Pattern analysis of a linear dune field on the northern margin of Qarhan Salt Lake,northwestern China

In terms of formation mechanisms of linear dunes,there are open arguments for their widespread distribution and multi-morphological diversities.In order to clarify the formation mechanism of linear dunes of Qarhan Salt Lake,we used pattern analysis method to analyze the statistical characteristics and spatial variation of their pattern parameters.Except at the west-northwest margin,the pattern parameters showed regular spatial variation from the up-middle part towards the downwind end of the dune field.Based on the cumulative probability plots for inter-crest spacing and crest length,we divided the linear dunes into three groups,which corresponding to the three evolution stages of these dunes.The first group comprises erosional relics,with shorter crests,smaller inter-crest spacing and more random dune orientation.The second group comprises dunes whose sand supply is just sufficient to maintain stability and these dunes are approaching the net erosion stage.The crest length and inter-crest spacing of these dunes are much larger than those of the first group,and dune orientation is closer to the resultant drift direction （RDD） .The last group comprises linear dunes that are still undergoing vertical accretion and longitudinal elongation,which follows the RDD of the modern wind regime.The presence of regular spatial variation of pattern parameters and a similar geometry with the vegetated linear dunes suggest that deposition and erosion coexist in the development and evolution of linear dunes of Qarhan Salt Lake,i.e.deposition predominates at the downwind end of linear dunes in the vertical accretion and longitudinal elongation stage,whereas erosion mainly occurs at the upwind end of linear dunes in the degradation stage.Therefore,the formation mechanism of linear dunes in Qarhan Salt Lake can be reasonably explained by the combination of depositional and erosional theories.

An Analysis of the Correlation between the Changes in Sa-tellite DNA Methylation Patterns and Plant Cell Responses to the Stress

The differences in satellite DNA methylation pattern of corn seedlings with various spontaneous chromosome aberration yields and changes in methylation pattern of these DNA sequences under different exposure modes of acute UV-C and chronic gamma-irradiations have been investigated. The obtained experimental data and the conducted correlation analysis demonstrated the significant correlation between the satellite DNA methylation pattern varieties and chromosome aberration yields under various stress exposure modes. The role of satellite DNA methylation pattern variability and its changing in key responses to stress such as mobile elements’ activation, cell’s passage of checkpoints, and homological repair was discussed.

Formulation of Optimization Problems with Radiation Field Phases as Design Variables for Pattern Synthesis of Linear Antenna Arrays

Pattern synthesise of antenna arrays is usually complicated optimization problems,while evolutionary algorithms(EAs)are promising in solving these problems.This paper does not propose a new EA,but does construct a new form of optimization problems.The new optimization formulation has two differences from the common ones.One is the objective function is the field error between the desired and the designed,not the usual amplitude error between the desired and the designed.This difference is beneficial to decrease complexity in some sense.The second difference is that the design variables are changed as phases of desired radiation field within shaped-region,instead of excitation parameters.This difference leads to the reduction of the number of design variables.A series of synthesis experiments including equally and unequally spaced linear arrays with different pattern shape requirements are applied,and the effectiveness and advantages of the proposed new optimization problems are validated.The results show that the proposing a new optimization formulation with less complexity is as significant as proposing a new algorithm.

Non-Linear Synthesis Problems for Plane Radiating Systems According to the Prescribed Power Directivity Pattern

A variational formulation of the synthesis problem for plane radiating systems according to the prescribed power directivity pattern (DP) is considered. The function representing the mean-square deviation of the prescribed and synthesized power DPs and containing the additional term with squared norm of the current or field in the antenna aperture is considered as the criterion of optimization. Freedom to choose the phase DP is used to improve the proximity of the prescribed and synthesized DPs. In such formulation, the classes of non-linear problems, for which the non-uniqueness of solutions, their branching and bifurcation are characteristic, arise. The properties of solutions depend on the electric size of radiating system and prescribed power DP. From a practical point of view, the existence of different solutions creating the same or similar DPs, gives the opportunity to choose the solution that has a simpler implementation. The synthesis problems for plane radiating systems and plane arrays are considered.

Correlation of the quantifiable parameters of blood flow pattern derived with dynamic CT in solitary bronchogenic adenocarcinoma

Objective:To evaluate the correlation of the quantifiable parameters of blood flow pattern derived with dynamic CT in solitary bronchogenic adenocarcinoma(SBA).Methods:46 patients with solitary bronchogenic adenocarcinomas (SBA)(diameter≤4 cm)underwent multi-location dynamic contrast material-enhanced(nonionic contrast material was administrated via the antecubital vein at a rate of 4 mL/s by using an autoinjector 90 mL,4×5 mm or 4×2.5 mm scanning mode with stable table were performed)serial CT.Precontrast and postcontrast attenuation on every scan was recorded.Perfusion (PBA),peak height(PHBA),ratio of peak height of the SPN to that of the aorta(BA-to-A ratio)and mean transit time(MTT)were calculated.The correlation between peak height of the aorta(PHA)and parameters of the SBA(PHBA,BA-to-A ratio,PBA,and MTT)and those among parameters of the SBA were assessed by means of linear regression analysis.Regression equation among parameters of the SBA were obtain by means of stepwise regression.Results:The correlation between the SBA peak height(PHBA,36.78 HU±12.02)and the aortic peak height(PHA)was significant(r=0.506,P<0.0001).No significant cor- relation was found between the BA-to-Apeak height ratio(15.33%±4.55)and the aortic peak height(r=0.130,P=0.388> 0.05)as it was between the SBA perfusion(PBA,31.86 mL/min/100 g±9.74)and the aortic peak height(r=0.049,P=0.749 >0.05).The SBA perfusion correlated with the PHBA and the BA-to-A peak height ratio(r=0.394,P=0.007<0.05;r=0.407, P=0.005<0.05).The PHBA correlated positively with the BA-to-A peak height ratio(r=0.781,P<0.0001).Mean transit time was 14.84 s±5.52.PBA=18.500+0.872×BA-to-A ratio.BA-to-A ratio=4.467+0.295×PHBA.Conclusion:The linear correlation between the SBA perfusion and BA-to-Aratio and that between BA-to-Aratio and PHBA can be expressed by equation. It is possible to design a simpler scanning procedure of investigation of bronchogenic adenocarcinoma angiogenesis.

从“线性”到“复合”:我国农家书屋的供给模式转向

文章基于复合治理理论,围绕主体、空间、资源、工具、客体5个核心要素,结合线性供给模式下农家书屋面临的供给困境,构建主体结构多元合作、空间功能深度融合、资源供需高效匹配、工具组合灵活运用、供给客体精准识别的我国农家书屋复合供给模式,并提出相应的实现路径,即加强多元主体间的交流与合作,拓展农家书屋空间功能,促进资源供需精准对接,协调工具传承与创新的关系,实现服务共性与客体个性的有机结合。

一种等通量波束的多极化可重构天线

随着航天技术的革新,对近地轨道的通信需求逐年增高。近地轨道卫星就在此背景下产生,主要应用于遥感探测天气预报和数据通信领域。由于近地轨道卫星天线辐射波束所覆盖的地球表面是球面,因此波束通常设计为等通量形式。由于卫星通信通常存在极化失配、多径效应等问题,选择多极化而不是圆极化作为近地卫星天线的工作状态能更好地适应复杂的工作环境,保证通信质量,将等通量波束天线和多极化可重构技术结合起来有很大的应用前景。基于一对正交圆极化波能合成线极化波的设计原理,文中提出了一种具有等通量波束的多极化可重构天线,该天线由可重构馈电网络和带扼流环的隔片极化器圆波导组成。馈电网络中嵌入单刀四掷开关(SP4T)与单刀双掷开关(SP2T),通过改变开关的工作状态,馈电网络将给圆波导提供不同的馈电条件,在圆波导内隔片的作用下天线实现两种圆极化与两种线极化的可重构。通过在圆波导口引入扼流环以及波导口作“T”型开槽处理,实现波束赋形,并且保证天线在不同极化状态下辐射等通量波束。实测结果显示,天线在不同的极化状态下-15 dB重叠阻抗带宽14.7%,覆盖4.80~5.56 GHz,方向图顶部在θ为-24°~+24°范围内具有平坦效果,圆极化状态下空间轴比覆盖-51°~+50°,覆盖范围大于方向图顶部平坦范围。天线实测结果与仿真结果有较好的一致性,具有多极化和方向图顶部平坦的优势,可满足移动通信和卫星通信中多极化应用场景的需要。

低成本接收阵列方向图测试系统与方法

采用传统的相控阵测试方法对数字阵列及数字波束合成进行测试,存在系统复杂、设备齐套周期长、问题难解耦等弊端。因此,对于数字阵列及相关算法,需要一种不依赖天线和物理环境,且能够以低成本和高效率,在系统开发中期完成相关性能评估和迭代的方法。给出一种基于阵列信号模拟技术的低成本接收阵列方向图测试系统,并提出了随机虚拟相移技术用于解决测试精度不足的问题。基于简要的理论分析、给出了测试平台构成和测试流程,并通过仿真和实测验证了方法的有效性。

线性模型下二水平正规设计效应混杂的度量

在线性模型中,试验设计效应之间的混杂会导致参数估计存在某种偏差.针对二水平正规设计,本文引入混杂指标集来度量这类偏差,并提出一种新方法来研究其性质,揭示它与别名效应数型、别名关系数及字长型之间的关系,得到了低阶效应混杂指标的计算公式以及最优设计存在的一些必要条件,并通过例子展示了所得到的理论结果.

Changes of coastline and tidal flat and its implication for ecological protection under human activities: Take China’s Bohai Bay as an example

The change processes and trends of shoreline and tidal flat forced by human activities are essential issues for the sustainability of coastal area,which is also of great significance for understanding coastal ecological environment changes and even global changes.Based on field measurements,combined with Linear Regression(LR)model and Inverse Distance Weighing(IDW)method,this paper presents detailed analysis on the change history and trend of the shoreline and tidal flat in Bohai Bay.The shoreline faces a high erosion chance under the action of natural factors,while the tidal flat faces a different erosion and deposition patterns in Bohai Bay due to the impact of human activities.The implication of change rule for ecological protection and recovery is also discussed.Measures should be taken to protect the coastal ecological environment.The models used in this paper show a high correlation coefficient between observed and modeling data,which means that this method can be used to predict the changing trend of shoreline and tidal flat.The research results of present study can provide scientific supports for future coastal protection and management.

检验检测服务业经营绩效的关键影响因素研究——基于双循环视角

利用多元线性回归模型,探究影响我国各地区检验检测服务业经营绩效的关键因素.选取机构营收额作为被解释变量,进出口贸易、第二产业发展、第三产业发展、受教育程度作为解释变量,进行我国整体分析和地区异质化分析.研究结果表明:产业结构优化是提升检验检测服务业经营绩效的决定因素,进出口贸易对检验检测服务业的发展具有显著的正向影响,但进出口贸易的正向作用明显小于产业结构的作用.人力资源错配是造成东部地区人力资本抑制检验检测服务业经营绩效的重要原因.

基于样板的GPU线程快速构造方法

阐述通用计算任务可利用GPU的多线程获得并行加速,根据预先设定的样板,对整个线程一次性创建,加快了线程的构造时间。样板分为线性和瓦片两种,分别处理线性和矩形排列的工作组。模拟仿真测试表明,基于样板的线程构造时间一般为8cycles左右,比传统方法获得3倍的提升。该方法易于硬件实现,可以在之前电路上直接扩展,实现功能向前兼容。

2022年5月欧亚大陆中高纬度地区“三极子”型异常气温的特点和成因

2022年5月,欧亚大陆中高纬度地区出现了“三极子”型的异常表面气温(Surface air temperature,SAT),东欧和东北亚偏冷,欧亚大陆中北部偏暖,是2000年以来5月最明显的一次气温异常。基于多种资料和方法,本文探讨了此次“三极子”型异常气温的特点和成因。结果表明:“三极子”型异常SAT在5月15—27日期间最显著,与“三极子”型的异常大气环流密切相关,偏暖(冷)处受到了异常高(低)压和异常偏南(北)风的影响,欧亚大陆中北部(东欧)还受到了异常下沉(上升)运动和净热通量正(负)异常的影响,东北亚较弱的异常环流可能是该处SAT异常较弱的原因。比较不同物理过程对三极子各区域SAT异常的贡献,发现异常温度平流(异常经向风对气候态温度的平流)在“三极子”型异常SAT的形成中贡献最大,贡献率分别为40.5%、18.7%和17.7%。“三极子”型异常环流与两支波列有关。里海以北和中纬度北大西洋东部分别在5月9—10日和15—17日期间有与低层辐合异常和高层辐散异常相关的异常上升运动,导致降水异常偏多。线性斜压模式结果证明,降水导致的潜热释放在对流层形成的异常热源可以激发出欧亚大陆上的“三极子”型环流。

ARCGIS软件在第三次国土调查中应用研究

ARCGIS软件是测绘地理信息项目中常用软件。第三次国土调查是作为一项在国情国力方面的调查,其目的是调查清楚全国土地资源利用情况和国土地类现状,为以后诸如国土空间规划、基本农田划定、生态文明建设等方面提供基础数据和政策导向。在第三次国土调查中,ARCGIS为内业数据处理提供了强大的技术支撑。ARCGIS软件可对线状地物图斑化和野外举证数据提前批处理进行详细的研究,在水利、农业、生态、交通、林业、住建等方面都有非常广泛的应用。

Oscillation Result for Some Non-homogeneous Linear Differential Equations and Its Application

This paper investigates solutions of some non-homogeneous linear differential equations, which have non-homogeneous term as the small function of solution. Using the similar method, we can generalize the result of G.Gundersen and L.Z.Yang.

中远程一体化车载雷达线阵天线的设计

该文提出了一种新型的宽带近接耦合毫米波微带阵列天线,并将其作为77~81 GHz中远程汽车雷达的专用天线。该天线阵列由微带线及一系列矩形和多边形辐射单元组成。辐射单元在微带线两侧呈周期性分布,间隔约为引导波长的1/2。为增强激励耦合引入了矩形和多边形辐射单元,在拓宽阻抗带宽的同时,抑制了带外频率。不同辐射单元和矩形反射槽相匹配,达到波束赋形的效果,实现了平肩膀辐射方向图。通过调整辐射单元与微带线的间隔,控制辐射单元的归一化电阻。在工作频率为77~81 GHz时,阵列天线的增益超过14 dBi,阻抗带宽达到7.47%(76.5~82.4 GHz)。对实物样本进行加工及性能检测,测试表明,仿真与实测数据基本一致。

铜锌铝合金表面非线性振荡花样的研究

在Ｃｕ－Ｚｎ－Ａｌ形状记忆合金表面观察到尚未被人们认识的非线性振荡花样。这些花样经计算机图像处理得知，在空间和时间上明显呈现分形特征。这种振荡花样的产生可能与未知相变的预转变过程有关。

基于FFT的阵列方向图快速计算

分析了等距线阵方向图与傅立叶变换的一致性,用FFT算法进行阵列方向图快速计算。通过严格的数学推导,揭示变换序列与可见空间的关系,讨论了不同单元间距情况下的处理方法。文中结合实例,阐述了FFT算法在阵列方向图计算中的应用技巧,如扫描处理方法、指向分辨精度和边缘数据点估计,并指出用FFT算法计算阵列方向图其运算速度可提高一个数量级以上。

中国温带旱柳物候期对气候变化的时空响应

为了揭示中国温带植物物候随时间变化和植物物候对气候变化响应的空间格局及其生态机制,利用52个站点1986—2005年的旱柳展叶始期、开花始期、果实成熟期、叶变色始期和落叶末期的物候数据,分析其时间序列的线性趋势,并通过建立基于最佳期间日均温的物候时间模型,确定物候发生日期对气温年际变化的响应。在研究的时段内,区域平均旱柳展叶始期、开花始期和果实成熟期的发生日期分别以-4.2 d/10 a、-3.8 d/10 a和-3.3 d/10 a的平均速率显著提前,而区域平均旱柳叶变色始期和落叶末期的发生日期则分别呈不显著推迟和以2.4 d/10 a的平均速率显著推迟的趋势。单站展叶始期、开花始期和果实成熟期发生日期的线性趋势以提前为主,显著提前的站点分别占40%、41%和29%;叶变色始期发生日期呈显著提前和显著推迟趋势的站点数相当,分别占17%和19%;落叶末期发生日期的线性趋势以推迟为主,显著推迟的站点占23%。各站展叶始期、开花始期和果实成熟期发生日期的线性趋势空间序列与相应的最佳期间日均温的线性趋势空间序列之间呈显著负相关,表明一个站点前期气温升高的速率越快,该站这些物候期发生日期提前的速率就越快。在物候期对气温年际变化的响应方面,区域平均春季最佳期间日均温每升高1℃,展叶始期、开花始期和果实成熟期的发生日期分别提前3.08 d、2.83 d和3.54 d;区域平均秋季最佳期间日均温每升高1℃,叶变色始期和落叶末期的发生日期分别推迟1.69 d和2.28 d。单站展叶始期和落叶末期发生日期对气温年际变化的响应表现出在温暖地区的站点比在寒冷地区的站点更为敏感的特点。总体上看,基于日均温的物候时间模型对春、夏季物候期的模拟精度明显高于对秋季物候期的模拟精度。建立了基于最佳期间日均温和日累积降水量的改进秋季物候模型,该模型使旱柳叶变色始期和落叶末期的模拟精度显著提高。由此可见,旱柳叶变色始期和落叶末期的发生日期受到前期气温和降水量的综合影响。

一种基于线性鉴别分析的GIS局部放电模式识别

根据GIS设备绝缘缺陷放电形式和特点,设计了4种典型的GIS缺陷模型,构造了局部放电灰度谱图;针对GIS局部放电及其缺陷特点,提出一种基于局部放电图像的主分量分析-线性鉴别方法,即首先进行主分量分析,将数据从超高维空间降至低维空间,再提取统计不相关的最优鉴别矢量集,采用最小距离分类器进行模式识别,识别结果表明该方法对GIS各类模拟缺陷的正确识别率较高,效果良好.