58 research outputs found
Inception of Regular Valley Spacing in Fluvial Landscapes: A Linear Stability Analysis
No full textIncipient valley formation in mountainous landscapes is often associated with their presence
at a regular spacing under diverse hydroclimatic forcings. Here we provide a formal linear stability
theory for a landscape evolution model representing the action of tectonic uplift, diffusive soil creep, and
detachment-limited fluvial erosion. For configurations dominated by only one horizontal length scale, a single
dimensionless quantity characterizes the overall system dynamics based on model parameters and boundary
conditions. The stability analysis is conducted for smooth and symmetric hillslopes along a long mountain
ridge to study the impact of the erosion law form on regular first-order valley formation. The results provide
the critical condition when smooth landscapes become unstable and give rise to a characteristic length scale for
incipient valleys, which is related to the scaling exponents that couple fluvial erosion to the specific drainage
area and the local slope. The valley spacing at first instability is uniquely related to the ratio of the scaling
exponents and widens with an increase in this ratio. We find compelling evidence of sediment transport by
diffusive creep and fluvial erosion coupled with the specific drainage area equation as a sufficient mechanism
for first-order valley formation. We finally show that the predictions of the linear stability analysis conform
with the results of numerical simulations for different degrees of nonlinearity in the erosion law and agree well
with topographic data from a natural landscape
Soil Structure and Mixing Controls on Water‐Rock Contact: Implications for Enhanced Weathering
No full textEnhanced weathering (EW), the addition of finely ground silicate rock powder (RP) to soil, has
emerged as a promising carbon removal strategy. However, quantifying weathering rates in soils remains
challenging, as most continuum‐scale EW models do not adequately account for the fraction of RP surface area
(SA) that is wet at a given soil moisture and thus actively weathering. Here, we study how soil pore structure, RP
particle size distribution, and RP mixing degree within the soil control water‐rock contact. Using a soil‐physics‐
based framework, we derive a scaling factor that quantifies the wet fraction of RP SA as a function of soil
moisture and mixing degree within soil pores. This scaling factor varies nonlinearly with soil moisture for
typical soil pore structures and RP particle size distributions, countering previous zero‐order (independent of
soil moisture) or linear assumptions. The scaling factor evolves dynamically with hydrological fluctuations and,
for a given pore structure and RP mixing degree, it can span nearly two orders of magnitude with changes in
median particle size. To illustrate its application, we integrate the derived scaling factor into the Soil Model for
Enhanced Weathering and examine the sensitivity of simulated weathering fluxes to mixing degree under
otherwise identical conditions. Under low mixing, results show that average weathering rates are roughly two
orders of magnitude lower than under perfect mixing over 1 year of application. Our work provides a
mechanistic, computationally efficient framework for representing water‐rock contact in soil, offering a
pathway to improve continuum‐scale EW models
Comment on “Groundwater Affects the Geomorphic and Hydrologic Properties of Coevolved Landscapes” by Litwin et al.
No full textThe objective of this comment is to correct two sets of statements in Litwin et al. (2022, https://doi.org/10.1029/2021JF006239), which consider our research work (Bonetti et al., 2018, https://doi.org/10.1098/rspa.2017.0693; Bonetti et al., 2020, https://doi.org/10.1073/pnas.1911817117). We clarify here that (a) the specific contributing area is defined in the limit of an infinitesimal contour length instead of the product of a reference contour width (Bonetti et al., 2018, https://doi.org/10.1098/rspa.2017.0693), and (b) not all solutions obtained from the minimalist landscape evolution model of Bonetti et al. (2020, https://doi.org/10.1073/pnas.1911817117) are rescaled copies of each other. We take this opportunity to demonstrate that the boundary conditions impact the obtained solutions, which has not been considered in the dimensional analysis of Litwin et al. (2022, https://doi.org/10.1029/2021JF006239). We clarify this point by using dimensional analysis and numerical simulations for a square domain, where only one horizontal length scale (the side length l) enters the physical law.CHANG
Self-similarity and vanishing diffusion in fluvial landscapes
No full textComplex topographies exhibit universal properties when fluvial erosion dominates landscape evolution over other geomorphological processes. Similarly, we show that the solutions of a minimalist landscape evolution model display invariant behavior as the impact of soil diffusion diminishes compared to fluvial erosion at the landscape scale, yielding complete self-similarity with respect to a dimensionless channelization index. Approaching its zero limit, soil diffusion becomes confined to a region of vanishing area and large concavity or convexity, corresponding to the locus of the ridge and valley network. We demonstrate these results using one dimensional analytical solutions and two dimensional numerical simulations, supported by real-world topographic observations. Our findings on the landscape self-similarity and the localized diffusion resemble the self-similarity of turbulent flows and the role of viscous dissipation. Topographic singularities in the vanishing diffusion limit are suggestive of shock waves and singularities observed in nonlinear complex systems
Representing the form and formation of Earth’s topography under natural and anthropogenic drivers
No full textWhile the Earth's topography may appear static at a casual glance, it is continuously shaped by diverse geomorphic processes operating across various spatial and temporal scales. These processes leave distinctive spatial patterns of ridges and valleys on natural terrains, influencing the flow and availability of water, energy, and nutrients across the surface and subsurface, thereby impacting overall ecosystem functionality. Given the pivotal role of Earth's dynamic topography, a key question emerges: How do different surface processes transform the land surface, and how can we effectively quantify these changes?
In pursuit of this question, this dissertation utilizes a minimal process-based modeling approach, with the use of analytical and numerical methods, dimensional analysis, and model output comparisons with observational data to elucidate the interplay of these geomorphic processes and landform changes. We analyze the effects of hillslope processes of soil creep and landslide erosion in creating smooth, convex to planar hillslope profiles, in contrast to surface runoff, which generates intricate branching patterns of ridges and valleys as it intensifies. In the final section of this thesis, we transition from a geomorphic perspective to a practical examination of soil erosion within human timescales. We evaluate existing experimental methodologies for estimating erosion rates and analyze empirical soil erosion models from a physics-based perspective of sediment transport
Navigating challenges for supply chain transparency in the digital enterprises
No full textPurpose:
In the age of digital businesses, the rise of innovative digital transformation has made supply chain transparency (SCT) an essential research topic. While digital technologies provide possibilities for enhancing transparency in supply chains, there is limited research on how digital businesses overcome different SCT issues or provide real-time visibility and traceability. This research investigates the different challenges of transparency in supply chains for digital businesses in the age of digital transformation.
Design/methodology/approach:
Challenges are identified through a comprehensive literature review and finalized through the fuzzy-Delphi method (FDM) after industry experts’ validation. Data is gathered, ranked and prioritized through the analytic hierarchy process (AHP) entropy method.
Findings:
The study reveals that challenges related to data privacy and security, supplier resistance, and lack of data standardization grouped under Cluster 1 (Critical Digital Friction Points) pose the most significant barriers to supply chain transparency in digital enterprises. These are followed by Cluster 2 (Operational Capability Gaps) and Cluster 3 (External and Strategic Constraints), highlighting a clear prioritization framework for addressing SCT issues in a structured, phased manner.
Implications: By leveraging advanced digital technologies to gather, share, and analyze supply chain data, digital enterprises can overcome these challenges, enhance operational effectiveness, and gain stakeholders' trust. These findings can be utilized by policymakers to develop guidelines that enhance transparency while maintaining data security. Practitioners can develop targeted strategies to address supplier resistance and infrastructure deficiencies.
Originality:
This study makes three distinct contributions. Firstly, it fills a gap in current literature by initiating a clear debate on supply chain transparency beyond generic or sustainability-focused models, illuminating its unique dimensions in digital enterprises. Secondly, it demonstrates the practical importance of SCT by identifying and prioritizing the key challenges that are faced by digitally transforming companies. Thirdly, it advances theory by contrasting traditional perspectives with new insights drawn from our findings, offering both actionable guidance and novel conceptual frameworks for transparency in digitally enabled supply chains
A Delay-Tolerant low-duty cycle scheme in wireless sensor networks for IoT applications
No full textEnergy efficiency is an existing research challenge in wireless sensor networks (WSNs); to make WSNs energy efficient, many researchers moved to low-duty cycle WSNs with different data forwarding schemes. Low-duty cycle is considered to be a promising approach to design routing protocols for resource-constrained WSNs. Many applications have real-time constraints, which requires an event must be reported to the sink before deadline. Furthermore, wireless links between low-power radios are highly unreliable, and end-to-end latency requirements are challenging due to multiple transmissions for a single packet delivery. By considering probabilistic delay (i.e., delay bounded data delivery with reliability constraints) and energy efficiency issues, little research has been done using different data forwarding schemes, but still, the problem exists. In this work, two strategies are proposed for data forwarding: an energy-optimal path and a delay-optimal path. The early-arrived packet follows an optimal energy route and a diverse path to achieve a delay guarantee with minimum transmission cost. The proposed scheme improves the performance of low-duty cycle WSNs in terms of delay, reliability, stability, and transmission cost. It is observed that under different low-duty cycles, the proposed scheme achieves up to 25% energy conservation compared with both MinEEC and MinEED. At last, undirected spanning trees are considered to balance communication costs. The simulation results of the proposed scheme are compared with the existing methods
Smallest eigenvalue density for regular or fixed-trace complex Wishart–Laguerre ensemble and entanglement in coupled kicked tops
No full text
Inception of Regular Valley Spacing in Fluvial Landscapes: A Linear Stability Analysis
No full textIncipient valley formation in mountainous landscapes is often associated with their presence at a regular spacing under diverse hydroclimatic forcings. Here we provide a formal linear stability theory for a landscape evolution model (LEM) representing the action of tectonic uplift, diffusive soil creep, and detachment-limited fluvial erosion. For configurations dominated by only one horizontal length scale, a single dimensionless quantity characterizes the overall system dynamics based on model parameters and boundary conditions. The stability analysis is conducted for smooth and symmetric hillslopes along a long mountain ridge to study the impact of the erosion law form on regular first-order valley formation. The results provide the critical condition when smooth landscapes become unstable and give rise to a characteristic length scale for incipient valleys, which is related to the scaling exponents that couple fluvial erosion to the specific drainage area and the local slope. The valley spacing at first instability is uniquely related to the ratio of the scaling exponents and expands logarithmically with an increase in this ratio. We find compelling evidence of sediment transport by diffusive creep and fluvial erosion coupled with the specific drainage area equation as a sufficient mechanism for first-order valley formation. We finally show that the predictions of the linear stability analysis conform with the results of numerical simulations for different degrees of nonlinearity in the erosion law and agree well with topographic data from a natural landscape.CHANG
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