The Relative Occupational Success of Blacks and Whites

macroeconomics, occupational success

Knowledge Resources, Exploration, and Exploitation: A New Perspective on the Interplay Between Innovation and Application

Knowledge resources are the fundamental ingredients used in exploration and exploitation and an overlooked source of distinction and tension between these two processes. In this paper we use a strategic lens to differentiate evidence-based knowledge resources from tinkerable knowledge resources. This conceptualization provides the basis for a bridge between the literature on the resource-based view of the firm and research into exploration and exploitation. We suggest that an examination of knowledge resources offers a new perspective for understanding exploration and exploitation, and suggests new opportunities for achieving organizational ambidexterity. A proposed model indicates the application consequences of match and mismatch across knowledge resources and knowledge flow activities in terms of exploration and exploitation. An agenda for future research is proposed along with steps that managers can take to develop exploration and exploitation capabilities in their firms by managing their knowledge resources more precisely and effectively.knowledge resources, exploration, exploitation, knowledge management

Planetary nebulae after common-envelope phases initiated by low-mass red giants

It is likely that at least some planetary nebulae are composed of matter which was ejected from a binary star system during common-envelope (CE) evolution. For these planetary nebulae the ionizing component is the hot and luminous remnant of a giant which had its envelope ejected by a companion in the process of spiralling-in to its current short-period orbit. A large fraction of CE phases which end with ejection of the envelope are thought to be initiated by low-mass red giants, giants with inert, degenerate helium cores. We discuss the possible end-of-CE structures of such stars and their subsequent evolution to investigate for which structures planetary nebulae are formed. We assume that a planetary nebula forms if the remnant reaches an effective temperature greater than 30 kK within 10^4 yr of ejecting its envelope. We assume that the composition profile is unchanged during the CE phase so that possible remnant structures are parametrized by the end-of-CE core mass, envelope mass and entropy profile. We find that planetary nebulae are expected in post-CE systems with core masses greater than about 0.3 solar masses if remnants end the CE phase in thermal equilibrium. We show that whether the remnant undergoes a pre-white dwarf plateau phase depends on the prescribed end-of-CE envelope mass. Thus, observing a young post-CE system would constrain the end-of CE envelope mass and post-CE evolution.Comment: Published in MNRAS. 12 pages, 12 figures. Minor changes to match published versio

Investigation of advanced counterrotation blade configuration concepts for high speed turboprop systems, task 1: Ducted propfan analysis

The time-dependent three-dimensional Euler equations of gas dynamics were solved numerically to study the steady compressible transonic flow about ducted propfan propulsion systems. Aerodynamic calculations were based on a four-stage Runge-Kutta time-marching finite volume solution technique with added numerical dissipation. An implicit residual smoothing operator was used to aid convergence. Two calculation grids were employed in this study. The first grid utilized an H-type mesh network with a branch cut opening to represent the axisymmetric cowl. The second grid utilized a multiple-block mesh system with a C-type grid about the cowl. The individual blocks were numerically coupled in the Euler solver. Grid systems were generated by a combined algebraic/elliptic algortihm developed specifically for ducted propfans. Numerical calculations were initially performed for unducted propfans to verify the accuracy of the three-dimensional Euler formulation. The Euler analyses were then applied for the calculation of ducted propfan flows, and predicted results were compared with experimental data for two cases. The three-dimensional Euler analyses displayed exceptional accuracy, although certain parameters were observed to be very sensitive to geometric deflections. Both solution schemes were found to be very robust and demonstrated nearly equal efficiency and accuracy, although it was observed that the multi-block C-grid formulation provided somewhat better resolution of the cowl leading edge region

Silent Commands? Frodo and Gollum at the Cracks of Doom

Analyzes the key scene at the Cracks of Doom, which the reader sees through Sam’s viewpoint, for hints as to the powers of the bearer of the Ring and his ability to command others. Considers similar scenes from the Bible, Beowulf, and Chanson de Roland. Concludes that Frodo issued Gollum a “silent command” to throw himself into the pit with the Ring