pwc-archive/papers-with-abstracts huggingface dataset:
Extracting Governing Laws from Sample Path Data of Non-Gaussian Stochastic Dynamical Systems
Authors: Yang Li, Jinqiao Duan
Date: 2021-07-21 00:00:00

Advances in data science are leading to new progresses in the analysis and understanding of complex dynamics for systems with experimental and observational data. With numerous physical phenomena exhibiting bursting, flights, hopping, and intermittent features, stochastic differential equations with non-Gaussian L\'evy noise are suitable to model these systems. Thus it is desirable and essential to infer such equations from available data to reasonably predict dynamical behaviors. In this work, we consider a data-driven method to extract stochastic dynamical systems with non-Gaussian asymmetric (rather than the symmetric) L\'evy process, as well as Gaussian Brownian motion. We establish a theoretical framework and design a numerical algorithm to compute the asymmetric L\'evy jump measure, drift and diffusion (i.e., nonlocal Kramers-Moyal formulas), hence obtaining the stochastic governing law, from noisy data. Numerical experiments on several prototypical examples confirm the efficacy and accuracy of this method. This method will become an effective tool in discovering the governing laws from available data sets and in understanding the mechanisms underlying complex random phenomena.
Provenance, Anonymisation and Data Environments: a Unifying Construction
Authors: Muhammad Aslam Jarwar, Adriane Chapman, Mark Elliot, Fatemeh Raji
Date: 2021-07-21 00:00:00
Tasks: Decision Making, Management

The Anonymisation Decision-making Framework (ADF) operationalizes the risk management of data exchange between organizations, referred to as "data environments". The second edition of ADF has increased its emphasis on modeling data flows, highlighting a potential new use of provenance information to support anonymisation decision-making. In this paper, we provide a use case that showcases this functionality more. Based on this use case, we identify how provenance information could be utilized within the ADF framework, and identify a currently un-met requirement which is the modeling of \textit{data environments}. We show how data environments can be implemented within the W3C PROV in four different ways. We analyze the costs and benefits of each approach, and consider another use case as a partial check for completeness. We then summarize our findings and suggest ways forward.
Learning Heuristics for Template-based CEGIS of Loop Invariants with Reinforcement Learning
Authors: Minchao Wu, Takeshi Tsukada, Hiroshi Unno, Taro Sekiyama, Kohei Suenaga
Date: 2021-07-16 00:00:00
Tasks: reinforcement-learning, Reinforcement Learning (RL)

Loop-invariant synthesis is the basis of program verification. Due to the undecidability of the problem in general, a tool for invariant synthesis necessarily uses heuristics. Despite the common belief that the design of heuristics is vital for the performance of a synthesizer, heuristics are often engineered by their developers based on experience and intuition, sometimes in an \emph{ad-hoc} manner. In this work, we propose an approach to systematically learning heuristics for template-based CounterExample-Guided Inductive Synthesis (CEGIS) with reinforcement learning. As a concrete example, we implement the approach on top of PCSat, which is an invariant synthesizer based on template-based CEGIS. Experiments show that PCSat guided by the heuristics learned by our framework not only outperforms existing state-of-the-art CEGIS-based solvers such as HoICE and the neural solver Code2Inv, but also has slight advantages over non-CEGIS-based solvers such as Eldarica and Spacer in linear Constrained Horn Clause (CHC) solving.
Controlling the Remixing of Separated Dialogue with a Non-Intrusive Quality Estimate
Authors: Matteo Torcoli, Jouni Paulus, Thorsten Kastner, Christian Uhle
Date: 2021-07-21 00:00:00

Remixing separated audio sources trades off interferer attenuation against the amount of audible deteriorations. This paper proposes a non-intrusive audio quality estimation method for controlling this trade-off in a signal-adaptive manner. The recently proposed 2f-model is adopted as the underlying quality measure, since it has been shown to correlate strongly with basic audio quality in source separation. An alternative operation mode of the measure is proposed, more appropriate when considering material with long inactive periods of the target source. The 2f-model requires the reference target source as an input, but this is not available in many applications. Deep neural networks (DNNs) are trained to estimate the 2f-model intrusively using the reference target (iDNN2f), non-intrusively using the input mix as reference (nDNN2f), and reference-free using only the separated output signal (rDNN2f). It is shown that iDNN2f achieves very strong correlation with the original measure on the test data (Pearson r=0.99), while performance decreases for nDNN2f (r>=0.91) and rDNN2f (r>=0.82). The non-intrusive estimate nDNN2f is mapped to select item-dependent remixing gains with the aim of maximizing the interferer attenuation under a constraint on the minimum quality of the remixed output (e.g., audible but not annoying deteriorations). A listening test shows that this is successfully achieved even with very different selected gains (up to 23 dB difference).
Constrained Power Reference Control for Wind Turbines
Authors: Daniel S. Zalkind, Marco M. Nicotra, Lucy Y. Pao
Date: 2021-07-21 00:00:00

The cost of wind energy can be reduced by controlling the power reference of a turbine to increase energy capture, while maintaining load and generator speed constraints. We apply standard torque and pitch controllers to the direct inputs of the turbine and use their set points to change the power output and reduce generator speed and blade load transients. A power reference controller increases the power output when conditions are safe and decreases it when problematic transient events are expected. Transient generator speeds and blade loads are estimated using a gust measure derived from a wind speed estimate. A hybrid controller decreases the power rating from a maximum allowable power. Compared to a baseline controller, with a constant power reference, the proposed controller results in generator speeds and blade loads that do not exceed the original limits, increases tower fore-aft damage equivalent loads by 1%, and increases the annual energy production by 5%.
A Network Control Theory Approach to Longitudinal Symptom Dynamics in Major Depressive Disorder
Authors: Tim Hahn, Hamidreza Jamalabadi, Daniel Emden, Janik Goltermann, Jan Ernsting, Nils R. Winter, Lukas Fisch, Ramona Leenings, Kelvin Sarink, Vincent Holstein, Marius Gruber, Dominik Grotegerd, Susanne Meinert, Katharina Dohm, Elisabeth J. Leehr, Maike Richter, Lisa Sindermann, Verena Enneking, Hannah Lemke, Stephanie Witt, Marcella Rietschel, Katharina Brosch, Julia-Katharina Pfarr, Tina Meller, Kai Gustav Ringwald, Simon Schmitt, Frederike Stein, Igor Nenadic, Tilo Kircher, Bertram Müller-Myhsok, Till F. M. Andlauer, Jonathan Repple, Udo Dannlowski, Nils Opel
Date: 2021-07-21 00:00:00

Background: The evolution of symptoms over time is at the heart of understanding and treating mental disorders. However, a principled, quantitative framework explaining symptom dynamics remains elusive. Here, we propose a Network Control Theory of Psychopathology allowing us to formally derive a theoretical control energy which we hypothesize quantifies resistance to future symptom improvement in Major Depressive Disorder (MDD). We test this hypothesis and investigate the relation to genetic and environmental risk as well as resilience. Methods: We modelled longitudinal symptom-network dynamics derived from N=2,059 Beck Depression Inventory measurements acquired over a median of 134 days in a sample of N=109 patients suffering from MDD. We quantified the theoretical energy required for each patient and time-point to reach a symptom-free state given individual symptom-network topology (E 0 ) and 1) tested if E 0 predicts future symptom improvement and 2) whether this relationship is moderated by Polygenic Risk Scores (PRS) of mental disorders, childhood maltreatment experience, and self-reported resilience. Outcomes: We show that E 0 indeed predicts symptom reduction at the next measurement and reveal that this coupling between E 0 and future symptom change increases with higher genetic risk and childhood maltreatment while it decreases with resilience. Interpretation: Our study provides a mechanistic framework capable of predicting future symptom improvement based on individual symptom-network topology and clarifies the role of genetic and environmental risk as well as resilience. Our control-theoretic framework makes testable, quantitative predictions for individual therapeutic response and provides a starting-point for the theory-driven design of personalized interventions. Funding: German Research Foundation and Interdisciplinary Centre for Clinical Research, M\"unster
Genetic, Individual, and Familial Risk Correlates of Brain Network Controllability in Major Depressive Disorder
Authors: Tim Hahn, Nils R. Winter, Jan Ernsting, Marius Gruber, Marco J. Mauritz, Lukas Fisch, Ramona Leenings, Kelvin Sarink, Julian Blanke, Vincent Holstein, Daniel Emden, Marie Beisemann, Nils Opel, Dominik Grotegerd, Susanne Meinert, Walter Heindel, Stephanie Witt, Marcella Rietschel, Markus M. Nöthen, Andreas J. Forstner, Tilo Kircher, Igor Nenadic, Andreas Jansen, Bertram Müller-Myhsok, Till F. M. Andlauer, Martin Walter, Martijn P. van den Heuvel, Hamidreza Jamalabadi, Udo Dannlowski, Jonathan Repple
Date: 2021-07-21 00:00:00

Background: A therapeutic intervention in psychiatry can be viewed as an attempt to influence the brain's large-scale, dynamic network state transitions underlying cognition and behavior. Building on connectome-based graph analysis and control theory, Network Control Theory is emerging as a powerful tool to quantify network controllability - i.e., the influence of one brain region over others regarding dynamic network state transitions. If and how network controllability is related to mental health remains elusive. Methods: From Diffusion Tensor Imaging data, we inferred structural connectivity and inferred calculated network controllability parameters to investigate their association with genetic and familial risk in patients diagnosed with major depressive disorder (MDD, n=692) and healthy controls (n=820). Results: First, we establish that controllability measures differ between healthy controls and MDD patients while not varying with current symptom severity or remission status. Second, we show that controllability in MDD patients is associated with polygenic scores for MDD and psychiatric cross-disorder risk. Finally, we provide evidence that controllability varies with familial risk of MDD and bipolar disorder as well as with body mass index. Conclusions: We show that network controllability is related to genetic, individual, and familial risk in MDD patients. We discuss how these insights into individual variation of network controllability may inform mechanistic models of treatment response prediction and personalized intervention-design in mental health.
Encoding Impact of Network Modification on Controllability via Edge Centrality Matrix
Authors: Prasad Vilas Chanekar, Jorge Cortes
Date: 2021-07-21 00:00:00

This paper develops tools to quantify the importance of agent interactions and its impact on global performance metrics for networks modeled as linear time-invariant systems. We consider Gramian-based performance metrics and propose a novel notion of edge centrality that encodes the first-order variation in the metric with respect to the modification of the corresponding edge weight, including for those edges not present in the network. The proposed edge centrality matrix (ECM) is additive over the set of inputs, i.e., it captures the specific contribution to each edge's centrality of the presence of any given actuator. We provide a full characterization of the ECM structure for the class of directed stem-bud networks, showing that non-zero entries are only possible at specific sub/super-diagonals determined by the network size and the length of its bud. We also provide bounds on the value of the trace, trace inverse, and log-det of the Gramian before and after single-edge modifications, and on the edge-modification weight to ensure the modified network retains stability. Simulations show the utility of the proposed edge centrality notion and validate our results.
Instabilizability Conditions for Continuous-Time Stochastic Systems Under Control Input Constraints
Authors: Ahmet Cetinkaya, Masako Kishida
Date: 2021-07-21 00:00:00

In this paper, we investigate constrained control of continuous-time linear stochastic systems. We show that for certain system parameter settings, constrained control policies can never achieve stabilization. Specifically, we explore a class of control policies that are constrained to have a bounded average second moment for Ito-type stochastic differential equations with additive and multiplicative noise. We prove that in certain settings of the system parameters and the bounding constant of the control constraint, divergence of the second moment of the system state is inevitable regardless of the initial state value and regardless of how the control policy is designed.
Frequency-Domain Data-Driven Controller Synthesis for Unstable LPV Systems
Authors: Tom Bloemers, Roland Tóth, Tom Oomen
Date: 2021-07-20 00:00:00

Synthesizing controllers directly from frequency-domain measurement data is a powerful tool in the linear time-invariant framework. Ever-increasing performance requirements necessitate extending these approaches to account for plant variations. The aim of this paper is to develop frequency-domain analysis and synthesis conditions for local internal stability and $\mathcal{H}_\infty$-performance of single-input single-output linear parameter-varying systems. The developed synthesis procedure only requires frequency-domain measurement data of the system and does not need a parametric model of the plant. The capabilities of the synthesis procedure are demonstrated on an unstable nonlinear system.
Diseases on complex networks. Modeling from a database and a protection strategy proposal
Authors: Ronald Manríquez, Camilo Guerrero-Nancuante
Date: 2021-07-20 00:00:00

Among the diverse and important applications that networks currently have is the modeling of infectious diseases. Immunization, or the process of protecting nodes in the network, plays a key role in stopping diseases from spreading. Hence the importance of having tools or strategies that allow the solving of this challenge. In this work, we evaluate the effectiveness of the DIL-W^{\alpha} ranking in immunizing nodes in an edge-weighted network. The network is obtained from a real database and the spread of COVID-19 was modeled with the classic SIR model. We apply the protection to the network, according to the importance ranking list produced by DIL-W^{\alpha}.
Recent Developments in Inference: Practicalities for Applied Economics
Authors: Jeffrey D. Michler, Anna Josephson
Date: 2021-07-20 00:00:00

We provide a review of recent developments in the calculation of standard errors and test statistics for statistical inference. While much of the focus of the last two decades in economics has been on generating unbiased coefficients, recent years has seen a variety of advancements in correcting for non-standard standard errors. We synthesize these recent advances in addressing challenges to conventional inference, like heteroskedasticity, clustering, serial correlation, and testing multiple hypotheses. We also discuss recent advancements in numerical methods, such as the bootstrap, wild bootstrap, and randomization inference. We make three specific recommendations. First, applied economists need to clearly articulate the challenges to statistical inference that are present in data as well as the source of those challenges. Second, modern computing power and statistical software means that applied economists have no excuse for not correctly calculating their standard errors and test statistics. Third, because complicated sampling strategies and research designs make it difficult to work out the correct formula for standard errors and test statistics, we believe that in the applied economics profession it should become standard practice to rely on asymptotic refinements to the distribution of an estimator or test statistic via bootstrapping. Throughout, we reference built-in and user-written Stata commands that allow one to quickly calculate accurate standard errors and relevant test statistics.
Vehicle 24-Color Long Tail Recognition Based on Smooth Modulation Neural Network with Multi-layer Feature Representation
Authors: Hu Ming-Di, Bai Long, Li Ying, Zhao Si-Rui, Chen En-Hong
Date: 2021-07-21 00:00:00
Tasks: Management, Vehicle Color Recognition

Vehicle color recognition plays an important role in intelligent traffic management and criminal investigation assistance. However, the current vehicle color recognition research involves at most 13 types of colors and the recognition accuracy is low, which is difficult to meet practical applications. To this end, this paper has built a benchmark dataset (Vehicle Color-24) that includes 24 types of vehicle colors, including 10091 vehicle pictures taken from 100 hours of urban road surveillance videos. In addition, in order to solve the problem of long tail distribution in Vehicle Color-24 dataset and low recognition rate of existing methods, this paper proposes a Smooth Modulated Neural Network with Multi-layer Feature Representation (SMNN-MFR) is used for 24 types of vehicle color recognition. SMNN-MFR includes four parts: feature extraction, multi-scale feature fusion, suggestion frame generation and smooth modulation. The model is trained and verified on the Vehicle Color-24 benchmark dataset. Comprehensive experiments show that the average recognition accuracy of the algorithm in the 24 categories of color benchmark databases is 94.96%, which is 33.47% higher than the Faster RCNN network. In addition, the average accuracy rate of the model when recognizing 8 types of colors is 97.25%, and the detection accuracy of algorithms in similar databases is improved. At the same time, visualization and ablation experiments also proved the rationality of our network settings and the effectiveness of each module. The code and database are published at: https://github.com/mendy-2013.
Two Efficient and Easy-to-Use NLOS Mitigation Solutions to Indoor 3-D AOA-Based Localization
Authors: Wenxin Xiong, Joan Bordoy, Andrea Gabbrielli, Georg Fischer, Dominik Jan Schott, Fabian Hoeflinger, Johannes Wendeberg, Christian Schindelhauer, Stefan Johann Rupitsch
Date: 2021-07-21 00:00:00

This paper proposes two efficient and easy-to-use error mitigation solutions to the problem of three-dimensional (3-D) angle-of-arrival (AOA) source localization in the mixed line-of-sight (LOS) and non-line-of-sight (NLOS) indoor environments. A weighted linear least squares estimator is derived first for the LOS AOA components in terms of the direction vectors of arrival, albeit in a sub-optimal manner. Next, data selection exploiting the sum of squared residuals is carried out to discard the error-prone NLOS connections. In so doing, the first approach is constituted and more accurate closed-form location estimates can be obtained. The second method applies a simulated annealing stochastic framework to realize the robust $\ell_1$-minimization criterion, which therefore falls into the methodology of statistical robustification. Computer simulations and ultrasonic onsite experiments are conducted to evaluate the performance of the two proposed methods, demonstrating their outstanding positioning results in the respective scenarios.
Convolutional Sparse Coding based Channel Estimation for OTFS-SCMA in Uplink
Authors: Anna Thomas, Kuntal Deka, P. Raviteja, Sanjeev Sharma
Date: 2021-07-21 00:00:00

Orthogonal time frequency space (OTFS) has emerged as the most sought-after modulation technique in a high mobility scenario. Sparse code multiple access (SCMA) is an attractive code-domain non-orthogonal multiple access (NOMA) technique. Recently a code-domain NOMA approach for OTFS, named OTFS-SCMA, is proposed. OTFS-SCMA is a promising framework that meets the demands of high mobility and massive connectivity. This paper presents a channel estimation technique based on the convolutional sparse coding (CSC) approach for OTFS-SCMA in the uplink. The channel estimation task is formulated as a CSC problem following a careful rearrangement of the OTFS input-output relation. We use an embedded pilot-aided sparse-pilot structure that enjoys the features of both OTFS and SCMA. The existing channel estimation techniques for OTFS in multi-user scenarios for uplink demand extremely high overhead for pilot and guard symbols, proportional to the number of users. The proposed method maintains a minimal overhead equivalent to a single user without compromising on the estimation error. The results show that the proposed channel estimation algorithm is very efficient in bit error rate (BER), normalized mean square error (NMSE), and spectral efficiency (SE).
Fiber decomposition of deterministic reaction networks with applications
Authors: Carsten Wiuf, Chuang Xu
Date: 2021-07-18 00:00:00
Tasks: Epidemiology

Deterministic reaction networks (RNs) are tools to model diverse biological phenomena characterized by particle systems, when there are abundant number of particles. Examples include but are not limited to biochemistry, molecular biology, genetics, epidemiology, and social sciences. In this chapter we propose a new type of decomposition of RNs, called fiber decomposition. Using this decomposition, we establish lifting of mass-action RNs preserving stationary properties, including multistationarity and absolute concentration robustness. Such lifting scheme is simple and explicit which imposes little restriction on the reaction networks. We provide examples to illustrate how this lifting can be used to construct RNs preserving certain dynamical properties.
Variant-driven multi-wave pattern of COVID-19 via a Machine Learning analysis of spike protein mutations
Authors: Adele de Hoffer, Shahram Vatani, Corentin Cot, Giacomo Cacciapaglia, Maria Luisa Chiusano, Andrea Cimarelli, Francesco Conventi, Antonio Giannini, Stefan Hohenegger, Francesco Sannino
Date: 2021-07-21 00:00:00

Applying a ML approach to the temporal variability of the Spike protein sequence enables us to identify, classify and track emerging virus variants. Our analysis is unbiased, in the sense that it does not require any prior knowledge of the variant characteristics, and our results are validated by other informed methods that define variants based on the complete genome. Furthermore, correlating persistent variants of our approach to epidemiological data, we discover that each new wave of the COVID-19 pandemic is driven and dominated by a new emerging variant. Our results are therefore indispensable for further studies on the evolution of SARS-CoV-2 and the prediction of evolutionary patterns that determine current and future mutations of the Spike proteins, as well as their diversification and persistence during the viral spread. Moreover, our ML algorithm works as an efficient early warning system for the emergence of new persistent variants that may pose a threat of triggering a new wave of COVID-19. Capable of a timely identification of potential new epidemiological threats when the variant only represents 1% of the new sequences, our ML strategy is a crucial tool for decision makers to define short and long term strategies to curb future outbreaks. The same methodology can be applied to other viral diseases, influenza included, if sufficient sequencing data is available.