The generation of multidimensional autoregressive series by the herringbone method

The generation of isotropic artificial series in two or three dimensions by the autoregressive process is of considerable interest for the purpose of modeling environmental properties such as ore grade or reservoir porosity. The relations needed to produce bilateral symmetry using the one-sided autoregressive recursion equations have been attained on the square net and on the isometric lattice by an alternation procedure. In the case of the square net, the one-sided autoregressive (AR) process is alternated between the two diagonals of the net, while in three dimensions, the alternation takes place among the four body diagonals of the isometric cell.     

关于一类时变大系统的平稳振荡

本文应用大系统的分解方法以及一个推广的不等式,研究了一类线性时变大系统的平稳振荡问题,得到了一个新的、简洁的结果,并给出了应用实例。     

1949年前中国的两个地震研究系统

叙述了１９４９年前中国从事地震研究工作的２个系统。主要介绍了在蒋丙燃和竺可桢２位先生先后领导下由王应伟和金咏深等所做的工作。着重介绍了《近世地震学》和这一论著的主要观点。第２个是地质系统，介绍了翁文灏先生以及他在《锥指集》中对地震发生和预测方面的各种论点。     

A general Bayesian framework for calibrating and evaluating stochastic models of annual multi-site hydrological data

Multi-site simulation of hydrological data are required for drought risk assessment of large multi-reservoir water supply systems. In this paper, a general Bayesian framework is presented for the calibration and evaluation of multi-site hydrological data at annual timescales. Models included within this framework are the hidden Markov model (HMM) and the widely used lag-1 autoregressive (AR(1)) model. These models are extended by the inclusion of a Box–Cox transformation and a spatial correlation function in a multi-site setting. Parameter uncertainty is evaluated using Markov chain Monte Carlo techniques. Models are evaluated by their ability to reproduce a range of important extreme statistics and compared using Bayesian model selection techniques which evaluate model probabilities. The case study, using multi-site annual rainfall data situated within catchments which contribute to Sydney’s main water supply, provided the following results: Firstly, in terms of model probabilities and diagnostics, the inclusion of the Box–Cox transformation was preferred. Secondly the AR(1) and HMM performed similarly, while some other proposed AR(1)/HMM models with regionally pooled parameters had greater posterior probability than these two models. The practical significance of parameter and model uncertainty was illustrated using a case study involving drought security analysis for urban water supply. It was shown that ignoring parameter uncertainty resulted in a significant overestimate of reservoir yield and an underestimation of system vulnerability to severe drought.     

Stochastic differential dynamic programming for multi-reservoir system control

: As with all dynamic programming formulations, differential dynamic programming (DDP) successfully exploits the sequential decision structure of multi-reservoir optimization problems, overcomes difficulties with the nonconvexity of energy production functions for hydropower systems, and provides optimal feedback release policies. DDP is particularly well suited to optimizing large-scale multi-reservoir systems due to its relative insensitivity to state-space dimensionality. This advantage of DDP encourages expansion of the state vector to include additional multi-lag hydrologic information and/or future inflow forecasts in developing optimal reservoir release policies. Unfortunately, attempts at extending DDP to the stochastic case have not been entirely successful. A modified stochastic DDP algorithm is presented which overcomes difficulties in previous formulations. Application of the algorithm to a four-reservoir hydropower system demonstrates its capabilities as an efficient approach to solving stochastic multi-reservoir optimization problems. The algorithm is also applied to a single reservoir problem with inclusion of multi-lag hydrologic information in the state vector. Results provide evidence of significant benefits in direct inclusion of expanded hydrologic state information in optimal feedback release policies.     

Spatial simulation of geologic variables

Analytical formulation of a general simulation model for generation of anisotropic as well as isotropic synthetic patterns in one, two, or three dimensions is proposed. It has significance for the purpose of modeling geologic properties such as ore grades, reservoir porosity, mineral distribution, fracture spacings, aperture, orientations, etc. General procedures for such a simulation by the autoregressive process are given for model parameters estimation and synthetic pattern generation. The model works on the square net basis and generates sequential patterns first along any desired direction for unidimensional simulation and then two-dimensional patterns are constructed with reference to two orthogonal unidimensional sequences. Applications to synthetic two-dimensional pattern are shown for isotropic cases with different model parameters. The extension of the model to three-dimensional space is readily available.     

Hidden negative spatial autocorrelation

Mostly lip service treatments of negative spatial autocorrelation (NSA) appear in the literature, although spatial scientists confront it in practice. NSA was detected serendipitously in recalcitrant empirical analyses containing a sizeable amount of global positive spatial autocorrelation (PSA) unaccounted for by standard spatial statistical models, and labeled hidden because conventional spatial statistical tools detected only PSA while giving absolutely not hint of NSA existing. The meaning of this phenomenon is explored empirically, with findings including: a better understanding of NSA, spatial filter model construction guidelines, effective illustrations of NSA, and how hidden NSA furnishes a diagnostic for model misspecification.

江苏省未来植被变化对“碳达峰、碳中和”的影响评价

在全国推进“碳达峰、碳中和”的政策背景下,包含碳汇的模型研究对指导减排具有重要意义。以江苏省为例,依据1997—2018年的年碳排放量数据建立ARIMA(5,2,0)模型,对2019—2060年的年碳排放量进行预测和估算。结果显示,江苏省年碳排放量在未来40 a内将保持波动上升的趋势。根据江苏省植被类型分布面积和相关植物的光合速率,得到每种植被类型的CO₂年吸收总量,进一步分析不同植被变化下的减排方案,评价未来植被变化对“碳达峰、碳中和”的影响。在植被可增加面积有限且仅种植光合速率较大的经济林的条件下：1)若2030年后CO₂排放量保持不变,排放量应控制在2030年的26.94%,植被面积需增加1.078×10⁹ m²才能在2060年顺利实现碳中和。2)若2030年后每年CO₂排放量与预测结果保持一致,2030年开始年排放量在预测结果的基础上减少81.06%,植被面积需增加1.081×10⁹ m²,可在2060年顺利实现碳中和。3)若...