Literatura científica selecionada sobre o tema "TFLES"

Abstract OBJECTIVE: The objective of this study was to evaluate the clinical significance of the transforaminal ligaments (TFLs) in relation to the area of the lumbar intervertebral foramen (IVF) by analyzing cadaveric spines. METHODS: One hundred ninety-eight cadaveric lumbar IVFs were studied, and the existence and type of TFLs were identified. All IVFs were photographed, and the images were saved. The areas of the IVFs and TFLs were measured with the Scion Image for Windows image analysis program. RESULTS: TFLs were found in 82.8% of the IVFs. The oblique inferior transforaminal ligament was the most common. The mean area of the IVFs was 155.8 ± 51.1 mm2, and the mean area occupied by the TFLs was 46.3 ± 37.6 mm2. The mean percentage of the IVF area occupied by the TFLs was 28.5 ± 18.8%. CONCLUSION: TFLs are common structures in the IVF and may reduce the space available for the spinal nerve root within the IVF. In this circumstance, any compromise of the IVF may impinge on the nerve root.

Objective:Cerebral amyloid angiopathy (CAA) is a common age-related small vessel disease (SVD). Patients without intracerebral hemorrhage (ICH) typically present with transient focal neurologic episodes (TFNEs) or cognitive symptoms. We sought to determine if SVD lesion burden differed between patients with CAA first presenting with TFNEs vs cognitive symptoms.Methods:A total of 647 patients presenting either to a stroke department (n = 205) or an outpatient memory clinic (n = 442) were screened for eligibility. Patients meeting modified Boston criteria for probable CAA were included and markers of SVD were quantified, including cerebral microbleeds (CMBs), perivascular spaces, cortical superficial siderosis (cSS), and white matter hyperintensities (WMHs). Patients were classified according to presentation symptoms (TFNEs vs cognitive). Total CAA-SVD burden was assessed using a validated summary score. Individual neuroimaging markers and total SVD burden were compared between groups using univariable and multivariable models.Results:There were 261 patients with probable CAA included. After adjustment for confounders, patients first seen for TFNEs (n = 97) demonstrated a higher prevalence of cSS (p < 0.0001), higher WMH volumes (p = 0.03), and a trend toward higher CMB counts (p = 0.09). The total SVD summary score was higher in patients seen for TFNEs (adjusted odds ratio per additional score point 1.46, 95% confidence interval 1.16–1.84, p = 0.013).Conclusions:Patients with probable CAA without ICH first evaluated for TFNEs bear a higher burden of structural MRI SVD-related damage compared to those first seen for cognitive symptoms. This study sheds light on neuroimaging profile differences across clinical phenotypes of patients with CAA without ICH.

<abstract><p>The 1D and 2D spatial compact finite difference schemes (CFDSs) for time-fractional diffusion equations (TFDEs) were presented in this article with uniform temporal convergence order. Based on the idea of the modified block-by-block method, the CFDSs with uniform temporal convergence order for TFDEs were given by combining the fourth-order CFDSs in space and the high order scheme in time. The stability analysis and convergence order of CFDSs with uniform convergence order in time for TFDEs strictly proved that the provided uniform accuracy time scheme is $ (3-\alpha) $ temporal order and spatial fourth-order, respectively. Ultimately, the astringency of 1D and 2D spatial CFDSs was verified by some numerical examples.</p></abstract>

Objective:The Texas Functional Living Scale (TFLS) is a measure of adaptive functioning commonly utilized across the geriatric population. Current research suggests that those with Alzheimer’s disease and other dementias perform poorly on the TFLS, compared to those with mild cognitive impairment (MCI) and normal cognition (Cullum et al., 2001). Additional research is needed to examine the influence anxiety and depressive symptoms have on activities of daily living (ADLS) in individuals being evaluated for memory disorders. This study will examine the effects of anxiety and depression on adaptive functioning across all patients, and within samples of those with dementia and MCI. It is hypothesized that higher reported anxiety and depressive symptoms will predict lower scores of ADLS.Participants and Methods:Patients at a memory disorder clinic (N = 756; 58.2% female) were screened for cognitive impairment using the Montreal Cognitive Assessment (MoCA). A brief neuropsychological evaluation (BNE) was then conducted in which the TFLS, Geriatric Depression Scale (GDS), and Geriatric Anxiety Inventory (GAI) were administered, among other measures.Results:A stepwise hierarchical regression was conducted on the entire sample to examine the effects of anxiety and depressive symptoms on TFLS performance, controlling for cognitive impairment using the MoCA. Lower MoCA scores explained a significant amount of variance in TFLS performance (R2 = 0.456, F(1, 754) = 632.78, p < .001). MoCA scores (b = 1.27, p < .001), the GAI (b = 0.14, p = .019), and the GDS (b = 0.10, p = 0.039) were significant predictors of poor TFLS performance across the entire sample. Although the MoCA, GDS, and GAI were each significant predictors of the TFLS, the increased variance explained by the GDS and GAI individually was incremental (AR2 = 0.003, F(1, 752) = 3.90, p = .049). Stepwise hierarchical regressions were also conducted on subsamples diagnosed with MCI (N = 171) and dementia (N = 394). For those with MCI, MoCA scores explained a significant amount of variance in TFLS performance (R2 = 0.044, F(1, 169) = 7.80, p = .006). Neither the GAI nor GDS explained significant additional variance. Only MoCA scores (b = .30, p =.006) predicted TFLS performance. For those with dementia, MoCA scores explained significant variance in TFLS scores (R2 = 0.338, F(1, 392) = 200.47, p < .001). The GAI explained additional significant variance when added (AR2 = 0.009, F(1, 391) = 5.26, p = .022). The GDS did not explain any additional variance. Both the MoCA (b = 1.29, p < .001) and the GAI (b = -0.15, p = .002) significantly predicted TFLS performance.Conclusions:While results suggest that anxiety and depressive symptoms alone do not explain a significant degree of variance within scores of adaptive functioning across the entire sample, elevated ratings of anxiety and depressive symptoms were significant predictors of lower scores of ADLS, suggesting some support for our hypothesis. Additionally, anxiety symptoms significantly explained increased variance in TFLS scores for those diagnosed with dementia, suggesting a potential relationship between anxiety levels and poor adaptive functioning for dementia patients.

Abstract Background In spite of viral suppression with antiretroviral therapy (ART), neurocognitive impairment (NCI) affects ~20% of those infected with HIV; most are asymptomatic or only mildly impaired based on instrumental activity of daily living (IADL) self-reported questionnaires. Previous studies have shown a strong association between depression, common among HIV+, and self-reported IADL impairment, potentially confounding evaluation of the functional impact of NCI. We studied a brief (15–20 minutes) task-based measure of function, the Texas Functional Living Scale (TFLS), in the context of HIV, NCI, and depression. Methods Baseline data were analyzed from parallel, longitudinal cohort studies of neurocognitive function among HIV+ and demographically matched HIV-subjects enrolled at NIH and DoD sites. Subjects recruited at NIH were on ART with viral suppression (VS) ≥1 year and nearly all in the DoD also had long-term VS. All participants underwent a standardized, comprehensive neurocognitive battery (7 domains), as well as the TFLS. Global deficit score (GDS) ≥0.5 defined neurocognitive impairment (NCI) and TFLS impairment was defined as T-score >1 standard deviation below mean (i.e., < 40). Results 420 subjects were evaluated with demographics in Table 1. Eighty-five subjects (20%) had NCI by GDS and 57 (13%) subjects had TFLS impairment. 17% had a Beck Depression Inventory II (BDI) score ≥13 indicating significant depressive symptoms. In univariate analysis of Table 1 variables, only HIV status was not significantly different between those with or without TFLS impairment, however after adjustment using multivariable logistic regression, only education level, race, and NCI were associated with TFLS impairment; depressive symptoms (BDI ≥13) were not associated with functional impairment measured by TFLS. Conclusion In parallel DoD and NIH cohorts of well-treated HIV+ and matched HIV- subjects, task-based functional impairment measured by TFLS was strongly associated with NCI, but not with depressive symptoms, suggesting the potential utility of this measure to better understand the functional consequences of HIV associated neurocognitive disorders. While the association of TFLS with education was expected, that with race was not and requires further study. Disclosures All authors: No reported disclosures.

The present paper reports fifteen medicinal plant species belonging to twelve families from the Timberline Forest Extensions (TFEs) in Dayyara meadow which is located in district Uttarkashi of Garhwal Himalaya at an elevation ranging between 3308 m and 4200 m. Timberline Forest Extensions (TFEs) are dense small patches of typical timberline woody species which serve as refuge habitat for commercially exploited and vulnerable medicinal plants. The deformed architecture of the woody species in these TFEs further supports the growth of herbs by sheltering them from various biotic and natural stresses.

<abstract><p>The construction of efficient numerical schemes with uniform convergence order for time-fractional diffusion equations (TFDEs) is an important research problem. We are committed to study an efficient uniform accuracy scheme for TFDEs. Firstly, we use the piecewise quadratic interpolation to construct an efficient uniform accuracy scheme for the fractional derivative of time. And the local truncation error of the efficient scheme is also given. Secondly, the full discrete numerical scheme for TFDEs is given by combing the spatial center second order scheme and the above efficient time scheme. Thirdly, the efficient scheme's stability and error estimates are strictly theoretical analysis to obtain that the unconditionally stable scheme is $ 3-\beta $ convergence order with uniform accuracy in time. Finally, some numerical examples are applied to show that the proposed scheme is an efficient unconditionally stable scheme.</p></abstract>

Abstract Objective Prior factor analysis of the Texas Functional Living Scale (TFLS), a performance-based measure of functional abilities, in a military veteran sample supported four factors discrepant from the published subscales. This study analyzed TFLS factor structure in a non-veteran clinical sample. Method Two hundred seventy adult outpatients completed the TFLS during neuropsychological evaluation. Principal axis factor analysis with oblique promax rotation was conducted with age and education effects partialed out. Results Parallel analysis indicated five factors for extraction that accounted for a combined 48% of the variance. The first factor independently explained 26% of the total variance. Inspection of factor loadings suggested the following factor interpretations: complex calculations/time, complex visual search, praxis, memory, and basic calculations/math concepts. Five items did not significantly load onto any of the factors. Conclusions Current results did not entirely correspond to the published subscales or prior results in a veteran sample. Further clarification of the TFLS factor structure is warranted.

Le cycle thermodynamique classique des turbines à gaz n'a subi aucune modification majeure au cours des dernières décennies, et les améliorations d'efficacité les plus importantes ont été obtenues en réduisant les pertes thermiques, en augmentant le taux de compression et la température maximale. Malgré les efforts visant à améliorer les performances des chambres de combustion, les technologies actuelles pourraient ne pas être à la hauteur des contraintes environnementales de plus en plus strictes. Par conséquent, une percée technologique est essentielle pour façonner l'avenir des moteurs thermiques. La combustion à gain de pression (PGC) émerge comme l'une des solutions les plus prometteuses, introduisant de nouveaux cycles thermodynamiques où la pression augmente tout au long du processus de combustion. Cela peut conduire à une augmentation d'entropie plus faible, bénéficiant à l'efficacité globale du cycle.Plusieurs concepts de PGC sont actuellement étudiés par la communauté scientifique, allant de la déflagration, telle que la combustion à volume constant (CVC), à la détonation, notamment la combustion à détonation rotative (RDC). La simulation numérique est utilisée pour évaluer les performances de ces systèmes et pour mieux comprendre leur comportement afin de les améliorer avant de procéder à des essais expérimentaux. La simulation aux grandes échelles (LES) a un rôle important dans ce domaine grâce à sa capacité à prédire fidèlement les écoulements réactifs. Cependant, avec la complexité croissante des systèmes de combustion, des modèles physiques avancés sont cruciaux pour assurer des simulations prédictives.Dans ce travail, la combustion à volume constant est évaluée et les principaux défis numériques posés par ces systèmes de combustion sont examinés. L'allumage, la combustion à haute pression, la dilution, l'interaction flamme-turbulence, les effets d'étirement, les flux de chaleur font partie intégrante de la physique que les systèmes CVC englobent, et leur interaction conduit à des phénomènes physiques complexes qui doivent être modélisés. Les modèles numériques développés dans ce travail sont principalement examinés dans des cas test, puis appliqués dans le calcul de la chambre à volume constant CV2, opérée au laboratoire Pprime (Poitiers, France).D'abord, des nouvelles conditions limites sont dérivées de la théorie des tuyères pour mimer les effets des soupapes d'admission et d'échappement. Les propriétés d'écoulement sont imposées dynamiquement à la fois à l'entrée et à la sortie de ces systèmes contrôlés par des vannes.Une chimie globale pour les mélanges propane/air est dérivée pour différentes pressions, températures et compositions de gaz frais. La cinétique chimique est optimisée pour différentes concentrations de diluants, composés des gaz brûlés tels que le dioxyde de carbone et la vapeur d'eau. Comme les moteurs à piston, les chambres CVC fonctionnent cycliquement, et chaque cycle de combustion est influencé par les gaz résiduels provenant des cycles précédents. Pour cette raison, un modèle numérique détaillant la composition locale des mélanges inflammables dilués est proposé pour fournir toutes les informations sur les gaz frais nécessaires à la cinétique et au modèle de combustion. Basé sur une généralisation du Thickened Flame (TF), un nouveau modèle de combustion, le Stretched-Thickened Flame (S-TF) model, est développé pour surmonter les limitations du modèle TF dans la prédiction des effets d'étirement sur la vitesse de combustion des flammes laminaire. Cela est crucial pour capturer efficacement les événements transitoires des flammes propagative, fondamentaux dans les chambres CVC. Enfin, dans le cadre de la modélisation de l'allumage, le modèle de dépôt d'énergie est couplé avec le modèle S-TF.Les modèles développés dans cette thèse sont ensuite appliqués à la chambre CV2, mettant en évidence leur impact positif dans la prédiction de la physique transitoire impliquée dans ces systèmes
Classical gas turbine thermodynamic cycle has undergone no major changes over the last decades and the most important efficiency improvements have been obtained reducing thermal losses and raising the overall pressure ratio and peak temperature. Despite the efforts in research and development aiming at enhancing especially combustion chambers performances, current technologies may fall short of complying the increasingly stringent environmental constraints. Consequently, a technological breakthrough is essential to shape the future of thermal engines. Pressure Gain Combustion (PGC) emerges as one of the most promising solutions, introducing new thermodynamic cycles where, unlike the Brayton cycle, pressure increases across the combustion process. This can lead to a lower entropy raise, benefiting the overall cycle efficiency.Several PGC concepts are currently studied by the combustion community, ranging from deflagration, such as constant volume combustion (CVC), to detonation, including Rotating Detonation Combustion (RDC) and Pulse Detonation Engine (PDE). Numerical simulation is used to assess the performance of these systems as well as better understand their behavior for improvements before performing experimental tests. Large Eddy Simulation (LES) has assumed an increasingly significant role in combustion science thanks to its high capability in capturing reacting flows. However, with the increasing complexity of combustion systems, advanced physical models are crucial to ensure predictive simulations.In this work, constant volume combustion technology is assessed and the main numerical challenges posed by these combustion systems are scrutinized. Ignition, high pressure combustion, dilution, flame-turbulence interaction, flame-stretch effects, heat fluxes are just part of the physics that CVC systems encompass and their interplay leads to complex physical phenomena that have to be modeled. The numerical models developed in this work are primarily scrutinized in simple test cases and then applied in complete 3D LES framework to compute the constant volume combustion chamber CV2, operated at Pprime laboratory (Poitiers, France).First, novel boundary conditions, based on NSCBC formalism, are derived from nozzle theory to mimic intake and exhaust valve effects. With this strategy no moving part is introduced in the LES and the flow properties are imposed both at the inlet and the outlet of these valves-controlled systems.Second, a two-step chemistry for propane/air mixtures is derived for multiple pressure, temperature and composition of fresh gases. The chemical kinetics is optimized for different concentration of dilutants, composed by burnt products such as carbon dioxide and water vapor. Like piston engines, constant volume chambers operate cyclically and each combustion event is affected by the residual burnt gases coming from previous cycles. For this reason, a numerical model to detail the local composition of diluted flammable mixtures is proposed to provide all the fresh gas information required by the kinetics and the combustion model. Based on a generalization of the classical Thickened Flame (TF) model, a new combustion model, the Stretched-Thickened Flame (S-TF) model, is developed to overcome the TF model limitations in predicting stretch effects on the laminar flame burning velocity. This is crucial to well capture transient events of propagating flames, which are fundamental in CVCs.Eventually, the ignition modeling is assessed and the Energy Deposition model is coupled with the S-TF model by tracking the kernel size in time.The models developed in this thesis are then applied to the CV2 chamber, highlighting their positive impact in capturing the unsteady physics involved in such systems

Polymers and their composites have been widely applied in different industrial sectors as alternatives to conventional metal-based materials, for the better performance of the system, increasing efficiency and cutting down operational costs. In those applications polymeric materials are sometime subjected to tribological loading conditions where external lubricants are not permissible and polymers’ self-lubricating ability is desirable in such tribo-contacts. In particular, high temperature is often the key factor determining the working conditions of polymers. Hence, high performance polymers (HPPs) have received increasing attention in last decades. In view of above-mentioned facts, the present research investigated the tribological performance of some important engineering polymers and their nanocomposites such as epoxy, PEEK, PPP and PBI. For example, nano-silica (SiO2), nano-rubber (CBTN) and titanium dioxide (TiO2) nano-particles have been incorporated in thermosetting epoxy resin and PEEK, respectively, to improve their tribological properties. To explore the effect of harsh environments during sliding wear, pin-on-disk tests of above-mentioned materials were carried out in dry, wet and elevated temperature regimes. Finally, attempts have been made to establish correlations between the basic mechanical properties of HPPs and their sliding wear behaviour. Various wear models to correlate the tribological aspects of HPPs and polymer nanocomposites with associated mechanical properties were examined along with experimental validation. In addition to that, underlying wear mechanisms were taken into account towards model developments. To develop a quantitative solution for wear prediction, the new computer techniques such as artificial neural network (ANN) may be helpful in the area. Accordingly, the ANN was employed to find the general wear trend of materials.

碩士
國立中央大學
電機工程研究所
90
In order to investigate the feasibility of fabricating Si-based visible light-emitting diodes (LEDs) with common well-developed silicon processing technology, the SiO2-isolated n [phosphorous-doped hydrogenated amorphous silicon (n-a-Si:H) ] - i [intrinsic hydrogenated amorphous silicon-carbon (i-a-SiC:H) or intrinsic hydrogenated amorphous silicon-nitride (i-a-SiN:H)] - p [boron-doped hydrogenated amorphous silicon (p-a-Si:H)] thin-film LEDs (TFLEDs) were fabricated on n-type c-Si wafers. These SiO2-isolated TFLEDs would emit red-orange, green-white light and even light with voltage-tunable color. The red-orange TFLED revealed a highest brightness of 8100 cd/m2 at an injection current density of 600 mA/cm2, an electroluminescence (EL) peak wavelength at 600 nm, and an EL threshold voltage = 19.1 V. The green-white TFLED had a brightness of 370 cd/m2 at an injection current density of 300 mA/cm2, an EL peak wavelength at 528 nm, and an EL threshold voltage = 15.4 V. The voltage-tunable TFLEDs had the EL peak wavelength ranged from 565 nm to 670 nm at different applied voltages. The experimental results demonstrated the feasibility of developing Si-based visible light-emitting devices on c-Si substrate.

碩士
國立中央大學
電機工程學系
86
In order to blue-shift the electroluminescence (EL) peak wavelength of anamorphous p-i-n thin-film light-emitting diode (TFLED), a higher optical-gapmaterial, a-SiN:H, was used as the luminescent i-layer. Further, to improve the device EL properties, the same material (a-SiN:H) was employed to from thep-i and n-i brightness of a finished device, having a n+-a- Si:H layer contactedwith the Al external electrode , was 200cd/ m2 at an injection current density of 4A/cm2. Its EL threshold voltage was 11.7V and peak wavelength of EL spectrum.However, its brightness is lower and not so good as expected. The current-conductionmechanism of the a-SiN:H p-i-n TFLEDs was also investigated. For a low applied voltage, the ohmic conduction is dominat. Whereas, for a high applied voltage, the Frenkel-Poole emission is the main conduction mechanism.

Nowadays, models predicting soot emissions are, neither able to describe correctly fine effects of technological changes on sooting trends nor sufficiently validated at relevant operating conditions to match design office quantification needs. Yet, phenomenological descriptions of soot formation, containing key ingredients for soot modeling exist in the literature, such as the well-known Leung et al. model (Combust Flame 1991). This approach indeed includes contributions of nucleation, surface growth, coagulation, oxidation and thermophoretic transport of soot. When blindly applied to aeronautical combustors for different operating conditions, this model fails to hierarchize operating points compared to experimental measurements. The objective of this work is to propose an extension of the Leung model, including an identification of its constants over a wide range of condition relevant of gas turbines operation. Today, the identification process can hardly be based on laboratory flames since few detailed experimental data are available for heavy-fuels at high pressure. Thus, it is decided to directly target smoke number values measured at the engine exhaust for a variety of combustors and operating conditions from idling to take-off. A Large Eddy Simulation approach is retained for its intrinsic ability to reproduce finely unsteady behavior, mixing and intermittency. In this framework, The Leung model for soot is coupled to the TFLES model for combustion. It is shown that pressure-sensitive laws for the modelling constant of the soot surface chemistry are sufficient to reproduce engine emissions. Grid convergence is carried out to verify the robustness of the proposed approach. Several cases are then computed blindly to assess the prediction capabilities of the extended model. This study paves the way for the systematic use of a high fidelity tool solution in design office constraints for combustion chamber development.

One method for characterizing the contact conductance of Thermal Interface Materials (TIMs) is the steady state one dimensional heat flow method typified by ASTM D5470. A test apparatus and procedure were developed which use the basic theory of steady state testing TIMs and improves upon the accuracy and repeatability of the standard test. This procedure and apparatus were used to test the contact conductance of the interface four commercial available TIMs. These materials include: Laird Tflex 720, Laird Tmate 2905c, Chomerics Cho-Therm T500, and Chomerics Cho-Therm 1671. It was found that the Laird products underperformed the available manufacturer published values and the Chomerics products only met performance expectations at relatively high clamping pressures (400 psi).

With the advantages of high reliability, high power density and long life, small nuclear power reactor has become one of the most excellent space power options in the space missions. TOPAZ-II is the most mature space nuclear power reactor based on thermionic conversion. In this paper, the thermo-physical and transport properties of NaK-78 and heat transfer correlations for liquid metals are implemented into the RELAP5 code. The modified RELAP5 has already been accessed to analyze the thermal-hydraulic characteristics of the space reactor cooled by NaK-78. A RELAP5 model including the core, TFEs, radiator, coolant loop and volume accumulator is developed. Temperature reactivity feedback, TFE emitter, TFE collector, moderator and the reactivity insertion effects of control drums and safety drums are modeled in the point reactor kinetics equations with six-group delayed neutrons. To V&V the integrated TOPAZ-II system model, the steady state is simulated and analyzed. The steady state calculated results are in good agreement with the designed values. On the basis of V&V, a hypothetical reactivity insertion accident is simulated and analyzed. During the accident, the automatic control system is assumed to be malfunctioned, 0.01$ positive reactivity is introduced for 500s and then control drums start to rotate inward. The maximum temperatures of fuel and emitter are below the melting temperature, respectively. The maximum temperature of coolant is 940K with 160K margin from boiling. With the rotating of control drums, the reactor reaches critical again.