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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.
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.
Research Summary The growth of China and President Xi's policies have transformed the global economy in ways that global strategy and international business (IB) scholars have yet to reflect fully in their research. The global economy is increasingly bifurcated between a China‐centered authoritarian system and a market‐oriented democratic system, generating complications and perils largely unknown since the end of the Cold War. The global business environment now bears faint resemblance to existing models in IB. To properly analyze the new reality, global strategy and IB scholars need to adopt a wider‐aperture, systems‐theoretic view that will require the cross‐fertilization of ideas and collaboration with other disciplines such as international political economy. This engagement will allow the development of more broadly based frameworks, theories, and models that can assist decision makers in the private and public sectors. Managerial Summary Strategic rivalry between China and the West requires managers to face a new reckoning. China remains the world's factory, but it has a tenuous relationship to even‐handed rules of law, both domestically and internationally. China leverages access to its market and has aligned with other autocratic countries to reshape the world order. Many firms have straddled the divide and tried to play by two sets of rules. This is not viable longer term. The strategic decisions of Western firms, particularly those involved with advanced and, especially, dual‐use technologies, are consequential to the future of democracy. A systemic view of the long‐term health of the enterprise may reveal the need to choose. Choosing democracy means, at minimum, guarding intellectual property, enhancing organizational capabilities, coordinating with peers, and protecting national security.
The topological insulator is an electronic phase stabilized by spin-orbit coupling that supports propagating edge states and is not adiabatically connected to the ordinary insulator. In several ways it is a spin-orbit-induced analogue in time-reversal-invariant systems of the integer quantum Hall effect (IQHE). This paper studies the topological insulator phase in disordered two-dimensional systems, using a model graphene Hamiltonian introduced by Kane and Mele as an example. The nonperturbative definition of a topological insulator given here is distinct from previous efforts in that it involves boundary phase twists that couple only to charge, does not refer to edge states, and can be measured by pumping cycles of ordinary charge. In this definition, the phase of a Slater determinant of electronic states is determined by a Chern parity analogous to Chern number in the IQHE case. Numerically we find, in agreement with recent network model studies, that the direct transition between ordinary and topological insulators that occurs in band structures is a consequence of the perfect crystalline lattice. Generically these two phases are separated by a metallic phase, which is allowed in two dimensions when spin-orbit coupling is present. The same approach can be used to study three-dimensional topological insulators.
Theoretical efficiency limits are useful primarily because they provide a means for selecting which technologies to pursue, and they are a driving force for further progress. Yet implicit in such a process is the assumption that the upper limit provides a realistic estimate of potential performance. Real systems will never be perfect, but small deviations in material quality or optical design should yield only small deviations in performance. Shockley-Queisser efficiencies are not robust to small deviations. Although they provide a simple calculational tool, they obscure important internal dynamics. We examine these dynamics, resulting in a surprising conclusion: instead of considering external emission as a loss mechanism, it should actually be designed for. A solar cell must have almost perfect photon extraction, or it will fall far short of the Shockley-Queisser efficiency limit.
By adding a linear resistor R/sub 0/ in Chua's circuit, an immensely richer bifurcation landscape can be obtained, including an endowment of more than 20 new distinct strange attractors which were suppressed when R/sub 0/ to 0. The author interprets this augmented circuit as a global unfolding of Chua's circuit because its basic mechanism is similar to the local unfolding theory in nonlinear mathematics. This augmented Chua's circuit, which has only seven parameters, is canonical in the sense that it is capable of duplicating all qualitative behaviors of a 21-parameter family C of ordinary differential equations in R/sup 3/. Explicit formulas are given for calculating the seven circuit parameters of the augmented Chua's circuit so that it is topologically conjugate to any member of this 21-parameter family of third-order piecewise-linear circuits; namely, the Chua's circuit family. A gallery of selected strange attractors from this canonical circuit is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
This paper discusses congestion control from a game-theoretic perspective. There are two basic premises: 1) Users are assumed to be independent and selfish. 2) Central administrative control is exercised only at the network switches. The operating points resulting from selfish user behavior depend crucially on the service disciplines implemented in network switches. This effect is investigated in a simple model consisting of a single exponential server shared by many Poisson sources. We discuss the extent to which one can guarantee, through the choice of switch service disciplines, that these selfish operating points will be efficient and fair. We also discuss to what extent the choice of switch service disciplines can ensure that these selfish operating points are unique and are easily and rapidly accessible by simple self optimization techniques. We show that no service discipline can guarantee optimal efficiency. As for the other properties, we show that the traditional FIFO service discipline guarantees none of these properties, but that a service discipline called fair share guarantees all of them. While the treatment utilizes game-theoretic concepts, no previous knowledge of game theory is assumed.
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.
We argue that surface segregation can be substantially modified by the presence of adsorbates and present a first-principles method that allows us to equilibrate segregation and adsorption simultaneously on surfaces with fixed topology. The method is based on a cluster expansion theory to write the state of the system in terms of adsorbate and surface layer occupation variables. This model can be parametrized with density functional theory calculations and equilibrated at finite temperature with Monte Carlo simulation. The method is applied to surface ordering and segregation at a (111) surface of ${\mathrm{Pt}}_{(1\ensuremath{-}x)}{\mathrm{Ru}}_{x}$ alloys in the presence of adsorbing oxygen. While Pt segregates under vacuum conditions, the strong binding between oxygen and Ru couples the segregation energy of the Ru to the oxygen chemical potential. As a result, we find that variations in oxygen chemical potential can dramatically alter the segregation and surface ordering tendency of dilute Ru in Pt.
