Estimating size fraction categories of coal particles on conveyor belts using image texture modeling methods

Motivation: Physical properties of coal such as particle size distribution have a large influence on the stability and operational behavior of fluidized bed reactors and metallurgical furnaces. In particular, the presence of large amounts of “fine” particles invariably has a drastic effect on plant performance as a result of impaired gas permeability characteristics of the coal or ore burden. Therefore, monitoring and control of particle size distribution profiles of such aggregate material on reactor feed streams, such as moving conveyor belts, is critical for predictable operation of these processes. Traditionally, the method of sieve analysis using stock or belt cut samples has been widely used in industry. Unfortunately, the reliability and usefulness of belt cut techniques are constrained by frequency of sampling as well as laboratory analysis turnaround times. For real-time monitoring and control purposes, automated sampling and analysis methods are more desirable. Methods: In this study, the problem of estimating the particle size distribution profile of material on a moving conveyor belt is formulated within a texture classification framework, which has its basis in machine vision and incorporates elements from statistical pattern recognition. Using exemplar images of coal particles taken on a process stream, a set of local features that compactly describes the textural properties of each image are expressed in terms of localized nonlinear features called textons. Representation of image information using textons is primarily motivated by insights from neuroscience research on the optimality of linear oriented basis functions as models of perception in early processing of visual information in the cortex regions of the human brain. Using these representations for different textures, nearest neighbor and support vector machine classification models are subsequently used to classify test images. Results: Using a comprehensive evaluation, it is shown that the use of texton representation obtained from decomposing images with linear oriented basis functions can be sufficiently discriminative compared to the use of the widely used second-order statistical features or features from other baseline models. In particular, model performance obtained with appropriately tuned filters suggest the importance of including shape and spatial structure information in an image representation for texture classification of coal particles. Furthermore, using nonlinear support vector machines rather than nearest neighbor classifiers significantly improved classification performance. A texture classification approach to particle size profile estimation has potential applications in the online monitoring of the proportion of “fines” in coal material on moving conveyor belts.     

Critical Role of Triplet Exciton Interface Trap States in Bilayer Films of NPB and Ir(piq)3

Investigations are carried out into triplet transfer in bilayer films of NPB (N,N´‐diphenyl‐N,N´‐bis(1‐naphthyl)‐1,1´‐biphenyl‐4,4?‐diamine) and Ir(piq)₃ (Iridium (III) Tris(1‐phenylisoquinoline) using laser light pulses to excite the upper surface of the NPB, and thereafter observing the decay dynamics in the Ir(piq)₃ layer situated beneath the NPB. The NPB layer thickness is varied from 13 nm to 80 nm. The results show that up to 200 ns after excitation, the multiexponential decay of directly excited Ir(piq)₃ is observed, thereafter the decay is monoexponential. It is concluded that this monoexponential decay after 200 ns is due to triplets that are transferred to the Ir(piq)₃ via migration from the NPB. The thicker the NPB layer the longer it takes for the reservoir of NPB triplets to deplete via the Ir(piq)₃, with the result that the apparent monoexponential lifetime of the Ir(piq)₃ increases as the thickness of the NPB films increases. Based on time resolved spectra and decays, it is concluded that triplets arriving from NPB are trapped at interface sites of Ir(piq)₃ and do not migrate directly to the bulk states of Ir(piq)₃. A model based on exciton diffusion kinetics, including the presence of interface trap sites, is described, which accurately predicts this behavior.     

谨慎的开始

在经历了数周的增长之后,由于银行业出炉了不容乐观的财务报告,以及财政与货币政策收紧等不利因素的影响,全球股市在2010年1月底开始变得谨慎起来.     

Molecular and mechanical properties of hydroxypropyl methylcellulose solutions during the sol:gel transition

This paper outlines the latest findings in our work to understand the fundamental interactions within hydrated hydroxypropyl methylcellulose (HPMC) at elevated temperature. ATR-FTIR spectroscopy was used to relate molecular interactions to the rheological changes in aqueous HPMC solutions during the sol:gel transition. Sol:gel transition temperatures determined using ATR-FTIR spectroscopy, oscillatory rheology and turbidimetry were in agreement to within experimental error. ATR-FTIR spectroscopy provided direct evidence of increased hydrophobic interactions within the gel network through a shift to lower wavenumber of ν_as(CH) vibrations observed during the gelation process. In addition, the FTIR spectra provide evidence that the structure of the polymer network is different in the thermo-formed gel, to that which exists in viscous solution. Both the rheological and ATR-FTIR data confirmed the supposition that thermal gelation is a two stage process. The first stage has been attributed to the disruption of native cellulosic bundles and this is supported by the changes in both the storage modulus and intensity of the ν(CO) band at low temperatures. The second stage corresponded to phase separation and gelation resulting from increased hydrophobic interactions between polymer chains at elevated temperatures.     

天津市成都道新建村住宅小区

项目背景：本项目位于天津市著名的五大道之一的成都道．是现代城市中心地段的高档高层住宅小区和沿街商业建筑的综合发展项目。建筑单体及总平面设计采用现代风格，设计任务书对景观设计的要求是：设计风格是后现代的．手法和材料是现代的．尽量将传承地域文化的片断融合在设计中。     

Finite element modelling of the effect of non-metallic inclusions in metal forming processes

The presence of non-metallic inclusions can result in material failure during the metal forming process, or lead to a serious deterioration of the quality of the final product. Understanding the effects of inclusions during metal forming is therefore an important step towards predicting the behaviour of inclusions and subsequently minimising their consequences. To achieve this understanding the authors incorporated non-metallic inclusions into a finite element (FE) simulation of metal forming. The chosen metal forming process was rod drawing, the chosen inclusion material aluminium oxide (Al₂O₃) and the chosen inclusion shape spherical. Real rod drawing experiments were also designed with Al₂O₃ spheres embedded in a steel rod in order to compare experimental and simulated results. Specifically, from the experiments carried out the changes of the rod around the inclusion were investigated and the findings compared with the finite element simulation results of an equivalent model. The FE simulation of the experiments considered specifically the fracturing of brittle inclusions. A concept allowing the fracturing of brittle inclusions by means of finite element method is described. Experimental results from fourpoint bending tests, and tensile tests, for Al₂O₃ ceramic bodies were used to calibrate the simulation. Further experiments involved the crushing of Al₂O₃ spheres where the force necessary to achieve crushing was measured and compared with the results of the calibrated FE simulation. It is demonstrated that the intended FE method for the simulation of brittle fracture of inclusions can be used with good accuracy.     

Change point detection in time series data with random forests

A large class of monitoring problems can be cast as the detection of a change in the parameters of a static or dynamic system, based on the effects of these changes on one or more observed variables. In this paper, the use of random forest models to detect change points in dynamic systems is considered. The approach is based on the embedding of multivariate time series data associated with normal process conditions, followed by the extraction of features from the resulting lagged trajectory matrix. The features are extracted by recasting the data into a binary classification problem, which can be solved with a random forest model. A proximity matrix can be calculated from the model and from this matrix features can be extracted that represent the trajectory of the system in phase space. The results of the study suggest that the random forest approach may afford distinct advantages over a previously proposed linear equivalent, particularly when complex nonlinear systems need to be monitored.     

Constraints to wildlife harvesting among aboriginal communities in Alaska and Canada

A large body of research confirms that access to wildlife resources can reduce conditions of food insecurity and health related illness among Aboriginal peoples in Canada and Alaska. Yet the procurement of wildfoods depends on the ability of Aboriginal households to overcome a range of obstacles that impede such access. Utilizing a data set collected between 2007 and 2013, this paper identifies a range of barriers that Aboriginal households in Alaska (Gwich’in), Alberta (Cree), Nunavik (Inuit), and Nunatsiavut (Inuit) encounter in accessing wildfoods. The results demonstrate that the constraints experienced by Aboriginal peoples in Canada and Alaska in accessing wildfoods are experienced differently depending on region, community, age, gender, and the political environment in which wildlife harvesting occurs. These findings underscore the diversity of factors that can influence one’s access to wildlife resources, and one’s chance of being food insecure. It is hoped that the results of this research will lead to a more informed understanding of Aboriginal food security in the Arctic and Sub-Arctic Regions of North America, and can contribute to more flexible policies that can account for the social, economic and political diversity in which Aboriginal food insecurity is experienced.