旱情评估指标研究简介及探讨

干旱灾害是我国发生最为频繁、影响范围较大,并造成严重危害的一种气象灾害。由于干旱自身的复杂性及对社会影响的广泛性,干旱指标的确定和分析对干旱的监测及评估有重要的意义,同时也为全球变化中的气候一植被关系研究提供方法和依据。将干旱指标从气象、水文、农业和社会经济4方面进行综述,介绍了国内外干旱指标研究现状及最新动态,并指出其优势和不足,以此提出今后干旱指标研究重点与展望。     

Analysing the extent (size and shape) of Lake Basaka expansion (Main Ethiopian Rift Valley) using remote sensing and GIS

This study attempted to estimate the extent of the expansion of the area of Lake Basaka over the past 50 years (1960 to 2010), using LANDSAT images, field observations, local information and topographic maps. The analysis revealed that the lake has exhibited a dramatic expansion over the past five decades. An increase in the lake water level by 7.6 m over this period resulted in flooding about 45.8 km² of surrounding areas and an incremental lake volume of about 280 Mm³. About 70% of the lake expansion was observed in the period between the 1970s and 1990s. This phenomenon coincides with the periods of remarkable land use/cover changes in the region. Furthermore, the beginning of the lake expansion coincided with the introduction of irrigated agriculture in the region, and construction of Koka Dam in the mid‐1960s in the upper Awash River Basin. This study suggests that the observed expansion trend, if it continues unabated, could result in certain socio‐economic and environmental consequences in the region in particular, and to Ethiopia in general. Groundwater inundation or salty water intrusion, for example, might occur in the area in the near future, thereby affecting the sustainability of regional irrigated agriculture. The lake has the potential to inundate the surrounding region (Matahara Sugar Estate; towns of Fantalle and Matahara) and might connect with the Awash River during the next 10–15 years. This would affect downstream irrigation developments in the Awash Basin and the livelihoods of people that depend on the basin’s water resources. The overall findings of this study emphasize the need to adopt mitigation measures before the lake expansion results in irreversible damage to the region or the basin.     

SELECTING HYDROLOGIC INDICES FOR THE PRAIRIE PROVINCES

The large and accumulating body of evidence for both the controlling effect of the flow regime on river ecology and for the dependence of river health on the natural flow regime has led to the increasing use of hydrologic indices in instream flow studies. The myriad of collinear hydrologic indices present a daunting challenge to water managers trying to select a manageable number of indices for use in a hydrology‐based environmental flow framework. In this study, a large number of hydrologic indices were calculated from gauging sites in the prairie provinces of Canada. Principal component analysis (PCA) and two rank‐based non‐parametric techniques are compared in their ability to select a small number of statistically informative indices. Despite the data being skewed and far from normal, PCA and the non‐parametric technique called BioEnv + stepwise (BEST) both led to similar interpretations and could identify a small number of indices that capture a majority of the statistical variability. BEST selected indices more evenly from among conceptual categories of flow than PCA. Copyright © 2011 John Wiley & Sons, Ltd.     

基于DFT与量子拓扑学的氯代二苯并呋喃QSPR研究

为了研究多氯代二苯并呋喃（PCDFs）在云杉针叶和飞灰表面的光解半衰期（t1／2）与其结构的定量关系,本文应用密度泛函理论（DFT）,在B3LYP／6—31＋G（d）基组上优化和振动分析计算了48种PCDFs的分子空间几何结构,得到其各原子之间空间拓扑距离,并建立拓扑空间距离矩阵．结合分子中各原子的支化度,应用原子平衡电负性对分子图进行着色修饰,得到量子拓扑指数XP1、XP2．采用偏最小二乘回归法（PLS）对48种PCDFs在云杉针叶和飞灰表面的t1/2进行模拟分析,分别得到2定量结构一性质相关（QSPR）模型,并用这种模型对t1/2进行预测,结果表明预测结果和实验值吻合较好．同时对QSPR拓扑模型采用留一检验法（LOO）进行测试,测试结果显示模型具有良好稳定性和较强的预测能力．     

Spatial and temporal distributions of Dreissena spp. veligers in Lake Huron: Does calcium limit settling success?

The larval stage of invasive Dreissena spp. mussels (i.e., veligers) are understudied despite their seasonal numerical dominance among plankton. We report the spring and summer veliger densities and size structure across the main basin, North Channel, and Georgian Bay of Lake Huron, and seek to explain spatiotemporal variation. Monthly sampling was conducted at 9 transects and up to 3 sites per transect from spring through summer 2017. Veliger densities peaked in June and July, and we found comparable densities and biomasses of veligers between basins, despite differences in density of juvenile and adult mussels across these regions. Using a generalized additive model to explain variations in veliger density, we found that temperature, chlorophyll a, and nitrates/nitrites were most important. We generated an index of veliger attrition based on size distributions that revealed a higher rate of attrition in the North Channel than the rest of the lake. A logistic model indicated a threshold calcium concentration of around 22 mg/L was necessary for veligers to survive to larger sizes and recruit to their juvenile and benthic adult life stages. Improved understanding of factors that regulate the production and survival of Dreissena veligers could improve the ability of managers to assess future invasion threats as well as explore potential control options.     

Comparison between required clothing insulation and that actually worn by workers exposed to artificial cold

Required Clothing Insulation (IREQ) is a new thermal index submitted to the International Organisation for Standardisation (ISO) for discussion. It is designed to prevent general body cooling and is based on an analysis of heat exchanges. The thermal clothing insulation actually worn (lcl) is estimated using a new method, also submitted to ISO.

IREQ of 54 workers exposed to artificial cold (air temperature between −30° C and +10° C) was compared with lcl actually worn by these workers. The results of the present study show that, on average, the workers choose accurately lcl they need if their IREQ is below and up to 1·5 clo. Moreover, these workers prefer to wear garments which provide them with thermal comfort. If IREQ of workers is higher than 1·5–2 clo (i e, workers exposed to −20° C), it is difficult for them to increase their thermal insulation with additional garments. Although their lcl is not sufficient, there is no risk of gradual body cooling because of their continuous time exposure (CTE) which is shorter than the calculated Duration Limited Exposure (DLE). On the other hand, Wind Chill Index (WCI), which is proposed to prevent local cooling, is better adapted to prevent cold injuries than physiological thermal strain; for example, impairment of manual dexterity cannot be prevented with this index.     

气相色谱程序升温和等温保留指数的关系

通过对７种物质在不同程升速率下的程升保留指数及各温度下的特温保留指数的测定,发现程序升温的流出温度与相应的等温温度之差与程升速率有关,并得到ＰＥＧ－２０Ｍ极性交联毛细管色谱柱上二者的关系曲线,该曲线可用于程序升温保留指数的预测。方法简便,结果准确。     

A novel collapse prediction index for voltage stability analysis and contingency ranking in power systems

Voltage instability is a serious phenomenon that can occur in a power system because of critical or stressed conditions. To prevent voltage collapse caused by such instability, accurate voltage collapse prediction is necessary for power system planning and operation. This paper proposes a novel collapse prediction index (NCPI) to assess the voltage stability conditions of the power system and the critical conditions of lines. The effectiveness and applicability of the proposed index are investigated on the IEEE 30-bus and IEEE 118-bus systems and compared with the well-known existing indices (Lmn, FVSI, LQP, NLSI, and VSLI) under several power system operations to validate its practicability and versatility. The study also presents the sensitivity assumptions of existing indices and analyzes their impact on voltage collapse prediction. The application results under intensive case studies prove that the proposed index NCPI adapts to several operating power conditions. The results show the superiority of the proposed index in accurately estimating the maximum load-ability and predicting the critical lines, weak buses, and weak areas in medium and large networks during various power load operations and contingencies. A line interruption or generation unit outage in a power system can also lead to voltage collapse, and this is a contingency in the power system. Line and generation unit outage contingencies are examined to identify the lines and generators that significantly impact system stability in the event of an outage. The contingencies are also ranked to identify the most severe outages that significantly cause voltage collapse because of the outage of line or generator.     

Estimations of Chlorophyll Content from Vegetation Indicesby Using PROSPECT and DART

With the aid of a well known leaf optical model PROSPECT and a canopy scale model DART (Discrete Anisotropic Radiative Transfer),sensitivities between chlorophyll content and six different vegetation indices were investigated by simulating eucalyptus,one of a dominant fast growing tree in China,as an example.Vegetation indices used here include Normalized Difference Vegetation Index (NDVI),Structure Insensitive Pigment Index (SIPI),Colouration Index (COI),Simple Ratio Index (SR),Cater Index (CAI),and Red edge Position Linear Interpolation (REP_Li).Results indicate that at the leaf scale,COI and SIPI are sensitive to the LCC (Leaf Chlorophyll Content)as the Chlorophyll Content changes.Meanwhile,no obvious saturation phenomenon is observed for these two indices compared to other indices.Further investigations show that all these vegetation indices are incapable of estimating LCC at the canopy scale,due to significant influences from LAI(Leaf Area Index).Nevertheless,it suggests that SIPI and COI can be applied to estimate the CCC (Canopy Chlorophyll Content).     

Evaluating Uncertainty in Physical Habitat Modelling in a High‐Gradient Mountain Stream

Predictions of habitat‐based assessment methods that are used to determine instream flow requirements for aquatic biota are uncertain, but instream flow practitioners and managers often ignore those uncertainties. Two commonly recognized uncertainties arise from (i) estimating the way in which physical habitat within a river changes with discharge and (ii) the suitability of certain types of physical habitat for organisms. We explored how these sources of uncertainty affect confidence in the results of the British Columbia Instream Flow Methodology (BCIFM), which is a commonly used transect‐based habitat assessment tool for small‐scale water diversions. We calculated the chance of different magnitudes of habitat loss resulting from water diversion using a high‐gradient reach of the North Alouette River, BC, as a case study. We found that uncertainty in habitat suitability indices for juvenile rainbow trout generally dominated uncertainty in the results of the BCIFM when large (>15) numbers of transects were used. In contrast, with small numbers of transects, variation in physical habitat among sampled transects was the major source of uncertainty in the results of the BCIFM. Presentations of results of the BCIFM in terms of probabilities of different amounts of habitat loss for a given flow can help managers prescribe instream flow requirements based on their risk tolerance for fish habitat loss. Copyright © 2015 John Wiley & Sons, Ltd.