Semi-analytical proton exchange membrane fuel cell modeling

Mathematical techniques are presented which allow for analytical solutions of the catalyst layer transport and electrochemical problem in PEM fuel cells. These techniques transform the volumetric reaction terms to boundary flux terms, thereby eliminating the need for computational solving of the catalyst layer problem. The result is a semi-analytical fuel cell model—a computational model that entails analytical rather than computational catalyst layer solutions. This helps to alleviate the meshing difficulties inherent in the catalyst layers caused by large geometric aspect ratios, and hence reduce the computational requirements for fuel cell models.     

Enhanced Photocurrent Production by Photosystem I Multilayer Assemblies

The long‐term success of photosynthetic organisms has resulted in their global superabundance, which is sustained by their widespread, continual mass‐production of the integral proteins that photocatalyze the chemical processes of natural photosynthesis. Here, a fast, general method to assemble multilayer films composed of one such photocatalytic protein complex, Photosystem I (PSI), onto a variety of substrates is reported. The resulting films, akin to the stacked thylakoid structures of leaves, consist of a protein matrix that is permeable to electrochemical mediators and contain a high concentration of photoelectrochemically active redox centers. These multilayer assemblies vastly outperform previously reported monolayer films of PSI in terms of photocurrent production when incorporated into an electrochemical system, and it is shown that these photocatalytic properties increase with the film thickness. These results demonstrate how the assembly of micron‐thick coatings of PSI on non‐biological substrates yields a biohybrid ensemble that manifests the photocatalytic activity of the film’s individual protein constituents, and represent significant progress toward affordable, biologically‐inspired renewable energy conversion platforms.     

Guest Editors’ introduction to special section: Supply chain trading agent research

Predictability of prices and availability are becoming less predictable in emerging supply chain environments, as product lifecycles shorten and organizations pursue increased agility. This leads to new competitive and strategic interactions among actors across the supply chain. It also threatens to overwhelm human decision capabilities with a combinatorial explosion of possibilities. Recent advances in technical infrastructure have enabled new types of interorganizational interactions, but have not addressed the need for fundamentally new kinds of decision support systems that can help tame the complexity of this emerging environment. The papers in this special issue describe progress in semi-autonomous trading agents that are being developed to meet this need.     

Reconfigurable counter spindle module with integrated device for fast spindle alignment

An upcoming exchange of a machine tool spindle involves a downtime of several days for a cutting machine. This paper presents an innovative counter spindle module which can be replaced in significantly less time. The counter spindle module is developed in a methodical design process and is based on an effective high-precision alignment system, whose functionality and features are described in detail. Furthermore, an appropriate measuring process to identify the present deviation of a main or counter spindle is introduced. Finally, the operational capability and efficiency of the developed spindle alignment system is validated on the basis of the introduced measuring process.     

Structural aspects and conformation of linear carbon polytypes (carbynes)

The apparent discrepancy that an element with the richest chemistry of all should possess only few polymorphs was resolved recently by the increasing recognition of carbynes, chain-like compounds with sp-configuration and conjugated triple or cumulated double bonds between the carbon atoms in the chain. A simple classification approach is suggested leading to a linear relationship between the number of atoms in the chain and the c-axes lengths, the cell volumes, and the $\text{a}{}_0\text{c}{}_0$ ratio. Moreover, a new carbyne form was observed which may have originated from regraphitization of shock-formed diamond. The new carbon polymorph fits well in the gap between already known carbyne forms.     

Effect of various phenol additives on viscosity of SRC blends

Coal-derived liquids are susceptible to oxidative degradation. Two different weight ratios of SRC-I/SRC-II blends, with or without phenol derivatives, have been subjected to accelerated ageing studies. Viscosity, infrared, elemental analysis, molecular weight determination, and solvent analysis are used to examine the properties of the degradation products. On ageing, there is a large increase in the amount of toluene-insoluble material, decrease in oil components, and a relatively constant amount of asphaltenes. The oxygen content increases in the aged toluene-insoluble and asphaltene fractions, and a new absorption at ≈1700 cm^?1 (the C = 0 group) appears in these two fractions only. On the addition of phenol itself and the less hindered phenol derivatives, the original hydrogen-bonding between the acidic and basic fuctional groups in the coal liquids is apparently disrupted because the added phenol can now interact with the proton-accepting species in the liquids, thus leading to a lower viscosity. This does not mean that the unhindered phenols retard the rate of ageing. The original hydrogen-bonding in the coal-derived liquid now gives way to a new hydrogen-bonding, and ageing occurs with the latter. The more hindered phenol derivatives are not as effective as phenol in disrupting the original hydrogen-bonding in the coal-derived liquids.     

Evaluation of capital cost data: Heat exchangers

Capital cost correlations are given for heat exchangers and furnaces. Correlations available in the literature and current data are compared on a consistent basis. Forty-six graphs show the relative magnitude of the different correlations and the recommended correlation for each type of equipment is summarized in a table. Some data on the costs of installing heat exchange equipment are given.     

The coalescence of H2S and CO2 bubbles in water

Coalescence times are reported for bubbles of H₂S and CO₂ formed on adjacent nozzles in water. With CO₂, times were small (1–3 ms) at pressures below 2 MPa, and rose to 20 ms at 3.4 MPa. With H₂S, the logarithm of the coalescence time was proportional to pressure, and coalescence times reached 100 ms at 1.7 MPa. Film stretching rates were calculated assuming that the film surfaces were slightly immobile. By using a form of Vrij's theory for the inherent breaking time of films of constant thickness, the effective number of immobile layers could be calculated. Since these were in the range 10^?2 to 10^?3, only a small amount of “stiffness” in the film surface is enough to cause large changes in coalescence time.     

Cholesterol transport and uptake in miniature swine fed vegetable and animal fats and proteis. 1. Plasma lipoproteins and LDL clearance

In a 2×2 factorial arrangement, miniature pigs were fed four diets containing vegetable protein/fat (soybean) and animal protein (egg white)/fat (beef tallow) to demonstrate the effects of protein and fat source on total plasma cholesterol, lipoprotein distribution, low density lipoprotein (LDL) composition, and plasma clearance of LDL-cholesterol and protein. Beef tallow consumption resulted in greater plasma cholesterol concentration, decreased LDL-cholesterol concentration, and a lower LDL-cholesterol to LDL-protein ratio than did consumption of soybean oil. High density lipoprotein (HDL)-cholesterol concentration was increased by beef tallow consumption. Cholesterol percentage by weight in LDL was significantly greater in pigs consuming soybean oil than those consuming beef tallow. Percentages by weight of protein, triglyceride and phospholipid in LDL were not significantly different in any group. Dietary protein source had no significant effect on total plasma cholesterol concentration, lipoprotein concentration or LDL composition. Egg white consumption decreased fractional catabolic rate and irreversible loss of LDL-cholesterol and LDL-protein when compared with consumption of soy protein. Dietary fat source had no consistent effect on LDL clearance from plasma. Dietary fat and protein seemed to influence lipoprotein metabolism by different mechanisms. Fat source altered lipoprotein concentration and LDL composition, whereas protein source affected the removal rate of LDL from plasma. Data taken from a dissertation submitted to Iowa State University by L. S. Walsh Hentges as partial fulfillment of the requirements for the Ph.D. degree. A preliminary paper, was presented at the meeting of the American Oil Chemists' Society in Dallas, Texas, May, 1984.