On adaptive trajectory tracking of a robot manipulator usinginversion of its neural emulator

This paper is concerned with the design of a neuro-adaptive trajectory tracking controller. The paper presents a new control scheme based on inversion of a feedforward neural model of a robot arm. The proposed control scheme requires two modules. The first module consists of an appropriate feedforward neural model of forward dynamics of the robot arm that continuously accounts for the changes in the robot dynamics. The second module implements an efficient network inversion algorithm that computes the control action by inverting the neural model. In this paper, a new extended Kalman filter (EKF) based network inversion scheme is proposed. The scheme is evaluated through comparison with two other schemes of network inversion: gradient search in input space and Lyapunov function approach. Using these three inversion schemes the proposed controller was implemented for trajectory tracking control of a two-link manipulator. Simulation results in all cases confirm the efficacy of control input prediction using network inversion. Comparison of the inversion algorithms in terms of tracking accuracy showed the superior performance of the EKF based inversion scheme over others.     

Lay diagnosis and health-care-seeking behaviour for chest pain in south Asians and Europeans

BACKGROUND: South Asian people in the UK experience greater delays than Europeans in obtaining appropriate specialist management for heart disease, but the causes are not known. We investigated whether south Asians and Europeans interpret and act upon anginal symptoms differently. METHODS: We randomly selected 2000 people from general practitioners' (family physicians) lists in London, UK, to receive a questionnaire that included a short fictional case history of an individual with possible anginal pain and asked how respondents would react to experiencing it. A second questionnaire seeking information on medical history, attitudes to health, and demography was sent later. The main outcome measure was the proportion who said they would seek immediate care (hospital emergency department or general practitioner) for the pain described in the case scenario. FINDINGS: The rate of response to both questionnaires was 60.2% (903 of 1500 who received both), 553 responders were of European origin, 124 were Hindu, and 235 were Sikh. There were no differences between the ethnic groups in the proportion identifying the pain as cardiac, but south Asians would be more anxious about the pain than would Europeans. Of the men, 55 (23%) Europeans, 20 (38%) Hindus, and 52 (47%) Sikhs said they would seek immediate care (p < 0.0001 for heterogeneity); of women, 77 (24%), 25 (35%), and 58 (46%), respectively, would seek immediate care (p < 0.0001). After adjustment for confounding variables the odds ratio for seeking immediate care in Hindus compared with Europeans was 2.67 (95% CI 1.49-4.73) and that for Sikhs compared with Europeans was 3.18 (1.98-5.12). INTERPRETATION: Hindus and Sikhs reported a greater likelihood of seeking immediate care for anginal symptoms than Europeans; this finding indicates that barriers to cardiology services for south Asians are unrelated to difficulties in interpretations of symptoms or willingness to seek care. Improvement of awareness of heart disease may not decrease delays in obtaining care. Service-related explanations must be explored, such as general practitioners' difficulties in arriving at a diagnosis or differences in management because of ethnic origin.     

Localization of critical histidyl residues required for vinblastine-induced tubulin polymerization and for microtubule assembly

Vinblastine-induced tubulin polymerization is electrostatically regulated and shows pH dependence with a pI approximately 7.0 suggesting the involvement of histidyl residues. Modification of histidyl residues of tubulin with diethylpyrocarbonate (DEPC) at a mole ratio of 0.74 (DEPC/total His residues) for 3 min at 25 degreesC completely inhibited vinblastine-induced polymerization with little effect on microtubule assembly. Under these conditions DEPC reacts only with histidyl residues. For complete inhibition two histidyl residues have to be modified. Demodification of the carboxyethyl histidyl derivatives by hydroxylamine led to nearly complete recovery of polymerization competence. Labeling with [14C]DEPC localized both of these histidyl residues on beta-tubulin at beta227 and beta264. Similarly, tubulin modification with DEPC for longer times (8 min) resulted in complete inhibition of microtubule assembly, at which time approximately 4 histidyl residues had been modified. This inhibition by DEPC was also reversed by hydroxylamine. The third histidyl residue was found on alpha-tubulin at alpha88. Thus, two charged histidyl residues are obligatorily involved in vinblastine-induced polymerization, whereas a different histidyl residue on a different tubulin monomer is involved in microtubule assembly.     

Performability modeling with UltraSAN

The utility of stochastic activity networks (SANs) for performability evaluation is discussed. UltraSAN, a new graphical, X-Windows-based software package that uses SANs, is described. UltraSAN incorporates three innovations: a class of SAN-level performability variables common to both analytical and simulation solution methods, methods that use the performability-variable choice and the SAN structure to greatly reduce the size of the stochastic process required for an analytical solution, and methods that use the performability-variable choice and the SAN structure to reduce the number of activities checked on each state change, thus speeding the simulation. The UltraSAN modeling framework, organization, and user interface are examined. Model construction and solution are described     

A dynamic liquid support system for continuous electrospun yarn fabrication

Electrospinning is known to be a highly versatile process which is able to produce fibers made out of different compositions with diameter of a few microns down to several nanometers. Current electrospinning technology generally involves the deposition of fibers onto a solid substrate although in some cases, a liquid coagulation bath is used to collect the fibers. However, a liquid collector may offer several advantages over a solid substrate. A novel electrospun fiber manipulation process through the use of a water vortex is described in this communication where continuous yarn was made from electrospun fibers. Preliminary studies on some parameters such as solution feed rate and solution concentration and their impact on fabrication of the yarn and the fiber morphology were carried out.     

A Novel Dynamic and Scalable Caching Algorithm of Proxy Server for Multimedia Objects

This paper presents a novel dynamic and scalable caching algorithm of proxy server with a finite storage size for multimedia objects. Among the multimedia such as text, image, audio and video, video is a dominant component in terms of the performance of proxy server due to its traffic characteristics. For the fast caching process, caching sequences for videos are obtained to decrease both the buffer size and the required bandwidth and saved into metafiles in advance. Then, we present a novel caching and replacing algorithms for multimedia objects based on the metafiles. Finally, experimental results are provided to show the superior performance of the proposed algorithm.     

A Multicommodity Integrated Freight Origin–destination Synthesis Model

This paper introduces a multi-commodity, single (generic) vehicle formulation of freight ODS model that combines a commodity-based model to estimate loaded truck trips and a complementary model of empty trips. This integration is important because explicit modeling of empty trips—that account for 30% to 40% of total truck trips—is required to avoid significant errors in the estimation of the directional traffic. The formulation is then applied to a case study. Two cases of the proposed model are studied. The first one uses total traffic in the estimation; while the second one is based on loaded and empty traffic. The results conclusively show that the models that consider an empty trip submodel significantly outperform the model that does not in their ability to replicate the observed traffic counts. The comparison between the results from the multi-commodity ODS and the single commodity ODS previously developed by the authors indicates that the multi-commodity formulation brings about substantial reductions in the error associated with the estimation of observed traffic counts. These reductions, in the order of 20% for empty traffic and 40% for loaded and total traffic, seem larger than the spurious improvement to be expected from the increased number of parameters, suggesting that the multi-commodity ODS formulation performs better. The results also show some minor improvements in the ability of the multi-commodity ODS formulation to estimate the OD matrices. In terms of the model's ability to correctly estimate the “true” value of the parameters of the models used, i.e., the parameter values estimated by calibrating the model directly from the OD data, it was found that the multicommodity ODS procedure is able to provide fairly good estimates Noortman and van Es's model parameters, though the parameters of the gravity models that came out to be quite different than the “true” values. The overall assessment of the formulation introduced here is that it represents a solid improvement with respect to comparable techniques.     

Preparation of poly(methyl methacrylate) nanocomposites with superior impact strength

A chemically stable syrup of poly(methyl methacrylate) in its monomer was prepared with a suitable dual‐initiating system. Nanoalumina particles were prepared by the autoignition of aluminum nitrate with urea and were made compatible with the organic medium by chemical modification with methacrylol isocyanate. The polymer syrup prepared in this way was applied between two poly(methyl methacrylate) sheets (each 10 cm × 10 cm × 2 mm), and the composite thus prepared was tested with a bullet‐firing machine and a drop‐weight‐impact testing machine. The impact strength measurements of the two‐plate composite from both of these procedures showed that the impact resistance doubled in the case of nanoalumina. The modeling of the damage to the multilayered composite by the critical impact energy was performed with the relation E = pn² + qn + r, where E is the impact energy, p, q, and r are constants, and n is the number of layers. Experiments showed that the presence of nanoparticles in the adhesive increased the value of the constants. The 10‐layer composite was further tested with a 0.32 Indian Ordinance Factory (IOF) revolver with a bullet mass of 9.9 g and a muzzle velocity of 236 ± 7 m/s (muzzle energy = 275 J) from a 10‐m distance, which produced an ordinary indentation with no penetration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Optimisation of baking parameters of chapati with respect to vitamin B1 and B2 retention and quality

Vitamin losses during processing of cereal grains and their food products play an important role in human vitamin intake. Therefore, experiments were conducted to optimise the baking parameters for chapati, a flat unleavened, hot-plate-baked product of Asian diet. In the experiments, whole-wheat flour (100% extraction rate) was used for the preparation of chapaties. Central composite rotatable design with three independent variables (thickness of dough sheet, time as well as temperature of baking) at five levels and nine dependent variables, i.e. vitamin B₁ and B₂ content, textural properties and overall acceptability scores, were used to conduct the experiments. The ranges for three independent variables were: thickness, 2.5–4.5 mm; time, 2.0–3.0 min; and temperature, 200–240 °C. Thickness of the dough sheet had a significant ( P  ≤ 0.05) positive effect on vitamin retention, while the temperature had greater negative effect as compared with the time of baking. Based on compromise optimisation, optimum conditions for baking of chapati, especially with respect to vitamin retention were: thickness of dough sheet 3.2 mm, time of baking 2.1 min and baking temperature 216.3 °C.     

Dependent and multimode failures in reliability evaluation ofextra-stage shuffle-exchange MINs

Previous reliability evaluations for multistage interconnection networks (MINs) assumed that “all failures are statistically-independent and that no degraded operational modes exist for switches”, though these assumptions are not realistic. For example, researchers have described instances of statistically-dependent failures, or fault side-effects, in some MINs. This paper presents efficient algorithms for terminal, broadcast, and K-terminal reliability evaluation of the shuffle-exchange network with an extra stage (SENE), a redundant-path MIN, under assumptions that allow statistical-dependence between failures and degraded operational modes for switches. A modified shock-model incorporates failure statistical-dependency and multiple operational modes into the reliability evaluation. For an N×N SENE, the reliability algorithms and their run-times are: terminal and broadcast →O(log(N)), and K-terminal→O(|K|·log(N))