331 research outputs found
Design and Development of Laboratory Single-Axis PV Module Tracker
Solar energy is an integral part of the renewable energy industry. Advanced solar farms actively track solar movement and update solar panel angles to maximize the systemâs output power. Cal Poly boasts its own Solar Farm that features a single-axis tracking system. Single-axis tracking aims to get panels as close to perpendicular as possible given the panel arrangements and given the time of year. Single-axis tracking is a more robust measurement and tracking option. Single-axis tracking systems usually only have East-West panel arc movement, following the sunâs rotation. Dual-axis trackers have both East-West and North-South panel arc movements. Dual-axis systems have the ability to shift their North-South angle to better face the sun as the seasons change, based on GPS location. Solar panels generate the most power when receiving the highest light intensity. Single-axis systems generally cost less than Dual-axis. One less axis of motion translates to fewer mechanical parts, fewer motor controllers, and ultimately a more durable system. To account for the inability to directly face the sun year round, students will study how to eliminate inter-row shading between panels to maximize power production.
To observe and improve the single-axis tracking system, a laboratory model of the solar farm will be created. Identical solar panels to the Cal Poly panels will be integrated with a solar tracking embedded system. The system will be tested on available test panels in conjunction with a specialized angle tracking measurement network. Students will alter and study the system, accommodating for variables that are not accounted for in the current static algorithm. The new testing system will allow students to study the issues present in the farm and to develop a proposal to improve the power production performance at the farm. In addition, students will learn the fundamentals of single-axis tracking. The laboratory model will be adaptable regardless of the location and terrain of the solar farm, and will tilt the panels in the most optimal angle for the network of arrays in a typical farm
Revealing the dynamic modulations that underpin a resilient neural network for semantic cognition:An fMRI investigation in patients with anterior temporal lobe resection
Tense marking in children with autism
A recent large-scale study identified a subgroup of children with autism who had a language profile similar to that found among children with specific language impairment (SLI). including difficulties with nonsense word repetition, an ability that has been implicated as one clinical marker for SLI. A second clinical marker for English-speaking children with SLI is high rates of omission of grammatical morphemes that mark tense in obligatory contexts. This study used experimental probes designed to elicit third person and past tense morphology with a large heterogeneous sample of children with autism. The subgroup of children with autism who were language impaired showed high rates of omission of tense marking on the experimental tasks. in addition, some of the children with autism made performance errors that were specific to the autistic population, such as echolalia. These findings further refine the characteristics of language impairment found in a subgroup of children with autism
A theoretical investigation of the low lying electronic structure of poly(p-phenylene vinylene)
The two-state molecular orbital model of the one-dimensional phenyl-based
semiconductors is applied to poly(p-phenylene vinylene). The energies of the
low-lying excited states are calculated using the density matrix
renormalization group method. Calculations of both the exciton size and the
charge gap show that there are both Bu and Ag excitonic levels below the band
threshold. The energy of the 1Bu exciton extrapolates to 2.60 eV in the limit
of infinite polymers, while the energy of the 2Ag exciton extrapolates to 2.94
eV. The calculated binding energy of the 1Bu exciton is 0.9 eV for a 13
phenylene unit chain and 0.6 eV for an infinite polymer. This is expected to
decrease due to solvation effects. The lowest triplet state is calculated to be
at ca. 1.6 eV, with the triplet-triplet gap being ca. 1.6 eV. A comparison
between theory, and two-photon absorption and electroabsorption is made,
leading to a consistent picture of the essential states responsible for most of
the third-order nonlinear optical properties. An interpretation of the
experimental nonlinear optical spectroscopies suggests an energy difference of
ca. 0.4 eV between the vertical energy and ca. 0.8 eV between the relaxed
energy, of the 1Bu exciton and the band gap, respectively.Comment: LaTeX, 19 pages, 7 eps figures included using epsf. To appear in
Physical Review B, 199
Defining language impairments in a subgroup of children with autism spectrum disorder
Autism spectrum disorder (ASD) is diagnosed on the basis of core impairments in pragmatic language skills, which are found across all ages and subtypes. In contrast, there is significant heterogeneity in language phenotypes, ranging from nonverbal to superior linguistic abilities, as defined on standardized tests of vocabulary and grammatical knowledge. The majority of children are verbal but impaired in language, relative to age-matched peers. One hypothesis is that this subgroup has ASD and co-morbid specific language impairment (SLI). An experiment was conducted comparing children with ASD to children with SLI and typically developing controls on aspects of language processing that have been shown to be impaired in children with SLI: repetition of nonsense words. Patterns of performance among the children with ASD and language impairment were similar to those with SLI, and contrasted with the children with ASD and no language impairment and typical controls, providing further evidence for the hypothesis that a subgroup of children with ASD has co-morbid SLI. The findings are discussed in the context of brain imaging studies that have explored the neural bases of language impairment in ASD and SLI, and overlap in the genes associated with elevated risk for these disorders.M01 RR00533 - NCRR NIH HHS; R01 DC10290 - NIDCD NIH HHS; U19 DC03610 - NIDCD NIH HH
Weak chaos detection in the Fermi-Pasta-Ulam- system using -Gaussian statistics
We study numerically statistical distributions of sums of orbit coordinates,
viewed as independent random variables in the spirit of the Central Limit
Theorem, in weakly chaotic regimes associated with the excitation of the first
() and last () linear normal modes of the Fermi-Pasta-Ulam-
system under fixed boundary conditions. We show that at low energies
(), when the linear mode is excited, chaotic diffusion occurs
characterized by distributions that are well approximated for long times
() by a -Gaussian Quasi-Stationary State (QSS) with .
On the other hand, when the mode is excited at the same energy, diffusive
phenomena are \textit{absent} and the motion is quasi-periodic. In fact, as the
energy increases to , the distributions in the former case pass through
\textit{shorter} -Gaussian states and tend rapidly to a Gaussian (i.e.
) where equipartition sets in, while in the latter we need to
reach to E=4 to see a \textit{sudden transition} to Gaussian statistics,
without any passage through an intermediate QSS. This may be explained by
different energy localization properties and recurrence phenomena in the two
cases, supporting the view that when the energy is placed in the first mode
weak chaos and "sticky" dynamics lead to a more gradual process of energy
sharing, while strong chaos and equipartition appear abruptly when only the
last mode is initially excited.Comment: 12 pages, 3 figures, submitted for publication to International
Journal of Bifurcation and Chaos. In honor of Prof. Tassos Bountis' 60th
birthda
Parental phonological memory contributes to prediction of outcome of late talkers from 20 months to 4 years: a longitudinal study of precursors of specific language impairment
Background Many children who are late talkers go on to develop normal language, but others go on to have longer-term language difficulties. In this study, we considered which factors were predictive of persistent problems in late talkers. Methods Parental report of expressive vocabulary at 18 months of age was used to select 26 late talkers and 70 average talkers, who were assessed for language and cognitive ability at 20 months of age. Follow-up at 4 years of age was carried out for 24 late and 58 average talkers. A psychometric test battery was used to categorize children in terms of language status (unimpaired or impaired) and nonverbal ability (normal range or more than 1 SD below average). The vocabulary and non-word repetition skills of the accompanying parent were also assessed. Results Among the late talkers, seven (29%) met our criteria for specific language impairment (SLI) at 4 years of age, and a further two (8%) had low nonverbal ability. In the group of average talkers, eight (14%) met the criteria for SLI at 4 years, and five other children (8%) had low nonverbal ability. Family history of language problems was slightly better than late-talker status as a predictor of SLI.. The best predictors of SLI at 20 months of age were score on the receptive language scale of the Mullen Scales of Early Learning and the parent's performance on a non-word repetition task. Maternal education was not a significant predictor of outcome. Conclusions In this study, around three-quarters of late talkers did not have any language difficulties at 4 years of age, provided there was no family history of language impairment. A family history of language-literacy problems was found to be a significant predictor for persisting problems. Nevertheless, there are children with SLI for whom prediction is difficult because they did not have early language delay
The medical student
The Medical Student was published from 1888-1921 by the students of Boston University School of Medicine
Frontotemporal lobar degeneration and social behaviour:Dissociation between the knowledge of its consequences and its conceptual meaning
Endovascular Thrombectomy for Ischemic Stroke Increases Disability-Free Survival, Quality of Life, and Life Expectancy and Reduces Cost
Background: Endovascular thrombectomy improves functional outcome in large vessel occlusion ischemic stroke. We examined disability, quality of life, survival and acute care costs in the EXTEND-IA trial, which used CT-perfusion imaging selection. Methods: Large vessel ischemic stroke patients with favorable CT-perfusion were randomized to endovascular thrombectomy after alteplase versus alteplase-only. Clinical outcome was prospectively measured using 90-day modified Rankin scale (mRS). Individual patient expected survival and net difference in Disability/Quality-adjusted life years (DALY/QALY) up to 15 years from stroke were modeled using age, sex, 90-day mRS, and utility scores. Level of care within the first 90 days was prospectively measured and used to estimate procedure and inpatient care costs (US15,689 versus US10,515). The average saving per patient treated with thrombectomy was US$4,365. c Conclusion: Thrombectomy patients with large vessel occlusion and salvageable tissue on CT-perfusion had reduced length of stay and overall costs to 90 days. There was evidence of clinically relevant improvement in long-term survival and quality of life.Peer reviewe
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