Test Time Embedding Normalization for Popularity Bias Mitigation

Popularity bias is a widespread problem in the field of recommender systems, where popular items tend to dominate recommendation results. In this work, we propose 'Test Time Embedding Normalization' as a simple yet effective strategy for mitigating popularity bias, which surpasses the performance of the previous mitigation approaches by a significant margin. Our approach utilizes the normalized item embedding during the inference stage to control the influence of embedding magnitude, which is highly correlated with item popularity. Through extensive experiments, we show that our method combined with the sampled softmax loss effectively reduces popularity bias compare to previous approaches for bias mitigation. We further investigate the relationship between user and item embeddings and find that the angular similarity between embeddings distinguishes preferable and non-preferable items regardless of their popularity. The analysis explains the mechanism behind the success of our approach in eliminating the impact of popularity bias. Our code is available at https://github.com/ml-postech/TTEN.Comment: 5 pages, CIKM 202

Item-based Variational Auto-encoder for Fair Music Recommendation

We present our solution for the EvalRS DataChallenge. The EvalRS DataChallenge aims to build a more realistic recommender system considering accuracy, fairness, and diversity in evaluation. Our proposed system is based on an ensemble between an item-based variational auto-encoder (VAE) and a Bayesian personalized ranking matrix factorization (BPRMF). To mitigate the bias in popularity, we use an item-based VAE for each popularity group with an additional fairness regularization. To make a reasonable recommendation even the predictions are inaccurate, we combine the recommended list of BPRMF and that of item-based VAE. Through the experiments, we demonstrate that the item-based VAE with fairness regularization significantly reduces popularity bias compared to the user-based VAE. The ensemble between the item-based VAE and BPRMF makes the top-1 item similar to the ground truth even the predictions are inaccurate. Finally, we propose a `Coefficient Variance based Fairness' as a novel evaluation metric based on our reflections from the extensive experiments.Comment: 6pages, CIKM 2022 Data challeng

NAS-VAD: Neural Architecture Search for Voice Activity Detection

Various neural network-based approaches have been proposed for more robust and accurate voice activity detection (VAD). Manual design of such neural architectures is an error-prone and time-consuming process, which prompted the development of neural architecture search (NAS) that automatically design and optimize network architectures. While NAS has been successfully applied to improve performance in a variety of tasks, it has not yet been exploited in the VAD domain. In this paper, we present the first work that utilizes NAS approaches on the VAD task. To effectively search architectures for the VAD task, we propose a modified macro structure and a new search space with a much broader range of operations that includes attention operations. The results show that the network structures found by the propose NAS framework outperform previous manually designed state-of-the-art VAD models in various noise-added and real-world-recorded datasets. We also show that the architectures searched on a particular dataset achieve improved generalization performance on unseen audio datasets. Our code and models are available at https://github.com/daniel03c1/NAS_VAD.Comment: Submitted to Interspeech 202

Spatio-Temporal Network for Sea Fog Forecasting

Sea fog can seriously affect schedules and safety by reducing visibility during marine transportation. Therefore, the forecasting of sea fog is an important issue in preventing accidents. Recently, in order to forecast sea fog, several deep learning methods have been applied to time series data consisting of meteorological and oceanographic observations or image data to predict fog. However, these methods only use a single image without considering meteorological and temporal characteristics. In this study, we propose a multi-modal learning method to improve the forecasting accuracy of sea fog using convolutional neural network (CNN) and gated recurrent unit (GRU) models. CNN and GRU extract useful features from closed-circuit television (CCTV) images and multivariate time series data, respectively. CCTV images and time series data collected at Daesan Port in South Korea from 1 March 2018 to 14 February 2021 by Korea Hydrographic and Oceanographic Agency (KHOA) were used to evaluate the proposed method. We compare the proposed method with deep learning methods that only consider temporal information or spatial information. The results indicate that the proposed method using both temporal and spatial information at the same time shows superior accuracy

Item-based Variational Auto-encoder for Fair Music Recommendation

1

Length Scale Analyses of Background Error Covariances for EnKF and EnSRF Data Assimilation

Data assimilation (DA) combines incomplete background values obtained via chemical transport model predictions with observational information. Several 3-Dimensional variational (3DVAR) and sequential methods (e.g., ensemble Kalman filter (EnKF)) are used to define model errors and build a background error covariance (BEC) and are important factors affecting the prediction performance of DA. The BEC determines the spatial range, where observation concentration is reflected in the model when DA is applied to an air pollution transport model. However, studies investigating the characteristics of BEC using air quality models remain lacking. In this study, horizontal length scale (HLS) and vertical length scale (VLS) analyses of a BEC were applied to EnKF and ensemble square root filter (EnSRF), respectively, and two ensemble-based DA methods were performed; the characteristics were compared with those of a BEC applied to 3DVAR. The results of 6 h PM2.5 predictions performed for 42 days were evaluated for a control run without DA (CTR), 3DVAR, EnKF, and EnSRF. HLS and VLS respectively exhibited a high correlation with the ground wind speed and with the planetary boundary layer height for diurnal and daily variations; EnKF and EnSRF exhibited superior performances among all the methods. The root mean square errors were 11.9 μg m−3 and 11.7 μg m−3 for EnKF and EnSRF, respectively, while those for 3DVAR and CTR were 12.6 μg m−3 and 18.3 μg m−3, respectively. Thus, we proposed a simple method to find a Gaussian function that best described the error correlation of the BEC based on the physical distance

A Sensorized Hybrid Gripper to Evaluate a Grasping Quality based on a Largest Minimum Wrench

Soft pneumatic grippers, which are based on soft pneumatic actuators have been widely studied owing to their simple morphological structure, inherent compliance, and pliable grasp. Additionally, the integration of the soft gripper with various sensors to improve its functionality has also been extensively studied. Although the soft gripper is known to exhibit a robust grasping performance without accurate control, the grasping quality of the soft gripper has rarely been studied due to the lack of adequate embedded sensors and quality metrics of the soft gripper. Therefore, a hybrid gripper, which is a soft gripper with rigid components, was sensorized by embedding a soft force sensor and a bending sensor to evaluate the grasping quality. Furthermore, a new grasping quality metric for a soft gripper was proposed, which calculates the largest minimum wrench of a convex hull in the wrench space. The proposed grasping quality metric was experimentally verified, and a real-time program was developed to evaluate the grasping quality

Suppression of Oxidative Degradation of Tin-Lead Hybrid Organometal Halide Perovskite Solar Cells by Ag Doping

We present a simple and effective method for increasing the power conversion efficiencies (PCEs) and oxidative stability of tin-lead hybrid perovskite solar cells (PSCs). The Ag-doped PSCs with encapsulation retain 95% of their initial PCE after exposure to ambient air for 1000 h. Ag doping increases the grain size and reduces the thickness of amorphous intergranular films, thereby inhibiting the infiltration of oxygen into the perovskite crystals. A quantum mechanical simulation with density 11 functional theory revealed that Ag doping increases the energy barrier to the adsorption of oxygen onto the perovskite surface. Ag doping also relaxes the microstrain in the perovskite, which suppresses the chemical interactions between O-2 and the perovskite. We also verify that this method is also applicable to the tin-only perovskite for highly stable lead-free PSCs. We believe that these results open up the possibility of the use of various dopants to fabricate stable lead-free PSCs.11Nsciescopu