Assessing spatial and temporal variations in surface soil moisture in fire-disturbed black spruce forests in Interior Alaska using spaceborne synthetic aperture radar imagery — Implications for post-fire tree recruitment

Recent studies [Bourgeau-Chavez, L.L., Kasischke, E.S., Riordan, K., Brunzell, S.M., Nolan, M., Hyer, E.J., Slawski, J.J., Medvecz, M., Walters, T., and Ames, S. (in press). Remote monitoring of spatial and temporal surface soil moisture in fire disturbed boreal forest ecosystems with ERS SAR imagery. Int. J. Rem. Sens.] demonstrated that ERS SAR imagery can be used to estimate surface soil moisture in recently burned black spruce forests in interior Alaska. We used this relationship to analyze the intra- and inter-annual variations surface soil moisture in two burned black spruce forests in Alaska. The results of this study showed distinct seasonal and longer-term trends in soil moisture in the two sites, with the site that burned in 1994 having higher soil moisture than the site that burned in 1999. The differences in soil moisture between the sites were related to landscape-scale variations in soil drainage and seasonal permafrost thawing. Finally, we found that the 1999 site had dramatically lower levels of tree recruitment (both aspen and black spruce) than the 1994 site as a result of the lower soil moisture levels. These results show that the ERS SAR and similar systems can be used to monitor a site characteristic that is important to understanding changes in the ecosystem community structure that result from variations in climate and the fire regime in the boreal region.     

Mixed Dimensional Coupling in Finite Element Stress Analysis

Many analysis models utilize finite elements of reduced dimension. However, to capture stress concentrations at local details, it would be desirable to combine the reduced dimensional element types with higher dimensional elements in a single finite element model. It is therefore important in such cases to integrate into the analyses some scheme for coupling the element types that conforms to the governing equations of the problem. In this paper, a novel method that can correctly couple beams to solids, beams to shells and shells to solids for elastic problems is presented. The approach adopted is to equate the work done on either side of the interface between dimensions, and this leads to multi-point constraint equations, thus providing a relationship among nodal degrees of freedom between the differing element types. Example results show that the proposed technique does not introduce any spurious stresses at the dimensional interfaces. ID="A1" Correspondence and offprint requests to: C. G. Armstrong, School of Mechanical and Manufacturing Engineering, The Queen's University of Belfast, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland. E-mail: c.armstrong@qub.ac.uk     

Willingness-to-pay for reducing fatal accident risk in urban areas: an Internet-based Web page stated preference survey

Contemporary transport project evaluation requires the ability to value reductions in the number of estimated fatal and non-fatal accidents after project implementation. In this quest, we designed a stated preference (SP) experiment to estimate willingness-to-pay (WTP) for reducing fatal accident risk in urban areas. The survey was implemented in a Web page allowing rapid turnover and a complete customisation of the interview. The sample was presented with a series of route choice situations based on travel time, cost and number of car fatal accidents per year. With this data we estimated Multinomial Logit (MNL) and Mixed Logit (ML) models based on a consistent microeconomic framework; the former with linear and non-linear utility specifications and allowing for various stratifications of the data. The more flexible ML models also allow to treat the repeated observations problem common to SP data and, as expected, gave a better fit to the data in all cases. Based on these models, we estimated subjective values of time, that were consistent with previous values obtained in the country, and also sensible values for the WTP for reductions in fatal accident risk. Thus, the Internet appears as a potentially very interesting medium to carry out complex stated choice surveys.     

Mixed-mode crack propagation through reinforced concrete

This paper presents the results of a very recent experimental research program aimed at investigating mixed-mode fracture of reinforced concrete. The tests were designed so that only one single mixed-mode crack generates and propagates through the specimen, as opposed to the usual dense crack pattern found in most of the tests in scientific literature. The specimens were three-point-bend beams of three different sizes. They were notched asymmetrically and reinforced with various ratios of longitudinal and inclined reinforcement. These experiments may help to understand the mechanisms of crack initiation and propagation through reinforcing bars under mixed-mode load conditions.     

Mass appraisal of residential apartments: An application of Random forest for valuation and a CART-based approach for model diagnostics

To the best knowledge of authors, the use of Random forest as a potential technique for residential estate mass appraisal has been attempted for the first time. In the empirical study using data on residential apartments the method performed better than such techniques as CHAID, CART, KNN, multiple regression analysis, Artificial Neural Networks (MLP and RBF) and Boosted Trees. An approach for automatic detection of segments where a model significantly underperforms and for detecting segments with systematically under- or overestimated prediction is introduced. This segmentational approach is applicable to various expert systems including, but not limited to, those used for the mass appraisal.     

数模混合电路衬底耦合模型研究

提出了数模混合集成电路衬底耦合噪声的一种建模方案将集成电路芯片的衬底划分为多个Voronoi图,计算各区域的R、C值,在将衬底RC网络映射到原电路网表之后,对新网表进行SPICE模拟,分析数模混合集成电路中的衬底噪声.用此模型模拟了两个数模混合集成电路的衬底耦合噪声,指出了在模拟电路关键器件周围加保护环是减少衬底耦合噪声的一种有效途径.     

简论水泥搅拌桩复合地基与基础设计

本文对水泥搅拌桩复合地基与基础设计中基础面积的确定、桩长的确定和基础抗弯设计进行了探讨,并提出看法和建议,可供结构设计人员参考。     

Retaining the influence of crucial local effects in mixed Guyan and modal reduction

For the modal frequency and transient response analysis of moderate to large-sized structures, as well as residual structures that consist of synthesized, component mode-reduced sub-models with common boundaries, the structural model is most effectively reduced by the mixed Guyan and modal reduction. A strategy for the correct reduction of such systems which necessarily retains the crucial degrees of freedom in the reduced system is presented. A detailed set of practical guidelines for the appropriate selection of such degrees of freedom is given. To obtain the transformation to modal subspace, this reduction is followed by an eigensolution and the transformation is performed without shedding any degrees of freedom of the reduced model. This procedure automatically includes the high-frequency quasi-static mode shapes that are necessary to retain the influence of crucial local effects in the reduced system. Example problems that include important elements such as a stiff spring, a nonlinear stopper mechanism, and a concentrated excitation force, are presented to demonstrate the strength of the method in the solution of practical industrial applications. These example problems may also serve as reference problems for future developments in modal dynamic analysis techniques.     

Foundations of mathematics under neuroscience conditions of lateral inhibition and lateral activation

Abstract

In neuroscience we know that there exist the following two basic effects in perceiving information: (i) the lateral inhibition, responsible for a cognitive blindness in seeing the whole picture; (ii) the lateral activation, responsible for a cognitive blindness in seeing the details. In this paper, we show that the same effects can be considered in the proof cognitions performed by mathematicians in proving sophisticated theorems, such as Fermat’s Last Theorem. Hence, we insist that there can be two different foundations of mathematics: (i) the discrete foundations, dealing with a logical way of automatic proving from some axioms (the lateral inhibition in math); (ii) the analogue foundations, combining proof trees on tree forests by using the analogies as inference metarules (the lateral activation in math). We propose a kind of analogue logic for analogue reasoning in mathematics.     

Arrangement of the computer code for the prediction of forest fire spread

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