Efficiently Generating Random Bits from Finite State Markov Chains

The problem of random number generation from an uncorrelated random source (of unknown probability distribution) dates back to von Neumann's 1951 work. Elias (1972) generalized von Neumann's scheme and showed how to achieve optimal efficiency in unbiased random bits generation. Hence, a natural question is what if the sources are correlated? Both Elias and Samuelson proposed methods for generating unbiased random bits in the case of correlated sources (of unknown probability distribution), specifically, they considered finite Markov chains. However, their proposed methods are not efficient or have implementation difficulties. Blum (1986) devised an algorithm for efficiently generating random bits from degree-2 finite Markov chains in expected linear time, however, his beautiful method is still far from optimality on information-efficiency. In this paper, we generalize Blum's algorithm to arbitrary degree finite Markov chains and combine it with Elias's method for efficient generation of unbiased bits. As a result, we provide the first known algorithm that generates unbiased random bits from an arbitrary finite Markov chain, operates in expected linear time and achieves the information-theoretic upper bound on efficiency

Stable inversion based output tracking control of robotic systems

This thesis addresses stable inversion based output tracking control and its applications to robotic systems. It considers the non-causal invertibility (stable inversion) problem of control systems in its various aspects including properties of stable inverses and algorithms for constructing stable inverses. Then, the stable inversion approach is applied to solve a control problem of long-standing interest: output tracking control for non-minimum phase nonlinear systems;A minimum energy property of stable inverses is firstly established. The property claims that given any desired output trajectory, out of infinitely many possible inverse solutions, the one provided by the stable inversion process is the only one that has finite energy. Based on this property, a numerical procedure is developed to provide an efficient approach to construct stable inverses;Secondly, a new output tracking control design is developed. The design incorporates stable inverses and assumes a controller structure of feed-forward plus feedback. It achieves high precision tracking together with closed-loop stability. Furthermore, when system uncertainties are considered and assumed to satisfy the so-called matching conditions , a modified controller structure is presented and the corresponding robust tracking performance is discussed;Finally, the stable inversion based tracking control design is applied to three flexible robotic systems. The first study is output tracking control of a flexible-joint robot. The application demonstrates how the new design deals with the undesirable non-minimum phase property and achieves desired output tracking. The second application is tip trajectory tracking for a two-flexible-link manipulator. This thesis, for the first time, addresses the problem of stable tip trajectory tracking without any transient or steady-state errors for such non-minimum phase systems. In the third application, a new optimal motion control strategy for a flexible space robot is presented. The space robot system is assumed to consist of a two-link flexible manipulator attached to rigid space-craft. Optimality is in the sense that a performance index measured by maneuvering time, control effort, and structural vibrations is minimized while the interference from the manipulator to spacecraft is kept satisfactorily small;Studies on three applications demonstrate that the stable inversion based control design is very effective on output tracking for various robotic systems. This approach is expected to perform equivalently well for many other realistic non-minimum phase nonlinear systems

Using coal rejects and tailings as infills for standing supports in underground gateroads

Laboratory tests were conducted to investigate the uniaxial compressive strength (UCS) of two types of potential infill materials for standing supports. While one type of infill material was made from coal reject fines and a cementitious grout, the other was a mixture of tailings and a cementitious grout. 81 cylindrical specimens with a 50 mm diameter and 100 mm height were prepared and tested. The effect of various water-to-grout (w/g) ratios and grout-to-coal reject fines/tailings mix ratios on the UCS of the infills were investigated. Test results indicated that the strength of both infills was adversely affected by the w/g ratio. In addition, when the volume ratio of the coal reject fines in the infill was not greater than 50%, the strength of the infill was similar to that of the control group specimens. Interestingly, almost all the infills made of tailings and grout had a greater UCS when compared with the control group. The infill made from 50% tailings and 50% grout with the w/g ratio of 1.2 achieved the highest strength enhancement ratio, being 1.92 times the UCS of the control group

Research on Tracking and Synchronization of Uncertain Chaotic Systems

The tracking and synchronization problem of uncertain chaotic system, which is considered to be applied in secure communication in the future by many researchers, is considered in this paper. A double integral sliding mode controller is adopted to cope with the uncertainties of the chaotic system. Adaptive and robust strategies, such as Nussbaum gain method, are used to solve the unmodeled dynamic problem and unknown control direction problem. Meanwhile, the stability of the whole system is guaranteed by constructing of a big Lyapunov function for the whole system. Finally, a four dimension super-chaotic system is used as an example to do the numerical simulation and it testifies the rightness and effectiveness of the proposed method

Removal of Methyl Orange from Aqueous Solution by Calcium Alginate/Multi-walled Carbon Nanotubes Composite Fibers

AbstractAdsorbent of calcium alginate/multi-walled carbon nanotubes (CA/MWCNTs) composite fiber was prepared by wet spinning. Adsorptions of methyl orange (MO) anionic dyes onto CA/MWCNTs composite fiber were investigated with respect to MWCNTs content, initial dye concentration and pH values. Results illustrated that introduction of MWCNTs could obviously increase the adsorption capacity (qe) of MO onto CA/MWCNTs composite fibers. The equilibrium adsorption data were analyzed using two widely applied isotherms: Langmuir and Freundlich. The results showed that Langmuir isotherm fitted the experimental results well

Experimental study on the uniaxial compressive behaviour of a fibre reinforced polymer standing support

Laboratory tests were conducted to investigate the behaviour of an innovative fibre reinforced polymer (FRP) standing support subject to uniaxial compression. The FRP standing support consisted of two major components: 1) the internal cylindrical concrete column made of coal rejects and a cementitious grout, and 2) the external FRP jacket. A total of ten specimens with different water-to-cementitious grout (w/c) ratios and various layers of FRP confinement were prepared and tested. As expected, an increased w/c ratio adversely affected the compressive strength of the internal cylindrical column. The compressive strength of the column decreased from 15.9 MPa to 13.4 MPa when the w/c ratio increased from 1 to 1.2. Test results also indicated that the columns became much stronger and more deformable when confined with an FRP jacket. In contrast to the unconfined control specimens, the columns confined with two layers of FRP experienced an increase of approximately 150% in maximum compressive strength at approximately 500% higher axial deformation. A further growth in strength and deformability was also observed when the columns were confined with four layers of FRP. The maximum strength and deformability achieved were up to 49.6 MPa and 7.2% respectively

Effects of in ovo feeding of chlorogenic acid on antioxidant capacity of postnatal broilers

In this study, chlorogenic acid (CGA) was injected into the amniotic cavity of chicken embryos to study the effects of in ovo feeding of CGA on the antioxidant capacity of postnatal broilers. On the 17th day of embryonic age, a total of 300 healthy broiler fertile eggs with similar weights were randomly subjected to five groups as follows; in ovo injection with 0.5 ml CGA at 4 mg/egg (4CGA) or 7 mg/egg (7CGA) or 10 mg/egg (10CGA), or sham-injection with saline (positive control, PC) or no injection (negative control, NC). Each group had six replicates of ten embryos. Six healthy chicks with similar body weights hatched from each replicate were selected and reared until heat stress treatment (35°C ± 1°C, 8 h/d) at 28–42 days of age. The results showed that there was no significant difference in the hatching rate between the groups (p > 0.05). After heat stress treatment, 4CGA group showed an improved intestinal morphology which was demonstrated by a higher villus height in the duodenum and a higher villus height/crypt depth ratio in the jejunum, compared with the NC group (p < 0.05). The antioxidant capacity of chickens was improved by in ovo feeding of CGA since 4CGA decreased the plasma content of malondialdehyde (MDA) (p < 0.05), whereas, it increased the superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) activities compared with NC group (p < 0.05). Also, the MDA content of the different injection groups had a quadratic effect, with the 4CGA group having the lowest MDA content (Pquadratic < 0.05). In the duodenum, 4CGA injection significantly increased the mRNA expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (H O -1), glutathione synthetase (GSS), and SOD1 compared to the NC and PC groups (p < 0.05). The mRNA expressions of glutathione reductase (GSR) and GPX7 were significantly increased in all CGA-treated groups compared with the PC group (p < 0.05), while the mRNA expression of CAT was significantly increased by 4CGA group than the NC group (p < 0.05). The mRNA expressions of epigenetic-related genes, ten eleven translocation 1 and 2 (Tet1 and Tet2), and DNA-methyltransferase 3 alpha (DNMT3A) in the duodenum of 4CGA injected group was significantly increased compared with the NC and PC groups (p < 0.05). The mRNA expressions of Nrf2, SOD1, and Tet2 showed a significant quadratic effects with the 4CGA group having the highest expression (Pquadratic < 0.05). In conclusion, in ovo feeding of CGA alleviated heat stress-induced intestinal oxidative damage. Injection with CGA of 4 mg/egg is considered most effective due to its actions in improving intestinal antioxidant capacity, especially in the duodenum. The antioxidant effects of in ovo CGA on postnatal heat-stressed broilers may be related to its regulation of epigenetic mechanisms. Thus, this study provides technical knowledge to support the in ovo feeding of CGA to alleviate oxidative stress in postnatal heat-stressed broilers