and its ensuing suspension within the atmosphere constitute an essential process of soil erosion in the Columbia Plateau. Developing and implementing strategic land management practices on sandy loam soils is therefore necessary to control dust emissions in the Columbia Plateau.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Polarization vectors of light traveling in a coiled optical fiber rotate around its propagating axis even in the absence of birefringence. This rotation was usually explained due to the Pancharatnam-Berry phase of spin-1 photons. Here, we use a purely geometric method to understand this rotation. We show that similar geometric rotations also exist for twisted light carrying orbital angular momentum (OAM). The corresponding geometric phase can be applied in photonic OAM-state-based quantum computation and quantum sensing.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： How migratory birds can find the right way in navigating over thousand miles is an intriguing question, which much interested researchers in both fields of biology and physics for centuries. There several putative proposals that sound intuitively plausible all remain contested so far because those hypothesis-models of magnetoreceptor to sense geomagnetic field need either extremely high sensitivity or humankind-like intelligence to guide. Here we explore theoretically that the birds can navigate to their destination through an entirely new scenario to sense the geomagnetic field. Our proposal is based on separate peaks of the resonance-fluorescence spectrum of a four-level system derived from the ferric sulfide cluster which exists in a protein complex (Drosophila CG8198) of migratory birds. As the separation of spectral peaks contains information about geomagnetic field at both current location and birthland, the change of such separation cues the bird to choose a right direction to move and double-resonance emerges once arrived the destination. Our theoretical mechanism can explain previous experiments on the disorientation of migratory birds caused by oscillating magnetic field naturally and more precisely. This work provides insight to explain migratory navigation and motivates possible manmade practical devices.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We show that the time-averaged Poynting vector in parity-time (PT ) symmetric coupled waveguides is always positive and cannot explain the stopped light at exceptional points (EPs). In order to solve this paradox, we must accept the fact that the fields E and H and the Poynting vector in non-Hermitian systems are in general complex. Based on the original definition of the instantaneous Poynting vector, a formula on the group velocity is proposed, which agrees perfectly well with that calculated directly from the dispersion curves. It explains not only the stopped light at EPs, but also the fast-light effect near it. This investigation bridges a gap between the classic electrodynamics and the non-Hermitian physics, and highlights the novelty of non-Hermitian optics.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Traditional lasers function using resonant cavities, in which the round-trip optical path is exactly equal to an integer multiple of the intracavity wavelengths to constructively enhance the spontaneous emission rate. By taking advantage of the enhancement from the resonant cavity, the narrowest sub-10-mHz-linewidth laser and a $10^{-16}$-fractional-frequency-stability superradiant active optical clock (AOC) have been achieved. However, a laser with atomic spontaneous radiation being destructively inhibited in an anti-resonant cavity, where the atomic resonance is exactly between two adjacent cavity resonances, has not been reported. Herein, we experimentally demonstrate inhibited stimulated emission and termed it an inhibited laser. Compared with traditional superradiant AOCs, which exhibit superiority in terms of the high suppression of cavity noise, the suppression of the cavity-pulling effect of an inhibited laser can be further improved by a factor of $(2F/pi)^2$, i.e., 2.07 in this work, which was improved from 26 to 53 times. This study will guide further development of AOCs with better stability, and thus, it is significant for quantum metrology and may lead to new research in the laser physics and cavity quantum electrodynamics fields.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Resampling by interpolation is the traditional method to process sample in nonunform sampling Fourier transform spectrometer. Nonuniform discrete Fourier transform is an alternative to interpolation that has not been overlooked before. With the aid of experiment, we systematically compare the NUFFT method with resampling by interpolation FFT method in nonuniform sampling Fourier transform spectrometer. We found that NUFFT is comparable to interpolation in spectral profile and spectral noise levels and is better in spectral amplitudes. We also found that It has significant advantage in under-sampling and anti-aliasing property which is offered by the unique non-periodic nature of nonuniform sampling. It is faster and consumes less computer memory in our python implementation. Overall, we found that NUFFT is superior to traditional interpolation method with mostly better performances as well as additional capabilities.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Xiao Sun
Song Liang
Weiqing Cheng
Shengwei Ye
Yiming Sun
Yongguang Huang
Ruikang Zhang
Jichuan Xiong
Xuefeng Liu
John H. Marsh
Lianping Hou
摘要： We report an AlGaInAs multiple quantum well integrated source of polarization controlled light consisting of a polarization mode converter PMC, differential phase shifter(DPS), and a side wall grating distributed-feedback DFB laser. We demonstrate an asymmetrical stepped-height ridge waveguide PMC to realize TE to TM polarization conversion and a symmetrical straight waveguide DPS to enable polarization rotation from approximately counterclockwise circular polarization to linear polarization. Based on the identical epitaxial layer scheme, all of the PMC, DPS, and DFB laser can be integrated monolithically using only a single step of metalorganic vapor phase epitaxy and two steps of III V material dry etching. For the DFB-PMC device, a high TE to TM polarization conversion efficiency 98% over a wide range of DFB injection currents is reported at 1555 nm wavelength. For the DFB-PMC-DPS device, a 60 degree rotation of the Stokes vector was obtained on the Poincar\'e sphere with a range of bias voltage from 0 V to -4.0 V at IDFB is 170 mA.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Light-matter coupling strength and optical loss are two key physical quantities in cavity quantum electrodynamics (cQED), and their interplay determines whether light-matter hybrid states can be formed or not in chemical systems. In this study, by using macroscopic quantum electrodynamics (mQED) combined with a pseudomode approach, we present a simple but accurate method which allows us to quickly estimate the light-matter coupling strength and optical loss without free parameters. Moreover, for a molecular emitter coupled with photonic modes (including cavity modes and plasmon polartion modes), we analytically and numerically prove that the dynamics derived from the mQED-based wavefunction approach is mathematically equivalent to the dynamics governed by the cQED-based Lindblad master equation when the Purcell factor behaves like Lorentzians.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： One of the fundamental challenges in nanophotonics is to gain full control over nanoscale optical elements. The precise spatiotemporal arrangement determines their interactions and collective behavior. To this end, DNA nanotechnology is employed as an unprecedented tool to create nanophotonic devices with excellent spatial addressability and temporal programmability. However, most of the current DNA-assembled nanophotonic devices can only reconfigure among random or very few defined states. Here, we demonstrate a DNA-assembled rotary plasmonic nanoclock. In this system, a rotor gold nanorod can carry out directional and reversible 360 degree rotation with respect to a stator gold nanorod, transitioning among 16 well-defined configurations powered by DNA fuels. The full-turn rotation process is monitored by optical spectroscopy in real time. We further demonstrate autonomous rotation of the plasmonic nanoclock powered by DNAzyme-RNA interactions. Such assembly approaches pave a viable route towards advanced nanophotonic systems entirely from the bottom-up.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Lee-Huang-Yang (LHY) fluids are an exotic quantum matter dominated purely by quantum fluctuations. Recently, the three-dimensional LHY fluids were observed in ultracold atoms experiments, while their low-dimensional counterparts have not been well known. Herein, based on the Gross-Pitaevskii equation of one-dimensional LHY quantum fluids in two-component Bose-Einstein condensates, we reveal analytically and numerically the formation, properties, and dynamics of matter-wave structures therein. Considering a harmonic trap, approximate analytical results are obtained based on variational approximation, and higher-order nonlinear localized modes with nonzero nodes are constructed numerically. Stability regions of all the LHY nonlinear localized modes are identified by linear-stability analysis and direct perturbed numerical simulations. Movements and oscillations of single localized mode, and collisions between two modes, under the influence of different initial kicks are also studied in dynamical evolutions. The predicted results are available to quantum-gas experiments, providing a new insight into LHY physics in low-dimensional settings.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： The key component of nanoplasmonics is metals. For a long time, gold and silver have been the metals of choice for constructing plasmonic nanodevices because of their excellent optical properties. However, these metals possess a common characteristic, i.e., their optical responses are static. The past decade has been witnessed tremendous interest in dynamic control of the optical properties of plasmonic nanostructures. To enable dynamic functionality, several approaches have been proposed and implemented. For instance, plasmonic nanostructures can be fabricated on stretchable substrates or on programmable templates so that the interactions between the constituent metal nanoparticles and therefore the optical responses of the plasmonic systems can be dynamically changed. Also, plasmonic nanostructures can be embedded in tunable dielectric materials, taking advantage of the sensitive dependence of the localized surface plasmon resonances on the neighboring environment. Another approach, which is probably the most intriguing one, is to directly regulate the carrier densities and dielectric functions of the metals themselves.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We propose and study an efficient photonic CDE method using MZI-based coherent optical matrix multiplication. It improves the compensation performance by about 60% when the tap-length is limited, and only 50% taps of the theoretical value is needed for photonic CDE with 1-dB penalty.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Mingming Feng
Baoqing Zhang
Haotian Ling
Zihao Zhang
Yiming Wang
Yilin Wang
Xijian Zhang
Pingrang Hua
Qingpu Wang
Aimin Song
Yifei Zhang
摘要： Plasma frequency is the spectral boundary for low-loss propagation and evanescent decay of surface plasmon polariton (SPP) waves, which corresponds to a high cut-off phenomenon and is typically utilized for identifying SPPs. At terahertz (THz) frequencies, a metal line with periodic metallic grooves can mimic the conventional optical SPPs, which is referred to as designer SPPs. Theoretically, the plasma frequency of THz SPPs decreases as the groove depth increases. Here, by replacing the metallic grooves with graphene sheets, dynamically sweeping SPP plasma frequency is demonstrated for the first time. The metal-graphene hybrid structure comprises a metal line with periodic graphene grooves, a thin-layer ion gel for gating graphene, and metallic tips for uniforming gate field. As the chemical potential changes, the average conductivity of graphene is modulated so that the effective depth of the graphene grooves changes, which sweeps the plasma frequency of THz SPPs consequently. Both simulated and experimental data demonstrate a red shift of plasma frequency from 195 to 180 GHz at a low bias from -0.5 to 0.5 V. The proposed structure reveals a novel approach to control the on/off status of SPP propagation in the THz range.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： An explanation for superluminal phenomena based on wave-particle duality of photons is suggested. A single photon may be regarded as a wave packet, whose spatial extension is its coherence volume. As a photon propagates as a wave train in vacuum, its velocity is just the speed of light. When it tunnels through a barrier as a particle, its wave function collapses and it will travel faster than light. Superluminal propagation can occur only within the coherence length and the time constrained by uncertainty principle. A massive particle cannot be superluminal during the tunneling process. So superluminality does not violate causality. As for the superluminal and negative group velocities in anomalously dispersive medium, they are merely reshaping effect of the pulse, and they will become subluminal at large distances. A couple of experiments are proposed to test the superluminal phenomena.
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