Laplacian Canonization: A Minimalist Approach to Sign and Basis Invariant Spectral Embedding

Spectral embedding is a powerful graph embedding technique that has received a lot of attention recently due to its effectiveness on Graph Transformers. However, from a theoretical perspective, the universal expressive power of spectral embedding comes at the price of losing two important invariance properties of graphs, sign and basis invariance, which also limits its effectiveness on graph data. To remedy this issue, many previous methods developed costly approaches to learn new invariants and suffer from high computation complexity. In this work, we explore a minimal approach that resolves the ambiguity issues by directly finding canonical directions for the eigenvectors, named Laplacian Canonization (LC). As a pure pre-processing method, LC is light-weighted and can be applied to any existing GNNs. We provide a thorough investigation, from theory to algorithm, on this approach, and discover an efficient algorithm named Maximal Axis Projection (MAP) that works for both sign and basis invariance and successfully canonizes more than 90% of all eigenvectors. Experiments on real-world benchmark datasets like ZINC, MOLTOX21, and MOLPCBA show that MAP consistently outperforms existing methods while bringing minimal computation overhead. Code is available at https://github.com/PKU-ML/LaplacianCanonization.Comment: In Thirty-seventh Conference on Neural Information Processing Systems (2023

CFAD: A Chinese Dataset for Fake Audio Detection

Fake audio detection is a growing concern and some relevant datasets have been designed for research. However, there is no standard public Chinese dataset under complex conditions.In this paper, we aim to fill in the gap and design a Chinese fake audio detection dataset (CFAD) for studying more generalized detection methods. Twelve mainstream speech-generation techniques are used to generate fake audio. To simulate the real-life scenarios, three noise datasets are selected for noise adding at five different signal-to-noise ratios, and six codecs are considered for audio transcoding (format conversion). CFAD dataset can be used not only for fake audio detection but also for detecting the algorithms of fake utterances for audio forensics. Baseline results are presented with analysis. The results that show fake audio detection methods with generalization remain challenging. The CFAD dataset is publicly available at: https://zenodo.org/record/8122764.Comment: FAD renamed as CFA

基于雷电物理的风机叶片动态击距与 电气几何模型

The damage of wind turbine blades suffered lightning strikes has been a key factor of the safe and reliable operation of wind farms. The electric geometrical model of wind turbine blades (EGMTB) was presented based on the traditional electric geometrical method and the physical process of lightning leader. The concept of dynamic striking distance was introduced and clarified the physical meaning of striking distance. And the calculation method of blade lightning protection system (LPS) efficiency was deduced. Finally, the effectiveness of EGMTB was validated by the long gap breakdown experiment of blades. The EGMTB was used to analyze the influence factors of blade LPS efficiency. It is indicated that the efficiency of blade LPS reduces with the decrease of lightning current and the angle between the blade and horizontal, and the efficiency of blade LPS can be improved by increasing the side lightning receptors. The EGMTB is intended to provide a theory for lightning protection design and evaluation of wind turbine blades

Synthesis of KAlSiO4 by Hydrothermal Processing on Biotite Syenite and Dissolution Reaction Kinetics

To make potassium from K-bearing rocks accessible to agriculture, processing on biotite syenite powder under mild alkaline hydrothermal conditions was carried out, in which two types of KAlSiO4 were obtained successfully. The dissolution-precipitation process of silicate rocks is a significant process in lithospheric evolution. Its effective utilization will be of importance for realizing the comprehensiveness of aluminosilicate minerals in nature. Two kinds of KAlSiO4 were precipitated in sequence during the dissolution process of biotite syenite. The crystal structures of two kinds of KAlSiO4 were compared by Rietveld structure refinements. The kinetics model derived from geochemical research was adopted to describe the dissolution behavior. The reaction order and apparent activation energy at the temperature range of 240–300 °C were 2.992 and 97.41 kJ/mol, respectively. The higher dissolution reaction rate of K-feldspar mainly relies on the alkaline solution, which gives rise to higher reaction order. During the dissolution-precipitation process of K-feldspar, two types of KAlSiO4 with different crystal structure were precipitated. This study provides novel green chemical routes for the comprehensive utilization of potassium-rich silicates

Synthesis of Analcime Crystals and Simultaneous Potassium Extraction from Natrolite Syenite

Analcime single crystals were successfully synthesized from natrolite syenite powder (K2O 10.89%) and 92.6% of potassium was extracted simultaneously by means of soda roasting followed by alkali-hydrothermal method. Effects of NaOH concentration, reaction temperature, and holding period on the analcime formation and potassium extraction were investigated systemically. The results indicated that NaOH concentration plays an important role in determining the chemical composition of zeolites and size distribution; by turning the NaOH concentrations, three different pure zeolites (i.e., the phillipsite-Na, the analcime, and the sodalite) were prepared. Besides, a higher temperature could accelerate the dissolution of K+ ions and enhance the crystallinity degree of zeolite. The reactions involved in the analcime synthesis can be summarized as follows: sodium aluminum silicate dissolution → precipitation and dissolution of metastable zeolite-P → analcime nucleation → analcime growth. The extraction ratio of K+ is associated with the types of synthesized zeolites, among which analcime is the most effective to promote potassium leaching out from zeolite lattice position. The optimal condition for analcime crystallization and K+ leaching is found to be as follows: 175°C for 4 h in 0.5 mol/L NaOH solution

Comparative analyses of the air distributions created by attached ventilation with different air outlets

As an innovative ventilation mode, attached ventilation has been widely used in different types of buildings due to its high ventilation efficiency and energy saving. At present, the commonly used air outlet form is slot outlet. Considering the diversity of application places, different air outlet form models (Slot outlet (SO), Rectangular outlet (RO), Circular outlet (CO), Semi-circular outlet (SCO)) were established in this paper. Air distributions of the attached ventilation under different air outlet forms are analyzed and compared. The results show that the attached jet thickness is larger under RO, CO, and SCO form. Compared with SO form, the jet velocities of other three forms decay slowly in the vertical region. The attached ventilation with different outlet forms can form an "air lake" in the occupied zone to ensure the comfort environment. This research provides design references for the design and application of the attached ventilation under different air outlet forms

Train-induced unsteady airflow (TIUA) characteristics of track area in subway station with platform screen doors (PSDs)

Train-induced unsteady airflow (TIUA) has a great effect on the ventilation and thermal environment of a subway line. Track area, connecting tunnel with station, is the source of the TIUA acting on subway station. Exploring the TIUA characteristics of track area contributes to utilizing the TIUA for improving the tunnel and station environment. In this study, a 1D numerical model according to an actual subway line was established by IDA Tunnel software, to analyse the TIUA rates through the inbound and outbound ends of track area in the PSDs subway station. Four key factors, namely, train arrival time interval between both tunnels, train interval, operation modes of piston vent shafts and bypass ducts, were analysed. The results demonstrate that the TIUA rates of track area in PSDs subway station (bypass ducts closed) are mainly affected by the train driving in this tunnel. The TIUA rates of track area decreases about 36%∼41%, as the train interval increases from 180 s to 540 s. By adjusting the operation modes of piston vent shafts, the change of TIUA rates of track area can reach up to about 13%∼27%. By opening bypass ducts, the TIUA rates of track area decreases by 42%∼50%