A System for Building Intelligent Agents that Learn to Retrieve and Extract Information

We present a system for rapidly and easily building instructable and self-adaptive software agents that retrieve and extract information. Our Wisconsin Adaptive Web Assistant (WAWA) constructs intelligent agents by accepting user preferences in the form of instructions. These user-provided instructions are compiled into neural networks that are responsible for the adaptive capabilities of an intelligent agent. The agent’s neural networks are modified via user-provided and system-constructed training examples. Users can create training examples by rating Web pages (or documents), but more importantly WAWA’s agents uses techniques from reinforcement learning to internally create their own examples. Users can also provide additional instruction throughout the life of an agent. Our experimental evaluations on a ‘home-page finder’ agent and a ‘seminar-announcement extractor’ agent illustrate the value of using instructable and adaptive agents for retrieving and extracting information.     

Polyimide–polyurea copolymer coating with outstanding corrosion inhibition properties

A novel class of copolymers containing polyimide and polyurea blocks with unique physical properties and capable of providing effective protection to aluminum alloy 2024‐T3 substrate against corrosion has been prepared. The structure and properties of polyurea‐b‐polyimide (PUI) copolymers were controlled by varying the co‐monomer concentration. The PUI block copolymer can reorganize into a supra‐molecular structure by forming intra‐ and inter‐hydrogen bonding interactions between adjacent copolymer chains, resulting in a dense and compact structure capable of protecting the imide ring from hydrolysis when exposed to a corrosive environment. Apart from minimized surface hydrolysis, the establishment of compacted morphology also leads to a drastically improved barrier property and reduced diffusivity. The corrosion rate and polarization resistances of PUI‐coated aluminum alloys were measured by using direct current polarization technique. Increasing polyurea concentration resulted in a remarkable decrease in diffussivity and surface energy, consistent with the measured remarkable increase in the coatings durability and corrosion performance. Corrosion inhibition tests were carried out for more than 30 weeks in a saturated NaCl solution containing 3.5 wt % of salt. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45861.     

Electrodeposition of BTDA-ODA-PDA polyamic acid coatings on carbon fibers from nonaqueous emulsions

Electrochemical deposition of polyamic acid copolymer of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 4,4′-oxydianiline (ODA) and 1.3-phenylenediamine (PDA) was performed from a nonaqueous emulsion on carbon fibers. The electrodeposited PAA was subsequently dried. The yield and quality of deposited polyamic acid are strongly dependent upon a number of parameters that are related to the formulation and characteristics of polyamic acid emulsion. These parameters include solvent/precipitant ratio, concentration of surfactant, and solids content. The deposition yield of PAA was related to the applied current density, deposition time, and the charge passed, and was found to obey Faraday's laws of electrolysis. The coulombic efficiency was calculated.     

Spatio‐temporal variations in the trophic status of Lake Naivasha,Kenya

The spatio‐temporal dynamics of the trophic state of a lake are crucial in defining its water quality, as well as biodiversity. Accordingly, this study focused on the spatio‐temporal variations of the trophic state, and the possible causes of the heterogeneous turbidity in Lake Naivasha, Kenya. The trophic state of the lake oscillated between a eutrophic and hypereutrophic condition, being found to be more eutrophic than reported in previous studies, indicating a progressive deterioration of its water quality. Inferences from the graphical representation of the deviations of total phosphorus and Secchi depth from the chlorophyll‐a trophic state indices revealed that the lake is predominantly phosphorus limited. Furthermore, the turbidity in the northern part of the lake is dominated by suspended sediment and dissolved coloured material. Discriminant analysis resulted in identification of three distinct trophic state regions in Lake Naivasha, namely the northern region, the mid and southern part and the more or less isolated Crescent Lake. The results of this study provide a good basis for further investigation of the current loading magnitude of both nutrients and sediments, in order to facilitate sustainable management to ensure community integrity and ecosystem functions of the lake.     

Two-phase flow behaviour and performance of polymer electrolyte membrane electrolysers: Electrochemical and optical characterisation

Understanding gas evolution and two-phase flow behaviour are critical for performance optimization of polymer electrolyte membrane water electrolysers (PEMWEs), particularly at high current densities. This study investigates the gas-bubble dynamics and two-phase flow behaviour in the anode flow-field of a PEMWE under different operating conditions using high-speed optical imaging and relates the results to the electrochemical performance. Two types of anode flow-field designs were investigated, the single serpentine flow-field (SSFF) and parallel flow-field (PFF). The results show that the PFF design yielded a higher cell performance than the SSFF design at identical operating conditions. Optical visualization shows a strong relationship between the flow path length and the length of gas slugs produced, which in turn influences the flow regime of operation. Longer flow path length in the SSFF results in annular flow regime at a high current density which degrades cell performance. The annular flow regime was absent in the PFF design. It was found the effect of flow rate on performance depends strongly on operating temperature in both flow patterns. Results of this study indicate that long channel length promotes gas accumulation and channel-blocking which degrades performance in PEMWEs.     

Effect of isothermal aging on post-imidization and glass transition temperature of LaRC-IA polyimide resin

The isothermal aging of partilly imidized NASA Langley Research Center, LaRC-IA polymide resin containing 70 wt% N-methyl pyrrolidone, NMP was performed in a vacuum oven at 65, 95, 135, 165 and 200°C for 0.5, 1.0, 1.5 and 2 h. The weight loss and chemical changes that occurred during aging was determined gravimetrically and by FTIR spectroscopy, respectively. The imide absorption peak at 1778 cm⁻¹, increased in intensity as the aging temperature was increased from 65 to 200°C. The expulsion of NMP (70 wt%) was completed after ∼2.5 h of aging at 135°C. Additional weight loss ≤4 wt%, after the expulsion of NMP, was attributed to post-imidization. The imide carbonyl peak absorption at 1721 and 1778 cm⁻¹, respectively, were broadened after aging at 200°C. The broadening of the imide absorption peaks was marked by the disappearance of the amide peak near 1660 cm⁻¹ and is attributable to post-imidization of the partially imidized polyamic-acid. Dissolution of the polyimide aged at T ≥ 165°C in dimethyl formamide, DMF, was unsuccessful even after long times of stirring (∼12 h) at elevated temperature (T ∼ 85°C). The DSC thermogram for the LaRC-IA resin showed a series of broad endothermic peaks between 150–180°C and narrow endothermic peaks at 210°C. The low temperature endotherm disappeared after aging at T ≥ 135°C for t ≥ 1 h. The high temperature endotherm decreased with increased aging temperature and time. The glass transition temperature of the polyimide increased with increased aging temperature and time.     

Grease material properties from first principles thermodynamics

Thermodynamics has historically been used to derive characteristic material properties. In this study, fundamental thermodynamics is applied to grease. First-principle formulations of existing material properties—heat capacity and storage modulus—and new properties—thermal strain and stress coefficients, chemical resistance and thermo-chemical decay coefficient—are derived, some of which are experimentally determined. A new group of Maxwell relations is introduced by replacing the classical compression work $\mathit{PdV}$ with the grease shearing work $\mathit{\text{Vτdγ}}$. The physical interpretations and implications of these properties on grease behaviour and performance are presented. Experimental measurements of the derived properties are performed in accordance with the theoretical formulations. Six different grease types are studied. Obtained results are shown to conform with anticipated, observed and established grease behaviours. The proposed properties can be used in grease performance and degradation analyses, as well as grease selection for lubrication applications.