A limit theorem for the solutions of slow–fast systems with fractional Brownian motion

A limit theorem which can simplify slow–fast dynamical systems driven by fractional Brownian motion with the Hurst parameter H inside the（1/2, 1） interval has been proved. The slow variables of the original system can be approximated by the solution of the simplified equations in the sense of mean square. An example is presented to illustrate the applications of the limit theorem.

Time-Delay Effects on Synchronization of Coupled Slow-Fast Systems

Time-delay effects on synchronization features of delay-coupled slow-fast van der Pol systems are investigated in the present paper. The synchronization mechanism of “slow-manifold adjustment” is firstly described on the basis of geometric singular perturbation theory. Then, the impact of time delay on the structure of the slow manifold of synchronized system is obtained by using the method of stability switch, and thus, time-delay effects on synchronization features are stated. It is shown the time delay cannot qualitatively affect the synchronization mechanism, however, it can result in the drift of the optimal coupling strength.

Comparison of the Fabric Mechanical Properties Measured by the KESF and FAST Systems

In order to clarify the connections and differences be.tween KES- F and FAST, fifteen polyester- based fab-rics were selected and the experiments were strictly mea-sured. The test results between the two systems in termsof mechanical properties were compared, and highly sig-nificant correlation between two systems were obtaineddespite some considerable differences in the measurementprinciples of KES - F and FAST systems.

Construction of 3D porous Cu_(1.81)S/nitrogen-doped carbon frameworks for ultrafast and long-cycle life sodium-ion storage

Transition metal sulfides have great potential as anode mterials for sodium-ion batteries(SIBs)due to their high theoretical specific capacities.However,the inferior intrinsic conductivity and large volume variation during sodiation-desodiation processes seriously affect its high-rate and long-cyde performance,unbeneficial for the application as fast-charging and long-cycling SIBs anode.Herein,the three-dimensional porous Cu_(1.81)S/nitrogen-doped carbon frameworks(Cu_(1.81)S/NC)are synthesized by the simple and facile sol-gel and annealing processes,which can accommodate the volumetric expansion of Cu_(1.81)S nanoparticles and accelerate the transmission of ions and electrons during Na^(+)insertion/extraction processes,exhibiting the excellent rate capability(250.6 mA·g^(-1)at 20.0 A·g^(-1))and outstanding cycling stability(70% capacity retention for 6000 cycles at 10.0 A·g^(-1))for SIBs.Moreover,the Na-ion full cells coupled with Na_(3)V_(2)(PO_(4))_(3)/C cathode also demonstrate the satisfactory reversible specific capacity of 330.5 mAh·g^(-1)at 5.0 A·g^(-1)and long-cycle performance with the 86.9% capacity retention at 2.0 A·g^(-1)after 750 cycles.This work proposes a promising way for the conversionbased metal sulfides for the applications as fast-charging sodium-ion battery anode.

Stability and oscillations in a slow-fast flexible joint system with transformation delay

Flexible joints are usually used to transfer velocities in robot systems and may lead to delays in motion transformation due to joint flexibility. In this paper, a linkrotor structure connected by a flexible joint or shaft is firstly modeled to be a slow-fast delayed system when moment of inertia of the lightweight link is far less than that of the heavy rotor. To analyze the stability and oscillations of the slowfast system, the geometric singular perturbation method is extended, with both slow and fast manifolds expressed analytically. The stability of the slow manifold is investigated and critical boundaries are obtained to divide the stable and the unstable regions. To study effects of the transformation delay on the stability and oscillations of the link, two quantitatively different driving forces derived from the negative feedback of the link are considered. The results show that one of these two typical driving forces may drive the link to exhibit a stable state and the other kind of driving force may induce a relaxation oscillation for a very small delay. However, the link loses stability and undergoes regular periodic and bursting oscillation when the transformation delay is large. Basically, a very small delay does not affect the stability of the slow manifold but a large delay affects substantially.

Design of programmable high-accuracy telemetric fast collection system

A programmable high-accuracy system was proposed to collect and process telemetric fast varying signals,which consists of pre-circuit,analog-to-digital（A/D）conversion unit and signal collection and processing part.Performance analysis demonstrates that this novel telemetry-acquisition method is a potential solution to rapidly process fast varying signals and efficiently utilize telemetry channel.

基于灰度均值的自适应FAST角点检测优化算法

光照不均、突变引起的灰度变化会影响图像特征检测效果。为此,设计一种基于灰度均值的自适应FAST-9-12角点检测算法。首先,利用特征点的延展性设计一种小面积双重检测模板,减少像素点与中心点的比较次数,提高区域正检率和检测速度;其次,依据图像局部灰度均值,在每个像素点检测模板内自适应调整阈值,避免灰度变化影响检测效果;最后,根据柔性非极大值抑制的思想设计角点半径抑制原则,筛选鲁棒性更强的角点。在Inria遥感影像数据集上的实验结果表明,FAST-9-12角点检测速度比FAST-12-16,FAST-9-16两种模板提高22%左右,因自适应阈值的提取方式不易受光照影响,检测准确率分别提高4.16和3.11个百分点,实现了图像特征快速和精准检测。

基于Kano-FAST的瓦楞纸激光印刷设备设计研究

目的推动印刷行业朝更高效的方向迈进,提高印刷设备的易操作性和视觉识别性。方法将Kano和FAST(Function Analysis System Technique)模型引入瓦楞纸激光打印设备设计的前期应用需求分析中,通过问卷的方法获取用户的基本要求,并划分为几个子类型,进而建立Kano的二维功能属性模型。采用FAST法建立功能树,辅助使用Kano模型,从而更精准地分析用户需求,并更好地根据其需求进行优化设计。结果综合运用设计原理,针对性地挖掘瓦楞纸激光印刷设备在造型识别性、操作易用性、生产安全性上存在的问题,进而输出更优解。结论该设计方法的引入有助于为同类型的印刷设备设计提供参考,并引起更多相关厂家的重视,推动印刷行业向更积极的方向发展。

A Fast Version of LASG/IAP Climate System Model and Its 1000-year Control Integration

A fast version of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）/Institute of Atmospheric Physics （IAP） climate system model is briefly documented. The fast coupled model employs a low resolution version of the atmospheric component Grid Atmospheric Model of IAP/LASG （GAMIL）, with the other parts of the model, namely an oceanic component LASG/IAP Climate Ocean Model （LICOM）, land component Common Land Model （CLM）, and sea ice component from National Center for Atmospheric Research Community Climate System Model （NCAR CCSM2）, as the same as in the standard version of LASG/IAP Flexible Global Ocean Atmosphere Land System model （FGOALS_g）. The parameterizations of physical and dynamical processes of the atmospheric component in the fast version are identical to the standard version, although some parameter values are different. However, by virtue of reduced horizontal resolution and increased time-step of the most time-consuming atmospheric component, it runs faster by a factor of 3 and can serve as a useful tool for longterm and large-ensemble integrations. A 1000-year control simulation of the present-day climate has been completed without flux adjustments. The final 600 years of this simulation has virtually no trends in global mean sea surface temperatures and is recommended for internal variability studies. Several aspects of the control simulation＇s mean climate and variability are evaluated against the observational or reanalysis data. The strengths and weaknesses of the control simulation are evaluated. The mean atmospheric circulation is well simulated, except in high latitudes. The Asian-Australian monsoonal meridional cell shows realistic features, however, an artificial rainfall center is located to the eastern periphery of the Tibetan Plateau persists throughout the year. The mean bias of SST resembles that of the standard version, appearing as a ＂double ITCZ＂ （Inter-Tropical Convergence Zone） associated with a westward extension of the equatorial eastern Pacific cold tongue. The sea ice extent is acceptable but has a higher concentration. The strength of Atlantic meridional overturning is 27.5 Sv. Evidence from the 600-year simulation suggests a modulation of internal variability on ENSO frequency, since both regular and irregular oscillations of ENSO are found during the different time periods of the long-term simulation.

Fast filtering algorithm based on vibration systems and neural information exchange and its application to micro motion robot

This paper develops a fast filtering algorithm based on vibration systems theory and neural information exchange approach. The characters, including the derivation process and parameter analysis, are discussed and the feasibility and the effectiveness are testified by the filtering performance compared with various filtering methods, such as the fast wavelet transform algorithm, the particle filtering method and our previously developed single degree of freedom vibration system filtering algorithm, according to simulation and practical approaches. Meanwhile, the comparisons indicate that a significant advantage of the proposed fast filtering algorithm is its extremely fast filtering speed with good filtering perfi^rmance. Further, the developed fast filtering algorithm is applied to the navigation and positioning system of the micro motion robot, which is a high real-time requirement for the signals preprocessing. Then, the preprocessing data is used to estimate the heading angle error and the attitude angle error of the micro motion robot. The estimation experiments illustrate the high practicality of the proposed fast filtering algorithm.

Adaptive changes of gastro-entero-pancreatic system endocrine cells in the black-spotted pond frog Rana nigromaculata after fasting

Changes in distribution density,morphology and secretory content of endocrine cells in the gastro-entero-pancreatic system of black-spotted frogs Rana nigromaculata before and after fasting were investigated using immunohistochemistry and antisera to six gut hormones.Six types of endocrine cells were detected in the digestive tract of Rana nigromaculata,including 5-hydroxytryptamine(5-HT),gastrin(GAS),somatostatin(SOM),glucagon(GLU),pancreatic polypeptide(PP)and vasoactive intestinal polypeptide(VIP)cells.After fasting,the density of 5-HT cells in the esophagus,cardia and fundus,GAS cells in the fundus and pylorus,PP cells in the fundus decreased significantly(P<0.01),while SOM cells in the cardia,GLU cells in the rectum increased significantly(P<0.01).The cytoplasmic processes of 5-HT cells became shorter or not detectable.The secretory content of GAS cells reduced in the cardia.The positive immunostaining reaction in the perinuclear region of SOM cells in the cardia,fundus and pylorus became weaker,while the staining intensity in the periphery of these cells became stronger.VIP cells were not detectable in the whole digestive tract after fasting.Five types of endocrine cells were found in the pancreas of Rana nigromaculata,including 5-HT,GAS,SOM,GLU and PP cells.After fasting,the density of 5-HT cells decreased slightly(P>0.05),while SOM,GAS,GLU and PP cells increased significantly(P<0.01).Furthermore,the secretory content of GLU cells increased significantly.Considering their functionalities,our results indicate that the changes of GEP endocrine cells in Rana nigromaculata responded adaptively to starvation-induced stress.

Delayed Hopf bifurcation in time-delayed slow-fast systems

This paper presents an investigation on the phenomenon of delayed bifurcation in time-delayed slow-fast differential systems.Here the two delayed's have different meanings.The delayed bifurcation means that the bifurcation does not happen immediately at the bifurcation point as the bifurcation parameter passes through some bifurcation point,but at some other point which is above the bifurcation point by an obvious distance.In a time-delayed system,the evolution of the system depends not only on the present state but also on past states.In this paper,the time-delayed slow-fast system is firstly simplified to a slow-fast system without time delay by means of the center manifold reduction,and then the so-called entry-exit function is defined to characterize the delayed bifurcation on the basis of Neishtadt's theory.It shows that delayed Hopf bifurcation exists in time-delayed slow-fast systems,and the theoretical prediction on the exit-point is in good agreement with the numerical calculation,as illustrated in the two illustrative examples.

Battlefield dynamic scanning and staring imaging system based on fast steering mirror

This paper presents the design of an experimental battlefield dynamic scanning and staring imaging system based on a fast steering mirror(FSM), which is capable of real-time monitoring of hot targets and wide-area reconnaissance of hot regions. First,the working principle and working sequence of the FSM are briefly analyzed. The mathematical model of the FSM system is built by modeling its dynamic and electrical properties, and the rationality of the model is validated by means of model identification. Second,the influence of external sources of disturbance such as the carrier and moment on the control precision of the FSM is effectively suppressed by the jointly controlling of proportional integral(PI)and disturbance observer(DOB), thus realizing a high precision and strong robustness control of the FSM system. Then, this paper designs an experimental prototype and introduces a special optical structure to enable the infrared camera to share the FSM with the visible light camera. Finally, the influence of the velocity difference between the mirror of the FSM and the rotating platform on the imaging quality of the system is experimentally analyzed by using the image sharpness evaluation method based on point sharpness. A good dynamic scanning and staring imaging result is achieved when the velocity of these two components correspond.

Compressed sensing based channel estimation for fast fading OFDM systems

A compressed sensing（CS） based channel estimation algorithm is proposed by using the delay-Doppler sparsity of the fast fading channel.A compressive basis expansion channel model with sparsity in both time and frequency domains is given.The pilots in accordance with a novel random pilot matrix in both time and frequency domains are sent to measure the delay-Doppler sparsity channel.The relatively nonzero channel coefficients are tracked by random pilots at a sampling rate significantly below the Nyquist rate.The sparsity channels are estimated from a very limited number of channel measurements by the basis pursuit algorithm.The proposed algorithm can effectively improve the channel estimation performance when the number of pilot symbols is reduced with improvement of throughput efficiency.

Development of a fast electron bremsstrahlung diagnostic system based on LYSO and silicon photomultipliers during lower hybrid current drive for tokamak

A novel real time fast electron bremsstrahlung (FEB) diagnostic system based on the lutetium yttrium oxyorthosilicate scintillators (LYSO) and silicon photomultipliers (SiPM) has been developed for tokamak.The diagnostic system is dedicated to study the FEB emission in the hard x-ray (HXR) energy range between 10 and 200 keV during the lower hybrid current drive.The system consists of a detection module and three data acquisition and processing (DAP)boards.The detection module consists of annulus LYSO-SiPM detector array and a 12-channel preamplifier module.The DAP boards upload the data to the host computer for displaying and storing through PXI bus.The time and space resolutions of the system are 10 ms and 4 cm,respectively.The experimental results can show the evolution over time and the spatial distribution of FEB.This paper presents the system performance and typical discharge results.

Nonlinear fast–slow dynamics of a coupled fractional order hydropower generation system

Internal effects of the dynamic behaviors and nonlinear characteristics of a coupled fractional order hydropower generation system(HGS) are analyzed. A mathematical model of hydro-turbine governing system(HTGS) with rigid water hammer and hydro-turbine generator unit(HTGU) with fractional order damping forces are proposed. Based on Lagrange equations, a coupled fractional order HGS is established. Considering the dynamic transfer coefficient eis variational during the operation, introduced e as a periodic excitation into the HGS. The internal relationship of the dynamic behaviors between HTGS and HTGU is analyzed under different parameter values and fractional order. The results show obvious fast–slow dynamic behaviors in the HGS, causing corresponding vibration of the system, and some remarkable evolution phenomena take place with the changing of the periodic excitation parameter values.

Development of wideband orthomode transducers for FAST cryogenic receiver system

This paper describes the design,construction,and performance of the wideband orthomode transducers(OMTs)for the L-(1.2–1.8 GHz),the S-(2–3 GHz)and the P-(0.56–1.12 GHz)band receiver systems of the Five-hundred-meter Aperture Spherical radio Telescope(FAST).These OMTs operate at the cryogenic temperature of 70 K to reduce their thermal noise contribution to the receiver chains.The development on the FAST L-and S-band quad-ridged waveguide(QRWG)OMTs is carried out based on the theoretical mode analysis.In view of the miniaturization of FAST cryogenic receiver system at P-band,a novel wideband compact bowtie dipole OMT is designed with an octave bandwidth as well as a length of only quarter wavelength.The proposed L-,S-and P-band OMTs are designed and optimized by using Ansys High Frequency Structure Simulator(HFSS),and then manufactured,tested at room temperature.Measurement of FAST cryogenic receiver system noise is also performed with the L-,S-and P-band OMTs installed.The measured results fully comply with the design specifications.

Synthesis and Characterization of Y^3＋, W^6＋-Doped Mineral Lithium Fast Ion Conductor Li1.2＋x-y YxTi1.9-xAl0.1Si0. 1Wy P2.9-yO12 System

New lithium fast ion conductors of Li1.2 ＋ x - y Yx Ti1.9 - x Al0.1Si0. 1Wy P2.9 - y O12 based on LiTi2（PO4）3 were prepared by high temperature solid state reaction using refined natural kaolinite as a starting material. X-ray powder diffraction analysis indicates that a phase with Nasieon-like structure exists together with other phases in the composition range of x =0.1, y≤0.2 and x =0.2,y ≤0.2. AC impedance measurements show that the initial composition with x = 0.10, y = 0.10 possesses the highest ionic conductivity of 1.65 × 10^-5 S·cm^-1 at room temperature, while the sample with initial composition of x =0.20, y =0.10 has the best ionic conductivity of 6. 53 × 10^-3S·cm^-1 at 573 K and decomposes at 3.0 V.

Tunable magnomechanically induced transparency and fast-slow light in a hybrid cavity magnomechanical system

We theoretically explore the tunability of magnomechanically induced transparency(MMIT) phenomenon and fastslow light effect in a hybrid cavity magnomechanical system in which a high-quality yttrium iron garnet(YIG) sphere and an atomic ensemble are placed inside a microwave cavity. In the probe output spectrum, we can observe magnoninduced transparency(MIT) and MMIT due to the photon-magnon and phonon-magnon couplings. We further investigate the effect of atomic ensemble on the absorption spectrum. The results show that better transparency can be obtained by choosing appropriate atomic ensemble parameters. We give an explicit explanation for the mechanism of the Fano resonance phenomenon. Moreover, we discuss phenomena of slow-light propagation. The maximum group delay increases significantly with the increasing atom–cavity coupling strength, and the conversion between slow light and fast light can also be achieved by adjusting the atom–cavity coupling strength. These results may have potential applications for quantum information processing and high precision measurements.

A motion planning algorithm for the feed support system of FAST

The paper relates to a motion planning algorithm for the feed support system of the Five-hundred-meter Aperture Spherical radio Telescope(FAST).To enhance the stability of the feed support system,the start/termination planning segments are adopted with an acceleration and deceleration section.The source switching planning adopts a combination of a line segment and focal segment to realize stable control of the feed support system.Besides,during the observation trajectory,a transition segment which is not used for observation data is planned with a required time.Through an example simulation,a smooth change is realized via the motion planning algorithm and presented in this paper.