Strong pulses from pulsar PSR J0034-0721

We present an analysis of strong single pulses from PSR J0034-0721. Our observations were made using the Urumqi 25-m radio telescope at a radio frequency of 1.54GHz. A total of 353 strong pulses were detected during eight hours of observing. The signal-to-noise ratios of the detected pulses range from 5 to 11.5. The peak fluxes of those pulses are 17 to 39 times that of the average pulse peak. The cumulative distribution of the signal-to-noise ratios of these strong pulses has a rough power-law distribution...     

γ-rays from binary system with energetic pulsar and Be star with aspherical wind: PSR B1259−63/SS2883

At least one massive binary system containing an energetic pulsar, PSR B1259−63/SS2883, has been recently detected in the TeV γ-rays by the HESS telescopes. These γ-rays are likely produced by particles accelerated in the vicinity of the pulsar and/or at the pulsar wind shock, in comptonization of soft radiation from the massive star. However, the process of γ-ray production in such systems can be quite complicated due to the anisotropy of the radiation field, complex structure of the pulsar wind termination shock and possible absorption of produced γ-rays which might initiate leptonic cascades. In this paper, we consider in detail all these effects. We calculate the γ-ray light curves and spectra for different geometries of the binary system PSR B1259−63/SS2883 and compare them with the TeV γ-ray observations. We conclude that the leptonic inverse-Compton model, which takes into account the complex structure of the pulsar wind shock due to the aspherical wind of the massive star, can explain the details of the observed γ-ray light curve.     

Optimal filters for the construction of the ensemble pulsar time

An algorithm of the ensemble pulsar time based on the optimal Wiener filtration method has been constructed. This algorithm allows the separation of the contributions to the post-fit pulsar timing residuals of the atomic clock and the pulsar itself. Filters were designed using the cross- and auto-covariance functions of the timing residuals. The method has been applied to the timing data of millisecond pulsars PSR B1855+09 and B1937+21 and allowed the filtering out of the atomic-scale component from the pulsar data. Direct comparison of the terrestrial time TT(BIPM06) and the ensemble pulsar time PT_ens revealed that the fractional instability of TT(BIPM06)−PT_ens is equal to  σ _z = (0.8 ± 1.9) × 10⁻¹⁵  . Based on the  σ _z   statistics of TT(BIPM06)−PT_ens, a new limit of the energy density of the gravitational wave background was calculated to be equal to  Ω_g h ²∼ 3 × 10⁻⁹  .     

兰州市生态系统健康评价及协调性分析

进行区域生态系统健康评价,可以为当地制定生态系统保护政策和措施、生态系统协调和可持续发展提供科学依据。受数据源获取困难等因素制约,从乡（镇、街道）尺度开展的生态系统健康研究尚不多见。本文通过压力-状态-响应模型,选取15个指标因子构建了适宜于乡（镇、街道）尺度的评价指标体系,然后以第一次地理国情普查成果、统计年鉴数据和Landsat8、HJ-CCD、OMI遥感影像为主要数据源,对部分指标使用统计降尺度处理的基础上,以乡（镇、街道）为评价单元,运用熵值法综合评价兰州市生态系统健康状况,并对压力-状态-响应协调度进行分析。研究结果表明：① 生态系统健康整体表现出由城市中心区较差向城市外围区较好的过渡和替换趋势,从乡镇（街道）尺度来看,属于“不健康”、“亚健康”、“健康”、“很健康”的分别有13.5%、28.8%、51.3%、6.2%;② 就协调度而言,有59%的乡（镇、街道）为中度协调区,主要连片分布在城市郊区,其余分布在安宁区的街道,剩余的41%街道为高度协调区和低度协调区,占国土面积的25%,主要分布在城区的街道,零星分布在城市郊区的一些乡镇。     

Evaluation of Agricultural Ecological Security in Hubei Province

With the promotion of agricultural ecological civilization construction in China, agricultural ecological security has received increasing attention. How to ensure agricultural ecological security has become a great concern for many scholars. As an important agricultural province in China, Hubei is of great significance to Chinese food security and agricultural sustainable development. This paper aims to establish an index system of agricultural ecological security and security classification of Hubei via Analytic Hierarchy Process and Pressure-State-Response methods. An evaluation of agricultural ecological security in Hubei, with a base of the national average value in 2015, reveals that the security degree has increased by 0.07566 from 0.90150 in 2005 to 0.97716 in 2015. Results show that agricultural ecological security in Hubei has improved but failed to reach the national average and there is still large space for improvement of the security level, considering a trend of deterioration in some indexes, such as per capita water resources, population density, per unit area pesticide load of farmland, forest coverage, grassland degradation rate and average annual precipitation. Influencing factors, especially population spatial distribution, misconduct in agricultural production, insufficient ability in agricultural natural disaster prevention, deficiency of agro-ecological technology of agricultural ecological security in Hubei are analyzed. For improvement of the degree of agricultural ecological security in Hubei, some countermeasures and suggestions are discussed.     

The possible companions of young radio pulsars

We discuss the formation of pulsars with massive companions in eccentric orbits. We demonstrate that the probability for a non-recycled radio pulsar to have a white dwarf as a companion is comparable to that of having an old neutron star as a companion. Special emphasis is given to PSR B1820−11 and PSR B2303+46. Based on population synthesis calculations we argue that PSR B1820−11 and PSR B2303+46 could very well be accompanied by white dwarfs with mass ≳1.1 M_⊙. For PSR B1820−11, however, we cannot exclude the possibility that its companion is a main-sequence star with a mass between ∼0.7 M_⊙ and ∼5 M_⊙.     

陆海统筹资源环境承载能力评价体系构建

海洋与陆地是全球生态系统不可分割的组成部分.需要陆海统筹资源环境承载能力评价体系的研究.本次选取陆海统筹资源环境承载力评价指标,主要体现在生态保护重要性、农业生产适宜性、城镇建设适宜性、海洋环境影响、社会经济条件和海洋经济发展现状等5个方面.采用PSR模型,把陆地和海洋有效地连接起来,体现了二者之间相互制约,相互促进,...     

基于PSR模型的乌梁素海生态系统健康分区评价

在压力-状态-响应(Pressure-State-Response,PSR)模型的基础上,诊断了内蒙古乌梁素海不同湖区的生态系统健康状态.从湖泊生态环境特征、生态功能和社会环境3个方面筛选出25项诊断指标,在专家打分法的基础上,采用层次分析法确定每项指标的权重.根据湖区生态环境特征差异,将湖泊划分为Ⅰ、Ⅱ和Ⅲ3个不同的区域,分别诊断各个区域的健康状态.结果显示,乌梁素海生态系统综合健康指数在0.3~0.5之间,属于警戒或者较差的状态.Ⅰ、Ⅱ和Ⅲ区域的综合健康指数分别为0.3395、0.3866和0.4494.基于湖泊的生态系统健康存在区位上差异,为恢复湖泊健康提出有针对性的措施.本研究的开展,可为湖泊生态系统恢复和管理政策的制定提供科学依据.     

基于PSR模型的区域生态持续性评价概念框架

区域可持续发展是可持续发展的重要基础, 生态持续性则是实现区域可持续发展的重要前提与基本途径, 但目前仍缺乏普遍认可的生态持续性目标分解方案;而在人类活动对自然生态影响日益显著且不断增大的背景下, 生态系统健康、风险、安全与可持续性评价已成为当前宏观生态学的研究热点, 虽然在各类评价之间普遍存在概念混淆、指标体系雷同等问题。本研究在系统梳理生态持续性相关概念逻辑关联的基础上, 将区域视为人类自然-经济复合生态系统, 强调人类活动的主导性, 基于“压力-状态-响应(PSR)”模型, 从生态胁迫、生态系统健康和生态可持续能力3 方面构建了一个具有鲜明生态意义的区域生态持续性评价概念模型, 并对评价模型、评价指标筛选及其阈值与权重展开了深入探讨。研究认为:系统工程的综合评价法是区域生态持续性评价的基本方法;不存在绝对的评价标准, 区域生态持续性评价的终极目标, 不在于静态的评价某时某地人类-自然复合生态系统可持续与否, 而在于定量表征时空尺度上系统可持续性的动态变化与空间分异。