On the constraints violation in forward dynamics of multibody systems

It is known that the dynamic equations of motion for constrained mechanical multibody systems are frequently formulated using the Newton–Euler’s approach, which is augmented with the acceleration constraint equations. This formulation results in the establishment of a mixed set of partial differential and algebraic equations, which are solved in order to predict the dynamic behavior of general multibody systems. The classical solution of the equations of motion is highly prone to constraints violation because the position and velocity constraint equations are not fulfilled. In this work, a general and comprehensive methodology to eliminate the constraints violation at the position and velocity levels is offered. The basic idea of the described approach is to add corrective terms to the position and velocity vectors with the intent to satisfy the corresponding kinematic constraint equations. These corrective terms are evaluated as a function of the Moore–Penrose generalized inverse of the Jacobian matrix and of the kinematic constraint equations. The described methodology is embedded in the standard method to solve the equations of motion based on the technique of Lagrange multipliers. Finally, the effectiveness of the described methodology is demonstrated through the dynamic modeling and simulation of different planar and spatial multibody systems. The outcomes in terms of constraints violation at the position and velocity levels, conservation of the total energy and computational efficiency are analyzed and compared with those obtained with the standard Lagrange multipliers method, the Baumgarte stabilization method, the augmented Lagrangian formulation, the index-1 augmented Lagrangian, and the coordinate partitioning method.     

Distance maps from unthresholded magnitudes

A straightforward algorithm that computes distance maps from unthresholded magnitudes is presented, suitable for still images and video sequences. While results on binary images are similar to classic Euclidean Distance Transforms, the proposed approach does not require a binarization step. Thus, no thresholds are needed and no information is lost in intermediate classification stages. Experiments include the evaluation of spatial and temporal coherence of distance map values, showing better results in both measurements than those obtained with Sobel or Deriche gradients and classic chessboard distance transforms.     

Cyclic staff scheduling: optimization models for some real-life problems

In this work, we propose a general integer programming model to address the staff scheduling problem, flexible enough to be easily adapted to a wide-range of real-world problems. The model is applied with slight changes to two case studies: a glass plant and a continuous care unit, and also to a collection of benchmark instances available in the literature. The emphasis of our approach is on a novel formulation of sequence constraints and also on workload balance, which is tackled through cyclic scheduling. Models are solved using the CPLEX solver. Computational results indicate that optimal solutions can be achieved within a reasonable amount of time.     

Extended Algorithms for Approximating Variable Order Fractional Derivatives with Applications

This paper proposes accurate and robust algorithms for approximating variable order fractional derivatives of arbitrary order. The proposed schemes are based on finite difference approximations. We compare the performance of algorithms by introducing a new formulation of experimental convergence order. Two initial value problems are considered and solved by means of the proposed methods. Numerical results are provided justifying the usefulness of the proposed methods.     

Detection of Redundant Code Using R 2 D 2

We present the R ² D ² redundancy detector. R ² D ² identifies redundant code fragments in large software systems written in Lisp. For each pair of code fragments, R ² D ² uses a combination of techniques ranging from syntax-based analysis to semantics-based analysis, that detects positive and negative evidences regarding the redundancy of the analyzed code fragments. These evidences are combined according to a well-defined model and sufficiently redundant fragments are reported to the user. R ² D ² explores several techniques and heuristics to operate within reasonable time and space bounds and is designed to be extensible.     

NETmix®, a new type of static mixer: Modeling,simulation, macromixing,and micromixing characterization

NETmix® is a new technology for static mixing based on a network of chambers connected by channels. The NETmix® model is the basis of a flow simulator coupled with chemical reaction used to characterize macro and micromixing in structured porous media. The chambers are modeled as perfectly mixing zones and the channels as plug flow perfect segregation zones. A segregation parameter is introduced as the ratio between the channels volume and the whole network volume. Different kinetics and reactants injection schemes can be implemented. Results show that the number of rows in the flow direction and the segregation parameter control both macro and micromixing, but the degree of micromixing is also controlled by the reactants injection scheme. The NETmix® model enables the systematic study of micromixing and macromixing for different network structures and reaction schemes, enabling the design of network structures to ensure the desired yield and selectivity. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Business-Driven Design of Infrastructures for IT Services

A methodology for designing data center infrastructure for Information Technology (IT) services is developed. The main departure from existing methodologies is that it evaluates and compares alternative designs using business metrics rather than purely technical metrics. Specifically, the methodology evaluates the business impact (financial loss) imposed by imperfect infrastructure. The methodology provides the optimal infrastructure that minimizes the sum of provisioning costs and business losses incurred during failures and performance degradations. Several full numerical example scenarios are provided and results are analyzed. The use of the method for dynamically provisioning an adaptive infrastructure is briefly discussed.     

北京居民骨中^87Rb比活度及所致内照射剂量估算

本文报道了北京地区56例居民骨灰样品中铷(Rb)浓度的热中子活化分析结果。结果表明,骨灰中Rb浓度呈对数正态分布,范围为1—15.4μg/g(骨灰),几何均值为5.0μg/g(骨灰),几何标准差为1.7;算术均值和标准差分别为5.5和3.3μg/g(骨灰)。在假定体内Rb浓度等于无机骨中Rb浓度条件下,估算出北京居民体内Rb平均浓度为3.0mg/kg(体内~(87)Rb平均比活度为2.8Bq/kg),体负荷量为0.21g,骨沉积量为15mg。并讨论了骨中Rb浓度与年龄和性别的关系。由体内~(87)Rb平均比活度,根据UNSCEAR1986年报告模式估算体内~(87)Rb所致居民年有效剂量当量约为1.9μSv。     

The electronic booklet on teaching-learning process: Teacher vision and parents of students in primary and secondary education

This article presents the first phase of a research project whose purpose is to introduce a new form of collaboration and communication between the school and the family through an Electronic Booklet (EB). The EB was developed due to the increasing necessity of collaboration between the school and the family, promoting the teaching-learning process and educational success, supported by information and communication technologies. These conclusions and justifications were derived from a survey based in a questionnaire applied to guardians and teachers of several private and public Portuguese schools of the primary and secondary education level. Both groups – guardians and teachers stressed the importance of communication between school and family and expressed interest in the EB as a communication tool. The analysis of the survey results made possible the construction of an Electronics Booklet prototype.