Shadow Effect Research Articles

A new contour balancing rearrangement technique to enhance the solar PV array power under a realistic partial shading condition

Under partial shading conditions, the solar photovoltaic (PV) array receives an irregular pattern of solar light intensity which results in the creation of multiple peaks in the power vs voltage (P-V) and current vs voltage (I-V) plot and ultimately leads to hot spots creation and reduced power generation. Therefore, in this paper, redistribution of the shadow effect is assessed using a newly proposed reconfiguration method for the PV array called Contour Balancing Rearrangement (CBR) method. The proposed CBR method is based on the “Smash n′ Throw” approach which is applied to reconfigure the total-cross-tied (TCT) topology of the PV array that redistributes the shading pattern in such a way that the average irradiance of each row is almost the same. Further, a novel pragmatic dynamic cloud model is formulated to realize the partial shading condition as in realistic form at a particular location of the earth’s surface. For a more realistic analysis, the movement and acceleration of moving clouds are taken into account along with the coordinates of the place of interest for more accurate values of solar irradiation. Furthermore, different comparative studies are also carried out among the proposed and existing methods of various PV array reconfiguration methods to show the efficacy.

Research on the interface and properties of spherical ZTA particles reinforced Fe-Cr-B matrix composite

Spherical zirconia toughened alumina (ZTA) particles reinforced Fe–Cr–B matrix composite was prepared by the liquid phase sintering in the current study. The results demonstrated that at the sintering temperature of 1380 °C, a prominent interface layer was formed between the spherical ZTA particles and the Fe–Cr–B alloy, the thickness of which is about 50 μm. The combined effects of B element, Mn element and SiO2 promote the formation of the interface. Mn2SiO4, Fe2SiO4, MnFe2O4 and B2O3 were formed at the interface. The formation mechanism is described. Hardness and Young's modulus of SZ40 sample at the interface are 12.88 and 146.60 GPa, respectively, which play a crucial role in combining of ZTA particles and the matrix. The wear resistance of the composite prepared in the current study is excellent. The wear volume loss decreases gradually with the increase of spherical ZTA volume fraction. Under the same wear conditions, the volume loss of the SZ40sample is only 9.65% of that of the Cr16 sample and is 14.33% of that of the matrix sample. The spherical ZTA in the composite is higher than the Fe–Cr–B matrix, forming a “shadow effect” to protect the matrix. The Fe–Cr–B matrix has better toughness and can support the spherical ZTA particles during the wear process. Effective combination of the advantages of the two reduces the volume loss of the composite.

Investigation of interference from multiple oriented hydraulic fractures while considering near-radial wellbore stress distribution

Stratigraphic sequences are sometimes thin, rarely ideally horizontal and juxtaposed due to faulting. Wellbore trajectories targeting such strata may not be necessarily horizontal aligning with principal stress direction. Perspective from perforation orientations typically embeds understanding of fundamental fracturing issues such as high treating pressure, premature screen-outs, and tortuous and short-circuited fracture paths among others. One or more of these issues may influence other drawbacks making the overall problem more complicated. The objective of this study is to investigate the influence of stress shadow effect of multiple fracture propagation on treating pressure and fracture geometries (apertures, lengths, heights, and tortuosity) then later introduce a new concept of controlling fluid entry into multiple oriented perforations through modification of entry elements combined with radial wellbore technology. The study demonstrates that both simple bi-wing and complex multiple bi-wing fractures are associated with low treating pressure when combination of high phase/high or low orientation angles, illustrated with 1800/900 and 1800/00, is used. It has further shown that oriented perforation reduces the extent of fracture closure zone around the crack mouth. Sequential and simultaneous techniques are implemented with their comparison demonstrating that sequential fracturing is associated with elevated fluid pressure after first injection. A maximum error as low as 0.52 MPa is recorded during the bottom hole pressure analysis. Optimized results from restricted fluid entry elements, simulated within XFEM computational domain capable of accommodating fracture-turning effect, minimized fracture choke-like effect producing relatively uniform fracture development. The new elements are validated against KGD model. The model is further validated against published experiments and Daqing Oilfield data with good match of results in both cases. The study is important for field implementation of hydraulic fracturing in stratigraphically thin reservoirs with well trajectories disoriented from principal stress direction.

Multi-fracture initiation sequence and breakdown pressure in horizontal wells during TDPF: A visualization experimental investigation based on PMMA

Temporary plugging and diverting fracturing (TDPF) is an effective stimulation method to achieve multiple uniform fracture propagation in unconventional reservoirs. The plugging mechanism of diverters and the feasibility of diverted fractures have been investigated well in previous studies. However, few studies aim at the relationship between the multi-fracture morphology and injection pressure curve during TDPF because multiple fractures can not be directly observed during the fracturing process. This study established a visual true tri-axial fracturing physical experiment based on transparent polymethyl methacrylate (PMMA) to investigate the multi-fracture initiation sequence and breakdown pressure in the horizontal wellbore during TDPF. The critical fracture parameters, including completion method, injection flow rate, injection fluid type, fracture density, perforation depth and stress difference coefficient, were analyzed in detail based on twelve PMMA samples. The results showed that all experiments just produced one hydraulic fracture in the initial fracturing stage, but sequentially created multiple fractures after multiple diversion stages. Meanwhile, due to the effect of stress shadow, the break-down pressure of the first and second diverted fracture was 1.36 times and 1.67 times of the initial fracture respectively. In addition to the transverse fractures produced in the diversion stages, longitudinal fractures were also created along the horizontal wellbore, which decreased the multiple fracture initiation effectiveness. Optimized parameters, i.e. perforation completion method, high injection flowrate, moderate fracture density, uniform perforation depth and high-viscosity carrier fluid with diverters, were recommended to obtain more transverse fractures during TPDF. In addition, our results also revealed three fracture initiation sequences of multiple fractures in the horizontal well during TPDF. This study described the relationship between the visual multi-fracture geometries and breakdown pressure in horizontal wells during TPDF, which provides new insights into the propagation mechanism of multiple fractures and guidance for fracturing design in the oilfield.

DARCLOS: a cloud shadow detection algorithm for TROPOMI

Abstract. Cloud shadows are observed by the TROPOMI satellite instrument as a result of its high spatial resolution compared to its predecessor instruments. These shadows contaminate TROPOMI's air quality measurements, because shadows are generally not taken into account in the models that are used for aerosol and trace gas retrievals. If the shadows are to be removed from the data, or if shadows are to be studied, an automatic detection of the shadow pixels is needed. We present the Detection AlgoRithm for CLOud Shadows (DARCLOS) for TROPOMI, which is the first cloud shadow detection algorithm for a spaceborne spectrometer. DARCLOS raises potential cloud shadow flags (PCSFs), actual cloud shadow flags (ACSFs), and spectral cloud shadow flags (SCSFs). The PCSFs indicate the TROPOMI ground pixels that are potentially affected by cloud shadows based on a geometric consideration with safety margins. The ACSFs are a refinement of the PCSFs using spectral reflectance information of the PCSF pixels and identify the TROPOMI ground pixels that are confidently affected by cloud shadows. Because we find indications of the wavelength dependence of cloud shadow extents in the UV, the SCSF is a wavelength-dependent alternative for the ACSF at the wavelengths of TROPOMI's air quality retrievals. We validate the PCSF and ACSF with true-colour images made by the VIIRS instrument on board Suomi NPP orbiting in close proximity to TROPOMI on board Sentinel-5P. We find that the cloud evolution during the overpass time difference between TROPOMI and VIIRS complicates this validation strategy, implicating that an alternative cloud shadow detection approach using co-located VIIRS observations could be problematic. We conclude that the PCSF can be used to exclude cloud shadow contamination from TROPOMI data, while the ACSF and SCSF can be used to select pixels for the scientific analysis of cloud shadow effects.

Shadow modeling in urban environments for solar harvesting devices with freely defined positions and orientations

As a sustainable alternative regarding environmental impact, cost-effectiveness, and social integration, solar energy is expected to become an ever more ubiquitous part of our intricate human world. Dropping prices and growing demand are making it more viable for a variety of solar devices to be implemented in urban and other complex environments. From devices helping people meet their energy needs to solar-powered drones fulfilling urban services like maintenance, security, carrying goods, or even transporting people. These environments involve constrained and dynamic conditions, encouraging the use of solar harvesting devices that can freely adopt tailor-made positioning and tracking strategies to make the most of available resources. A crucial challenge is improving the geometrical flexibility and efficiency of modeling capabilities. In particular, developing practical approaches that account for detailed shadow effects in complex scenarios can be computationally challenging, and it is not clear how different approaches compare face-to-face in urban contexts and with freely defined harvesting surfaces. In this work, four shadow modeling approaches are developed and demonstrated in urban scenes of varying complexity; accuracy and precision are characterized versus computational cost; run-time trends are analyzed as functions of scene complexity, and energy estimation implications are examined. The approaches converge within 1% deviations, and the highest performing approach is three orders of magnitude faster than the most computationally costly. This work supports the selection and development of accurate, efficient, and flexible modeling frameworks that will play a role in enabling a diverse range of solar harvesting devices in challenging urban environments.

Effect of pile arrangement on lateral response of group-pile foundation for offshore wind turbines in sand

This study presents a series of centrifuge tests to investigate the lateral response of group-pile foundation for offshore wind turbines in ultimate conditions. The pile arrangement is specifically assessed together with the influence of pile number and soil property. The numerical analysis is conducted in ABAQUS and validated. The soil-pile interactions are demonstrated, and a parametric study is performed. The analysis shows that the axial load effect and the shadow effect simultaneously influence the behavior of the pile group. The tensile failure of the back-row pile dominates the total failure. The influence zone of the group-pile falls into 10D (D refer to pile diameter) in front of the front-row pile horizontally and 8D vertically. The front-row pile provides a majority of the lateral resistance while the contribution decreases sequentially to the very back-row. Adding rows to the pile group is more effective than adding columns to enhance the overall capacity, and the middle pile is less effective than the corner pile. A fitted formula is proposed to estimate the Pm by integrating the pile arrangement, pile number, and pile spacing. The reliability is checked against the field and centrifuge tests.

Experimental Investigation on the Concentration Polarization and Power Output of a Reverse Electrodialysis Stack With Permselective Spacers for Different Factors

Abstract The use of permselective spacers in reverse electrodialysis (RED) stack introduces a more severe concentration polarization phenomenon at membrane–solution interfaces in spite of effectively suppressing the spacer shadow effect. In this paper, the concentration polarization phenomenon in RED with permselective spacers is analyzed for different membrane types, numbers of cell pairs, solution concentrations, and temperatures by measuring non-ohmic resistance based on direct and alternating current methods combined with theoretical formula. Experiments on direct current method are further made to determine the influence of concentration polarization on power output and power generation performance of stack for different factors. The results show that the non-ohmic resistance accounts for less than 40% of the total stack resistance. Increasing the flowrate and solution temperature effectively suppresses the concentration polarization in stack and thus is beneficial to improving the power output. However, the membrane type, number of cell pairs, and solution concentration hardly affect concentration polarization. In spite of this, these factors all have a considerable impact on the power generation performance of the stack. Among them, increasing the concentration of concentrated and diluted solutions is most beneficial to improving the power density.

Multiple Stationary Human Targets Detection in Through-Wall UWB Radar Based on Convolutional Neural Network

Ultra-wideband (UWB) impulse radar is widely used for through-wall human detection due to its high-range resolution and high penetration capability. UWB impulse radar can detect human targets in non-line-of-sight (NLOS) conditions, mainly based on the chest motion caused by human respiration. The automatic detection and extraction of multiple stationary human targets is still a challenge. Missed alarms often exist if the detection method is based on the energy of the human target. This is mainly because factors such as the range of the target, the intensity of the respiratory movement, and the shadow effect will make a difference between the energy scattered by targets. Weak targets are easily masked by strong targets and thus cannot be detected. Therefore, in this paper, a multiple stationary human targets detection method based on convolutional neural network (CNN) in through-wall UWB impulse radar is proposed. After performing the signal-to-clutter-and-noise ratio (SCNR) enhancement method on the raw radar data, the range-slow-time matrix is fed into a six-layer CNN. Benefiting from the powerful feature extraction capability of CNN, the target point of interest (TPOI) can be extracted from the data matrix. The clustering algorithm is used to simplify the TPOIs to achieve accurate detection of multiple targets behind the wall. The effectiveness of the proposed method is verified by the experimental data.

The impact of shadow covering on the rooftop solar photovoltaic system for evaluating self-sufficiency rate in the concept of nearly zero energy building

In cities seeking energy self-sufficiency, one of the trends is to pursue nearly zero-energy buildings (nZEB). To achieve this target, reducing energy consumption as well as replacing the traditional energy by renewable energy are two major strategies. The former is limited by the difficulty in lowering energy consumption in daily life, so the latter has more potential. Solar photovoltaic systems are a popular means to reach the goal of self-sufficiency in cities, and those on rooftops have the highest efficiency. Shadow from surrounding buildings affects the energy generation but this research found that the impact of shadow is generally limited. Only buildings of less than 3 storeys might suffer serious shadow covering and those higher than this mainly reduce their productivity by only about 1%. However, although lower buildings experience shadow effects, they are the main energy generators due to their low energy self-consumption. For example, the energy shortage of the tallest building in this case study could be covered by a 1-storey building with 10.33 times area. This research indicated that a fully energy self-sufficient environment can be achieved when the city pattern is designed with consideration of a well-balanced building height arrangement.

LIFE-CLIVUT, ecosystem benefits of urban green areas: a pilot case study in Perugia (Italy)

Trees have a great value in terms of ecosystem services in urban areas. LIFE CLIVUT is an “Information and Governance” European project developed in 4 Mediterranean Cities, with the goal of increasing the knowledge and awareness of citizens, especially young people, on the importance of the presence and good management of urban trees to mitigate the “Heat Island” effects. The data collected on the value of tree heritage and their future potential are used to design a green asset management strategy that will help urban planners adopt better practices for the mitigation of the effects of climate change in urban environments. This paper illustrates the results of tree census activity in four urban green areas of Perugia, Central Italy, that will be compared with those recorded in others cities involved in the project. Dendrometric parameters (diameter at breast height, tree height, first branch height, max and min crown width, crown shape and density) were recorded in situ using a dedicated software operating through a web app (“Clivut-Treedb”). The following ecosystem services were estimated: CO2 sequestration, particulate matter (PM) absorption, shadow effect, biodiversity indexes. Several tree species characterized by important wood structures during their adult phase, such as Pinus pinea, Quercus ilex, Q. pubescens, Ulmus carpinifolia, Populus alba and Aesculus hippocastanum showed the highest estimates of CO2 stored. Q. ilex was the most efficient species in particulate adsorption, showing similar estimates (about 60 g PM10 tree-1 year-1) in the 3 oldest green areas established in the 1980s, while the youngest plantations (dating back to 2005) absorbed about 10 g tree-1 of PM10 per year. In terms of the potential cooling effect of trees, preliminary estimates of the shaded areas highlighted the difference between the older green areas (about 50% of shading) compared to the younger ones (about 15% and 8%).

Illumination Invariance Adaptive Sidewalk Detection Based on Unsupervised Feature Learning

To solve the problem of road recognition when the robot is driving on the sidewalk, a novel sidewalk detection algorithm from the first-person perspective is proposed, which is crucial for robot navigation. The algorithm starts from the illumination invariance graph of the sidewalk image, and the sidewalk “seeds” are selected dynamically to get the sidewalk features for unsupervised feature learning. The final sidewalk region will be extracted by multi-threshold adaptive segmentation and connectivity processing. The key innovations of the proposed algorithm are the method of illumination invariance based on PCA and the unsupervised feature learning for sidewalk detection. With the PCA-based illumination invariance, it can calculate the lighting invariance angle dynamically to remove the impact of illumination and different brick colors’ influence on sidewalk detection. Then the sidewalk features are selected dynamically using the parallel geometric structure of the sidewalk, and the confidence region of the sidewalk is obtained through unsupervised feature learning. The proposed method can effectively suppress the effects of shadows and different colored bricks in the sidewalk area. The experimental result proves that the F-measure of the proposed algorithm can reach 93.11% and is at least 7.7% higher than the existing algorithm.

Frequency-comb-induced radiation pressure force in dense atomic clouds

We investigate the frequency-comb-induced radiation pressure force acting on a cloud of cold 87 R b atoms. Reduction and spectral broadening of the frequency comb force are observed as the cloud’s optical thickness is increased. Since the radiation pressure force is uniquely determined by light scattered by an atomic cloud, we discuss different scattering mechanisms and point to the shadow effect as the dominant mechanism affecting the FC-induced force in resonantly excited dense atomic clouds. Our results improve the understanding of the interaction of frequency comb light with many-atom ensembles, which is essential for novel frequency comb applications in simultaneous multispecies cooling and self-ordering, multimode quantum memories, and quantum computing.

Effect of shadow on atmospheric and topographic processed NDSI values in Chenab basin, western Himalayas

The present study was undertaken in the Chenab basin, western Himalayas to explore the effect of shadow on atmospherically and topographically corrected normalized difference snow index (NDSI) values. The research was conducted using the Landsat-8 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) datasets of two time periods i.e., February 2015 and February 2018. Our results suggested that total snow cover area (SCA) computed using NDSI from raw satellite images, under estimated SCA (viz. 10,938.66 and 7739.97 Km2); relative to atmospherically corrected (AC) (14,819.01 and 11,199.7 Km2) and topographically corrected (TC) (14,882.07 and 11,188.18 Km2) images during both the time periods (i.e., 2015 and 2018, respectively). This is mainly due to the non-identification of snow pixels in the shadow regions of raw imageries. Maximum SCA lies in the higher NDSI range in case of AC and TC images, unlike raw image where maximum SCA lies in lower NDSI range for both sunlit and shadow test sites. In the sunlit and shadow terrains, minimum NDSI values were found to be higher for TC images as compared to AC images, except few observations which exhibited similar values for both AC and TC images. In case of maximum NDSI values, most of the observations exhibited similar values for both AC and TC images, except few observations which depicted higher maximum NDSI value in AC images as compared to TC images in both the terrains. This observation ascertains the narrow range of NDSI values for TC images as compared to AC images, which could be attributed to reduced background reflection and low atmospheric scattering in the TC images. Comparison among shadow and sunlit snow terrains, reveals low values of minimum and maximum NDSI in the shadow site, which is ascertained by significant (p < 0.001) t-values of means difference between shadow and sunlit terrains. Moreover, snow surface temperature (SST) values computed for both the time periods, reveal low SST values for shadow sites (t-values −5.1 and − 10.57 for minimum SST, and − 9.1 and − 12.61 for maximum SST for the years 2015 and 2018, respectively) as compared to sunlit sites, and this observation validates that minimum amount of solar radiation reaches the shadow sites. Thus, it is concluded that AC and TC are helpful for delineation of snow pixels under shadow, but shadow has a significant impact on the spectral reflectance of snow, even in the AC and TC images. The influence of shadow should be taken into account for accurate estimation of physical properties and broadband albedo of the snow.

EFFECTS OF SUNLIGHT AND SHADOW ON THE SURFACES OF PIGEON TOWERS IN CENTRAL ASIA: CASE STUDIES IN IRAN, QATAR, EGYPT AND SAUDI ARABIA

In many parts of the world, especially Central Asia, pigeon towers have been constructed as traditional buildings with different forms and types to keep pigeons. These buildings are cylindrical, cubic, dome-like and multi-cylinder in shape. This study was conducted to identify the effects of sunlight and shadow on the surfaces of pigeon towers in Iran, Qatar, Egypt, and Saudi Arabia with hot and dry or humid climates. Several pigeon towers with different types and structures in these countries were selected and modeled in detail in Rhino 5. Radiance and Ecotect were then employed to measure solar radiation and shadow on the surfaces of the pigeon towers on the hottest day of the year. According to the graphical and numerical results obtained, sunlight and shadow differently affected the surfaces of the different pigeon towers. The effect level of sunlight and shadow on the single-form pigeon towers was higher than on the vaults. In fact, solar radiation was lower and shadow was higher per square meter of the surfaces of the vaults constructed as pigeon towers in close proximity. These houses were therefore found to be the optimal type for the hot and dry or humid climate in Central Asia.

Automatic Semantic Segmentation of Benthic Habitats Using Images from Towed Underwater Camera in a Complex Shallow Water Environment

Underwater image segmentation is useful for benthic habitat mapping and monitoring; however, manual annotation is time-consuming and tedious. We propose automated segmentation of benthic habitats using unsupervised semantic algorithms. Four such algorithms––Fast and Robust Fuzzy C-Means (FR), Superpixel-Based Fast Fuzzy C-Means (FF), Otsu clustering (OS), and K-means segmentation (KM)––were tested for accuracy for segmentation. Further, YCbCr and the Commission Internationale de l’Éclairage (CIE) LAB color spaces were evaluated to correct variations in image illumination and shadow effects. Benthic habitat field data from a geo-located high-resolution towed camera were used to evaluate proposed algorithms. The Shiraho study area, located off Ishigaki Island, Japan, was used, and six benthic habitats were classified. These categories were corals (Acropora and Porites), blue corals (Heliopora coerulea), brown algae, other algae, sediments, and seagrass (Thalassia hemprichii). Analysis showed that the K-means clustering algorithm yielded the highest overall accuracy. However, the differences between the KM and OS overall accuracies were statistically insignificant at the 5% level. Findings showed the importance of eliminating underwater illumination variations and outperformance of the red difference chrominance values (Cr) in the YCbCr color space for habitat segmentation. The proposed framework enhanced the automation of benthic habitat classification processes.

Automated retinal layer segmentation in optical coherence tomography images with intraretinal fluid

We propose a novel retinal layer segmentation method to accurately segment 10 retinal layers in optical coherence tomography (OCT) images with intraretinal fluid. The method used a fan filter to enhance the linear information pertaining to retinal boundaries in an OCT image by reducing the effect of vessel shadows and fluid regions. A random forest classifier was employed to predict the location of the boundaries. Two novel methods of boundary redirection (SR) and similarity correction (SC) were combined to carry out boundary tracking and thereby accurately locate retinal layer boundaries. Experiments were performed on healthy controls and subjects with diabetic macular edema (DME). The proposed method required an average of 415[Formula: see text]s for healthy controls and of 482[Formula: see text]s for subjects with DME and achieved high accuracy for both groups of subjects. The proposed method requires a shorter running time than previous methods and also provides high accuracy. Thus, the proposed method may be a better choice for small training datasets.

Editorial Preface to Special Issue: Exploring the impact of Andean uplift and climate on life evolution and landscape modification: From Amazonia to Patagonia

• Uplift of the Northern Andes (from Peru to Colombia) took place from Late Cretaceous to Paleocene (72 and 60 Ma), and was driven by collision of the South American plate with the Caribbean Arch. This process affected drainage directions and paleogeography shaping the present Andes configuration. • Studies in the Northern Andes concur with Late Cretaceous tectonism and suggest that uplift took place in three-stages. During the final Neogene uplift stage, the Antioquia plateau (Central Cordillera, Northern Andes) is thought to have achieved altitudes higher than present. • Subsurface processes, such as slab-flattening drove uplift in Central Cordillera (Northern Andes) and caused an asymmetric topography that affected drainages and biodiversity development. • Climate as a driver of mountain uplift remains contentious, but it is clear that uplift strongly affects climate and environment, due to the orographic rain shadow effect. • Multiple studies found that Andean uplift played a key role in shaping the evolutionary history and biodiversity patterns in both plants and animals, even in mutualistic species relationships. The effect of uplift on biogeographic history is not limited to the Andes mountains, but also extends into the Amazon drainage basin with soils in the western Amazonia being most species rich. During the Neogene, eastern Amazonia gradually became species-enriched through biotic interchange. • The effects of Andean uplift on biota add to other fundamental factors, such as climate, environment and dispersal, all of which contribute to the modern biodiversity patterns in South America and their evolutionary history. • The Neotropics were hot and humid during Eocene global warming. However, paleobotanical studies in the Northern Andes suggest that during towards the end of the Eocene a shift towards arid and seasonal climatic conditions occurred. In western Amazonia the EOT is further marked by a sea level drop, and a shift from deltaic to fluvial conditions that is accompanied by a decline in species richness. • In Patagonia the Oligocene ‘icehouse’ is characterized by a species poor assemblage. Towards the MCO there is an increase in species diversity with a subsequent decline in the MMCT. The biggest paleobotanical change, however, occurs in the late Miocene and is marked by the rise in arid taxa. This coincides with the uplift of the easternmost flank of the Andes and formation of a rain shadow. Aridification and sea level drop was initiated in the MMCT and culminated in the late Miocene. In the Northern Andes this transition is recognized by a dramatic change in paleosoil profiles. • Marine incursions and fluctuating sea level played an important part in Amazonia's history and evidence of this can be found in middle and late Miocene deposits in the western Amazon. Sediment records in the large Pebas wetland system (western Amazon) indicate that orbital forcing controlled sedimentation while the towering Central and Northern Andes provided the sediment supply. • Holocene records of Amazonia suggest rainforest trees are resilient to natural drying but not to fire and deforestation. A stark warning that human influence is more devastating than climate change.

Iris recognition method based on segmentation

The development of science and studies has led to the creation of many modern means and technologies that focused and directed their interests on enhancing security due to the increased need for high degrees of security and protection for individuals and societies. Hence identification using a person's vital characteristics is an important privacy topic for governments, businesses and individuals. A lot of biometric features such as fingerprint, facial measurements, acid, palm, gait, fingernails and iris have been studied and used among all the biometrics, in particular, the iris gets the attention because it has unique advantages as the iris pattern is unique and does not change over time, providing the required accuracy and stability in verification systems. This feature is impossible to modify without risk. When identifying with the iris of the eye, the discrimination system only needs to compare the data of the characteristics of the iris of the person to be tested to determine the individual's identity, so the iris is extracted only from the images taken. Determining correct iris segmentation methods is the most important stage in the verification system, including determining the limbic boundaries of the iris and pupil, whether there is an effect of eyelids and shadows, and not exaggerating centralization that reduces the effectiveness of the iris recognition system. There are many techniques for subtracting the iris from the captured image. This paper presents the architecture of biometric systems that use iris to distinguish people and a recent survey of iris segmentation methods used in recent research, discusses methods and algorithms used for this purpose, presents datasets and the accuracy of each method, and compares the performance of each method used in previous studies

A new GIS-based algorithm to estimate photovoltaic potential of solar train: Case study in Gyeongbu line, Korea

Photovoltaic (PV) power generation is considered a forward-looking industry. Nevertheless, solar energy is yet to become a direct source of electric power for mobile vehicles. Recently, there have been cases where solar panels were attached to the roof of trains to generate electricity. In this study, a method was devised to estimate the power generated by a solar train with panels. The solar irradiance on the roof of a moving train was calculated with respect to the location and time of the train, as well as the shadow effects of obstacles. The preprocessing of the input data required for calculating solar irradiation was executed through Geographic Information Systems, and finally, an algorithm for calculating solar irradiation and power generation was developed. With the algorithm-embodied Graphical User Interface, when spatial information of various routes is provided, the PV potential for each route can be calculated. Experimental calculations were conducted on the Gyeongbu line in Korea. During train operation, 122.15 MWh of power can be generated per year, with a reduction of 56 tons of CO2. The results of this preliminary evaluation are expected to accelerate the growth of the solar train industry.