Constructing Parsimonious Analytic Models for Dynamic Systems via Symbolic Regression

Developing mathematical models of dynamic systems is central to many disciplines of engineering and science. Models facilitate simulations, analysis of the system's behavior, decision making and design of automatic control algorithms. Even inherently model-free control techniques such as reinforcement learning (RL) have been shown to benefit from the use of models, typically learned online. Any model construction method must address the tradeoff between the accuracy of the model and its complexity, which is difficult to strike. In this paper, we propose to employ symbolic regression (SR) to construct parsimonious process models described by analytic equations. We have equipped our method with two different state-of-the-art SR algorithms which automatically search for equations that fit the measured data: Single Node Genetic Programming (SNGP) and Multi-Gene Genetic Programming (MGGP). In addition to the standard problem formulation in the state-space domain, we show how the method can also be applied to input-output models of the NARX (nonlinear autoregressive with exogenous input) type. We present the approach on three simulated examples with up to 14-dimensional state space: an inverted pendulum, a mobile robot, and a bipedal walking robot. A comparison with deep neural networks and local linear regression shows that SR in most cases outperforms these commonly used alternative methods. We demonstrate on a real pendulum system that the analytic model found enables a RL controller to successfully perform the swing-up task, based on a model constructed from only 100 data samples

GIS Frameworks in the National Weather Service

Eugene Derner is a Senior Hydrologist for NOAA/National Weather Service at the Missouri Basin River Forecast Center. This presentation was given as part of the GIS Day@KU symposium on November 18, 2015. For more information about GIS Day@KU activities, please see http://www.gis.ku.edu/gisday/2015/.Platinum Sponsors: KU Department of Geography and Atmospheric Science; KU School of Business. Gold Sponsors: Bartlett & West; Kansas Biological Survey; KU Environmental Studies Program; KU Institute for Policy & Social Research; KU Libraries. Silver Sponsors: State of Kansas Data Access and Support Center (DASC). Bronze Sponsors: KU Center for Remote Sensing of Ice Sheets (CReSIS); TREKK Design Group, LLC; Wilson & Company, Engineers and Architects

Avaliação da produtividade da microalga Haematococcus pluvialis em diferentes meios de cultura

TCC (graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Agrárias. Curso de Engenharia de Aquicultura.Diversos estudos têm sido realizados com a microalga Haematococcus pluvialis devido ao seu potencial de produção do pigmento astaxantina, podendo acumular até 5% deste composto em termos de biomassa seca. Estudos relatam que este pigmento natural apresenta uma atividade biológica mais potente em comparação com outros carotenoides, alavancando o interesse da indústria farmacêutica, nutracêutica, cosmética e alimentícia. Por conta destas características, muitos estudos têm sido desenvolvidos justificando a produção comercial desta microalga. Para o cultivo de microalgas os nutrientes apresentem papel muito importante no crescimento e produção de biomassa, sendo este componente um item fundamental para a viabilidade econômica dos cultivos comerciais. O presente estudo teve como objetivo determinar o efeito de três diferentes meios de cultura (OHM, BBM e COMBO) no crescimento da microalga Haematococcus pluvialis. Os parâmetros de crescimento avaliados foram: densidade celular, biomassa máxima alcançada e produtividade. O meio de cultura que gerou a maior biomassa foi o BBM (0,57 g/l), seguido do OHM e COMBO com (0,47 g/l) e (0,36 g/l), respectivamente. Porém, com relação à produtividade, o emprego dos meios COMBO e BBM apresentou os melhores resultados, com 0,046 (g/l/d) e 0,044 (g/l/d) respectivamente, não havendo diferença estatística entre eles

Sex, Drugs, and Rodent Reward: An Exploration of the Sex-Specific Roles of Nicotinic Acetylcholine Receptors in Ethanol Reward

Alcohol, recently named the most dangerous drug in the world, contributes to nearly 40% of violent crimes and fatal traffic accidents, increases risk of roughly 60 different diseases and injuries, and is responsible for 2.5 million deaths each year worldwide. Despite these staggering figures, treatments remain ineffective and riddled with adverse side effects, making successful use of even the most effective treatments unlikely. Moreover, many of the treatments, and the supporting research, have focused only on male subjects, despite sex differences in various alcohol-related behaviors. Human alcohol use is frequently accompanied by nicotine use, and vice versa, suggesting a common mechanism of the two drugs. In fact, alcohol may act through the same family of receptors as nicotine, the nicotinic acetylcholine receptors (nAChRs), eliciting similar activation of the reward pathway as nicotine and other drugs of abuse. Studies have shown that nAChRs containing the α4 and/or α6 subunits are involved in nicotine-induced activation of the reward pathway, leading to the hypothesis that these same receptor subtypes may be important for alcohol effects in the brain as well. Using male and female genetic mouse models and various behavioral assays, we have shown not only that these α4 and/or α6-containing nAChRs are involved in alcohol- related behaviors and activation of the reward pathway, but also show sex differences in this involvement. Uncovering the mechanism of alcohol in the brain, in males as well as in females, is an important step in developing targeted treatments for alcohol abuse

Review and critical analysis: Rolling-element bearings for system life and reliability

A ball and cylindrical roller bearing technical specification which incorporates the latest state-of-the-art advancements was prepared for the purpose of improving bearing reliability in U.S. Army aircraft. The current U.S. Army aviation bearing designs and applications, including life analyses, were analyzed. A bearing restoration and refurbishment specification was prepared to improve bearing availability

Toward Physically Plausible Data-Driven Models: A Novel Neural Network Approach to Symbolic Regression

Many real-world systems can be described by mathematical models that are human-comprehensible, easy to analyze and help explain the system's behavior. Symbolic regression is a method that can automatically generate such models from data. Historically, symbolic regression has been predominantly realized by genetic programming, a method that evolves populations of candidate solutions that are subsequently modified by genetic operators crossover and mutation. However, this approach suffers from several deficiencies: it does not scale well with the number of variables and samples in the training data - models tend to grow in size and complexity without an adequate accuracy gain, and it is hard to fine-tune the model coefficients using just genetic operators. Recently, neural networks have been applied to learn the whole analytic model, i.e., its structure and the coefficients, using gradient-based optimization algorithms. This paper proposes a novel neural network-based symbolic regression method that constructs physically plausible models based on even very small training data sets and prior knowledge about the system. The method employs an adaptive weighting scheme to effectively deal with multiple loss function terms and an epoch-wise learning process to reduce the chance of getting stuck in poor local optima. Furthermore, we propose a parameter-free method for choosing the model with the best interpolation and extrapolation performance out of all the models generated throughout the whole learning process. We experimentally evaluate the approach on four test systems: the TurtleBot 2 mobile robot, the magnetic manipulation system, the equivalent resistance of two resistors in parallel, and the longitudinal force of the anti-lock braking system. The results clearly show the potential of the method to find parsimonious models that comply with the prior knowledge provided

Proposal to Creation the Investment Portfolio of the Hedge Fund

Tato bakalářská práce se zaměřuje na finanční analýzu největších amerických technologických společností. Teoretická část popisuje teoreticko-právní aspekty fungování fondů kvalifikovaných investorů a metody finanční analýzy použité v praktické části. Ta se skládá z prvotního výběru vhodných společností, které jsou následně analyzovány, porovnávány mezi sebou a verifikovány bankrotním modelem. V poslední kapitole je vypracováno investiční doporučení pro vytvoření portfolia fondu.This bachelor thesis is focused on financial analysis of the largest American technology companies. Theoretical part describes theoretical and legal aspects of the operation of qualified investors fund and methods of financial analysis used in the practical part. It consists of na initial selection of suitable companies, which are then analysed, compared between each other and verified by a bankruptcy model. In the last chapter, an investment recommendation for the creation of the funds portfolio is developed.

Ethical Limitations on Lawyer-to-Lawyer Online Consultations Regarding Pending Cases

This comment explains how and when lawyer-to-lawyer consultations are permitted in the online world. In all lawyer-to-lawyer consultations, but especially with the online variety, a lawyer must avoid violating the principle of confidentiality when consulting other lawyers about client matters. While in-person lawyer-to-lawyer consultations have been commonplace in the legal profession for decades, the rise of listservs and social media networks has caused many lawyers to seek advice from colleagues on the Internet. In considering online lawyer-to-lawyer consultations, there are two major issues. Firstly, a lawyer must determine whether the jurisdiction in which he or she practices permits online lawyer-to-lawyer consultations; while several jurisdictions that have addressed their use have answered in the affirmative, the associated ethical boundaries are not yet clearly drawn. Secondly, a lawyer must consider what types of information can be shared over the course of a lawyer-to-lawyer consultation—reviewing jurisdictions have indicated that a limited amount of client information can be shared, and the use of abstractions/generalities is encouraged to ensure that the attorney-client privilege is not inadvertently destroyed. This comment addresses the ethical limitations on what lawyers may share online for the purpose of advancing client interests; the authorities and arguments presented herein are timely, and will only become more important as the legal profession continues into the Internet age

Ivšić's contribution to linguistic Croatistics

Iako je početkom 20. stoljeća hrvatski jezik potiskivan na različite načine, svoj doprinos u to vrijeme dao mu je jedan od važnijih jezikoslovaca Stjepan Ivšić. U ovome radu osvrnut ću se na njegovu biografiju, prve priloge, važne radove te doprinose jezikoslovnoj znanosti. Također ću dati interpretaciju nekoliko njegovih rasprava i članaka koje se tiču pravopisnih pitanja, ali obuhvaćaju isto tako drugačije interese njegova proučavanja, kao što je i ćirilometodska baština