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.

Monopoly Causes Inter-industry Wage Differentials

Inter-industry wage differentials in China, measured in terms of average employment earnings by industry, are significant and have been increasing since 1988. The coefficient of variables measuring inter-industry average earning differentials is apparently on the rise along with the subdivision of industry. A theoretical analysis of the labour market indicates that inter-industry wage differentials are mainly due to human capital variation among the employees of different industries and the likelihood of monopoly rent sharing. An empirical study finds that employee characteristics such as sex, age and education can only explain 60 percent of CVs in the period 2003 to 2005 and the rest may be due to the effect of monopoly rent sharing in certain industries. A residual analysis of wage equation proves that the monopoly industries of technology or knowledge share a small proportion of rents with employment, whereas non-competitive monopoly industries generally garner an abnormal share of rents, as much as half of their above-average earnings for their industries. Such abnormal rents and benefits are mainly the result of low cost natural resources, the use of state-owned assets, the misappropriation of consumer welfare and the seeking of fiscal or social subsidy for cost inflation. So, China should deal with the non-competitive monopoly industries by reforming their monopoly power and primary social distribution mechanism to structure a fair income distribution order.

Gender-Differentiated Language and Effective Inter-gender Communication

This paper discusses firstly the main differences between men's and women's speech in everyday communication among English native speakers,and then analyses the effects on inter-gender communication. It reduces English learners in China barriers when they communicate with English native speakers in different situations and gives domestic English teachers some enlightenment when they foster students' communication competence.

面齿轮轴间限滑差速器构型设计与性能分析

为解决现有轴间限滑差速器限滑能力有限、构型复杂且加工困难等问题,提出了一种新型的面齿轮轴间限滑差速器设计方案。对差速器构型原理和运动特性进行理论分析,建立了面齿轮轴间限滑差速器的力学平衡方程和锁紧系数理论模型;基于面齿轮加工成型原理和轴间差速器工作特性,设计搭建了三维实体模型和Adams虚拟样机模型,并利用Adams仿真软件进行了多体动力学分析。结果表明,面齿轮轴间限滑差速器对前后轴的锁紧系数分别可达到6.5和5;在良好路面行驶时,前后轴输出转矩与预设转矩分配比40∶60基本吻合;在双附着系数路面行驶时,可迅速锁紧打滑侧车轴并将转矩更多分配至未打滑侧车轴,实现转矩分配的自动调节,对前后轴的最大转矩分配分别可达73%和79%。结果验证了面齿轮轴间限滑差速器的可行性,为面齿轮轴间限滑差速器的设计应用提供了依据。

基于不同模糊度固定产品的PPP-AR定位性能评估

基于CODE、GFZ、CNES、武汉大学PRIDE实验室和内部估计的模糊度固定产品,从收敛时间、首次固定时间及定位精度等方面进行PPP-AR固定性能的研究。实验选用2022年40个IGS测站7 d的观测数据和各模糊度固定产品配套使用的精密产品,结果表明,在置信度为95%的静态解算模式下,5种产品在解算时间为1 h时固定解较浮点解定位精度提升最明显,分别提升46.58%(3.4 cm)、41.10%(3.0 cm)、45.21%(3.3 cm)、34.25%(2.5 cm)和41.10%(3.0 cm)。仿动态解算模式下,5种产品E、N方向的定位精度都能达到mm级,U方向较浮点解精度提升较小,其中使用GBM产品的精度提升最小,E、N、U方向分别提高72.73%(2.4 cm)、47.37%(0.9 cm)、5.41%(0.2 cm);提升效果较好的是WUM和COM产品,分别为81.82%(2.7 cm)、63.16%(1.2 cm)、24.32%(1.1 cm)和81.82%(2.7 cm)、63.16%(1.2 cm)、15.58%(0.8 cm)。

直流换流站高通HP3型交流滤波器电抗器匝间故障监测及保护

直流换流站高通HP3型交流滤波器组中电抗器匝间短路故障事故多发,由于缺乏对此故障的快速监测及保护,导致其匝间短路持续存在3~9 min之久并起火燃烧。匝间短路后电抗器的等值电感会不断减小,由此引起了滤波器电路参数变化并进而引发了滤波器配置的热过负荷保护启动告警,长久故障也引发了次生的电抗器底部支撑绝缘子闪络接地致使滤波器差动保护动作出口跳闸。文中分析了3起典型故障案例,结合C型高通HP3型滤波器电路设计理念及运行特点,解释了有关保护启动及动作的原因。基于匝间短路会导致HP3电路中电阻器上的工频电压、电流会随着匝间短路的不断发展而剧烈增大的特性,提出了一种基于工频电压差动原理的故障监测及保护方法。

顾及DISB的智能手机伪距差分定位算法

为了提高智能手机在遮挡环境下的定位精度和可靠性,给出一种全球定位系统(GPS)、伽利略卫星导航系统(Galileo)、北斗卫星导航系统(BDS)组合的系统间紧组合伪距差分定位模型和适用于智能手机的高度角附加不确定度的随机模型。首先评估了L1/B1I和L1/E1频率间的伪距差分系统间偏差的大小与稳定性,结果表明,智能手机伪距差分系统间偏差可以保持稳定性。利用小米8、华为P40智能手机和实测相同及不同类型接收机进行对比验证,通过设置截止高度角方式模拟遮挡环境。实验结果表明:在45°截止高度角模拟遮挡环境情况下,应用紧组合伪距差分改正模型,小米8和华为P40智能手机平面定位精度分别提高了25.5%和32.4%。该方法可以提高智能手机在遮挡环境下定位的精度和可靠性。

Performance analysis of the tight combination of GPS, BDS, GALILEO, and QzsS mixed frequencies signals

With the gradual development and modernization of satellite navigation systems,using observation information from multi-GNss has become one of the hot-spot issues in recent years.Multi-system loose combinations form double-difference observation equations within their respective systems,and the positioning effect is improved.However,the interchangeability and compatible interoperability between global navigation satellite systems(GNSS)cannot be truly realized.At the same time,when the number of visible satellites decreases abruptly,the positioning performance deteriorates sharply.This paper focuses on the GNsS multi-system tight combination relative positioning technique,gives a mathe-matical model of multi-system tight combination relative positioning considering differential inter-system bias(DISB),and analyzes the time-varying characteristics of DISB at overlapping and non-overlapping frequencies among GPS/Galileo,GPS/BDS,and GPS/QZSS in terms of receiver brand,tem-perature,and receiver restart.The GNsS tight combination relative positioning performance is verified by static data from Curtin University and dynamic data measured at Taiyuan University of Technology.The results show that compared with loose combination,the ambiguity-fixed rate increases from 62.18%to 97.60%for static data and from 74.97%to 99.53%for dynamic data when the elevation mask angle is 50°,resulting in a significant improvement in positioning performance.

不同栽培模式下人参根际土壤代谢物的差异研究

本研究旨在比较仿野生林下栽培人参(PSM)与农田栽培人参(NPSM)根际土壤代谢物的差异,以期为提升林下栽培人参的品质提供科学依据。通过采用气相色谱-串联质谱(GC-MS/MS)检测技术和分子生物学方法,分析了仿野生林下栽培人参和农田栽培人参根际土壤代谢物的差异。结果显示,仿野生林下栽培人参和农田栽培人参根际土壤代谢物具有差异,在检测到的68种差异代谢物中,有17种代谢物表现出显著差异,其中14种上调,3种下调。这些差异代谢物主要包括糖类、脂质类、有机酸类、酯类等物质。其中糖类占总显著差异代谢物的47%,是差异代谢物的主要部分;这些根际土壤差异代谢物直接或间接的影响了林下人参的品质。本研究不仅揭示了林下栽培人参和农田栽培人参根际土壤代谢物的差异,而且为提高林下栽培人参品质、探索克服林下人参栽培连作障碍的新途径以及提升林下人参药用价值和食用价值提供了科学参考。并为中国东北地区林下人参产业发展及乡村振兴战略的实施提供了新思路和方法。

基于边缘化高斯厄密特卡尔曼滤波的有偏量测下机动目标跟踪方法

针对传感器存在测量偏差情况下的机动目标跟踪问题,提出一种基于边缘化高斯厄密特卡尔曼滤波的有偏量测下机动目标跟踪方法。首先,通过相邻时刻的量测差分构建差分量测方程,从而消除测量偏差,将相邻时刻的目标状态扩维形成增广状态向量以匹配差分量测方程,实现实时滤波估计,同时对增广状态向量进行边缘化处理以降低高斯厄密特滤波的采样维度,减小滤波负担;然后,将交互式多模型方法融入边缘化高斯厄密特卡尔曼滤波以解决机动目标运动模型不确定的问题,在此基础上利用差分量测方程和增广状态向量推导出相应的滤波方程。实验结果表明,本方法能有效消除传感器测量偏差,目标跟踪精度远高于传统的交互式多模型高斯厄密特卡尔曼滤波方法。

论“学科交叉”与“交叉学科”

在现代意义上,学科应该是知识体系、活动体系和建制体系的统一。随着社会生产力水平不断提高,学科分化乃成为社会发展之历史必然。而今,深陷科学主义和工具理性泥潭的现代科学日益凸显出其固有的局限性,并严重制约着学科的进一步发展。于是,具有包容性和开放性特征的学科交叉便成为学科发展的必然选择。在认识和处理“学科交叉”和“交叉学科”关系时,切忌将路径、手段和方法等工具性因素“异化”为目的本身。在本质意义上,学科交叉只是一种工具性存在,而促进学科建设与发展、全面认识客观世界才是根本目的。交叉学科是学科交叉的产物之一,学科交叉比交叉学科更重要。

基于二维有偏距离插值的双层嵌入可逆信息隐藏算法

针对目前可逆信息隐藏技术存在载密图像嵌入率与失真度无法兼顾的问题,提出一种基于二维有偏距离插值的双层嵌入可逆信息隐藏方案。第一层嵌入将图像像素按棋盘式划分为两组,采用改进的全向梯度参数结合二维有偏距离插值算法,用其中一组像素预测另一组像素,再按照预测误差扩展方式嵌入秘密信息。第二层嵌入将剩余一组像素作为目标像素,再进行预测和嵌入,进一步提高嵌入率。本文从算法可逆性、预测精度、嵌入容量和载密图像失真度等多方面进行实验分析,结果表明,双层嵌入恢复后图像峰值信噪比为∞,不同种类隐藏图像像素和恢复图像像素均方误差均为0,表明算法可实现完全可逆隐藏;对不同种类载体图像进行测试,测试图像平均预测误差绝对值小于4的比例为79%,表明算法预测精度高;嵌入率对比实验表明,与其他算法相比,本算法均为最高,且双层嵌入较单层嵌入率平均提升30%以上,充分利用了像素冗余性;嵌入率为0.7 bit/pixel时,本算法载密图像和原始图像的峰值信噪比平均为39.854 dB,高于同类算法3~5 dB,表明载密图像失真度更低。本文还对阈值与嵌入率、结构相似性与嵌入率之间的关联进行分析和对比实验,深入探讨了高嵌入率的获得条件。本算法可较好解决载密图像嵌入率和嵌入失真不平衡的矛盾,综合性能更优。

北斗三号PPP-B2b差分码偏差对UPPP解算的影响

通过北斗三号精密单点定位服务信号(Precise Point Positioning B2b,PPP-B2b)差分码偏差(Differential Code Biases,DCB)对实时非组合精密单点定位(Uncombined Precise Point Positioning,UPPP)解算参数的影响进行研究。基于PPP-B2b服务的UPPP模型,分析了DCB对UPPP定位、收敛时间、对流层、钟差及斜向电离层解算的影响。在非组合模型下,采用北斗三号PPP-B2b实时精密单点定位(Real-Time Precise Point Positioning B2b,RTPPP-B2b)软件对接收机实测数据进行实验分析。实验结果表明:载波与伪距观测值权比为103∶1时,DCB对定位精度和收敛时间影响均较小,载波与伪距观测值权比为102∶1时,无DCB校正的UPPP定位误差收敛时间会变长;DCB对解算对流层天顶总延迟的影响可以忽略,对接收机钟差影响在亚纳秒级别;在使用UPPP提取斜向电离层过程中,DCB主要影响斜向电离层的计算精度。

Evaluation of negative bias temperature instability in ultra-thin gate oxide pMOSFETs using a new on-line PDO method

A new on-line methodology is used to characterize the negative bias temperature instability （NBTI） without inherent recovery. Saturation drain voltage shift and mobility shift are extracted by ID-VD characterizations, which were measured before stress, and after every certain stress phase, using the proportional differential operator （PDO） method. The new on-line methodology avoids the mobility linearity assumption as compared with the previous onthe-fly method. It is found that both reaction-diffusion and charge-injection processes are important in NBTI effect under either DC or AC stress. A similar activation energy, 0.15 eV, occurred in both DC and AC NBTI processes. Also degradation rate factor is independent of temperature below 90℃ and sharply increases above it. The frequency dependence of NBTI degradation shows that NBTI degradation is independent of frequencies. The carrier tunnelling and reaction-diffusion mechanisms exist simultaneously in NBTI degradation of sub-micron pMOSFETs, and the carrier tunnelling dominates the earlier NBTI stage and the reaction-diffusion mechanism follows when the generation rate of traps caused by carrier tunnelling reaches its maximum.

CHEMICAL“CARCINOGENS”,AS MODULATORS OF INTER-CELLULAR COMMUNICATION,ARE MITOGENS,NOT MUTAGENS.

Although mutations clearly play a role in themulti-stage process of carcinogenesis,a challengewll be made to the paradigm that most chemical"carcinogens" act via mutagenic activity("carcinogens as mutagens").Control ofproliferation and differentiation within andbetween tissues is mediated by

基于微分域电流过零点偏移特征的电抗器匝间保护新方法

以中性点不带小电抗的高压并联电抗器为研究对象,在分析电抗器空投励磁涌流特征的基础上,指出了并联电抗器不带中性点小电抗时涌流会更加严重,是引起匝间保护误动的主要原因。分析了并联电抗器空投饱和的机理,指出了电抗器绕组磁通饱和后微分域相电流过零点前后采样峰值间距会发生偏移,在此基础上提出一种基于微分域电流过零点偏移特征的电抗器匝间保护新方法。利用工频特征下相电流过零点前后峰值间距与微分域相电流过零点前后采样峰值间距的偏移程度,结合相电流线性区内各时刻电感的均方根值与额定电感之间的特征关系来识别电抗器空投饱和与匝间故障,若识别为电抗器空投饱和则闭锁匝间保护,若识别为匝间故障则经短延时开放匝间保护。仿真结果验证了所提方法的正确性和有效性。

永磁同步电机匝间短路故障短路线圈定位方法

为了研究基于电机外部电信号的直驱永磁同步电机早期匝间短路故障检测及定位方法,提出一种基于探测线圈阵列的DDPMSM的ISF短路线圈定位方法。首先,提出一种基于电机绕组分布及连接方式的探测线圈阵列;其次,分析了探测线圈工作机理,建立了考虑短路线圈位置的探测线圈反电势矩阵;然后,利用所建立的探测线圈反电势矩阵,分析用于ISF短路线圈位置的故障特征量。提出了利用探测线圈反电势差值进行ISF故障检测和故障线圈组的定位,利用探测线圈反电势残差进行短路线圈的定位,提出基于上述定位特征量的ISF定位方法。仿真和实验结果验证了所提出方法的正确性和有效性。最后,以样机为例,将所提出的定位方法与现有故障定位方法进行比较,进一步证明方法的准确性和灵敏性。

妊娠期糖尿病中医体质辨证及血清糖脂RBP4水平的关系研究

目的:探究妊娠期糖尿病(GDM)产妇中医体质辨证及血清糖脂视黄醇结合蛋白4(RBP4)水平的关系。方法:选取2019年6月-2021年6月期间于我院就诊的142例GDM患者作为研究对象,对所有患者进行中医体质辨证分型,根据体质分型结果将其分为偏颇体质组和平和体质组。比较两组基线资料、糖代谢指标[空腹血糖(FPG)、餐后两小时血糖(2hPG)、糖化血红蛋白(HbAlc)]、血清RBP4、脂代谢指标[总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)]水平,分析GDM患者体质偏颇的影响因素及与糖脂代谢、血清RBP4的关系。结果:所有患者经中医体质辨证分型后,发现体质偏颇患者115例(80.99%),体质平和患者27例(19.01%);偏颇体质组和平和体质组年龄、确诊孕周、收缩压、舒张压等资料无显著差异(P>0.05),偏颇体质组体质指数(BMI)、腰臀比显著大于平和体质组(P<0.05);偏颇体质组FPG、2hPG、HbAlc、RBP4、TC、TG、LDL-C水平均显著高于平和体质组(P<0.05),两组HDL-C水平比较无显著差异(P>0.05);Logistic回归分析得出,GDM患者体质偏颇与BMI、FPG、2hPG、HbAlc、RBP4、TC、TG、LDL-C水平相关(P<0.05)。结论:中医体质辩证属偏颇体质的GDM患者糖脂代谢紊乱较平和体质患者更严重,临床需引起充分重视,并通过相关血清指标进行评估,及时对偏颇体质患者予以治疗。

Relative position determination of a lunar rover using the biased differential phase delay of same-beam VLBI

When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The relative position between a lunar rover and a lander can be determined with an error of several hundreds of meters. When the guidance information of the rover is used to determine relative position, the rover's wheel skid behavior and integral movement may influence the accuracy of the determined position. This paper proposes a new method for accurately determining relative position. The differential group delay and biased differential phase delay are obtained from the same-beam VLBI observation, while the modified biased differential phase delay is obtained using the statistic mean value of the differential group delay and the biased phase delay as basis. The small bias in the modified biased phase delay is estimated together with other parameters when the relative position of the rover is calculated. The effectiveness of the proposed method is confirmed using the same-beam VLBI observation data of SELENE. The radio sources onboard the rover and the lander are designed for same-beam VLBI observations. The results of the simulations of the differential delay of the same-beam VLBI observation between the rover and the lander show that the differential delay is sensitive to relative position. An approach to solving the relative position and a strategy for tracking are also introduced. When the lunar topography data near the rover are used and the observations are scheduled properly, the determined relative position of the rover may be nearly as accurate as that solved using differential phase delay data.

基于励磁绕组差模电流基频分量的新型磁阀式并联电抗器匝间保护方案

作为一种新型无功补偿装置,磁阀式可控电抗器(magnetic valve controllable reactor,MVCR)能够实现无功功率的大范围平滑调节,进而有效解决无功失衡导致的电压波动问题。该文针对一种新型MVCR开展研究,首先介绍了该种新型MVCR的拓扑结构,分析了其正常运行时励磁绕组的电气特性,在此基础上针对新型MVCR励磁绕组和工作绕组发生匝间故障时的故障特性开展研究,其中引入了励磁绕组差模电流的概念来表征匝间故障特征。当匝间故障发生后,新型MVCR励磁绕组差模电流中将产生较大的基频分量。基于该故障特性,提出了一种基于励磁绕组差模电流基频分量的匝间保护方案,并进一步分析了该保护方案在预励磁合闸暂态过程中的适应性。最后,通过Matlab/Simulink仿真实验,验证了该文所提新型MVCR匝间保护方案的可行性及有效性。