太平洋混合层厚度(dml)年际异常的初步分析

用太平洋区域30a逐月混合层厚度(d_ml)及浅层海温(T_s)距平资料,分析了20°S以北太平洋区域d_ml年际变率的地理分布和季节变化,得到两个纬向d_ml高变率带,它们分别位于北太平洋(45°N附近)和赤道中、西太平洋。重点分析了赤道太平洋d_ml高变率带,并对其上混合层气候位置、d_ml年际异常与ElNino事件关系及伴随强ElNino事件的d_ml正异常东传等作了初步分析。     

顶点Pk覆盖问题的研究综述

顶点覆盖问题是经典的NP完全问题,在排序、计算机网络等现实生活中有许多的应用.近几年来,许多研究者开始探究它的推广形式——顶点P_k覆盖（VCP_k）问题,即寻找一个顶点子集,从拓扑结构图中删除后使得剩下的顶点导出的子图不包含P_k路,其中P_k是指包含k个顶点的路.本文简单介绍了VCP_k问题的应用背景,归纳了它在近似算法、精确算法、参数化算法3个方面的主要研究进展,并分析了一些主要的方法和技巧.在此基础上,对VCP_k问题及其相关问题的研究前景进行了展望.     

不确定奇异系统的时滞相关鲁棒H∞滤波器设计

为了设计出全阶的滤波器,同时使得滤波误差动态系统是正则的、无脉冲的,并且满足一定的H_∞性能指标,研究了连续奇异系统的全阶H_∞滤波器的设计问题.利用Lyapunov-Krasovskii泛函及二次型的积分不等式方法获得了滤波误差动态系统的H_∞性能时滞相关的判据,给出了奇异系统的鲁棒H_∞滤波器存在的时滞依赖的充分条件.最后的数值例子说明了该方法的有效性.     

具有遗忘时滞的静态神经网络的H∞状态估计

本文研究了具有遗忘时滞的静态神经网络的H_∞状态估计问题.首先降低了时变时滞可微的条件,然后通过构造合适的Lyapunov-Krasovskii泛函,设计保H_∞性能的状态估计器,使得误差系统实现全局渐近稳定.最后,借助Matlab中线性矩阵不等式工具箱进行数值仿真,验证了结论的有效性.     

具有异步控制器的离散马尔可夫跳变Lur'e系统的稳定性和l2增益性能分析

本文研究了一类具有异步控制器的离散马尔可夫Lur''e跳变系统的稳定性及l₂增益性能.通过引入隐马尔可夫模型（HHM）来描述所设计的控制器和原始系统之间出现的异步现象.利用线性矩阵不等式（LMI）方法分析了闭环系统的稳定性和l₂增益性能.然后提出了一个充分条件使得闭环系统随机稳定,并使得从扰动到系统输出的l₂增益达到最小.同时,通过求解给定条件来设计一个由线性状态反馈和扇形有界非线性输出反馈组成的异步控制器.最后,给出了一个数值仿真例子来验证所提方法的有效性.     

一次强降水风暴回波合并前后双偏振特征分析

基于济南S波段双偏振多普勒天气雷达探测数据,结合卫星、探空和地面实况资料,对2020年8月6日发生在山东曲阜一带的强降水风暴合并前后双偏振参量特征和微物理特征进行分析。结果表明:(1)云带之间产生多次合并,合并后风暴加强发展,产生较大的分钟降水量和累计降水量。(2)新生单体最典型的双偏振特征是具有大的Z_DR和CC,以少许液态粒子为主;新生单体迅速发展过程中上升气流强度明显加强,出现明显的K_DP柱和Z_DR柱,液态粒子浓度明显增大并出现偏大的液态粒子。(3)合并后发展的主要特征是,风暴顶高、强回波区顶高和K_DP柱明显增高,-10℃层高度以下,特别是在风暴底层K_DP值明显增大。(4)合并之后风暴发展最典型的微物理特征是,-10℃层高度之下液态雨滴粒子浓度迅速增大,-10℃层高度之上冰晶或霰粒子层的厚度明显增大。发展旺盛的风暴中、低层有丰富的液态水,风暴高层含有丰富的冰相粒子,从而导致风暴产生高强度降水。     

欺骗攻击下一类神经网络的自适应事件触发H∞滤波

本文主要研究了在欺骗攻击下的离散时间神经网络的H_∞滤波器设计问题.考虑到被控系统和滤波器在一个易受外部网络攻击且带宽有限的共享通信网络上进行信息交换,本文提出了自适应事件触发机制来减轻数据传输的通信负担.此外,由于通信网络的开放性和互通互联,通过共享通信网络传输到滤波器的实际输入信息可能会被攻击者注入的虚假信息所改变.在此基础上,利用构造Lyapunov-Krasovskii泛函、线性矩阵不等式等处理技术,本文给出了滤波误差系统渐近稳定的充分条件,并且设计了满足预设性能的H_∞滤波器,最后通过一个仿真实例验证了所提方法的有效性.     

模糊多智能体系统的H∞一致跟踪控制

本文研究非线性多智能体系统在有向拓扑下的领导跟随H_∞一致性问题.首先,提出一种新的多项式模糊建模方法来描述由领导者与跟随者构建的偏差动态系统.然后,设计一致控制协议使跟随者渐近跟踪领导者的轨迹.基于多项式李雅普诺夫函数技术,提出松弛的渐近一致的充分条件并确保存在外界干扰时多智能体系统具有H_∞抑制性能.将导出的条件转化为平方和形式并能够进行数值求解.最后,给出一个实例来验证所提出的一致控制协议的有效性.     

膜基—气体吸收耦合分离混合气中CO2性能评价

在膜基—气体吸收耦合实验装置上,评价了疏水性PP(聚丙烯)微孔膜,活化MDEA(N-甲基二乙醇胺)溶液分离混合气中CO₂传质性能,研究了气液流速、吸收剂和混合气的浓度等因素对总传质系数的影响,采用阻力层关联方程模型预测总传质系数K_ov值。结果表明:活化MDEA溶液能提高总传质系数K_ov值,模型的计算值和实验值符合较好。     

基于负μ传输线的电偶极子和环天线设计

负μ传输线是一种通过串联电容加载来获得等效负磁导率的人工电磁材料,利用其零传播常数的性质,可以设计具有无限大波长且谐振频率与尺寸无关的谐振器,从而实现天线的小型化和宽带化.本文以基于分段线结构的负μ传输线为例,分别设计了具有宽带特性的电偶极子和环天线.测试结果表明长度为107 mm（1.03λ₀@2.9 GHz）的电偶极子可获得的阻抗带宽约为1.4 GHz（2.2~3.6 GHz,48%）,并且该天线在工作带宽内具有稳定的E面方向图.直径为52 mm（0.5λ₀@2.9 GHz）的环天线可获得的阻抗带宽约为1 GHz（2.4~3.4 GHz,34%）,并且环上具有均匀的电流分布,从而具有磁偶极子的辐射特性.测试和仿真结果吻合较好.     

HO x production due to radon decay in air

The HO _x (OH and HO₂) production rate in indoor air caused by radon decay was measured by the chemical amplification technique. The average HO _x production rate was found to be (4.31±0.07)×10⁵ HO _x per Rn decay per second (Bq) within the range of relative humidity from 3.4 to 55.0 percent at 22 °C. This work providedG(HO _x )-value, 7.86±0.13 #/100 eV in air by directly measuring [HO _x ] from radiolysis of water vapor. It is also found that there is no obvious relationship between the HO _x production rate and the relative humidity in this range. Therefore, this work provides both the basic data for the evaluation of radioactive pollution in indoor air as well as a potentially useful way to produce HO _x concentrations in air.     

CLIMATE CHANGE DUE TO GREENHOUSE EFFECTS IN CHINA AS SIMULATED BY A REGIONAL CLIMATE MODEL-PART I:EVALUATION OF THE MODEL SIMULATIONS*

Impacts of greenhouse effects(2×CO₂) on climate change over China as simulated by a regional climate model have been investigated.The model was based on RegCM2 and is nested in one-way mode within a global coupled atmosphere-ocean model(CSIRO R₂₁L₉ AOGCM).Two multi-year simulations,the control run with normal CO₂ concentration and the sensitivity run with doubled CO₂ concentration are conducted. As Part I of the publications,results of control run of the CSIRO,i.e.its simulation of present climate in China,are analyzed briefly.It shows that the model can basically reproduce the surface air temperature and precipitation pattern over China.Therefore,its outputs can be used to drive the regional model. Analysis of control run of RegCM shows that with a high resolution,the model improves the simulations of surface air temperature and precipitation in China as compared to the CSIRO model, especially for the precipitation.The spatial correlation coefficient between simulated and observed annual temperature increased from 0.83 in the CSIRO to 0.92 in the RegCM and for annual precipitation from 0.48 in the CSIRO to 0.65 in the RegCM.A similar improvement in the RegCM compared to the CSIRO was found in all simulated months.The main improvement for surface temperature is that RegCM can simulate the fine scale structure of temperature caused by topography.RegCM greatly improved the spatial distribution of precipitation by eliminating the virtual precipitation center in central China,which was simulated by many other GCMs.The precipitation simulated by RegCM in North and Northwest China is smaller than that by CSIRO, which makes it closer to the observation.     

天顶扫描模式在双偏振天气雷达Z_(dr)系统偏差订正中的应用

双偏振天气雷达Z_(dr)系统偏差是影响雷达数据质量的关键因素,本文利用南京信息工程大学C波段双偏振天气雷达,对90°仰角天顶扫描数据在Z_(dr)系统偏差订正中的应用进行了分析,同时增加90°仰角定点观测模式,讨论并确认了方位旋转关节对Z_(dr)测量结果的影响,在双偏振天气雷达雷达Z_(dr)系统偏差订正中加入了方位旋转关节因素。研究结果表明:选择合适的90°仰角数据,不仅可以对接收双通道不一致造成的Z_(dr)固定系统偏差进行订正,还能够进一步检测由方位旋转关节衰减不同引起的误差;利用90°仰角数据对Z_(dr)的系统偏差进行订正,稳定性和精度较高,满足双偏振天气雷达Z_(dr)精度要求。     

热带太平洋表面水中CO2对El Niño事件响应的数值模拟

文中用一个带生物泵的三维全球海洋碳循环模式模拟了热带太平洋表面水中CO2总量(TCO2)在ElNi     

一次重雾霾天气成因及湿清除特征分析

为了深入了解发生在武汉地区一次重雾霾天气过程的气象条件、污染源和污染物的湿清除特征,本文利用空气质量监测资料、地面观测资料和遥感火点监测资料和实测雨滴谱资料,详细分析了这次过程。结果表明:此次持续10 d的重雾霾天气过程发生在高压天气系统和静风条件下,辐射降温形成的稳定逆温边界层结构有利于污染气溶胶的积累和雾霾的形成和发展,尤其是来自南方持续不断的湿平流使雾霾天气得以长时间持续和发展,整个雾霾天气期间能见度均小于2 km,最低能见度不足50 m。2014年11月23~24日降水过程对此类污染物有明显的清除效果,清除率最高的是颗粒物污染,NO_2、SO_2和CO次之,最差的是O_3,通过与Scott(1982)按平均碰并系数E(E=0.65)得到的清除率和雨强的关系比较,武汉地区稳定性降水对气溶胶的平均碰并系数可取0.25~0.35。     

THE APPROACH TO REMOTE SENSING OF WATER VAPOR BASED ON GPS AND LINEAR REGRESSION Tm IN EASTERN REGION OF CHINA

The approach to remote sensing of water vapor by using global positioning systems(GPS) isdiscussed.In order to retrieve the vertical integrated water vapor(IWV) or the precipitable water(PW),the weighted "mean temperature" of the atmosphere,T_m would be estimated to the specificarea and season.T_m depends on surface temperature,tropospheric temperature profile,and thevertical distribution of water vapor.The surface temperature dependence is borne out by acomparison of T_m and the values of surface temperature T_s using radiosonde profiles of BeijingStation(No.54511) throughout 1992.The analysis of radiosonde profiles spanning a one-yearinterval(1992) from sites in eastern region of China with a latitude range of 20-50°N and alongitude range of 100-130°E yields the coefficients a and b of a linear regression equation T_m=a+bT_s.     

Seasonal variation of particulate organic compounds in atmospheric PM10 in the biggest municipal waste landfill of Algeria

The average composition and seasonal variations of atmospheric organic particulates with respect to n-alkanes, n-alkanoic acid, polycyclic aromatic hydrocarbon (PAHs), and nitrated polycyclic aromatic hydrocarbons (N-PAHs) were determined at the biggest municipal waste landfill in Algeria located in Oued Smar, 13 km east of downtown Algiers. Samplings were carried out from August 2002 to February 2003, and organic compounds adsorbed in air particles having an aerodynamic diameter lower than 10 μm (PM₁₀) were characterized using gas chromatography coupled with mass spectrometric detection (GC/MSD). Total concentrations ranged from 828 to 11,068 ng per cubic meter of air for n-alkanes, from 1714 to 21,710 ng per cubic meter of air for n-alkanoic acids, from 13 to 212 ng per cubic meter of air for PAHs and from 93 to 205 pg per cubic meter of air for N-PAHs. n-Alkanoic acids accounted for 85 and 56% of the total organic composition of the aerosol measured in summer and winter, respectively, were the biggest fraction. The distribution profiles and the diagnostic ratios of some marker compounds allowed to identify the combustion and microbial activity as the major sources of particulate organic pollutants associated with direct emission. The year-time dependence of organic fraction content of aerosol in Oued Smar appeared to be related to average meteorological conditions as well as variability of rate and nature of materials wasted into the landfill.     

RETRIEVING OVER-OCEAN PRECIPITABLE WATER FROM THE SSM/I MEASUREMENTS WITH SEVERAL REGRESSION ALGORITHMS*

A collocated SSM/I and radiosonde measurement data set provided by the NASDA(Japan) was used to retrieve the total precipitable water(PW) over oceans.The retrieval results obtained with several regression algorithms were compared against the radiosonde measurements.It is shown that:(a) the routinely operational algorithm of Alishouse et al.(1990) yields significant underestimation in high PW regime and overestimation in low PW regime;(b) a cubic correction by Colton and Poe(1994) is not sufficient and globally improves slightly the retrieval results;and(c) the regression algorithm with the form of brightness temperature(T_b) function In(280-T_b) gives a little largely scattered retrievals in whole PW range but without considerable over-and underestimates in low and high PW regimes.To improve the estimation of the oceanic precipitable water from the SSM/I measurements,a composite algorithm with different forms of T_b function in low.medium and high PW regimes is proposed and tested.     

北京秋季一次典型大气污染过程多站点分析

多站点多种大气污染物的同步在线观测对深入剖析大气污染的成因和演变机制有重要意义。以龙潭湖、北京325 m塔、双清路和阳坊4监测站点实时NO_x、SO₂、O₃、PM2.5和PM10浓度观测数据为基础,介绍了北京地区2010年10月3～11日发生的一次典型污染过程。不同污染物在污染过程中变化特征不一致,表现为NO_x、SO₂、O₃浓度有明显日变化,而PM浓度升高后一直维持在高值,日变化幅度很小。通过分析不同站点、相同污染物之间的相关性和变异系数发现,4站点间一次污染物NO和SO₂空间浓度差别大,变异系数分别为77%和70%,相关系数低于0.44;而二次污染物NO₂、PM2.5、O₃空间浓度差别较小,变异系数分别为34%、36%和29%,相关系数均超过0.54。结合中尺度气象模式研究发现,该污染过程中,850 hPa高空持续的西南暖平流造成华北地区显著平流逆温,与近地层辐射逆温共同作用,使北京地区混合层高度维持在1200 m以下。低混合层高度和低风速限制了大气垂直和水平扩散,造成北京地区近地层污染物累积,形成重度污染。     

Investigating the Changes in Air Pollutant Emissions over the Beijing-Tianjin-Hebei Region in February from 2014 to 2019 through an Inverse Emission Method

In recent years, China has implemented several measures to improve air quality. The Beijing-Tianjin-Hebei(BTH)region is one area that has suffered from the most serious air pollution in China and has undergone huge changes in air quality in the past few years. How to scientifically assess these change processes remain the key issue in further improving the air quality over this region in the future. To evaluate the changes in major air pollutant emissions over this region, this paper employs ens...