Effects of passive vibration absorbers on the mechanisms having clearance joints

Multibody System Dynamics - In the current study, the dynamic behavior of two planar mechanisms with revolute joints, in the presence of clearances is investigated. Subsequently, a control scheme...     

A new F(ast)-CMS NEGF algorithm for efficient 3D simulations of switching characteristics enhancement in constricted tunnel barrier silicon nanowire MuGFETs

In this paper, we present 3D quantum simulations based on Non-Equilibrium Green’s Function (NEGF) formalism using the Comsol Multiphysics^? software and on the implementation of a new Fast Coupled Mode-Space (FCMS) approach. The FCMS algorithm allows one to simulate transport in nanostructures presenting discontinuities, as the normal Coupled Mode-Space (CMS) algorithm does, but with the speed of a Fast Uncoupled-Mode Space (FUMS) algorithm (a faster algorithm that cannot handle discontinuities). We then use this new algorithm to explore the effect of local constrictions on the performance of nanowire MultiGate Field-Effect Transistors (MuGFETs). We show that cross-section variations in a nanowire result in the formation of energy barriers that can be used to improve the on/off current ratio and switching characteristics of transistors: (1) A small constriction resulting in a barrier of the order of a 0.1 eV can be used as an effective means to improve the subthreshold slope and minimize the on/off current ratio degradation resulting from SD tunneling in ultra scaled transistor, and (2) We also report a new variable barrier transistor (VBT) device concept that is able to achieve sub-kT/q subthreshold slope without using impact ionization or band-to-band tunneling. Intra-band tunneling through constriction barriers is used instead. The device is, therefore, fully symmetrical and can operate at very low supply voltages. A subthreshold slope as low as 56.5 mV/decade is reported at T=300 K. The VBT reported here breaks the 60 mV/dec barrier over more than five decades of subthreshold current, which is the widest current range reported so far.     

Specific contributions of phonological abilities to early reading acquisition: Results from a Dutch latent variable longitudinal study.

Contributions of phonological abilities to early reading acquisition were examined in a longitudinal study of 166 Dutch children from kindergarten through 2nd grade. Various phonological abilities, nonverbal intelligence, vocabulary, and letter knowledge were assessed in kindergarten and Grade 1. Reading and arithmetic were examined in 1st and 2nd grades. The importance of individual differences in phonological ability for subsequent reading acquisition changed over time. At first, the effects of phonological abilities increased, but after Grade 1, these effects disappeared. Phonological awareness and rapid naming had independent and specific influences on reading achievement. Verbal working memory was associated with both reading and arithmetic acquisition. The results tend to support an interactive view of the relation between development of phonological abilities and learning to read. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in the manifestation of a phonological deficit in dyslexic children learning to read a regular orthography.

In a longitudinal study, the development of phonological processing abilities was studied in 19 dyslexic, 17 weak, and 19 normal readers learning to read in Dutch. Among other abilities, phonological awareness and rapid automatized naming were assessed in kindergarten, in 1st grade, and in 6th grade. Dyslexic and weak readers had impairments in rapid naming from kindergarten through 6th grade. Their impairments in phonological awareness at the level of phonemes became manifest in 1st grade and tended to disappear at the end of primary school. However, in a second cross-sectional study, including 13 dyslexic and 25 normal readers, dyslexic children's awareness of phonemes was hampered when task demands increased. The various manifestations of a phonological deficit follow distinct developmental pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coalescence efficiency of bubbles in bubble columns

Bubble size distribution was modelled by employing the population balance equation (PBE). All three bubble coalescence mechanisms (turbulence, buoyancy and laminar shear) and the main bubble breakup mechanism (breakup due to turbulent eddies) were considered in the model. Local bubble size distributions at the top and bottom of the column were obtained by solving this PBE. The results were compared with the experimental data for seven independent multiphase systems (water/air, isomax diesel/air, kerosene/air and four other liquid mixture/air) at two diverse gas velocities. The experimental adjustable constant in the coalescence efficiency function was determined by fitting the population balance to the experimental bubble size distributions. An empirical correlation was proposed for the coalescence efficiency by the dimensional analysis, which includes Reynolds and Weber numbers. © 2011 Canadian Society for Chemical Engineering     

Elucidating the Impact of Mg Substitution on the Properties of NASICON-Na3+yV2−yMgy(PO4)3 Cathodes

Vanadium multiredox-based NASICON-Na_zV_2−yM_y(PO₄)₃ (3 ≤ z ≤ 4; M = Al³⁺, Cr³⁺, and Mn²⁺) cathodes are particularly attractive for Na-ion battery applications due to their high Na insertion voltage (>3.5 V vs Na⁺/Na⁰), reversible storage capacity (≈150 mA h g⁻¹), and rate performance. However, their practical application is hindered by rapid capacity fade due to bulk structural rearrangements at high potentials involving complex redox and local structural changes. To decouple these factors, a series of Mg²⁺-substituted Na_3+yV_2−yMg_y(PO₄)₃ (0 ≤ y ≤ 1) cathodes is studied for which the only redox-active species is vanadium. While X-ray diffraction (XRD) confirms the formation of solid solutions between the y = 0 and 1 end members, X-ray absorption spectroscopy and solid-state nuclear magnetic resonance reveal a complex evolution of the local structure upon progressive Mg²⁺ substitution for V³⁺. Concurrently, the intercalation voltage rises from 3.35 to 3.45 V, due to increasingly more ionic V O bonds, and the sodium (de)intercalation mechanism transitions from a two-phase for y ≤ 0.5 to a solid solution process for y ≥ 0.5, as confirmed by in operando XRD, while Na-ion diffusion kinetics follow a nonlinear trend across the compositional series.     

NBTI and hot-carrier effects in accumulation-mode Pi-gate pMOSFETs

Negative bias temperature instability (NBTI) and hot-carrier induced device degradation in accumulation-mode Pi-gate pMOSFETs have been studied for different fin widths ranging from 20 to 40 nm. The NBTI induced device degradation is more significant in narrow devices. This result can be explained by enhanced diffusion of hydrogen at the corners in multiple-gate devices. Due to larger impact ionization, hot-carrier induced device degradation is more significant in wider devices. Finally, hot-carrier induced device degradation rate is highest under stress conditions where V_GS = V_TH.     

Comparison of different surface orientation in narrow fin MuGFETs

Device performance characteristics are investigated for different surface orientation and doping concentration on accumulation-mode p-type and inversion-mode n-type MuGFETs. Short-channel effects and drain breakdown voltage are better is carrier transport is in the (1 0 0) direction than in the (1 1 0) direction. This is due to the larger Si/SiO₂ interface roughness, the higher density of interface state at (1 1 0) surfaces, and to the difference of effective mass. The mobility in PMOS devices, however, is much higher in the (1 1 0) direction than that in the (1 0 0) direction. For better performance of device, our results show that optimized fin orientation can improve device stability and performance.     

An early comparison between endoscopic ultrasound-guided fine-needle aspiration and mediastinoscopy for diagnosis of mediastinal malignancy

Precise mediastinal lymph node staging is essential in non-small cell lung cancer for proper evaluation and treatment. In addition to CT, mediastinoscopy is routinely used for staging and diagnosis of mediastinal malignancy. Recently, endoscopic ultrasound (EUS) combined with fine-needle aspiration (FNA) biopsy has been used to evaluate mediastinal disease. The purpose of this study was to assess and compare mediastinoscopy with EUS/FNA in the evaluation of mediastinal masses. From August 1995 to July 1997, 21 patients with suspected mediastinal malignancy underwent cervical mediastinoscopy with biopsy. During this same period, seven patients with suspected mediastinal malignancy were evaluated using EUS/FNA. All patients were retrospectively studied. Both mediastinoscopy and EUS/FNA were highly sensitive in diagnosing mediastinal malignancy (100% and 86%, respectively). Specificity and positive predictive value were 100 per cent for both procedures. Mediastinoscopy and EUS/FNA are highly accurate methods of staging mediastinal malignancy. Mediastinoscopy provides better access to the upper and anterior mediastinum, whereas EUS/FNA can safely be used to biopsy subcarinal and posterior mediastinal masses. Mediastinoscopy and EUS/FNA target different areas of the mediastinum and may be complimentary in the evaluation of mediastinal malignancy and staging of bronchogenic carcinoma.