Functional forms in energy demand modeling

In the estimation of demand functions for energy resources, linear, log–linear and translog functional forms are commonly assumed. It has often been questioned whether such functional forms can indeed accurately represent the underlying relationships between the demand for various energy resources and explanatory variables such as energy prices, weather variables, income and other factors. This paper compares linear, log–linear and translog share equation functional forms against a non-parametric function. Bootstrapping methods are used to test the validity of using the three parametric functional forms in models of residential energy demand. Cross-sectional household-level data from the US BLS Consumption Expenditure survey and other government datasets are used. Each of the parametric functional forms tested performs poorly, suggesting that they may be insufficiently flexible to provide valid results in certain applications.     

基于Bootstrap的实测负荷模型参数优选

负荷模型对电力系统的动态仿真及控制起着举足轻重的作用。为使建立的负荷模型具有较好的泛化能力,在Bootstrap原理的基础上,本文充分利用实测负荷数据,提出了负荷模型参数优选的策略:首先利用优化的方法(如遗传算法)辨识单条实测曲线的负荷模型参数,然后利用Bootstrap法估计型各参数的统计特性,最后根据统计特性选择相应的参数值。由于Bootstrap法可将小样本问题转化为大样本问题来估计未知参数的近似分布,因此该策略可充分利用现场实测的小样本数据,客观估计小样本空间下参数的统计特性,达到参数优选的目的。     

改进偏最小二乘回归在电力负荷预测中的应用

多元回归分析是中长期电力负荷预测中的一个重要方法,其中偏最小二乘法因为可以有效解决样本数据偏少以及自变量多重线性的问题而得到采用。探讨了通过Bootstrap方法给偏最小二乘法筛选自变量后进行负荷分析预测的可行性,将计算结果与一般偏最小二乘法及经变量筛选的逐步回归法进行比较。算例表明,应用Bootstrap方法进行参数检验的偏最小二乘方法在变量关系的描述上更简明准确,同时提高了预测精度,具有一定的实用性。     

基于Bootstrap框架的响应式网页设计与实现

为了解决各种移动设备兼容显示网页的问题,以确保良好的用户体验,提出了响应式网页设计技术。研究了web前端开发框架Bootstrap,分析其在响应式网页设计中的作用,并以数字媒体技术专业介绍为背景,设计并构建了基于Bootstrap框架的响应式网站,实现了移动端与PC端网页显示的一致性。     

Using contrails and animated sequences to visualize uncertainty in dynamic sensory profiles obtained from temporal check-all-that-apply (TCATA) data

Approaches for analyzing temporal check-all-that-apply (TCATA) data are further developed and illustrated using data arising from a Syrah wine finish evaluation. Raw and smoothed trajectories are obtained using principal component analysis. Virtual panels are obtained from a partial bootstrap, and the attribute citation proportions are then projected into the solution space to form contrails. Trajectories are overlaid on the contrails, allowing smoothing to be evaluated. Separation between two contrails provides evidence that the trajectories differ. At individual time slices, data concentration ellipses are overlaid on bootstrap scores. Separation of ellipses provides evidence of differences among treatments. Difference trajectories and difference ellipses can also be plotted; if the difference ellipse excludes the origin it indicates a difference between the treatments. Animated sequences summarize changes in product characterization over time in a manner that facilitates review. A glossary of terms introduced in the paper is provided in an appendix.     

Time-varied causality between US partisan conflict shock and crude oil return

To investigate the causality between US partisan conflict shock and crude oil return, this paper utilizes bootstrap full-sample Granger causality and bootstrap rolling window sub-sample Granger causality tests. Although no evidence supports the causal nexus between partisan conflict shock and crude oil return with full sample data, time-varied causality is observed for particular sub-samples. Such difference can be attributed to the parameter non-constancy in the VAR system. In terms of the empirical results, the US partisan conflict shock causes the fluctuations of the crude oil market in 2008–2009 and 2014–2015. However, such influence is temporary. Inversely, the crude oil return causes US partisan shock in 1985–1986, 1991–1994, 1998–2000 and 2012–2013. These findings indicate crude oil market significantly affects political stability of the US, especially during the periods of the Gulf War and OPEC production cut. The empirical results are robust in terms of both sample setting variation and window size selection.     

Bootstrap current fraction scaling for a tokamak reactor design study

We have derived new bootstrap current fraction scalings for systems codes by solving the Hirshman–Sigmar model, which is valid for arbitrary aspect ratios and collision conditions. The bootstrap current density calculation module in the ACCOME code was used with the matrix inversion method without the large aspect ratio assumption. Nine self-consistent MHD equilibria, which cover conventional, advanced and spherical tokamaks with normal or reversed shear, were constructed using numerical calculations in order to compare the bootstrap current fraction values with those of the new model and all six existing models. The Wilson formula successfully predicted the bootstrap current fraction, but it requires current density profile index for the calculation. The new scaling formulas and IPDG accurately estimated the bootstrap current fraction for the normal and weakly reversed shear tokamaks, regardless of the aspect ratio. However, none of the existing models except the Wilson formula can accurately estimate the bootstrap current fraction for the reversed shear tokamaks, which is promising for the advanced tokamak operation mode.     

Statistical methodology for predicting the life of lithium-ion cells via accelerated degradation testing

Statistical models based on data from accelerated aging experiments are used to predict cell life. In this article, we discuss a methodology for estimating the mean cell life with uncertainty bounds that uses both a degradation model (reflecting average cell performance) and an error model (reflecting the measured cell-to-cell variability in performance). Specific forms for the degradation and error models are presented and illustrated with experimental data that were acquired from calendar-life testing of high-power lithium-ion cells as part of the U.S. Department of Energy's (DOEs) Advanced Technology Development program. Monte Carlo simulations, based on the developed models, are used to assess lack-of-fit and develop uncertainty limits for the average cell life. In addition, we discuss the issue of assessing the applicability of degradation models (based on data acquired from cells aged under static conditions) to the degradation of cells aged under more realistic dynamic conditions (e.g., varying temperature).     

积分型全景取样保持电路

本文简要描述了一种具有宽带响应特性的积分型取样保持电路,并对电路设计和测量结果作了介绍。