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排序方式: 共有86条查询结果,搜索用时 15 毫秒
1.
Jagath C Rajapakse Choong Leong Tan Xuebin Zheng Susanta Mukhopadhyay Kanyan Yang 《IEEE engineering in medicine and biology magazine》2006,25(2):102-111
Covariance-based methods of exploration of functional connectivity of the brain from functional magnetic resonance imaging (fMRI) experiments, such as principal component analysis (PCA) and structural equation modeling (SEM), require a priori knowledge such as an anatomical model to infer functional connectivity. In this research, a hybrid method, combining independent component analysis (ICA) and SEM, which is capable of deriving functional connectivity in an exploratory manner without the need of a prior model is introduced. The spatial ICA (SICA) derives independent neural systems or sources involved in task-related brain activation, while an automated method based on the SEM finds the structure of the connectivity among the elements in independent neural systems. Unlike second-order approaches used in earlier studies, the task-related neural systems derived from the ICA provide brain connectivity in the complete statistical sense. The use and efficacy of this approach is illustrated on two fMRI datasets obtained from a visual task and a language reading task. 相似文献
2.
P. Samarasekara M. A. K. Mallika Arachchi A. S. Abeydeera C. A. N. Fernando A. S. Disanayake R. M. G. Rajapakse 《Bulletin of Materials Science》2005,28(5):483-486
Copper oxide (CuO) thin films with photocurrent as high as 25 μA/cm2 were deposited on conductive glass substrates using d.c. reactive sputtering. This was the highest reported photocurrent
for sputteredp- type copper oxide measured in the electrolyte KI. The photocurrent drastically increased up to 25 (μA/cm2 as the sputtering pressure and the substrate temperature were increased up to 8.5 mbar and 192°C, respectively. All the synthesized
films contained single phase of CuO in this range of pressure and substrate temperature. Variation of the photocurrent, photovoltage,
structure and absorbance with deposition conditions were studied in detail. 相似文献
3.
This paper presents a protection scheme that is capable of very fast isolation of faults in high voltage transmission systems. Proposed scheme comprises set of relays connected through a telecommunication network, located at different nodes of the system. Relays use wavelet coefficients of current signals to identify the fault directions relative to their location. Fault directions identified at different locations in the system can be combined to determine the faulted line (or busbar) and isolate it. A robust single ended traveling wave based fault distance estimation approach is proposed as a backup in case of communication failure. Investigations were carried out using time domain simulations in PSCAD/EMTDC for a high voltage transmission system. 相似文献
4.
Sarusha Santhiravel Alaa El-Din A. Bekhit Eresha Mendis Joe L. Jacobs Frank R. Dunshea Niranjan Rajapakse Eric N. Ponnampalam 《International journal of molecular sciences》2022,23(15)
The gastrointestinal tract of humans is a complex microbial ecosystem known as gut microbiota. The microbiota is involved in several critical physiological processes such as digestion, absorption, and related physiological functions and plays a crucial role in determining the host’s health. The habitual consumption of specific dietary components can impact beyond their nutritional benefits, altering gut microbiota diversity and function and could manipulate health. Phytochemicals are non-nutrient biologically active plant components that can modify the composition of gut microflora through selective stimulation of proliferation or inhibition of certain microbial communities in the intestine. Plants secrete these components, and they accumulate in the cell wall and cell sap compartments (body) for their development and survival. These compounds have low bioavailability and long time-retention in the intestine due to their poor absorption, resulting in beneficial impacts on gut microbiota population. Feeding diets containing phytochemicals to humans and animals may offer a path to improve the gut microbiome resulting in improved performance and/or health and wellbeing. This review discusses the effects of phytochemicals on the modulation of the gut microbiota environment and the resultant benefits to humans; however, the effect of phytochemicals on the gut microbiota of animals is also covered, in brief. 相似文献
5.
1-3 Piezocomposites are made by embedding piezoelectric fibers/rods in polymer matrix materials. Fiber–matrix interface fracture can affect the performance of piezocomposites. In this paper, axisymmetric interfacial cracks in piezocomposites are studied by considering an idealized model of a single piezoelectric fiber in a matrix material. The displacement discontinuity method is used to formulate the Mode I and II crack problems. The fundamental solutions required for DDM are derived explicitly by using the electroelastic field equations and Fourier integral transforms. The dependence of Mode I and II stress intensity factors of single and multiple interface cracks on fiber and matrix material properties, crack length and distance between cracks are investigated. 相似文献
7.
Q.Y. Soundararajah B.S.B. Karunaratne R.M.G. Rajapakse 《Materials Chemistry and Physics》2009,113(2-3):850-855
The interest in clay polymer nanocomposites (CPN) materials, initially developed by researchers at Toyota, has grown dramatically over the last decade. They have attracted great interest, both in industry and in academia, because they often exhibit remarkable improvement in materials’ properties when compared with virgin polymer or conventional micro- and macro-composites. These improvements can include high moduli, increased strength and heat resistance, decreased gas permeability and flammability, optical transparency and increased biodegradability of biodegradable polymers. Such enhancement in the properties of nanocomposites occurs mostly due to their unique phase morphology and improved interfacial properties. Because of these enhanced properties they find applications in the fields of electronics, automobile industry, packaging, and construction. This study aims at investigating the mechanical property enhancement of polyaniline (PANI) intercalated with montmorillonite (MMT) clay. The MMT–PANI nanocomposites displayed improved mechanical properties compared to the neat polymer or clay. The enhancement was achieved at low clay content probably due to its exfoliated structure. The increased interfacial areas and improved bond characteristics may attribute to the mechanical property enhancement. 相似文献
8.
We present a method to separate clustered nuclei from fluorescence microscopy cellular images, using shape markers and marking function in a watershed-like algorithm. Shape markers are extracted using an adaptive H-minima transform. A marking function based on the outer distance transform is introduced to accurately separate clustered nuclei. With synthetic images, we quantitatively demonstrate the performance of our method and provide comparisons with existing approaches. On mouse neuronal and Drosophila cellular images, we achieved 6%-7% improvement of segmentation accuracies over earlier methods. 相似文献
9.
Analysis and Design of a Micromachined Electric-Field Sensor 总被引:1,自引:0,他引:1
Bahreyni B. Wijeweera G. Shafai C. Rajapakse A. 《Journal of microelectromechanical systems》2008,17(1):31-36
In this paper, the design and experimental results for a novel micromachined electric-field sensor are presented. The operation of the sensor is based on chopping an incident field with a shutter and measuring the induced charge on two sets of electrodes situated below the shutter. Employing of thermal actuators to move the shutter allows for substantial reduction in drive-signal amplitude as compared to electrostatic actuators which has consequently resulted in less interference from the drive signal. Moreover, the drive and sense signals are separated in the frequency domain owing to the inherent nonlinearity of thermal actuators, further improving the accuracy and resolution of the measurements. The relatively small displacements produced by thermal actuators are mechanically amplified using a novel lever mechanism. The sensor is capable of measuring fields as small as 42 V/m using actuation signals on the order of 60 mV. 相似文献
10.
This paper considers the electro-mechanical interaction between a fiber and a matrix material in a 1–3 piezocomposite due to an axial load and electric charge applied to the fiber. The fiber–matrix interface is assumed to be mechanically imperfect and is represented by a spring-factor model. The interface is either electrically open- or short-circuited. The analytical general solutions corresponding to an infinite piezoelectric fiber with a vertical body force and an electric body charge are derived by using Fourier integral transforms. These solutions together with the analytical general solutions for a transversely isotropic elastic medium are used to formulate the fiber–matrix interaction problem. Selected numerical results for the fiber axial force and vertical electric field, and interfacial stresses are presented for representative 1–3 piezocomposites. The influence of the interface stiffness on the electro-mechanical load diffusion is also examined. 相似文献