A stable elemental decomposition for dynamic process optimization

AbstractIn Cervantes and Biegler (A.I.Ch.E.J. 44 (1998) 1038), we presented a simultaneous nonlinear programming problem (NLP) formulation for the solution of DAE optimization problems. Here, by applying collocation on finite elements, the DAE system is transformed into a nonlinear system. The resulting optimization problem, in which the element placement is fixed, is solved using a reduced space successive quadratic programming (rSQP) algorithm. The space is partitioned into range and null spaces. This partitioning is performed by choosing a pivot sequence for an LU factorization with partial pivoting which allows us to detect unstable modes in the DAE system. The system is stabilized without imposing new boundary conditions. The decomposition of the range space can be performed in a single step by exploiting the overall sparsity of the collocation matrix but not its almost block diagonal structure. In order to solve larger problems a new decomposition approach and a new method for constructing the quadratic programming (QP) subproblem are presented in this work. The decomposition of the collocation matrix is now performed element by element, thus reducing the storage requirements and the computational effort. Under this scheme, the unstable modes are considered in each element and a range-space move is constructed sequentially based on decomposition in each element. This new decomposition improves the efficiency of our previous approach and at the same time preserves its stability. The performance of the algorithm is tested on several examples. Finally, some future directions for research are discussed

Conflict-Based Model Predictive Control for Scalable Multi-Robot Motion Planning

This paper presents a scalable multi-robot motion planning algorithm called Conflict-Based Model Predictive Control (CB-MPC). Inspired by Conflict-Based Search (CBS), the planner leverages a similar high-level conflict tree to efficiently resolve robot-robot conflicts in the continuous space, while reasoning about each agent's kinematic and dynamic constraints and actuation limits using MPC as the low-level planner. We show that tracking high-level multi-robot plans with a vanilla MPC controller is insufficient, and results in unexpected collisions in tight navigation scenarios. Compared to other variations of multi-robot MPC like joint, prioritized, and distributed, we demonstrate that CB-MPC improves the executability and success rate, allows for closer robot-robot interactions, and reduces the computational cost significantly without compromising the solution quality across a variety of environments. Furthermore, we show that CB-MPC combined with a high-level path planner can effectively substitute computationally expensive full-horizon multi-robot kinodynamic planners

A tool to analyze robust stability for constrained nonlinear MPC

A sufficient condition for robust asymptotic stability of nonlinear constrained model predictive control (MPC) is derived with respect to plant/model mismatch. This work is an extension of a previous study on the unconstrained nonlinear MPC problem, and is based on nonlinear programming sensitivity concepts. It addresses the discrete time state feedback problem with all states measured. A strategy to estimate bounds on the plant/model mismatch is proposed that can be used off-line as a tool to assess the extent of model mismatch that can be tolerated to guarantee robust stability.http://www.sciencedirect.com/science/article/B6V4N-4R7F42T-2/1/7729956156701c2970c6a488f929884

As above, so below: whole transcriptome profiling demonstrates strong molecular similarities between avian dorsal and ventral pallial subdivisions

Over the last two decades, beginning withthe Avian Brain Nomenclature Forum in2000, major revisions have been made to our understanding of the organization andnomenclature of the avian brain. However, there are still unresolved questions on avianpallial organization, particularly whether the cells above the vestigial ventricle representdistinct populations to those below it or similar populations. To test these two hypothe-ses, we profiled the transcriptomes of the major avian pallial subdivisions dorsal and ven-tral to the vestigial ventricle boundary using RNA sequencing and a new zebra finchgenome assembly containing about 22,000annotated, complete genes. We found thatthe transcriptomes of neural populations above and below the ventricle were remarkablysimilar. Each subdivision in dorsal pallium (Wulst) had a corresponding molecular counter-part in the ventral pallium (dorsal ventricularridge). In turn, each corresponding subdivi-sion exhibited shared gene co-expression modules that contained gene sets enriched infunctional specializations, such as anatomical structure development, synaptic transmis-sion, signaling, and neurogenesis. Thesefindings are more in line with the continuumhypothesis of avian brain subdivision organization above and below the vestigial ventriclespace, with the pallium as a whole consisting offour major cell populations (intercalatedpallium, mesopallium, hyper-nidopallium, andarcopallium) instead of seven (hyperpalliumapicale, interstitial hyperpallium apicale, intercalated hyperpallium, hyperpalliumdensocellare, mesopallium, nidopallium, and arcopallium). We suggest adopting a morestreamlined hierarchical naming system thatreflects the robust similarities in geneexpression, neural connectivity motifs, and function. These findings have important impli-cations for our understanding of overall vertebrate brain evolution

3-D multiobservable probabilistic inversion for the compositional and thermal structure of the lithosphere and upper mantle: III. Thermochemical tomography in the Western-Central U.S.

Acknowledgments We are indebted to F. Darbyshire and J. von Hunen for useful comments on earlier versions of this work. This manuscript benefited from thorough and constructive reviews by W. Levandowski and an anonymous reviewer. We also thank J. Connolly, M. Sambridge, B. Kennett, S. Lebedev, B. Shan, U. Faul, and M. Qashqai for insightful discussions about, and contributions to, some of the concepts presented in this paper. The work of J.C.A. has been supported by two Australian Research Council Discovery grants (DP120102372 and DP110104145). Seismic data are from the IRIS DMS. D.L.S. acknowledges support from NSF grant EAR-135866. This is contribution 848 from the ARC Centre of Excellence for Core to Crust Fluid Systems (http://www.ccfs.mq.edu.au) and 1106 in the GEMOC Key Centre (http://www.gemoc.mq.edu.au).Peer reviewedPublisher PD

Criteria for the successful completion of medical dissertations – A multicenter study

Objective: In order to acquire the academic title “doctor” in Germany, it is essential to complete a dissertation. A high number of publications at German universities are based on medical dissertations. The reasons why some dissertations are successfully accomplished and why some are not completed – despite far-reaching consequences – have been barely investigated to date

Benefits and pitfalls of scientific research during undergraduate medical education

Objective: The integration of scientific research into medical education is a widely discussed topic. Most research training programs are offered on a voluntary basis. In Germany, it is mandatory to complete a doctoral thesis to obtain the academic title “doctor”. The reasons why students start a dissertation project and the influence of this project on their undergraduate studies and later career choices are not well known

Implementation of an innovative teaching project in a Chemical Process Design course at the University of Cantabria, Spain

This paper shows the planning, the teaching activities and the evaluation of the learning and teaching process implemented in the Chemical Process Design course at the University of Cantabria, Spain. Educational methods to address the knowledge, skills and attitudes that students who complete the course are expected to acquire are proposed and discussed. Undergraduate and graduate engineers' perceptions of the methodology used are evaluated by means of a questionnaire. Results of the teaching activities and the strengths and weaknesses of the proposed case study are discussed in relation to the course characteristics. The findings of the empirical evaluation shows that the excessive time students had to dedicate to the case study project and dealing with limited information are the most negative aspects obtained, whereas an increase in the students' self-confidence and the practical application of the methodology are the most positive aspects. Finally, improvements are discussed in order to extend the application of the methodology to other courses offered as part of the chemical engineering degree.This work was partially supported with the financial help of the University of Cantabria, 1st and 2nd Teaching Innovation Programs 2011-2012, 2013-2014, Projects Innodesign 1 and 2

Estudi sobre les hores més conflictives en un institut de secundària

Aquest Treball Final de Màster analitza la conflictivitat existent a les aules d'un institut de secundària. S'ha fet un estudi, amb dades reals de dos centres, sobre les incidències produïdes segons tres paràmetres que són la franja horària o hora lectiva, el curs i la matèria. Aquestes dades s'han representat i analitzat mitjançant taules i gràfics per poder fer una comparació. Els resultats obtinguts en els dos centres són sorprenentment coincidents pel que fa a conflictivitat per cursos i franges horàries, que es concentra al primer cicle i a la segona franja horària. Les diferències són una mica més grans pel que fa referència a les assignatures. Un cop identificada la franja horària més conflictiva del dia, s'ha dissenyat una proposta d'aplicació a l'aula relacionada amb tècniques de relaxació. Per desenvolupar la proposta s'ha fet un estudi de les tècniques existents a l'actualitat