Dynamic Modeling and Control System Design for Shape Memory Alloy Actuators

Shape memory alloy (SMA) is a type of smart material which remembers its original state. It is light weight and small, and known to provide high contraction force with low noise. Its application has wide range from robotics to medical science. One of its potential applications in space is a supporting system of membrane structure that can be used as synthetic aperture radar (SAR) antenna to achieve high flatness. It exhibits nonlinear phenomena called hysteresis when it's electrically heated. Hysteresis is a nonlinear phenomenon that refers to the dependence of a physical system on the environment. Hysteresis in SMA causes a major difficulty in control system design. Un-modeled or poorly modeled hysteresis introduces inaccuracy in tracking and the performance of the system. Experimental test bench is constructed for one set of SMA actuators that resembles the membrane structure's supporting system. Hysteresis is obtained by running open loop test with the test bench. Dynamic model of the SMA wires is developed using classical Preisach model and modified Maxwell model. Then the inverse model is implemented in feed-forward loop to compensate for nonlinear hysteresis. Simple feedback controllers are added to correct the modeling errors. Experimental results reveal that the error is significantly reduced when comparing feedback controller with hybrid feedback and feed-forward controller

Interaction of psychological, physiological and neuronal processes in functional dyspepsia

Functional dyspepsia is characterized by postprandial fullness, early satiation, epigastric pain, bloating, and nausea symptoms in the absence of structural changes in the gastrointestinal tract. Numerous works have been performed to identify the peripheral characteristics of functional dyspepsia and its association with dyspeptic symptoms, including changes of gastric motility, visceral sensitivity, secretion of hormones, functions of immune system. However, the pathophysiological mechanisms involved and standard treatment strategies are still lacking. The role of the dysfunction of the brain-gut axis and the effect of the food ingestion in the gastrointestinal symptoms of functional dyspepsia patients have therefore been attracting more interest in recent years. How the food is processed differently in the peripheral and in the central nervous system in functional dyspepsia has, however, received little attention in comparison to other functional gastrointestinal disorders. In this thesis, we used various approaches to examine the physiological and neuronal mechanisms in functional dyspepsia patients. We commenced by summarizing previous functional neuroimaging studies to establish their limitations. To bridge the resulting research gap, we investigated physiological and attentional responses to visual food cues, and measured the altered brain activity before and after the food ingestion in functional dyspepsia patients. In the paper I, we reviewed the current status of brain research related to functional dyspepsia and were able to clearly show a knowledge gap regarding neural mechanisms of food-related factors in functional dyspepsia patients. In paper II, we introduced how to design the neuroimaging study and interpret the results of it to clinicians. In paper III, we report findings of an eyetracking and behavioral study on functional dyspepsia patients. The patients showed 1) greater dyspeptic symptoms even after ingestion of a lower calorie and food intake from standard breakfast; 2) decreased pleasantness ratings to food images; and 3) reduced visual attention to food images in comparison to healthy controls. In paper IV, we report findings of a functional magnetic resonance imaging study during meal ingestion (yoghurt with different fat content and label info) in functional dyspepsia patients. The patients showed 1) greater abdominal pain, burning, and discomfort after high fat labeled yogurt ingestion than after low fat labeled yogurt ingestion irrespective of fat content, 2) increased activity in occipital areas before and after ingestion irrespective of fat content and label and increased activity in the middle frontal gyrus before ingestion, 3) increased functional connectivity between the insula and the precuneus after ingestion of yogurt with low fat label, and 4) greater nausea-related increased functional connectivity between the insula and the occipital gyrus after ingestion of high fat yogurt than of low fat yogurt. Furthermore, bidirectional influences between quality of life and depression, as mediated by dyspeptic symptoms and the impact of food craving on the amplitude of brain activity in the middle frontal gyrus, as mediated by depression in functional dyspepsia patients were recorded. In conclusion, the abnormal dietary behavior, reduced positive emotional response and visual attention to food images, and the role of cognitive perception of fat on the aggravation of dyspeptic symptoms should be considered in clinics and in research for functional dyspepsia

Domain Reduction Strategy for Non Line of Sight Imaging

This paper presents a novel optimization-based method for non-line-of-sight (NLOS) imaging that aims to reconstruct hidden scenes under various setups. Our method is built upon the observation that photons returning from each point in hidden volumes can be independently computed if the interactions between hidden surfaces are trivially ignored. We model the generalized light propagation function to accurately represent the transients as a linear combination of these functions. Moreover, our proposed method includes a domain reduction procedure to exclude empty areas of the hidden volumes from the set of propagation functions, thereby improving computational efficiency of the optimization. We demonstrate the effectiveness of the method in various NLOS scenarios, including non-planar relay wall, sparse scanning patterns, confocal and non-confocal, and surface geometry reconstruction. Experiments conducted on both synthetic and real-world data clearly support the superiority and the efficiency of the proposed method in general NLOS scenarios

Fourier Series of the Periodic Bernoulli and Euler Functions

We give some properties of the periodic Bernoulli functions and study the Fourier series of the periodic Euler functions which are derived periodic functions from the Euler polynomials. And we derive the relations between the periodic Bernoulli functions and those from Euler polynomials by using the Fourier series

Decreased Peripheral and Central Responses to Acupuncture Stimulation following Modification of Body Ownership

Acupuncture stimulation increases local blood flow around the site of stimulation and induces signal changes in brain regions related to the body matrix. The rubber hand illusion (RHI) is an experimental paradigm that manipulates important aspects of bodily self-awareness. The present study aimed to investigate how modifications of body ownership using the RHI affect local blood flow and cerebral responses during acupuncture needle stimulation. During the RHI, acupuncture needle stimulation was applied to the real left hand while measuring blood microcirculation with a LASER Doppler imager (Experiment 1, N = 28) and concurrent brain signal changes using functional magnetic resonance imaging (fMRI; Experiment 2, N = 17). When the body ownership of participants was altered by the RHI, acupuncture stimulation resulted in a significantly lower increase in local blood flow (Experiment 1), and significantly less brain activation was detected in the right insula (Experiment 2). This study found changes in both local blood flow and brain responses during acupuncture needle stimulation following modification of body ownership. These findings suggest that physiological responses during acupuncture stimulation can be influenced by the modification of body ownership

Thiol-linked peroxidase activity of human ceruloplasmin

AbstractHuman ceruloplasmin exhibited different antioxidant effects according to the electron donors in a metal-catalyzed oxidation system. Purified ceruloplasmin did not play a significant role in the protection of DNA strand breaks in the ascorbate/Fe3+/O2 system. However, when ascorbates were replaced with a thiol-reducing equivalent such as dithiothreitol, DNA strand breaks were significantly prevented by the same amount of ceruloplasmin. Ceruloplasmin did not catalyze the decomposition of H2O2 in the absence of reduced glutathione. On the contrary, ceruloplasmin showed a potent peroxidase ability to destroy H2O2 in the presence of reduced glutathione. In conclusion, the removal of H2O2 by human ceruloplasmin is not simply stoichiometric but thiol-dependent