11 research outputs found
A Posteriori Multistage Optimal Trading under Transaction Costs and a Diversification Constraint
No full textReference trajectory planning under constraints and path tracking using linear time-varying model predictive control for agricultural machines
No full textA method for the control of autonomously and slowly moving agricultural machinery is presented. Special emphasis is on offline reference trajectory generation tailored for high-precision closed-loop tracking within agricultural fields using linear time-varying model predictive control. When optimisation is carried out, high-level logistical processing can result in edgy reference paths for field coverage. Subsequent trajectory smoothing can consider specific actuator rate constraints and field geometry. The latter step is the subject of this paper. Focussing on forward motion only, the role of non-convexly shaped field geometry, repressed area minimisation and spraying gap avoidance is analysed. Three design methods for generating smooth reference trajectories are discussed: circle-segments, generalised elementary paths, and bi-elementary paths
Evidence from diatom-bound nitrogen isotopes for subarctic Pacific stratification during the last ice age and a link to North Pacific denitrification changes
No full textAuthor Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 22 (2007): PA1215, doi:10.1029/2005PA001205.In a piston core from the central Bering Sea, diatom microfossil-bound N isotopes and the concentrations of opal, biogenic barium, calcium carbonate, and organic N are measured over the last glacial/interglacial cycle. Compared to the interglacial sections of the core, the sediments of the last ice age are characterized by 3‰ higher diatom-bound δ 15N, 70 wt % lower opal content and 1200 ppm lower biogenic barium. Taken together and with constraints on sediment accumulation rate, these results suggest a reduced supply of nitrate to the surface due to stronger stratification of the upper water column of the Bering Sea during glacial times, with more complete nitrate consumption resulting from continued iron supply through atmospheric deposition. This finding extends the body of evidence for a pervasive link between cold climates and polar ocean stratification. In addition, we hypothesize that more complete nutrient consumption in the glacial age subarctic Pacific contributed to the previously observed ice age reduction in suboxia and denitrification in the eastern tropical North Pacific by lowering the nutrient content of the intermediate-depth water formed in the subpolar North Pacific. In the deglacial interval of the Bering Sea record, two apparent peaks in export productivity are associated with maxima in diatom-bound and bulk sediment δ 15N. The high δ 15N in these intervals may have resulted from greater surface nutrient consumption during this period. However, the synchroneity of the deglacial peaks in the Bering Sea with similar bulk sediment δ 15N changes in the eastern Pacific margin and the presence of sediment lamination within the Bering Sea during the deposition of the productivity peaks raise the possibility that both regional and local denitrification worked to raise the δ 15N of the nitrate feeding Bering Sea surface waters at these times.Financial support for this work was provided by
NSF grants OCE-0136449, OCE-9981479, ANT-0453680, by BP and Ford
Motor Company through the Princeton Carbon Migration Initiative, and by
a NDSEG fellowship to B.G.B. Work conducted aboard the USCG Healy
(Healy 0202) was funded by grant OPP-9912122
Spatial-based predictive control and geometric corridor planning for adaptive cruise control coupled with obstacle avoidance
No full textLanguage, Motor Ability and Related Deficits in Children at Familial Risk of Schizophrenia or Bipolar Disorder
No full textIt is known that impairments in linguistic ability and motor function tend to co-occur in children, and that children from families with parental mental illness such as schizophrenia tend to perform poorly in both domains, but the exact nature of these links has not yet been fully elucidated.
In this study, we leveraged the first wave of the Danish High Risk and Resilience Study (VIA 7), which includes both genetic data and measures covering multiple developmental domains. The VIA 7 cohort comprises 522 7-year-old children born to parents with schizophrenia (N = 202), bipolar disorder (N = 120) or neither (N = 200). We investigated the relationships between linguistic ability and motor function using correlation and regression analyses, focusing on developmental coordination disorder (DCD) and specific language impairment (SLI) and their potential associations with the three risk groups.
We found significant correlations between most measures of language and motor function and significant associations of DCD and SLI with language and movement measures, respectively, the largest effect being that of DCD on receptive language, with a significant interaction effect: DCD was associated with poorer performance in children from schizophrenia families compared to bipolar disorder and control families. Both disorders showed higher prevalence among children with familial high risk of mental illness. We did not find significant evidence of genetic overlap between DCD and SLI.
Our results suggest strong links between the domains of motor function and linguistic ability. Children of parents with schizophrenia are at high risk of comorbid language and movement disorders.
© The Author(s) 2024. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center
The ADVANCE toolkit: Automated descriptive video annotation in naturalistic child environments
No full textVideo recordings are commonplace for observing human and animal behaviours, including interindividual interactions. In studies of humans, analyses for clinical applications remain particularly cumbersome, requiring human-based annotation that is time-consuming, bias-prone, and cost-ineffective. Attempts to use machine learning to address these limitations still oftentimes require highly standardised environments, scripted scenarios, and forward-facing individuals. Here, we provide the ADVANCE toolkit, an automated video annotation pipeline. The versatility of ADVANCE is demonstrated with schoolchildren and adults in an unscripted clinical setting within an art classroom environment that included 2-5 individuals, dynamic occlusions, and large variations in actions. We accurately detected each individual, tracked them simultaneously throughout the duration of the recording (including when an individual left and re-entered the field of view), estimated the position of their skeletal joints, and labelled their poses. By resolving challenges of manual annotation, we radically enhance the ability to extract information from video recordings across different scenarios and settings. This toolkit reduces clinical workload and enhances the ethological validity of video-based assessments, offering scalable solutions for behaviour analyses in naturalistic contexts.
© 2025. The Author(s)
The Multidimensional Anxiety Scale for Children : a further validation with Australian adolescents with and without ADHD
No full textTo examine the factor structure of the Multidimensional Anxiety Scale for Children (MASC) with Australian adolescents with and without Attention–Deficit/Hyperactivity Disorder (ADHD). The MASC was administered to 210 high school aged adolescents (109 males, 101 females), 115 of who were clinically diagnosed as ADHD (86 males, 29 females). The remaining 95 were non ADHD Community Comparisons. Results: Analyses supported a three-factor model, with a reduced item pool, which combined the Harm Avoidance and Separation Anxiety scales together. This model was invariant across younger and older participants, and across boys and girls. The model was largely invariant across ADHD and non-ADHD groups. The ADHD group had significantly higher Physical Symptom factor scores than the non-ADHD group. The MASC is useful for assessing anxiety in adolescents with and without ADHD but items reflecting the Harm Avoidance and Separation Anxiety scales may need revising
Hemispheric dissociation and dyslexia in a computational model of reading
No full textThere are several causal explanations for dyslexia, drawing on distinctions between dyslexics and control groups at genetic, biological, or cognitive levels of description. However, few theories explicitly bridge these different levels of description. In this paper we review a long-standing theory that some dyslexics’ reading impairments are due to impairments in hemispheric transfer. We test this theory in a computational model of reading, implementing anatomical features of the visual system. We demonstrate that, when callosal transfer is impaired, the model reads nonwords as well as an unimpaired model, but reads exception words poorly: a pattern of behaviour similar to surface dyslexia. This computational modelling provides a causal link between brain-based theories of dyslexia to cognitive-level theories that refer specifically to phonological impairments within the reading system
Microresonators for organic semiconductor and fluidic lasers
No full textThis thesis describes a number of studies of microstructured optical resonators,
designed with the aim of enhancing the performance of organic semiconductor lasers
and exploring potential applications. The methodology involves the micro-engineering
of the photonic environment in order to modify the pathways of the emitted light and
control the feedback mechanism. The research focuses on designing new organic
microstructures using established semi-analytical and numerical methods, developing fabrication techniques using electron-beam lithography, and optically characterising the resulting structures.
Control of the feedback mechanism in conjugated polymer lasers is first investigated by studying Distributed Feedback or photonic crystal resonators based on a square feedback lattice. This study identified the diffraction to free space radiation as a major source of loss in current microstructured resonator designs. By cancelling the coupling to free space through the use of different feedback symmetries and diffraction orders, a threshold reduction by almost an order of magnitude is demonstrated.
The introduction of mid-gap defect photonic states in an otherwise uniformly periodic
structure was studied in Distributed Bragg Reflector (DBR) resonators. This enabled
GaN diode pumped polymer lasers to be demonstrated, indicating that the transition
from complex excitation sources to more compact systems is possible. Devices for
potential applications in the field of optical communications are also explored by
demonstrating a polymer DBR laser based on silicon. In this way, the potential for
integrating conjugated polymers with silicon photonics is confirmed.
Photonic crystal fibres, which have a periodic microstructure in the transverse
direction, are explored as an alternative means for controlling the optical properties of organic lasers. Fluidic fibre organic lasers were demonstrated as efficient sources with good spectral purity. In these devices, mechanisms to tune the emission wavelength
were explored and the origin of the frequency selection mechanism was investigated.The author received a Wingate Scholarship for the Si experiments
