Bayesian Nonparametric Joint Mixture Model for Clustering Spatially Correlated Time Series

Abstract

We develop a Bayesian nonparametric joint mixture model for clustering spatially correlated time series based on both spatial and temporal similarities. In the temporal perspective, the pattern of a time series is flexibly modeled as a mixture of Gaussian processes, with a Dirichlet process (DP) prior over mixture components. In the spatial perspective, the spatial location is incorporated as a feature for clustering, like a time series being incorporated as a feature. Namely, we model the spatial distribution of each cluster as a DP Gaussian mixture density. For the proposed model, the number of clusters does not need to be specified in advance, but rather is automatically determined during the clustering procedure. Moreover, the spatial distribution of each cluster can be flexibly modeled with multiple modes, without determining the number of modes or specifying spatial neighborhood structures in advance. Variational inference is employed for the efficient posterior computation of the proposed model. We validate the proposed model using simulated and real-data examples. Supplementary materials for the article are available online.     

Steel slag waste combined with melamine pyrophosphate as a flame retardant for rigid polyurethane foams

To explore the potential application of industrial waste, steel slag powder in combination with melamine pyrophosphate (MPP) was adopted to improve the flame retardancy of rigid polyurethane foam (RPUF). The incorporation of steel slag slightly reduced the thermal conductivity of the resulting flame-retardant RPUF samples. The addition of MPP and/or steel slag did not significantly alter the thermal stability in terms of T_-10% and T_max but did obviously increase the T_-50% value, suggesting the improved thermal resistance of the residues. The coaddition of MPP and steel slag into RPUF resulted in higher LOI values and lower peak heat release rates than the samples incorporating either MPP or steel slag alone. The superior flame retardancy could be attributed to MPP promoting char formation, which then acted as a barrier at the beginning of RPUF thermal decomposition; simultaneously, the thermally stable inorganics in the steel slag powder strengthened the thermal resistance of this char layer.     

部分国家能源战略及对我国的启示

本文通过对美国、日本、英国、俄罗斯、伊朗、印尼的能源发展对比分析，分别归纳出了发达国家、资源大国、发展中国家在新时期的能源战略特点，并对我国未来一段时间能源战略提出了相关建议。     

用氨化P_(507)对龙南稀土萃取分组Nd-Sm的研究

本文报道了用氨化与不氨化P_(507)萃取分组Nd-Sm的对比效果。并对氧化萃取分组Nd-Sm的既定条件如相混合时间,萃取酸度、氨化率、相比等进行了探讨。在上述条件试验的基础上,完成了Nd-Sm分组分馏萃取串级实验。证明用氯化P_(507)萃取及分离稀土元素,能够提高萃取稀土的效果,提高萃取剂的萃取容量。是一种有发展前途的新的萃取工艺方法。     

高压辊磨机在冶金矿业的应用前景

在概述高压辊磨机的辊磨原理的基础上，分析了辊磨后物料对矿物回收率的影响及在设备结构上的最新改进，探讨了高压辊磨机普遍应用于冶金矿业的必要性和可行性。     

节能省地型住宅设计探讨——“2006全国节能省地型住宅设计竞赛”获奖作品评析

本文是作者参与“全国节能省地型住宅设计竞赛”获奖作品的设计理念介绍。基于作者多年住宅设计相关方面的研究经验,本文从“规划:在高容积率的压力下争取居住的舒适度;楼栋:以丰富、合理的户型结构满足不同购房需求;户型:灵活可变,以人为本,确保生活质量;技术:全面系统,经济实用”这4个层面对于中小户型住宅设计进行了深入、细致地探讨,提出一整套切实可行的既节能省地又舒适宜居的设计理念。     

THE EFFECTS OF IMPROVING SEWAGE SLUDGE DIGESTION

A model was developed and tested to investigate the effects of various parameters on the processing costs of anaerobic digestion. The model was based on empirical data collected from full-scale plants which varied in size from 35,000 to 900,000 population equivalents. (Equivalent to loading rates of 0.5 to 2.7 kg VS/m³/d.) In spite of different operating regimes and conditions of the plants analysed, various relationships were discovered between: sludge quality and volatile solids destruction; sludge quality and biogas yield; and, effluent volatile solids and dewatering. Where correlations existed, these were used to make predictions on operating costs of the digestion and dewatering plant based on sensitivity analysis. The results of the model were used to make recommendations on how to optimise the operation of an anaerobic digestion plant.     

The impact of using chilled water storage systems on the performance of air cooled chillers in Kuwait

In the air conditioning (AC) industry chilled water storage (CWS) systems are one form of cool thermal storage technology that can be used to time shift the electrical load of the system from the peak day periods to off peak night time periods. In this paper the data for the actual exported and generated electrical energy obtained for the power stations in Kuwait has been used to estimate the electrical energy consumption and the peak electrical load of AC systems. Since the chiller in an air cooled AC system represent more than 75% of the total electrical power consumed by an AC system during the peak demand period, the impact of using CWS systems with alternative operating strategies including partial (load levelling), partial (demand limiting) and full load has been investigated. In our conclusions we estimate that approximately 45% of the total annual exported electrical energy is consumed solely by AC systems as a result of the very high ambient temperatures occurring between March and October. Furthermore, it is estimated AC systems represent about 62% of the peak electrical load. The results demonstrate that CWS can reduce the peak electrical load of a chiller in an air cooled AC system by up to 100% and reduce the nominal chiller size by up to 33% depending upon the operating strategy adopted. This is achieved with only a 4% increase in power consumption of the chiller for all CWS strategies except for full storage where the energy consumption actually decreases by approximately 4%.     

Organochlorine residues in two seal species from Western Iceland

Harbour seals and grey seals from Faxaflói (Western Iceland) were analyzed for contamination with organochlorines (HCB, PCBs, p,p′-DDT, p,p′-DDE, chlordanes and the enantiomers of α-HCH). Although the values strongly varied, both harbour seals and grey seals on average showed comparable levels of PCBs, p,p′-DDT, p,p′-DDE and α-HCH, as well as chlordanes (ΣCD). Differences were measured in the HCB content of the seal species. The HCB/α-HCH ratio in harbour seals was <1 and in grey seals >1. The results from seals on Iceland were compared with data derived from seal samples of the Antarctic, the Arctic (Spitzbergen) and the North Sea (Germany) in order to give an insight into the global distribution of pollution with chlorinated organics.