TY - JOUR
AB - Material appearance hinges on material reflectance properties but also surface geometry and illumination. The unlimited number of potential combinations between these factors makes understanding and predicting material appearance a very challenging task. In this work, we collect a large-scale dataset of perceptual ratings of appearance attributes with more than 215,680 responses for 42,120 distinct combinations of material, shape, and illumination. The goal of this dataset is twofold. First, we analyze for the first time the effects of illumination and geometry in material perception across such a large collection of varied appearances. We connect our findings to those of the literature, discussing how previous knowledge generalizes across very diverse materials, shapes, and illuminations. Second, we use the collected dataset to train a deep learning architecture for predicting perceptual attributes that correlate with human judgments. We demonstrate the consistent and robust behavior of our predictor in various challenging scenarios, which, for the first time, enables estimating perceived material attributes from general 2D images. Since our predictor relies on the final appearance in an image, it can compare appearance properties across different geometries and illumination conditions. Finally, we demonstrate several applications that use our predictor, including appearance reproduction using 3D printing, BRDF editing by integrating our predictor in a differentiable renderer, illumination design, or material recommendations for scene design.
AU - Serrano, Ana
AU - Chen, Bin
AU - Wang, Chao
AU - Piovarci, Michael
AU - Seidel, Hans Peter
AU - Didyk, Piotr
AU - Myszkowski, Karol
ID - 9820
IS - 4
JF - ACM Transactions on Graphics
SN - 07300301
TI - The effect of shape and illumination on material perception: Model and applications
VL - 40
ER -
TY - JOUR
AB - Heart rate variability (hrv) is a physiological phenomenon of the variation in the length of the time interval between consecutive heartbeats. In many cases it could be an indicator of the development of pathological states. The classical approach to the analysis of hrv includes time domain methods and frequency domain methods. However, attempts are still being made to define new and more effective hrv assessment tools. Persistent homology is a novel data analysis tool developed in the recent decades that is rooted at algebraic topology. The Topological Data Analysis (TDA) approach focuses on examining the shape of the data in terms of connectedness and holes, and has recently proved to be very effective in various fields of research. In this paper we propose the use of persistent homology to the hrv analysis. We recall selected topological descriptors used in the literature and we introduce some new topological descriptors that reflect the specificity of hrv, and we discuss their relation to the standard hrv measures. In particular, we show that this novel approach provides a collection of indices that might be at least as useful as the classical parameters in differentiating between series of beat-to-beat intervals (RR-intervals) in healthy subjects and patients suffering from a stroke episode.
AU - Graff, Grzegorz
AU - Graff, Beata
AU - Pilarczyk, Pawel
AU - Jablonski, Grzegorz
AU - Gąsecki, Dariusz
AU - Narkiewicz, Krzysztof
ID - 9821
IS - 7
JF - PLoS ONE
TI - Persistent homology as a new method of the assessment of heart rate variability
VL - 16
ER -
TY - JOUR
AB - Attachment of adhesive molecules on cell culture surfaces to restrict cell adhesion to defined areas and shapes has been vital for the progress of in vitro research. In currently existing patterning methods, a combination of pattern properties such as stability, precision, specificity, high-throughput outcome, and spatiotemporal control is highly desirable but challenging to achieve. Here, we introduce a versatile and high-throughput covalent photoimmobilization technique, comprising a light-dose-dependent patterning step and a subsequent functionalization of the pattern via click chemistry. This two-step process is feasible on arbitrary surfaces and allows for generation of sustainable patterns and gradients. The method is validated in different biological systems by patterning adhesive ligands on cell-repellent surfaces, thereby constraining the growth and migration of cells to the designated areas. We then implement a sequential photopatterning approach by adding a second switchable patterning step, allowing for spatiotemporal control over two distinct surface patterns. As a proof of concept, we reconstruct the dynamics of the tip/stalk cell switch during angiogenesis. Our results show that the spatiotemporal control provided by our “sequential photopatterning” system is essential for mimicking dynamic biological processes and that our innovative approach has great potential for further applications in cell science.
AU - Zisis, Themistoklis
AU - Schwarz, Jan
AU - Balles, Miriam
AU - Kretschmer, Maibritt
AU - Nemethova, Maria
AU - Chait, Remy P
AU - Hauschild, Robert
AU - Lange, Janina
AU - Guet, Calin C
AU - Sixt, Michael K
AU - Zahler, Stefan
ID - 9822
IS - 30
JF - ACS Applied Materials and Interfaces
SN - 19448244
TI - Sequential and switchable patterning for studying cellular processes under spatiotemporal control
VL - 13
ER -
TY - CONF
AB - Approximate agreement is one of the few variants of consensus that can be solved in a wait-free manner in asynchronous systems where processes communicate by reading and writing to shared memory. In this work, we consider a natural generalisation of approximate agreement on arbitrary undirected connected graphs. Each process is given a vertex of the graph as input and, if non-faulty, must output a vertex such that
all the outputs are within distance 1 of one another, and
each output value lies on a shortest path between two input values.
From prior work, it is known that there is no wait-free algorithm among 𝑛≥3 processes for this problem on any cycle of length 𝑐≥4 , by reduction from 2-set agreement (Castañeda et al. 2018).
In this work, we investigate the solvability and complexity of this task on general graphs. We give a new, direct proof of the impossibility of approximate agreement on cycles of length 𝑐≥4 , via a generalisation of Sperner’s Lemma to convex polygons. We also extend the reduction from 2-set agreement to a larger class of graphs, showing that approximate agreement on these graphs is unsolvable. On the positive side, we present a wait-free algorithm for a class of graphs that properly contains the class of chordal graphs.
AU - Alistarh, Dan-Adrian
AU - Ellen, Faith
AU - Rybicki, Joel
ID - 9823
SN - 03029743
T2 - Structural Information and Communication Complexity
TI - Wait-free approximate agreement on graphs
VL - 12810
ER -
TY - CONF
AB - We define a new compact coordinate system in which each integer triplet addresses a voxel in the BCC grid, and we investigate some of its properties. We propose a characterization of 3D discrete analytical planes with their topological features (in the Cartesian and in the new coordinate system) such as the interrelation between the thickness of the plane and the separability constraint we aim to obtain.
AU - Čomić, Lidija
AU - Zrour, Rita
AU - Largeteau-Skapin, Gaëlle
AU - Biswas, Ranita
AU - Andres, Eric
ID - 9824
SN - 03029743
T2 - Discrete Geometry and Mathematical Morphology
TI - Body centered cubic grid - coordinate system and discrete analytical plane definition
VL - 12708
ER -
TY - CONF
AB - The dual attack has long been considered a relevant attack on lattice-based cryptographic schemes relying on the hardness of learning with errors (LWE) and its structured variants. As solving LWE corresponds to finding a nearest point on a lattice, one may naturally wonder how efficient this dual approach is for solving more general closest vector problems, such as the classical closest vector problem (CVP), the variants bounded distance decoding (BDD) and approximate CVP, and preprocessing versions of these problems. While primal, sieving-based solutions to these problems (with preprocessing) were recently studied in a series of works on approximate Voronoi cells [Laa16b, DLdW19, Laa20, DLvW20], for the dual attack no such overview exists, especially for problems with preprocessing. With one of the take-away messages of the approximate Voronoi cell line of work being that primal attacks work well for approximate CVP(P) but scale poorly for BDD(P), one may further wonder if the dual attack suffers the same drawbacks, or if it is perhaps a better solution when trying to solve BDD(P).
In this work we provide an overview of cost estimates for dual algorithms for solving these “classical” closest lattice vector problems. Heuristically we expect to solve the search version of average-case CVPP in time and space 20.293𝑑+𝑜(𝑑) in the single-target model. The distinguishing version of average-case CVPP, where we wish to distinguish between random targets and targets planted at distance (say) 0.99⋅𝑔𝑑 from the lattice, has the same complexity in the single-target model, but can be solved in time and space 20.195𝑑+𝑜(𝑑) in the multi-target setting, when given a large number of targets from either target distribution. This suggests an inequivalence between distinguishing and searching, as we do not expect a similar improvement in the multi-target setting to hold for search-CVPP. We analyze three slightly different decoders, both for distinguishing and searching, and experimentally obtain concrete cost estimates for the dual attack in dimensions 50 to 80, which confirm our heuristic assumptions, and show that the hidden order terms in the asymptotic estimates are quite small.
Our main take-away message is that the dual attack appears to mirror the approximate Voronoi cell line of work – whereas using approximate Voronoi cells works well for approximate CVP(P) but scales poorly for BDD(P), the dual approach scales well for BDD(P) instances but performs poorly on approximate CVP(P).
AU - Laarhoven, Thijs
AU - Walter, Michael
ID - 9825
SN - 03029743
T2 - Topics in Cryptology – CT-RSA 2021
TI - Dual lattice attacks for closest vector problems (with preprocessing)
VL - 12704
ER -
TY - CONF
AB - Automated contract tracing aims at supporting manual contact tracing during pandemics by alerting users of encounters with infected people. There are currently many proposals for protocols (like the “decentralized” DP-3T and PACT or the “centralized” ROBERT and DESIRE) to be run on mobile phones, where the basic idea is to regularly broadcast (using low energy Bluetooth) some values, and at the same time store (a function of) incoming messages broadcasted by users in their proximity. In the existing proposals one can trigger false positives on a massive scale by an “inverse-Sybil” attack, where a large number of devices (malicious users or hacked phones) pretend to be the same user, such that later, just a single person needs to be diagnosed (and allowed to upload) to trigger an alert for all users who were in proximity to any of this large group of devices.
We propose the first protocols that do not succumb to such attacks assuming the devices involved in the attack do not constantly communicate, which we observe is a necessary assumption. The high level idea of the protocols is to derive the values to be broadcasted by a hash chain, so that two (or more) devices who want to launch an inverse-Sybil attack will not be able to connect their respective chains and thus only one of them will be able to upload. Our protocols also achieve security against replay, belated replay, and one of them even against relay attacks.
AU - Auerbach, Benedikt
AU - Chakraborty, Suvradip
AU - Klein, Karen
AU - Pascual Perez, Guillermo
AU - Pietrzak, Krzysztof Z
AU - Walter, Michael
AU - Yeo, Michelle X
ID - 9826
SN - 03029743
T2 - Topics in Cryptology – CT-RSA 2021
TI - Inverse-Sybil attacks in automated contact tracing
VL - 12704
ER -
TY - JOUR
AB - The Nearest neighbour search (NNS) is a fundamental problem in many application domains dealing with multidimensional data. In a concurrent setting, where dynamic modifications are allowed, a linearizable implementation of the NNS is highly desirable.This paper introduces the LockFree-kD-tree (LFkD-tree ): a lock-free concurrent kD-tree, which implements an abstract data type (ADT) that provides the operations Add, Remove, Contains, and NNS. Our implementation is linearizable. The operations in the LFkD-tree use single-word read and compare-and-swap (Image 1 ) atomic primitives, which are readily supported on available multi-core processors. We experimentally evaluate the LFkD-tree using several benchmarks comprising real-world and synthetic datasets. The experiments show that the presented design is scalable and achieves significant speed-up compared to the implementations of an existing sequential kD-tree and a recently proposed multidimensional indexing structure, PH-tree.
AU - Chatterjee, Bapi
AU - Walulya, Ivan
AU - Tsigas, Philippas
ID - 9827
JF - Theoretical Computer Science
KW - Concurrent data structure
KW - kD-tree
KW - Nearest neighbor search
KW - Similarity search
KW - Lock-free
KW - Linearizability
SN - 03043975
TI - Concurrent linearizable nearest neighbour search in LockFree-kD-tree
ER -
TY - JOUR
AB - Amplitude demodulation is a classical operation used in signal processing. For a long time, its effective applications in practice have been limited to narrowband signals. In this work, we generalize amplitude demodulation to wideband signals. We pose demodulation as a recovery problem of an oversampled corrupted signal and introduce special iterative schemes belonging to the family of alternating projection algorithms to solve it. Sensibly chosen structural assumptions on the demodulation outputs allow us to reveal the high inferential accuracy of the method over a rich set of relevant signals. This new approach surpasses current state-of-the-art demodulation techniques apt to wideband signals in computational efficiency by up to many orders of magnitude with no sacrifice in quality. Such performance opens the door for applications of the amplitude demodulation procedure in new contexts. In particular, the new method makes online and large-scale offline data processing feasible, including the calculation of modulator-carrier pairs in higher dimensions and poor sampling conditions, independent of the signal bandwidth. We illustrate the utility and specifics of applications of the new method in practice by using natural speech and synthetic signals.
AU - Gabrielaitis, Mantas
ID - 9828
JF - IEEE Transactions on Signal Processing
SN - 1053-587X
TI - Fast and accurate amplitude demodulation of wideband signals
VL - 69
ER -
TY - JOUR
AB - In 2020, many in-person scientific events were canceled due to the COVID-19 pandemic, creating a vacuum in networking and knowledge exchange between scientists. To fill this void in scientific communication, a group of early career nanocrystal enthusiasts launched the virtual seminar series, News in Nanocrystals, in the summer of 2020. By the end of the year, the series had attracted over 850 participants from 46 countries. In this Nano Focus, we describe the process of organizing the News in Nanocrystals seminar series; discuss its growth, emphasizing what the organizers have learned in terms of diversity and accessibility; and provide an outlook for the next steps and future opportunities. This summary and analysis of experiences and learned lessons are intended to inform the broader scientific community, especially those who are looking for avenues to continue fostering discussion and scientific engagement virtually, both during the pandemic and after.
AU - Baranov, Dmitry
AU - Šverko, Tara
AU - Moot, Taylor
AU - Keller, Helena R.
AU - Klein, Megan D.
AU - Vishnu, E. K.
AU - Balazs, Daniel
AU - Shulenberger, Katherine E.
ID - 9829
IS - 7
JF - ACS Nano
SN - 19360851
TI - News in Nanocrystals seminar: Self-assembly of early career researchers toward globally accessible nanoscience
VL - 15
ER -