陀螺定向中几个常见问题的应用分析

文章就陀螺定向应用过程中,如何减少定向时间、节省电量、保证定向精度等几个常见问题进行了分析,主要从仪器常数的稳定性、零位改正、粗定向简化几方面着手,通过实验测试,分析了仪器常数的特性、零位改正的规范要求与应用、粗定向简化的方案,并对本文中提出的方法结合工程实际进行验证,结果表明,能够加快作业速度、提高定向效率.     

农业干旱业务化监测研究进展与展望

业务化农业干旱监测系统是农业干旱监测和预测以及农业风险评价和防范的有力工具,为了更好地促进农业干旱业务化监测的发展,系统回顾了基于气象变量、土壤湿度、植被状态和多变量等4类常用干旱指数,详细分析了美国、中国、欧洲和联合国粮食及农业组织等业务化农业干旱监测系统的特征,讨论了业务化农业干旱监测系统中存在的问题：如数据的质量及融合不稳定、综合干旱指数的构建不确定、监测的时间分辨率有待提高、缺乏考虑水文条件以及作物的生长过程等影响的问题。展望了未来农业干旱业务化监测,应从利用多源数据监测干旱、构建综合指标时需考虑区域时空差异及不同指标间的累积性和滞后性、加强机器及深度学习在综合指标构建中的作用、发展日时间尺度监测干旱以应对骤旱事件的发生、强化作物生长过程模型和先进的技术手段在干旱监测中的作用等方面深入发展。     

Evaluating the Efficiency of Typographic Design: Gender and Expertise Variation

Abstract

Although the efficiency of label placement algorithms has been studied extensively, few studies considered the influence of the label designs on the efficiency of map readers. Labels are one of the most important elements on the map as they can provide more information than other symbols can. The design of the labels does have to stress the theme, shape and functionality of the associated objects, which results in a more efficient interpretation of the map content by the user. How the label designs can enhance the map readers’ efficiency (and thus the quality of the maps themselves) is the main objective of this study. A user study was conducted in which the participants were asked to locate a target label on a map. Different label designs were implemented across the trials. The participants’ reactions times were registered to measure their efficiency and statistically analysed using a one-way ANOVA. Two different users’ characteristics were considered: gender and expertise. Related to the size, shape, orientation and texture of the labels, a number of significant differences (P<0·05) and trends were located. Differences in efficiency between males and females, on the one hand, and between novices and experts, on the other hand, were also described statistically. Consequently, recommendations can be formulated regarding the design of labels in order to obtain more efficient maps, keeping in mind the map users’ characteristics.     

LOCAL LABOR MARKETS: THEORIES AND POLICIES IN THE U.S. DURING THE 1970s∗

Local labor market policies of the federal government are critically evaluated with respect to their target efficiency and underlying theoretical assumptions. Policies of the Economic Development Administration are considered to be target inefficient compared to those of the Comprehensive Employment Training Act. Experimental mobility policies of the Department of Labor appear to be have questionable impact locally as opposed to nationally. Some local hybrid programs offer improved place and people targeting.     

中国经济效率的省域空间格局及其提升研究

文章选取资本存量、劳动力、土地、外商投资、邮政电信业务量作为投入变量,选取地区生产总值作为产出变量,分析了2009年中国经济效率的静态空间格局。发现纯技术效率要好于技术效率。在规模报酬不变状态下的技术效率（TEcrs）方面,DEA 有效的省份只有16个;在规模报酬变动状态下的纯技术效率（TEvrs）方面,DEA 有效的省份有18个;从规模效率（SE）上看,DEA 有效的省份也是18个。从中国内陆31个省份的平均技术效率、平均规模效率和规模报酬的情况上看,全国层面和不同空间尺度的区域层面存在差异。文章对各个省份资本、劳动力、土地、外商投资、信息化等存在投入冗余及产出不足的情形进行了分析,研究结果可以为各省政府部门提供参考。     

南京都市圈产业效率演化及空间差异分析

都市圈是具有经济一体化趋势的地域空间组织形式,其内部产业效率状态是城市之间存在紧密联系的基础。本文采用数据包络分析（DEA）方法,对南京都市圈内六市四县以及巢湖市市区的产业效率进行分析和空间刻画,结果表明：南京都市圈内产业效率的市域差异,呈现由“中心式结构”向“双核式结构”的过渡趋势,整体产业效率走向相对均衡发展,其中产业效率呈现“东高西低、南高北低”的状态;南京都市圈整体产业效率演化状态趋于增长,其中第二产业的产业效率演化在整个过程中处于主导地位;南京都市圈内的产业效率与其经济实力存在强正相关,经济实力时空格局与南京都市圈产业效率演变的格局基本一致。     

Comparing expert judgement and numerical criteria for hydrograph evaluation

Abstract

This paper investigates the relationship between expert judgement and numerical criteria when evaluating hydrological model performance by comparing simulated and observed hydrographs. Using a web-based survey, we collected the visual evaluations of 150 experts on a set of high- and low-flow hydrographs. We then compared these answers with results from 60 numerical criteria. Agreement between experts was found to be more frequent in absolute terms (when rating models) than in relative terms (when comparing models), and better for high flows than for low flows. When comparing the set of 150 expert judgements with numerical criteria, we found that most expert judgements were loosely correlated with a numerical criterion, and that the criterion that best reflects expert judgement varies from expert to expert. Overall, we identified two groups of 10 criteria yielding an equivalent match with the expertise of the 150 participants in low and high flows, respectively. A single criterion common to both groups (the Hydrograph Matching Algorithm with mean absolute error) may represent a good indicator for the overall evaluation of models based on hydrographs. We conclude that none of the numerical criteria examined here can fully replace expert judgement when rating hydrographs, and that both relative and absolute evaluations should be based on the judgement of multiple experts.

Editor D. Koutsoyiannis     

Scenarios of global municipal water-use demand projections over the 21st century

Abstract

A comparison study is presented of three methods for evaluating trends in drought frequency: the standardized precipitation index (SPI), the Palmer drought severity index (PDSI), and a new method for estimation of dry spells (DS), which is based on average daily temperature and precipitation, and takes into account the length of a spell. The methods were applied to climate data from 450 stations in the Elbe River basin for the period 1951–2003, as well as data from several stations with longer observed time series. Statistical methods were used to calculate trend lines and evaluate the significance of detected trends. The dry spells estimated with the new method show significant trends in the whole lowland part of the Elbe basin during the last 53 years, and at the 10% level almost everywhere in the German part of the basin excluding mountains and the area around the river mouth. The SPI and PDSI methods also revealed significant trends, but for smaller areas in the lowland. The new DS method provides a useful supplement to other drought indices for the detection of trends in drought frequency. Furthermore, the DS method was able to detect statistically significant trends in areas where the other two methods failed to find significant trends, e.g. in the loess region in the southwest of the German part of the basin, where small insignificant changes in climate can lead to significant changes in water fluxes. This is important, because the loess region is the area within the basin having the highest crop yields. Therefore, additional research has to be done to investigate possible impacts of detected trends on water resources availability, and possible future trends in drought frequency under climate change.     

Modelling catchment inflows into Lake Victoria: uncertainties in rainfall–runoff modelling for the Nzoia River

Abstract

Climate and soil characteristics vary considerably around the Lake Victoria basin resulting in high spatial and temporal variability in catchment inflows. However, data for estimating the inflows are usually sparsely distributed and error-prone. Therefore, modelled estimates of the flows are highly uncertain, which could explain early difficulties in reproducing the lake water balance. The aim of this study was to improve the estimates of catchment flow to Lake Victoria. The WASMOD model was applied to the Nzoia River, one of the major tributaries to Lake Victoria. Uncertainty was assessed within the GLUE framework. During calibration, log-transformation was performed on both simulated and observed flows. The results showed that, despite its simple structure, WASMOD produces acceptable results for the basin. For a Nash-Sutcliffe efficiency (NS) threshold of 0.6, the percentage of observations bracketed by simulations (POBS) was 74%, the average relative interval length (ARIL) was 0.93, and the maximum NS value was 0.865. The residuals were shown to be homoscedastic, normally distributed and nearly independent. When the NS threshold was increased to 0.8, POBS decreased to 54% with an improvement of ARIL to 0.49, highlighting the effect of the subjective choice of likelihood threshold.

Citation Kizza, M., Rodhe, A., Xu, C.-Y. & Ntale, H. K. (2011) Modelling catchment inflows into Lake Victoria: uncertainties in rainfall–runoff modelling for the Nzoia River. Hydrol. Sci. J. 56(7), 1210–1226.     

Growth and survival of Halimione portulacoides stem cuttings in heavy metal contaminated soils

The halophytic shrub Halimione portulacoides demonstrates a high tolerance to heavy metal contamination and a capacity for accumulating metals within its tissues. On the Iberian Peninsula, this species has colonized habitats with high levels of metal pollution. The aim of this study is to analyze the response of H. portulacoides stem cuttings to this pollution. Growth, photosynthesis and metal uptake were examined in H. portulacoides through an experiment in which stem cuttings were replanted in metal-contaminated soil. This condition decreased growth and lowered both photosynthetic rate and stomatal conductance. Reduced photosynthetic performance was largely due to the reduced concentration of photosynthetic pigments. Despite these responses, there was some important evidence suggesting the phytoremediatory potential of Halimione stem cuttings. The results of our study indicate that this salt-marsh shrub may represent a biotool of value in the restoration of polluted areas.