Free-walking:Pedestrian inertial navigation based on dual foot-mounted IMU

The inertial navigation system(INS),which is frequently used in emergency rescue operations and other situations,has the benefits of not relying on infrastructure,high positioning frequency,and strong real-time performance.However,the intricate and unpredictable pedestrian motion patterns lead the INS localization error to significantly diverge with time.This paper aims to enhance the accuracy of zero-velocity interval(ZVI)detection and reduce the heading and altitude drift of foot-mounted INS via deep learning and equation constraint of dual feet.Aiming at the observational noise problem of low-cost inertial sensors,we utilize a denoising autoencoder to automatically eliminate the inherent noise.Aiming at the problem that inaccurate detection of the ZVI detection results in obvious displacement error,we propose a sample-level ZVI detection algorithm based on the U-Net neural network,which effectively solves the problem of mislabeling caused by sliding windows.Aiming at the problem that Zero-Velocity Update(ZUPT)cannot suppress heading and altitude error,we propose a bipedal INS method based on the equation constraint and ellipsoid constraint,which uses foot-to-foot distance as a new observation to correct heading and altitude error.We conduct extensive and well-designed experiments to evaluate the performance of the proposed method.The experimental results indicate that the position error of our proposed method did not exceed 0.83% of the total traveled distance.

Modeling and Mapping Sand Encroachment Risk as an Aid for Urban Planning in the United Arab Emirates (UAE)

Sand encroachment into urban areas represents a high risk factor for transportation infrastructural and urban development in the United Arab Emirates. The UAE is located in one of the world’s largest arid regions with a strong prevalence of sand movement and encroachment into urban areas, particularly in the last few years. The objective of this research is to develop a land surface process platform that models sand movements and further generates an encroachment risk index map of potential encroachment risk areas season-wise in the UAE. To achieve this objective, this research used elevation and land cover maps generated from Lands at 8 Operational Land Imager (OLI) data which represent the topography of the study area coupled with meteorological information on wind speed, temperature and precipitation. Furthermore, the study considered the vegetation cover as a major contribution factor to reduce sand encroachment. Using developed sand movement model for this research, sand encroachment risk maps were generated to help urban planners in cities making informed decisions of future urban protection structures and transportation networks that mitigate the effects of sand dunes encroachments in the UAE. A major finding of this research results conclude that during the summer season encroachment risk reaches 30% higher compared to the winter season due to the extremely high temperature which leads to reduced vegetation in the country. Urban planning decision maker may consider the finding of this research for future infrastructural adjustments.

Do aeolian deposits and sand encroachment intensity shape patterns of vegetation diversity and plant functional traits in desert pavements?

The effects of sand encroachment on composition,diversity,and functional patterns of vegetation in drylands are rarely studied,and yet addressing these aspects is important to deepen our understanding of the biodiversity conservation.This study aimed to investigate the effect of sand encroachment on plant functional biodiversity of desert pavements(gravel deserts)in the Sahara Desert of Algeria.Plants were sampled and analyzed in three desert pavements with different levels of sand encroachment(LSE)and quantity of aeolian deposits(low,LLSE;medium,MLSE;and high,HLSE).Within the sample-plot area(100 m^(2)),density of every plant species was identified and total vegetation cover was determined.Plant taxonomic and functional diversity were analyzed and compared between LSE.Result showed that 19 plant species in desert pavements were classified into 18 genera and 13 families.Asteraceae and Poaceae were the most important families.The species Anabasis articulata(Forssk)Moq.characterized LLSE desert pavements with 11 species,whereas Thymelaea microphylla Coss.&Durieu ex Meisn.and Calobota saharae(C&D)Boatwr.&van Wyk were dominant species of desert pavements with MLSE(14 species)and HLSE(10 species),respectively.The highest values of species richness and biodiversity were recorded in desert pavements with MLSE,while low values of these ecological parameters were obtained in desert pavements with HLSE.Desert pavements with LLSE were characterized with the highest values of species abundances.Plant communities were dominated by chamaephytes,anemochorous,arido-active,and competitive stress-tolerant plants.The increase in LSE along the gradient from LLSE to HLSE induced significant changes in plant community variables including decreases in plant density,plant rarity,lifeform composition,morphological type,and aridity adaptation.Desert pavements with HLSE favor the degradation of vegetation and trigger biodiversity erosion.

Tree encroachment into savannas alters soil microbiological and chemical properties facilitating forest expansion

Abstract Forests have been expanding over typical savanna sites for the past 3000 years in the Neotropics. Such invasion can produce a series of environmental modifications on typical savanna; however, it remains unclear how modifications in soil properties, caused by the encroachment of woody species, facilitate the expansion of forest ecosystems under dystrophic conditions. Here we examined chemical and microbiological changes associ- ated with tree encroachment in oxisols of a Neotropical Savanna at Assis Ecological Station, Southeastern Brazil. We predicted that tree encroachment caused by typical forest species would cause significant changes in the chemical and microbiological properties of savanna soils. Soils were sampled at Assis Ecological Station, from savanna sites differing in tree encroachment （typical, dense and forested savanna） caused by decades of fire exclusion. We analysed vegetation leaf area index and leaf litter volume deposited in the studied plots and chemical （pH,organic matter, P, K, Ca, Mg, A1, NO3-, NH4＋） and microbiological （microbial C biomass and dehydrogenase activity） properties of soils under distinct encroachment conditions. Most soil chemical properties did not change along the tree encroachment gradient; however, total P, soil organic matter, soil microbial C and dehydrogenase activity increased from typical savanna to forested savanna. The changes in soil organic matter and dehydrogenase activity were correlated with the values of leaf area index and litter volume along the encroachment gradient. Our results demonstrate that forest species can increase carbon and phosphorus supplies in tropical savanna soils.

Encroachment of the Buriganga River in Bangladesh

A survey on different aspects of Buriganga River encroachment was conducted in a 300 meter long encroached part of the river located in Dhaka, Bangladesh. A total of 100 respondents were surveyed and three Focus Group Discussions (FGDs) were arranged prior to the semi-structured questionnaire survey. It was observed that almost all of the respondents migrated to the study area. The majority of the respondents had better business opportunity (69.23%) as the cause of encroachment. Significant portions of the respondents occupying the encroached area were found to be landless (36.84%), small businessmen (31.58%) and people with political affluence (26.32%). Major portions (23.33%) of the encroached land were used for industrial development as well as housing and developmental projects. Negative health impact (40%) was found to be the main adverse effect of encroachment of the river. Other adverse effects included economic loss through obliteration of fisheries (35.71%), scarcity of clean water (32.14%), reduction of aesthetic value of the surroundings (25%) etc. For the protection of the river, the majority of the respondents opted for relocation of the industries (46.15%) and enforcement of strict rules and regulations (38.46%).

The Impact of Encroachment on the Distribution of Tree Species in Cross River National Park, Oban Division, Nigeria

Increasing human activities around protected area pinpoint to looming degradation and alteration of the component of such areas, especially where adequate measures are not taken to forestall encroachment. The Oban division of the Cross River National Park is one of the oldest rainforests and has been identified as a biodiversity hotspot. However, communities settling around the park have been involved in some economic activities for their livelihood. Resource utilization at the edge of the park may alter the components of the park such as species diversity. Therefore this study is geared towards assessing the impact of human encroachment and the concomitant impact on the distribution of species within the park. The study adopted participatory research methods which included Focus Group Discussion and participatory mapping as well as a plot based survey which involved the laying of sample plots within two zones of the park designated as areas bounded by cultivated land and areas bounded by fallow. Three 40 m × 40 m square plots are laid along a 320 meter transect measured from the boundary of the park at each buffer zone. The plots are separated by 100 m gap. From the result obtained, it is discovered that Musanga cercropoides dominates the outer plots of the cultivated zones and fallow zones comprising 20.2 and 21.5 percent respectively while Terminalia ivorensis dominates the middle and inner areas of the park. Moreover the composition of species decreases inward to the inner part of the park. Diversity index decreases in the order of 2.566 < 2.348 < 2.163 at the cultivated zones and 2.443 < 2.376 < 2.366 at the fallow zones. It is concluded that human activities close to the park alters the species composition of the park. Hence, it’s recommended that adequate alternatives livelihood and incentive be provided to support zone communities to reduce their dependents on the edge of the park.

因子图框架下里程计辅助GNSS/INS组合导航算法

在复杂观测环境下,GNSS/INS组合导航系统的GNSS信号易受干扰从而导致INS独立导航精度迅速下降。针对上述问题,本文基于因子图的里程计辅助GNSS/INS组合导航算法,利用里程计观测信息结合非完整性约束构建航向速度约束方程,同时采用能多次线性化计算和多次迭代的因子图优化方法进行参数估计。实际车载试验解算结果表明,在GNSS信号良好时,基于因子图方法比滤波方法具有更快的收敛时间,收敛速度提高了近10倍;在GNSS信号发生中断时,添加里程计辅助后组合导航系统在东向和北向分别提升了83%和89%。与传统的滤波融合手段相比,本文采用因子图优化后在东向和北向的定位精度分别有63%、70%的改善。

地下隧道-土体非线性动力相互作用的FE-IE-INE模型的研究

在考虑了土与结构的相互作用的基础上,采用FE-IE-INE模型来模拟土体的分层性、非线性以及土体和钢筋混凝土之间的滑移、拉裂、嵌入及土体的半无限边界.阐述了接触元建立的方法;推导了平行无限元的单元刚度矩阵方法以及无限元单元刚度矩阵组装成总体刚度矩阵的原理.通过对一双洞口矩形截面隧道的地震反应进行分析,为地下结构的抗震设计提供参考意见.

新版MEDL INE光盘著者检索与网上查询比较分析

目的 :评价不同的检索式的检索效果 ,旨在提高著者检索的查全率和查准率。方法 :举例介绍英语人名各种署名形式 ,针对 2 0 0 2年版MEDLINE光盘的著录特点 ,编制相应的检索式及与网上查询效果对比分析。结果 :遇姓名中含有前缀词、后缀词或复姓时 ,MEDLINE光盘和网上检索均可获得较高的查准率 ;而名缩写或截词后以及中、日文音译名检出的文献 ,则误检率高。调整检索式后 ,既保证了查全率 ,又剔除了误检文献。结论 :从而达到迅速而准确地检出所需文献的目的。

Influence of Seawall Line Choice on Tide Lock Drainage in Tidal Flat Inning——Cangdongpian Inning Area on the west part of Tiaozini Sand as a case study

Most of the flood from the wide inner lowland plain discharges through tide locks on coast, and the influence of tidal flat inning projects on the tide lock drainage must be solved by seawall line choice. Taking the Cangdongpian inning area on the west side of Tiaozini Sand as a case study, the paper analyzed the compages and validity of ebb tide water to maintain the flood discharge creek below the tide lock for different projects of seawall line. Result indicates that a rational seawall line program has little influence on the flood discharge of lock during the mean tide or general spring tides, but has certain influences during a storm surge or an extreme spring tide in autumn. However it could be resolved by several times of artificial scour on the creek.

基于自适应高斯渐进滤波的工程车GNSS/INS紧组合定位

研究了量测野值影响下的工程车GNSS/INS紧组合定位问题,提出了一种基于自适应高斯渐进滤波的车辆定位方法。首先,为降低量测野值对滤波器的破坏风险,利用假设检验方法对量测野值进行检测和剔除;其次,对于野值漏检测引起的定位性能下降的问题,设计了自适应的高斯渐进滤波方法来补偿量测的不确定性;特别地,利用线性化误差与系统估计误差的变化关系,对渐进量测更新方式进行了改进,从而实现对线性化误差的间接补偿。最后,通过工程车GNSS/INS紧组合定位实验进行结果分析,验证了所提方法的可靠性和优越性。

低压工作的高速10bit Pipelined ADC

本文提出了一种低压工作的高速10bit Pipelined ADC。采用自举时钟采样和Cascode频率补偿等方法,该ADC可以在低电压下工作,并达到较高的带宽。该ADC在HJTC 0.18-μmCMOS数模混合工艺下进行了设计仿真和流片测试,结果表明:当供电电压为1.8V,采样频率为62.5MSample/s时,所设计的ADC对于1MHz的输入信号转换有效位数可以达到52.2dB SFDR、44.8dB SNR和44.3dB SNDR。

INES简介及我国推行INES的方式初探

本文简单介绍了国际原子能机构(IAEA)向各成员国推荐使用的国际核事件分级表(INES)的出台背景、现状、评价标准及对一些重大核事件的分级示例。此外还对我国参加 INES 试用期间活动的方式、核电厂事件信息评价的传递途径及技术后援等提出初步看法。

基于MEMS IMU的GNSS RTK/INS紧组合定位分析

本文针对复杂动态的城市环境自动驾驶规模化应用需求,提出惯性单元辅助RTK快速收敛的自动驾驶低成本、高精度定位方法。使用MEMS IMU M39和战术级IMU Pos320,通过对多组实测车载数据进行仿真中断,得到INS位置漂移误差、模糊度收敛时间、模糊度固定正确性指标,再对无惯导辅助、M39辅助模糊度固定和Pos320辅助3种情形下的模糊度固定时间和定位精度进行了统计和分析。结果表明,M39在GNSS中断5 s时可辅助RTK实现模糊度瞬时固定,中断时间为10 s时可以将RTK模糊度收敛时间压缩至1/4。MEMS IMU的加入使得RTK模糊度固定错误个数显著下降,10 cm以内高精度定位占比由62.25%提高至98.44%。试验验证了MEMS IMU辅助RTK能够加快模糊度收敛速度,提高了其在自动驾驶导航定位应用中的精度和可靠性。

基于VB-EKF的GPS/INS松组合导航定位算法

针对应用在无人机(Unmanned Aerial Vehicle,UAV)中的全球定位系统/惯性导航系统(GPS/INS)松组合导航非线性系统受到外界噪声干扰导致量测噪声在滤波时不断变化,从而造成滤波精度下降等问题,提出一种变分贝叶斯扩展卡尔曼滤波(VB-EKF)算法。该算法利用EKF(Extended Kalman Filter)将非线性系统中的状态函数和量测函数展开为线性方程,并将两个不同的导航系统数据进行融合,避免了单系统导航定位发散的问题。考虑到组合系统中量测噪声的时变特性,引入变分贝叶斯算法进行改进,有效解决了系统滤波精度下降问题。仿真结果表明,VB-EKF较EKF算法可有效提高滤波稳定性,进而提高系统导航定位精度。

Fast fine acquisition algorithm of GPS receiver aided by INS information

Acquisition time of global position system （GPS） receiver, which is the main factor contributes to time to first fix （TTFF）, can be shortened by estimating the Doppler frequency shift through external inertial navigation system （INS） information and almanac data and reducing the searching area. The traditional fast acquisition is analyzed, the fast acquisition of the GPS receiver aided is presented by INS information, and the signal is fine captured by spectrum zooming. Then the algorithm is simulated by sampled GPS intermediate frequency （IF） signal and the result verifies that this acquisition can dramatically improve the capability of GPS receiver and reduce its acquisition time.

Chemistry and health beneficial effects of oolong tea and theasinensins

Among six major types of tea(white,green,oolong,yellow,black,and dark teas)from Camellia sinensis,oolong tea,a semi-fermented tea,with its own unique aroma and taste,has become a popular consumption as indicated by the increasing production.Representing the characteristic flavonoids of oolong tea,theasinensins are dimeric flavan-3-ols.Many recent studies have indicated that oolong tea and theasinensins possess several health benefit properties.We consider it significant and necessary to have a comprehensive review in the recent advances of oolong tea.Therefore,the aim of the present review is to provide a new perspective on oolong tea and its characteristic phytochemicals,theasinensins associated with health benefits,molecular action pathway,and chemical mechanism of theasinensin formation from scientific evidences available on the literature.Furthermore,the chemical characterization of the oxidation products and the model oxidation system to the chemical changes of theasinensins are also discussed.

Error Model of Rotary Ring Laser Gyro Inertial Navigation System

To improve the precision of inertial navigation system（INS） during long time operation,the rotation modulated technique（RMT） was employed to modulate the errorr of the inertial sensors into periodically varied signals,and,as a result,to suppress the divergence of INS errors.The principle of the RMT was introduced and the error propagating functions were derived from the rotary navigation equation.Effects of the measurement error for the rotation angle of the platform on the system precision were analyzed.The simulation and experimental results show that the precision of INS was ① dramatically improved with the use of the RMT,and ② hardly reduced when the measurement error for the rotation angle was in arc-second level.The study results offer a theoretical basis for engineering design of rotary INS.

基于组合历元新息抗差的GNSS/INS欺骗检测方法

针对传统的全球卫星导航系统/惯性导航系统(GNSS/INS)新息平均抗差欺骗检测算法对阶跃式欺骗存在检测时延长、对斜坡式欺骗检测不敏感等问题,提出了一种基于组合历元新息抗差的GNSS/INS欺骗检测方法。检测方法联合使用单历元新息和多历元新息平均检测方法提高检测效率,构造多历元等价权因子加大对斜坡式欺骗的削弱力度,按欺骗类型进行分类处理。实验结果表明,与单历元新息检测方法和多历元新息平均检测方法相比,所提方法更具敏感性,能够检测到单历元新息无法检出的10 m的阶跃式欺骗和多历元新息平均法无法检出的0.03 m/s的斜坡式欺骗;多历元等价权因子能削弱在检测到斜坡式欺骗之前误差跟踪效应对新息的影响;在多通道欺骗场景下,所提方法使检测时延缩短了21.3%,对欺骗进行分类处理使得与真实轨迹的最大位置误差减小了86.6%,均方根误差减小了96.8%。

LS-SVM和抗差估计的GNSS/INS紧组合欺骗检测算法

针对传统欺骗检测算法对斜率较小的斜坡式欺骗检测时间过长、虚警率和漏检率偏高等问题,提出一种最小二乘支持向量机(LS-SVM)和抗差估计的全球卫星导航系统(GNSS)和惯性导航系统(INS)紧组合欺骗检测算法。所提算法通过抗差自适应调整增益矩阵,有效削弱欺骗对新息的影响,将抗差优化的训练数据集经LS-SVM回归得到的预测新息来代替滤波器中的欺骗新息,从而进一步提高对斜率较小的斜坡式欺骗检测处理能力。仿真结果表明:在检测欺骗值为0.1 m/s的斜坡式欺骗时,所提算法与传统算法相比,检测时间缩短26.65%,虚警率降低40.63%,定位精度提高72.72%。所提算法具有检测快、虚警率低的优势,适用于GNSS/INS紧组合导航用户的斜坡式欺骗检测。