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1. w-HAR: An Activity Recognition Dataset and Framework Using Low-Power Wearable Devices

   https://doi.org/10.3390/s20185356  

   Bhat, Ganapati; Tran, Nicholas; Shill, Holly; Ogras, Umit Y. (September 2020, Sensors)

   null (Ed.)

   Human activity recognition (HAR) is growing in popularity due to its wide-ranging applications in patient rehabilitation and movement disorders. HAR approaches typically start with collecting sensor data for the activities under consideration and then develop algorithms using the dataset. As such, the success of algorithms for HAR depends on the availability and quality of datasets. Most of the existing work on HAR uses data from inertial sensors on wearable devices or smartphones to design HAR algorithms. However, inertial sensors exhibit high noise that makes it difficult to segment the data and classify the activities. Furthermore, existing approaches typically do not make their data available publicly, which makes it difficult or impossible to obtain comparisons of HAR approaches. To address these issues, we present wearable HAR (w-HAR) which contains labeled data of seven activities from 22 users. Our dataset’s unique aspect is the integration of data from inertial and wearable stretch sensors, thus providing two modalities of activity information. The wearable stretch sensor data allows us to create variable-length segment data and ensure that each segment contains a single activity. We also provide a HAR framework to use w-HAR to classify the activities. To this end, we first perform a design space exploration to choose a neural network architecture for activity classification. Then, we use two online learning algorithms to adapt the classifier to users whose data are not included at design time. Experiments on the w-HAR dataset show that our framework achieves 95% accuracy while the online learning algorithms improve the accuracy by as much as 40%. 

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2. Simulation for a Mems-Based CTRNN Ultra-Low Power Implementation of Human Activity Recognition

   https://doi.org/10.3389/fdgth.2021.731076  

   Emad-Ud-Din, Muhammad; Hasan, Mohammad H.; Jafari, Roozbeh; Pourkamali, Siavash; Alsaleem, Fadi (September 2021, Frontiers in Digital Health)

   This paper presents an energy-efficient classification framework that performs human activity recognition (HAR). Typically, HAR classification tasks require a computational platform that includes a processor and memory along with sensors and their interfaces, all of which consume significant power. The presented framework employs microelectromechanical systems (MEMS) based Continuous Time Recurrent Neural Network (CTRNN) to perform HAR tasks very efficiently. In a real physical implementation, we show that the MEMS-CTRNN nodes can perform computing while consuming power on a nano-watts scale compared to the micro-watts state-of-the-art hardware. We also confirm that this huge power reduction doesn't come at the expense of reduced performance by evaluating its accuracy to classify the highly cited human activity recognition dataset (HAPT). Our simulation results show that the HAR framework that consists of a training module, and a network of MEMS-based CTRNN nodes, provides HAR classification accuracy for the HAPT that is comparable to traditional CTRNN and other Recurrent Neural Network (RNN) implantations. For example, we show that the MEMS-based CTRNN model average accuracy for the worst-case scenario of not using pre-processing techniques, such as quantization, to classify 5 different activities is 77.94% compared to 78.48% using the traditional CTRNN. 

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3. HAR-CTGAN: A Mobile Sensor Data Generation Tool for Human Activity Recognition

   https://doi.org/10.1109/BigData55660.2022.10020848  

   DeOliveira, Joshua; Gerych, Walter; Koshkarova, Aruzhan; Rundensteiner, Elke; Agu, Emmanuel (December 2022, 2022 IEEE International Conference on Big Data (Big Data))

   Human activity recognition (HAR) is the process of using mobile sensor data to determine the physical activities performed by individuals. HAR is the backbone of many mobile healthcare applications, such as passive health monitoring systems, early diagnosing systems, and fall detection systems. Effective HAR models rely on deep learning architectures and big data in order to accurately classify activities. Unfortunately, HAR datasets are expensive to collect, are often mislabeled, and have large class imbalances. State-of-the-art approaches to address these challenges utilize Generative Adversarial Networks (GANs) for generating additional synthetic data along with their labels. Problematically, these HAR GANs only synthesize continuous features — features that are represented by real numbers — recorded from gyroscopes, accelerometers, and other sensors that produce continuous data. This is limiting since mobile sensor data commonly has discrete features that provide additional context such as device location and the time-of-day, which have been shown to substantially improve HAR classification. Hence, we studied Conditional Tabular Generative Adversarial Networks (CTGANs) for data generation to synthesize mobile sensor data containing both continuous and discrete features, a task never been done by state-of-the-art approaches. We show HAR-CTGANs generate data with greater realism resulting in allowing better downstream performance in HAR models, and when state-of-the-art models were modified with HAR-CTGAN characteristics, downstream performance also improves. 

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4. Poster: Comparative Study of Transformer Models on a Large Multivariate Time Series HAR Dataset

   Kwon, Hyungtaek; Xie, Zongxing; Liu, Mengjing; Ye, Fan (June 2024, IEEE/ACM international conference on Connected Health: Applications, Systems and Engineering Technologies (CHASE))

   In Activities of Daily Living (ADL) research, which has gained prominence due to the burgeoning aging population, the challenge of acquiring sufficient ground truth data for model training is a significant bottleneck. This obstacle necessitates a pivot towards unsupervised representation learning methodologies, which do not require many labeled datasets. The existing research focused on the tradeoff between the fully supervised model and the unsupervised pre-trained model and found that the unsupervised version outperformed in most cases. However, their investigation did not use large enough Human Activity Recognition (HAR) datasets, both datasets resulting in 3 dimensions. This poster extends the investigation by employing a large multivariate time series HAR dataset and experimenting with the models with different combinations of critical training parameters such as batch size and learning rate to observe the performance tradeoff. Our findings reveal that the pre-trained model is comparable to the fully supervised classification with a larger multivariate time series HAR dataset. This discovery underscores the potential of unsupervised representation learning in ADL extractions and highlights the importance of model configuration in optimizing performance. 

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5. Examining Power Use and the Privacy Paradox between Intention vs. Actual Use of Mobile Applications

   https://doi.org/10.1145/3481357.3481513  

   Namara, Moses; Anaraky, Reza Ghaiumy; Wisniewski, Pamela; Page, Xinru; Knijnenburg, Bart P. (October 2021, The 2021 European Symposium on Usable Security)

   The prevalence of smartphones in our society warrants more research on understanding the characteristics of users and their information privacy behaviors when using mobile apps. This paper investigates the antecedents and consequences of “power use” (i.e., the competence and desire to use technology to its fullest) in the context of informational privacy. In a study with 380 Android users, we examined how gender and users’ education level influence power use, how power use affects users’ intention to install apps and share information with them versus their actual privacy behaviors (i.e., based on the number of apps installed and the total number of “dangerous permission” requests granted to those apps). Our findings revealed an inconsistency in the effect of power use on users’ information privacy behaviors: While the intention to install apps and to share information with them increased with power use, the actual number of installed apps and dangerous permissions ultimately granted decreased with power use. In other words, although the self-reported intentions suggested the opposite, people who scored higher on the power use scale seemed to be more prudent about their informational privacy than people who scored lower on the power use scale. We discuss the implications of this inconsistency and make recommendations for reconciling smartphone users’ informational privacy intentions and behaviors. 

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