Sand-dust storms in China: temporal-spatial distribution and tracks of source lands

Sand-dust storm is a special natural disaster that frequently occurs in deserts and their surrounding areas. With the data published onSurface Meteorological Monthly Bulletin andSurface Chart during 1971–1996, the temporal-spatial distribution and annual variation of sand-dust storms are analyzed on the basis of the case study of atmospheric processes. Furthermore, the tracks and source areas of sand-dust storms are determined with the aid of GIS. The results show that except some parts of Qinghai Province and Inner Mongolia as well as Beijing, sand-dust storms decrease apparently in time and space in recent decades in China. Sand-dust storms occur most frequently in spring, especially in April. According to their source areas, sand-dust storms are classified into two types, i.e., the inner-source and outer-source sand-dust storms. Most of the outer-source sand-dust storms move along the north and west tracks. The north-track outer-source sand-dust storms always intrude into China across the Sino-Mongolian border from Hami, a city in the eastern part ofXinjiang, to Xilin Gol, a league in Inner Mongolia, while the west-track ones intrude into China from both southern and northern Xinjiang. The source lands of inner-source sand-dust storms concentrate in the Taklimakan Desert and its surrounding areas in southern Xinjiang, southern part of the Junggar Basin in north of Xinjiang, the Hexi Corridor in western Gansu Province, the dry deserts of Inner Mongolia and the Qaidam Basin in Qinghai.

Dimension decomposition algorithm for multiple source localization using uniform circular array

A dimension decomposition(DIDE)method for multiple incoherent source localization using uniform circular array(UCA)is proposed.Due to the fact that the far-field signal can be considered as the state where the range parameter of the nearfield signal is infinite,the algorithm for the near-field source localization is also suitable for estimating the direction of arrival(DOA)of far-field signals.By decomposing the first and second exponent term of the steering vector,the three-dimensional(3-D)parameter is transformed into two-dimensional(2-D)and onedimensional(1-D)parameter estimation.First,by partitioning the received data,we exploit propagator to acquire the noise subspace.Next,the objective function is established and partial derivative is applied to acquire the spatial spectrum of 2-D DOA.At last,the estimated 2-D DOA is utilized to calculate the phase of the decomposed vector,and the least squares(LS)is performed to acquire the range parameters.In comparison to the existing algorithms,the proposed DIDE algorithm requires neither the eigendecomposition of covariance matrix nor the search process of range spatial spectrum,which can achieve satisfactory localization and reduce computational complexity.Simulations are implemented to illustrate the advantages of the proposed DIDE method.Moreover,simulations demonstrate that the proposed DIDE method can also classify the mixed far-field and near-field signals.

DERIVATION AND INTEGRAL SLIDING MODE VARIABLE STRUCTURE CONTROL OF HYDRAULIC VELOCITY TRACKING SYSTEM

The velocity tracking control of a hydraulic servo system is studied. Sincethe dynamics of the system are highly nonlinear and have large extent of model uncertainties, suchas big changes in load and parameters, a derivation and integral sliding mode variable structurecontrol scheme (DI-SVSC) is proposed. An integral controller is introduced to avoid the assumptionthat the derivative of desired signal must be known in conventional sliding mode variable structurecontrol, a nonlinear derivation controller is used to weaken the chattering of system. The designmethod of switching function in integral sliding mode control, nonlinear derivation coefficient andcontrollers of DI-SVSC is presented respectively. Simulation shows that the control approach is ofnice robustness and improves velocity tracking accuracy considerably.

A Particle Filter Based Compressive Sensing Method for Tracking Moving Wideband Sound Sources

Tracking moving wideband sound sources is one of the most challenging issues in the acoustic array signal processing which is based on the direction of arrival(DOA) estimation. Compressive sensing(CS) is a recent theory exploring the signal sparsity representation, which has been proved to be superior for the DOA estimation. However, the spatial aliasing and the offset at endfire are the main obstacles for CS applied in the wideband DOA estimation. We propose a particle filter based compressive sensing method for tracking moving wideband sound sources. First, the initial DOA estimates are obtained by wideband CS algorithms. Then, the real sources are approximated by a set of particles with different weights assigned. The kernel density estimator is used as the likelihood function of particle filter. We present the results for both uniform and random linear array. Simulation results show that the spatial aliasing is disappeared and the offset at endfire is reduced. We show that the proposed method can achieve satisfactory tracking performance regardless of using uniform or random linear array.

Linear Track Estimation Using Double Pulse Sources for Near-Field Underwater Moving Target

The double pulse sources （DPS） method is presented for linear track estimation in this work. In the field of noise identification of underwater moving target, the Doppler will distort the frequency and amplitude of the radiated noise. To eliminate this, the track estimation is necessary. In the DPS method, we first estimate bearings of two sinusoidal pulse sources installed in the moving target through baseline positioning method. Meanwhile, the emitted and recorded time of each pulse are also acquired. Then the linear track parameters will be achieved based on the geometry pattern with the help of double sources spacing. The simulated results confirm that the DPS improves the performance of the previous double source spacing method. The simulated experiments were carried out using a moving battery car to further evaluate its performance. When the target is 40-60m away, the experiment results show that biases of track azimuth and abeam distance of DPS are under 0.6° and 3.4m, respectively. And the average deviation of estimated velocity is around 0.25m/s.

Integrated site-specific quantification of faecal bacteria and detection of DNA markers in faecal contamination source tracking as a microbial risk tracking tool in urban Lake ecosystems

The presence of feacal-derived pathogens in water is responsible for several infectious diseases and deaths worldwide. As a solution, sources of fecal pollution in waters must be accurately assessed, properly determined and strictly controlled. However, the exercise has remained challenging due to the existing overlapping characteristics by different members of faecal coliform bacteria and the inadequacy of information pertaining to the contribution of seasonality and weather condition on tracking the possible sources of pollution. There are continued ef forts to improve the Faecal Contamination Source Tracking(FCST) techniques such as Microbial Source Tracking(MST). This study aimed to make contribution to MST by evaluating the efficacy of combining site specific quantification of faecal contamination indicator bacteria and detection of DNA markers while accounting for seasonality and weather conditions' eff ects in tracking the major sources of faecal contamination in a freshwater system(Donghu Lake, China). The results showed that the use of cyd gene in addition to lacZ and uidA genes differentiates E. coli from other closely related faecal bacteria. The use of selective media increases the pollution source tracking accuracy. BSA addition boosts PCR detection and increases FCST efficiency. Seasonality and weather variability also influence the detection limit for DNA markers.

Approximation of Derivative for a Singularly Perturbed Second-Order ODE of Robin Type with Discontinuous Convection Coefficient and Source Term

In this paper, a singularly perturbed Robin type boundary value problem for second-order ordinary differential equation with discontinuous convection coefficient and source term is considered. A robust-layer-resolving numerical method is proposed. An e-uniform global error estimate for the numerical solution and also to the numerical derivative are established. Numerical results are presented, which are in agreement with the theoretical predictions.

Nonlinear Derivative and Integral Sliding Control for Tracked Vehicle Steering with Hydrostatic Drive

In the steering process of tracked vehicle with hydrostatic drive,the motion and resistance states of the vehicle are always of uncertain and nonlinear characteristics,and these states may undergoe large-scale changes.Therefore,it is significant to enhance the steering stability of tracked vehicle with hydrostatic drive to meet the need of future battlefield.In this paper,a sliding mode control algorithm is proposed and applied to achieve desired yaw rates.The speed controller and the yaw rate controller are designed through the kinematics and dynamics analysis.In addition,the nonlinear derivative and integral sliding mode control algorithm is designed,which is supposed to efficiently reduce the integration saturation and the disturbances from the unsmooth road surfaces through a conditional integrator approach.Moreover,it improves the response speed of the system and reduces the chattering by the derivative controller.The hydrostatic tracked vehicle module is modeled with a multi-body dynamic software RecurDyn and the steering control strategy module is modeled by MATLAB/Simulink.The co-simulation results of the whole model show that the control strategy can improve the vehicle steering response speed and also ensure a smooth control output with small chattering and strong robustness.

Geochemical Evidence for Coal and Carbonaceous Mudstone as the Possible Major Oil Source Rock in the Jurassic Turpan Basin, Northwest China

Petroleum geologists have debated whether the hydrocarbons from Jurassic coal measures are derived from the coals, carbonaceous mudstones or coal-measure mudstones in the Turpan Basin. Based on the geochemistry analysis of the 20 crude oils and 40 source rocks from the Turpan Basin, some data have been obtained as follows： carbon preference index and methylphenanthrene index of the Jurassic oils are 1.16-1.45 and 0.28-0.80, and the ααα C29 sterane 20S/（20S＋20R） and C29 sterane ββ/（ββ＋αα） are 0.44-0.51 and 0.4-0.54 respectively, which show the normal maturity of oils; the vitrinite reflectance of the source rocks from the Xishanyao to Badaowan Formations range from 0.47% to 0.97%, which indicate immature to mature thermal evolutionary stage and sufficient conditions for generating mass mature oil. The effect of hydrocarbon expulsion should be considered when studying the source of coal-derived oil by using Biomarkers. Biomarkers in the Jurassic oils from the basin are similar to those in the coals and carbonaceous mudstones, with a strong predominant content of pristane, relatively high ratio of C15 /C16 sesquiterpenoids （1）, a relatively high content of low carbon number tricyclic terpanes and C 24 tetracyclic terpane, little gammacerane and C 29 Ts detected, an absolute predominant content of C29 sterane and a relatively high content of diasterane. However, the opposite characteristics are shown in mudstones, with an approximately equal content of pristane and phytane, relatively low ratio of C15 /C16 sesquiterpenoids （1）, a relatively high content of high carbon number tricyclic terpanes and a low content of C 24 tetracyclic terpane, peaks of gammacerane and C29 Ts detected obviously and an increasing C27 sterane content. All of these characteristics identify the coals and carbonaceous mudstones as the possible major oil source rocks in this area, and they were formed in the stronger oxidizing environment with shallower water than mudstones.

Discussion on heat source mechanism and geothermal system of Qinghai Gonghe-Guide Basin

The Qinghai Gonghe-Guide Basin together with the alternatively distributed mountainous region shows characteristics that the conductive geothermal resource of the basin has high geothermal gradient, the granite occurs in the bottom of borehole for geothermal exploration, and the convective hot springs in the basin-edge uplift fracture are in zonal distribution and with high-temperature geothermal water. There are still some divergences about the heat source mechanism of the basin. In this paper, queries to the view of mantle-derived heat source have been put forward, coming up with geochemical evidences to prove that the radiogenic heat of granite is the heat source within the mantle. Additionally, temperature curve is drawn based on the geothermal boring and geochemical geothermometer has been adopted for an estimation of the temperature and depth of the geothermal reservoir, it has been found that the surrounding mountains belong to the medium-temperature geothermal system while the area within the basin belongs to the high-temperature geothermal system with the temperature of borehole bottom reaching up to 175-180 ℃. In this paper, discussions on the problems existing in the calculation of geothermal gradient and the differences generated by the geothermal system have been carried out.

Burial fluxes and source apportionment of carbon in culture areas of Sanggou Bay over the past 200 years

In this study, we assessed the burial fluxes and source appointment of different forms of carbon in core sediments collected from culture areas in the Sanggou Bay, and preliminarily analyzed the reasons for the greater proportion of inorganic carbon burial fluxes （BFTIc）. The average content of total carbon （TC） in the Sanggou Bay was 2.14%. Total organic carbon （TOC） accounted for a small proportion in TC, more than 65% of which derived from terrigenous organic carbon （Ct）, and while the proportion of marine-derived organic carbon （Ca） increased significantly since the beginning of large-scale aquaculture. Total inorganic carbon （TIC） accounted for 60%-75% of TC, an average of which was 60%, with a maximum up to 90% during flourishing periods （1880-1948） of small natural shellfish derived from seashells inorganic carbon （SheU-IC）. The TC burial fluxes ranged from 31 g/（m2.a） to 895 g/（m2.a） with an average of 227 g/（m2.a）, which was dominated by TIC （about 70%）. Shell-IC was the main source of TIC and even TC. As the main food of natural shellfish, biogenic silica （BSi） negatively correlated with BFTIc through affecting shellfish breeding. BFTIc of Sta. S1, influenced greatly by the Yellow Sea Coastal Current, had a certain response to Pacific Decadal Oscillation （PDO） in some specific periods.

Using Host-Specificity of Cryptosporidium to Understand Contaminant Sources, Seasonality, and Human Health Risk in Three Watersheds of Differing Land-Use

Three tributaries of the Grand River watershed (Ontario, Canada), each representing different watershed types (urban, agricultural/rural, and mixed land-use) were examined to understand the spatial, temporal, and host-source distribution of the waterborne pathogen, Cryptosporidium. Cryptosporidium was frequently found throughout the study (73%, 65/89) with occurrence and concentrations observed to be similar among the varying watershed types. However, applying advanced genotyping techniques, marked differences in dominant host sources could be observed in each watershed. The agricultural/rural and mixed land-use watersheds were dominated by genotypes typically associated with cattle (i.e., C. andersoni), while the urban watershed had the highest diversity of Cryptosporidium genotypes with a variety of wildlife as the common source of contamination (e.g., muskrat and cervine genotypes). A similar seasonal trend observed in the urban, agricultural, and mixed land-use watershed suggests that factors beyond specific land use activities (e.g. autumn manure spreading) may influence the timing and concentration of Cryptosporidium in these streams. Corresponding genotyping results provided additional insight into source inputs during these seasonal peaks, indicating that wildlife may be important seasonal contributors to Cryptosporidium contamination in these streams. Despite the abundance of Cryptosporidium in these watersheds, most of the genotypes observed were of limited human health importance. This study provides evidence regarding the significance of including genotyping results into studies examining waterborne Cryptosporidium. Using this technique can provide a greater understanding of the risk to the population using water sources, as well as provide insight into the probable sources and timing of contamination. This ancillary information can contribute to implementation of targeted management strategies to further protect sources of drinking water and recreation areas.

Optimum Energy Harvesting for Series-Connected Power Sources with Uniform Voltage Distribution

This paper presents a power system architecture where SIPO （series-input parallel-output） converters are controlled to achieve uniform inpt voltages across their respective series-connected power sources while also tracking the system optimum power point; the system optimum power point is the maximum power drawn from the series-connected power sources while their voltages are kept uniformly distributed. With proper uniform input voltage distribution control, near maximum use of the power sources is achieved by employing only one MPT （maximum power tracking） controller instead of multiple MPT controllers dedicated for their respective power sources. Provided that the maximum power point voltages of the input power sources are similar, the resulting system architecture offers near-maximum power transfer with a lower parts count. A feasibility study using computer simulation has successfully validated two SIPO power architectures and their control concepts for optimum power transfer.

面向光伏能量收集应用的实时MPPT预估算法研究

对于环境中存在的各种类型能量源,其往往具有不同的阻抗特性以及输出功率范围。为了提高能量收集系统的能量萃取能力,合理的接口电路设计是关键。基于此,通过对环境中光伏(Photovoltaic,PV)能量源微弱直流特性以及高效率收集和转化的研究,在传统开路电压法(Open-Circuit Voltage,OCV)的基础上,结合输入电压纹波控制,提出了一种可实时最大功率点追踪(Maximum Power Point Tracking,MPPT)的预估算法。该预估算法根据能量源的输出特性,采用了分数开路电压法(Fractional Open-Circuit Voltage,FOCV),并根据纹波大小动态调节变换器的工作模式,实现阻抗匹配。为了尽可能减小因采样带来的能量损失,采用可片上全集成的较小的采样电容,并逐周期的进行开路电压采样和计算,实现了对源功率变化的高精度追踪。仿真结果表明,所提出的追踪算法能够实时监测能量源的状态,具有高的追踪速度和追踪精度,且采样时间仅需100 ns。能量源功率在1μW~10 mW范围内变化时,最短的追踪时间仅需4.37μs,追踪精度可达99.7%。

油气地质勘探将从烃源岩时代进入幔源油气新时代

简要梳理了人类石油勘探发展历程,分析并研究了国内外25个油田(或盆地、油区)的勘探资料,得出结论:石油地质勘探经历过的第一个阶段是背斜(构造)勘探阶段(19世纪60年代~20世纪60年代),第二个阶段是烃源岩勘探阶段(20世纪30年代至今),现在已经进入一个全新的阶段——幔源油气勘探时代。依据幔源油气理论,提出了创新的“盆-壳-幔镜像叠置成藏模式”。

基于广义互相关时延估计(TDOA)算法的声源定位跟踪系统设计与实现

为实现在二维平面内对声源进行实时定位和动态跟踪,运用时延估计(TDOA)互相关算法设计一种原声监听头阵列的CC-TDOA声源定位跟踪系统,实现对多个原声监听头进行同步采样,再进行信号放大及运算处理,运用LCD屏实时显示目标声源的距离和方位角度,同时运用二维云台控制激光笔对准声源,并持续动态跟踪声源。模拟仿真及真实环境实验测试表明,采用基于到达时间差的互相关定位算法,计算量小,精度较高,测试角度误差小于2o,距离误差小于1.2%,可以满足多种智能应用场合中声源实时定位与跟踪的要求。

滇西南沧源岩溶洞穴硝洞堆积物来源分析

岩溶洞穴是第四纪时期古人类活动的重要场所。开展岩溶洞穴碎屑沉积物的沉积特征及物质来源分析,对其沉积环境演变历史及古人类活动研究都具有重要意义。本文在了解硝洞洞穴及其周围不同沉积物黏土矿物特征的基础上,结合硝洞洞穴沉积物的粒度和矿物学等特征对其物质来源进行了分析。结果表明:硝洞洞穴沉积物的主要来源为洞穴外地表较高处的沉积物,其通过片流作用被带入洞穴内进行堆积。其次,还同时堆积有少量灰岩不溶性物质及其经历进一步风化成壤作用后形成的物质,总体可能存在4次进一步的风化成壤作用。此外,也有洞壁崩塌的石灰岩角砾和岩块参与堆积,总体存在4次大量灰岩角砾或岩块参与堆积过程,而最近一次的堆积作用,显然受到了人类活动的影响。

李渡特香型大曲层次间微生物群落结构与风味物质变化规律研究

目前对于特香型大曲不同层次间微生物群落结构和数量变化特征,及其与风味物质的关联性尚不清晰。该研究运用绝对定量和相对定量扩增子测序技术,揭示特香型大曲不同层次结构的微生物组成及变化规律,并对主要细菌和真菌的来源进行了溯源分析。同时运用顶空固相微萃取-气相色谱质谱联用技术(headspace solid phase microextraction-gas chromatography-mass spectrometry,HS-SPME-GC-MS),比较分析大曲不同层次的风味化合物含量。结果表明,曲心的细菌总生物量显著低于曲皮和中层,为曲皮的55%,中层的53%。魏斯氏菌属(Weissella)、乳杆菌属(Lactobacillus)和肠杆菌属(Enterobacter)为曲皮的主要细菌类型,高温放线菌属(Thermoactinomyces)为曲心的特征优势细菌,而糖多孢菌属(Saccharopolyspora)在中层和曲心含量远高于曲皮。伊萨酵母属(Issatchenkia)和丝孢毕赤酵母属(Hyphopichia)为曲皮的主要酵母,曲霉属(Aspergillus)为曲心的优势霉菌。曲心的醇类、醛酮类、吡嗪类和醚酚类的总含量均高于曲皮和中层,而曲皮的酯类的总含量高于曲心。该项研究结果为优化特香型大曲制曲工艺,进而运用生态发酵技术提升大曲品质提供了重要参考。

基于相关性反馈的开源系统跨层需求追踪方法

大型复杂软件系统的需求分析与生成是一个由上而下逐层分解的过程,跨层需求间追踪关系的构建对于项目的管理、开发与演化都至关重要.开源系统的松耦合贡献方式需要每位参与者能便捷地理解需求的来龙去脉及需求状态,这依赖跨层需求间的追踪.问题描述日志是开源系统中需求的常见呈现方式,其无固定模板要求,内容多样(含文本、代码、调试信息等),术语使用自由,跨层需求间抽象层次大,给自动追踪带来极大的挑战.提出一种面向关键特征维度的相关性反馈方法,通过静态分析项目代码结构,抽取代码相关术语及其间的关联强度,构建代码词汇库,以缓解跨层需求的抽象层次差距及用语不统一的问题;通过度量词汇对需求描述的重要性并基于此筛选关键特征维度,以对查询语句进行针对性的优化,有效减少需求描述长度、内容形式等方面的噪音.通过在3个开源系统需求集上针对两个场景的实验,表明所提方法相比基线方法在跨层需求追踪方面的优越性,相比VSM、Standard Rocchio和Trace BERT,F2值的最大提升分别可达29.01%、7.45%和59.21%.

计及网络动态特性的电-热互联系统仿射优化法

热网动态特性带来能量传输延时的同时,使得空间上的源荷不确定性对系统造成的影响存在时序上的先后差异,导致电-热互联系统日前调度转变为复杂的时空耦合问题。为此,该文提出一种计及网络动态特性的仿射优化法。首先,利用流量分段法与节点网络模型,构建计及能量传输延时且适用于环网的热网动态模型。在此基础上,利用仿射算法与牛顿-拉夫逊能流计算原理,通过线性化建模方式与模型凸化方法,构建仿射凸优化模型。其次,利用仿射优化法解决电-热互联系统不确定性优化调度问题,实现对源荷不确定性传播轨迹的跟踪及其影响的量化分析。最后,33节点电-热互联系统仿真算例证明,所提方法能够揭示网络动态特性下源荷不确定性影响机理,并获得具有低保守性、高经济性的调度方案。