pwc-archive/papers-with-abstracts huggingface dataset:
Offline Evaluation for Reinforcement Learning-based Recommendation: A Critical Issue and Some Alternatives
Authors: Romain Deffayet, Thibaut Thonet, Jean-Michel Renders, Maarten de Rijke
Date: 2023-01-03 00:00:00
Tasks: Offline RL, Recommendation Systems, reinforcement-learning, Reinforcement Learning, Reinforcement Learning (RL)

In this paper, we argue that the paradigm commonly adopted for offline evaluation of sequential recommender systems is unsuitable for evaluating reinforcement learning-based recommenders. We find that most of the existing offline evaluation practices for reinforcement learning-based recommendation are based on a next-item prediction protocol, and detail three shortcomings of such an evaluation protocol. Notably, it cannot reflect the potential benefits that reinforcement learning (RL) is expected to bring while it hides critical deficiencies of certain offline RL agents. Our suggestions for alternative ways to evaluate RL-based recommender systems aim to shed light on the existing possibilities and inspire future research on reliable evaluation protocols.
Causal Inference in Recommender Systems: A Survey of Strategies for Bias Mitigation, Explanation, and Generalization
Authors: Yaochen Zhu, Jing Ma, Jundong Li
Date: 2023-01-03 00:00:00
Tasks: Causal Inference, Recommendation Systems

In the era of information overload, recommender systems (RSs) have become an indispensable part of online service platforms. Traditional RSs estimate user interests and predict their future behaviors by utilizing correlations in the observational historical activities, their profiles, and the content of interacted items. However, since the inherent causal reasons that lead to the observed users' behaviors are not considered, multiple types of biases could exist in the generated recommendations. In addition, the causal motives that drive user activities are usually entangled in these RSs, where the explainability and generalization abilities of recommendations cannot be guaranteed. To address these drawbacks, recent years have witnessed an upsurge of interest in enhancing traditional RSs with causal inference techniques. In this survey, we provide a systematic overview of causal RSs and help readers gain a comprehensive understanding of this promising area. We start with the basic concepts of traditional RSs and their limitations due to the lack of causal reasoning ability. We then discuss how different causal inference techniques can be introduced to address these challenges, with an emphasis on debiasing, explainability promotion, and generalization improvement. Furthermore, we thoroughly analyze various evaluation strategies for causal RSs, focusing especially on how to reliably estimate their performance with biased data if the causal effects of interests are unavailable. Finally, we provide insights into potential directions for future causal RS research.
Understanding the main failure scenarios of subsea blowout preventers systems: An approach through Latent Semantic Analysis
Authors: Gustavo Jorge Martins de Aguiar, Ramon Baptista Narcizo, Rodolfo Cardoso, Iara Tammela, Edwin Benito Mitacc Meza, Danilo Colombo, Luiz Antônio de Oliveira Chaves, Jamile Eleutério Delesposte
Date: 2023-01-02 00:00:00

The blowout preventer (BOP) system is one of the most important well safety barriers during the drilling phase because it can prevent the development of blowout events. This paper investigates BOP system's main failures using an LSA-based methodology. A total of 1312 failure records from companies worldwide were collected from the International Association of Drilling Contractors' RAPID-S53 database. The database contains recordings of halted drilling operations due to BOP system's failures and component's function deviations. The main failure scenarios of the components annular preventer, shear rams preventer, compensated chamber solenoid valve, and hydraulic regulators were identified using the proposed methodology. The scenarios contained valuable information about corrective maintenance procedures, such as frequently observed failure modes, detection methods used, suspected causes, and corrective actions. The findings highlighted that the major failures of the components under consideration were leakages caused by damaged elastomeric seals. The majority of the failures were detected during function and pressure tests with the BOP system in the rig. This study provides an alternative safety analysis that contributes to understanding blowout preventer system's critical component failures by applying a methodology based on a well-established text mining technique and analyzing failure records from an international database.
Encrypted Data-driven Predictive Cloud Control with Disturbance Observer
Authors: Qiwen Li, Runze Gao, Yuanqing Xia
Date: 2023-01-01 00:00:00
Tasks: Privacy Preserving

In data-driven predictive cloud control tasks, the privacy of data stored and used in cloud services could be leaked to malicious attackers or curious eavesdroppers. Homomorphic encryption technique could be used to protect data privacy while allowing computation. However, extra errors are introduced by the homomorphic encryption extension to ensure the privacy-preserving properties, and the real number truncation also brings uncertainty. Also, process and measure noise existed in system input and output may bring disturbance. In this work, a data-driven predictive cloud controller is developed based on homomorphic encryption to protect the cloud data privacy. Besides, a disturbance observer is introduced to estimate and compensate the encrypted control signal sequence computed in the cloud. The privacy of data is guaranteed by encryption and experiment results show the effect of our cloud-edge cooperative design.
Democratization of Retail Trading: Can Reddit's WallStreetBets Outperform Investment Bank Analysts?
Authors: Tolga Buz, Gerard de Melo
Date: 2022-12-31 00:00:00

The recent hype around Reddit's WallStreetBets (WSB) community has inspired research on its impact on our economy and society. Still, one important question remains: Can WSB's community of anonymous contributors actually provide valuable investment advice and possibly even outperform top financial institutions? We present a data-driven empirical study of investment recommendations of WSB in comparison to recommendations made by leading investment banks, based on more than 1.6 million WSB posts published since 2018. %enriched with stock market data. To this end, we extract and evaluate investment recommendations from WSB's raw text for all S&P 500 stocks and compare their performance to more than 16,000 analyst recommendations from the largest investment banks. While not all WSB recommendations prove profitable, our results show that they achieve average returns that compete with the best banks and outperform them in certain cases. Furthermore, the WSB community has been better than almost all investment banks at detecting top-performing stocks. We conclude that WSB may indeed constitute a freely accessible, valuable source of investment advice.
Inferring multiple consensus trees and supertrees using clustering: a review
Authors: Vladimir Makarenkov, Gayane S. Barseghyan, Nadia Tahiri
Date: 2023-01-01 00:00:00
Tasks: Clustering

Phylogenetic trees (i.e. evolutionary trees, additive trees or X-trees) play a key role in the processes of modeling and representing species evolution. Genome evolution of a given group of species is usually modeled by a species phylogenetic tree that represents the main patterns of vertical descent. However, the evolution of each gene is unique. It can be represented by its own gene tree which can differ substantially from a general species tree representation. Consensus trees and supertrees have been widely used in evolutionary studies to combine phylogenetic information contained in individual gene trees. Nevertheless, if the available gene trees are quite different from each other, then the resulting consensus tree or supertree can either include many unresolved subtrees corresponding to internal nodes of high degree or can simply be a star tree. This may happen if the available gene trees have been affected by different reticulate evolutionary events, such as horizontal gene transfer, hybridization or genetic recombination. Thus, the problem of inferring multiple alternative consensus trees or supertrees, using clustering, becomes relevant since it allows one to regroup in different clusters gene trees having similar evolutionary patterns (e.g. gene trees representing genes that have undergone the same horizontal gene transfer or recombination events). We critically review recent advances and methods in the field of phylogenetic tree clustering, discuss the methods' mathematical properties, and describe the main advantages and limitations of multiple consensus tree and supertree approaches. In the application section, we show how the multiple supertree clustering approach can be used to cluster aaRS gene trees according to their evolutionary patterns.
Understanding EEG signals for subject-wise Definition of Armoni Activities
Authors: Kislay Raj, Aditya Singh, Abhishek Mandal, Teerath Kumar, Arunabha M. Roy
Date: 2023-01-03 00:00:00
Tasks: EEG, Electroencephalogram (EEG)

In a growing world of technology, psychological disorders became a challenge to be solved. The methods used for cognitive stimulation are very conventional and based on one-way communication, which only relies on the material or method used for training of an individual. It doesn't use any kind of feedback from the individual to analyze the progress of the training process. We have proposed a closed-loop methodology to improve the cognitive state of a person with ID (Intellectual disability). We have used a platform named 'Armoni', for providing training to the intellectually disabled individuals. The learning is performed in a closed-loop by using feedback in the form of change in affective state. For feedback to the Armoni, an EEG (Electroencephalograph) headband is used. All the changes in EEG are observed and classified against the change in the mean and standard deviation value of all frequency bands of signal. This comparison is being helpful in defining every activity with respect to change in brain signals. In this paper, we have discussed the process of treatment of EEG signal and its definition against the different activities of Armoni. We have tested it on 6 different systems with different age groups and cognitive levels.
Energy Efficient Design of Extreme MIMO
Authors: Stefan Wesemann, Jinfeng Du, Harish Viswanathan
Date: 2023-01-03 00:00:00

Ever since the invention of Bell Laboratories Layer Space-Time (BLAST) in mid 1990s, the focus of MIMO research and development has been largely on pushing the limit of spectral efficiency. While massive MIMO technologies laid the foundation of high spectrum efficiency in 5G and beyond, the challenge remains in improving energy efficiency given the increasing complexity of the associated radio systems. With the substantial negative implications of climate change looming ever closer, minimizing energy use is a key dimension of achieving sustainability and is of paramount importance for any future technology. Thus, every aspect of future extreme MIMO system design, implementation, and operation will be scrutinized to maximize energy efficiency. An analysis of the massive MIMO 5G radio energy consumption at different loads leads to qualitative energy efficiency design goals for emerging extreme MIMO systems. Following this, we focus on novel operational and component technology innovations to minimize energy consumption.
Frequency-Domain Detection for Molecular Communications
Authors: Meltem Civas, Ali Abdali, Murat Kuscu, Ozgur B. Akan
Date: 2023-01-03 00:00:00

Molecular Communications (MC) is a bio-inspired communication paradigm which uses molecules as information carriers, thereby requiring unconventional transmitter/receiver architectures and modulation/detection techniques. Practical MC receivers (MC-Rxs) can be implemented based on field-effect transistor biosensor (bioFET) architectures, where surface receptors reversibly react with ligands, whose concentration encodes the information. The time-varying concentration of ligand-bound receptors is then translated into electrical signals via field-effect, which is used to decode the transmitted information. However, ligand-receptor interactions do not provide an ideal molecular selectivity, as similar types of ligands, i.e., interferers, co-existing in the MC channel can interact with the same type of receptors, resulting in cross-talk. Overcoming this molecular cross-talk with time-domain samples of the Rx's electrical output is not always attainable, especially when Rx has no knowledge of the interferer statistics or it operates near saturation. In this study, we propose a frequency-domain detection (FDD) technique for bioFET-based MC-Rxs, which exploits the difference in binding reaction rates of different types of ligands, reflected to the noise spectrum of the ligand-receptor binding fluctuations. We analytically derive the bit error probability (BEP) of the FDD technique, and demonstrate its effectiveness in decoding transmitted concentration signals under stochastic molecular interference, in comparison to a widely-used time-domain detection (TDD) technique. The proposed FDD method can be applied to any biosensor-based MC-Rxs, which employ receptor molecules as the channel-Rx interface.
Explicitly Solvable Continuous-time Inference for Partially Observed Markov Processes
Authors: Daniel Chen, Alexander G. Strang, Andrew W. Eckford, Peter J. Thomas
Date: 2023-01-02 00:00:00
Tasks: Time Series, Time Series Analysis

Many natural and engineered systems can be modeled as discrete state Markov processes. Often, only a subset of states are directly observable. Inferring the conditional probability that a system occupies a particular hidden state, given the partial observation, is a problem with broad application. In this paper, we introduce a continuous-time formulation of the sum-product algorithm, which is a well-known discrete-time method for finding the hidden states' conditional probabilities, given a set of finite, discrete-time observations. From our new formulation, we can explicitly solve for the conditional probability of occupying any state, given the transition rates and observations within a finite time window. We apply our algorithm to a realistic model of the cystic fibrosis transmembrane conductance regulator (CFTR) protein for exact inference of the conditional occupancy probability, given a finite time series of partial observations.
Performance Analysis and Enhancement of Beamforming Training in 802.11ad
Authors: Wen Wu, Nan Cheng, Ning Zhang, Peng Yang, Khalid Aldubaikhy, Xuemin, Shen
Date: 2023-01-02 00:00:00

Beamforming (BF) training is crucial to establishing reliable millimeter-wave communication connections between stations (STAs) and an access point. In IEEE 802.11ad BF training protocol, all STAs contend for limited BF training opportunities, i.e., associated BF training (A-BFT) slots, which results in severe collisions and significant BF training latency, especially in dense user scenarios. In this paper, we first develop an analytical model to evaluate the BF training protocol performance. Our analytical model accounts for various protocol components, including user density, the number of A-BFT slots, and protocol parameters, i.e., retry limit and contention window size. We then derive the average successful BF training probability, the BF training efficiency and latency. Since the derived BF training efficiency is an implicit function, to reveal the relationship between system parameters and BF training performance, we also derive an approximate expression of BF training efficiency. Theoretical analysis indicates that the BF training efficiency degrades drastically in dense user scenarios. To address this issue, we propose an enhancement scheme which adaptively adjusts the protocol parameters in tune with user density, to improve the BF training performance in dense user scenarios. Extensive simulations are carried out to validate the accuracy of the developed analytical model. In addition, simulation results show that the proposed enhancement scheme can improve the BF training efficiency by 35% in dense user scenarios.
Beef up mmWave Dense Cellular Networks with D2D-Assisted Cooperative Edge Caching
Authors: Wen Wu, Ning Zhang, Nan Cheng, Yujie Tang, Khalid Aldubaikhy, Xuemin, Shen
Date: 2023-01-02 00:00:00
Tasks: Retrieval

Edge caching is emerging as the most promising solution to reduce the content retrieval delay and relieve the huge burden on the backhaul links in the ultra-dense networks by proactive caching popular contents in the small base station (SBS). However, constraint cache resource of individual SBSs significantly throttles the performance of edge caching. In this paper, we propose a device-to-device (D2D) assisted cooperative edge caching (DCEC) policy for millimeter (mmWave) dense networks, which cooperatively utilizes the cache resource of users and SBSs in proximity. In the proposed DCEC policy, a content can be cached in either users' devices or SBSs according to the content popularity, and a user can retrieve the requested content from neighboring users via D2D links or the neighboring SBSs via cellular links to efficiently exploit the cache diversity. Unlike existing cooperative caching policies in the lower frequency bands that require complex interference management techniques to suppress interference, we take advantage of directional antenna in mmWave systems to ensure high transmission rate whereas mitigating interference footprint. Taking the practical directional antenna model and the network density into consideration, we derive closed-form expressions of the backhaul offloading performance and content retrieval delay based on the stochastic information of network topology. In addition, analytical results indicate that, with the increase of the network density, the content retrieval delay via D2D links increases significantly while that via cellular links increases slightly. Comprehensive simulations validate our theoretical analysis and demonstrate that the proposed policy can achieve higher performance in offloading the backhaul traffic and reducing the content retrieval delay compared with the state-of-the-art most popular caching (MPC) policy.
Design of a Multi-User Wireless Powered Communication System Employing Either Active IRS or AF Relay
Authors: Omid Rezaei, Maryam Masjedi, Ali Kanaani, Mohammad Mahdi Naghsh, Saeed Gazor, Mohammad Mahdi Nayebi
Date: 2022-12-31 00:00:00

In this paper, we optimize a Wireless Powered Communication (WPC) system including multiple pair of users, where transmitters employ single-antenna to transmit their information and power to their receivers with the help of one multiple-antennas Amplify-and-Forward (AF) relay or an active Intelligent Reflecting Surface (IRS). We propose a joint Time Switching (TS) scheme in which transmitters, receivers, and the relay/IRS are either in their energy or information transmission/reception modes. The transmitted multi-carrier unmodulated and modulated waveforms are used for Energy Harvesting (EH) and Information Decoding (ID) modes, respectively. In order to design an optimal fair system, we maximize the minimum rate of all pairs for both relay and IRS systems through a unified framework. This framework allows us to simultaneously design energy waveforms, find optimal relay/IRS amplification/reflection matrices, allocate powers for information waveforms, and allocate time durations for various phases. In addition, we take into account the non-linearity of the EH circuits in our problem. This problem turns out to be non-convex. Thus, we propose an iterative algorithm by using the Minorization-Maximization (MM) technique, which quickly converges to the optimal solution. Numerical examples show that the proposed method improves the performance of the multi-pair WPC relay/IRS system under various setups.
Designing organizations for bottom-up task allocation: The role of incentives
Authors: Stephan Leitner
Date: 2023-01-01 00:00:00

In recent years, various decentralized organizational forms have emerged, posing a challenge for organizational design. Some design elements, such as task allocation, become emergent properties that cannot be fully controlled from the top down. The central question that arises in this context is: How can bottom-up task allocation be guided towards an effective organizational structure? To address this question, this paper presents a novel agent-based model of an organization that features bottom-up task allocation that can be motivated by either long-term or short-term orientation on the agents' side. The model also includes an incentive mechanism to guide the bottom-up task allocation process and create incentives that range from altruistic to individualistic. Our analysis shows that when bottom-up task allocation is driven by short-term orientation and aligned with the incentive mechanisms, it leads to improved organizational performance that surpasses that of traditionally designed organizations. Additionally, we find that the presence of altruistic incentive mechanisms within the organization reduces the importance of mirroring in task allocation.
Wealth Redistribution and Mutual Aid: Comparison using Equivalent/Nonequivalent Exchange Models of Econophysics
Authors: Takeshi Kato
Date: 2022-12-31 00:00:00

Given the wealth inequality worldwide, there is an urgent need to identify the mode of wealth exchange through which it arises. To address the research gap regarding models that combine equivalent exchange and redistribution, this study compares an equivalent market exchange with redistribution based on power centers and a nonequivalent exchange with mutual aid using the Polanyi, Graeber, and Karatani modes of exchange. Two new exchange models based on multi-agent interactions are reconstructed following an econophysics approach for evaluating the Gini index (inequality) and total exchange (economic flow). Exchange simulations indicate that the evaluation parameter of the total exchange divided by the Gini index can be expressed by the same saturated curvilinear approximate equation using the wealth transfer rate and time period of redistribution and the surplus contribution rate of the wealthy and the saving rate. However, considering the coercion of taxes and its associated costs and independence based on the morality of mutual aid, a nonequivalent exchange without return obligation is preferred. This is oriented toward Graeber's baseline communism and Karatani's mode of exchange D, with implications for alternatives to the capitalist economy.