Search Results (671)

An explicit coupled two-dimensional (2D) hydromechanical model (HMM) that can simulate discontinuous features in the foundation, as well as the effects of grout curtains and drainage systems, is employed to evaluate the influence of key parameters such as dam height, foundation behaviour, joint patterns, joint stiffness and strength, hydraulic apertures, and grout curtain permeability. A parametric sensitive study using four gravity dams, and a real case study of an operating dam are presented. The results presented show that dam height influences the relationship between water level in the reservoir and drain discharges, with higher dams showing more pronounced curved nonlinearity. The strength properties of the concrete–rock interface are also shown to have a meaningful influence on the HM response, especially for an elastic foundation and for higher dams, showing the need to properly characterize this interface through in situ testing. The joint aperture at nominal zero stress is shown to be the parameter with the most significant effect on the HM response. The results also show that a progressive degradation scenario of the concrete–rock interface or of the grout curtain permeability is easier to identify through the hydraulic measurements than in the mechanical displacement field. Full article

The Hisayamada Dam (22.5 m high, 75.4 m long), constructed in 1924 as a water supply facility, is a masonry arch–gravity concrete dam with a slender arch shape. Although it was the first theoretically designed arch-type dam in Japan, seismic forces were not considered at the time of construction. This study evaluates its seismic performance using a three-dimensional (3D) dynamic Finite Element Method (FEM) in accordance with current Japanese governmental guidelines. A detailed 3D model incorporating the dam body, surrounding topography, foundation, and reservoir was developed, and expected earthquake motions in three directions were applied simultaneously. The analysis showed that localized tensile stress exceeding the tensile strength occurred near the upstream heel of the dam base. However, these stress concentrations were limited to small regions and did not form continuous damage paths across the dam body. Based on the linear dynamic analysis and engineering judgment, the overall structural integrity and water storage function of the dam are considered to be maintained. Additional analyses were conducted by varying the elastic modulus of the foundation rock and dam concrete to clarify the influence of material stiffness on seismic response and stability. Full article

A conditional framework of Conditional Cosmological Recurrence (CCR) is introduced, as follows: if a causal patch admits a finite operational Hilbert space dimension D (as motivated by holographic and entropy bounds), then unitary quantum dynamics guarantee almost-periodic evolution, leading to recurrences. The central contribution is the explicit formulation of a micro-to-macro bridge, as follows: (i) finite regions discretize field modes; (ii) gravitational bounds cap entropy and energy; and (iii) the number of accessible states is finite, yielding CCR. The analysis differentiates global microstate recurrences (with double-exponential timescales in $S_{max}$) from operationally relevant coarse-grained returns (exponential in subsystem entropy), with conservative timescale estimates. For predictivity in eternally inflating settings, a causal-diamond measure with xerographic typicality and a single no-Boltzmann-brain constraint is employed, thereby avoiding volume-weighting pathologies. The scope is explicitly conditional: if future quantum gravity demonstrates $D=\infty$ for causal patches, CCR is falsified. Full article

The cosmological constant (CC, $\Lambda$) problem stands as one of the most profound puzzles in the theory of gravity, representing a remarkable discrepancy of about 120 orders of magnitude between the observed value of dark energy and its natural expectation from quantum field theory. This paper synthesizes two innovative paradigms—holographic naturalness (HN) and pre-geometric gravity (PGG)—to propose a unified and natural resolution to the problem. The HN framework posits that the stability of the CC is not a matter of radiative corrections but rather of quantum information and entropy. The large entropy $S_{\mathrm{dS}}\sim M_{\mathrm{P}}^2/\Lambda$ of the de Sitter (dS) vacuum (with $M_{\mathrm{P}}$ being the Planck mass) acts as an entropic barrier, exponentially suppressing any quantum transitions that would otherwise destabilize the vacuum. This explains why the universe remains in a state with high entropy and relatively low CC. We then embed this principle within a pre-geometric theory of gravity, where the spacetime geometry and the Einstein–Hilbert action are not fundamental, but emerge dynamically from the spontaneous symmetry breaking of a larger gauge group, SO($1,4$)→SO($1,3$), driven by a Higgs-like field ${\varphi }^A$. In this mechanism, both $M_{\mathrm{P}}$ and $\Lambda$ are generated from more fundamental parameters. Crucially, we establish a direct correspondence between the vacuum expectation value (VEV) v of the pre-geometric Higgs field and the de Sitter entropy: $S_{\mathrm{dS}}\sim v$ (or $v^3$). Thus, the field responsible for generating spacetime itself also encodes its information content. The smallness of $\Lambda$ is therefore a direct consequence of the largeness of the entropy $S_{\mathrm{dS}}$, which is itself a manifestation of a large Higgs VEV v. The CC is stable for the same reason a large-entropy state is stable: the decay of such state is exponentially suppressed. Our study shows that new semi-classical quantum gravity effects dynamically generate particles we call “hairons”, whose mass is tied to the CC. These particles interact with Standard Model matter and can form a cold condensate. The instability of the dS space, driven by the time evolution of a quantum condensate, points at a dynamical origin for dark energy. This paper provides a comprehensive framework where the emergence of geometry, the hierarchy of scales and the quantum-information structure of spacetime are inextricably linked, thereby providing a novel and compelling path toward solving the CC problem. Full article

The urban heat island (UHI) effect, intensified by rapid urbanization, necessitates the precise identification and mitigation of thermal sources and sinks. However, existing studies often overlook landscape connectivity and rarely analyze integrated source–sink networks within a unified framework. To address this gap, this research combines source–sink theory with the local climate zone classification to examine the spatiotemporal patterns of thermal characteristics in Fuzhou, China, from 2016 to 2023. Using morphological spatial pattern analysis, the minimum cumulative resistance model, and a gravity model, we identified key thermal source and sink landscapes, their connecting corridors, and barrier points. Results indicate that among built-type local climate zones, low-rise buildings exhibited the highest land surface temperature, while LCZ E and LCZ F were the warmest among natural types. Core heat sources were primarily LCZ 4, LCZ 7, and LCZ D, accounting for 19.71%, 13.66%, and 21.72% respectively, whereas LCZ A dominated the heat sinks, contributing to over 86%. We identified 75 heat source corridors, mainly composed of LCZ 7 and LCZ 4, along with 40 barrier points, largely located in LCZ G and LCZ D. Additionally, 70 heat sink corridors were identified, with LCZ A constituting 96.39% of them, alongside 84 barrier points. The location of these key structures implies that intervention efforts—such as implementing green roofs on high-intensity source buildings, enhancing the connectivity of cooling corridors, and performing ecological restoration at pinpointed barrier locations—can be deployed with maximum efficiency to foster sustainable urban thermal environments and support climate-resilient city planning. Full article

How to economically and effectively mobilize remaining oil and achieve carbon sequestration after water flooding in low-permeability, high-water-cut reservoirs is an urgent challenge. This study, focusing on Block Y of the Daqing Oilfield, employs numerical simulation to systematically reveal the synergistic influencing mechanisms of CO₂ flooding and geological storage. A three-dimensional compositional model characterizing this reservoir was constructed, with a focus on analyzing the controlling effects of key geological (depth, heterogeneity, physical properties) and engineering (gas injection rate, gas injection volume, bottom-hole flowing pressure) parameters on the displacement and storage processes. Simulation results indicate that the low-permeability characteristics of Block Y effectively suppress gas channeling, enabling a CO₂ flooding enhanced oil recovery (EOR) increment of 15.65%. Increasing reservoir depth significantly improves both oil recovery and storage efficiency by improving the mobility ratio and enhancing gravity segregation. Parameter optimization is key to achieving synergistic benefits: the optimal gas injection rate is 700–900 m³/d, the economically reasonable gas injection volume is 0.4–0.5 PV, and the optimal bottom-hole flowing pressure is 9–10 MPa. This study confirms that for Block Y and similar high-water-cut, low-permeability reservoirs, CO₂ flooding is a highly promising replacement technology; through optimized design, it can simultaneously achieve significant crude oil production increase and efficient CO₂ storage. Full article

To address the issues of high energy consumption and high carbon emissions associated with the steam injection development of ultra-heavy oil in China, technological exploration focusing on electrical heating and solvent substitution was conducted. Firstly, experiments on the heat transfer and temperature rise characteristics in the near-wellbore formation via electrical heating revealed its feasibility. Considering that ultra-heavy oil reservoirs in China suitable for Steam-Assisted Gravity Drainage (SAGD) have already been converted to SAGD production, and considering the certain safety risks of solvent extraction, a development strategy of SAGD—Electrical Heating Solvent Extraction—SAGD was formulated. A multi-stage drainage theoretical model coupling SAGD with electrical heating solvent extraction was established. The similarity criteria for 3D-scaled physical simulation of electrical-heating-assisted production were derived. Through three-stage (SAGD—Electrical Heating Solvent Extraction—SAGD) scaled physical simulation experiments, the development performance of converting a SAGD-developed reservoir to thermal solvent extraction was analyzed. Results indicate that the higher the oil content in the electrically heated wellbore and nearby formation, the faster the heat transfer rate. This confirmed the decision to conduct experiments on electrical-heating-assisted solvent extraction (without steam injection) in SAGD-developed reservoirs. After the SAGD steam chamber reaches the top, switching to electrical heating solvent extraction results in a drainage zone along the flanks of the horizontal section comprising: a high-temperature zone of vaporized solvent from electrical heating, a medium-low temperature oil dissolution zone from the solvent, and an untouched zone. Along the horizontal section, it is divided into a solvent chamber rising zone, a slow expansion zone, and a rapid expansion zone. Experiments confirmed that electrical heating can vaporize the solvent, continuously expanding the drainage chamber scale. Furthermore, the solvent continues to function in the subsequent SAGD stage, increasing the recovery factor from 64.4% to 71.2%, an improvement of 6.9%. The established multi-stage coupled drainage theoretical model, compared with experimental and analytical calculations, showed an overall agreement rate of 95.3%, and can be used for production prediction in electrical-heating-assisted solvent extraction composite recovery. Full article

This paper presents the detailed comparisons of solute macro-segregation pictures predicted by different meso-macroscopic simulations, based on the single-domain enthalpy–porosity approach coupled with distinct models of flow resistance in the two-phase zone. In the first, the whole zone is treated as a Darcy’s porous medium (EP model); in the other two, the columnar and equiaxed grain structures are distinguished using either the coherency point (EP-CP model) approach or by tracking a virtual surface of columnar dendrite tips (EP-FT model). The simplified 2D model of a solidifying cast in a centrifuge is proposed, and calculations are performed for the Pb-48wt. % Sn cast at various hypergravity levels and rotation angles. It is shown, in the example of Sn-10wt. % Pb alloy, that the predicted macro-segregation strongly depends on the mesoscopic model used, and the EP-FT simulation (validated with the AFRODITE benchmark) provides the most realistic solute inhomogeneity pictures. The EP-FT model is further used to investigate the impact of the hyper-gravity level and the cooling direction on the compositional nonuniformity developing in centrifuge casting. The hyper-gravity level visibly impacts the macro-segregation extent. The region of almost uniform solute distribution in the slurry zone rises with the increased effective gravity, though the solute channeling is more severe for higher gravity and rotation angles. A-channeling and V-channeling were observed for angles between the gravity vector and cooling direction lower than 120° and higher than 120°, respectively. Full article

Spaceflight induces a wide array of effects on the human body, notably including pathological changes mediated by alterations in gravity. Abnormalities in the formation of primary cilia (ciliogenesis) can lead to cell cycle arrest and decreased epithelial cell proliferation, thereby delaying wound healing. To investigate the effect of microgravity on ciliogenesis in bronchial epithelial cells, we used a 3D clinostat to generate simulated microgravity (SMG) conditions. When BEAS-2B bronchial epithelial cells were exposed to SMG for 72 h, their proliferation was significantly reduced. The expression of Ki-67, which is not expressed in the G0 phase, decreased under SMG. Conversely, the expression of p27, which is expressed in the G0 and G1 phases, increased under SMG. These results suggest that SMG led to an increase in the number of cells in the quiescent phase. When the mRNA expressions of ARL13B (a marker of cilia assembly) and disassembly-related genes (Aurora A, NDE1, HDAC6, and DVL2) were evaluated, SMG upregulated ciliary assembly markers and downregulated disassembly markers. In addition, SMG increased the cilia length and number of ciliated cells. These findings suggest that SMG contributes to reduced cell proliferation through cell cycle arrest by disrupting normal ciliogenesis. Our findings indicate that SMG could delay lung injury by decreasing cell proliferation. Full article

This paper proposes a new simple method for generating fractal-like aggregates in 2D real spaces. The idea is to use an initial fractal aggregate and simulate a Gravity-based attraction from a distant point (using a gravity attractor with a large mass, but without volume). A Diffusion-Limited Aggregation (DLA) procedure is then applied by considering a single particle situated in the gravity attractor, with a minimum distance $R_a$ for deciding between aggregation or no aggregation. The final aggregates obtained are completely new fractal-like aggregates (images or structures). We analyze the fractal-like generated images obtained with the proposed method, considering different configurations and parameters in the simulations, including different initial fractals, different minimum distances $R_a$, etc. We also analyze the fractal dimensions of some of the new aggregates constructed by the proposed Gravity-based DLA simulation method. Full article

This study aimed to establish the optimal mix proportions for eco-friendly lightweight boards based on Ground Granulated Blast-furnace Slag (GGBFS) and waste rock wool using Response Surface Methodology (RSM). The investigation focused on optimizing three key properties: flexural failure load (Y₁), moisture content (Y₂), and specific gravity (Y₃). ANOVA results identified Binder and Perlite as the most dominant and statistically significant factors, exhibiting critical conflicting effects necessary for balancing strength and lightweight goals. Wollastonite showed a non-linear effect on flexural strength, peaking at an intermediate level. A Response Optimization simulation, targeting a minimum flexural load of 400 N, moisture content of 2.0%, and specific gravity of 0.80, yielded an optimal mix proportion: Binder 52.12%, Perlite 48.45%, and Wollastonite 7.37%. This blend achieved a high Composite Desirability (D) of 0.8725. Experimental verification confirmed the model’s reliability. The measured flexural load (408.54 N) successfully exceeded the 400 N target, and all measured values exhibited a low error margin (under 7%) compared to the predicted values. This optimized mix proportion provides a reliable foundation for developing high-performance, sustainable lightweight construction materials. Full article

The canonical quantization of gravity in general relativity is greatly simplified by the artificial decomposition of space time into a 3 + 1 formalism. Such a simplification appears to come at the cost of general covariance. This quantization procedure requires tangential and perpendicular infinitesimal diffeomorphisms generated by the symmetry group under the Legendre transformation of the given action. This gauge generator, along with the fact that Weyl curvature scalars may act as “intrinsic coordinates” (or a dynamical reference frame) that depend only on the spatial metric ($g_{ab}$) and the conjugate momenta ($p^{cd}$), allows for an alternative approach to canonical quantization of gravity. In this paper, we present the tensorial solution of the set of Weyl scalars in terms of canonical phase-space variables. Full article

We resume our analysis of Newtonian Fractional-Dimension Gravity (NFDG), an alternative gravitational model that does not require the dark matter (DM) paradigm. We add three more galaxies (NGC 6946, NGC 3198, NGC 2841) to the catalog of those studied with NFDG methods. Once again, NFDG can successfully reproduce the observed rotation curves by using a variable fractional dimension $D\left(R\right)$, as with the nine other galaxies previously studied with these methods. In addition, we introduce a mass-dimension field equation for our model, which is capable of deriving the fractional mass dimension $D_m\left(R\right)$ from a single equation, as opposed to the previous $D\left(R\right)$, which was obtained simply by matching the experimental rotational velocity data for each galaxy. While the NFDG predictions computed with this new $D_m\left(R\right)$ dimension are not as accurate as those based on the original $D\left(R\right)$, they nevertheless confirm the validity of our fractional-dimension approach. Three previously studied galaxies (NGC 7814, NGC 6503, NGC 3741) were analyzed again with these new methods, and their structure was confirmed to be free from any dark matter components. Full article

In this work, we discuss the conditions that allow the establishment of an equivalence between $f(R,T)=R+\lambda h\left(T\right)$ gravity models and General Relativity (GR) coupled to a modified matter sector. We do so by considering a D-dimensional spacetime and the matter sector described by nonlinear electrodynamics and/or a scalar field. We find that, for this particular family of models, the action and field equations can indeed be written in terms of a modified matter source within GR. However, when several matter sources are combined, this interpretation is no longer possible if $h\left(T\right)$ is a nonlinear function, due to the emergence of crossed terms that mix together the scalar and vector sectors. Full article

Local governments assume the crucial responsibility of advancing regional environmental regulation and protection and fostering green innovation in development. This paper takes the provincial-level data from 2007 to 2018 in China, and investigates how government environmental protection expenditure (GEPE) influences regional green innovation. Also, a gravity model is constructed to figure out R&D element flow, and the moderating mechanisms of the flow of R&D personnel and R&D capital are further examined. The empirical evidence shows that GEPE significantly promotes regional green innovation (coefficient = 0.185, p < 0.01), with robustness confirmed through lagged effect tests, indicating sustained positive impact. Mechanism analysis indicates that R&D personnel flow significantly strengthens the positive effect of GEPE on regional green innovation (interaction coefficient = 0.016, p < 0.01), while the moderating effect of R&D capital flow is statistically insignificant. The spatial Durbin model further confirms that the impact of GEPE on green innovation has a spatial spillover effect in neighboring regions. Additionally, excessive environmental decentralization suppresses the positive influence of GEPE on regional green innovation. These findings provide empirical evidence for local governments to promote regional green innovation through fiscal expenditures. It emphasizes the necessity of giving full play to the guiding and “leveraging” role of government environmental governance expenditure while fostering a synergistic effect between government environmental protection expenditure and the free flow of R&D elements, ultimately promoting coordinated green development in regions. Full article