1,509 research outputs found
El pragmatismo: ¿un nombre antiguo para nuevas maneras de pensar?
This article provides an introductory overview and comparison of
the pragmatism of Charles Peirce, the founder of the American
movement, with aspects of the pragmatism of disciples such as
William James, F.C.S. Schiller, and John Dewey, including
Peirce’s reactions to these latter thinkers, and some observations
on the place of pragmatism in the 21st century
Group delay in THz spectroscopy with ultra-wideband log-spiral antennae
We report on the group delay observed in continuous-wave terahertz
spectroscopy based on photomixing with phase-sensitive homodyne detection. We
discuss the different contributions of the experimental setup to the phase
difference \Delta\phi(\nu) between transmitter arm and receiver arm. A simple
model based on three contributions yields a quantitative description of the
overall behavior of \Delta\phi(\nu). Firstly, the optical path-length
difference gives rise to a term linear in frequency. Secondly, the
ultra-wideband log-spiral antennae effectively radiate and receive in a
frequency-dependent active region, which in the most simple model is an annular
area with a circumference equal to the wavelength. The corresponding term
changes by roughly 6 pi between 100 GHz and 1 THz. The third contribution stems
from the photomixer impedance. In contrast, the derivative (d\Delta\phi / d\nu)
is dominated by the contribution of periodic modulations of \Delta\phi(\nu)
caused by standing waves, e.g., in the photomixers' Si lenses. Furthermore, we
discuss the Fourier-transformed spectra, which are equivalent to the waveform
in a time-domain experiment. In the time domain, the group delay introduced by
the log-spiral antennae gives rise to strongly chirped signals, in which low
frequencies are delayed. Correcting for the contributions of antennae and
photomixers yields sharp peaks or "pulses" and thus facilitates a
time-domain-like analysis of our continuous-wave data.Comment: 7 pages, 7 figure
Evaluation of Pull Production Control Strategies Under Uncertainty: An Integrated Fuzzy Ahp-Topsis Approach
Purpose: Just-In-Time (JIT) production has continuously been considered by industrial practitioners and researchers as a leading strategy for the yet popular Lean production. Pull Production Control Policies (PPCPs) are the major enablers of JIT that locally control the level of inventory by authorizing the production in each station. Aiming to improve the PPCPs, three authorization mechanisms: Kanban, constant-work-in-process (ConWIP), and a hybrid system, are evaluated by considering uncertainty. Design/methodology/approach: Multi-Criteria Decision Making (MCDM) methods are successful in evaluating alternatives with respect to several objectives. The proposed approach of this study applies the fuzzy set theory together with an integrated Analytical Hierarchy Process (AHP) and a Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) method. Findings: The study finds that hybrid Kanban-ConWIP pull production control policies have a better performance in controlling the studied multi-layer multi-stage manufacturing and assembly system. Practical implications: To examine the approach a real case from automobile electro-mechanical part production industry is studied. The production system consists of multiple levels of manufacturing, feeding a multi-stage assembly line with stochastic processing times to satisfy the changing demand. Originality/value: This study proposes the integrated Kanban-ConWIP hybrid pull control policies and implements several alternatives on a multi-stage and multi-layer manufacturing and assembly production system. An integrated Fuzzy AHP TOPSIS method is developed to evaluate the alternatives with respect to several JIT criteriaPeer Reviewe
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