Influence Of Topographic Features Research Articles

The effect of covariates on Soil Organic Matter and pH variability: a digital soil mapping approach using random forest model

ABSTRACT This research focuses on understanding the spatial variation of Soil Organic Matter (SOM) and pH levels in the North of Morocco. The study employs a comprehensive approach to enhance predictive modelling, incorporating the Boruta algorithm for effective environmental covariates selection and optimizing model parameters through hyperparameter optimization. Utilizing a Random Forest (RF) model with remote sensing indices and topographic features, the research predicts SOM and pH to identify key contributors to their spatial variability. SOM prediction saw significant success, with a notable correlation to remote sensing indices such as the RVI, NDVI, and TNDVI. These indices, indicative of vegetation health and productivity, emerged as primary influencers of SOM. In comparison, the influence of topographic features like elevation, slope, and aspect was found to be less significant. Conversely, predicting pH was challenging due to the minimal spatial variability within the dataset. Addressing this limitation could involve dataset expansion or alternative models for low-correlated data handling. Despite the RF model’s limited efficacy in pH prediction, an observable correlation between SOM and pH was identified, consistent with prior research. Areas with higher SOM exhibited lower pH values, indicating relative soil acidification from organic matter decomposition. The study’s RF model demonstrated potential in SOM prediction using remote sensing indices, but enhancing pH prediction is essential. Future research may explore dataset expansion, diverse sampling, or testing alternative predictive models for better performance with low-correlated datasets. The study offers valuable insights for advanced predictive model development and enriches understanding of soil management practices.

Analysis of Information Transmission Characteristics Based on Adaptive Ground Electrode Current Field

The information transmission mechanism of the ground electrode current field uses a very low-frequency electrical signal, which is applied to the two electrodes driven into the soil layer or the collapsed body of the tunnel to form a current field in the rock layer or soil layer. Signal detection is created via the strong penetration of wireless information transmission. This research focuses on various electromagnetic effects, such as polarization, magnetization, and the transmission of electromagnetic waves under the influence of different media, such as rock, sand, reinforced concrete, and air voids. The influence of these adaptive electromagnetic effects on the transmission of electromagnetic waves is mainly reflected in the reflection, refraction, and attenuation of electromagnetic wave signals. The inhomogeneity of the earth medium, the influence of topographic features, and multi-path transmission all cause signal distortion, fading, or changes in the direction of electromagnetic wave propagation. By studying the three physical quantities of magnetic permeability, permittivity, and conductivity, the electromagnetic characteristics of the earth medium are described to research the information transmission characteristics of the earth electrode current field.

Assessing Numerical Model Skill at Simulating Coastal Flooding Using Field Observations of Deposited Debris and Photographic Evidence

Despite the growing range and availability of resources to support coastal flood hazard model development, there is often a scarcity of data to support critical assessment of the performance of community-scale coastal inundation models. Even where long-term tide gauge measurements are available in close proximity to the study area, the records provide little insight into the spatial distribution and limits of overland flooding, or the influence of topographic features and structures on flooding pathways. We present methods to support the assessment of model performance using field observations in lieu of, or supplementary to, conventional water-level records. A high-resolution, numerical coastal flood hazard model was developed to simulate storm surge-driven flooding in the Acadian Peninsula region of New Brunswick, Canada. Owing to the remoteness of the study area from tide gauge stations, model performance was assessed based on a comparison with field measurements of deposited wrack and debris, as well as photographic and video evidence of coastal flooding, for two significant storm surge events in recent history. Our research findings illustrate the value of observational and qualitative data for characterizing coastal flood hazards, lending gravity to the importance of non-conventional data sources, particularly in data-scarce regions.

Influence of topographic features and stream network structure on the spatial distribution of hydrological response

Topographic data and geomorphological characteristics are recognized as significant factors that affect the hydrological response of a river basin. There have been a variety of lumped or semi-distributed hydrological models developed based on the use of geomorphological parameters. However, the possibility of applying geomorphological factors to describe the temporal and spatial distribution of hydraulic variables in a watershed is still questioned. This study focuses on thoroughly exploring the relationship between watershed topography and two variables, the water depth and discharge. Machine learning (ML) techniques are utilized to predict the spatial distribution of the two hydraulic variables based on geomorphological factors. To enhance the overall predicted accuracy, the structure and unique distribution of the stream network exiting a river basin are investigated for use in modifying the training procedure of the ML model. A novel method of data classification according to the stream network structure and cluster analysis is established to reinforce the capability of predicting hydraulic variables. Application results of two river basins in Taiwan island show that the performance of water depth and discharge predictions are satisfactory as long as the data classification is conducted for model training. Therefore, the ML-based model developed in this study is a promising way to replace the fully distributed numerical model in order to improve executing efficiency and bypass any problem of instability.

Influence of topographical features on the surface appearance measurement of injection moulded components

Adding textures to surfaces is known to improve the external appearance of injection moulded components. However, when high surface quality is required, normally a paint coating is applied on top of the moulded textured surface. In this work, an alternative to painting for obtaining high quality surfaces is proposed, following an environmental-friendly process and having low production cost. Three different surface textures obtained by injection moulding have been characterized and compared with a painted one. Alternative topographical parameters such as the absolute functional height (AFH), the functional height distribution (FHD), texture slope (TS) or texture aperture angle (TAA) besides to the traditional roughness parameters such as the arithmetical mean height (Sa) and the root mean square height (Sq) have been utilized to characterize the random surface textures. The relationships between these parameters and the surface quality appearance represented by gloss and reflectivity contrast have been established using a new total appearance measurement (TAM) apparatus. It was found that by applying secondary operation on the textured mould cavity, such as adding micro roughness features or coatings, equal apparent quality to the ones obtained by painting can be reached.

Interactive Effects of Breed, Physiological Conditions and Topography on Grazing Behaviour and Distribution of Dairy Cattle at Mpwapwa

The study was carried out at Mpwapwa Livestock Training Agency (LITA) Dairy unit during dry season to examine the interactive effect of dairy cattle breeds and their physiological condition on grazing behaviour and the influence of topographical features on grazing distribution. The experimental design involved 2x3 factorial arrangements with two factors; breed (Friesian, Ayrshire and Jersey) and physiological status (dry, weaners and lactating). Focal observation method was used by three trained observers to examine focal animals for four days consecutively. Field survey techniques were used for recoding different signs of animals’ movement from upper-land and lowland. It was revealed that the time spent for foraging was inversely proportion to the time spent for rumination; grazing being higher for Friesian and Ayrshire breeds and significantly lower for Jersey breed. Interestingly, lactating cows had significantly lower feeding rate which was associated with concentrate supplementation. More studies are recommended not only to determine the impacts of supplementation on production levels but also economic implication of supplementation. Moreover, Friesian and Jersey displayed higher feeding rate at weaning stage and drying-off period respectively which implies the complex interrelationship between genomic characteristics and physiology of animals and thus calls for indepth studies. Nevertheless, a preferential choice of grazing animals in lowland has ecological implication by increasing grazing pressure on lowland pastures. Appropriated range management practices such as proper stocking rate, water point distribution and pasture improvement are recommended. Further studies are also recommended to examine nutritional composition and seasonal variation in forage resources.

Engineering stem cell cardiac patch with microvascular features representative of native myocardium.

The natural myocardium is a highly aligned tissue with an oriented vasculature. Its characteristic cellular as well as nanoscale extracellular matrix (ECM) organization along with an oriented vascular network ensures appropriate blood supply and functional performance. Although significant efforts have been made to develop anisotropic cardiac structure, currently neither an ideal biomaterial nor an effective vascularization strategy to engineer oriented and high-density capillary-like microvessels has been achieved for clinical cardiovascular therapies. A naturally derived oriented ECM nanofibrous scaffold mimics the physiological structure and components of tissue ECM and guides neovascular network formation. The objective of this study was to create an oriented and dense microvessel network with physiological myocardial microvascular features.Methods: Highly aligned decellularized human dermal fibroblast sheets were used as ECM scaffold to regulate physiological alignment of microvascular networks by co-culturing human mesenchymal stem cells (hMSCs) and endothelial cells (ECs). The influence of topographical features on hMSC and EC interaction was investigated to understand underlying mechanisms of neovasculature formation.Results: Results demonstrate that the ECM topography can be translated to ECs via CD166 tracks and significantly improved hMSC-EC crosstalk and vascular network formation. The aligned ECM nanofibers enhanced structure, length, and density of microvascular networks compared to randomly organized nanofibrous ECM. Moreover, hMSC-EC co-culture promoted secretion of pro-angiogenic growth factors and matrix remodeling via metalloprotease-2 (MMP-2) activation, which resulted in highly dense vascular network formation with intercapillary distance (20 μm) similar to the native myocardium.Conclusion: HMSC-EC co-culture on the highly aligned ECM generates physiologically oriented and dense microvascular network, which holds great potential for cardiac tissue engineering.

Influence of Macro-Topography on Damage Tolerance and Fracture Toughness of 0.1 wt % Multi-Layer Graphene/Clay-Epoxy Nanocomposites.

Influence of topographical features on mechanical properties of 0.1 wt % Multi-Layer Graphene (MLG)/clay-epoxy nanocomposites has been studied. Three different compositions were made: (1) 0.1 wt % MLG-EP; (2) 0.1 wt % clay-EP and (3) 0.05 wt % MLG-0.05 wt % clay-EP. The objective of making hybrid nanocomposites was to determine whether synergistic effects are prominent at low weight fraction of 0.1 wt % causing an improvement in mechanical properties. The topographical features studied include waviness (Wa), roughness average (Ra), root mean square value (Rq) and maximum roughness height (Rmax or Rz). The Rz of as-cast 0.1 wt % MLG-EP, clay-EP and 0.05 wt % MLG-0.05 wt % clay-EP nanocomposites were 43.52, 48.43 and 41.8 µm respectively. A decrease in Rz values was observed by treating the samples with velvet cloth and abrasive paper 1200P while increased by treating with abrasive papers 320P and 60P. A weight loss of up to 16% was observed in samples after the treatment with the abrasive papers. It was observed that MLG is more effective in improving the mechanical properties of epoxy than nanoclay. In addition, no significant improvement in mechanical properties was observed in hybrid nanocomposites indicating that 0.1 wt % is not sufficient to generate conspicuous synergistic effects.

Prediction of horizontal movement and strain at the surface due to longwall coal mining

Strain is an important parameter for assessing the potential for impacts on surface features due to mine subsidence. However, this parameter is also one of the most difficult to predict. Research is being undertaken with the objective to improve the currently available predictive methods for horizontal movement and strain at the surface. The methodology predominantly follows an empirical approach, using a large database of ground monitoring data, which was supplemented using numerical modelling. Predictive equations have been developed for the relative horizontal movements across various zones above longwalls based on the vertical subsidence and the influence of topographical features. These relative horizontal movements are then used as the basis to predict the distributions of strain within each of these zones. This paper provides an overview of the methodology and the current findings from this research project.

Influence of Macro-Topography on Damage Tolerance and Fracture Toughness of Monolithic Epoxy for Tribological Applications

Influence of topographical features on mechanical properties of monolithic epoxy samples has been studied. The topographical features studied include waviness (Wa), roughness average (Ra), root mean square value (Rq), and maximum roughness height (Rmax or Rz). The Rz of as-cast monolithic epoxy samples was 13.93 μm. By treating with velvet cloth, the Rz value significantly decreased to 2.28 μm. The Rz value of monolithic epoxy sample treated with abrasive paper 1200P was 4.85 μm which was also lower than that of as-cast monolithic epoxy samples. However, Rz values significantly increased by treating with abrasive papers 320P and 60P and became 20.32 μm and 39.32 μm, respectively. It was interesting to note that although Ra, Wa, and Rq, all increased by treating the monolithic epoxy samples with abrasive paper 1200P, however, Rz decreased by abrasive paper 1200P. A weight loss of up to 17% was observed in monolithic epoxy samples after the treatment with the abrasive papers. Both V-shaped and U-shaped notches were produced on the surfaces of the samples. The mechanical properties were significantly degraded due to surface notches mainly because of the associated stress concentration effect. The topographical features also influenced the dynamic mechanical properties and fracture mode.

A new approach to estimate the spatial distribution of solar radiation using topographic factor and sunshine duration in South Korea

Solar radiation is one of the important renewable resources, currently scientists are taking their interest in. Accurate solar radiation data is not only required for solar-power management but also is a vital input parameter in different biogeochemical and atmospheric models. But there are inadequate number of stations measuring solar radiation in comparison to stations dedicated for sunshine duration, temperature, humidity etc. Therefore, to overcome this problem, an empirical model is developed to estimate solar radiation from sunshine duration data over South Korea. As more than 50% of the area in Korean peninsula have a complex terrain, a topographical factor is applied to modeled data. Thereafter a map presenting monthly mean variation in incoming solar insolation is constructed using ordinary kriging method. The influence of topographical features like slope and aspect is found to be higher in winter than summer. Solar radiation is highest in May and lowest in December over Korea. Spatial variation of incoming radiation is mainly influenced by topographical and atmospheric features whereas latitudinal gradient is almost insignificant.

Nanotopography and Plasma Treatment: Redesigning the Surface for Vascular Graft Endothelialisation

Introduction: Current vascular graft materials in clinical use, such as PTFE and Dacron®, do not endothelialise and have low unacceptable patency rates. The importance of an endothelial cell layer on the luminal surface of a vascular graft is well-known. The influence of topographical features and surface chemistry on cellular adhesion and proliferation is recognised and under investigation. A nanocomposite polymer has been developed which has shown promise as a vascular graft material due to its compliant, biocompatible and anti-thrombogenic properties. However, despite these benefits a lack of endothelialisation is still a cause for major concern. Our aim in this work is to investigate the potential of plasma treatment and topographical structures on the luminal graft surface to enhance the self-endothelialisation potential of a nanocomposite vascular graft material. Methods: POSS-PCU is a polycarbonate urea urethane (PCU) with a nanoparticle, polyhedral oligomeric silsesquioxane (POSS) incorporated within it and fabricated according to published protocols. Microgrooves (MG) of pitch 25 μm were fabricated using photolithography and nanopits, Near-Square (NSQ), were fabricated using electron beam lithography. These were then embossed onto the POSS-PCU polymer and replication fidelity was confirmed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The samples then underwent oxygen plasma treatment at different powers at a fixed time (40 W, 60 W, 80 W at 60 seconds). Successful plasma treatment was confirmed by water contact angle (WCA) measurements. Human Umbilical Vein Endothelial Cells (HUVECs) were seeded onto the treated polymer samples and cell proliferation was measured using Live/Dead Cell® staining. Immunostaining of vinculin and actin was conducted to observe cell morphology and adhesion. Results: The embossing of the micro- and nanostructures were replicated with high fidelity, as seen by SEM and AFM. The microgrooves have a pitch size of 25 μm. NSQ was also verified to be 120nm pits with centre-centre spacing of 300 nm with ±50 nm offset in pit placement. Oxygen plasma treatment of the different samples, show that increase in power increased significantly the hydrophilicity of the samples (p < 0.05). These had a direct impact on giving the optimal surface on which HUVECs preferentially proliferate and adhere, with an average WCA of 68°, giving the highest HUVEC growth. HUVEC proliferation was seen to increase on NSQ surfaces over MG and planar samples, retaining both morphology and function. Conclusion: These exciting observations indicate an important role for nanotopography and plasma treatment in the development of vascular grafts.

Water storage in a till catchment. II: Implications of transmissivity feedback for flow paths and turnover times

AbstractThis paper explores the flow paths and turnover times within a catchment characterized by the transmissivity feedback mechanism where there is a strong increase in the saturated hydraulic conductivity towards the soil surface and precipitation inputs saturate progressively more superficial layers of the soil profile. The analysis is facilitated by the correlation between catchment water storage and groundwater levels, which made it possible to model the daily spatial distribution of water storage, both vertically in different soil horizons and horizontally across a 6300‐m2 till catchment. Soil properties and episodic precipitation input dynamics, combined with the influence of topographic features, concentrate flow in the horizontal, vertical, and temporal dimensions. Within the soil profile, there was a vertical concentration of lateral flow to superficial soil horizons (upper 30 cm of the soil), where much of the annual flow occurred during runoff episodes. Overland flow from a limited portion of the catchment can contribute to peak flows but is not a necessary condition for runoff episodes. The spatial concentration of flow, and the episodic nature of runoff events, resulted in a strong and spatially structured differentiation of local flow velocities within the catchment. There were large differences in the time spent by the laterally flowing water at different depths, with turnover times of lateral flow across a 1‐m‐wide soil pedon ranging from under 1 h at 10‐ to 20‐cm depth to a month at 70‐ to 80‐cm depth. In many regards, the hydrology of this catchment appears typical of the hydrology in till soils, which are widespread in Fenno‐Scandia. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Influence of topographical features on the fluoride corrosion of Ni–Ti orthodontic archwires

Different manufacturing processes of Ni-Ti archwires respond differently to corrosion due to the surface conditions involved. In this study, several topographical features and their influence upon fluoride corrosion were studied. Four topographies (smooth, dimple, scratch, and crack) according to the main surface defect were characterized (n = 40). Static corrosion tests were performed in artificial saliva with fluorated prophylactic gel (12500 ppm) for 28 days. The surface was characterized by SEM and laser confocal microscopy. Standard electrochemical corrosion (open circuit potential, corrosion potential and corrosion current density) was performed. Statistical analysis was carried out using the ANOVA test (α ≤ 0.05). An increase was observed in the surface defects and/or roughness of the cracked and scratched surfaces. These defects produced an important increase in corrosion behavior. The best surfaces for the orthodontic archwires were the smooth and dimpled surfaces, respectively. The increase in defects was independent of roughness. Manufacturing processes that produce surface cracks should be avoided in orthodontic applications.

Nanotechnology and orthopedics: a personal perspective

Bone is a nanocomposite material comprised of hierarchically arranged collagen fibrils, hydroxyapatite and proteoglycans in the nanometer scale. Cells are accustomed to interact with nanostructures, thus providing the cells with a natural bone-like environment that potentially enhance bone tissue regeneration/repair. In this direction, nanotechnology provides opportunities to fabricate as well as explore novel properties and phenomena of functional materials, devices, and systems at the nanometer-length scale. Recent studies have provided significant insights into the influence of topographical features in regulating cell behavior. Topographical features provide essential chemical and physical cues that cells can recognize and elicit desired cellular functions including preferential adhesion, migration, proliferation, and expression of specific cell phenotype to bring desired effects. The current article will address some of the nanotechnology implications in addressing issues related to orthopedic implants performance and tissue engineering approach to bone repair/regeneration.

Objectively mapping HF radar‐derived surface current data using measured and idealized data covariance matrices

Surface currents measured by high‐frequency radars are objectively mapped using covariance matrices computed from hourly surface current vectors spanning two years. Since retrievals of surface radial velocities are inherently gappy in space and time, the irregular density of surface current data leads to negative eigenvalues in the sample covariance matrix. The number and the magnitude of the negative eigenvalues depend on the degree of data continuity used in the matrix computation. In a region of 90% data coverage, the negative eigenvalues of the sample covariance matrix are small enough to be removed by adding a noise term to the diagonal of the matrix. The mapping is extended to regions of poorer data coverage by applying a smoothed covariance matrix obtained by spatially averaging the sample covariance matrix. This approach estimates a stable covariance matrix of surface currents for regions with the intermittent radar coverage. An additional benefit is the removal of baseline errors that often exist between two radar sites. The covariance matrices and the correlation functions of the surface currents are exponential in space rather than Gaussian, as is often assumed in the objective mapping of oceanographic data sets. Patterns in the decorrelation length scale provide the variabilities of surface currents and the insights on the influence of topographic features (bathymetry and headlands). The objective mapping approach presented herein lends itself to various applications, including the Lagrangian transport estimates, dynamic analysis through divergence and vorticity of current vectors, and statistical models of surface currents.

Influence of topographic features and along shelf flow upon the Ebro plume

A three dimensional primitive equation baroclinic model is used to examine the influence of shelf width, along shelf flow and the “mestral” wind upon the spreading of the plume associated with the discharge of the Ebro river into the Balearic Sea. Calculations show that the change in shelf width in the region of the Ebro discharge influences the northward and offshore extent of the plume. Also, along shelf flows are topographically steered offshore by the change in shelf width. For the case in which the northward spread of the plume reaches the narrow shelf region, there is significant interaction between the plume and the shelf edge flow, with the plume water being advected along the shelf edge and further offshore, with a corresponding reduction in its near shore down stream spread. These results are used to interpret the flow fields which arise when an additional forcing, namely the “mestral” wind is applied. The form of the surface circulation produced by the “mestral” wind is characterized by a strong offshore flow in the region of the Ebro outflow, and a surface eddy to the south, centred at approximately mid-way between the shore and the shelf edge. This wind-induced surface flow field significantly modifies the offshore spreading of the Ebro plume. Some general comments concerning the use of the results to complement a field measurement programme, and interpret data collected from such a programme are made in the final section.

Satellite sensing techniques and applications for the purpose of BALTEX

Various satellite sensing techniques and their corresponding applications suitable for use in validation and modelling activities in BALTEX are presented and discussed. Special emphasis is given to data and mature applications available during the main BALTEX BRIDGE experiment. For atmospheric simulations and studies, sensors measuring radiation budget quantities, cloud properties, moisture content and precipitation are considered as most important. Sensors measuring ice conditions and sea state parameters are identified for oceanographical applications and sensors measuring snow conditions and surface conditions are listed for hydrological studies. One example of an application based on extracted cloud information from NOAA AVHRR imagery is demonstrated. Estimations of mean cloud conditions in summer for the period 1991-1998 are shown for the total cloud cover, Cirrus cloudiness and low-level cloudiness over the Nordic region. It is shown that the Baltic Sea and other sea surfaces in the region has a large impact in suppressing summertime cloudiness, in particular low-level cloudiness. As a contrast, cloud patterns for high-level clouds show low correlation with the spatial distribution of sea surfaces. The influence of topographic features (i.e., the Scandinavian mountain range) seems more important here. Cirrus cloudiness peak on the lee side (to the east) of mountains suggesting a frequent presence of lee-wave cirrus clouds. As a summary, the following satellites and sensors will be the main satellite data sources for BALTEX: the ScaRaB instruments on the Ressurs and METEOR satellites, the CERES instrument on the EOS-AMI satellite, the AVHRR and ATOVS sensors on the NOAA satellites. the MVIRI and SEVIRI sensors on the METEOSAT satellites, the SAR instruments on the ERS, Radarsat and ENVISAT satellites and the SSM/I instrument on the DMSP satellites. Of particular interest is also radio occultation measurements of the radio signals from the GPS satellites. The need for a central BALTEX coordination facility (a satellite data function) with the objective to compile and transfer satellite data from various processing centres to BALTEX research groups is particularly stressed.

The influence of topographic features and density variations upon the internal tides in shelf edge regions

The influence of topographic features and density variations upon the internal tides in shelf edge regions

The influence of topographic features and density variations upon the internal tides in shelf edge regions

A brief outline of the development of a three-dimensional primitive equation baroclinic model for computing the internal tides is presented. A series of calculations are performed to examine the internal tide in the shelf edge region off the west coast of Scotland, with the aim of determining the influence upon the internal tide in the region of topographic features, namely large-scale features, such as seamounts, and small-scale features, such as a detailed specification of the shelf slope, which is possible using results from a recent survey rather than topographic data taken from a coarse grid model using depths interpolated from charts. The influence upon the solution of small variations in the density field and seasonal variations is examined. Also, the influence of a well-mixed bottom boundary layer at the base of the shelf slope, produced possibly by cascading of dense water off the shelf during a major wind event, upon the internal tide is also examined. In the calculations described here the model is used in cross-shelf form. A comparison of internal tides computed with and without the inclusion of an offshore seamount shows that internal tides are produced along the sides of the seamount, and can propagate towards the shelf edge, and thereby influence the internal tidal signal in that region. A comparison of internal tides computed using previously available bottom topography extracted from charts with those computed using a detailed topographic data set from a recent survey shows the importance of accurate topography in the shelf edge region for internal tide calculations. Simulations show that the internal tide is influenced by variations in the density field, suggesting that an accurately measured density field is essential for internal tide determination. Calculations also show that if a well-mixed sea bed boundary layer occurs at the bottom of the shelf slope, the internal tide can be reflected by this feature giving rise to significant internal tides in the ocean at larger distances from the shelf edge than in the absence of this water mass.