Long-term and short-term stability characteristics of receiver inter system bias for BDS3/BDS2

The study of inter-system bias(ISB)is important for multi-system fusion and the performance of different signal compatibility.In this paper,the stability of ISB at the BDS3/BDS2 receiver end is calculated and analyzed for different time spans(DOY 060~090 in 2021)from a total of 31 MGEX and iGMAS stations.We adopted two estimation strategies,random walk and constant approach,using the precision products of orbit and clock bias provided by WUM,the influence of which on ISB was also analyzed.Our results showed that the ISB value varied little within a day,and the mean of daily ISB standard deviation was only 0.037 m when the observation condition was good.The signal reception was continuous,indicating a high ISB stability for one day.If extending the time series to one month,however,the ISB standard deviation calculated by constant approach,in which a constant ISB is estimated on a daily basis was about 0.1 m,and the results of adjacent days were not continuous,with no apparent pattern.Concerning the random walk approach,the obtained ISB time series also had a jump,and the conclusion was the same as that of the constant strategy.Besides,receiver types showed a strong regularity in ISB numerical situation,and the distribution of ISB values corresponding to the same receiver type was relatively close.Therefore,we conclude that the ISB parameters remain stable in the short term(one day)and less stable in the long-term period.It is recommended that the ISB term should be set as a constant estimate every day in BDS3/BDS2 solutions,regardless of receiver type consistency.

Slope stability prediction based on a long short-term memory neural network:comparisons with convolutional neural networks,support vector machines and random forest models

The numerical simulation and slope stability prediction are the focus of slope disaster research.Recently,machine learning models are commonly used in the slope stability prediction.However,these machine learning models have some problems,such as poor nonlinear performance,local optimum and incomplete factors feature extraction.These issues can affect the accuracy of slope stability prediction.Therefore,a deep learning algorithm called Long short-term memory(LSTM)has been innovatively proposed to predict slope stability.Taking the Ganzhou City in China as the study area,the landslide inventory and their characteristics of geotechnical parameters,slope height and slope angle are analyzed.Based on these characteristics,typical soil slopes are constructed using the Geo-Studio software.Five control factors affecting slope stability,including slope height,slope angle,internal friction angle,cohesion and volumetric weight,are selected to form different slope and construct model input variables.Then,the limit equilibrium method is used to calculate the stability coefficients of these typical soil slopes under different control factors.Each slope stability coefficient and its corresponding control factors is a slope sample.As a result,a total of 2160 training samples and 450 testing samples are constructed.These sample sets are imported into LSTM for modelling and compared with the support vector machine(SVM),random forest(RF)and convo-lutional neural network(CNN).The results show that the LSTM overcomes the problem that the commonly used machine learning models have difficulty extracting global features.Furthermore,LSTM has a better prediction performance for slope stability compared to SVM,RF and CNN models.

Double Layer Composite Electrode Strategy for Efficient Perovskite Solar Cells with Excellent Reverse-Bias Stability

Perovskite solar cells(PSCs)have become the represent-atives of next generation of photovoltaics;nevertheless,their stability is insufficient for large scale deployment,particularly the reverse bias stability.Here,we propose a transparent conducting oxide(TCO)and low-cost metal composite electrode to improve the stability of PSCs without sacrificing the efficiency.The TCO can block ion migrations and chemical reactions between the metal and perovskite,while the metal greatly enhances the conductivity of the composite electrode.As a result,composite electrode-PSCs achieved a power conversion efficiency(PCE)of 23.7%(certified 23.2%)and exhibited excellent stability,maintaining 95%of the initial PCE when applying a reverse bias of 4.0 V for 60 s and over 92%of the initial PCE after 1000 h continuous light soaking.This composite electrode strategy can be extended to different combinations of TCOs and metals.It opens a new avenue for improving the stability of PSCs.

The Effect of Oxygen Partial Pressure during Active Layer Deposition on Bias Stability of a-InGaZnO TFTs

The effect of oxygen partial pressure （Po2） during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide （a-IGZO） thin film transistors （TFTs） is investigated. As Po2 increases from 10% to 30%, it is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on the x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies （Or） within the a-IGZO layer is suppressed by increasing Po2. Meanwhile, the low-frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops with increasing Po2. Therefore, the improved interface quality with increasing Po2 during the channel layer deposition can be attributed to the reduction of interface Ov-related defects, which agrees with the enhanced bias stress stability of the a-IGZO TFTs.

Improvement of the short-term stability of atomic fountain clock with state preparation by two-laser optical pumping

To improve the signal to noise ratio(SNR)and the short-term stability of cesium atomic fountain clocks,the work of two-laser optical pumping is presented theoretically and experimentally.The short-term stability of the NIM6 fountain clock has been improved by preparing more cold atoms in the|F=4,m_(F)=0>clock state with a shortened cycle time.Two π-polarized laser beams overlapped in the horizontal plane have been applied after launching,one is resonant with|F=4>→|F′=4>transition and the other is resonant with|F=3>→|F′=4>transition.With optical pumping,the population accumulated in the|m_(F)=0>clock state is improved from 11%to 63%,and the detection signal is increased by a factor of 4.2,the SNR of the clock transition probability and the short-term stability are also improved accordingly.

Convolution Neural Network-based Load Model Parameter Selection Considering Short-term Voltage Stability

The recently proposed ambient signal-based load modeling approach offers an important and effective idea to study the time-varying and distributed characteristics of power loads.Meanwhile,it also brings new problems.Since the load model parameters of power loads can be obtained in real-time for each load bus,the numerous identified parameters make parameter application difficult.In order to obtain the parameters suitable for off-line applications,load model parameter selection(LMPS)is first introduced in this paper.Meanwhile,the convolution neural network(CNN)is adopted to achieve the selection purpose from the perspective of short-term voltage stability.To begin with,the field phasor measurement unit(PMU)data from China Southern Power Grid are obtained for load model parameter identification,and the identification results of different substations during different times indicate the necessity of LMPS.Meanwhile,the simulation case of Guangdong Power Grid shows the process of LMPS,and the results from the CNNbased LMPS confirm its effectiveness.

Long-term Stability and Oceanic Mean State Simulated by the Coupled Model FGOALS-s2

We describe the long-term stability and mean climatology of oceanic circulations simulated by version 2 of the Flexible Global Ocean-Atmosphere-Land System model （FGOALS-s2）. Driven by pre-industrial forcing, the integration of FGOALS-s2 was found to have remained stable, with no obvious climate drift over 600 model years. The linear trends of sea SST and sea surface salinity （SSS） were -0.04℃ （100 yr）-1 and 0.01 psu （100 yr）-1, respectively. The simulations of oceanic temperatures, wind-driven circulation and thermohaline circulation in FGOALS-s2 were found to be comparable with observations, and have been substantially improved over previous FGOALS-s versions （1.0 and 1.1）. However, significant SST biases （exceeding 3℃） were found around strong western boundary currents, in the East China Sea, the Sea of Japan and the Barents Sea. Along the eastern coasts in the Pacific and Atlantic Ocean, a warm bias （〉3℃） was mainly due to overestimation of net surface shortwave radiation and weak oceanic upwelling. The difference of SST biases in the North Atlantic and Pacific was partly due to the errors of meridional heat transport. For SSS, biases exceeding 1.5 psu were located in the Arctic Ocean and around the Gulf Stream. In the tropics, freshwater biases dominated and were mainly caused by the excess of precipitation. Regarding the vertical dimension, the maximal biases of temperature and salinity were located north of 65°N at depths of greater than 600 m, and their values exceeded 4℃ and 2 psu, respectively.

The Challenge of Standard Stability in LC-MS Based Multi-Analyte Approaches for Veterinary Drugs

The short-and long-term stability of multi-component mixtures and intermediate mixtures of analytical standards of veterinary drugs,which can potentially occur in food and feed chains,was examined by an isochronous measurement approach.Short-term stability testing of calibrants included storage for 1,2,4,and 7 days at-20℃(as a baseline)4℃,and 23℃(with and without exposure to sunlight),respectively.Long-term stability testing conditions of intermediate mixes were-20℃,4℃,23℃(with and without exposure to sunlight),and control temperature at-80℃while the testing period was 2,4,8,and 12 weeks,respectively.Results indicated that calibration standards should ideally be stored at 4℃for only 1~2 days,without the presence of acid.Neutral storage conditions were acceptable even at room temperature.Storage of intermediate mixtures containingß-lactams and cephalosporins for longer than 1 month under 4℃ and room temperature resulted in a loss of almost 90%.When it comes to the intermediate mixtures with penicillin V and G,acceptable storage conditions were 2 weeks at-20℃,without the presence of acid.Other classes of veterinary drugs were less critical as considers long-term stability.Overall,storage conditions at-20℃were considered optimal for long-term storage of intermediate mixes of veterinary drug standards.

Synthesis and characterization of a 1,3-dibutylimidazolium azide([BBIm][N_(3)]) : A promising green energetic ionic liquid

In the pursuit of advancing imidazolium-based energetic ionic liquids (EILs),the current study is devoted to the synthesis and characterization of 1,3-dibutyl-imidazolium azide ([BBIm][N_(3)]),as a novel member in this ionic liquids class.The chemical structure of this EIL was rigorously characterized and confirmed using FTIR spectroscopy,1D,and 2D-NMR analyses.The thermal behavior assessment was conducted through DSC and TGA experiments.DSC analysis revealed an endothermic glass transition at T_(g)=-61℃,followed by an exothermic degradation event at T_(onset)=311℃.Similarly,TGA thermograms exhibited a one-stage decomposition process resulting in 100% mass loss of the sample.Furthermore,the short-term thermal stability of the azide EIL was investigated by combining the non-isothermal TGA data with the TAS,it-KAS,and VYA/CE isoconversional kinetic approaches.Consequently,the Arrhenius parameters(E_(a)=154 kJ·mol^(-1),Log(A/s^(-1))=11.8) and the most probable reaction model g(a) were determined.The observed high decomposition temperatures and the significantly elevated activation energy affirm the enhanced thermal stability of the modified EIL.These findings revealed that[BBIm][N_(3)]EIL can be a promising candidate for advanced energetic material application.

Comparison of Velocity Shear with Turbulence Reduction Driven by Biasing in a Simple Cylindrical Slab Plasma

In an experimental realization of the sheared cylindrical slab, the level of plasma turbulence is strongly reduced by application of a sufficient bias potential difference in the radial direction. Density fluctuation levels △nrms/n decrease by more than a factor of five. The ion flow velocity profile is measured spectroscopically from the Doppler shift of an argon ion line. Comparison of the shearing rates with the turbulent amplitudes as a function of bias show no relation between the shearing rate and turbulence reduction, contrary to expectations.

Dealing with Multicollinearity in Factor Analysis: The Problem, Detections, and Solutions

Multicollinearity in factor analysis has negative effects, including unreliable factor structure, inconsistent loadings, inflated standard errors, reduced discriminant validity, and difficulties in interpreting factors. It also leads to reduced stability, hindered factor replication, misinterpretation of factor importance, increased parameter estimation instability, reduced power to detect the true factor structure, compromised model fit indices, and biased factor loadings. Multicollinearity introduces uncertainty, complexity, and limited generalizability, hampering factor analysis. To address multicollinearity, researchers can examine the correlation matrix to identify variables with high correlation coefficients. The Variance Inflation Factor (VIF) measures the inflation of regression coefficients due to multicollinearity. Tolerance, the reciprocal of VIF, indicates the proportion of variance in a predictor variable not shared with others. Eigenvalues help assess multicollinearity, with values greater than 1 suggesting the retention of factors. Principal Component Analysis (PCA) reduces dimensionality and identifies highly correlated variables. Other diagnostic measures include the condition number and Cook’s distance. Researchers can center or standardize data, perform variable filtering, use PCA instead of factor analysis, employ factor scores, merge correlated variables, or apply clustering techniques for the solution of the multicollinearity problem. Further research is needed to explore different types of multicollinearity, assess method effectiveness, and investigate the relationship with other factor analysis issues.

变压器直流偏磁瞬态场路耦合计算的稳定性分析

变压器瞬态场路耦合计算存在稳定性、计算效率及精确度的问题。利用瞬态场路耦合方法,结合能量扰动原理计算磁场变化对应的动态电感。根据四阶龙格库塔法求解的高阶收敛性,推导绝对稳定域以判断计算是否收敛,分析时间步长与状态矩阵特征值的关系,定义电感变化函数评价磁场计算精确度。对单相变压器建模和仿真,计算正常运行和直流偏磁时的瞬态磁场和等效电路参数,研究耦合参数在不同励磁饱和程度时的变化规律,结果说明利用动态电感参数可以反映时变的励磁饱和情况。与传统欧拉法和改进欧拉法对比,四阶龙格库塔法具有更高的稳定性和精确性,同时验证了绝对稳定域的正确性。以稳定性为前提,合理选取磁场求解频率可以有效提高计算效率和精确度。通过实验验证了瞬态场路耦合计算的可行性和稳定性分析的可靠性,为实际变压器瞬态场路计算提供新的思路。

Quadrature error and offset error suppression circuitry for silicon micro-gyroscope

The reasons for inducing quadrature error and offset error are analyzed and the expressions of quadrature error and offset error are induced. The open-loop system analysis indicates that, in order to avoid the appearance of harmonic peaks, the frequency difference δf between drive mode and sense mode must be less than 1/（2Qy）. In order to eliminate the effects of the quadrature error and the offset error, as well as the inherent non- linearity in the capacitance-type sensors, a closed-loop feedback control circuit with quadrature correction is designed. The experimental results indicate that the quadrature error and offset error are corrected. By comparing with open-loop detection, the closed-loop feedback control circuit with quadrature correction decreases the non-linearity of the scale factor from 16. 02% to 0. 35 %, widens the maximum rate capability from ± 270 （°）/s to ± 370 （°）/s and increases the stability of zero bias from 155. 2 （°）/h to 60. 6 （°）/h.

永磁饱和型故障限流器的永磁体稳定性实验研究

为获得用于永磁饱和型故障限流器(permanent-magnet-biased saturation based fault current limiter,PM-FCL)的钕铁硼(Nd-Fe-B)N35永磁体的运行稳定性能,从时间、温度和外磁场影响3方面展开了实验研究。以永磁体随时间的退磁率来表征时间稳定性,以可逆损失率和可逆温度系数来表征温度稳定性,并分析了永磁部件的面积厚度比S/L对温度稳定性的影响。进一步,用通电螺线管模拟220kV变电站的工程磁场环境,通过实验考查了PMFCL永磁体的外磁场稳定性。实验表明,钕铁硼永磁体具有较好的时间稳定性和外磁场稳定性,在温度较高时的退磁效应并不明显,并可通过设计面积厚度比S/L较低的限流拓扑予以抵消。所得研究结果为研制面向工程应用的高压大容量PMFCL提供了基础依据。

永磁饱和型故障限流器的高压大容量化分析

为提高永磁体的偏置能力以利永磁饱和型故障限流器朝高压大容量发展,从温度和外磁场两方面分析了钕铁硼永磁体的稳定性问题,论证了其应用到该限流器的可行性;提出"饱和深度比"的定义,指出改善永磁体的偏置能力与提高铁心的饱和深度比等价;基于一种结构参数可调的永磁饱和型故障限流器拓扑,分析了限流器结构参数与铁心饱和深度比的数量关系,并通过有限元法仿真以及实验加以验证;最后给出了10kV等级永磁饱和型故障限流器的一个设计实例。仿真与实验结果均表明,增加永磁体的厚度与截面积可获得较优的偏置能力,实现永磁饱和型故障限流器的高压大容量化在技术上是可行的。

桥式混合励磁型饱和铁心故障限流器性能分析

为降低饱和铁心故障限流器(saturated core fault current limiter,SCFCL)运行中的励磁损耗,应用稀土永磁体对铁心进行励磁已得到广泛研究。但永磁体在高压大容量领域中的励磁能力尚不足,且稳定性易受影响,限制了其推广应用。为解决上述不足,提出了一种桥式混合励磁型饱和铁心故障限流器(bridge-type hybrid-biased SCFCL,BHFCL)。BHFCL利用混合励磁结构增强励磁能力,并通过对磁路磁阻进行设计,可有效降低通过永磁体的反向交流磁通,提高永磁体稳定性。通过电磁耦合的方法,对BHFCL基本原理以及工作特性进行分析,研究了结构参数对其性能的影响。基于Maxwell的有限元电磁仿真结果以及220 V/10 A限流器样机实验结果,均验证了文中所提BHFCL的有效性与理论分析的正确性。

爆破振动下偏压隧道洞口段边坡稳定性分析

通过有限元软件建立三维双侧壁偏压隧道洞口段边坡数值模型,提出3种爆破工况;分析3种爆破工况下边坡的振速响应规律,通过边坡的位移分析坡体的变形特性,依据最小二乘法对监测数据进行回归分析得出爆破振动衰减公式,制定每个工况单段最大起爆药量安全阈值。由解析法求出不同工况在静、动态下坡体的稳定性变化规律。研究结果表明:随着爆心距的增大,坡面振速衰减呈现出近快、远慢的传播规律;工况1相比其他工况对边坡整体及坡脚的稳定性影响最大;通过对坡体测点各向振速监测数据进行回归分析,得出在安全控制标准内工况1-工况3的单段最大起爆药量分别控制在3.4,3.4及3.5kg之内效果最好;由解析法得出,静力状态下开挖隧道时边坡均处于稳定状态。左、中导坑在爆破开挖时边坡安全系数分别为1.13和1.18均小于1.20,极有可能诱发局部坡体滑移失稳。

A novel closed-loop vacuum silicon microgyroscope

A novel closed-loop control strategy of a silicon microgyroscope （SMG） is proposed. The SMG is sealed in metal can package in drive and sense modes and works under the air pressure of 10 Pa. Its quality factor reaches greater than l0 000. Self-oscillating and closed-loop methods based on electrostatic force feedback are adopted in both measure and control circuits. Both single side driving and sensing methods are used to simplify the drive circuit. These dual channel decomposition and reconstruction closed loops are applied in sense modes. The testing results demonstrate that useful signals and guadrature signals do not interact with each other because of the decoupling of their phases. Under the condition of a scale factor of 9. 6 mV/（（°） .s）, in a full measurement range of±300 （°）/s, the zero bias stability reaches 28 （°）/h with a nonlinear coefficient of 400 × 10^-6 and a simulated bandwidth of more than 100 Hz. The overall performance is improved by two orders of magnitude in comparison to that at atmospheric pressure.

偏压隧道不均匀来压下钢拱架应力变化的机理分析

钢拱架常作偏压隧道的支护结构,其应力变化对隧道的稳定性影响较大。以某铁路隧道偏压段为研究对象,利用SAP2000对该隧道进行建模,通过在模型中选取关键位置,施加与现场实测相近的应力,分析了不同来压对钢拱架应力变化的影响。分析结果为:在初期支护中,钢拱架应力的变化能通过围岩压力有效地反映,围岩压力越大,钢拱架应力变化越大。研究结果可为隧道支护结构的稳定性分析和施工提供一定的借鉴。

基于超细径光纤的高精度光纤陀螺

在应用系统的牵引及光学器件技术的推动下,工程化光纤陀螺朝着小型化、轻量化、高精度方向发展,设计了一种基于新型超细径(60/100)光纤制作的高精度光纤陀螺。相比于传统细径保偏光纤,新型超细径光纤可增加光纤的抗弯曲程度,也可使光纤环圈的绕制半径减少;同时,由于光纤变细,光纤环厚度减小,当环境温度改变时,内外层光纤温度差减小,有利于改善光纤陀螺环圈全温性能,提高光纤陀螺温度特性。首先研究了新型超细径光纤纤芯、包层结构设计,在此基础上为针对性提高涂覆胶体、绕环胶体材料的可靠性,建立了胶体材料性能随时间退化的模型;随后,基于上述新型光纤和小型化宽谱ASE光源,成功搭建了高精度光纤陀螺仪样机,陀螺整机尺寸为70 mm×70 mm×35 mm,陀螺测试零偏稳定性可达0.007°/h,可以满足陀螺小型化、轻量化、高精度需求。