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When the Debye length is on the order of or larger than the height of a nanofluidic channel containing surface charge, a unipolar solution of counterions is generated to maintain electrical neutrality. A pressure-gradient-driven flow under such conditions can be used for ion separation, which forms the basis for electrochemomechanical energy conversion. The current−potential (I−φ) characteristics of such a battery were calculated using continuum dynamics. When the bulk concentration is large and the channel does not become a unipolar solution of counterions, both the current and potential become small. On the other hand, when bulk concentration is so much smaller, the mass diffusion becomes the rate-controlling step and the potential drops rapidly in the high current density region. When the Debye length of the solution is about half of the channel height, the efficiency is maximized.
The intensity, distribution, and frequency characteristics of hydrodynamic pressures acting on dams during earthquakes are discussed. A short review of previous work on this subject is presented, with particular emphasis on evaluation of common simplifying assumptions. Including compressibility of water, an analysis is made of the pressures generated on a rigid dam with a vertical upstream face. These results are intended for gravity dams. General expressions for the complete time history of pressures during arbitrary horizontal and vertical ground motions are derived. It is concluded that the concept of an added mass, moving with the dam, to represent hydrodynamic effects is not valid for earthquake-type excitations. It is also shown that significant errors are introduced by ignoring compressibility of water. The standard design practice in considering additional water pressures on dams due to earthquakes is compared with the theoretical responses.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Controllable etching and surface passivation of InP semiconductors are desirable for removing damaged surfaces and obtaining good electronic properties. We have observed that organic acids (α-hydroxy acids: tartaric, lactic, citric, and malic), when used in conjunction with HCl to etch the (100) surface of InP results in smoother and defect-free surfaces, in comparison to etches based on inorganic acids alone. The chelating action of the organic acids aids in efficiently removing In from the surface, which leads to a very controllable etching. These chemical treatments have implications in controlling surface properties such as band bending and surface recombination velocity. © 2002 The Electrochemical Society. All rights reserved.
The first‐principles calculation of finite‐temperature phase stability and thermodynamic properties of multicomponent oxides presents a significant challenge. The time scale on which substitutional disorder occurs prevents the use of standard simulation methods, and a correct description of entropic effects requires that excitation energies can be calculated accurately on the scale of k B T . A model is presented in which substitutional disorder is parameterized with a cluster expansion. The thermodynamics of this model can be easily obtained with lattice model statistical mechanics. The only input required to the procedure is a description of bonding in the system, which is used to calculate the energy of ordered ionic configurations. This method is applied to the CaO‐MgO, Gd 2 O 3 ‐ZrO 2 , CaO‐ZrO 2 systems, and to Li x CoO 2 ( x between 0 and 1) electrodes for rechargeable lithium batteries. In almost all cases, a correct description of the charge state of the ions is essential to obtain the proper mixing behavior. Only for a highly ionic material such as CaO‐MgO does the charge state of the ions remain unvaried upon mixing. We find that approximate energy models that employ fixed charges will tend to overestimate the energy required for mixing, hence the order‐disorder transition temperature.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Trypsin immobilization onto continuous "molded" rods of porous poly(glycidyl methacrylate-co-ethylene dimethacrylate) and some applications of the conjugate have been studied. The rods polymerized within a tubular mold (chromatographic column), were treated in situ with ethylenediamine, activated with glutaraldehyde and finally modified with trypsin. The performance of the trypsin-modified rods was evaluated and compared to that of poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads, modified with the same enzyme. Overall the enzyme-modified rods performed substantially better than the corresponding beads. In particular, the performance of the molded supports as enzymatic reactors or as chromatographic media benefits greatly from the enhanced mass transfer that is characteristic of the molded rod at high flow rates. (c) 1996 John Wiley & Sons, Inc.
