Virtual Taxila: A Web-Accessible, Multi-User Virtual Environment (MUVE) of an Ancient Indian City

The Virtual Taxila project will develop a web-accessible, 3D, immersive, multi-user virtual environment (MUVE), where visitors will engage in situated, participatory learning about ancient Indian culture. The project will focus on the archaeological site of Taxila, the ancient capital of western Punjab and now an UNESCO World Heritage site located in Pakistan. Taxila was inhabited c. 500 BCE to c. 700 CE, but the project will model the city as it stood at circa 1 CE. The model will include both the city's tangible heritage (the built environment and the physical artifacts) and its intangible heritage (the people and their rituals, commercial transactions, and work activities). Virtual Taxila will create a "situated" community of practice, where visitors will be immersed in the historical context about which they learn. By logging in online, visitors will be able to interact with computer controlled characters that will act as guides, providing them with an insider's experience

Instability zones for isotropic and anisotropic multibladed rotor configurations.

Helicopter ground resonance is an unstable dynamic phenomenon which can lead to the total destruction of the aircraft during take-off or landing phases. The earliest research in this domain was carried out by Coleman and Feingold during the decade of 60s. The instability was predicted by using classical procedures once the rotor was considered as isotropic, consequently, the periodic equations of motion could be simplified to a system with constant coefficients by introducing a change of variables, known as the Coleman Variable Transformation. The goal of the present work is to further comprehend the phenomenon and the influence of the anisotropic properties of rotors by analyzing the periodic set of equations of motion. For this, Floquet's Theory (Floquet's Method — FM) is used. The analysis for predicting the ground resonance phenomenon in isotropic and anisotropic rotor configurations is explored. The conclusions lead to verify the appearance of bifurcation points depending on the anisotropic characteristic present in the rotor. The temporal response analysis in the motion of helicopter with one asymmetric blade at unstable regions highlighted the presence of non symmetric rotor deformation shapes

Robustness Analysis of Helicopter Ground Resonance with Parametric Uncertainties in Blade Properties

This paper presents a stability robustness analysis of the helicopter ground-resonance phenomenon. By using the lifting procedure the uncertain linear-time-periodic model of the helicopter is transformed into an augmented uncertain linear-time-invariant model that allows the application of μ-analysis tools. The lifting procedure involves a periodic switching linear-time-invariant piecewise model computed using oversampling of the system period. The representativeness of the lifted model for various oversampling period values and methods is discussed and compared with a Floquet analysis for several parametric discretization configurations. A μ-analysis is then applied to find the worst-case parametric configuration for a given rotor angular rate. The parametric uncertainties taken into account are the dynamic characteristics (stiffness and damping) of each blade hinge. A significant advantage of the proposed approach is that it enables performing ground-resonance analysis for a rotor with dissimilar blade properties due to aging effects. Considering uncertainties on the four blade hinge stiffnesses and damping factors, the μ-analysis performed on the lifted model leads to the conclusion that the worst case for degraded rotor stability corresponds to the symmetric perturbation of all the blades

Modélisation dynamique d’un rotor sur base flexible.

On s’intéresse dans cette étude à la modélisation dynamique d’un rotor sur base flexible afin de mettre en évidence le phénomène de résonance du sol rencontré sur certains hélicoptères, générant des instabilités pouvant conduire à sa destruction

Instability zones identification in multiblade rotor dynamics

Helicopter ground resonance is an unstable dynamic phenomenon which can lead to the total destruction of the aircraft during take-off or landing phases. Studies have been developed by researchers which considered a simplified mathematical model. With the goal of further comprehend the phenomenon, predictions of unstable motions are done and compared. First, Floquet's theory is applied to solve the linear equations of motion including parametric and periodic terms. Then, the multiple scales method is applied on the nonlinear model. The analyses highlight that, by keeping the nonlinear terms in the equations, other instability zones are identified

Screening for distress in pediatric cancer survivors : a systematic comparison of one-step and two-step strategies to minimize detection errors

Background:Childhood cancer survivors should be routinelyscreened for psychological distress. However, existing screeningtools promoted by cancer care institutions, such as the DistressThermometer (DT) generate high rates of errors. The aim of thisstudy is to help refining strategies of screening psychologicaldistress in this population by exploring two-step methods com-bining the DT on step #1 with one question on step #2.Procedure:Data from 255 survivors of childhood acutelymphoblastic leukemia aged 13–40years were analyzed (38%13–18 years, 62% 19þyears, 53% females). We used the DTon step #1 and the individual emotion items from thePediatric Quality of Life Questionnaire (PedsQL) on step #2, todetect distress, depression and anxiety as measured by stand-ard instruments. We compared sensitivity, specificity, negativeand positive predictive values, Youden index, and clinical util-ity indices, in newly developed two-step strategies.Results:The best two-step strategies to screen anxious-depressive distress were DT 2 on step #1, with the item ofSadness on step #2, and DT 2 combined with the item ofConcerns. Two-step strategies outperformed the DT alone onthe correct identification of distressed survivors. However,two-step strategies did not outperform the DT used alone onthe correct detection of no distressed survivors. Results weresimilar when predicting depression or anxiety alone.Conclusion:Completing the DT with one single question onemotions from the PedsQL may minimize the number of par-ticipants falsely identified as distressed, which could be par-ticularly pertinent in resource-limited clinics

Psychological risk in long-term survivors of childhood acute lymphoblastic leukemia and its association with functional health status : A PETALE cohort study

Background: Recent research has suggested that long-term pediatric cancer survivors were at risk of important physical and psychological morbidities. To date, we do not know to what extent functional health status contributes to psychological risk and which domains are most important. The aim of this study was to systematically explore which functional domain could explain anxiety, depression, and distress symptoms. Procedure: We used data available for 105 adolescents and 182 adults successfully treated for childhood acute lymphoblastic leukemia at two Canadian sites part of the PETALE cohort. Participants were ≥5 years postdiagnosis, aged 22 ± 6 years, 52% female, and 49% acute lymphoblastic leukemia high-risk status. The contribution of health functional status (15D/16D questionnaires) to self-reported anxiety, depression, and distress (Beck scales and distress thermometer) was evaluated using adjusted logistic regression models. Results: Prevalence rates found for mild-severe anxiety, depression, and distress were 14%, 21%, and 30% among adolescents and 27%, 20%, and 19% among adults. Frequent health domains associated with psychological risk were sleeping and breathing in adolescents, and vitality/fatigue, discomfort/symptoms, mental function, and sleeping in adults. Mental function was systematically associated with psychological risk across age groups (median OR = 10.00, 95% CI 3.01-33.71). Exploratory mediation bootstrapping analyses suggested that the effect on psychological risk of overall health status and mental function problems was partly explained by social/work/school functioning. Conclusion: The results identified important functional health domains that could be targeted for interventions preventing psychological risk: vitality/fatigue, discomfort/symptoms, sleeping, and mental function issues. Health domains probably affect mood partly by limiting social/work/school functioning

Inconsistencies between measures of cognitive dysfunction in childhood acute lymphoblastic leukemia survivors : description and understanding

Objectives The frequency of cognitive difficulties in childhood cancer survivors varies according to the measurement strategy. The goal of this research is to (a) describe agreements and differences between measures of working memory and attention (b) identify contributors of these differences, such as emotional distress, affects, and fatigue. Methods We used data available for 138 adults successfully treated for childhood acute lymphoblastic leukemia (ALL) (PETALE cohort). Working memory and attention were assessed using subtests from the WAIS‐IV and self‐reported questionnaires (BRIEF‐SR and CAARS‐S:L). Potential contributors included emotional distress, anxiety, depression (BSI‐18), affects (PANAS), and fatigue (PedsQL‐MFS). We explored measurement agreements and differences using diagnostic indices and multivariate regression models. Results The frequencies of working memory and attention deficits were higher when using cognitive tests (15%‐21%) than with self‐reports (10%‐11%). Self‐reported questionnaires showed high specificity (median 0.87) and low sensitivity (median 0.10), suggesting they did not reliably identify positive cases on cognitive tests. We identified negative affectivity as a possible contributor to inconsistencies between self‐report and test results. Conclusions When measuring working memory and attention in childhood ALL survivors, cognitive test results and self‐reports should not be considered equivalent. At best, self‐report may be used for screening (high specificity), but not to assess prevalence in large samples. Self‐reported difficulties are also probably influenced by the negative mood in this population