8,645 research outputs found
The Faustian Grip of Academic Publishing
The journal acquisition budget of libraries is not increasing at the same rate as subscription rates creating the serials' crisis. Many solutions have been proposed including the freely available electronic journal. However, all the solutions suffer the same Faustian Grip - namely that the actors in the academic publishing game have little or no incentive to stop publishing in the current journals. We examine those incentives concluding that even with a better more efficient technology, the actors will not change from the current academic publishing institution, and the serials' crisis will remain.serials crisis journal pricing academic publishing
Weak Energy: Form and Function
The equation of motion for a time-independent weak value of a quantum
mechanical observable contains a complex valued energy factor - the weak energy
of evolution. This quantity is defined by the dynamics of the pre-selected and
post-selected states which specify the observable's weak value. It is shown
that this energy: (i) is manifested as dynamical and geometric phases that
govern the evolution of the weak value during the measurement process; (ii)
satisfies the Euler-Lagrange equations when expressed in terms of Pancharatnam
(P) phase and Fubini-Study (FS) metric distance; (iii) provides for a PFS
stationary action principle for quantum state evolution; (iv) time translates
correlation amplitudes; (v) generalizes the temporal persistence of state
normalization; and (vi) obeys a time-energy uncertainty relation. A similar
complex valued quantity - the pointed weak energy of an evolving state - is
also defined and several of its properties in PFS-coordinates are discussed. It
is shown that the imaginary part of the pointed weak energy governs the state's
survival probability and its real part is - to within a sign - the
Mukunda-Simon geometric phase for arbitrary evolutions or the Aharonov-Anandan
(AA) phase for cyclic evolutions. Pointed weak energy gauge transformations and
the PFS 1-form are discussed and the relationship between the PFS 1-form and
the AA connection 1-form is established.Comment: To appear in "Quantum Theory: A Two-Time Success Story"; Yakir
Aharonov Festschrif
Emergence of atom-light-mirror entanglement inside an optical cavity
We propose a scheme for the realization of a hybrid, strongly
quantum-correlated system formed of an atomic ensemble surrounded by a
high-finesse optical cavity with a vibrating mirror. We show that the steady
state of the system shows tripartite and bipartite continuous variable
entanglement in experimentally accessible parameter regimes, which is robust
against temperature
Welding high-strength aluminum alloys
Handbook has been published which integrates results of 19 research programs involving welding of high-strength aluminum alloys. Book introduces metallurgy and properties of aluminum alloys by discussing commercial alloys and heat treatments. Several current welding processes are reviewed such as gas tungsten-arc welding and gas metal-arc welding
Some applications of the second method of Liapunov to dynamical systems described by partial differential equations
Efficient optimisation of structures using tabu search
This paper presents a novel approach to the optimisation of structures using
a Tabu search (TS) method. TS is a metaheuristic which is used to guide local
search methods towards a globally optimal solution by using flexible memory
cycles of differing time spans. Results are presented for the well established
ten bar truss problem and compared to results published in the literature. In
the first example a truss is optimised to minimise mass and the results
compared to results obtained using an alternative TS implementation. In the
second example, the problem has multiple objectives that are compounded into a
single objective function value using game theory. In general the results
demonstrate that the TS method is capable of solving structural optimisation
problems at least as efficiently as other numerical optimisation approaches
Insight into High-quality Aerodynamic Design Spaces through Multi-objective Optimization
An approach to support the computational aerodynamic design process is presented
and demonstrated through the application of a novel multi-objective variant of
the Tabu Search optimization algorithm for continuous problems to the
aerodynamic design optimization of turbomachinery blades. The aim is to improve
the performance of a specific stage and ultimately of the whole engine. The
integrated system developed for this purpose is described. This combines the
optimizer with an existing geometry parameterization scheme and a well-
established CFD package. The system’s performance is illustrated through case
studies – one two-dimensional, one three-dimensional – in which flow
characteristics important to the overall performance of turbomachinery blades
are optimized. By showing the designer the trade-off surfaces between the
competing objectives, this approach provides considerable insight into the
design space under consideration and presents the designer with a range of
different Pareto-optimal designs for further consideration. Special emphasis is
given to the dimensionality in objective function space of the optimization
problem, which seeks designs that perform well for a range of flow performance
metrics. The resulting compressor blades achieve their high performance by
exploiting complicated physical mechanisms successfully identified through the
design process. The system can readily be run on parallel computers,
substantially reducing wall-clock run times – a significant benefit when
tackling computationally demanding design problems. Overall optimal performance
is offered by compromise designs on the Pareto trade-off surface revealed
through a true multi-objective design optimization test case. Bearing in mind
the continuing rapid advances in computing power and the benefits discussed,
this approach brings the adoption of such techniques in real-world engineering
design practice a ste
Skylab materials processing facility experiment developer's report
The development of the Skylab M512 Materials Processing Facility is traced from the design of a portable, self-contained electron beam welding system for terrestrial applications to the highly complex experiment system ultimately developed for three Skylab missions. The M512 experiment facility was designed to support six in-space experiments intended to explore the advantages of manufacturing materials in the near-zero-gravity environment of Earth orbit. Detailed descriptions of the M512 facility and related experiment hardware are provided, with discussions of hardware verification and man-machine interfaces included. An analysis of the operation of the facility and experiments during the three Skylab missions is presented, including discussions of the hardware performance, anomalies, and data returned to earth
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