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1. Assessment of the Elliptic Blending Reynolds Stress Model for a Rotating Turbulent Pipe Flow Using New DNS Data

   https://doi.org/10.2514/6.2019-2966  

   Ashton, Neil; Davis, Jefferson; Brehm, Christoph (June 2019, AIAA Aviation Forum and Exposition)

   New direct numerical simulation data of a fully-developed axially rotating pipe at Re = 5300 and Re = 19, 000 is used to examine the performance of the second-moment closure elliptic blending Reynolds stress model for a range of rotation rates from N=0 to N=3. In agreement with previous studies (using alternative second-moment closure models), the turbulence suppression observed by the DNS is over-predicted. This over-prediction is greatest at Re = 5, 300 and most noticeable in the poor prediction of the ut wt turbulent shear-stress component. At N=3 the flow is completely relaminarized in contrast to the DNS that is only partly relaminarized. The accuracy of the second-moment closure model is superior to the two-equation k − ω SST model which predicts pure solid-body rotation, however, both are equally poor at the highest rotation rates. The accuracy of each model is also assessed for the initial portion of a rotating pipe where in contrast to the fully- developed rotating pipe flow the turbulent suppression is under-predicted compared to the DNS. It is clear that greater work is required to understand the root cause of the poor prediction by these second-moment closure models and further DNS and experimental work is underway to assist this effort. 

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2. Benchmark of Bitrate Adaptation in Video Streaming

   https://doi.org/10.1145/3468063  

   Chen, Jessica; Milner, Henry; Stoica, Ion; Zhan, Jibin (December 2021, Journal of Data and Information Quality)

   The HTTP adaptive streaming technique opened the door to cope with the fluctuating network conditions during the streaming process by dynamically adjusting the volume of the future chunks to be downloaded. The bitrate selection in this adjustment inevitably involves the task of predicting the future throughput of a video session, owing to which various heuristic solutions have been explored. The ultimate goal of the present work is to explore the theoretical upper bounds of the QoE that any ABR algorithm can possibly reach, therefore providing an essential step to benchmarking the performance evaluation of ABR algorithms. In our setting, the QoE is defined in terms of a linear combination of the average perceptual quality and the buffering ratio. The optimization problem is proven to be NP-hard when the perceptual quality is defined by chunk size and conditions are given under which the problem becomes polynomially solvable. Enriched by a global lower bound, a pseudo-polynomial time algorithm along the dynamic programming approach is presented. When the minimum buffering is given higher priority over higher perceptual quality, the problem is shown to be also NP-hard, and the above algorithm is simplified and enhanced by a sequence of lower bounds on the completion time of chunk downloading, which, according to our experiment, brings a 36.0% performance improvement in terms of computation time. To handle large amounts of data more efficiently, a polynomial-time algorithm is also introduced to approximate the optimal values when minimum buffering is prioritized. Besides its performance guarantee, this algorithm is shown to reach 99.938% close to the optimal results, while taking only 0.024% of the computation time compared to the exact algorithm in dynamic programming. 

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3. Demo Abstract: An Ultra-Low-Power Custom Integrated Circuit based Sound-Source Localization System

   de Godoy, Daniel; Xia, Stephen; Fernandez, Wendy; Jiang, Xiaofan; Kinget, Peter R (April 2018, IEEE/ACM International Conference on Internet-of-Things Design and Implementation)

   The aim of this demo is to explore the implementation of an ultra-low-power analog-to-feature ASIC to an IoT embedded system. The custom integrated circuit, designed to optimize the power consumption of a traditional sound-source localization systems, is capable of extracting the time-difference of arrival (TDoA) between 4 microphones consuming only 78.2nW. An end-to-end embedded system is presented; a microphone array is connected to the ASIC that converts the TDoA to digital information and sends it to a host computer. A machine-learning algorithm, running in the host, is then used to detect the bearing of the sound-source. During the demonstration, the audience is able to verify the benefits and drawbacks of the custom integrated circuit solution, both in the perspective of the signal-processing performance of the ASIC, and the impact it introduces to the complexity of the system’s integration. 

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4. Application of tests for contagion in point processes to measles, Chlamydia, Lyme disease, and suicide

   https://doi.org/10.18103/mra.v12i9.5916  

   Schoenberg, Frederic (September 2024, Medical Research Archives)

   A recently proposed likelihood-ratio test for identifying causal triggering in point process data is applied to a variety of case counts of diseases of varying infectiousness. The test, suggested by McGovern et al. (2023), involves comparing the likelihood of a fitted Hawkes model to that of a fitted Poisson cluster model, and was shown using simulations to be powerful at discriminating between a process with causal triggering and a process where the clustering is merely due to spatial-temporal inhomogeneity. Here, the test is applied to data on measles, Chlamydia, and Lyme disease in the United States, to see if the test can discern between diseases that are highly contagious, moderately contagious, and not directly contagious from human to human. Measles is a highly contagious disease that spreads rapidly through populations, so it can potentially be modeled accurately using a Hawkes model. Chlamydia is a sexually transmitted disease that is not as highly contagious as measles since the level of contact needed for exposure is much higher than for measles. Lyme disease is non-contagious from human to human but cases tend to be highly clustered, as the disease is primarily spread through ticks, and this exposure is much more likely to happen during warmer weather. Further, the test is applied to data on adolescent suicides in the United States, in order to investigate the hypothesis that such suicides are an epidemic spread by social contagion. The results show that the test is able to measure the degree of contagion of a disease, and the results suggest that there is indeed a small but statistically significant element of contagion to youth suicides. 

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5. Optimal Scoring Rules for Multi-dimensional Effort

   Hartline, Jason; Shan, Liren; Li, Yingkai; Wu, Yifan (November 2023, Proceedings of Thirty Sixth Conference on Learning Theory)

   Neu, Gergely; Rosasco, Lorenzo (Ed.)

   This paper develops a framework for the design of scoring rules to optimally incentivize an agent to exert a multi-dimensional effort. This framework is a generalization to strategic agents of the classical knapsack problem (cf. Briest, Krysta, and Vocking, 2005; Singer, 2010) and it is foundational to applying algorithmic mechanism design to the classroom. The paper identifies two simple families of scoring rules that guarantee constant approximations to the optimal scoring rule. The truncated separate scoring rule is the sum of single dimensional scoring rules that is truncated to the bounded range of feasible scores. The threshold scoring rule gives the maximum score if reports exceed a threshold and zero otherwise. Approximate optimality of one or the other of these rules is similar to the bundling or selling separately result of Babaioff, Immorlica, Lucier, and Weinberg (2014). Finally, we show that the approximate optimality of the best of those two simple scoring rules is robust when the agent’s choice of effort is made sequentially. 

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