A computationally efficient norm optimal iterative learning control approach for LTV systems

This paper proposes a computationally efficient iterative learning control (ILC) approach termed non-lifted norm optimal ILC (N-NOILC). The objective is to remove the computational complexity issues of previous 2-norm optimal ILC approaches, which are based on lifted system techniques, while retaining the iteration domain convergence properties. The computational complexity needed to implement the proposed method scales linearly with the trial length. Therefore, the approach can be implemented on controlled processes having long trial durations and high sampling rates. Robustness is accomplished by adding a penalty term on the control input in the cost function. Simulations are presented to verify and validate the features of the proposed method.     

The ups and downs of protein topology; rapid comparison of protein structure

Protein topology can be described at different levels. At themost fundamental level, it is a sequence of secondary structureelements (a `primary topology string'). Searching predictedprimary topology strings against a library of strings from knownprotein structures is the basis of some protein fold recognitionmethods. Here a method known as TOPSCAN is presented for rapidcomparison of protein structures. Rather than a simple two-letteralphabet (encoding strand and helix), more complex alphabetsare used encoding direction, proximity, accessibility and lengthof secondary elements and loops in addition to secondary structure.Comparisons are made between the structural information contentof primary topology strings and encodings which contain additionalinformation (`secondary topology strings'). The algorithm isextremely fast, with a scan of a large domain against a libraryof more than 2000 secondary structure strings completing in     

Increased α-linolenic acid intake increases tissue α-linolenic acid content and apparent oxidation with little effect on tissue docosahexaenoic acid in the guinea pig

The essential fatty acids do not have identical roles in nutrition. Linoleic acid (LA) accumulates throughout the body of most mammals, whereas α-linolenic acid (ALA) is rarely found in tissue lipids to the same extent as LA. It has been argued that this is the result of metabolism of ALA to docosahexaenoic acid (DHA) or that ALA is rapidly β-oxidized to acetyl CoA and CO₂. In this study, we consider the effect of high and low ALA levels on the tissue distribution of ALA and other n-3 polyunsaturated fatty acids (PUFA) in all tissues. Guinea pigs were fed one of two defined diets for 3 wk from wearning with both diets containing 1.8% (by weight) of LA and either 1.7% ALA or 0.03% ALA. The high ALA diet was associated with significantly increased ALA levels in all tissues except the brain and significantly increased levels of long-chain n-3 PUFA in all tissues except intestines, brain, carcass, and skin. The long-chain n-3 PUFA content of the whole body was less than 5% of that of the ALA content in both diet groups, and the major long-chain n-3 PUFA (>66% of total) in the body was 22∶5n−3. The brain was the only tissue where the DHA content exceeded that of 22∶5n−3. On the low ALA diet, there appeared to be conservation of ALA based on a comparison of the ratio of LA to ALA in the tissues compared with that in the diet. On the high ALA diet there was a loss of ALA relative to LA in the tissues compared with the diet. These studies suggest that the low levels of tissue ALA in the guinea pig are likely the result of β-oxidation or excretion via the skin and fur rather than metabolism to DHA.     

Perceiving,learning, and exploiting object affordances for autonomous pile manipulation

Autonomous manipulation in unstructured environments will enable a large variety of exciting and important applications. Despite its promise, autonomous manipulation remains largely unsolved. Even the most rudimentary manipulation task—such as removing objects from a pile—remains challenging for robots. We identify three major challenges that must be addressed to enable autonomous manipulation: object segmentation, action selection, and motion generation. These challenges become more pronounced when unknown man-made or natural objects are cluttered together in a pile. We present a system capable of manipulating unknown objects in such an environment. Our robot is tasked with clearing a table by removing objects from a pile and placing them into a bin. To that end, we address the three aforementioned challenges. Our robot perceives the environment with an RGB-D sensor, segmenting the pile into object hypotheses using non-parametric surface models. Our system then computes the affordances of each object, and selects the best affordance and its associated action to execute. Finally, our robot instantiates the proper compliant motion primitive to safely execute the desired action. For efficient and reliable action selection, we developed a framework for supervised learning of manipulation expertise. To verify the performance of our system, we conducted dozens of trials and report on several hours of experiments involving more than 1,500 interactions. The results show that our learning-based approach for pile manipulation outperforms a common sense heuristic as well as a random strategy, and is on par with human action selection.     

A memetic algorithm for the capacitated m-ring-star problem

The Capacitated m-Ring-Star Problem (CmRSP) models a network topology design problem in the telecommunications industry. In this paper, we propose to solve this problem using a memetic algorithm that includes a crossover operation, a mutation operation, a local search involving three neighborhood operators, and a population selection strategy that maintains population diversity. Our approach generates the best known solutions for 131 out of 138 benchmark instances, improving on the previous best solutions for 24 of them, and exhibits more advantages on large benchmark instances when compared with the best existing approach. Additionally, all existing algorithms for this problem in literature assume that the underlying graph of the problem instance satisfies the triangle inequality rule; our approach does not require this assumption. We also generated a new set of 36 larger test instances based on a digital data service network price structure to serve as a new benchmark data set for future researchers.     

Chlorophyll and plankton of the Gulf coastal waters of Saudi Arabia bordering a desalination plant

As on land, plants are the real producers in the sea, and on them depend all marine living resources and the basic sustainability of ecosystems. Primary production is performed by chlorophyll-bearing plants ranging from the tiny phytoplankton to the giant kelps through the process ofphotosynthesis. Zooplankton play an important role as secondary producers, and together with phytoplankton they support the vast assemblages of marine food chain with all their diversity and complexity. Data on chlorophyll pigments, phytoplankton and zooplankton are regarded as a sound basis for environmental appraisal of ecosystems. This paper presents a set of data collected from the Saudi Arabian coastal waters near the desalination plants in AI-Jubail. Materials were collected from six different sites covering the intake and discharge zones during cruises carried out in 1997-1998. Analyses of chlorophyll pigments were made using the spectrophotometric method. Plankton samples were collected using a Nansen plankton net with a mesh size of 75 μ and analyzed following standard procedures. Chlorophyll a, b, c and phaeophytin are the most commonly occurring pigments in seawater. Their concentrations showed wide fluctuation. The phytoplankton community was composed of 35 genera representing the Diatoms, Dinoflagellates and blue- green algae. Zooplankton were composed ofProtozoa, Coelenterata, Ctenophora, Aschelminthes, Annelida, Mollusca, Arthropoda, Echinodermata and Chordata. Arthropoda, represented by Cladocera, Copepoda and Crustacean larvae, formed the largest group followed by Chordata. The distribution of phyto- and zooplankton was examined and discussed on a seasonal, annual and inter-annual basis. In terms of species, overall species composition was not affected by plant discharge. The study brings out a greater understanding of the changes experienced by biotic communities as a result of impingement, entrainment and entrapment consequent to water passage through the plant structures. The study reflects the ecological relationships that the phytoplankton and the zooplankton of the region possess with respect to intake and discharge. Further, the study has brought to light a very redeeming feature of the ecosystem to sustain its productivity and planktonic abundance. It was observed that seawater temperature, conductivity and total suspended solids did not act as limiting factors. Besides throwing much light on the little known biological aspects of desalination sites, the data provided constitute a significant addition to the knowledge base of marine living resources in an industrial zone of Gulf coastal waters.     

Methanol oxidation on Au/TiO2 catalysts

We have investigated the adsorption and reaction of methanol with Au/TiO₂ catalysts using a pulsed flow reactor, DRIFTS and TPD. The TiO₂ (P25) surface adsorbed a full monolayer of methanol, much of it in a dissociative manner, forming methoxy groups associated with the cationic sites, and hydroxyl groups at the anions. The methoxy is relatively stable until 250 °C, at which point decomposition occurs, producing mainly dimethyl ether by a bimolecular surface reaction. As the concentration of methoxy on the surface diminishes, so the mechanism reverts to a de-oxygenation pathway, producing mainly methane and water (at ~330 °C in TPD), but also with some coincident CO and hydrogen. Au catalysts were prepared by the deposition-precipitation method to give Au loadings between 0.5–3 wt %. The effect of low levels of Au on the reactivity is marked. The pathway which gives methane, which is characteristic of titania, remains, but a new feature of the reaction is the evolution of CO₂ and H₂ at lower temperature (a peak is seen in TPD at 220 °C), and the elimination of the DME-producing state. Clearly this is associated with the presence of Au and appears to be due to the production of a formate species on the surface of the Au component. This formate species is mainly involved in the reaction of methanol with the Au/TiO₂ catalysts which results in a combustion pathway being followed, with complete conversion occurring by ~130 °C.     

Potassium sorbate solutions as copper chemical mechanical planarization (CMP) based slurries

Copper depassivation and repassivation characteristics in potassium sorbate solutions, subsequent to mechanical abrading are reported. The identification of copper repassivation kinetics obtained subsequent to mechanical damage of copper protective films formed in sorbate based solutions is discussed. The repassivation rate of copper in sorbate based solutions was measured by means of a slurryjet system capable of measuring single particle impingments on microelectrodes. Copper repassivation rates measured by this slurryjet system in sulfate solutions containing 10 g L⁻¹ potassium sorbate were found to be in the range of 0.5-1.5 ms. An increase in the potassium sorbate concentration leads to a decrease in copper repassivation time at potentials ranging from 200 to 600 mV_Ag/AgCl. The impingement angle between the copper surface and a single abrasive particle has no impact on copper repassivation time nor peak current (I_max) values. XPS studies revealed that copper passivation in potassium based solution was due to the formation of a thin film which is constituted of: Cu₂O, Cu(OH)₂ and Cu(II)-sorbate, while copper(II)-sorbate is mainly present at the top levels of the passive film. It is therefore recommended that the use of potassium sorbate as a passivating component in conjunction with the addition of strong oxidizing agents in chemical mechanical planarization (CMP) slurry design should be considered.     

Kinetics of the hydroformylation of soybean oil by ligand-modified homogeneous rhodium catalysis

The kinetics and mechanism of the hydroformylation of soybean oil by homogeneous ligand-modified rhodium catalysts were investigated at 70–130°C and 4000–11,000 kPa. The effects of reaction rates on systematic variations in reaction parameters were evaluated in order to develop an industrial process to convert vegetable oils to polyaldehydes. The activation energies in the presence of triphenylphosphine (Ph₃P) (61.1±0.8 kJ/mol) (mean±SD) and triphenyl phosphite [(PhO)₃P] (77.4±5.0 kJ/mol) were determined. The catalyst was deactivated at temperatures higher than 100°C. An evaluation of the effects of the reaction parameters on initial rates yielded the rate laws for Ph₃P {rate=k [olefin][Rh(CO)₂Acac]^1.1 [Ph₃P]^−0.5 (pH₂+pCO)^1.4, where Rh(CO)₂Acac is (acetylacetonato)dicarbonylrhodium (I)} and (PhO)₃P {rate=[olefin] [Rh(CO)₂Acac]^1.2 [(PhO)₃P]^−0.8 (pH₂+pCO)^0.9 at total pressures lower than 7000 kPa, and rate =[olefin] [Rh(CO)₂Acac]^1.2 [(PhO)₃P]^−0.8(pH₂+pCO)^1.7 at total pressures higher than 7000 kPa}.     

Feeding response of Ips paraconfusus to phloem and phloem metabolites of Heterobasidion annosum-inoculated ponderosa pine,Pinus ponderosa

In studies of feeding by the bark beetle, Ips paraconfusus, two pine stilbenes (pinosylvin and pinosylvin methyl ether), ferulic acid glucoside, and enantiomers of the four most common sugars present in ponderosa pine phloem (sucrose, glucose, fructose, and raffinose) did not stimulate or reduce male feeding when assayed on wet -cellulose with or without stimulatory phloem extractives present. When allowed to feed on wet -cellulose containing sequential extracts (hexane, methanol, and water) of ponderosa pine phloem, methanol and water extractives stimulated feeding, but hexane extractives did not. Males confined in wet -cellulose containing aqueous or organic extracts of culture broths derived from phloem tissue and containing the root pathogen, Heterobasidion annosum, ingested less substrate than beetles confined to control preparations. In an assay using logs from uninoculated ponderosa pines, the mean lengths of phloem in the digestive tracts increased as time spent feeding increased. Males confined to the phloem of basal logs cut from ponderosa pines artificially inoculated with H. annosum ingested significantly less phloem than beetles in logs cut from trees that were (combined) mock-inoculated or uninoculated and did not contain the pathogen. However, individual pathogen-containing treatments were not significantly different from uninoculated controls. It was concluded that altered feeding rates are not a major factor which may explain why diseased ponderosa pines are colonized by I. paraconfusus.