898 research outputs found
Dynamic Connectivity in Disk Graphs
Let S â R2 be a set of n sites in the plane, so that every site s â S has an associated
radius rs > 0. Let D(S) be the disk intersection graph defined by S, i.e., the graph
with vertex set S and an edge between two distinct sites s, t â S if and only if the
disks with centers s, t and radii rs , rt intersect. Our goal is to design data structures
that maintain the connectivity structure of D(S) as sites are inserted and/or deleted
in S. First, we consider unit disk graphs, i.e., we fix rs = 1, for all sites s â S.
For this case, we describe a data structure that has O(log2 n) amortized update time
and O(log n/ log log n) query time. Second, we look at disk graphs with bounded
radius ratio Κ, i.e., for all s â S, we have 1 †rs †Κ, for a parameter Κ that is
known in advance. Here, we not only investigate the fully dynamic case, but also the
incremental and the decremental scenario, where only insertions or only deletions of
sites are allowed. In the fully dynamic case, we achieve amortized expected update
time O(Κ log4 n) and query time O(log n/ log log n). This improves the currently
best update time by a factor of Κ. In the incremental case, we achieve logarithmic
dependency on Κ, with a data structure that has O(α(n)) amortized query time and
O(log Κ log4 n) amortized expected update time, where α(n) denotes the inverse Ackermann
function. For the decremental setting, we first develop an efficient decremental
disk revealing data structure: given two sets R and B of disks in the plane, we can delete
disks from B, and upon each deletion, we receive a list of all disks in R that no longer
intersect the union of B. Using this data structure, we get decremental data structures
with a query time of O(log n/ log log n) that supports deletions in O(n log Κ log4 n)
overall expected time for disk graphs with bounded radius ratio Κ and O(n log5 n)
overall expected time for disk graphs with arbitrary radii, assuming that the deletion
sequence is oblivious of the internal random choices of the data structures
Proceedings of SIRM 2023 - The 15th European Conference on Rotordynamics
It was our great honor and pleasure to host the SIRM Conference after 2003 and 2011 for the third time in Darmstadt. Rotordynamics covers a huge variety of different applications and challenges which are all in the scope of this conference. The conference was opened with a keynote lecture given by Rainer Nordmann, one of the three founders of SIRM âSchwingungen in rotierenden Maschinenâ. In total 53 papers passed our strict review process and were presented. This impressively shows that rotordynamics is relevant as ever. These contributions cover a very wide spectrum of session topics: fluid bearings and seals; air foil bearings; magnetic bearings; rotor blade interaction; rotor fluid interactions; unbalance and balancing; vibrations in turbomachines; vibration control; instability; electrical machines; monitoring, identification and diagnosis; advanced numerical tools and nonlinearities as well as general rotordynamics. The international character of the conference has been significantly enhanced by the Scientific Board since the 14th SIRM resulting on one hand in an expanded Scientific Committee which meanwhile consists of 31 members from 13 different European countries and on the other hand in the new name âEuropean Conference on Rotordynamicsâ. This new international profile has also been
emphasized by participants of the 15th SIRM coming from 17 different countries out of three continents. We experienced a vital discussion and dialogue between industry and academia at the conference where roughly one third of the papers were presented by industry and two thirds by academia being an excellent basis to follow a bidirectional transfer what we call xchange at Technical University of Darmstadt. At this point we also want to give our special thanks to the eleven industry sponsors for their great support of the conference. On behalf of the Darmstadt Local Committee I welcome you to read the papers of the 15th SIRM giving you further insight into the topics and presentations
"Le present est plein de lâavenir, et chargĂ© du passĂ©" : VortrĂ€ge des XI. Internationalen Leibniz-Kongresses, 31. Juli â 4. August 2023, Leibniz UniversitĂ€t Hannover, Deutschland. Band 2
[No abstract available]Deutschen Forschungsgemeinschaft (DFG)/Projektnr. 517991912VGH VersicherungNiedersĂ€chsisches Ministerium fĂŒr Wissenschaft und Kultur (MWK
Geometric Data Analysis: Advancements of the Statistical Methodology and Applications
Data analysis has become fundamental to our society and comes in multiple facets and approaches. Nevertheless, in research and applications, the focus was primarily on data from Euclidean vector spaces. Consequently, the majority of methods that are applied today are not suited for more general data types. Driven by needs from fields like image processing, (medical) shape analysis, and network analysis, more and more attention has recently been given to data from non-Euclidean spacesâparticularly (curved) manifolds. It has led to the field of geometric data analysis whose methods explicitly take the structure (for example, the topology and geometry) of the underlying space into account.
This thesis contributes to the methodology of geometric data analysis by generalizing several fundamental notions from multivariate statistics to manifolds. We thereby focus on two different viewpoints.
First, we use Riemannian structures to derive a novel regression scheme for general manifolds that relies on splines of generalized BĂ©zier curves. It can accurately model non-geodesic relationships, for example, time-dependent trends with saturation effects or cyclic trends. Since BĂ©zier curves can be evaluated with the constructive de Casteljau algorithm, working with data from manifolds of high dimensions (for example, a hundred thousand or more) is feasible. Relying on the regression, we further develop
a hierarchical statistical model for an adequate analysis of longitudinal data in manifolds, and a method to control for confounding variables.
We secondly focus on data that is not only manifold- but even Lie group-valued, which is frequently the case in applications. We can only achieve this by endowing the group with an affine connection structure that is generally not Riemannian. Utilizing it, we derive generalizations of several well-known dissimilarity measures between data distributions that can be used for various tasks, including hypothesis testing. Invariance under data translations is proven, and a connection to continuous distributions is given for one measure.
A further central contribution of this thesis is that it shows use cases for all notions in real-world applications, particularly in problems from shape analysis in medical imaging and archaeology. We can replicate or further quantify several known findings for shape changes of the femur and the right hippocampus under osteoarthritis and Alzheimer's, respectively. Furthermore, in an archaeological application, we obtain new insights into the construction principles of ancient sundials. Last but not least, we use the geometric structure underlying human brain connectomes to predict cognitive scores. Utilizing a sample selection procedure, we obtain state-of-the-art results
2019 GREAT Day Program
SUNY Geneseoâs Thirteenth Annual GREAT Day.https://knightscholar.geneseo.edu/program-2007/1013/thumbnail.jp
Geometry, mechanics and actuation of intrinsically curved folds
We combine theory and experiments to explore the kinematics and actuation of
intrinsically curved folds (ICFs) in otherwise developable shells. Unlike
origami folds, ICFs are not bending isometries of flat sheets, but arise via
non-isometric processes (growth/moulding) or by joining sheets along curved
boundaries. Experimentally, we implement both, first making joined ICFs from
paper, then fabricating flat liquid crystal elastomer (LCE) sheets that morph
into ICFs upon heating/swelling via programmed metric changes. Theoretically,
an ICF's intrinsic geometry is defined by the geodesic curvatures on either
side, . Given these, and a target 3D fold-line, one can construct
the entire surface isometrically, and compute the bending energy. This
construction shows ICFs are bending mechanisms, with a continuous family of
isometries trading fold angle against fold-line curvature. In ICFs with
symmetric , straightening the fold-line culminates in a
fully-folded flat state that is deployable but weak, while asymmetric ICFs
ultimately lock with a mechanically strong finite-angle. When unloaded,
freely-hinged ICFs simply adopt the (thickness independent) isometry that
minimizes the bend energy. In contrast, in LCE ICFs a competition between flank
and ridge selects a ridge curvature that, unusually, scales as .
Finally, we demonstrate how multiple ICFs can be combined in one LCE sheet, to
create a versatile stretch-strong gripper that lifts 40x its own weight.Comment: The supplemental movies are available at
https://drive.google.com/drive/folders/1CR5TdbZNhveHiDYt0_a20O7_nQYS6xZ
Edoardo Benvenuto Prize. Collection of papers
The promotion of studies and research on the science and art of building in their historical development constitutes the objective that the Edoardo Benvenuto Association has set itself, since its establishment, in order to honor the memory of Edoardo Benvenuto (1940-1998). The Association in recent years has achieved interesting results by developing various activities such as: organization of national and international meetings, conferences, study days; collaborations with national and foreign research institutions; promotion of the editorial series âBetween Mechanics and Architecture"; activation of the portal Bibliotheca Mechanica Architectonica, first âopen sourceâ digitized library dedicated to historical research on mechanical and architectural texts. But perhaps the most qualifying initiative was the institution of the Edoardo Benvenuto Prize, arrived in 2019 in its twelfth edition, reserved for young researchers in the field of historical studies on science and the art of building. The awarding of the Prize takes place after an in-depth examination of the texts received by the Association by an international commission of experts. The purpose of this book is to collect and present the most recent studies and publications produced by the winners of the various editions of the Edoardo Benvenuto Prize
Zooming in on the Universe: In Search of Quantum Spacetime
This thesis investigates low-dimensional models of nonperturbative quantum
gravity, with a special focus on Causal Dynamical Triangulations (CDT). We
define the so-called curvature profile, a new quantum gravitational observable
based on the quantum Ricci curvature. We subsequently study its coarse-graining
capabilities on a class of regular, two-dimensional polygons with isolated
curvature singularities, and we determine the curvature profile of
(1+1)-dimensional CDT with toroidal topology. Next, we focus on CDT in 2+1
dimensions, intvestigating the behavior of the two-dimensional spatial slice
geometries. We then turn our attention to matrix models, exploring a
differential reformulation of the integrals over one- and two-matrix ensembles.
Finally, we provide a hands-on introduction to computer simulations of CDT
quantum gravity.Comment: Ph.D. thesi
Anime Studies: media-specific approaches to neon genesis evangelion
Anime Studies: Media-Specific Approaches to Neon Genesis Evangelion aims at advancing the study of anime, understood as largely TV-based genre fiction rendered in cel, or cel-look, animation with a strong affinity to participatory cultures and media convergence. Making Neon Genesis Evangelion (Shin Seiki Evangerion, 1995-96) its central case and nodal point, this volumen forground anime as a media with clearly recognizable aesthetic properties, (sub)cultural affordances and situated discourses
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