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    Preferential concentration of inertial sub-kolmogorov particles. The roles of mass loading of particles, Stokes and Reynolds numbers

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    Turbulent flows laden with inertial particles present multiple open questions and are a subject of great interest in current research. Due to their higher density compared to the carrier fluid, inertial particles tend to form high concentration regions, i.e. clusters, and low concentration regions, i.e. voids, due to the interaction with the turbulence. In this work, we present an experimental investigation of the clustering phenomenon of heavy sub-Kolmogorov particles in homogeneous isotropic turbulent flows. Three control parameters have been varied over significant ranges: Reλ[170450]Re_{\lambda} \in [170 - 450], St[0.15]St\in [0.1 - 5] and volume fraction ϕv[2×1062×105]\phi_v\in [2\times 10^{-6} - 2\times 10^{-5}]. The scaling of clustering characteristics, such as the distribution of Vorono\"i areas and the dimensions of cluster and void regions, with the three parameters are discussed. In particular, for the polydispersed size distributions considered here, clustering is found to be enhanced strongly (quasi-linearly) by ReλRe_{\lambda} and noticeably (with a square-root dependency) with ϕv\phi_v, while the cluster and void sizes, scaled with the Kolmogorov lengthscale η\eta, are driven primarily by ReλRe_{\lambda}. Cluster length Ac\sqrt{\langle A_c \rangle} scales up to 100η\approx 100 {\eta}, measured at the highest ReλRe_{\lambda}, while void length Av\sqrt{\langle A_v \rangle} scaled also with η\eta is typically two times larger (200η\approx 200 {\eta}). The lack of sensitivity of the above characteristics to the Stokes number lends support to the "sweep-stick" particle accumulation scenario. The non-negligible influence of the volume fraction, however, is not considered by that model and can be connected with collective effects

    The Global Spread of Stock Exchange, 1980-1998

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    Nations opened local stock exchanges at a rapid pace during the late 1980s and 1990s, creating a channel for investment capital from wealthy industrial nations to "emerging markets" as well as a mechanism for institutional change in local economies. This study examines the local and global processes by which exchanges spread, examining all nations "at risk" during the 1980s and 1990s. We find that local factors influencing the creation of stock exchanges included the size of the economy (overall and relative to population size); the legacy of colonialism; and a recent transition to multi-party democracy. Global factors associated with creating exchanges included levels of prior investment by multinationals; IMF "structural adjustment" aid; centrality in trade flows; and regional "contagion." In contrast to prior work in financial economics, we find no evidence for the influence of legal tradition, and contrary to the implications of dependency theory, we find no sign that foreign capital penetration affects the creation of exchanges. We also find no consistent evidence for the influence of stock exchanges on inequality or human development at the national level, above and beyond their effect on economic and population growth. The results indicate that globalization is usefully construed as a process analogous to institutional diffusion at the organization level.http://deepblue.lib.umich.edu/bitstream/2027.42/39725/3/wp341.pd

    Rent Appropriation in Strategic Alliances: A Study of Technical Alliances in Pharmaceutical Industry

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    Many existing alliance studies have investigated how embedded relations create superior value for organizations. The role of network structure in rent appropriation or pie splitting, however, has been underexplored. We propose that favorable locations in interorganizational networks provide firms with superior opportunities for appropriating more economic benefits from alliances than their partners do. Specifically, we argue that partners’ asymmetric network positions will lead to unequal brokerage positions that promote disparate levels of information gathering, monitoring, and bargaining power, which lead to differing capacities to appropriate value. This in turn results in variations in market performance. We also propose this brokerage position exacerbates existing inequalities such as commercial capital; thus, available firm resources will moderate such network effects. Evidence is presented in the form of market response to technology alliance announcements from a set of pharmaceutical firms. In general, we find that firms within central network positions and those spanning structural holes have higher returns than their partners. In addition, we show that this relationship is contingent upon available firm resources
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