This paper introduces a novel voltage-controlled second-order discrete memristor with two internal state variables and a locally active operating region, designed to enrich memory-dependent nonlinear dynamics beyond conventional first-order devices. Power-off plot analysis reveals distinct stability properties for the internal states, where one state exhibits volatile behavior, while the other is non-volatile, resulting in a hybrid short- and long-term memory mechanism. This coexistence of volatile and persistent memory enhances the dynamical flexibility of the device. As an application, the memristor is employed as a synaptic element to couple two Chialvo neuron maps, forming a memristively coupled neural system with increased dimensionality and complexity. The collective dynamics are investigated using bifurcation diagrams, Lyapunov exponents, and time-series analysis, revealing resting, periodic, quasi-periodic, chaotic, and hyperchaotic regimes, as well as pronounced multistability and hysteresis. Parameter mismatch between neurons enlarges chaotic regions and produces diverse firing patterns, while synchronization is mainly observed in simple dynamical states. In addition, intermittent large-amplitude spikes that do not satisfy conventional extreme-event criteria are identified and characterized as quasi-extreme dynamics. The influence of additive noise is also examined, demonstrating noise-induced spiking and transitions from periodic to chaotic behaviors. These results show that second-order memristive coupling provides a flexible framework for generating rich neural dynamics, with potential applications in neuromorphic computing and memory-based nonlinear circuits.
Can Gio District in southern Vietnam, including the Can Gio Biosphere Reserve and the urbanized beaches of Can Thanh Town, is a rapidly developing coastal area facing increasing pressures from marine plastic pollution. This study compared beach litter monitoring using 1 m × 1 m quadrats with in situ collection against smartphone imagery captured via the Mergin Maps app and later annotated in DotDotGoose. Mergin Maps was selected because it provides an open‑source, smartphone‑based GIS platform for rapid, low‑cost capture of georeferenced quadrat images, which is more feasible for routine monitoring in resource‑limited coastal settings than drone surveys or fully manual transect methods. Across four sandy beaches, at Bui Lam Beach field surveys recorded 399 items, while image-based analysis detected 410 items; at Bui Lam-Tac Xuat Beach, field surveys recorded 212 items, compared with 236 from image-based analysis, indicating strong tidal influence and clam farming activities at these sites. At Can Thanh Park, 189 items were counted in the field compared with 149 items in images, whereas at Tac Xuat, a tourist beach with regular cleanups, 82 and 71 items were recorded by field and image-based methods, respectively. Overall litter densities exceeded 10 items m⁻2 for both methods, and plastics accounted for more than 96
Neptunia oleracea Lour., commonly known as “Yellow Pan Weed, Water Mimosa or Water Sensitive Plant”, is a wild aquatic plant of the genus Neptunia in the family Fabaceae, and its parts can be used as food and in medicine. With further exploration, its applications are found in various fields, including food, agriculture, and medicinal herbs. This review summarizes traditional knowledge by integrating it with scientific evidence related to N. oleracea’s phytochemical compounds, pharmacological activities, and therapeutic potential. This narrative review analyzed 50 documents from databases, including Web of Science, Scopus, Google Scholar, ScienceDirect, SpringerLink, PubMed, and other online databases (1790–2025), focusing on articles and textbooks on N. oleracea’s botany, nutritional benefits, traditional uses, phytochemistry, and pharmacological properties. 54 metabolites, including pheophorbides, phenolics, flavonoids, and other compounds, were found in N. oleracea. The extracts from N. oleracea parts and its isolated compounds have been shown to possess various biological properties, including antioxidant, antimicrobial, anti‐inflammatory, analgesic, anticancer, antiulcer, astringent, anti-5α-reductase, and anti-diabetic activities. These pharmacological properties are closely associated with the presence of phenolic compounds, particularly flavonoids. Various parts of N. oleracea contain nutritional components, minerals, and vitamins. Although some evidence supports the link between traditional uses and modern pharmacology, significant knowledge gaps still hinder its integration into evidence-based clinical applications. In the future, prioritizing large-scale clinical studies and developing combination formulations will further elucidate and expand the therapeutic potential of N. oleracea.
Energy harvesting (EH)-enabled multi-input multi-output (MIMO) short-packet communication (SPC) employs the recent advanced technologies such as radio frequency EH, SPC, and MIMO processing, targeting high energy efficiency, strong reliability, enhanced spectrum efficiency, and low latency. Moreover, nonorthogonal multiple access (NOMA) can further boost reliability and spectral efficiency by successive interference cancellation (SIC). Under SIC, information of one NOMA user is decoded by others. Thereby, the question arises when NOMA users are untrusted, which eavesdrop information of others, how their information is secured in EH-enabled MIMO SPC (EHMIMOSPC). This open problem is solved in this paper with the proposal of an analytical framework presenting the secrecy evaluation for untrusted NOMA users in EHMIMOSPC under practical conditions of nonlinear EH, imperfect SIC and imperfect channel state information. Monte-Carlo simulation validates this analytical framework and exposes understandings on the effects of key parameters on the secrecy capability of EHMIMOSPC with NOMA. Also, this paper considers EHMIMOSPC with orthogonal multiple access (OMA). The findings show that NOMA is worse than OMA in EHMIMOSPC, which is contradictory to long-packet communication.
For a long time, the Lorenz system has been a typical example for understanding the limits of nonlinear instability and predictability in atmospheric dynamics. In this study, we propose and examine a five-dimensional generalized Lorenz model in which the traditional constant heating parameter is replaced by a sinusoidal heating function, thereby accounting for periodically fluctuating thermal input. The additional dynamic variables describe secondary convective modes linked to multilayer heat transport. This means that there are more possible behaviors than in the classical three-dimensional model. We analyze the system’s symmetry, dissipativity, equilibrium structure, and local stability, and explore its intricate dynamics using one- and two-parameter bifurcation diagrams, Lyapunov exponents, and the Kaplan–Yorke dimension. The results show multiple attractors, multistability, and transitions between equilibrium, periodic, and chaotic regimes driven by crises. These results demonstrate that periodic thermal forcing can alter attractor geometry and trigger abrupt qualitative changes in system behavior, thereby affecting atmospheric regime shifts and constraints on predictability. The research emphasizes the influence of dimensionality and time-dependent heating on the configuration of chaotic convection models.
