A direct adaptive neural command controller design for an unstable helicopter

This paper presents an off-line (finite time interval) and on-line learning direct adaptive neural controller for an unstable helicopter. The neural controller is designed to track pitch rate command signal generated using the reference model. A helicopter having a soft inplane four-bladed hingeless main rotor and a four-bladed tail rotor with conventional mechanical controls is used for the simulation studies. For the simulation study, a linearized helicopter model at different straight and level flight conditions is considered. A neural network with a linear filter architecture trained using backpropagation through time is used to approximate the control law. The controller network parameters are adapted using updated rules Lyapunov synthesis. The off-line trained (for finite time interval) network provides the necessary stability and tracking performance. The on-line learning is used to adapt the network under varying flight conditions. The on-line learning ability is demonstrated through parameter uncertainties. The performance of the proposed direct adaptive neural controller (DANC) is compared with feedback error learning neural controller (FENC).     

Inspiratory flow shape clustering: an automated method to monitor upper airway performance during sleep

We describe an automated method for monitoring airflow dynamics in the upper airway of a sleeping subject. Its main task is to determine a set of inspiratory flow shape representatives and their relative incidence in a given respiratory airflow material. The flow shape clustering aims at reducing redundant information in the data, and thereby decreases the time needed to score overnight sleep recordings. Compared with previous computer-assisted systems, built on a pre-defined classification of prototype shapes, we require no a priori assumptions of the flow shape clusters to be discovered. The intrinsic flow shape clustering is performed with a modification of the Isodata algorithm, and the K-means clustering is used as a reference in comparison studies. The operation of the method is demonstrated on clinical sleep recordings both from patients with nocturnal breathing disorders and from non-symptomatic individuals. The feasible results obtained in the practical research design suggest that application of clustering algorithms to respiratory airflow measurements could give important insights into the subtle flow shape abnormalities underlying obstructive sleep-disordered breathing.     

FPGA-based real-time 3D image preprocessing for image-guided medical interventions

Minimally invasive image-guided interventions (IGIs) are time and cost efficient, minimize unintended damage to healthy tissue, and lead to faster patient recovery. One emerging trend in IGI workflow is to use volumetric imaging modalities such as low-dose computed tomography (CT) and 3D ultrasound to provide real-time, accurate anatomical information intraoperatively. These intraoperative images, however, are often characterized by quantum (in low-dose CT) or speckle (in ultrasound) noise and must be enhanced prior to any advanced image processing. Anisotropic diffusion filtering and median filtering have been shown to be effective in enhancing and improving the visual quality of these images. However, achieving real-time performance, as required by IGIs, using software-only implementations is challenging because of the sheer size of the images and the arithmetic complexity of the filtering operations. We present a field-programmable gate array-based reconfigurable architecture for real-time preprocessing of intraoperative 3D images. The proposed architecture provides programmable kernels for 3D anisotropic diffusion filtering and 3D median filtering within the same framework. The implementation of this architecture using an Altera Stratix-II device achieved a voxel processing rate close to 200 MHz, which enables the use of these processing techniques in the IGI workflow prior to advanced operations such as segmentation, registration, and visualization.

Methods for quantitative usability requirements: a case study on the development of the user interface of a mobile phone

Quantitative usability requirements are a critical but challenging, and hence an often neglected aspect of a usability engineering process. A case study is described where quantitative usability requirements played a key role in the development of a new user interface of a mobile phone. Within the practical constraints of the project, existing methods for determining usability requirements and evaluating the extent to which these are met, could not be applied as such, therefore tailored methods had to be developed. These methods and their applications are discussed.

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High pressure effect on MoS<Subscript>2</Subscript> and MoSe<Subscript>2</Subscript> single crystals grown by CVT method

Single crystals of MoS₂ and MoSe₂ were grown by chemical vapour transport method using iodine as a transporting agent and characterized by optical microscopy, energy dispersive analysis (EDAX), X-ray powder diffraction (XRD) and Hall mobility at room temperature. The variation of electrical resistance under pressure was monitored in a Bridgman anvil set-up up to 6.5 GPa to identify occurrence of any structural transition. MoS₂ and MoSe₂ do not undergo any structural transitions under pressure.     

X-ray diffraction studies of NbTe<Subscript>2</Subscript> single crystal

NbTe₂ is a member of transition metal dichalcogenide (TMDC) group. Single crystals of niobium ditelluride (NbTe₂) have been grown by a chemical vapour transport technique using iodine as transporting agent. The composition of the grown crystals was confirmed on the basis of energy dispersive analysis by X-ray (EDAX) and remaining structural characterization was also accomplished by X-ray diffraction (XRD) studies. Lattice parameters, volume and X-ray density have been carried out for the grown crystals. The particle size for a number of reflections has been calculated using Scherrer’s formula.     

A microgrooved membrane based gas–liquid contactor

This research presents an approach for applying microgrooved membranes for improved gas–liquid contacting. The study involves analysis of the performance of the microdevice by quantifying the flux enhancement for different membrane configurations. Two kinds of configurations, continuous and non-continuous grooves, were investigated. The microgrooves provide shear-free gas–liquid interfaces, which result in local slip velocity at the gas–liquid interface. Exploiting this physical phenomenon, it is possible to reduce mass transport limitations in gas–liquid contacting. An experimental study using grooved membranes suggests enhancement in flux up to 20–30 %. The flux enhancement at higher liquid flow rates is observed due to a partial shear-free gas–liquid interface. The performance of the membrane devices decreased with wetted microgrooves due to the mass transport limitations. The flow visualization experiments reveal wetting of the microgrooves at higher liquid flow rates. According to the numerical and experimental study, we have shown that microgrooved membranes can be employed to improve gas–liquid contacting processes.     

Tensilica如何验证处理器核心

由于半导体厂商不断地将摩尔定律往前推进，系统单芯片（SoC）设计正陷入混乱的验证泥潭。验证工作在百万门SoC设计中所占整体设计的比重，根据绝大多数的估计，约占50—80％。全定制的RTL硬件模块（hardware blocks）需要定制化的验证工具。在一颗数百万门的SoC上会有数十、成百？或上千个RTL模块，这些都需要验证测试集的建立。     

Vicker’s microhardness of Bi1?xSbx (x?=?0.05–0.30) crystals

The solid–liquid interface of Bi_1−x Sb _x crystal growth is very favorable for investigations of electron–phonon phenomena. Bismuth is a semimetal with high electron and hole mobilities. When Bi is doped with Sb in the range of 7–22 atomic percentage, it undergoes semimetal–semiconductor transition. Interest in Bi–Sb materials system has recently been stimulated due to promise of a new generation of thermoelectric materials based on these alloys. The starting materials used in this study, Bi and Sb, were both of 99.999% purity. The authors have studied microhardness of these crystals with the above said composition range. The crystals were grown using Zone melting method with 0.35 cm/h growth speed and 25 zone passes. The indentation method is the most widely used method for measurement of hardness of the crystals either of metallic or nonmetallic nature. This method does not require large specimens and even on a small specimen a number of measurements can be carried out. Microhardness indentation tests were carried out on the cleavage planes (111) of the Bi_1−x Sb _x (x = 0.5 to 0.30) crystals, using the Vickers diamond pyramidal indenter. The results of Vickers microhardness studies on Bi_1−x Sb _x (x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30) are presented in this paper.