Using Complex Surveys to Estimate the L1‐Median of a Functional Variable: Application to Electricity Load Curves

Mean profiles are widely used as indicators of the electricity consumption habits of customers. Currently, in Électricité De France (EDF), class load profiles are estimated using point‐wise mean profiles. Unfortunately, it is well known that the mean is highly sensitive to the presence of outliers, such as one or more consumers with unusually high‐levels of consumption. In this paper, we propose an alternative to the mean profile: the L ₁ ‐ median profile which is more robust. When dealing with large data sets of functional data (load curves for example), survey sampling approaches are useful for estimating the median profile avoiding storing the whole data. We propose here several sampling strategies and estimators to estimate the median trajectory. A comparison between them is illustrated by means of a test population. We develop a stratification based on the linearized variable which substantially improves the accuracy of the estimator compared to simple random sampling without replacement. We suggest also an improved estimator that takes into account auxiliary information. Some potential areas for future research are also highlighted.     

THE VALUE OF TIGER SHARK DIVING WITHIN THE ALIWAL SHOAL MARINE PROTECTED AREA: A TRAVEL COST ANALYSIS

Using on‐site survey data collected via the administration of a questionnaire to 197 respondents during the period stretching from January 2007 to December 2007 from the Aliwal Shoal Marine Protected Area, this study estimates and compares an ordinary least squares and two Poisson count data models of recreational tiger shark diving demand. The Poisson model corrected for endogenous stratification and truncation provided the best results. It was concluded that in 2007, the consumer surplus per person per tiger shark dive was R1,136, and the total consumer surplus per annum was R2,080,925.     

流动人口的社会分层与居住质量——基于上海市长宁区“六普”数据的分析

有关流动人口的分层研究以往大多集中于制度性因素层面(户籍制度),或者从职业、收入等非制度性因素层面进行区分。从居住角度来研究流动人口的社会分层问题并不多见。利用上海市长宁区第六次人口普查数据作了分析研究。在流动人口中,住房质量的好坏、是否拥有产权不再是精英阶层的特权,相反,精英阶层和非精英阶层内部出现分化,非精英阶层中的商业服务人员无论在产权的拥有上,还是住房质量上都表现出明显的优势,而精英阶层中的专业人员在住房质量上也较为突出,但在住房面积上,职业分层并未对住房面积的大小产生影响。     

农民工城镇化意愿分层:代际与婚姻的视角

从农民工城镇化意愿的分层表现入手,探讨婚姻状况对城镇化意愿代际差异形成的贡献。基于经济理性假设构建农民工城镇化分层决策模型,并建立多个有序logistic模型分析城镇化意愿影响因素。实证分析结果证实了两个假说:一是已婚农民工城镇化决策更符合经济理性;二是城镇中对农民工有利的社会福利制度形成城镇化意愿的制度性拉力,而农村中对农民有利的社会福利制度形成城镇化意愿的制度性阻力,城乡社会制度共同影响农民工城镇化意愿的分层决策。     

2008年广东“龙舟水”特点及诊断分析

文章对2008年5月28日至6月18日,广东省出现持续时间长、范围大、强度高的大暴雨降水过程进行分析。分析结果表明,形成这次＂龙舟水＂过程的原因如下：在欧亚中高纬度维持两槽一脊稳定的大环流形势,为暴雨的持续提供了冷空气,副高较弱位置偏东、偏南,暴雨持续期副高略有加强,使华南沿海地区暖湿气流加强;南支槽活跃,每次强降水过程均与西风槽、高空急流和低层切变线的南压过程配合;水汽源于孟加拉湾和南海且以孟加拉湾为主,水汽的辐合主要发生在华南沿海;华南沿海辐合上升为持续性＂龙舟水＂的产生提供了稳定的上升运动背景且主要出现在层结不稳定的条件下。     

分层教学在工厂电气控制设备课程中的尝试

分层教学思想旨在课堂教学中面向全体学生，促使人人成功。分层教学指协调教学目标和要求，将教学要求置于各层次学生的最近发展区之中，同时调动学生学习可能性中的易变因素，使教学要求与学生的学习可能性相互适应。通过实施分层授课、分层训练、分层辅导、分层评价，以达到各类学生接受效应、共振效应。使各类学生的素质达到分层发展的目的。     

Stratification,diel and seasonal energy transfers in Malilangwe Reservoir in the south‐eastern lowveld of Zimbabwe

This study provides a 9‐month record of Malilangwe Reservoir stratification and diel and seasonal energy transfers between February and October 2011. The reservoir was not strongly stratified during the hot‐wet season (February and March), exhibiting low dissolved oxygen concentrations of <2 mg DO L^?1 in the bottom layers (<6 m depth). During the cool‐dry season, when both the air temperature and solar radiation input decreased, the water temperatures in the epilimnion and across the thermocline decreased, and the water column was very weakly stratified. In this state, the reservoir could easily be mixed, even by light winds, resulting in overturning, thereby giving the bottom water an opportunity to become aerated, as observed during the cool‐dry season. The stability was greatest when the water level was high (during midday), while it was considerably lower during the predawn hours. The calculated annual Birgean heat budget for the reservoir was 110 MJ m^?2 year^?1 for February to October 2011. The diurnal Birgean heat budget was consistently associated with heat loss over a 24 hour period in all seasons, mostly between 0400 and 1000 h. Spearman's correlation suggests that the DO was significantly correlated with stability for the three study months (February r = 0.69, P < 0.05; June r = ?0.76, P < 0.001; October r = 0.96, P < 0.001). The results of this study suggests that warming temperatures (warmer months or seasons) will result in high Birgean heat budgets, which could potentially trigger some important changes in plankton population dynamics in small reservoir, with severe water quality implications. The nutrient concentrations varied throughout the seasons.     

Modelling approach for characterizing thermal stratification and assessing water quality for a large tropical reservoir

The dynamics of water temperature, dissolved oxygen and total dissolved solids concentrations in Aguamilpa Reservoir was analysed by considering horizontal and water column variations. The reservoir model, CE‐QUAL‐W2, was used to simulate the temporal variations calibrated with data gathered every 2 months from June 2008 to June 2009. Temperature depth profiles indicated a typical asymmetry of reservoirs exhibiting a large stratification in the lower part near the dam. Dissolved oxygen concentration profiles exhibited some degree of anoxia in the bottom water during the rainy season (May through October). This is most likely due to decomposition vegetation and organic matter via soil erosion and run‐off from the basin accumulating at the bottom of the reservoir. The reservoir stratification is clearly seasonal, occurring during the rainy season, especially in the lowest reservoir zones. The CE‐QUAL‐W2 model results provided a comprehensive understanding of the temporal behaviour of the study variables during the modelling study period. Application of this water quality model is directed to water resource managers to help them better understand the dynamics of physico‐chemical processes, and how they vary temporally and spatially in the reservoir, and to propose the best management practices for preserving or improving the water quality of the system.     

THRESHOLD FLOWS FOR THE BREAKDOWN OF SEASONALLY PERSISTENT THERMAL STRATIFICATION: SHOALHAVEN RIVER BELOW TALLOWA DAM,NEW SOUTH WALES,AUSTRALIA

Reduced mixing of deep pools attributable to river regulation and downstream flow suppression can lead to an increase in the magnitude, frequency and duration of thermal stratification in riverine pools over summer. This study monitored hourly temperature profiles with five thermistor loggers in a 15 m deep natural pool over 12 months from May 2005. Detailed bathymetric and topographic survey data and HEC‐RAS hydraulic modelling of layer Richardson numbers were used to extend thermistor observations of flow‐related stratification breakdown in this single deep pool to a 20 km long pool‐riffle dominated river reach below the dam. Reach‐wide breakdown of persistent thermal stratification in deep pools over spring and summer was likely to be achieved by a flow rate of 3000 ML day^?1. This flow rate approximates the long‐term mean annual natural flow (2860 ML day^?1) and the 16th flow duration percentile (mean daily flows equalled or exceeded for 16% of time), indicating that thermal stratification of the deepest pools in the Shoalhaven River is a common, natural phenomenon not solely attributable to river regulation. Should reasonably consistent hydraulic geometry relationships exist between low salinity rivers in similar climatic, hydrologic and geomorphic settings, then we suggest that the mean annual natural flow is likely to achieve widespread breakdown of thermal stratification across lengthy reaches of similar pool‐riffle sequence rivers elsewhere. Hourly mean wind speeds of up to 65 km h^?1 recorded at an automated weather station 25 km from the study site were found to suppress of the degree of thermal stratification in the study pool but did not achieve deep mixing of persistent seasonal thermoclines. Large, rapid and sustained air temperature decreases associated with the passage of cold fronts across southeastern Australia in summer were found to be more effective than wind and achieved mixing to depths of at least 4.2 m. Copyright © 2011 John Wiley & Sons, Ltd.