Simulation of a feedback and adaptive systems

A computer approach for simulating a feedback system and its adaptive versions is presented. It is conceived with recursion formulas to describe the interconnected elements of the system. The potential of the approach is explored by applying it to an existing practical system. It is then enhanced by a performance analysis leading to a provision of a unified system evaluation technique. The approach permitted experimentation with different combination of system parameters, system inputs and system configuration. The efficiency of the approach suggets its suitability for a rational engineering design of systems.     

Novel Structural Modulation in Ceramic Sensors Via Redox Processing in Gas Buffers

High selectivity, enhanced sensitivity, short response time, and long shelf-life are some of the key features sought in the solid-state ceramic-based chemical sensors. As the sensing mechanism and catalytic activity are predominantly surface-dominated, benign surface features in terms of small grain size, large surface area, high aspect ratio and, open and connected porosity, are required to realize a successful material. In order to incorporate these morphological features, a technique based on rigorous thermodynamic consideration of the metal/metal oxide coexistence is described. By modulating the oxygen partial pressure across the equilibrium M/MO proximity line, formation and growth of new oxide surface on an atomic/submolecular level under conditions of "oxygen deprivation," with exotic morphological features, has been achieved in potential sensor materials. This paper describes the methodology and discusses the results obtained in the case of potential semiconducting ceramic oxide-based carbon monoxide and hydrogen sensors with enhanced characteristics.     

Calcified right ventricular fibroma causing outflow obstruction. Report of a case with successful excision

A 5-year-old boy with clinical findings of pulmonic stenosis was found to have a large calcified mass in the right ventricular outflow region and a gradient of 120 mm Hg between the right ventricle and the pulmonary artery. At surgery, an ovalshaped tumor attached to the interventricular septum and obstructing the right ventricular outflow tract was removed. The child survived and is doing well. Histologically, the tumor had the characteristics of fibroma. A hemodynamic study three months after surgery showed almost complete abolishment of the gradient. To our knowledge this is the fifth reported case of calcified right ventricular fibroma with successful operation. In childhood intracardiac calcifications, together with obstruction, are highly suggestive of this lesion.     

A finite element large displacement analysis of stiffened plates

A finite element analysis of the large deflection behaviour of stiffened plates using the isoparametric quadratic stiffened plate bending element is presented. The evaluation of fundamental equations of the stiffened plates is based on Mindlin's hypothesis. The large deflection equations are based on von Kármán's theory. The solution algmrithm for the assembled nonlinear equilibrium equations is based on the Newton-Raphson iteration technique. Numerical solutions are presented for rectangular plates and skew stiffened plates.     

Impulse Response of a Meteor Burst Communications Channel Determined by Ray-Tracing Techniques

Ray-tracing techniques are used to derive the impulse response at VHF of a meteor burst communications channel. An approach to analyze the effects of multipath arising from wind shear is also presented and is applied to a simplified model of trail distortion. Within the limitations of the models adopted, we have found that a single path with a spread of approximately 0.2 μs adequately describes the channel behavior within roughly half a second from trail formation, and that a multipath structure with several paths and a total multipath spread of approximately 2 μs is typically associated with the channel at later times, when the wind shear substantially affects the trail shape. These results are consistent with experimental findings according to which a meteor trail communications channel is capable of transmitting beyond-the-horizon bursts of television images of broadcast quality typically for a fraction of a second after trail formation.     

Enhanced HBsAb production in pathogenesis of fulminant viral hepatitis type B

The possible importance of humoral immunity in the pathogenesis of fulminant hepatitis was investigated by comparing 17 patients with fulminant hepatitis type B with 20 patients with severe but non-fulminant disease. Hepatitis B surface antigen (HBsAg) was cleared from the serum significantly faster (P less than 0-001) in those with fulminant hepatitis, and in 41% anti-HBsAg (HBsAb) was detectable by radioimmunoassay (RIA) at presentation. In all 11 sera from patients with fulminant hepatitis that were examined by electron microscopy aggregates of HBsAg and HBsAb were seen. In contrast, HBsAb was never detected by RIA in those with non-fulminant hepatitis, and in only one serum specimen (5%) were aggregates seen on electron microscopy. A significant sex difference between fulminant and non-fulminant hepatitis was observed, 65% of patients with fulminant hepatitis but only 15% of patients with non-fulminant hepatitis being women (P less than 0-01). An enhanced production of HBsAb in fulminant hepatitis, by leading to free HBsAb in portal blood, may cause an Arthus reaction in the sinusoids of the liver with ensuing ischaemic necrosis of hepatocytes.     

An information fidelity criterion for image quality assessment using natural scene statistics.

Measurement of visual quality is of fundamental importance to numerous image and video processing applications. The goal of quality assessment (QA) research is to design algorithms that can automatically assess the quality of images or videos in a perceptually consistent manner. Traditionally, image QA algorithms interpret image quality as fidelity or similarity with a "reference" or "perfecft" image in some perceptual space. Such "full-referenc" QA methods attempt to achieve consistency in quality prediction by modeling salient physiological and psychovisual features of the human visual system (HVS), or by arbitrary signal fidelity criteria. In this paper, we approach the problem of image QA by proposing a novel information fidelity criterion that is based on natural scene statistics. QA systems are invariably involved with judging the visual quality of images and videos that are meant for "human consumption." Researchers have developed sophisticated models to capture the statistics of natural signals, that is, pictures and videos of the visual environment. Using these statistical models in an information-theoretic setting, we derive a novel QA algorithm that provides clear advantages over the traditional approaches. In particular, it is parameterless and outperforms current methods in our testing. We validate the performance of our algorithm with an extensive subjective study involving 779 images. We also show that, although our approach distinctly departs from traditional HVS-based methods, it is functionally similar to them under certain conditions, yet it outperforms them due to improved modeling. The code and the data from the subjective study are available at.     

Echocardiographic diagnosis of supravalvular aortic stenosis

The echocardiographic features of supravalvular aortic stenosis seen in a patient with valvular aortic and multiple pulmonary branch stenosis are described. Since patterns of valvular, discrete subvalvular, and supravalvular aortic stenosis can be recognized by echocardiography, it is now possible to screen close relatives of patients having supravalvular aortic stenosis and pulmonary branch stenosis by this non-invasive technic.