Impacts of particulate matter on Gulf of Mexico tropical cyclones

This research analyzes the relationship between tropical cyclones and fine particulate matter (PM_2.5) for landfalling Atlantic tropical cyclones from 2000 to 2015. Daily mean PM₂.₅ concentrations were collected from the United States Environmental Protection Agency. Tropical cyclone data were acquired from Tropical Prediction Center Best Track Reanalysis in Unisys weather. GRIdded Binary (GRIB formatted) data were downloaded from the Data Support Section of the Computational and Information Systems Laboratory at the National Center for Atmospheric Research (NCAR). Tracks of tropical cyclones were overlaid with the interpolated daily mean PM₂.₅ concentration value. Results suggest that, in general, tracks are distant from areas with the largest PM₂.₅ concentrations. To examine the cause-effect nature of this relationship, simulation using the Weather Research and Forecasting (WRF) model suggests that the intensity of Hurricane Lili was weakened only after passing the most PM₂.₅-polluted area in Louisiana. This result suggests that aerosol loading may weaken the intensity of tropical cyclones, at least in some cases.     

特大城市空间形态差异对交通网络效率的影响

以交通网络出行迂回作为交通网络效率分析的切入点,选取形状指数、紧凑度作为空间形态分析指标,对特大城市空间形态布局进行类型划分,并挖掘各城市交通网络效率空间分布差异特征,基于多元回归模型剖析中国各特大城市空间形态布局与交通网络效率之间的影响关系。研究表明：① 5种类型城市交通效率高低分布差异明显,紧凑圆形城市边缘区交通网络效率较低,而非紧凑带形交通效率低的区域多分布于城市核心区,紧凑方形城市交通网络效率高地区分布较为集中,而非紧凑方形交通效率低的地区分布较为分散,紧凑带形城市面积越小则交通效率越高。② 就城市空间布局与交通网络效率影响关系而言,随着城市形状指数的增大,城市交通迂回值未进一步增大,说明城市形态布局接近圆形均匀分布时,其城市交通网络效率较高;随着城市紧凑度值的增加,城市交通迂回程度值亦不断增加,说明城市形态布局程度越紧密,反而其交通网络效率越低,当城市形态布局紧密程度适中时,交通网络效率水平较高。     

小型水下运载器快速上浮导弹发射过程扰动分析

区别于传统潜艇发射导弹,小型水下运载器由于尺寸小、重量轻、上浮速度快,导弹发射过程对其动力学特性具有重要影响。针对小型快速上浮运载器,对上浮过程、发射过程及开盖过程扰动进行建模,并对典型上浮发射导弹过程进行仿真分析。结果表明,开盖及发射过程对运载器弹道及姿态的扰动较小,而对上浮速度影响较大,发射后运载器控制效率显著下降。     

北斗剖面浮标数据服务系统设计与业务运行

北斗剖面浮标数据服务系统主要由北斗剖面浮标数据自动接收/监视子系统和北斗剖面浮标数据解码、处理及分发共享子系统组成,具备自动、批量、业务化接收国产北斗剖面浮标数据,以及业务化处理和分发浮标数据的能力,为我国主导建设南海或“21 世纪海上丝绸之路”Argo 区域海洋观测网提供了关键技术保障。催生的中国北斗剖面浮标数据服务中心,也为北斗剖面浮标走出国门、参与国际竞争奠定了坚实基础,成为世界上 3 个有能力为全球 Argo 实时海洋观测网提供剖面浮标观测数据服务的国家平台之一。     

威海南部近岸泥质区晚更新世以来的重矿物组合特征及对物源的指示

对威海南部近岸泥质区WHZK01孔（孔深25.1 m）岩心开展重矿物分析,结果表明,WHZK01孔主要以普通角闪石（22.1%）、磁铁矿（20.0%）和绿帘石（17.7%）为主,晚更新世以来自下而上可分为3个矿物组合带。氧同位素3期晚期河流相沉积（DU3）主要矿物组合为普通角闪石-绿帘石。末次冰后期河漫滩-河口湾相沉积（DU2）主要矿物组合为普通角闪石-绿帘石-钛铁矿-褐铁矿。全新世滨-浅海相沉积（DU1）主要矿物组合为磁铁矿-绿帘石-片状矿物-自生黄铁矿。重矿物物源判别表明,DU3和DU2层沉积物主要来自山东半岛南部沿岸河流输入。DU1层沉积物主要来自沿岸流输运的大量黄河细粒物质,沿岸河流物质和岛屿侵蚀物也有少量贡献。     

饥饿胁迫对大黄鱼激素敏感性脂肪酶和乙酰辅酶A羧化酶mRNA表达及酶活性的影响

激素敏感性脂肪酶（hormone sensitive lipase,HSL）和乙酰辅酶A羧化酶（acetyl-CoA carboxylase,ACC）是脂代谢的关键酶,肌肉和肝脏是鱼类脂代谢的主要场所。为研究饥饿过程中这两种酶的作用,本实验采用实时荧光定量PCR技术以及ELISA技术检测了在35 d饥饿过程中这两种酶在大黄鱼肌肉和肝组织中mRNA表达水平和酶活性的变化。结果显示,饥饿胁迫显著降低大黄鱼肌肉和肝组织中脂肪含量,以及脂肪合成关键酶ACC mRNA表达水平（P<0.05）;显著提高脂肪分解关键酶HSL mRNA表达水平（P<0.05）。饥饿胁迫对肌肉和肝组织中HSL和ACC酶活性均有显著影响（P<0.05）,肌肉和肝组织HSL （相关系数r分别为0.598 2和0.539 6）以及肌肉组织ACC酶活性（r=0.677 7）与对应mRNA表达水平呈中度正相关（0.5 < r < 0.8）,但ACC酶活性在肝组织与其对应的mRNA表达量呈负相关（r=-0.374 0）,提示饥饿胁迫对大黄鱼HSL和ACC的表达存在翻译前和翻译后两种水平的调控。本研究结果可为研究饥饿胁迫对大黄鱼脂类代谢分子层面的影响机制提供依据。     

基于分数阶傅里叶变换的水下目标速度估计

在高斯白噪声背景下,匹配滤波器作为线性调频信号的最优检测器,在水声信号处理中被广泛应用。 当发射信号为线性调频信号时,由水下目标径向速度引起的多普勒频移会造成回波和样本之间失配, 使匹配滤波器的检测性能下降,增加了目标速度估计的难度。 利用分数阶傅里叶变换对于线性调频信号的聚焦特性,提出了应用分数阶傅里叶变换的水下运动目标线性调频回波检测算法,完成对目标速度的估计, 推导目标运动速度与分数阶傅里叶变换阶数之间的关系,并对测量结果进行误差分析。 仿真测试表明,该算法可有效地估计混响背景下的目标径向速度,且具有良好的估计性能。     

Gravitational Waves and Gravitational-wave Sourcestwo

The recent discovery of gravitational-wave burst GW150914 marks the coming of a new era of gravitational-wave astronomy, which provides a new window to study the physics of strong gravitational field, extremely massive stars, extremely high energy processes, and extremely early universe. In this article, we introduce the basic characters of gravitational waves in the Einstein's general relativity, their observational effects and main generation mechanisms, including the rotation of neutron stars, evolution of binary systems, and spontaneous generation in the inflation universe. Different sources produce the gravitational waves at quite different frequencies, which can be detected by different methods. In the lowest frequency range (f < 10^?15 Hz), the detection is mainly dependent of the observation of B-mode polarization of cosmic microwave background radiation. In the middle frequency range (10^?9 < f < 10^?6 Hz), the gravitational waves are detected by analyzing the timing residuals of millisecond pulsars. And in the high frequency range (10 ? 4 < f < 10⁴ Hz), they can be detected by the space-based and ground-based laser interferometers. In particular, we focus on the main features, detection methods, detection status, and the future prospects for several important sources, including the continuous sources (e.g., the spinning neutron stars, and stable binary systems), the burst sources (e.g., the supernovae, and the merge of binary system), and the stochastic backgrounds generated by the astrophysical and cosmological process. In addition, we forecast the potential breakthroughs in gravitational-wave astronomy in the near future, and the Chinese projects which might involve in these discoveries.     

Quantifying the vertical distribution pattern of land-use conversion in the loess hilly region of northern Shaanxi Province 1995–2015

Journal of Geographical Sciences - The mountainous and hilly region plays an important role in ecological safety and production in China. However, recent studies have poorly characterized the...     

Multi-dimensional expansion of urban space through the lens of land use: The case study of Nanjing City,China

Journal of Geographical Sciences - The study of multi-dimensional expansion of urban space (MEUS) addresses the laws of urban spatial expansion from all directions and angles. Using Nanjing as an...