System Level Synthesis

This article surveys the System Level Synthesis framework, which presents a novel perspective on constrained robust and optimal controller synthesis for linear systems. We show how SLS shifts the controller synthesis task from the design of a controller to the design of the entire closed loop system, and highlight the benefits of this approach in terms of scalability and transparency. We emphasize two particular applications of SLS, namely large-scale distributed optimal control and robust control. In the case of distributed control, we show how SLS allows for localized controllers to be computed, extending robust and optimal control methods to large-scale systems under practical and realistic assumptions. In the case of robust control, we show how SLS allows for novel design methodologies that, for the first time, quantify the degradation in performance of a robust controller due to model uncertainty -- such transparency is key in allowing robust control methods to interact, in a principled way, with modern techniques from machine learning and statistical inference. Throughout, we emphasize practical and efficient computational solutions, and demonstrate our methods on easy to understand case studies.Comment: To appear in Annual Reviews in Contro

Effect of problem-based learning on knowledge acquisition, knowledge retention, and critical thinking ability of agriculture students in urban schools

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on September 4, 2007)Vita.Includes bibliographical references.Thesis (Ph. D.) University of Missouri-Columbia 2007.Dissertations, Academic -- University of Missouri--Columbia -- Agricultural education.The purpose of this study was three-fold: to determine the effectiveness of instructional strategies on improving the acquisition and retention of leadership content by secondary students in urban agriculture programs; to examine the motivational profile of students who have elected to enroll in an urban agricultural program; and to examine the effect of instructional strategies [problem-based learning (PBL) and teacher-guided learning (TGL)] on critical thinking ability which includes the ability to acquire and use information and understand complex systems. A sample of 110 students from an agricultural magnet school was randomly assigned to learn leadership theories for two weeks using either PBL (n = 54) or TGL (n = 56). The sample's motivational profile indicated that students who had an influence in the decision to enroll in the agricultural school were more self-determined, more satisfied with the decision to attend, and reported exerting more effort during the study. Using ANCOVA to account for motivational differences, it was determined that students who had traditional instruction performed better on the knowledge test but retained less of the information they had learned. Furthermore, using ANCOVA to account for prior critical thinking ability, it was determined that no differences existed between the groups after treatment as measured by the WGCTA®. However, teacher and student reflection statements indicated an increase in the use of higher-order thinking skills and overall engagement by the students taught using the PBL instructional strategy

Effect of Problem-Based Learning on Knowledge Acquisition and Retention and Critical Thinking Ability of Agriculture Students in Urban Schools

The thesis from which this item is derived can be found at http://hdl.handle.net/10355/4832.Students at the Chicago High School for Agricultural Sciences enrolled as freshman in the Agricultural Careers and Leadership course participated in the study (n=110). The purpose of the study was to assess the effectiveness of instructional strategies on improving students' knowledge acquisition, knowledge retention, and critical thinking ability and to examine the motivational profile of students who chose to enroll in urban agriculture programs. The instructional strategies examined in the study were traditional Teacher Guided Learning and an experimental Problem Based Learning approach. Students in each group were given a prior knowledge unit test and Watson-Glasser Critical Thinking Appraisal pretest at the beginning of the study; followed by a knowledge retention unit test and WGTCA posttest at the end of the study

Shape and symmetry determine two-dimensional melting transitions of hard regular polygons

The melting transition of two-dimensional (2D) systems is a fundamental problem in condensed matter and statistical physics that has advanced significantly through the application of computational resources and algorithms. 2D systems present the opportunity for novel phases and phase transition scenarios not observed in 3D systems, but these phases depend sensitively on the system and thus predicting how any given 2D system will behave remains a challenge. Here we report a comprehensive simulation study of the phase behavior near the melting transition of all hard regular polygons with $3\leq n\leq 14$ vertices using massively parallel Monte Carlo simulations of up to one million particles. By investigating this family of shapes, we show that the melting transition depends upon both particle shape and symmetry considerations, which together can predict which of three different melting scenarios will occur for a given $n$. We show that systems of polygons with as few as seven edges behave like hard disks; they melt continuously from a solid to a hexatic fluid and then undergo a first-order transition from the hexatic phase to the fluid phase. We show that this behavior, which holds for all $7\leq n\leq 14$, arises from weak entropic forces among the particles. Strong directional entropic forces align polygons with fewer than seven edges and impose local order in the fluid. These forces can enhance or suppress the discontinuous character of the transition depending on whether the local order in the fluid is compatible with the local order in the solid. As a result, systems of triangles, squares, and hexagons exhibit a KTHNY-type continuous transition between fluid and hexatic, tetratic, and hexatic phases, respectively, and a continuous transition from the appropriate "x"-atic to the solid. [abstract truncated due to arxiv length limitations]

A Tension Shell Structure for Application to Entry Vehicles

The shape of a shell of revolution designed t o have only tensile stresses under axisymmetric aerodynamic loadings has been derived on the basis of linear membrane theory. values of circumferential tension is also given. The results of this paper indicate that the design of an entry vehicle based on the tension shell concept leads to desirable aerodynamic and structural characteristics, namely, high drag and low weight

Laser diffraction particle sizing: Instrument probe volume relocation and elongation

The effective probe volume of laser diffraction particle sizing instruments depends on many instrument parameters. In particular the probe volume axial boundaries and its location along laser beam are essentially defined by the onset of a vignetting effect where light scattered at large angles from small particles misses the transform lens. This vignetting effect results in a probe volume that must be inconveniently close to the lens in order to detect smaller diameter particles (less than 100 micrometers). With the addition of an appropriately designed Keplerian telescope, the probe volume may be relocated and elongated. The theory of operation of this supplemental optical system is described. Design considerations for these supplemental optical systems are described, including recommendations for lens specifications, assembly and use. An image transfer system is described which has been designed for use on a Malvern 2600HSD instrument. Experimental validation of this image transfer system is described

Economic Dimensions of Fees and Access Control under the Fishery Conservation and Management Act of 1976

This article is devoted to an analysis of how these new management tools can be used most effectively as applied to domestic and foreign fishermen