Texas Technology University

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Texas Technology University

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Madhushani T.W.U.,Postgraduate and Research Unit | Maithripala D.H.S.,University of Peradeniya | Berg J.M.,Texas Technology University
Proceedings of the American Control Conference | Year: 2017

This paper applies geometric PID control for asymptotic tracking of a desired trajectory by a hoop robot in the presence of disturbances and uncertainties. The hoop robot, consisting of a circular body rolling without slip along a one-dimensional surface, is a planar analog of a spherical robot. A variety of coupled mechanical system may be used to actuate the hoop robot. This paper specifically considers two different actuators, one a simple pendulum and the other an internal cart. The geometric PID controller requires the plant to be a simple mechanical system, and the hoop robot does not satisfy this condition. Therefore a geometric inner loop is presented that gives the hoop robot the required structure. This procedure is here referred to as feedback regularization. Feedback regularization - in contrast to feedback linearization - is coordinate independent, and hence reflects the fundamental system structure. Note also that the resulting mechanical system is nonlinear and underactuated. Subsequently, the geometric PID outer loop guarantees almost-semiglobal tracking with locally exponential convergence, and the integral action of the PID guarantees robustness to constant disturbances and parameter uncertainties, including constant inclination of the rolling surface. The complete tracking controller is the composition of the two coordinate-independent loops, and therefore is also coordinate independent. © 2017 American Automatic Control Council (AACC).

Toledo L.N.,Pontifical Catholic University of Valparaíso | Salazar F.N.,Pontifical Catholic University of Valparaíso | Aquino A.J.A.,Texas Technology University
South African Journal of Enology and Viticulture | Year: 2017

The stabilisation of the proteinaceous material in the wine matrix represents one of the big challenges for the production of quality white wines, but the characterisation of the mechanism that governs the interactions between its components is still a very challenging goal. The aim of this study was to provide new information for developing new technologies in the stabilisation of bottled white wines using a novel theoretical approach. This method combines electronic structure calculations for the determination of the a stable conformation of three ligands that may interact with one of the proteins responsible for the haze in wines, the thaumatin-like protein (TLP), with the search for the mode of binding between this protein and its ligands through docking calculations. The result shows that sites that exposed positive residues to the surface of the protein are the sites favoured for the caffeic acid (CA) binding. Additionally, it was observed that the ligand with the lowest binding energy (-7.38 kcal/mol) was the quercetin (Q). The presence of a Π-Π stacking interaction with the residue F118 is confirmed in a family of TLP-Q complexes, and it is proposed that the mechanism of haze formation in white wines during bottle storage seems to be related to the interaction of polyphenolic molecules with some residues of this big cavity; these residues or sites of interaction can be considered as future targets in the control of the haze phenomena and in the research on alternatives to the fining treatment in the wine industry.

De Bruyn M.,Bangor University | Stelbrink B.,Humboldt University of Berlin | Morley R.J.,Royal Holloway, University of London | Morley R.J.,Palynova Ltd | And 15 more authors.
Systematic Biology | Year: 2014

Tropical Southeast (SE) Asia harbors extraordinary species richness and in its entirety comprises four of the Earth's 34 biodiversity hotspots. Here, we examine the assembly of the SE Asian biota through time and space. We conduct meta-analyses of geological, climatic, and biological (including 61 phylogenetic) data sets to test which areas have been the sources of long-term biological diversity in SE Asia, particularly in the pre-Miocene, Miocene, and Plio-Pleistocene, and whether the respective biota have been dominated by in situ diversification, immigration and/or emigration, or equilibrium dynamics. We identify Borneo and Indochina, in particular, as major "evolutionary hotspots" for a diverse range of fauna and flora. Although most of the region's biodiversity is a result of both the accumulation of immigrants and in situ diversification, within-area diversification and subsequent emigration have been the predominant signals characterizing Indochina and Borneo's biota since at least the early Miocene. In contrast, colonization events are comparatively rare from younger volcanically active emergent islands such as Java, which show increased levels of immigration events. Few dispersal events were observed across the major biogeographic barrier of Wallace's Line. Accelerated efforts to conserve Borneo's flora and fauna in particular, currently housing the highest levels of SE Asian plant and mammal species richness, are critically required. © The Author(s) 2014. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved.

Maithripala D.H.S.,University of Peradeniya | Berg J.M.,Texas Technology University
Proceedings of the IEEE Conference on Decision and Control | Year: 2014

This paper presents a PID controller for fully actuated, left-invariant, mechanical systems on a general Lie group. The class of problems solved includes tracking of a smoothly time-varying desired orientation for a rigid body with fully actuated attitude dynamics in two or three dimensions. If the reference velocity and unmodeled disturbance forces converge to constant values, then the closed-loop system will be almost-globally exponentially stable. The controller is robust to errors or variations in the inertial parameters and the actuator parameters. We explicitly construct the controller on the group of rigid body rotations and demonstrate its performance in quadrotor attitude tracking. © 2014 IEEE.

Maithripala D.H.S.,University of Peradeniya | Berg J.M.,Texas Technology University
Automatica | Year: 2015

This paper shows how "integral action" may be implemented intrinsically in the general setting of fully-actuated mechanical systems on Lie groups. When combined with an intrinsic formulation of PD control, integral action ensures that a suitably defined configuration tracking error will converge to zero in response to constant velocity commands and disturbance forces. Convergence is locally exponential and almost global, and is robust to bounded parametric uncertainty. For more general bounded commands and disturbances, the tracking error can be made arbitrarily small by choosing sufficiently large controller gains. A separation principle allows the addition of an intrinsic velocity observer to complete a geometric analog to the familiar output feedback PID controller for second-order linear systems. The controller extends naturally to accommodate tracking of equivariant output functions. The result is explicitly shown for the Lie group SO(3), and supported by simulations of a 6DOF quadrotor model. © 2015 Elsevier Ltd.

Hamilton K.R.,University of Maryland University College | Littlefield A.K.,Texas Technology University | Anastasio N.C.,University of Texas Medical Branch | Cunningham K.A.,University of Texas Medical Branch | And 10 more authors.
Personality Disorders: Theory, Research, and Treatment | Year: 2015

Impulsivity is a multifaceted construct that is a core feature of multiple psychiatric conditions and personality disorders. However, progress in understanding and treating impulsivity is limited by a lack of precision and consistency in its definition and assessment. Rapid-response impulsivity (RRI) represents a tendency toward immediate action that occurs with diminished forethought and is out of context with the present demands of the environment. Experts from the International Society for Research on Impulsivity (InSRI) met to discuss and evaluate RRI measures in terms of reliability, sensitivity, and validity, with the goal of helping researchers and clinicians make informed decisions about the use and interpretation of findings from RRI measures. Their recommendations are described in this article. Commonly used clinical and preclinical RRI tasks are described, and considerations are provided to guide task selection. Tasks measuring two conceptually and neurobiologically distinct types of RRI, "refraining from action initiation" (RAI) and "stopping an ongoing action" (SOA) are described. RAI and SOA tasks capture distinct aspects of RRI that may relate to distinct clinical outcomes. The InSRI group recommends that (a) selection of RRI measures should be informed by careful consideration of the strengths, limitations, and practical considerations of the available measures; (b) researchers use both RAI and SOA tasks in RRI studies to allow for direct comparison of RRI types and examination of their associations with clinically relevant measures; and (c) similar considerations be made for human and nonhuman studies in an effort to harmonize and integrate preclinical and clinical research. © 2015 American Psychological Association.

Reid R.C.,University of California at Los Angeles | Garos S.,Texas Technology University | Fong T.,University of California at Los Angeles
Journal of Behavioral Addictions | Year: 2012

Background and aims: The past decade has seen an increased interest in understanding hypersexual behavior and its associated features. Beyond the obvious risks for sexually transmitted infections, there is a paucity of literature examining specific challenges encountered by hypersexual individuals. This study investigated and developed a new scale, the Hypersexual Behavior Consequences Scale (HBCS), to assess the various consequences reported among hypersexual patients. Methods: Participants were drawn from a sample of patients recruited in a DSM-5 Field Trial for Hypersexual Disorder (HD). Participants completed the Hypersexual Behavior Inventory, a structured diagnostic interview to assess for psychopathology and HD, and self-report measures of personality, life satisfaction, and the initial item pool for the HBCS. Results: Factor analysis reduced the HBCS items to a single factor solution which showed high internal consistency and stability over time. Higher HBCS scores were positively correlated with higher levels of emotional dysregulation, impulsivity, and stress proneness and lower levels of satisfaction with life and happiness. HBCS scores among the hypersexual patients were significantly higher than non-hypersexual patients. Conclusions: The HBCS possesses good psychometric properties and appears to capture various consequences associated with the DSM-5 proposed criteria for HD. The HBCS can be used to aid clinicians and researchers in identifying consequences associated with hypersexual behavior. The HBCS may also prove a useful tool to guide treatment interventions aimed at reducing the negative impact of hypersexuality in patient populations. © 2012 Akadémiai Kiadó.

Zhang S.,China University of Petroleum - East China | Sheng J.J.,Texas Technology University | Qiu Z.,China University of Petroleum - East China
Journal of Petroleum Science and Engineering | Year: 2016

Polyamine (PA) is a novel inhibitor applied to water-based drilling fluid in order to reduce clay hydration. In this paper, water adsorption behavior on kaolinite and illite after PA adsorption (PA-kaolinite, PA-illite) was characterized by X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and adsorption isotherms tests using water, benzene, and heptane. After PA adsorption, water adsorption on kaolinite was enhanced while water adsorption on illite was reduced. Water vapor adsorption affinity on kaolinite in an entire range was significantly increased due to H-bonds between the ammonium groups of PA and water molecules. As a result, kaolinite surface tension was increased. Water adsorption affinity on illite in the low relative humidity (RH) regimes was decreased after PA adsorption and illite surface tension decreased because fewer water molecules could adsorb on tetrahedral (SiO4) of illite. Therefore, PA can be used as inhibitor while drilling shale formations mainly composed of illite, not kaolinite. © 2016 Elsevier B.V.

Hardin E.E.,University of Tennessee | Longhurst M.O.,Texas Technology University
Journal of Counseling Psychology | Year: 2016

Despite robust support for the basic theoretical model of social cognitive career theory (Lent, Brown, & Hackett, 1994) and predictions that, for example, increases (or declines) in self-efficacy would lead to subsequent increases (or declines) in interest, there has been surprisingly little longitudinal research that has directly examined the extent to which members of different groups (e.g., women and men) actually do experience changes in critical social- cognitive variables over time early in their curricula in the fields of science, technology, engineering, and mathematics (STEM). Knowing the extent to which such changes occur in typical introductory undergraduate courses is important for targeting interventions to increase persistence of underrepresented groups in STEM. We measured social-cognitive-career-theoryrelevant variables near the middle and at the end of the 1st semester of a gateway introductory chemistry course and found that women had lower STEM self-efficacy, coping self-efficacy, and STEM interest than did men, even after controlling for actual course performance. Although there were no detrimental changes across the semester for women or men, men experienced a small but significant increase in their perceived support for pursuing a STEM degree, whereas women did not. © 2015 American Psychological Association.

Peng Z.,Texas Technology University | Li C.,Texas Technology University
2015 IEEE MTT-S International Microwave Workshop Series on RF and Wireless Technologies for Biomedical and Healthcare Applications, IMWS-BIO 2015 - Proceedings | Year: 2015

A 24-GHz portable FMCW radar for short-range human tracking is designed, fabricated, and tested. The complete radar system weights 17.3 grams and has a dimension of 65mm×60mm×25mm. It has an on-board chirp generator, which generates a 45.7 Hz sawtooth signal to control the VCO. A 1.8GHz bandwidth ranging from 22.8 GHz to 24.6 GHz is transmitted. A pair of Vivaldi antennas with a bandwidth of 3.8 GHz, ranging from 22.5 GHz to 26.3 GHz, are implemented on the same board with the RF transceiver. A six-port structure is employed to down-convert the RF signal to baseband. Measurement result has validated its promising ability to for short-range human tracking. © 2015 IEEE.

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