We present an all-oxide solar cell fabricated from vertically oriented zinc oxide nanowires and cuprous oxide nanoparticles. Our solar cell consists of vertically oriented n-type zinc oxide nanowires, surrounded by a film constructed from p-type cuprous oxide nanoparticles. Our solution-based synthesis of inexpensive and environmentally benign oxide materials in a solar cell would allow for the facile production of large-scale photovoltaic devices. We found that the solar cell performance is enhanced with the addition of an intermediate oxide insulating layer between the nanowires and the nanoparticles. This observation of the important dependence of the shunt resistance on the photovoltaic performance is widely applicable to any nanowire solar cell constructed with the nanowire array in direct contact with one electrode.
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.
: The recent development of metallic alloy systems which can be processed with an amorphous structure over large dimensions, specifically to form metallic glasses at low cooling rates (tilde 10 K/s), has permitted novel measurements of important mechanical properties. These include, fatigue crack growth and fracture toughness behavior, representing the conditions governing the subcritical and critical propagation of cracks. In the present study, bulk plates of a Zr41.2 Ti13.8 Cu12.5 Ni10 Be22.5 alloy, machined into 7 mm thick, 33 mm wide compact tension specimens and fatigue precracked following standard procedures, revealed fracture toughness in the fully amorphous structure of KIc tilde 55 MPa(square root m), i.e., comparable with that of a high strength steel or aluminum alloy. However, annealing to induce partial and full crystallization was found to result in a drastic reduction in fracture toughness to 1 MPa(square root m), i.e., comparable with silica glass. Under cyclic loading, whereas crack propagation behavior of the bulk amorphous metal was similar to that observed in traditional steel and aluminum alloys, the stress-life (S-N) properties of were markedly different. As in more traditional crystalline metallic alloys, the crack propagation mechanism in the metallic glass was associated with alternating blunting and resharpening of the crack tip as evidenced by striations on fatigue fracture surfaces. Alternatively, during S-N tests flaws apparently initiated quite easily due to the lack of microstructural barriers which would normally provide local crack arrest points, thereby giving rise to poor S-N properties.
This paper presents a comparative analysis of two resource reservation protocols, ST-II proposed by Topolcic (1990) and resource reservation protocol (RSVP) proposed by Zhang, Braden, Estrin, Herzog and Jamin (1994) in support of an integrated services packet network (ISPN). The authors use simulations to examine the network-wide resource requirements for each protocol to support a number of application communication styles, across a range of group sizes and membership distributions. They also present a comparison of the protocol features to accommodate network and group membership dynamics.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Stomata are major conduits for the diffusion of many trace gas species between leaves and the atmosphere. The role of the stomata on controlling gas exchange between the terrestrial biosphere and the atmosphere at the landscape, meso- and global-scales has only recently been recognized. Further advances in modelling large-scale trace gas exchange will depend on our ability to understand and model stomatal mechanics at the scale of the pertinent sub-unit, which is typically that of the canopy. This paper describes two approaches for estimating canopy stomatal conductance. One approach is based on 'bottom-up' scaling. This approach computes canopy stomatal conductance by integrating detailed leaf-level and environmentally-driven, physiological processes with the use of a detailed canopy micrometeorology model. The other approach is based on 'top-down' scaling. It interprets the integrated canopy stomatal conductance from measured fluxes of trace gas exchange. Frameworks for extending these scaling approaches to non-idea conditions are given. 96 refs., 5 figs.
The authors prove three key inequalities stated in the paper by L.O. Chua, M. Komouro, and T. Matsumoto (see ibid., vol. CAS-33, p. 1072-1118, 1986) by giving verifiable error bounds to the quantities involved in the inequalities with an assistance of a computer. This provides another rigorous proof that the so-called double scroll circuit is chaotic in the sense of Shilnikov. Since a computer is used, everything must be transparent; there should be no black box. To provide a rigorous computer-base free from roundoff errors, it is shown that all the computations are reduced to four logic operations: AND, OR, NOT, and XOR. Based on this, the computer performs internal analysis, which is a method of computing intervals containing the true values. This is important for two reasons: first, the double scroll circuit then becomes, the first real, physical system in which chaos is (i) observed in the laboratory, (ii) confirmed by computer simulation, and (iii) proven mathematically. Second, the author's approach can easily be modified to apply to other problems, providing a powerful tool for a large class of problems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Damage and cyclic fatigue failure under alternating loading in transformation-toughened zirconia ceramics is reviewed and compared to corresponding behavior under quasi-static loading (static fatigue). Current understanding of the role of transformation toughening in influencing cyclic fatigue-crack propagation behavior is examined based on studies which altered the extent of the tetragonal-to-monoclinic phase transformation in MG-PSZ through subeutectoid aging. These studies suggest that near-tip computations of the crack-driving force (in terms of the local stress intensity) can be used to predict crack-growth behavior under constant amplitude and variable-amplitude (spectrum) loading, using spatially resolved Raman spectroscopy to measure the extent of the transformation zones. In addition, results are reviewed which rationalize distinctions between the crack-growth behavior of preexisting, ``long`` (> 2 mm), through-thickness cracks and naturally-occurring, ``small`` (1 to 100 {mu}m), surface cracks in terms of variations in crack-tip shielding with crack size. In the present study, the effect of grain size variations on crack-growth behavior under both monotonic (R-curve) and cyclic fatigue loading are examined. Such observations are used to speculate on the mechanisms associated with cyclic crack advance, involving such processes as alternating shear via transformation-band formation, cyclic modification of the degree of transformation toughening, and uncracked-ligament (or grain) bridging.
Patterns of referral among internists in private practice are examined in terms of the rewards and costs perceived by physicians occupying different levels of professional status in the medical community. Referral patterns are highly related to professional status networks. High status internists showed the most cohesive patterns of referral and low status the least. Findings pertaining to the institutionalization of reciprocity, as well as the influence of social friendships, distance between offices, and hospital appointments are discussed. Policy implications and areas for further research are suggested.
The Local Activity Principle and the Emergence of Complexity Local Activity and Edge of Chaos in Computer Visualization The Local Activity Principle and the Expansion of the Universe The Local Activity Principle and the Dynamics of Matter The Local Activity Principle and the Evolution of Life The Local Activity Principle and the Co-evolution of Technology The Local Activity Principle and Innovation in the Economy and Society The Message of the Local Activity Principle.
