碳纤维复合材料无人机叶片的仿真与分析

为得到碳纤维在无人机叶片中最优的铺层方式,通过Workbench中的ACP(ANSYS Composite PrepPost)模块,对碳纤维复合材料无人机叶片的铺层进行设计。利用SolidWorks三维建模软件建立无人机叶片的三维模型,并采用HyperMesh对叶片进行几何清理、划分网格等,利用Ansys Workbench Fluent对无人机叶片的不同转速进行流体仿真,提取叶片表面压力载荷,对不同铺层的碳纤维复合材料无人机叶片进行仿真与分析,得到碳纤维复合材料无人机叶片的力学仿真结果,并基于Tsai-Wu失效准则,计算每层铺层的失效系数,进而对比得出最优的碳纤维铺层方式为[0°,90°,90°,90°,0°]。     

A new grounded lamination gate (GLG) for diminished fringe-capacitance effects in high-/spl kappa/ gate-dielectric MOSFETs

A grounded lamination gate (GLG) structure for high-/spl kappa/ gate-dielectric MOSFETs is proposed, with grounded metal plates in the spacer oxide region. Two-dimensional device simulations performed on the new structure demonstrate a significant improvement with respect to the threshold voltage roll-off with increasing gate-dielectric constant (due to parasitic internal fringe capacitance), keeping the equivalent oxide thickness same. A simple fabrication procedure for the GLG MOSFET is also presented.     

Grain orientation and anisotropy in the physical properties of SrBi2(Nb1 − x V x )2O9 (0 ≤ x ≤ 0.3) ceramics

SrBi₂(Nb_{1 – x} V _x )₂O₉ (0 x 0.3 in molar ratio) ceramics have been fabricated via conventional sintering at elevated temperatures. Interestingly sintering the pellets in the 1320–1470 K temperature range yielded partially grain oriented ceramics. The orientation factor (f) monitored via X-ray powder diffraction studies was found to increase with increasing V₂O₅ content and reached 83% for x = 0.3. The increment in (f) was not that significant with increase in sintering temperature and its duration. The microstructural studies suggest that V₂O₅ has a truncating effect on the abnormal platy growth of SBN grains. The dielectric constant (_r) and loss (D) measurements as functions of both temperature and V₂O₅ content have been carried out along the directions parallel (_rp) and perpendicular (_rn) to the cold pressing axis of the pellet. The anisotropy (_rn/_rp) associated with _r was found to be 1.11 at 300 K and 2.1 at the Curie temperature, (T _c) respectively. Different dielectric mixture formulae that were employed to analyze the effective dielectric constants of these samples with varying porosity confirmed that the experimental value of _r was comparable with that obtained using Wiener's formula. Impedance spectroscopy was employed to rationalize the electrical behavior of these ceramics. The pyroelectric coefficients along the directions parallel and perpendicular to the pressing axis of the grain oriented (83%) SBN ceramic at 300 K were 0.13145 mC/m²K and 0.26291 mC/m²K respectively. The ferroelectric properties of these grain-oriented ceramics were better in the direction perpendicular to the pressing axis than those in the parallel direction.     

Emission factors of carbon monoxide and size-resolved aerosols from biofuel combustion

This study reports emission factors of carbon monoxide and size-resolved aerosols from combustion of wood, dung cake, and biofuel briquette in traditional and improved stoves in India. Wood was the cleanest burning fuel, with higher emissions of CO from dung cake and particulate matter from both dung cake and briquette fuels. Combustion of dung cake, especially in an improved metal stove, resulted in extremely high pollutant emissions. Instead, biogas from anaerobic dung digestion should be promoted as a cooking fuel for public health protection. Pollutant emissions increased with increasing stove thermal efficiency, implying that thermal efficiency enhancement in the improved stoves was mainly from design features leading to increased heat transfer but not combustion efficiency. Compared to the traditional stove, the improved stoves resulted in the lower pollutant emissions on a kW h-1 basis from wood combustion but in similar emissions from briquette and dung cake. Stove designs are needed with good emissions performance across multiple fuels. Unimodal aerosol size distributions were measured from biofuel combustion with mass median aerodynamic diameters of 0.5-0.8 micron, about a factor of 10 larger than those from fossil fuel combustion (e.g. diesel), with potential implications for lung deposition and health risk.     

Changes in the glaciers of Chandra–Bhaga basin,Himachal Himalaya,India, between 1980 and 2010 measured using remote sensing

This study reports the glacier changes of Chandra–Bhaga basin, northwest Himalaya, India, from 1980 to 2010. Satellite remote-sensing data from the Landsat Multispectral Scanner (MSS) and Thematic Mapper (TM), the Linear Imaging Self Scanning Sensor (LISS) and Advanced Wide Field Sensor (AWiFS) of the Indian Remote Sensing (IRS) series, and the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) were used to study the changes in glacier parameters such as glacier area, length, snout elevation, and the impact of glacier topographical parameters (glacier slope, aspect, and altitude range) on the glacier changes. It was found that the total glaciated area had shrunk to 368.2 km² in 2010 from 377.6 km² in 1980, a loss of 2.5%. The average position of glacier terminuses retreated by 465.5 ± 169.1 m from 1980 to 2010 with an average rate of 15.5 ± 5.6 m year^?1. The decadal scale analysis showed that the average rate of retreat had increased the most in the recent decade. A moraine-dammed lake located in the study region was found to have expanded in area from (0.65 ± 0.01) km² in 1980 to (1.26 ± 0.03) km² in 2010. Glaciers with steep slope and less altitude range have lost more area than the glaciers having gentle slope and greater altitude range.     

Size Distribution and Morphology of Liposome Aerosols Generated By Two Methodologies

Pulmonary delivery of sustained release formulations needs drug encapsulation in a suitable matrix, as well as the generation of aerosols with high lung penetration and suitable release characteristics. Nanometer sized liposomes offer the potential for biocompatibility, controlled release and easy internalization in the lung. For uniform dose delivery and drug release kinetics, it is of interest to understand generation techniques to obtain aerosols containing nearly monodispered nanometer sized dry particles. Two aerosolization techniques, air-jet atomization and electrohydrodynamic atomization (EHDA) were studied to identify conditions under which the inclusion of one-liposome-per-drop could be achieved. In air-jet atomization, low lipid concentrations resulted in a unimodal aerosol with a median mobility diameter of 94 (± 3.5) nm, while higher concentrations led to larger median diameters, implying possible inclusion of multiple liposomes per drop. In EHDA, tuning drop sizes in the range of 130 to 200 nm, as well as the use of high lipid concentrations, resulted in a bimodal aerosol distribution, with peaks at 35 and 100 nm mobility diameters. TEM images of the liposome aerosol from EDHA showed fused liposomes, resulting in cylindrical structures with different physical diameters. It was hypothesized that deformation of liposomes to cylindrical structures in the micro-capillary liquid tip of the electrospray, and interactions along the axial or cross sectional surfaces led to dry particles with different mobility sizes.     

Solvothermal synthesis and characterization of acicular α-Fe2O3 nanoparticles

Nanometer-sized α-Fe₂O₃ particles have been prepared by a simple solvothermal method using ferric acetylacetonate as a precursor. The products were characterized by X-ray diffraction (XRD), energy dispersive X-ray microanalysis (EDAX), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transition electron microscopy (TEM), infrared spectroscopy (IR) and thermal analysis (TG-DTA). XRD indicates that the product is single-phase α-Fe₂O₃ with rhombohedral structure. Bundles of acicular shaped nanoparticles are seen in TEM images with an aspect ratio ～ 12; typically 8–12 nm wide and over 150 nm long. The α-Fe₂O₃ nanoparticles posses a high thermal stability, as observed on thermal analysis traces.     

Oxidative Stress in Aging-Matters of the Heart and Mind

Oxidative damage is considered to be the primary cause of several aging associated disease pathologies. Cumulative oxidative damage tends to be pervasive among cellular macromolecules, impacting proteins, lipids, RNA and DNA of cells. At a systemic level, events subsequent to oxidative damage induce an inflammatory response to sites of oxidative damage, often contributing to additional oxidative stress. At a cellular level, oxidative damage to mitochondria results in acidification of the cytoplasm and release of cytochrome c, causing apoptosis. This review summarizes findings in the literature on oxidative stress and consequent damage on cells and tissues of the cardiovascular system and the central nervous system, with a focus on aging-related diseases that have well-documented evidence of oxidative damage in initiation and/or progression of the disease. The current understanding of the cellular mechanisms with a focus on macromolecular damage, impacted cellular pathways and gross morphological changes associated with oxidative damage is also reviewed. Additionally, the impact of calorific restriction with its profound impact on cardiovascular and neuronal aging is addressed.