Journal of University of Chinese Academy of Sciences

Tectonic stress chemistry: a possible perspective on focal mechanism of slow earthquakes

GUO Qianqian, SUN Jingxian, HOU Quanlin

2025, 42 (1): 1-12. DOI: 10.7523/j.ucas.2024.010

Research on the slow-earthquake focal mechanism was mainly based on brittle deformation. However, high ratios of P-wave to S-wave velocity, and anomalously high Poisson’s ratios indicate that the source material of slow earthquakes is more viscous and more prone to plastic deformation. Traditional studies suggest that plastic deformation begins with dislocation, and is permanent. Therefore, the plastic strain energy cannot be released. However, it may be different when talked about on a microscopic molecular scale. The lithosphere is mainly constructed of silicate minerals, especially of tetracoordinated compounds with [SiO₄] tetrahedrons as fundamental units. That is, within minerals, there are chemical bonds binding various atoms together. Therefore, the dislocation mechanism of plastic deformation may first start with the change of chemical bonds, and then the chemical bonds begin to break off and rebond, forming sub-grains and grain size reduction. Mechanochemical study shows that the mechanical force can directly act on the chemical bond via stretching and rotating, change the bond length and angle, and finally break off the chemical bond. Quantum chemical calculations on molecular fragments of the crystalline structure in coal indicate that the carbon bond breaks off at high energy levels, when the hydroxyl group of the 6-membered benzene ring falls off to form CO and 5-membered rings. During plastic deformation, the energy conversion may be work done from mechanical energy by external forces firstly to internal energy as atomic potential energy, and then plastic strain energy. However, not all atomic potential energy could transform into plastic strain energy for the reconstruction of the chemical bond may release energy. As a result, a little energy may be released during the plastic deformation. Whether this is related to slow earthquakes is a scientific proposition worth exploring. It may be a possible way to explore the focal mechanism of slow earthquakes by using atomic-scale quantum chemistry calculations to establish a finer energy change process of crystal plastic deformation and comparing the source parameters of slow earthquakes.

A class of quasilinear equations with -1 powers

ZHANG Heng, SUN Yijing

2025, 42 (1): 13-19. DOI: 10.7523/j.ucas.2023.006

Abstract ( 142 ) PDF (0KB) ( 0 )

This paper deals with quasilinear elliptic equations of singular growth like -Δu-uΔ(u²)=a(x)u^-1. We establish the existence of positive solutions for general a(x)∈L^p(Ω),p>2， where Ω is a bounded domain in ℝ^N with N≥1.

Learning the parameters of a class of stochastic Lotka-Volterra systems with neural networks

WANG Zhanpeng, WANG Lijin

2025, 42 (1): 20-25. DOI: 10.7523/j.ucas.2023.012

Abstract ( 218 ) PDF (0KB) ( 0 )

In this paper, we propose a neural network approach to learn the parameters of a class of stochastic Lotka-Volterra systems. Approximations of the mean and covariance matrix of the observational variables are obtained from the Euler-Maruyama discretization of the underlying stochastic differential equations (SDEs), based on which the loss function is built. The stochastic gradient descent method is applied in the neural network training. Numerical experiments demonstrate the effectiveness of our method.

Stochastic augmented Lagrangian method for stochastic nonconvex nonsmooth programs with many convex constraints

ZHAO Wenshen, HAN Congying, JIN Lingzi

2025, 42 (1): 26-42. DOI: 10.7523/j.ucas.2023.055

Abstract ( 228 ) PDF (0KB) ( 0 )

The stochastic gradient methods have been widely used in machine learning, but most existing works aim for unconstrained or simple constrained problems. In this paper, we consider the nonconvex stochastic programs with many functional convex constraints. The deterministic augmented Lagrangian method is a classic algorithm for such problems, but the requirement of accurate gradient information makes the method impractical for the case with large-scale constraints. To solve such problems, we propose a novel stochastic augmented Lagrangian method, which is called CSALM(composite stochastic augmented Lagrangian method). The CSALM uses a stochastic gradient to approximate the accurate gradient, and it only samples stochastic gradients and batches constraint gradient per iteration. We establish the convergence theory of CSALM and show that the CSALM can find an $\epsilon$-KKT point after $\mathcal{O}\left(\epsilon^{-8}\right)$ iterations. The numerical experiments on the multi-class Neyman-Pearson classification problem(mNPC) demonstrate the efficiency of CSALM.

Design of low temperature measurement experimental device based on superconductor magnetic penetration depth

ZHU Changyang, BIAN Xing, WANG Jinzhen, LIU Jie

2025, 42 (1): 43-49. DOI: 10.7523/j.ucas.2023.020

Abstract ( 245 ) PDF (0KB) ( 0 )

The magnetic penetration depth of the external magnetic field into the superconductor varies with the temperature, especially near the superconducting transition temperature, the penetration depth changes dramatically. Detecting the change of the penetration depth can achieve high-resolution measurement of temperature changes, which is an important principle of deep and low temperature measurement. Based on this basic principle, this work studies a temperature measurement scheme using the change of superconductor penetration depth, the quantization of closed superconducting loop magnetic flux and the superconducting quantum interference device (SQUID), carries out theoretical analysis and simulation, which is expected to achieve a temperature resolution of nK/$\sqrt{\mathrm{Hz}}$ in the liquid helium temperature region, and gives the specific experimental device design. This method offers high resolution, does not introduce additional heat flow, and does not require continuous current excitation. It can greatly reduce the adverse effects of the traditional temperature measurement caused by thermometer self-heating effect and contact thermal resistance. By plating superconducting film on the surface of the object，which is beneficial to temperature measurement experiments and applications below 10 K.

Characteristics of high technology manufacturing industry migration based on micro enterprise data: a case study of Beijing metropolitan area

ZHANG Peiyuan, LI Jiaming, ZHANG Wenzhong

2025, 42 (1): 50-60. DOI: 10.7523/j.ucas.2023.047

Abstract ( 170 ) PDF (0KB) ( 0 )

This study traces the migration process of key high-tech enterprises in Beijing during 2008-2016, revealing the migration characteristics and patterns of high-tech enterprises within the metropolitan area. The results show that medium-sized enterprises are more likely to relocate than small and large enterprises, especially in lucrative sectors. Moreover, migration is mainly within agglomerations, with relatively little migration across agglomerations and between agglomerations and non-agglomerations, although this varies between agglomerations. Finally, most high-tech manufacturing firms first relocate between 7 and 16 years after their establishment, which means that there is roughly a 7-year adaptation or development period for firms in a region after their establishment. During the adaptation period, companies do not tend to relocate, after which, as they grow, they need to find new spaces to grow. For reasons such as familiarity with the environment, enterprises give priority to finding new locations within the agglomeration and the surrounding area.

Basin ecological restoration zoning and land use simulation evaluation based on multivariate coupling model: a case study of Dianchi Lake Basin

WANG Jiaheng, YAN Wei, DUAN Xuejun, DUAN Yanyan, LI Zhuona, ZOU Hui

2025, 42 (1): 61-73. DOI: 10.7523/j.ucas.2023.039

Abstract ( 120 ) PDF (0KB) ( 0 )

Scientific delineation of watershed ecological restoration zones and simulation of land use scenarios in each zone can provide important support for the design of land space-related planning schemes such as watershed ecological restoration, ecological risk avoidance and land use index formulation. Taking the Dianchi Lake Basin as an example, this paper identified the ecological restoration zones of the Dianchi Lake Basin and conducted land use simulations under different scenarios based on the ecosystem service value and ecological risk calculation model, PLUS model, GIS analysis and other methods. The results showed that: 1) From 2000 to 2020, the ecosystem service value in the Dianchi Lake Basin decreased from 20.614 billion RMB to 19.271 billion RMB, and the proportion of areas with high ecological risk and above increased from 6.24% to 19.30%; 2) The spatial distribution of ecological restoration zones in the Dianchi Lake Basin was a circular structure. From the center of Lake Dianchi to the outside, ecological restoration zones were divided into 4 categories: the core area of ecological restoration, the important area of ecological restoration, the green development area and the ecological restoration and conservation area. The occupied area was 362.09, 109.99, 791.92, and 1 590.89 km², respectively; 3) Under the natural development scenario in 2030, the construction land in the Dianchi Lake Basin would increase by 189.92 km²; under the ecological restoration scenario, the construction land would increase by 53.75 km², and the urban expansion rate would slow down. The ecological restoration scenario had an additional ecosystem service value of 434 million RMB in the Dianchi Lake Basin compared with the natural development scenario.

Response of glacial isostatic adjustment (GIA) in Patagonia, South America based on hydrological and GRACE gravity data

LI Mengyu, SUN Pengchao, GUO Changsheng, WANG Changyu, WEI Dongping

2025, 42 (1): 74-85. DOI: 10.7523/j.ucas.2024.005

Abstract ( 75 ) PDF (0KB) ( 0 )

The Patagonia Plateau in South America is located in a complex tectonic area where the large ice sheets in the temperate zone are melting rapidly and the oceanic plate is subducting into the continental plate. The signal of glacial isostatic adjustment (GIA) and the mechanism of surface uplift in this area need to be further investigated. Based on the time-variable gravity data of gravity recovery and climate experiment (GRACE), this paper analyzes the characteristics of mass trends in the plateau from 2003 to 2016. Relevant hydrological models and remote sensing satellite data are used to improve the combined hydrological model of this region and extract the spatial variation characteristics of its hydrological information. The current GIA signals are obtained by deducting hydrologic signals from the integrated GRACE signals. The contribution of GIA effect to land surface uplift is analyzed using global positioning system (GPS) data. The results show mass loss in and around Patagonia Icefield (PIF) and mass increase in the south and north of the Patagonia Plateau. The hydrologic mass loss forms a spatial distribution with PIF as the center and the negative signal gradually weakening. The GIA response causes the plateau uplift and is most significant in the southern part of PIF, reaching a maximum of (1.97±0.35) cm/a. The GIA signal is similar to the GIA model. The GIA signals can interpret about 69.25% and 82.70% of GPS vertical speed signals in Northern Patagonia Icefield (NPI) and Southern Patagonia Icefield (SPI), respectively.

Organic mineralization in lead-zinc deposits: a case study of the Jinding lead-zinc deposit, Lanping Basin

HOU Xingao, JU Yiwen, FENG Hongye, XIAO Lei, QIAO Peng, TAO Liru, WANG Peng, WANG Wei, GAO Jian

2025, 42 (1): 86-106. DOI: 10.7523/j.ucas.2024.016

Abstract ( 148 ) PDF (0KB) ( 0 )

A large amount of organic matter (OM) is associated with ore bodies in the Jinding lead-zinc deposit, Lanping Basin, the northwestern Yunnan Province, but the way and process of OM participation in lead-zinc mineralization remain controversial. OM in the deposit has generally undergone biodegradation, and much of it still contains detectable compounds such as n-alkanes, isoprenoids, naphthalene, phenanthrene, and biphenyl. A small portion of OM does not contain n-alkanes and isoprenoids but shows the characteristics of initial degradation of steranes while no 25-norhopane is generated, which is generally in line with the characteristics of grade 2-5 biodegradation, consistent with the bacterial sulfate reduction (BSR). No significant correlation is observed between the δ¹³C_PDB and δ¹⁸O_PDB values of calcites, and their distribution patterns of REEs, Y/Ho values, and Sr contents are also inconsistent with the characteristics of thermochemical sulfate reduction (TSR) calcites. The δ¹³C_PDBvalues (~-27‰) of bitumen in the deposit are not less than those of source rocks (estimated value), so it is reasonable to infer that TSR is not the main way for OM to participate in the lead-zinc mineralization. The estimation results of δ³⁴S show that the δ³⁴S of H₂S generated by the thermal decomposition of OM is from -5‰ to 0, which is consistent with the range of heavy sulfur isotope peaks (-8‰~-2‰) in the δ³⁴S value histogram of metal sulfides in the deposit. Based on mineralization characteristics, if one-third of the lead-zinc ore is related to the thermal decomposition of OM, and the sulfur content of crude oil in the paleo reservoir is 1.5%, the amount of crude oil required for mineralization is calculated to be about 96.87 million tons, which is not contradictory to geological facts. Therefore, we propose that OM was mainly involved in lead-zinc mineralization through BSR in the formation stage of paleo reservoirs and thermal decomposition of OM in the high-temperature mineralization stage, while large-scale TSR might not occur.

Remote sensing semantic segmentation method based on high-resolution relational graph convolutional network

WANG Yinda, CHEN Jiahui, PENG Ling, LI Zhaobo, YANG Lina

2025, 42 (1): 107-115. DOI: 10.7523/j.ucas.2023.079

Abstract ( 312 ) PDF (0KB) ( 0 )

Semantic segmentation of remote sensing images is an important task in remote sensing image processing and analysis, especially in multi-category semantic segmentation. Current methods mainly revolve around convolutional neural networks, but convolution only focuses on the local information of the image while ignoring the global information. Therefore, inspired by high resolution network (HRNet) and relational graph convolutional network (R-GCN), this paper proposes a high-resolution relational graph convolutional network (HRGCN) for multi-category semantic segmentation. Firstly, simple linear iterative clustering (SLIC) is done on the original image, and the result is used to segment the feature map output from HRNet to obtain superpixel blocks with high homogeneity and containing multi-resolution information; then graph nodes and edges are constructed based on the superpixel blocks, and R-GCN is used to classify the graph nodes, so as to learn the long-distance dependency between different features and complete the extraction and classification of remote sensing images. The HRGCN model designed in this paper is experimented on Potsdam and Vaihingen datasets, and the results are compared with the existing methods, and the $\bar{F}_1$ values and MIoU values are improved to certain degrees, which proves that the method has good advancement.

Shallow subsurface structure of the Utopia Planitia based on Zhurong rover penetrating radar data

YANG Jiaqi, SHAO Yun, BIAN Xiaolin, ZHANG Tingting, WANG Guojun

2025, 42 (1): 116-125. DOI: 10.7523/j.ucas.2023.030

Abstract ( 235 ) PDF (0KB) ( 0 )

Mars subsurface exploration is essential to obtain information on the historical evolution of Mars and to search for possible living environments on Mars. The rover penetrating radar (RoPeR) on board Zhurong, the rover of China’s first Mars exploration mission, is used to detect the subsurface structure of Utopia Planitia. In this paper, high-frequency channel data of RoPeR are selected to obtain the shallow subsurface information of Utopia Planitia. This study includes 1) subsurface structure modeling of the landing area and numerical simulation of shallow subsurface echo based on the finite-difference time-domain (FDTD) algorithm; 2) processing the high-frequency channel data of RoPeR; 3) interpreting the shallow subsurface structure of Utopia Planitia. The study results validate the ability of RoPeR to detect shallow subsurface structure. There is a 10-20 cm duricrust at the surface of the Zhurong landing area. Under the duricrust are loose weathering material and randomly distributed gravels, which gradually transition to the middle Amazonian sedimentary sequence with increasing depth. There are strong echo signals in the radar image of Sol 101, which are presumed to be related to recent meteorite activity. The results of the study initially reveal the shallow subsurface structure of Utopia Planitia, which is a good reference for the situ probing and sampling experiments of the subsequent Mars exploration missions.

Ultra-reliable low-latency edge computing architecture for 6G

DING Yuhua, CHEN Li, WEI Guo

2025, 42 (1): 126-133. DOI: 10.7523/j.ucas.2023.029

Abstract ( 218 ) PDF (0KB) ( 0 )

MEC (mobile edge computing) is the supporting technology for the 6G mobile communication network to connect communication and service and realize the smart connection of everything. For the computational delay optimization of the MEC system, a horizontal multi-host architecture is proposed and a complete signaling flow is designed. For the transmission delay optimization of the MEC system and the straggler problem of multi-host parallel computation, a master-slave architecture of multi-connectivity is proposed and a complete signaling flow is designed. For the evaluation of MEC system performance, a multi-host MEC simulation platform based on the open-source libraries is built. The experiments show that the horizontal multi-host MEC architecture effectively improves computational latency performance; the proposed master-slave MEC architecture of multi-connectivity effectively alleviates the straggler problem and improves transmission latency performance; the built MEC simulation platform can effectively evaluate the key performance indicators of the multi-host architecture.

Public participation, environmental regulation, and residents' well-being: a bibliometric analysis based on CiteSpace

ZOU Yurou, LIU Hong, LYU Chen

2025, 42 (1): 134-144. DOI: 10.7523/j.ucas.2023.080

Abstract ( 255 ) PDF (0KB) ( 0 )

The research on the relationship between public participation, environmental regulation and residents’ well-being is of great significance for the scientific formulation of environmental regulation policies and the optimization of the governance environment. Using the data of journal papers collected by Web of Science and CNKI from 2006 to 2021, using CiteSpace bibliometric analysis software and combining with traditional review methods, this paper draws the following conclusions: 1) Chinese literature research hotspots have gone through three stages: the western experience discussion of public participation in environmental governance and the initial stage in China, the theoretical model analysis of public participation in environmental governance and the empirical research stage of influencing factors, the evaluation of residents’ well-being effect of environmental regulation and the specific case study of public participation in environmental regulation. English literature research initially focused on the participation of residents at the community level in environmental regulation, and then focused on the exploration of problems and influencing factors in practice. At present, it focuses on the impact of environmental regulation on residents’ well-being and environmental health inequity and big data analysis applications； 2) The academic community has not yet reached a consistent conclusion on the impact of public participation in environmental regulation and residents’ well-being. The study confirms that environmental regulation has a positive impact on residents’ health and enhances individual subjective well-being, but at the same time it exacerbates the income gap between residents and between regions； 3) The research trend shows that the research perspective changes from macro to micro, the research method changes from statistical model to spatial analysis and quasi-natural experiment method, and the variable measurement changes from single index to comprehensive index； 4) Future research needs to focus on the analysis and optimization of government response mechanism, the research on the equity of environmental regulations on residents’ well-being, and the improvement and perfection of research methods, data, and variable measurement methods.

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