5,981 research outputs found

    Problems with Using Evolutionary Theory in Philosophy

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    Does science move toward truths? Are present scientific theories (approximately) true? Should we invoke truths to explain the success of science? Do our cognitive faculties track truths? Some philosophers say yes, while others say no, to these questions. Interestingly, both groups use the same scientific theory, viz., evolutionary theory, to defend their positions. I argue that it begs the question for the former group to do so because their positive answers imply that evolutionary theory is warranted, whereas it is self-defeating for the latter group to do so because their negative answers imply that evolutionary theory is unwarranted

    Total ownership cost reduction case study : AEGIS radar phase shifters

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    MBA Professional ReportThe goal of this research is to provide a case study that captures the production and design processes and program management solutions used to reduce total ownership costs of AEGIS Radar Phase Shifters. Specifically, it will focus on the design and redesign of the SPY-1 radar phase shifter; a redesign that dramatically improved performance without increasing Average Procurement Unit Costs (APUC). The researchers will analyze various process-improvement projects (PIP) used to reduce touch-labor and improve production process yield (percentage of manufactured items that are defect-free) of SPY-1B/D phase shifters, and will review programs that improved phase shifter production either directly or indirectly, i.e., consolidated purchasing, lean and six sigma, productivity improvement projects, etc. This case study was conducted with the sponsorship and assistance of the Acquisition Research Program, Graduate School of Business & Public Policy, Naval Postgraduate School, Monterey, CA.http://archive.org/details/totalownershipco1094534231Lieutenant Commander, United States NavyCaptain, United States Air ForceApproved for public release; distribution is unlimited

    Charge collective modes in an incommensurately modulated cuprate

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    We report the first measurement of collective charge modes of insulating Sr14Cu24O41 using inelastic resonant x-ray scattering over the complete Brillouin zone. Our results show that the intense excitation modes at the charge gap edge predominantly originate from the ladder-containing planar substructures. The observed ladder modes (E vs. Q) are found to be dispersive for momentum transfers along the "legs" but nearly localized along the "rungs". Dispersion and peakwidth characteristics are similar to the charge spectrum of 1D Mott insulators, and we show that our results can be understood in the strong coupling limit (U >> t_{ladder}> t_{chain}). The observed behavior is in marked contrast to the charge spectrum seen in most two dimensional cuprates. Quite generally, our results also show that momentum-tunability of inelastic scattering can be used to resolve mode contributions in multi-component incommensurate systems.Comment: 4+ pages, 5 figure

    Quasiparticle coherence and the nature of the metal-insulator phase transition in Nax_xCoO2_2

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    Layered cobaltates embody novel realizations of correlated quantum matter on a spin-1/2 triangular lattice. We report a high-resolution systematic photoemission study of the insulating cobaltates (Na1/2CoO2 and K1/2CoO2). Observation of single-particle gap opening and band-folding provides direct evidence of anisotropic particle-hole instability on the Fermi surface due to its unique topology. Kinematic overlap of the measured Fermi surface is observed with the 3\sqrt{3}x3\sqrt{3} cobalt charge-order Brillouin zone near x=1/3 but not at x=1/2 where insulating transition is actually observed. Unlike conventional density-waves, charge-stripes or band insulators, the on-set of the gap depends on the quasiparticle's quantum coherence which is found to occur well below the disorder-order symmetry breaking temperature of the crystal (the first known example of its kind).Comment: 4+ pages, 5 figure
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