pwc-archive/papers-with-abstracts huggingface dataset:
Low case numbers enable long-term stable pandemic control without lockdowns
Authors: Sebastian Contreras, Jonas Dehning, Sebastian B. Mohr, Simon Bauer, F. Paul Spitzner, Viola Priesemann
Date: 2020-11-23 00:00:00

The traditional long-term solutions for epidemic control involve eradication or population immunity. Here, we analytically derive the existence of a third viable solution: a stable equilibrium at low case numbers, where test-trace-and-isolate policies partially compensate for local spreading events, and only moderate restrictions remain necessary. In this equilibrium, daily cases stabilize around ten new infections per million people or less. However, stability is endangered if restrictions are relaxed or case numbers grow too high. The latter destabilization marks a tipping point beyond which the spread self-accelerates. We show that a lockdown can reestablish control and that recurring lockdowns are not necessary given sustained, moderate contact reduction. We illustrate how this strategy profits from vaccination and helps mitigate variants of concern. This strategy reduces cumulative cases (and fatalities) 4x more than strategies that only avoid hospital collapse. In the long term, immunization, large-scale testing, and international coordination will further facilitate control.
A Keller-Segel model for C elegans L1 aggregation
Authors: Leon Avery, Brian Ingalls, Catherine Dumur, Alexander Artyukhin
Date: 2020-12-04 00:00:00

We describe a mathematical model for the aggregation of starved first-stage C elegans larvae (L1s). We propose that starved L1s produce and respond chemotactically to two labile diffusible chemical signals, a short-range attractant and a longer range repellent. This model takes the mathematical form of three coupled partial differential equations, one that describes the movement of the worms and one for each of the chemical signals. Numerical solution of these equations produced a pattern of aggregates that resembled that of worm aggregates observed in experiments. We also describe the identification of a sensory receptor gene, srh-2, whose expression is induced under conditions that promote L1 aggregation. Worms whose srh-2 gene has been knocked out form irregularly shaped aggregates. Our model suggests this phenotype may be explained by the mutant worms slowing their movement more quickly than the wild type.
Modeling the effects of dynamic range compression on signals in noise
Authors: Ryan M. Corey, Andrew C. Singer
Date: 2020-12-07 00:00:00

Hearing aids use dynamic range compression (DRC), a form of automatic gain control, to make quiet sounds louder and loud sounds quieter. Compression can improve listening comfort, but it can also cause distortion in noisy environments. It has been widely reported that DRC performs poorly in noise, but there has been little mathematical analysis of these distortion effects. This work introduces a mathematical model to study the behavior of DRC in noise. Using statistical assumptions about the signal envelopes, we define an effective compression function that models the compression applied to one signal in the presence of another. This framework is used to prove results about DRC that have been previously observed experimentally: that when DRC is applied to a mixture of signals, uncorrelated signal envelopes become negatively correlated; that the effective compression applied to each sound in a mixture is weaker than it would have been for the signal alone; and that compression can reduce the long-term signal-to-noise ratio in certain conditions. These theoretical results are supported by software experiments using recorded speech signals.
Inferring the effect of interventions on COVID-19 transmission networks
Authors: Simon Syga, Diana David-Rus, Yannik Schälte, Michael Meyer-Hermann, Haralampos Hatzikirou, Andreas Deutsch
Date: 2020-12-07 00:00:00
Tasks: Clustering

Countries around the world implement nonpharmaceutical interventions (NPIs) to mitigate the spread of COVID-19. Design of efficient NPIs requires identification of the structure of the disease transmission network. We here identify the key parameters of the COVID-19 transmission network for time periods before, during, and after the application of strict NPIs for the first wave of COVID-19 infections in Germany combining Bayesian parameter inference with an agent-based epidemiological model. We assume a Watts-Strogatz small-world network which allows to distinguish contacts within clustered cliques and unclustered, random contacts in the population, which have been shown to be crucial in sustaining the epidemic. In contrast to other works, which use coarse-grained network structures from anonymized data, like cell phone data, we consider the contacts of individual agents explicitly. We show that NPIs drastically reduced random contacts in the transmission network, increased network clustering, and resulted in a change from an exponential to a constant regime of newcases. In this regime, the disease spreads like a wave with a finite wave speed that depends on the number of contacts in a nonlinear fashion, which we can predict by mean field theory. Our analysis indicates that besides the well-known transitionbetween exponential increase and exponential decrease in the number of new cases, NPIs can induce a transition to another, previously unappreciated regime of constant new cases.
The Testing Multiplier: Fear vs Containment
Authors: Francesco Furno
Date: 2020-12-07 00:00:00

I study the economic effects of testing during the outbreak of a novel disease. I propose a model where testing permits isolation of the infected and provides agents with information about the prevalence and lethality of the disease. Additional testing reduces the perceived lethality of the disease, but might increase the perceived risk of infection. As a result, more testing could increase the perceived risk of dying from the disease - i.e. "stoke fear" - and cause a fall in economic activity, despite improving health outcomes. Two main insights emerge. First, increased testing is beneficial to the economy and pays for itself if performed at a sufficiently large scale, but not necessarily otherwise. Second, heterogeneous risk perceptions across age-groups can have important aggregate consequences. For a SARS-CoV-2 calibration of the model, heterogeneous risk perceptions across young and old individuals mitigate GDP losses by 50% and reduce the death toll by 30% relative to a scenario in which all individuals have the same perceptions of risk.
Optimal Insurance to Minimize the Probability of Ruin: Inverse Survival Function Formulation
Authors: Bahman Angoshtari, Virginia R. Young
Date: 2020-12-07 00:00:00

We find the optimal indemnity to minimize the probability of ruin when premium is calculated according to the distortion premium principle with a proportional risk load, and admissible indemnities are such that both the indemnity and retention are non-decreasing functions of the underlying loss. We reformulate the problem with the inverse survival function as the control variable and show that deductible insurance with maximum limit is optimal. Our main contribution is in solving this problem via the inverse survival function.
Stability of discrete-time feed-forward neural networks in NARX configuration
Authors: Fabio Bonassi, Marcello Farina, Riccardo Scattolini
Date: 2020-12-07 00:00:00

The idea of using Feed-Forward Neural Networks (FFNNs) as regression functions for Nonlinear AutoRegressive eXogenous (NARX) models, leading to models herein named Neural NARXs (NNARXs), has been quite popular in the early days of machine learning applied to nonlinear system identification, owing to their simple structure and ease of application to control design. Nonetheless, few theoretical results are available concerning the stability properties of these models. In this paper we address this problem, providing a sufficient condition under which NNARX models are guaranteed to enjoy the Input-to-State Stability (ISS) and the Incremental Input-to-State Stability ({\delta}ISS) properties. This condition, which is an inequality on the weights of the underlying FFNN, can be enforced during the training procedure to ensure the stability of the model. The proposed model, along with this stability condition, are tested on the pH neutralization process benchmark, showing satisfactory results.
Data-driven Model Predictive Control Method for DFIG-based Wind Farm to Provide Primary Frequency Regulation Service
Authors: Zizhen Guo, Wenchuan Wu
Date: 2020-12-07 00:00:00
Tasks: Dimensionality Reduction, Model Predictive Control

As wind power penetration increases, the wind farms are required by newly released grid codes to provide frequency regulation service. The most critical challenge is how to formulate the dynamic model of wind farm for dynamic control, since it is essentially is nonlinear and there are huge amount of parameters to be maintained frequently. This paper proposes a data-driven model predictive control (data-driven MPC) method to make wind farms participate primary frequency regulation. In this method,a specialized dynamic mode decomposition (SDMD) algorithm is developed, which can linearly approximate the dynamics of wind farm from measurements based on Koopman operator theory.Compared with the existing extended dynamic mode decomposition (EDMD) method,this tailored SDMD has two advantages: 1) fully capturing the nonlinear transients of wind turbine dynamics with good accuracy under a wide range of working conditions; 2) much less computational burden with model dimensionality reduction. Based on the recursively updated linear dynamic model, a model predictive control solution is implemented. The simulation results show this model-free solution can dynamically optimize wind turbine generators' active power to track the frequency response requirement from system operator and minimize the rotor speed distortion.
An Adaptive Anaphylaxis Detection and Emergency Response System
Authors: Gopabandhu Hota, Abhilash Nandy, Kshitiz Goel, Dishank Yadav, Saumo Pal, Ankush Roy
Date: 2019-08-05 00:00:00
Tasks: Anomaly Detection

Allergic Reactions can range from mild rashes to severe conditions, sometimes even leading to anaphylaxis and sudden death. Lack of sufficient prior patient data and a need of physician's immediate supervision calls for a solution which can be deployed at large to prevent the sudden death occurring due to anaphylactic shocks and further collect data to enable fast detection in future situations. This paper describes an integrated ecosystem comprising of several on-body patient devices connected to a central server with a doctor at one of the client nodes. An on-body device consists of physiological signal acquiring sensors, abnormality detector, and smart-phone for uploading the anomalous data to a server for further classification. Gathering anomalous data from the patients, the cloud processes them through a binary adversarial classifier based on physician's annotation of anaphylaxis occurrence. The adversarial classifier has been incorporated to tackle data insufficiency because of its faster convergence.
The genomic consequences of hybridization
Authors: Benjamin M Moran, Cheyenne Payne, Quinn Langdon, Daniel L Powell, Yaniv Brandvain, Molly Schumer
Date: 2020-12-07 00:00:00

In the past decade, advances in genome sequencing have allowed researchers to uncover the history of hybridization in diverse groups of species, including our own. Although the field has made impressive progress in documenting the extent of natural hybridization, both historical and recent, there are still many unanswered questions about its genetic and evolutionary consequences. Recent work has suggested that the outcomes of hybridization in the genome may be in part predictable, but many open questions about the nature of selection on hybrids and the biological variables that shape such selection have hampered progress in this area. We discuss what is known about the mechanisms that drive changes in ancestry in the genome after hybridization, highlight major unresolved questions, and discuss their implications for the predictability of genome evolution after hybridization.
Dynamic Anchor Learning for Arbitrary-Oriented Object Detection
Authors: Qi Ming, Zhiqiang Zhou, Lingjuan Miao, Hongwei Zhang, Linhao Li
Date: 2020-12-08 00:00:00
Tasks: Multi-Oriented Scene Text Detection, Object, object-detection, Object Detection In Aerial Images, Oriented Object Detection, regression

Arbitrary-oriented objects widely appear in natural scenes, aerial photographs, remote sensing images, etc., thus arbitrary-oriented object detection has received considerable attention. Many current rotation detectors use plenty of anchors with different orientations to achieve spatial alignment with ground truth boxes, then Intersection-over-Union (IoU) is applied to sample the positive and negative candidates for training. However, we observe that the selected positive anchors cannot always ensure accurate detections after regression, while some negative samples can achieve accurate localization. It indicates that the quality assessment of anchors through IoU is not appropriate, and this further lead to inconsistency between classification confidence and localization accuracy. In this paper, we propose a dynamic anchor learning (DAL) method, which utilizes the newly defined matching degree to comprehensively evaluate the localization potential of the anchors and carry out a more efficient label assignment process. In this way, the detector can dynamically select high-quality anchors to achieve accurate object detection, and the divergence between classification and regression will be alleviated. With the newly introduced DAL, we achieve superior detection performance for arbitrary-oriented objects with only a few horizontal preset anchors. Experimental results on three remote sensing datasets HRSC2016, DOTA, UCAS-AOD as well as a scene text dataset ICDAR 2015 show that our method achieves substantial improvement compared with the baseline model. Besides, our approach is also universal for object detection using horizontal bound box. The code and models are available at https://github.com/ming71/DAL.
Evaluating Explainable Methods for Predictive Process Analytics: A Functionally-Grounded Approach
Authors: Mythreyi Velmurugan, Chun Ouyang, Catarina Moreira, Renuka Sindhgatta
Date: 2020-12-08 00:00:00
Tasks: BIG-bench Machine Learning, Feature Importance, Predictive Process Monitoring

Predictive process analytics focuses on predicting the future states of running instances of a business process. While advanced machine learning techniques have been used to increase accuracy of predictions, the resulting predictive models lack transparency. Current explainable machine learning methods, such as LIME and SHAP, can be used to interpret black box models. However, it is unclear how fit for purpose these methods are in explaining process predictive models. In this paper, we draw on evaluation measures used in the field of explainable AI and propose functionally-grounded evaluation metrics for assessing explainable methods in predictive process analytics. We apply the proposed metrics to evaluate the performance of LIME and SHAP in interpreting process predictive models built on XGBoost, which has been shown to be relatively accurate in process predictions. We conduct the evaluation using three open source, real-world event logs and analyse the evaluation results to derive insights. The research contributes to understanding the trustworthiness of explainable methods for predictive process analytics as a fundamental and key step towards human user-oriented evaluation.
The Architectural Implications of Distributed Reinforcement Learning on CPU-GPU Systems
Authors: Ahmet Inci, Evgeny Bolotin, Yaosheng Fu, Gal Dalal, Shie Mannor, David Nellans, Diana Marculescu
Date: 2020-12-08 00:00:00
Tasks: CPU, Deep Reinforcement Learning, GPU, reinforcement-learning, Reinforcement Learning (RL)

With deep reinforcement learning (RL) methods achieving results that exceed human capabilities in games, robotics, and simulated environments, continued scaling of RL training is crucial to its deployment in solving complex real-world problems. However, improving the performance scalability and power efficiency of RL training through understanding the architectural implications of CPU-GPU systems remains an open problem. In this work we investigate and improve the performance and power efficiency of distributed RL training on CPU-GPU systems by approaching the problem not solely from the GPU microarchitecture perspective but following a holistic system-level analysis approach. We quantify the overall hardware utilization on a state-of-the-art distributed RL training framework and empirically identify the bottlenecks caused by GPU microarchitectural, algorithmic, and system-level design choices. We show that the GPU microarchitecture itself is well-balanced for state-of-the-art RL frameworks, but further investigation reveals that the number of actors running the environment interactions and the amount of hardware resources available to them are the primary performance and power efficiency limiters. To this end, we introduce a new system design metric, CPU/GPU ratio, and show how to find the optimal balance between CPU and GPU resources when designing scalable and efficient CPU-GPU systems for RL training.
Robustness of Accuracy Metric and its Inspirations in Learning with Noisy Labels
Authors: Pengfei Chen, Junjie Ye, Guangyong Chen, Jingwei Zhao, Pheng-Ann Heng
Date: 2020-12-08 00:00:00
Tasks: Learning with noisy labels, Model Selection, Multi-class Classification

For multi-class classification under class-conditional label noise, we prove that the accuracy metric itself can be robust. We concretize this finding's inspiration in two essential aspects: training and validation, with which we address critical issues in learning with noisy labels. For training, we show that maximizing training accuracy on sufficiently many noisy samples yields an approximately optimal classifier. For validation, we prove that a noisy validation set is reliable, addressing the critical demand of model selection in scenarios like hyperparameter-tuning and early stopping. Previously, model selection using noisy validation samples has not been theoretically justified. We verify our theoretical results and additional claims with extensive experiments. We show characterizations of models trained with noisy labels, motivated by our theoretical results, and verify the utility of a noisy validation set by showing the impressive performance of a framework termed noisy best teacher and student (NTS). Our code is released.
Sparse encoding for more-interpretable feature-selecting representations in probabilistic matrix factorization
Authors: Joshua C. Chang, Patrick Fletcher, Jungmin Han, Ted L. Chang, Shashaank Vattikuti, Bart Desmet, Ayah Zirikly, Carson C. Chow
Date: 2020-12-08 00:00:00
Proceeding: ICLR 2021 1
Tasks: Clustering, Decoder, Dimensionality Reduction, feature selection

Dimensionality reduction methods for count data are critical to a wide range of applications in medical informatics and other fields where model interpretability is paramount. For such data, hierarchical Poisson matrix factorization (HPF) and other sparse probabilistic non-negative matrix factorization (NMF) methods are considered to be interpretable generative models. They consist of sparse transformations for decoding their learned representations into predictions. However, sparsity in representation decoding does not necessarily imply sparsity in the encoding of representations from the original data features. HPF is often incorrectly interpreted in the literature as if it possesses encoder sparsity. The distinction between decoder sparsity and encoder sparsity is subtle but important. Due to the lack of encoder sparsity, HPF does not possess the column-clustering property of classical NMF -- the factor loading matrix does not sufficiently define how each factor is formed from the original features. We address this deficiency by self-consistently enforcing encoder sparsity, using a generalized additive model (GAM), thereby allowing one to relate each representation coordinate to a subset of the original data features. In doing so, the method also gains the ability to perform feature selection. We demonstrate our method on simulated data and give an example of how encoder sparsity is of practical use in a concrete application of representing inpatient comorbidities in Medicare patients.
UnrealPerson: An Adaptive Pipeline towards Costless Person Re-identification
Authors: Tianyu Zhang, Lingxi Xie, Longhui Wei, Zijie Zhuang, Yongfei Zhang, Bo Li, Qi Tian
Date: 2020-12-08 00:00:00
Proceeding: CVPR 2021 1
Tasks: Domain Adaptation, Image Generation, Person Re-Identification

The main difficulty of person re-identification (ReID) lies in collecting annotated data and transferring the model across different domains. This paper presents UnrealPerson, a novel pipeline that makes full use of unreal image data to decrease the costs in both the training and deployment stages. Its fundamental part is a system that can generate synthesized images of high-quality and from controllable distributions. Instance-level annotation goes with the synthesized data and is almost free. We point out some details in image synthesis that largely impact the data quality. With 3,000 IDs and 120,000 instances, our method achieves a 38.5% rank-1 accuracy when being directly transferred to MSMT17. It almost doubles the former record using synthesized data and even surpasses previous direct transfer records using real data. This offers a good basis for unsupervised domain adaption, where our pre-trained model is easily plugged into the state-of-the-art algorithms towards higher accuracy. In addition, the data distribution can be flexibly adjusted to fit some corner ReID scenarios, which widens the application of our pipeline. We will publish our data synthesis toolkit and synthesized data in https://github.com/FlyHighest/UnrealPerson.
Enhanced spatio-temporal electric load forecasts using less data with active deep learning
Authors: Arsam Aryandoust, Anthony Patt, Stefan Pfenninger
Date: 2020-12-08 00:00:00
Tasks: Active Learning, BIG-bench Machine Learning, Deep Learning, Informativeness, Spatio-Temporal Forecasting

An effective way to oppose global warming and mitigate climate change is to electrify our energy sectors and supply their electric power from renewable wind and solar. Spatio-temporal predictions of electric load become increasingly important for planning this transition, while deep learning prediction models provide increasingly accurate predictions for it. The data used for training deep learning models, however, is usually collected at random using a passive learning approach. This naturally results in a large demand for data and associated costs for sensors like smart meters, posing a large barrier for electric utilities in decarbonizing their grids. Here, we test active learning where we leverage additional computation for collecting a more informative subset of data. We show how electric utilities can apply active learning to better distribute smart meters and collect their data for more accurate predictions of load with about half the data compared to when applying passive learning.