Surface optimization of metal halide perovskite solar cells using ZnS nanorods

Journal of Materials Science: Materials in Electronics - The present paper reports the fabrication of solar cells using surface-optimized ZnS-Perovskite composites. Initially, ZnS nanorods (NRs)...     

Adaptive Control of Aircraft Wing Flutter by Stress-Induced Stiffness Modification

Lightweight unoccupied air vehicles (UAVs) with wide wingspans are especially vulnerable to dynamic instability. Such instability can be contained by using mass and stiffness balancing and the shape and attitude of the aircraft in flight. Passive methods and pilot-operated devices such as dampers, ailerons, flaps, and other actuators, are currently used. Also, ongoing attempts exist to develop self-adaptive controls by using piezoelectric and other devices. The present work is concerned with controlling aerodynamic flutter by using stress-induced elements in selected structural components of the aircraft wing. A scheme has been developed to determine the “optimal” locations for such elements to be activated, in real time, to contain the dynamic instability or flutter condition. Various stress-induced stiffening schemes have been developed to modify the frequency response of aircraft wings by shifting the critical flutter speed to safe levels. Results and conclusions include the identification of the optimal location and type of the stress-induced elements and the magnitude and distribution of induced stress for best results with the least expense of energy during actuation.     

Determination of filler content in rice husk ash and wood-based composites by thermogravimetric analysis

Three new types of fillers for polypropylene are investigated. The first two were derived from burnt rice husk ash (RHA), whereas the third, a wood-based filler, was processed from oil palm trunk. One important characterization of the composites involves the checking for the actual filler content and filler distribution within the matrix. An analytical technique is described here for computation of the filler content in the composites based on a simple expression derives from thermogravimetric analyses. For filler with volatiles such as the black RHA, the derived expression was p _f = 106 ( r _b / m _c ), and for easily burnt fillers (wood-based), the expression was p _f = 156 ( m _d / m _c ). The technique has shown good agreement and consistency between analyzed and actual filler contents and a uniform filler distribution within the polypropylene matrix. © 1994 John Wiley & Sons, Inc.     

Aspects of miscibility in poly(vinyl chloride)/epoxidized natural rubber blends. Part I: Mechanical and morphological properties

Miscibility in poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends was studied by examining evidence from tensile, impact, and physical properties. The observation of synergism in tensile strength, percent elongation at break, hardness, and relative density has reaffirmed PVC/ENR blends as miscible systems. Studies of impact properties, however, revealed that the blends are microheterogeneous in nature. This could be attributed to the large sizes of polymer molecules involved and the microgel content of ENR-50. Results from Fourier transform infrared spectroscopy (FTIR) revealed that hydrogen bonding is extensively involved in PVC/ENR systems. This evidence unveiled the exact nature of the specific interactions responsible for miscibility and hence the enhanced mechanical properties of PVC/ENR blends.     

Probabilistic Fire Simulation Assessment Using Simplified Model and Zone Modelling of a Kitchen Fire Scenario

Fire Technology - Probabilistic fire simulation has been gaining interest in performance-based design approach. Very few evaluations on modelling performance can lead to...     

A static friction model for tube bulge forming using a solid bulging medium

In a metal working process, the friction between the material and the tools influences the process by modifying the strain distribution of the workpiece. From a numerical point of view, a constant coefficient of friction (Coulomb’s friction) is commonly used in finite element simulations to model the frictional behaviour of contacting solids. However, friction coefficient varies in time and space with many parameters. We presented here a theoretical model of static friction in rubber/metal contact which allows the determination of the static coefficient of friction as a function of local contact conditions. Simulations using finite element software ABAQUS/Explicit were carried out for an axisymmetric tube bulging operation using the defined friction model. We compared the computed tube thickness related to the constant coefficient of static friction with the defined friction model. The results clearly showed that the new friction model provides better agreement between experiments (Girard, Grenier, Mac Donald, J Mater Process Technol 172:346–355, 2006) and results of numerical simulations.     

Tribological Testing of Hemispherical Titanium Pin Lubricated by Novel Palm Oil: Evaluating Anti-Wear and Anti-Friction Properties

In this study, the properties of hip implant material and lubricants were examined using a pin on disc apparatus, to compare the effect of metal-on-metal(Mo M)contact with a bio-lubricant derived from palm oil. The behaviour of the lubricants was observed during the experiments, in which a hemispherical pin was loaded against a rotating disc with a groove. A titanium alloy was used to modify the hemispherical pin and disc. Before and after the experiments, the weight and surface roughness were analysed, to detect any degradation. The results were compared according to the different kinematic viscosities.The wear rates and level of friction with each lubricant were also examined. The lubricant with the highest viscosity had the lowest frictional value. Therefore, developing suitable lubricants has the potential to prolong the lifespan of prostheses or implants used in biomedical applications. The experiments collectively show that lubricants derived from palm oil could be used as efficient bio-lubricants in the future.     

Effect of cryogenic high-speed milling of compacted graphite iron using indirect spray system

Compacted graphite iron (CGI) is replacing conventional cast iron (CI), especially in the automotive industries for the manufacture of a high-performance and light-weight diesel engine due to its outstanding mechanical properties as compared to the conventional CI. Nevertheless, the pace of replacement is still slow because of the low machining performance encountered by the industries during high-speed machining of CGI. Thus, in this study, the effect of various cooling-lubrication strategies in high-speed machining of CGI using uncoated carbide inserts was investigated. Results showed that the combination of indirect cryogenic cooling and minimum quantity lubrication (MQL) improves the tool life by 26% compared to conventional flood coolant strategy. The result has been clarified by monitoring the cutting force and the sound pressure for each cooling/lubrication strategy.     

Exudates segmentation using inverse surface adaptive thresholding

This paper presents a new approach to detect exudates and optic disc from color fundus images based on inverse surface thresholding. The strategy involves the applications of fuzzy c-means clustering, edge detection, otsu thresholding and inverse surface thresholding. The main advantage of the proposed approach is that it does not depend on manually selected parameters that are normally chosen to suit the tested databases. When applied to two sets of databases the proposed method outperforms methods based on watershed segmentation and morphological reconstruction. The proposed method obtained 98.2 and 90.4 in terms of sensitivity for Standard Diabetic Retinopathy Database – Calibration Level 1 (DIARETDB1) and a local dataset provided by National University Hospital of Malaysia (NUHM), respectively.