Semantic Proximity Alignment: Towards Human Perception-consistent Audio Tagging by Aligning with Label Text Description

Most audio tagging models are trained with one-hot labels as supervised information. However, one-hot labels treat all sound events equally, ignoring the semantic hierarchy and proximity relationships between sound events. In contrast, the event descriptions contains richer information, describing the distance between different sound events with semantic proximity. In this paper, we explore the impact of training audio tagging models with auxiliary text descriptions of sound events. By aligning the audio features with the text features of corresponding labels, we inject the hierarchy and proximity information of sound events into audio encoders, improving the performance while making the prediction more consistent with human perception. We refer to this approach as Semantic Proximity Alignment (SPA). We use Ontology-aware mean Average Precision (OmAP) as the main evaluation metric for the models. OmAP reweights the false positives based on Audioset ontology distance and is more consistent with human perception compared to mAP. Experimental results show that the audio tagging models trained with SPA achieve higher OmAP compared to models trained with one-hot labels solely (+1.8 OmAP). Human evaluations also demonstrate that the predictions of SPA models are more consistent with human perception.Comment: 5 pages, 3 figures. Submitted to ICASSP 202

A Sketch-based Rapid Modeling Method for Crime Scene Presentation

The reconstruction of crime scene plays an important role in digital forensic application. This article integrates computer graphics, sketch-based retrieval and virtual reality (VR) techniques to develop a low-cost and rapid 3D crime scene presentation approach, which can be used by investigators to analyze and simulate the criminal process. First, we constructed a collection of 3D models for indoor crime scenes using various popular techniques, including laser scanning, image-based modeling and geometric modeling. Second, to quickly obtain an object of interest from the 3D model database, a sketch-based retrieval method was proposed. Finally, a rapid modeling system that integrates our database and retrieval algorithm was developed to quickly build a digital crime scene. For practical use, an interactive real-time virtual roaming application was developed in Unity 3D and a low-cost VR head-mounted display (HMD). Practical cases have been implemented to demonstrate the feasibility and availability of our method

Reliable metal alloy contact for Mg3+δBi1.5Sb0.5 thermoelectric devices

Proper contacts between thermoelectric (TE) materials and electrodes are critical for TE power generation or refrigeration. The Bi-rich n-type Zintl material Mg3+δBi2-xSbx exhibits very good TE performance near room temperature, which makes Mg3+δBi2-xSbx-based compounds highly promising candidates to replace the Bi2Te3-ySey alloys, but ideal contacts that can match their TE performance have not yet been well studied. Here we investigate different metal (Ni and Fe) and metal alloy (NiFe, NiCr, NiCrFe, and stainless steel) contacts on n-type Mg3+δBi1.5Sb0.5. It is first shown that the low Schottky barrier and narrow depletion region resulting from the band degeneracy and high carrier concentration of a heavily doped TE material are beneficial for the formation of a low-resistivity ohmic contact with a metal or a metal alloy. Most fully optimized TE materials can take advantage of this. Second, it is found that the NiFe/Mg3+δBi1.5Sb0.5 contact exhibits excellent thermal stability and the lowest ohmic contact resistivity among those studied after aging for over 2100 h, which is attributed to the formation of metallic NiMgBi between the NiFe and Mg3+δBi1.5Sb0.5 layers. As a buffer phase, NiMgBi can effectively prevent elemental diffusion without negatively affecting the electron transport. Benefiting from such low contact resistance, a Mg3+δBi1.5Sb0.5/Bi0.4Sb1.6Te3 unicouple exhibits competitive conversion efficiency, 6% with a 150 K temperature difference and a hot-side temperature of 448 K

Dynamic Characteristics and Working Modes of Permanent Magnet Electrodynamic Suspension Vehicle System Based on Six Wheels of Annular Halbach Structure

A novel type of suspension system for maglev vehicles using six permanent magnet electrodynamic wheels (EDW) and conductor plate has been designed. It has the advantages of high speed, environmental protection, and a low turning radius. Differing from existing maglev vehicles, this paper proposes a new maglev vehicle utilizing six EDWs to respectively provide driving force and levitation force. This structure can keep the levitation force at a large constant value and obtain enough driving force at low rotational speeds by adjusting the motor speed. First, the structure of the electrodynamic wheel is given. The accuracy and validity of the FEM results are verified by the experiments. Moreover, based on the finite element method (FEM), the optimal structure of the EDWs is obtained with the objective of maximum levitation force. Then, the simplified electromagnetic force model is obtained by using MATLAB Toolbox. Third, using a co-simulation of Simulink and Adams to design and build a 1:50 maglev vehicle model, this article studies the dynamic response characteristics of the maglev vehicle model from the perspective of dynamics and proposes a feedback control strategy by adjusting the rotational speed to control the maglev vehicle. This paper also proposes a method to realize the car’s pivot steering to reduce the car’s turning radius and help the drivers pass narrow road sections. This article verifies the feasibility of the maglev vehicle with six EDWs and is expected to provide a certain reference for the development of permanent magnet electrodynamic suspension vehicles

Defect charging and resonant levels in half-Heusler Nb1-xTixFeSb

We report Nb and Sb NMR and J Fe Mdssbauer studies combined with DFT calculations of Nbi-arTixFeSb (0 ^ x ^ 0.3), one of the most promising thermoelectric systems for applications above 1000 K. These studies provide local information about defects and electronic configurations in these heavily p-type materials. The NMR spin-lattice relaxation rate provides a measure of states within the valence band. With increasing x, changes of relaxation rate vs carrier concentration for different substitution fractions indicate the importance of resonant levels which do not contribute to charge transport. The local paramagnetic susceptibility is significantly larger than expected based on DFT calculations, which we discuss in terms of an enhancement of the susceptibility due to a Coulomb enhancement mechanism. The Mossbauer spectra of Ti-substituted samples show small departures from a binomial distribution of substituted atoms, while for unsubstituted p-type NbFeSb, the amplitude of a Mossbauer satellite peak increases vs temperature, a measure of the T-dependent charging of a population of defects residing about 30 meV above the valence band edge, indicative of an impurity band at this location.1

NMR and Mössbauer study of p-type half-Heusler thermoelectrics Nb 1- x Ti x FeSb

To investigate the local behavior of defects and mixed compositions in NbFeSb-based semiconductors, for improved thermoelectric efficiency, we have performed 93Nb and 121Sb NMR, as well as Mössbauer measurements, on pure NbFeSb and a series of p-type Ti-substituted (Nb,Ti)FeSb samples with different substitution levels. A small but consistently increasing paramagnetic defect density is observed with the increase of Ti substitution level revealing the existence of additional Ti-induced paramagnetic defects. NMR line shapes show a clear difference between effect of intrinsic and extrinsic defects in NbFeSb. The NMR shifts can be well understood by a model combining a Knight shift and composition-dependent chemical shift. The results indicate a nearly rigid-band behavior for the valence band with a small enhacement of effective mass vs substitution. For pure NbFeSb samples, the Mössbauer spectra include an additional T-dependent singlet. The increase of its area can be explained based on carriers activated into a shallow acceptor-like defect level above the valence band, consistent with the defect activation results obtained with NMR. In samples with Ti substitution, the Mössbauer spectra are consistent with a random neighbor distribution, indicating no preferential local ordering.1-1