一种改进编码器角度解算过程的方法与实现

在机械电子一直是一个热门学科,其目的是通过软件控制机械操作来代替机械的哑巴解决方案。DS-25旋转电子编码器能够很好地与机械电子应用相匹配,其输出为两路标准的sine和cosine曲线,通过分析sine和cosine数值来计算编码器所对应的绝对角度位置。通过对DS-25的工作模式分析和实际应用情况提出角度解算的改进方案,该方案利用DS-25工作于粗略模式下测试到的角度值来推算精确模式下的信号周期,结合精确模式下测试到的角度值来计算编码器所对应的绝对角度。摒弃其原有的复杂查表过程进而节省电子表格的存储空间,在降低硬件成本的同时提升了软件灵活性。实验证明,算法的改进能够节省约2KB的存储空间,角度位置误差能控制在1‰以内。     

Monitoring land surface processes with thermal infrared data: Calibration of SVAT parameters based on the optimisation of diurnal surface temperature cycling features

Land Surface Models (LSM) have been designed to describe water and energy transfers at the soil-vegetation-atmosphere interface, and are therefore essential in many environmental disciplines. These numerical models, driven by the boundary conditions in the atmosphere and in the soil, require adequate knowledge of those vegetation and soil characteristics which are determinant in the characterisation of mass and energy transfers. In view of the fact that, firstly this information is often only partially known, and secondly the transfers are sometimes incorrectly represented, these models can rapidly drift and need to be regularly corrected. To this aim, remote sensing is a promising tool and many studies are currently devoted to the development of assimilation techniques to control their inputs or internal variables. The research presented in this paper contributes to this effort. Its ambition is to explore new methodologies, designed to make use of remote sensing thermal infrared data recorded from space. This study is based on the analysis of links between the characteristics of the diurnal cycle of the surface brightness temperature and the soil-atmosphere interface parameters and variables. The proposed methodology takes advantage of these temperatures cycling features, instead of absolute temperature values, to calibrate the LSM. The results show that the model parameters have a significant impact on the diurnal temperature dynamics, sometimes to a greater extent than on the temperature itself, and that these relationships have diurnal and seasonal variations. As a consequence, the use of TIR data for LSM calibration can be optimised by considering only those parts of the information which are really relevant to parameter calibration.     

An extension of likelihood-ratio-test for testing linear hypotheses in the baseline-category logit model

A new family of test statistics for testing linear hypotheses in baseline-category logit models is introduced and its asymptotic distribution is obtained. The new family is a natural extension of the classical likelihood ratio test. A simulation study is carried out to find new test statistics that offer an attractive alternative to the classical likelihood ratio test in terms of both exact size and exact power.     

A general topology-based framework for adaptive insertion of cohesive elements in finite element meshes

Large-scale simulation of separation phenomena in solids such as fracture, branching, and fragmentation requires a scalable data structure representation of the evolving model. Modeling of such phenomena can be successfully accomplished by means of cohesive models of fracture, which are versatile and effective tools for computational analysis. A common approach to insert cohesive elements in finite element meshes consists of adding discrete special interfaces (cohesive elements) between bulk elements. The insertion of cohesive elements along bulk element interfaces for fragmentation simulation imposes changes in the topology of the mesh. This paper presents a unified topology-based framework for supporting adaptive fragmentation simulations, being able to handle two- and three-dimensional models, with finite elements of any order. We represent the finite element model using a compact and “complete” topological data structure, which is capable of retrieving all adjacency relationships needed for the simulation. Moreover, we introduce a new topology-based algorithm that systematically classifies fractured facets (i.e., facets along which fracture has occurred). The algorithm follows a set of procedures that consistently perform all the topological changes needed to update the model. The proposed topology-based framework is general and ensures that the model representation remains always valid during fragmentation, even when very complex crack patterns are involved. The framework correctness and efficiency are illustrated by arbitrary insertion of cohesive elements in various finite element meshes of self-similar geometries, including both two- and three-dimensional models. These computational tests clearly show linear scaling in time, which is a key feature of the present data-structure representation. The effectiveness of the proposed approach is also demonstrated by dynamic fracture analysis through finite element simulations of actual engineering problems.

A multiperiod set covering location model for dynamic redeployment of ambulances

Emergency medical service (EMS) providers continually seek ways to improve system performance particularly the response time to incidents. The demand for ambulances fluctuate throughout the week, depending on the day of week, and even the time of day, therefore EMS operators can improve system performance by dynamic relocation/redeployment of ambulances in response to fluctuating demand patters. The objective of the model is to determine the minimum number of ambulances and their locations for each time cluster in which significant changes in demand pattern occur while meeting coverage requirement with a predetermined reliability. The model is further enhanced by calculating ambulance specific busy probabilities and validated by a comprehensive simulation model. Computational results on experimental data sets and data from an EMS agency are provided.     

An atomistic-continuum inhomogeneous material model for the elastic bending of metal nanocantilevers

The equivalent elastic modulus of nanocantilever can be obtained using atomistic simulation. However, the use of this modulus to predict the bending of nanocantilever results in significant error compared with direct atomistic simulation. The error originates from the surface effect. In our current work, the nanocantilever is considered as an inhomogeneous continuum material. The distributions of materials parameters at the cross-section, such as atomistic elastic constants, are calculated from atomistic simulations. These atomistic-information-based materials parameters are used as inputs to continuum model. A numerical example case validates the presented model and methodology. To correctly predict the structure-property relations of elemental nano-structures are very important for the design of nano-devices. Our continuum model includes nano-effects and provides another way to study nanomechanics.     

基于切片技术获取系统测试用例的方法

针对如何获取局部和全部的系统测试用例,确保其正确性和完备性以及与需求的一致性问题,提出利用先进的建模技术,建立可模拟验证的过程模型,并应用切片技术获取测试用例,并利用基于过程模型结构分析的归纳法证明了该法的正确性,根据过程模型切片准则获取系统测试用例的算法,介绍了实现工具的构成和应用实例。     

基于UML可适应的教学考评系统分析与设计

该文给出了UML的概念与要点,应用UML对教学考评系统进行了建模。给出了系统的用例模型、整体结构模型、静态模型、动态模型,并分析了模型对教学考评变化的可适应性。     

基于信任域的移动adhoc网络信任模型研究

详细阐述了基于信任域的信任模型策略分析、模型的基本设计思想、模型中的数据结构,探讨了保障簇代理安全性的措施,研究了计算机信任值及修正信任值的方法。