Modal Scope Research Articles

Quantification of Blade Vibration Amplitude in Turbomachinery

Experimental monitoring of blade vibration in turbomachinery is typically based on blade-mounted strain gauges. Their signals are used to derive vibration amplitudes which are compared to modal scope limits, including a safety factor. According to industrial guidelines, this factor is chosen conservatively to ensure safe operation of the machine. Within the experimental campaign with the open-test-case composite fan ECL5/CATANA, which is representative for modern lightweight Ultra High Bypass Ratio (UHBR) architectures, measurements close to the stability limit have been conducted. Investigation of phenomena like non-synchronous vibrations (NSV) and rotating stall require a close approach to the stability limit and hence demand for accurate (real-time) quantification of vibration amplitudes to ensure secure operation without exhaustive safety margins. Historically, short-time Fourier transforms of vibration sensors are used, but the complex nature of the mentioned coupled phenomena has an influence on amplitude accuracy, depending on evaluation parameters, as presented in a previous study using fast-response wall-pressure transducers. The present study investigates the sensitivity of blade vibration data to evaluation parameters for different spectral analysis methods and provides guidelines for fast and robust surveillance of critical vibration modes.

Are bundles good deals for first-order modal logic?

Bundled products are often offered as good deals to customers. In first-order modal logic (FOML), when we bundle quantifiers and modalities together (as in ∃x□, ◇∀x, etc.), we get new logical operators whose combinations produce interesting fragments of FOML without any restriction on the arity of predicates, the number of variables, or the modal scope. It is well-known that finding decidable fragments of FOML is hard, so we may ask: do bundled fragments that exploit the distinct expressivity of FOML constitute good deals in balancing the expressivity and complexity? There are a few positive earlier results towards identifying the decidable ones. In this paper, we map the terrain of bundled fragments of FOML in (un)decidability, and in the cases without a definite answer yet, we show that they lack the finite model property. Moreover, whether the class of models considered has constant domains (across states/worlds) or increasing domains presents another layer of complexity. We also present the loosely bundled fragment, which generalizes the bundles and yet retains decidability (over increasing domain models).

Experimental monitoring of vibrations and the problem of amplitude quantification

Experimental monitoring of blade vibration in turbomachinery is typically based on blade-mounted strain gauges. Their signals are used to derive vibration amplitudes which are compared to previously determined modal scope limits, including a safety factor. According to industrial guidelines, this factor is chosen conservatively to ensure safe operation of the machine.For the experimental campaign with the open test case fan ECL5, which is representative for modern lightweight UHBR architectures, it is planned to conduct measurements close to the stability limit. These investigations require a close approach to the limit and hence demand for accurate quantification of vibration amplitudes to ensure secure operation without exhaustive safety margins. It is required that the surveillance is possible in real time and not only in post-processing.Historically, short-time Fourier transformations of vibration sensors are used, but the complex nature of coupled phenomena near the stability limit has an influence on the amplitude accuracy, depending on evaluation parameters. This was demonstrated in a previous study using fast response wall pressure transducers. The present study investigates the influence on blade vibration data of a modern composite material transonic fan. Different methods are compared, sensitivity to evaluation parameters is analyzed and guidelines are given for fast and robust surveillance of critical vibration modes.

Modal signs and scope relations in TID

Modal signs and scope relations in TID

NETGRAPH – AN EFFICIENT TOOL FOR PERIODIC TIMETABLING AND CAPACITY PLANNING

A netgraph is a graphical representation of a periodic timetable concept for given spatial or modal scope. It adds a third dimension to the network plan – time. Despite no strictly prescribed rules, a common practice notation has been settled over time. The authors propose an extension of a netgraph for planning of periodic railway capacity and operation, including related notation rules.

Space-time constructivism vs. modal provincialism: Or, how special relativistic theories needn't show Minkowski chronogeometry

Already in 1835 Lobachevski entertained the possibility of multiple (one might say “rival”) geometries of the same type playing a role. This idea of rival geometries has reappeared from time to time (including Poincaré and several 20th century authors) but had yet to become a key idea in space-time philosophy prior to Brown's Physical Relativity. Such ideas are emphasized towards the end of Brown's book, which I suggest as the interpretive key. A crucial difference between Brown's constructivist approach to space-time theory and orthodox “space-time realism” pertains to modal scope. Constructivism takes a broad modal scope in applying (at least) to all local classical field theories—modal cosmopolitanism, one might say, including theories with multiple geometries. By contrast the orthodox view is modally provincial in assuming that there exists a unique geometry, as the familiar theories (Newtonian gravity, Special Relativity, Nordström's gravity, and Einstein's General Relativity) have. These theories serve as the “canon” for the orthodox view. Their historical roles also suggest a Whiggish story of inevitable progress. Physics literature after c. 1920 is relevant to orthodoxy primarily as commentary on the canon, which closed in the 1910s. The orthodox view explains the spatio-temporal behavior of matter in terms of the manifestation of the real geometry of space-time, an explanation works fairly well within the canon. The orthodox view, Whiggish history, and the canon have a symbiotic relationship.If one happens to philosophize about a theory outside the canon, space-time realism sheds little light on the spatio-temporal behavior of matter. Worse, it gives the wrong answer when applied to an example arguably within the canon, a sector of Special Relativity, namely, massive scalar gravity with universal coupling. Which is the true geometry—the flat metric from the Poincaré symmetry group, the conformally flat metric exhibited by material rods and clocks, or both—or is the question faulty? How does space-time realism explain the fact that all matter fields see the same curved geometry, when so many ways to mix and match exist? Constructivist attention to dynamical details is vindicated; geometrical shortcuts can disappoint. The more exhaustive exploration of relativistic field theories in particle physics, especially massive theories, is a largely untapped resource for space-time philosophy.

“Philosophy Needs To Find A Place For Imagination Also In The Analysis Of Action”: Faculty Interview with Professor Katja Vogt

In her recent project, Imagination and Agency, Professor Vogt addresses the gap between the philosophical theory and empirical research. I was curious about how this project aims to incorporate philosophical questions into an interdisciplinary debate.
 She explains that there is a significant body of empirical work on mental simulation and imagination as components of agency, since philosophers have also long been interested in imagination. However, philosophers tend to focus on what are called “lofty domains”: thought experiments, science, and art. Vogt argues that philosophy needs to find a place for imagination also in the context of the analysis of action. She thinks that it’s a long-standing idea that, when you make a decision, you decide between options that you consider possible. This is why her project examines the modal scope, the study of ways in which propositions can be true or false, of agential thought, since decision making is concerned with what is and what is not possible. As an example, she cites Aristotle, , who argued that no one deliberates about whether to become a god, because it’s impossible to become a god.

Space–time philosophy reconstructed via massive Nordström scalar gravities? Laws vs. geometry, conventionality, and underdetermination

What if gravity satisfied the Klein–Gordon equation? Both particle physics from the 1920–30s and the 1890s Neumann–Seeliger modification of Newtonian gravity with exponential decay suggest considering a “graviton mass term” for gravity, which is algebraic in the potential. Unlike Nordström׳s “massless” theory, massive scalar gravity is strictly special relativistic in the sense of being invariant under the Poincaré group but not the 15-parameter Bateman–Cunningham conformal group. It therefore exhibits the whole of Minkowski space–time structure, albeit only indirectly concerning volumes. Massive scalar gravity is plausible in terms of relativistic field theory, while violating most interesting versions of Einstein׳s principles of general covariance, general relativity, equivalence, and Mach. Geometry is a poor guide to understanding massive scalar gravity(s): matter sees a conformally flat metric due to universal coupling, but gravity also sees the rest of the flat metric (barely or on long distances) in the mass term. What is the ‘true’ geometry, one might wonder, in line with Poincaré׳s modal conventionality argument? Infinitely many theories exhibit this bimetric ‘geometry,’ all with the total stress–energy׳s trace as source; thus geometry does not explain the field equations. The irrelevance of the Ehlers–Pirani–Schild construction to a critique of conventionalism becomes evident when multi-geometry theories are contemplated. Much as Seeliger envisaged, the smooth massless limit indicates underdetermination of theories by data between massless and massive scalar gravities—indeed an unconceived alternative. At least one version easily could have been developed before General Relativity; it then would have motivated thinking of Einstein׳s equations along the lines of Einstein׳s newly re-appreciated “physical strategy” and particle physics and would have suggested a rivalry from massive spin 2 variants of General Relativity (massless spin 2, Pauli and Fierz found in 1939). The Putnam–Grünbaum debate on conventionality is revisited with an emphasis on the broad modal scope of conventionalist views. Massive scalar gravity thus contributes to a historically plausible rational reconstruction of much of 20th–21st century space–time philosophy in the light of particle physics. An appendix reconsiders the Malament–Weatherall–Manchak conformal restriction of conventionality and constructs the ‘universal force’ influencing the causal structure.Subsequent works will discuss how massive gravity could have provided a template for a more Kant-friendly space–time theory that would have blocked Moritz Schlick׳s supposed refutation of synthetic a priori knowledge, and how Einstein׳s false analogy between the Neumann–Seeliger–Einstein modification of Newtonian gravity and the cosmological constant Λ generated lasting confusion that obscured massive gravity as a conceptual possibility.

Natural Deduction for Modal Logic with a Backtracking Operator

Harold Hodes in [1] introduces an extension of first-order modal logic featuring a backtracking operator, and provides a possible worlds semantics, according to which the operator is a kind of device for ‘world travel’; he does not provide a proof theory. In this paper, I provide a natural deduction system for modal logic featuring this operator, and argue that the system can be motivated in terms of a reading of the backtracking operator whereby it serves to indicate modal scope. I prove soundness and completeness theorems with respect to Hodes’ semantics, as well as semantics with fewer restrictions on the accessibility relation (Hodes restricts his attentionto S5).

Scope ambiguities and conditionals

Scope ambiguities in natural language have been much discussed by linguists and philosophers. There has been some psychological work on the scope ambiguities of negation, but we present the first experiments on modal scope ambiguities in conditionals, with special attention paid to the scope ambiguities of the probability operator. We also discuss the implications of our results for the assessment of the conditional probability hypothesis, according to which the probability of a conditional is the probability of its consequent given its antecedent.

A Logical Hole the Chinese Room Avoids

Searle's Chinese room argument (CRA) was recently charged as being unsound because it makes a logical error. It is shown here that this charge is based on a misinterpretation of the modal scope of a major premise of the CRA and that the CRA does not commit the logical error with which it is charged.

QUESTIONS OF MODALITY

One goal of linguistic theory is to show which expressions determine which contents in which contexts and, conversely, which contents determine which expressions in which contexts. In order for this goal to be realizable, the concept of frequency-based determinacy form is essential. In this paper, aspects of modal expression, modal contents, and modal contexts are viewed within the framework of determinacy grammar, in particular, modal meaning, modal homonymy and polysemy, modal ambiguity resolution, modal scope and sequencing, and modality as causality. In each case, the adopted approach promises to provide precise answers to the questions raised

Scope phenomena in English and Dutch and L2 acquisition: A Case Study

The aim of this paper is to examine how a revised contrastive analysis, based on Chomsky's Government Binding Theory, can be a contribution to L2 acquisition research. The paper illustrates in detail how a contrastive approach in terms of parametric variation between languages may explain persistent errors made by Dutch learners of English. Three parameters are considered: the COMP-INFL parameter, the presence of absence of reanalysis in the VP and the categorial status of modals. These three interact in three related areas of English grammar: i) do-insertion, ii) scope of negation, and iii) modal scope (especially as regards conditionals). It is argued that errors made by Dutch learners in these areas of English grammar are due to an inadequate ‘resetting’ of the parameters involved. A prominent feature of L2 parameter setting seems to be the doubling strategy.