Search Results (181)

This work presents the first systematic development of the inverse scattering transform for matrix nonlinear Schrödinger equations in the case where the discrete spectrum has triple poles, under nonzero boundary conditions at infinity. These systems arise physically as reductions modeling spinor Bose-Einstein condensates with hyperfine spin $F=1$ and find applications in nonlinear optics. A uniformization variable is employed to map the underlying Riemann surface to the complex plane, enabling a complete characterization of the analyticity, symmetries, and asymptotic behaviors of the Jost functions and scattering data. Extending the established framework for simple and double poles, we show that $\mathrm{rank} P(x,t,z_n)=3$ requires a third-order zero of $\det a\left(z\right)$ at $z=z_n$, while $\mathrm{rank} P(x,t,z_n)=2$ necessitates a fourth-order zero—a nontrivial feature absent in lower-order cases. The discrete spectrum for both rank configurations is fully characterized, and the full singular behavior near a triple pole is derived, respecting the quartet symmetry $z_n$, $z_n^{*}$, $v{k}_0^2/z_n$, $v{k}_0^2/z_n^{*}$ imposed by the nonzero boundary conditions. Solving the resulting matrix Riemann-Hilbert problem with triple poles yields the potential reconstruction formula and, in the reflectionless case, explicit expressions for general N-triple-pole soliton solutions, with a detailed example for $N=1$ presented to illustrate the construction. Full article

Frequent flash floods threaten human well-being, hydropower infrastructure, and ecosystems. However, the long-term evolution of flash flood patterns over recent decades remains insufficiently understood, particularly in data-scarce high-altitude regions. Using multi-source remote sensing data integrated with historical disaster records and field investigations, this study examined the spatiotemporal evolution and driving factors of flash floods across the Qinghai–Tibet Plateau (QTP). The results indicate that flash floods have increased exponentially, which may be influenced by disaster management policies, with peaks in July–August and frequent occurrences from April to September. The seasonal trajectory of the center of gravity of flash floods from April to September exhibited a clear directional pattern. Regions with the highest disaster density were concentrated in the headwaters of five major rivers, including the Yarlung Zangbo, Jinsha, Nu, Lancang, and Yellow Rivers. Shapley Additive Explanation (SHAP) and Random Forest analyses reveal that soil moisture, anthropogenic intensity, and seasonal runoff variability are the dominant driving factors. With ongoing socioeconomic development, intensified human activities have become a key contributor to the increasing frequency of flash floods. These findings highlight the value of remote sensing-based assessments for flash flood monitoring and early warning and provide scientific support for risk mitigation, loss reduction, and the advancement of water-related targets under the United Nations’ Sustainable Development Goals. Full article

Coastal wetlands represent significant sources of greenhouse gases (GHGs) and serve as crucial ecological interfaces between terrestrial and marine environments, substantially contributing to global biogeochemical cycles. However, GHG emission fluxes are strongly influenced by complex anthropogenic activities, yet their underlying microbial mechanisms remain poorly understood. This study investigated seven representative human-impacted sites within the Yellow River Delta. Employing a combined approach of in vitro microcosm cultivation, molecular biology, and multivariate statistical analysis, we investigated the integrated mechanisms controlling nitrous oxide (N₂O) and methane (CH₄) fluxes, with consideration of soil depth, environmental factors, microbial communities, and functional microbes. The results indicated that significant differences in GHG fluxes among different anthropogenic activities and soil depths (p < 0.05). Surface soil N₂O fluxes were positive within sewage irrigation areas (20.98–35.08 mg N₂O-N m⁻² h⁻¹) and tourism development areas (12.52–23.87 mg N₂O-N m⁻² h⁻¹), while mariculture areas displayed negative fluxes. CH₄ fluxes were positive exclusively in natural areas (surface soil: 25.02–55.54 mg CH₄-C m⁻² h⁻¹; deep soil: 8.38–356.68 mg CH₄-C m⁻² h⁻¹), while other areas predominantly showed negative values (surface soil: −130.98–44.32 mg CH₄-C m⁻² h⁻¹; deep soil: −106.16–65.24 mg CH₄-C m⁻² h⁻¹). Furthermore, a structural equations model highlighted the pivotal role of key functional microbes in soil carbon–nitrogen cycling (e.g., nirK, nosZII, and SRB) involved in soil carbon–nitrogen cycling in negatively regulating N₂O and CH₄ fluxes. The study also revealed distinct microbial responses across diverse habitats, underscoring the significant role of Proteobacteria in wetland soil. This research enhances our understanding of GHG dynamics in coastal wetlands and provides scientific evidence and potential regulatory pathways for enhancing soil biological mitigation functions and achieving carbon neutrality and sustainability within wetland ecosystems. Full article

Frequency-selective attenuation is widely needed in integrated analog front-ends, yet conventional on-chip RC low-pass filters occupy unfeasibly large silicon areas for low-frequency cutoffs and inherently introduce cumulative phase lag. Motivated by the nonlinear, frequency-dependent state evolution of memristive devices, this work experimentally demonstrates a highly compact, capacitor-free memristor–resistor network that functions as a variable-cutoff, zero-phase-lag resistive attenuator. An Au/HfO₂/Au memristor (15 µm × 15 µm) is connected in series with a load resistor and characterized over a wide frequency range. By leveraging the finite time constant of internal ionic drift, the attenuation bandwidth is strictly programmable via the device’s initial resistance. Cutoff frequencies of approximately 10 Hz, 1 kHz, and 10 kHz are achieved for initial resistances of 400 k$\Omega \pm$30 k$\Omega$, 300 k$\Omega \pm$30 k$\Omega$, and 200 k$\Omega \pm$30 k$\Omega$, respectively. Remarkably, the nonlinear state-switching mechanism enables a steep post-cutoff attenuation rate approaching −60 dB/dec—equivalent to a cascaded third-order RC network—using only a single nanoscale device. Rather than functioning as a strictly linear time-invariant (LTI) filter, the proposed circuit operates as a state-adaptive edge-processor. Its inherent amplitude-dependent dynamics and total absence of reactive poles make it exceptionally suited for highly specialized, area-constrained applications, including zero-phase closed-loop noise suppression, frequency-to-amplitude conversion, and amplitude-aware event-driven sensory preprocessing. Full article

This study examines the impact of the spatial flow of new quality productive forces (NQPFS) and the optimal combination of new quality productive forces (NQPFC) on the high-quality economic development (HQMED) of China’s coastal regions. Based on panel data from 53 coastal cities (2004–2023), the research constructs comprehensive evaluation systems and employs a two-way fixed effects model for empirical analysis. The main findings are as follows: First, Spatial Evolution: The HQMED level of coastal areas shows a continuous upward trend with marked regional disparities, forming a spatial pattern of “one core, two wings” characterized by “Eastern leadership with Northern and Southern regions following.” The inter-city development gap has widened, with the overall spatial structure evolving from a “core-periphery” model toward a clustered stage of “one core, multiple poles, and networked linkage.” Correspondingly, New Quality Productive Forces have transitioned from initial single-point agglomeration to a multi-polar and ultimately networked distribution. Second, both the spatial flow and optimal combination of New Quality Productive Forces exert stable positive effects on coastal HQMED. The marginal contribution of the factor optimal combination is significantly greater than that of spatial flow. Third, two complete mediation pathways are identified: NQPFS promotes HQMED primarily by enhancing the resilience of the marine industrial chain, while NQPFC drives HQMED mainly through cultivating new-quality marine business forms. Fourth, resource misallocation exerts a significant negative moderating effect on the relationship between NQPFS and HQMED. Conversely, a sound innovation ecosystem positively moderates the impact of NQPFC on HQMED. Fifth, the effects exhibit significant regional and institutional variation. Geographically, the impact follows a pattern of “strong in the East, suppressed in the North, and insignificant in the South.” Administratively, core cities demonstrate stronger factor capture and configuration efficiency compared to ordinary cities. The study confirms that facilitating the cross-regional flow and efficient internal recombination of the New Quality Productive Force is crucial for driving coastal HQMED. Policy should focus on reducing resource misallocation to remove barriers to factor mobility, optimizing regional innovation ecosystems to enhance factor synergy, and implementing differentiated strategies that balance the radiating role of core cities with the distinctive development of ordinary cities, thereby fostering a new, coordinated pattern of high-quality development across coastal regions. Full article

This article provides the first comprehensive description and assessment of environmental changes in a unique natural transboundary region—South-Eastern Altai, which is located in the arid territories of Russia and Mongolia. This region of Asia is rightfully included in the high-mountain Third Pole (Roof of the World). In three key areas, Tsambagarav Massif (Mongolia), Mongun-Taiga Massif, and North-Chuya Ridge (Russia), the following are considered: (1) the latest dynamics of glaciers from the early 1960s (beginning of regular instrumental observations) to the present day; (2) climate change and land use systems; and (3) the characteristics of the biota and the causes of its dynamics. The article concludes with a consideration of (4) population adaptation models. Full article

This study constructs a global transportation carbon emission spatial correlation network via a modified gravity model and explores its evolutionary characteristics and dynamic mechanisms by integrating three-dimensional evolutionary analysis (node, overall, structural) and temporal exponential random graph model (TERGM). The main findings are as follows: (1) Global transportation carbon emission spatial correlation intensity keeps rising, with improved connectivity and integration, forming three regionally agglomerated correlation poles centered on the United States (America), China (Asia) and major European countries (Europe). (2) Network centrality distributes asymmetrically: Switzerland, Norway and the United States remain core nodes, while China, Japan and other Asian economies with strong direct correlation radiation are not in the core tier. (3) Third, evolutionary dynamics stem from the synergistic interaction of multidimensional attributes. ① Economic level positively drives bidirectional connection emission and attraction; economic scale and openness curb emission but boost attraction, while tertiary industry structure inhibits both. ② Only economic level and government efficiency exert significant positive effects on absdiff, fostering network heterophilic attraction. ③ Spatial and institutional proximity in edgecov effectively facilitate connection formation. ④ Endogenous network variables present a collaborative mechanism of reciprocity and transmission, constrained by network density. ⑤ Temporal effects show early connection structure forms path dependence, resulting in low dynamic variability and overall network stability. Full article

Ice cores retrieved from the Third Pole provide invaluable information about past and present environmental changes. Here we present, for the first time, a continuous tritium and plutonium isotope profile of the Puruogangri ice field, Tibetan Plateau, China, for the last 70 years. The age-depth profile has been composed by different time anchors such as the onset of thermonuclear weapon tests, the so-called bomb peak of tritium, the Chernobyl event, and the time of ice coring. The accumulation rate of ice calculated from the age-depth relation shows a decrease after 1963. It was 57, 15, and 22 cm/year in the periods of 1954–1963, 1963–1986, and 1986–2023, respectively. The concentrations of plutonium isotopes (²³⁹Pu: up to 2.7 fg/g) are slightly lower than those of the Belukha ice core, Siberian Altai, Russia, and almost the same as the Miaoergou glacier, eastern Tien Shan, China. Contrary to this latter ice core profile, the Puruogangri plutonium profile reflects that the Chinese weapon test started in 1966. This is confirmed by the tritium time series as well. ²⁴⁰Pu/²³⁹Pu atomic ratios vary between 0.14 and 0.23, with an average of 0.177 ± 0.024. The overall obtained local fallout of ²³⁹Pu and ²⁴⁰Pu is 13.2 and 9.0 Bq/m² (4.0 and 1.1 ng/m²), respectively. Full article

The lake systems of the Qinghai–Tibet Plateau, while serving as vital hubs for socioeconomic development, have become critical zones of heavy metal contamination, posing severe threats to the fragile “Third Pole” ecosystem and regional environmental security. This study investigated the concentration, distribution, sources, and ecological risks of eight heavy metals (As, Cd, Co, Cr, Cu, Ni, Pb, and Zn) in lake sediments and riparian soils of Bangong Co Lake, a remote alpine lake on the Qinghai–Tibet Plateau. Lake sediment and soil samples were collected and tested from various shoreline types, including natural and human-affected areas. The Pollution Load Index (PLI) was applied to assess contamination levels, and source apportionment was performed using principal component analysis (PCA) combined with the Absolute Principal Component Score–Multiple Linear Regression (APCS-MLR) receptor model. Results revealed that heavy metal concentrations were generally higher in soils than in sediments. Compared to regional background values, elevated levels of most heavy metals were observed in human-affected shores, while natural-type soils exhibited higher concentrations of Co, Cr, Ni, and As. In sediments, only Cd and As were notably elevated in human-affected areas. The PLI results indicated that most sampling sites were either uncontaminated or slightly contaminated, with higher pollution levels occurring primarily in human-affected shoreline zones. Source apportionment demonstrated that heavy metals in sediments were predominantly derived from natural sources such as rock weathering, with anthropogenic contributions being relatively limited. In contrast, soils exhibited significant anthropogenic influences, with industrial, transportation, and agricultural activities contributing substantially to Cu (53.27%), Pb (58.64%), Zn (57.98%), Cd (34.09%), and As (39.87%). The research underscores the differential impacts of human activities on heavy metal accumulation in sediments and soils of high-altitude lake systems. It offers valuable baseline data for monitoring and managing heavy metal pollution in ecologically sensitive alpine regions. Full article

The paper deals with the results of a study of a third-order nonlinear differential equation with moving singular points and critical poles. So far, this type of equation cannot be solved in quadratures. The development of the author’s approach in proving the theorem of the existence of moving singular points and solutions in the vicinity of a critical pole, based on a modified Cauchy majorant method, is given. An analytical approximate solution in the vicinity of a moving singular point is obtained, and an expression for the a priori error estimate is presented. A numerical experiment confirming the obtained theoretical results is provided. Full article

The brushless operation presented in this study is of an axial-flux wound-rotor synchronous machine (AFWRSM) which uses the third harmonic and the fundamental components of current. The proposed brushless AFWRSM utilizes a single inverter configuration; there are two windings on the rotor surface, i.e., field and harmonic windings, connected using a diode rectifier. The harmonic winding holds twelve poles, and the field winding consists of four poles, whereas the stator consists of a balanced three-phase, four-pole winding designed using 36 slots. A current source inverter (CSI) is utilized to inject both the fundamental and third-harmonic currents in the stator winding. This arrangement generates a third harmonic in the air-gap of the machine, which is used to induce voltages in the harmonic winding. The proposed AFWRSM brushless operation is validated using 3D finite element analysis (FEA). Full article

Recognized as the world’s “Third Pole”, the Qinghai–Xizang Plateau poses significant challenges to human health due to its harsh environment. With improved transportation and a tourism boom industry bringing over 90 million low-altitude residents to the plateau annually, hypoxia has become a critical concern. This study analyzes oxygen content data (2017–2022) together with environmental variables including elevation, temperature, precipitation, and vegetation cover, using the GeoDetector method to identify key drivers of near-surface oxygen distribution. Within the framework of disaster system theory, we evaluated the risk of hypoxia among short-term residents. Results show that the near-surface oxygen distribution across the plateau is primarily regulated by climatic and topographic factors. Interactions among environmental variables markedly enhance the explanatory power for spatial variation in oxygen content, with the coupled effects of humidity, atmospheric pressure, elevation, and temperature being especially pronounced. A high hypoxia hazard prevails across the plateau, particularly in the high-altitude western, northern, and central regions. The spatial distribution of hypoxia risk is strongly shaped by human activities, with high-risk zones clustering in densely populated towns, transportation corridors, and regions of intensive tourism. This results in a distinctive coexistence of “high hazard–low exposure” and “low hazard–high exposure” patterns. These findings provide scientific insights for tourism planning, health protection, and risk management in plateau regions. Full article

Load Frequency Control (LFC) is essential for ensuring frequency stability in modern power systems subject to load fluctuations, uncertainties, and increasing renewable penetration. This paper introduces a novel hybrid control framework that unifies H∞ stability guarantees, H₂ performance, and pole placement for transient shaping. Its originality is threefold. First, it models load variation as a measurable disturbance (D₁₂ = 0, D₂₁ ≠ 0), departing from the standard assumption of an unknown input. This enables a low-order H∞ controller that improves transient response, enhances robustness, and reduces energy consumption. Second, the framework explicitly accounts for a wider spectrum of real-world uncertainties, including governor and turbine dynamics and the transmission-line synchronizing power coefficient. Third, it integrates explicit energy optimization to reduce mechanical stress and extend equipment lifespan. This strategy yields substantial energy savings by minimizing fuel use and operational costs. Simulation results confirm its superiority: the proposed H∞/H₂ pole placement controller with measured disturbances achieves a 98% reduction in control energy relative to a standard H∞ controller, along with a 70% reduction in overshoot and a drastic improvement in settling time—from 7 s to 0.2 s—compared to a conventional H∞/H₂ controller. These results establish the proposed framework as a new benchmark for robust, efficient, and high-performance LFC design. Full article

Air pollution, particularly fine particulate matter (PM_2.5) and ozone (O₃) pollution, poses serious challenges to environmental quality and sustainable development. The Tibetan Plateau, often described as the “Third Pole,” functions as a key ecological shield for China and exerts wide-reaching influence on global climate systems, hydrological cycles, and cross-regional pollution transport. To better clarify the driving mechanisms of air pollution in this sensitive region, we propose an integrated MRG–HSW framework, which, for the first time, systematically couples statistical modeling and trajectory analysis by combining multivariate regression, residual-based screening, and HYSPLIT–WCWT trajectory analyses. Taking Qinghai Province as a case study, ERA5 and GDAS1 reanalysis products were coupled with in situ monitoring to identify the relative contributions of local emissions and long-range atmospheric transport. The results show that, in low-elevation zones, PM_2.5 levels are largely governed by local anthropogenic activities (R² = 0.631–0.803), whereas O₃ concentrations respond more strongly to meteorological variability (R² = 0.529–0.779). At higher elevations, however, local explanatory factors weaken, and long-range transport from the Hexi Corridor, Qaidam Basin, and even South Asia becomes the dominant influence for both pollutants. Additional sensitivity tests confirm that the framework performs robustly under diverse meteorological and seasonal conditions. Collectively, this work not only establishes a transferable methodology for source attribution in plateau environments but also underscores the pivotal role of the Tibetan Plateau in sustaining regional air quality and global environmental stability. Full article

Glaciers in High-Mountain Asia, the so-called “Third Pole,” are critical water sources but remain poorly monitored due to rugged topography and limited accessibility. We present an integrated approach that combines remote sensing with ground-based observations to model ice melt of the Passu Glacier (Pakistan) from 5 August to 13 October 2023. Meteorological data from two automatic weather stations and ablation measurements from four stakes were used together with satellite-derived albedo (Landsat 8 OLI), surface temperature (Landsat 9 TIRS), and topography (ALOS AW3D30 DSM) to implement an enhanced T-index melt model accounting for net shortwave and longwave radiation. Model performance was evaluated against station and satellite data and ablation stake measurements using leave-one-out cross-validation. The estimated total ice melt volume was 16 million m³ w.e. during the monitoring period, with an average melt of 3.60 m w.e. The model reproduced observed stake ablation with an uncertainty of 0.48 m w.e. (9% of average measured melt). Elevation was identified as the dominant melt driver (β = −0.501, unique R² = 0.199), with aspect and slope exerting secondary influences through their effect on solar radiation and shading. Our findings demonstrate that combining minimal but strategically located field data with satellite products provides a physically consistent and scalable framework for glacier melt estimation in data-scarce regions of the Third Pole, with relevance for hydrological monitoring and climate adaptation. Full article