Depth Sections Research Articles

FLOODWALL: A Real-Time Flash Flood Monitoring and Forecasting System Using IoT

In recent years, flooding has become a major problem, encountered in many places all over the world, causing damage to property ranging from human life to economic losses. Floods cannot be prevented and eliminated, but the catastrophic damage caused by them can be mitigated. Floods can be predicted in advance with the help of emerging technologies, such as the Internet of Things (IoT). Using such technologies, the people can be warned in advance and evacuated from affected areas to safe places, along with their valuable possessions. In this context, a real-time application is required that can provide an early flood warning based on the seamless data received from IoT devices about various parameters. In this work, we have developed an IoT-based prototype to collect hydrological data of rivers, such as water flow, water level, and water discharge. The proposed system is also able to collect meteorological data, such as temperature, humidity, wind speed, and wind direction. Furthermore, the collected data have been analyzed and classified by using the long short-term memory (LSTM) model with water discharge, water level, rainfall, and temperature as input parameters. The LSTM model then classified the flood events either into “no alert,” “yellow alert,” “orange alert,” or “red alert.” As rivers have dynamic geographical features, measuring the total discharge of water becomes a complex task. To address this vulnerability, a novel approach for determination of water discharge using water flow, sectional area width, and sectional average depth is proposed. In addition, the difficulties in measuring the total amount of rainfall due to the erratic behavior of the weather conditions of the unique geographical location have been addressed. The system is found to accurately predict the flood event state with F1-score of 97% for “no alert,” 97% for “yellow alert,” 96% for “orange alert,” and 98% for “red alert.”

Reconstruction of sedimentation conditions in paleo-reservoirs of the northern part of the Sambian Peninsula based on the comprehensive study of the Kulikovo section

A comprehensive analysis of the deposits of the paleo-reservoir represented in the Kulikovo section (the northern part of the Sambian Peninsula) has been carried out. According to results of radiocarbon dating, the deposits formed approximately from 14100 to 12900 cal yr BP. The most detailed data were obtained for the lower part of the section (depth 192–141 cm), comprising the Older Dryas and the first half of the Allerød. Results of a comprehensive lithological, diatom, spore-and-pollen analysis and algo-zoological microfossil analysis allowed us to identify 8 stages of the sedimentation conditions of the paleo-reservoir.

Three-dimensional electron microscopy by STEM depth sectioning

Three-dimensional electron microscopy by STEM depth sectioning

Geoelectrical resistivity and geochemical method for groundwater investigation in the coastal sediment

This research presents new investigations on the identification and mapping of heavy metals in aquifer systems using geoelectrical methods, water samples, and geochemical analyses. The subsurface was investigated using a total of three geoelectrical survey lines in the Wenner Schlumberger configuration. Six samples—three from bore wells, two from rivers, and one from the sea—were collected for additional laboratory examination in order to observe the quality of the water samples and variations in hadrochemical water samples in the research area. Soil samples collected from three different places were geochemically analysed. Cd concentration (0.94-2.42 mg/kg) was found to be higher in the northern portion of the study site, and Cr concentration (4.39-72.98 mg/kg), Ni concentration (12.11-47.69 mg/kg), and Co concentration (7,19-12,86) were found to be higher in the southern section. While Cd, Cr, Ni, and Co distribution of heavy metals are quite high in the northern and southern areas of Galesong beach, they are relatively low in the middle. A geochemical study of soil samples reveals that Cd and Cr concentrations are significantly high in the resistivity zone (<20 Ωm). The environmental resistivity value is low from the center zone to the northwest. The heavy metal zone in the aquifer system can be simply represented by the geoelectrical resistivity distribution presented in the form of a depth section, even though the resistivity value of more than 40 Ωm can be regarded as an aquifer zone.

Experimental and Numerical Investigation of Aluminum Beams: Flexural Behavior Section Shape Effect

Advanced technology and other aspects of life aim to use the available and efficient materials. Due to their high strength-to-weight ratio and durability, aluminum alloys are used in a variety of structural engineering applications. This paper describes the experimental and numerical flexural behavior investigation of the aluminum beams. The main variables considered in the study are related to section shape, which are the shape configuration, depth, and thickness of the aluminum section. The finite element three dimensional models are used to analyze the tested beams in order to check the ability of the models to predict the overall behavior and to obtain more information about the stresses and strains that developed. The results show that the larger the value of the section shape factor, the fiber is still in the elastic range, and the smaller the plastic deformation of the beam. And the web plates slenderness ratio has a significant influence on the load-deflection relationship because of local deformation as well as the plastic deformation of box beams is relatively smaller than that of the I-section beam. The constraint of the flange for box beams is greater than that for I-section beams. Besides, the adopted nonlinear numerical modeling gives acceptable agreement with the experimental results besides the load-deflection responses, the ultimate strength convergence ratios varied between 1.1-0.93.

THE CAESAREA GERMANICIA (?) OF ARCHEOGEOPHYSICAL INVESTIGATIONS

The remains unearthed in the Dulkadiroğlu district, one of the central districts of Kahramanmaraş, are thought to belong to Caesarea Germanicia, which was founded in the Roman Period. Research and excavations carried out by the Kahramanmaraş Museum and us in the region have revealed that the spread of archaeological cultural remains is more than 150 hectares. Although the concentration of Roman Period cultural remains in the research and excavations was remarkable, the discovery of Byzantine, Seljuk, and Ottoman Period ceramic pieces indicates an uninterrupted settlement in the research area for centuries. However, as can be seen in the images, the dense residential texture in the region is one of the biggest obstacles to archaeological research and excavations. Because, in order to carry out archaeological excavations of the identified structures, expropriations are required. However, the expropriation period covers an average of 2-4 years, which makes it difficult to conduct scientific research. Archeogeophysical methods provide information about the location, depth, and dimensions of the archaeological remains by applying them from the surface, without causing any damage to the archaeological remains sought. In this context, Ground Penetrating Radar (GPR) measurements were carried out to determine the quality of the mosaic-based structure on 445 layout, which were previously unearthed through illegal excavations in 2019, and the parcels on which it extends. GPR was carried out along 6 profiles. The obtained results were compared both with each other and with the existing surface conditions, and GPR depth maps were created. When the GPR depth sections were examined, 4 important reflections were found. It has been interpreted that 3 of these reflections belong to the archaeological building remains and 1 of them originates from a metal material (pipe). It was determined that the depth of the archaeological remains identified in the GPR sections started at a depth of approximately 20 cm. As a result of the excavation, it was seen that the reflections determined in the GPR sections belonged to the wall remains and metal pipe. As a result of archaeological excavations, it was determined that the GPR reflections belong to the remains of the walls of the Villa Rustica of the Early Byzantine Period or a Roman bath, as well as a metal pipe. In the measurements of the ground radar, it was determined that other walls cut the building walls in parallel. As a result of archaeological excavations, it was understood that these walls were made of rubble stone with mud additives. It was discovered during archaeological excavations and was discovered in the 11th-13th centuries AD. One of the ceramic fragments indicates that this structure was used again in the Middle Byzantine Period.

Reconstruction of Paleoenvironment and Paleoclimate of the Neogene Guantao Formation in the Liaodong Sub-Uplift of Bohai Bay Basin in China by Sedimentary Geochemistry Methods

The paleosedimentary environment and paleoclimate of the Neogene Guantao Formation in the Liaodong sub-uplift of Bohai Bay Basin in China, which is an important oil and gas exploration horizon, are not clear owing to the lack of quantitative analysis. The paleosedimentary environment and paleoclimate can be qualitatively or semi-quantitatively reconstructed by sedimentary geochemical indicators sensitive to the environment and climate. Based on the evaluation of whether the elements and isotopes can effectively record paleosedimentary environment and paleoclimate information or not, the paleoclimate (temperature and humidity), paleoenvironment (salinity, water depth, redox conditions), and evolution of the paleoenvironment and paleoclimate are studied by analyzing the trace elements, carbon and oxygen isotopes, strontium isotopes, whole-rock mineral compositions, and clay minerals of mudstones of the Guantao Formation in the Liaodong sub-uplift, Bohai Bay Basin. The study results show that (1) according to the trace element distribution patterns, high concentrations of continental elements (Ti, Zr, Th), clay minerals, and detrital content, the Guantao Formation is a product of proximal deposits, and the provenance mainly originates from the intermediate–acidic magmatic rocks near surrounding uplifts. (2) The paleoclimate during the sedimentation of the Guantao Formation was mainly semi-arid and semi-humid, as revealed by the Sr/Cu ratio. However, the high Rb/Sr and 87Sr/86Sr ratios demonstrate that the paleoclimate is relatively warm and humid. (3) The paleosedimentary temperature calculated by the Sr content and δ18O is roughly 30 °C, indicating that the Guantao Formation was deposited in a subtropical to tropical climate. (4) The Guantao Formation was deposited in continental freshwater according to the Li, Ni, and Sr content, Sr/Ba ratios, 87Sr/86Sr ratios, and salinity index Z. (5) The water depth of the paleoenvironment of the Guantao Formation is mainly in nearshore shallow water, reflected by the Mn/Ti ratio and calculated by the Co content, and the oxidizing condition of the paleoenvironment of the Guantao Formation, reflected by the U/Th, V/Cr, and Ni/Co ratios, is in a good coupling relationship with this environment. (6) As revealed by the variations in the geochemical data in the section, the temperature, humidity, and water depth of the Guantao Formation gradually increased from the early to late period, while the salinity gradually decreased, and the chemical weathering effect gradually increased.

Geoelectrical Sounding to Identify Sub-surface and Groundwater State at Village Banauli, Singrauli District, Madhya Pradesh, India

Electrical resistivity (Geoelectrical) methods are well-known and common techniques for investigating the groundwater potential zone. These methods are economically viable and have the highest resolving power compared with other geophysical methods. A total of fifteen Vertical electrical soundings were conducted in the village of Banauli, located in Singrauli district in Madhya Pradesh, India. Vertical electrical sounding was carried out using Schlumberger electrode configuration with the maximum current electrode (AB) spacing of 200 m and potential electrode (MN) spacing of 10 m. For interpretation of measured resistivity, the Partial curve matching technique was used to calculate the layer parameters (resistivity and thickness) and further depict the depth section of the profile. In this study, the maximum five-layer model is obtained, and most curves are of HAK types. The first layer has a mean resistivity value of 12.41 Ωm and a mean thickness of 0.94 m. The second layer has mean resistivity of 7.93 Ωm and a mean thickness of 4.79 m. The third layer has a mean thickness value of 10.55 m and a mean resistivity value of 16.54 Ωm. The fourth layer has a mean resistivity value of 20.17 Ωm and a mean thickness of 9.20 m, and finally, the fifth layer, the bedrock, has a higher mean resistivity value of 59.92 Ωm. Thus, the obtained results may be used for identifying the drilling site for the groundwater potential zone.

Machine Learning Prediction Model for Shear Capacity of FRP-RC Slender and Deep Beams

FPR reinforcing bars have emerged as a promising alternative to steel bars in construction, especially in corrosive environments. Literature includes several shear strength models proposed for FRP-RC members. This study presents a detailed evaluation of design shear models proposed by researchers and design codes. The evaluation was conducted through an extensive surveyed database of 388 FRP-RC beams without shear reinforcement tested in shear. Gene expression programming (GEP) has been utilized in this study to develop accurate design models for the shear capacity of slender and deep FRP-RC beams. Parameters used in the models are concrete compressive strength (f’c), section depth (d), section width (b), modular ratio (n), reinforcement ratio (ρf), shear span-to-depth ratio (a/d). The proposed model for slender beams resulted in an average tested-to-predicted ratio of 0.98 and a standard deviation of 0.21, while the deep beams model resulted in an average tested-to-predicted ratio of 1.03 and a standard deviation of 0.29. For deep beams, the model provided superior accuracy over all models. However, this can be attributed to the fact that the investigated models were not intended for deep beams. The deep beams model provides a simple method compared to the strut-and-tie method.

A 3D-printed spiral actuator for focus adjustment in circumferential scanning endomicroscopy

In this study, we showcase the design, manufacturing, and characterization of the focus adjustment actuator for use in capsule endoscopy. The actuator has a spiral flexure, carrying a lens and multiple magnets at its center to facilitate focusing through electromagnetic actuation. The interplay between the spiral flexure length and the lens size is investigated for optimal performance. An external coil is utilized to drive the lens actuator with a low power (∼5 mW) to acquire data from targets placed at multiple depths, axially spanning a range of 5 mm. The proposed actuator was intended for use in a circumferentially scanning wireless capsule endoscopy to provide high-resolution imaging at multiple depth sections throughout the gastrointestinal tract. The proposed device, targeted for confocal imaging, comprises a laser source and a light detector, the 3D-printed focus adjusting actuator to address different layers, a prism integrated micro-motor for circumferential scanning. We showcase a proof of principle data acquisition from reflective targets placed at different depths, through utilizing a scanning micromotor in conjunction with the developed focus actuator. With further development, the proposed actuator can be adapted to clinical environment to perform optical biopsies.

Numerical solution of the three-dimensional Burger’s equation by using the DQ-FD combined method in the determination of the 3D velocity of the flow

In this paper, the differential quadrature and the finite difference combined method (DQ-FDM) was applied to solve the three-dimensional Burger’s equation in the determination of the 3D velocity of the flow; so that spatial terms were discretized by the differential quadrature method, and the temporal term was discretized by the finite difference method, and the resulting nonlinear equations were solved using the Newton–Raphson method. All variables were considered as dimensionless in this equation. The solution results were compared with solution results of the two-dimensional equation in the two other numerical methods available in the literature which provided an acceptable accuracy. Also, the results of the mentioned numerical method were compared with those of the fully implicit finite difference method that was solved for larger than or equal viscosities of 0.1. The results showed that by increasing time and viscosity, the longitudinal, depth and transverse velocities were decreased. The occurrence of the upward flow was observed especially in the upsilon = 0.05 in the close of the bed, end of the length and width that in the presence of very fine particles of the clay and silt shows suspension of these particles in some spaces. The position of the longitudinal, depth and transverse velocities in the plan for the passing plates through the section depth for different viscosities and times showed that by increasing viscosity and time, the position of the maximum velocities became closer to the middle of the section width. Also, stream lines were plotted in all of sections and then analyzed.

Testing of Structural Integrity of U-Shaped Sheet Pile in Canal Engineering Using Ground Penetrating Radar

Compared with other piles with the same cross-sectional area, “U-shaped” structural section sheet pile can increase the moment of inertia of the structure’s section. Due to the large excavation depth of the open section of the “Yin Jiang Ji Huai” river canal project in Anhui province, China, the unprotected excavated inclined canal slope covers a large land area, which results in the current situation of high housing demolition costs and a shortage of land resources in densely populated areas. In this study, the non-destructive testing of a U-shaped sheet-pile wall to protect the vertical slope of the underwater expansive soil in the canal project is studied, which is of great significance in reducing the construction area and minimizing the cost of construction. It is necessary to test the structural integrity of the U-shaped sheet pile, which is also vital to ensuring the whole project quality. Ground penetrating radar (GPR) is used to detect the structural integrity of the U-shaped sheet pile in expansive soil. On the basis of identification and conversion of the original GPR data format, the processing methods based on the time-varying automatic gain and wavelet analysis are implemented. This case study proves that the GPR testing method is effective to estimate the quality of the U-shaped sheet pile.

Investigations on the influence of load width on web compression buckling strength of wide-flange steel members

A comprehensive study on web-compression buckling strength of wide-flange steel members subjected to concentric transverse loads spread over lengths longer than member section depth is presented in this paper. Calculation methodologies previously developed for web-compression-buckling strength of wide-flange steel members were established for use in beam-to-column moment connections, where the load width is relatively very narrow compared to the depth of the section, therefore does not include load width as a parameter in strength equations. More recently developed calculation procedures that account for load widths are typically limited to member section depth and are merely based on numerical models, and lack experimental evidence that validates these models. This study presents experimental research on steel wide-flange members subjected to transverse compression loading by having the load length as the primary variable. Experiments were conducted on specimens with measured imperfection levels and provided results on the buckling strength, displacement, and strain variation of the web portion during testing. The experimental program also investigated the potential of creep under sustained loading on web compression buckling strength of wide flange members at load levels near buckling strength. Benchmark numerical models using the finite element method were developed using the test results to obtain insights into the observed behavior and were employed in conducting numerical parametric studies to investigate the sensitivity of results due to load width and the angle of the applied load for various cross sections. The results obtained from the experimental and numerical studies were compared with the calculation methods provided in the North American and European design codes to evaluate their accuracy. The parametric study results were also used to develop an analytical calculation procedure for estimating the web-compression-buckling strength of steel wide-flange shapes subjected to vertical and inclined loading.

MLReal: Bridging the gap between training on synthetic data and real data applications in machine learning

Among the biggest challenges we face in utilizing neural networks trained on waveform (i.e., seismic, electromagnetic, or ultrasound) data is its application to real data. The requirement for accurate labels often forces us to train our networks using synthetic data, where labels are readily available. However, synthetic data often fail to capture the reality of the field/real experiment, and we end up with poor performance of the trained neural networks (NNs) at the inference stage. This is because synthetic data lack many of the realistic features embedded in real data, including an accurate waveform source signature, realistic noise, and accurate reflectivity. In other words, the real data set is far from being a sample from the distribution of the synthetic training set. Thus, we describe a novel approach to enhance our supervised neural network (NN) training on synthetic data with real data features (domain adaptation). Specifically, for tasks in which the absolute values of the vertical axis (time or depth) of the input section are not crucial to the prediction, like classification, or can be corrected after the prediction, like velocity model building using a well, we suggest a series of linear operations on the input to the network data so that the training and application data have similar distributions. This is accomplished by applying two operations on the input data to the NN, whether the input is from the synthetic or real data subset domain: (1) The crosscorrelation of the input data section (i.e., shot gather, seismic image, etc.) with a fixed-location reference trace from the input data section. (2) The convolution of the resulting data with the mean (or a random sample) of the autocorrelated sections from the other subset domain. In the training stage, the input data are from the synthetic subset domain and the auto-corrected (we crosscorrelate each trace with itself) sections are from the real subset domain, and the random selection of sections from the real data is implemented at every epoch of the training. In the inference/application stage, the input data are from the real subset domain and the mean of the autocorrelated sections are from the synthetic data subset domain. Example applications on passive seismic data for microseismic event source location determination and on active seismic data for predicting low frequencies are used to demonstrate the power of this approach in improving the applicability of our trained NNs to real data.

Erosion-accretion pattern in the tidal-rivers of Indian Sundarban in relation to estuarine hydrodynamics

Mapping the changes in the deltaic-coastal zone under changing hydrodynamic conditions is crucial for developing a concise picture of coastal vulnerability. The present study provides a comprehensive idea of changing scenario of rivers in the world's largest delta-Sundarban, using a variety of remotely sensed data and measurements, and relating these changes to hydrodynamic conditions. Bathymetric changes have also been estimated using Landsat imageries, calibrated with bathymetric chart data. We document a substantial dynamic variation between western and eastern sections of the Sundarban tidal rivers, as well as between the northern and southern parts. As such, banks adjoining the Saptamukhi and Thakuran rivers in the west have accreted by +43.48 ​km2 and +6.13 ​km2 respectively, while the net change in the eastern rivers like Matla, Gosaba, and Hariabhanga river systems shows a loss of −51.54 km2, –13.92 km2, and –13.82 km2, respectively, over the last century. Erosion rates have decreased from the southern seafront zone to the northern interior parts due to the low wave exposure, and high tidal range. The accretion rate has increased on the same ground. The depth of these rivers has also changed significantly. For instance, the depth of most sections along the Thakuran river has increased from 5 to 7 m to about 7–10 m during the period 1987–2016. The findings of this study will help researchers all around the world in understanding the centurial dynamics of tidal rivers, and by comparing these to other deltas, it will be possible to emphasize the relative vulnerability of major deltas to current sea level rise.

Substantiation of the Design and Layout Scheme for the Gravity-Pneumatic Soybean Seed Cleaner

It is shown that scientifi c research into the intensifi cation of soybean seed separation processes is necessary for developing new type purifi cation technologies that eliminate the shortcomings of traditional machines, as well as achieving more favorable technical and economic indicators of grain cleaning equipment. (Research purpose) To substantiate the design parameters of a cleaning and sorting plant for highly efficient separation of soybean seeds. (Materials and methods) We used a developed prototype model of the plant for cleaning soybean seeds, consisting of a gravity column and a pneumatic cleaning and sorting channel. The number of combs in the gravity column and the gap between the comb bars were substantiated. Subject to different supply of material, the completeness of separating a large impurity was determined in a gravity column, a light impurity – in the first section of the channel, soybean halves – in the second section of the channel, small and puny soybean seeds – in the third one. (Results and discussion) The optimal number of combs for the gravity column was set to 10 pieces with a gap between the comb bars of 10 millimeters, thus providing the separation effi ciency of 99.3 percent. It was obtained that the optimal ratio between the width of the narrowing partition and the 50-millimeters depth of the channel section equals 0.37. The width of the narrowing partitions was calculated to be 55.5 millimeters; the optimal supply of soybeans is 2.5 tons per hour, thus providing the separation completeness in the gravity column of no less than 95 percent, and that in the pneumatic channel of no less than 98 percent. (Conclusions) It was determined that the intensifi cation of the soybean seed separation process is possible by the combined use of a gravity column and a pneumatic separating device, which can increase the productivity and effi ciency of soybean cleaning by 20 percent or more.

Multiview PCA: A Methodology of Feature Extraction and Dimension Reduction for High-Order Data.

Facing with rapidly increasing demands for analyzing high-order data or multiway data, feature-extracting methods become imperative for analysis and processing. The traditional feature-extracting methods, however, either need to overly vectorize the data and smash the original structure hidden in data, such as PCA and PCA-like methods, which is unfavorable to the data recovery, or cannot eliminate the redundant information very well, such as tucker decomposition (TD) and TD-like methods. To overcome these limitations, we propose a more flexible and more powerful tool, called the multiview principal components analysis (Multiview-PCA) in this article. By segmenting a random tensor into equal-sized subarrays called sections and maximizing variations caused by orthogonal projections of these sections, the Multiview-PCA finds principal components in a parsimonious and flexible way. In so doing, two new operations on tensors, the S -direction inner/outer product, are introduced to formulate tensor projection and recovery. With different segmentation ways characterized by section depth and direction, the Multiview-PCA can be implemented many times in different ways, which defines the sequential and global Multiview-PCA, respectively. These multiple Multiview-PCA take the PCA and PCA-like, and TD and TD-like as the special cases, which correspond to the deepest section depth and the shallowest section depth, respectively. We propose an adaptive depth and direction selection algorithm for the implementation of Multiview-PCA. The Multiview-PCA is then tested in terms of subspace recovery ability, compression ability, and feature extraction performance when applied to a set of artificial data, surveillance videos, and hyperspectral imaging data. All numerical results support the flexibility, effectiveness, and usefulness of Multiview-PCA.

A Three-Dimensional Reconstruction Algorithm for Scanning Transmission Electron Microscopy Data from a Single Sample Orientation

Abstract Increasing interest in three-dimensional nanostructures adds impetus to electron microscopy techniques capable of imaging at or below the nanoscale in three dimensions. We present a reconstruction algorithm that takes as input a focal series of four-dimensional scanning transmission electron microscopy (4D-STEM) data. We apply the approach to a lead iridate, PbIrO, and yttrium-stabilized zirconia, YZrO, heterostructure from data acquired with the specimen in a single plan-view orientation, with the epitaxial layers stacked along the beam direction. We demonstrate that Pb–Ir atomic columns are visible in the uppermost layers of the reconstructed volume. We compare this approach to the alternative techniques of depth sectioning using differential phase contrast scanning transmission electron microscopy (DPC-STEM) and multislice ptychographic reconstruction.

Densification mechanism of deep low-permeability sandstone reservoir in deltaic depositional setting and its implications for resource development: A case study of the Paleogene reservoirs in Gaoshangpu area of Nanpu sag, China

A better understanding of reservoir densification mechanisms is very important for petroleum exploration and controlling the reservoir quality distribution in low-permeability reservoirs. Low porosity and low permeability, difficult reconstruction, and economic infeasibility are important factors restricting its efficient production. Systematic analysis was performed to study the evolution of different microfacies in the deltaic depositional setting of the Paleogene deep low-permeability Gaoshangpu reservoir, define their genetic mechanisms, delineate the dominant facies belts, and define the favorable diagenetic sequences that are important for exploration of high-quality reservoirs. To understand the tight genesis of the low-permeability reservoirs, we analyzed the sedimentological and diagenetic evolution characteristics of various microfacies (i.e., underwater distributary channel, distributary bay, mouth bar, and front sheet sand) using core data and physical property analysis of the reservoir sand body. The results show the underwater distributary channel and estuary bar sand body with medium-to fine-grained and poor–medium sorting. The diagenesis is dominated by strong compaction, calcareous, argillaceous cementation, and dissolution during stage B in early diagenesis and stage A in middle diagenesis. In the fan delta environment, the weak anti-compaction resistance of low-permeability reservoirs is mainly due to the large content of plastic particles, finer grain size, and medium–poor sorting, with an average porosity reduction rate of 65%. This is a key factor for densification of reservoirs above 3000 m. Comparison among different sandstone microfacies of the deltaic setting shows that the sand body of the underwater distributary channel with low shale content has slightly stronger compaction resistance. The porosity reduction is not obvious at the depth of 3,000–4,000 m, but the loss of permeability at this depth section is significant, and the reservoir improvement from later dissolution is most obvious at this depth section. Calcareous cementation is the cause for densification of some mouth bars in the early stage and of underwater distributary channels in the middle and late stage. Under the influence of strong compaction and calcareous-filling pore throat, the sand body of the mouth bar has been basically densified at 3,000 m, resulting in limited reservoir transformation from later dissolution. The study shows that compaction is the main cause of reservoir densification, argillaceous and calcareous cementation is the secondary cause, and later dissolution is another main cause of reservoir enhancement. The research results can provide a reference and direction for reservoir development and search for the high-quality sweet spot in the deep and low-permeability reservoir.

Atmospheric Correction Model for Water–Land Boundary Adjacency Effects in Landsat-8 Multispectral Images and Its Impact on Bathymetric Remote Sensing

Atmospheric correction (AC) is the basis for quantitative water remote sensing, and adjacency effects form an important part of AC for medium- and high-spatial-resolution optical satellite images. The 6S radiative transfer model is widely used, but its background reflectance function does not take the radiance changes at water–land boundaries into account. If the observed land possesses bright features, the radiance of the adjacent water will be affected, leading to deviations in the AC results and increasing the uncertainty of water depth-based optical quantitative remote sensing. In this paper, we propose a model named WL-AE (a correction model for water–land boundary adjacency effects), which is based on the obvious radiance differences at water–land boundaries. This model overcomes the problem by which the background reflectance calculation is not terminated due to the highlighting pixel. We consider the influences of different Rns (neighborhood space) on the target pixel. The effective calculation of the equivalent background reflectance of the target pixel is realized, and the influence of the land area anomaly highlighting the pixel on the adjacent water is avoided. The results show that WL-AE can effectively improve the entropy and contrast of the input image and that the water–land boundary is greatly affected by adjacency effects, especially in the green and near-infrared bands, where the Mrc (mean rate of change) are as high as 14.2% and 20.1%, respectively. In the visible wavelength, the Sd of Rrc (the relative rate of change) is positively correlated with Rns, and the Sd reaches 16.9%. Although the adjacency effect is affected by ground object types, its influence area remains within 3 km offshore. Based on the WL-AE and 6S results, the comparative test regarding bathymetric inversion shows that the influence is significant in the 0–5 m depth section. In Penang, the MRE of the 0–4 m inversion results is 31.4%, which is 10.5% lower than that of the 6S model.