National Taiwan Ocean University

In this study, a self-regularized approach was employed to determine the thermal stress in a free-free truss, which results in a singular stiffness matrix. Physically, the stiffness and flexibility matrices of structure with proper constraints are mutually inverse to each other. However, they are not invertible for a free-free truss from the mathematical point of view if the generalized inverse is not considered. To deal with the problem, the self-regularized approach is utilized to find the generalized flexibility matrix, which are the submatrices of the inverse of the bordered matrix for the singular stiffness matrix. The validity of this approach was confirmed through different methods such as the generalized inverse and Moore–Penrose inverse. Two analytical examples of continuous system, a rod and a beam, were given to demonstrate that the obtained inverse satisfy the Moore–Penrose inverse. Numerically speaking, two illustrative examples of a discrete system, a three-bar simple truss and a six-bar complex truss subject to uniform and nonuniform temperature change were provided. Three-bar simple truss yielded zero thermal stress under all conditions, whereas the six-bar complex truss produced thermal stress under nonuniform temperature change. The study also employed ABAQUS software for numerical analysis to validate previous results.

Understanding the origin of high-frequency stratigraphic heterogeneity in active orogenic basins is essential for distinguishing the relative contributions of regional tectonics and local environmental forcings. In the offshore areas of central Taiwan, the Early Pleistocene to present Toukoshan Formation exhibits complex architectural variations that challenge singular tectonic interpretations. This study utilizes multichannel seismic reflection profiles and borehole data to dissect the evolutionary mechanisms driving these stratigraphic shifts. While the underlying Late Miocene to Early Pleistocene sequences exhibit architectural stability as well-stratified reflections, the Toukoshan Formation marks a transition to highly discontinuous geometries, reflecting a switch in dominant drivers toward localized hydrodynamic forcing. The lower Toukoshan Formation features co-existing parallel and progradational clinoform geometries, indicating significant lateral variations. These progradational structures are vertically overlain by continuous, sub-parallel reflections, recording a low-to-high-to-low energy transition. While tectonic subsidence typically produces laterally continuous stratigraphic geometries, the observed progradational sets in this study exhibit marked vertical and lateral discontinuities. This suggests that localized stratigraphic architecture is decoupled from the gradual tectonic trend, reflecting a switch in dominant drivers toward rapid hydrodynamic forcing. Such features likely record wave-driven sediment redistribution and the development of localized barrier complexes under high-energy conditions during relative sea-level fluctuations, rather than being a direct response to tectonic loading. Correlation of key time horizons across multiple seismic profiles reveals a southward migration of the depocenter within the Toukoshan Formation. This spatial pattern is consistent with the southward propagation of the orogenic belt and the resulting higher subsidence rates in the south as noted in previous studies, indicating that such regional-scale sediment redistribution is primarily governed by foreland basin subsidence. Our findings reveal a decoupling of stratigraphic drivers: while isopach maps confirm sustained tectonic control over regional accommodation, the internal architecture of the Toukoshan Formation marks a switch to localized hydrodynamic forcing. Wave-driven sediment supply and reworking overrides the tectonic signal, creating high-frequency heterogeneity and proving that even under active tectonics, environmental energy can be the primary sculptor of the depositional landscape.

Land subsidence driven by intensive groundwater abstraction remains a major concern in Taiwan, particularly in Yunlin County. This study integrates multidisciplinary observations with artificial intelligence (AI)-driven modeling to support land-subsidence management. A hydrogeological conceptual model was developed to simulate groundwater-level dynamics and aquifer-system compaction, and an AI approach was used to capture the nonlinear relationship between groundwater fluctuations and soil-layer compression. Results indicate that subsidence is influenced by climate extremes and pumping intensity. The strong positive correlation and synchronized temporal variations between groundwater level and soil compression suggest a coupled hydro-mechanical response. To identify mitigation measures, five scenarios were evaluated, focusing on crop conversion and pumping regulation. Compared with current pumping conditions, both crop conversion and rotational pumping reduce groundwater drawdown and associated compression. Among the alternatives, conversion to sweet potato combined with rotational pumping yields the smallest drawdown, indicating a practical pathway for sustainable groundwater management and land-subsidence mitigation.