Shadow Effect Research Articles

Surrogate Modeling Strategy for Urban Building Energy Simulation in Early-Stage Urban Design: A Case Study of Energy-Efficient Neighborhood Design in Seoul

This study focuses on developing an efficient surrogate modelling strategy for early-stage urban design, aiding in energy-efficient residential neighborhood design in Seoul. The methodology involves devising a design schema with important design parameters, generating 1,000 random designs via Latin Hypercube Sampling, and simulating each design’s energy use considering microclimate and shadow effects. Polynomial regression is used to develop surrogate models based on those energy simulation results, which is further validated with energy use measurements of real neighborhoods in Seoul. The developed surrogate model can provide quick evaluation of energy use with a moderate level of accuracy for early-stage energy efficient neighborhood design.

Continuous Change Detection of Flood Extents With Multisource Heterogeneous Satellite Image Time Series

Flood monitoring is of crucial importance for protecting lives and properties. Change detection (CD) methods on multi-source remote sensing images have been widely used for flood extent monitoring. In this paper, we propose a spatiotemporal fusion CD (STFCD) algorithm, exploiting the spatial dependence and temporal interaction of multi-source heterogeneous (MSH) satellite image time series (SITS), to realize improved flood CD performance in comparison with existing methods. The proposed STFCD algorithm mainly contains two steps, i.e., spatial clustering and temporal fusion. In the spatial clustering step, we propose a sparse Markov random field (MRF)-based strategy to exploit contextually spatial features in each image of MSH-SITS, which provides a larger local receptive field than the commonly used MRF. In the temporal fusion step, the historical information of flood detection results is employed as constraints to effectively reduce the effects of terrain shadows in synthetic aperture radar (SAR) images and cloud shadows and topography shadows in optical images on flood CD results of existing methods in accordance with the temporal dependence among MSH-SITS. Experiments on real MSH-SITS (containing Gaofen-1, Gaofen-3, Gaofen-6, Sentinel-1, and Sentinel-2 satellite images) covering Chinese Amur and Huma Rivers show that the overall flood CD accuracy of our proposed STFCD algorithm is higher than the other commonly used algorithms for CD of flood extents and demonstrate the robustness of our proposed STFCD algorithm.

Influence of Wind Turbine Structural Parameters on Wind Shear and Tower Shadow Effect

To overcome the problems of natural decreases in power quality, and to eliminate wind speed fluctuation due to wind shear and tower shadow effect arising from wind turbine structural parameters, an improved prediction model accounting for the dual effect of wind shear and tower shadow is, in this paper, built. Compared to the conventional prediction model, the proposed model contains a new constraint condition, which makes the disturbance term caused by the tower shadow effect always negative so that the prediction result is closer to the actual situation. Furthermore, wind turbine structural parameters such as hub height, rotor diameter, the diameter of the tower top, and rotor overhang on wind shear and tower shadow effect are also explored in detail. The results show that the wind shear effect became weaker with the increase in hub height. The hub height is independent of the tower shadow effect. The rotor diameter is positively correlated with the wind shear and tower shadow effect. The tower shadow effect is positively correlated with the diameter of the tower top and negatively correlated with the rotor overhang.

Innovative Variational AutoEncoder for an End-to-End Communication System

Powered by deep learning (DL), autoencoders (AE) end-to-end (E2E) communication systems have been developed to merge all physical layer blocks in traditional communication systems and have achieved great success. In this paper, a new probabilistic model, based on the variational autoencoders (VAE), is proposed for short packet wireless communication systems. Using this new approach, the information messages are represented by the so called packet hot vectors (PHV) which are inferred by the VAE latent random variables (LRVs). Then only LRVs’ parameters can be transmitted through the physical wireless channel. This results in a significant improvement in spectral efficiency when compared with the pure AE approach where a longer hot vectors are to be transmitted. Specific VAE models have been developed for both binary (BPSK) as well as Quadrature phase shift keying (QPSK) systems. Simulation and numerical results are given to demonstrate the performance of the proposed method in different real scenarios, including Rayleigh and Rician fading channels with Shadowing and Doppler effects. Our simulation and numerical results show that the new proposed VAE with a DL classifier can provide an improved symbol error rate (SER) performance than both the baseline AE and the classical Hamming code with hard decision decoding. Furthermore, as far as the spectral efficiency of the proposed method is concerned, we show that using two channels in the proposed VAE performance exceeds the 7 channels baseline AE.

Mapping the Impact of Contractual Governance and Trust on Project Performance in Construction Industry— the moderating effect of shadow of future

Mapping the Impact of Contractual Governance and Trust on Project Performance in Construction Industry— the moderating effect of shadow of future

Mapping the impact of contractual governance and trust on project performance in construction industry – the moderating effect of shadow of future

Mapping the impact of contractual governance and trust on project performance in construction industry – the moderating effect of shadow of future

Automatic Shadow Generation via Exposure Fusion

Shadow generation aims to generate a plausible shadow for the inserted foreground object in a composite image. Besides the composite image and the associated mask of the inserted foreground object, existing methods also require a mask of all background objects as well as their shadows as an auxiliary input, which is laborious in practical applications. Meanwhile, most existing methods use a linear illumination transformation to darken the shadow region, which is prone to produce unrealistic shadows especially when background illumination is complex. To address these problems, this paper proposes an automatic shadow generation method, which avoids the laborious acquisition of the background object masks while harmonizing the shadow region to achieve plausible shadow effects. Specifically, to implicitly exploit background illumination to infer the shadow shape of the inserted foreground object, we first propose a Hierarchy Attention U-Net (HAU-Net) to sequentially build global interactions between the foreground object and background across spatial and channel dimensions. Since the spatial-variant property of the shadow, we formulate shadow harmonization as an exposure fusion problem and propose an Illumination-Aware Fusion Network (IFNet), which uses an improved illumination model with a double linear transformation to produce multiple under-exposure images of the shadow region. IFNet then learns pixel-wise fusion kernels that consider the local smoothness of the shadow to fuse the composite image with these under-exposure images to generate the realistic shadow of the foreground object. Extensive experiments on the DESOBA and Shadow-AR datasets demonstrate that our method achieves state-of-the-art performance for shadow generation on both the BOS and BOS-free test images.

Construction of an approach for evaluation of droplet collision models under DDM framework based on an improved Beer's law

In spray simulations, uncertainties in the collision incidence predictions always exist for droplet collision models under the discrete droplet model framework. In this study, Beer's law, which is used for electromagnetic radiation and light absorption, was improved to evaluate the accuracy of droplet collision models by eliminating the shadow effect among the light-absorbing (stationary) parcels. In addition, the range of parcel numbers in the computational domain was carefully calibrated to ensure the appropriate implementation of Beer's law. Based on the improved Beer's law, a theoretical evaluation method of the computational efficiency of droplet collision models was proposed to conduct a qualitative analysis. Using the above methods, a complete approach for evaluating the accuracy and efficiency of droplet collision models was established. Three representative collision models, including the O'Rourke model, the Nordin model, and the no-time-counter (NTC) model, as well as a new hybrid stochastic/trajectory (HST) collision model, were evaluated comprehensively. The convergence and dependence of the predicted collision incidence on various factors, including parcel radius, grid size, reference frame velocity, and droplet number represented by one parcel, were investigated. It was found that the HST model shows relatively better performance on the collision incidence compared with the other collision models in most cases, especially when one parcel represents multiple droplets. The NTC model achieves the highest computational efficiency, and the computational cost of the construction of the adaptive collision cells in the NTC model and the HST model constitutes a major proportion of the total time consumption.

A Subpixel Mapping Method for Urban Land Use by Reducing Shadow Effects

Urban land use classification is significant for urban development planning. Considering complex environments of urban surface features, traditional semantic segmentation methods are difficult to solve the problems of mixed pixels and limited spatial resolution of images. The subpixel mapping technology is an effective method to solve the above problems in urban land use classification. However, traditional subpixel mapping methods are sensitive to mountain shadow, high-rise building shadow and impermeable surface heterogeneity, resulting in false classification. Therefore, we propose a subpixel mapping method that can reduce the shadow effect. This method uses a multi-index feature fusion strategy to optimize the abundance of the shadow errors in the abundance image, and uses a super-resolution reconstruction neural network model to reconstruct the optimized abundance image for the subpixel mapping of urban land use. Experiments were conducted on sentinel-2 images obtained over Yuelu District of Changsha City, Hunan Province, China. The experimental results show that the method proposed in this article can effectively overcome the influence of building shadows and mountain shadows in urban land cover classification and is superior to traditional subpixel/pixel spatial attraction model, radial basis function, super-resolution subpixel mapping, and other methods in the effect and accuracy of urban land use subpixel mapping.

Birth of the Taklamakan Desert: When and How?

<abstract> <p>The Taklimakan Desert is one of the largest deserts and sand seas in the world and plays a critical role in the global aerosol (eolian dust) system, impacting both climate and ecosystems on continents and over oceans. Geological evidence suggests that much of the western part of the Tarim Basin, which is now covered by the vast sandy desert, was once the eastern fringe of the Paratethys Sea. After the retreat of the sea, the area transformed into a fluvial system before becoming an mountain front alluvial fan system due to the uplift of the northern Tibetan Plateau. Deserts developed during this period, as sand dunes and eolian loess deposits were formed and buried to become part of the sedimentary sequence. Dating of these sequences suggests that the Taklimakan Desert, in a similar form to what we observe today, came into existence no later than 25 million years ago. Taklimakan Desert was formed as a response to a combination of widespread regional aridification due to the rain shadow effect and increased erosion in the surrounding mountain fronts, both of which are closely linked to the tectonic uplift of the Tibetan-Pamir Plateau and Tian Shan, which had reached a climatically sensitive threshold at this time.</p> </abstract>

Comparison of Autonomous and Manual UAV Flights in Determining Forest Road Surface Deformations

The deterioration of the surface of forest roads is an important factor affecting the safe navigation of vehicles and traffic safety. In addition to traditional methods, automated methods are also used to determine the deterioration of the road surface. UAV systems, which are among the automated methods, are widely used to determine surface deformations with high accuracy. This study aimed to evaluate the advantages and disadvantages of two different flight modes of UAV, including autonomous flight and manual flight, in mapping road surface deformations. Within the scope of this study, the 50-meter section of the Type B forest road located in Kardüz Forest Management Chief (Düzce/Türkiye), was selected. For this study, first the pros and cons of the autonomous and manual flight data acquisition process were evaluated. Then, the photogrammetric data processing results were compared in terms of data size, with precision and accuracy. In addition, the deformation status on the surface within the selected road was determined using the average Z value differences obtained with two flight methods. The result of the study showed that, the number of images obtained from manual flights was 5.5 times higher than from autonomous flights and the flight time was taken four times longer. The average ground sampling distance of the orthophotos generated from two different light modes indicated that the manual flight mode provided seven times higher resolution than autonomous flight. Moreover, the results from the statistical tests for the two flight modes showed differences. When manual flights and autonomous flights are evaluated in terms of reducing the shadow effect, manual flights can be considered more advantageous. Furthermore, it was found that the dynamic mobility of erosion and accumulation on the road surface continued in time series in both flight methods.

Ray Tracing in Computer Graphics

The research is about the development of light and shadow in video games on the Internet, and also to compare the light and shadow effects displayed on video game screens using different techniques. Then, the types and history of ray tracing technology are explained, its working principle is studied, and its pros and cons are analyzed. After the research, this paper finally determined that a viable ray tracing technique in the current society is hybrid ray tracing, which is a combination of forward and backward ray tracing. Because forward ray tracing methods are too inefficient while backward ray tracing methods cannot calculate and render the light entering in front of the lens. By studying 3 main hybrid ray tracing, their advantages, disadvantages and suitable application scenarios are analyzed and determined in detail. Finally, the development and improvement of the technology in recent years are discussed. Currently, analyses of a particular ray tracing technology do exist in the market. However, there are still few articles that explore all available ray tracing technologies, taking the reader through the history and current state of ray tracing development and giving developers a more visual comparison to help them choose the most appropriate technology for the scenarios they want to develop.

Electrodialysis desalination: The impact of solution flowrate (or Reynolds number) on fluid dynamics throughout membrane spacers

The incorporation of a spacer among membranes has a major influence on fluid dynamics and performance metrics. Spacers create feed channels and operate as turbulence promoters to increase mixing and reduce concentration/temperature polarization effects. However, spacer geometry remains unoptimized, and studies continue to investigate a wide range of commercial and custom-made spacer designs. The in-depth discussion of the present systematic review seeks to discover the influence of Reynolds number or solution flowrate on flow hydrodynamics throughout a spacer-filled channel. A fast-flowing solution sweeping one membrane's surface first, then the neighboring membrane's surface produces good mixing action, which does not happen commonly at laminar solution flowrates. A sufficient flowrate can suppress the polarization layer, which may normally require the utilization of a simple feed channel rather than complex spacer configurations. When a recirculation eddy occurs, it disrupts the continuous flow and effectively curves the linear fluid courses. The higher the flowrate, the better the membrane performance, the higher the critical flux (or recovery rate), and the lower the inherent limitations of spacer design, spacer shadow effect, poor channel hydrodynamics, and high concentration polarization. In fact, critical flow achieves an acceptable balance between improving flow dynamics and reducing the related trade-offs, such as pressure losses and the occurrence of concentration polarization throughout the cell. If the necessary technical flowrate is not used, the real concentration potential for transport is relatively limited at low velocities than would be predicted based on bulk concentrations. Electrodialysis stack therefore may suffer from the dissociation of water molecules. Next studies should consider that applying a higher flowrate results in greater process efficiency, increased mass transfer potential at the membrane interface, and reduced stack thermal and electrical resistance, where pressure drop should always be indicated as a consequence of the spacer and circumstances used, rather than a problem.

The Economic Dimension of Using the Integration of Highway Sound Screens with Solar Panels in the Process of Generating Green Energy

One of the research areas related to renewable energy sources is the search for new applications for currently used technologies. An important postulate is to achieve the synergy effect by including the existing infrastructure in this process. The innovation described in this article is the integration of solar cells into a modular sound barrier on the highway. The contribution of this article is mainly based on the introduction of the potential feasibility of the first Turkish solar highway, describing the installation of PV systems based on a multi-criteria evaluation (azimuth angle, loss of shade, and dirt). The aim of the study is to determine the economic dimension by examining the costs of implementing such an investment and answering the question concerning the efficiency of solar cells on sound barriers. The research took into account various scenarios regarding the shadow effect and inclination of solar panels and their impact on solar energy production in the example of a given case study, an identified urban area. The research is limited to the model for assessing the feasibility of solar cells on sound barriers based on NPV and the essence of the relationship regarding the LCOE averaged electricity costs. In this study, the function and technical parameters of solar cells are not specified, but the article is limited to the basic information and characteristics required to investigate the payback period and profitability of an investment. Research has shown that if the investment is carried out in accordance with the proposed model, the expected amount of energy produced is 62,257 kWh per year. This value corresponds to the average consumption of electricity in a household by 24 apartments for a given destination, or to providing energy for a selected electric vehicle for one year of its operation, at the same time leading to a significant reduction of CO2. The presented research can find practical application in the area of developing a strategy for the development and popularization of renewable energy sources while increasing the use of the existing road infrastructure, presenting an important postulate in promoting this type of solution for other geographic destinations.

Climatic definitions of the world’s terrestrial biomes

Question: Is it feasible to establish a classification of large biotic units of the world related to climatic types? Study area: The world. Methods: A total of 616 localities have been selected, their climatic parameters calculated and subjected to a PCA. The climatic characterization of biomes and subbiomes has been completed after data analysis. Results: A hierarchical classification is proposed for the biotic units within four main domains: Cryocratic, Mesocratic, Xerocratic and Thermocratic, divided into 7 ecozones, 9 biomes and 20 subbiomes linked to climatically defined territories. Most of the units are intercontinental. The mountains represent an abbreviated version of the latitudinal zonation and the altitudinal belts are related to the corresponding units of the lowlands. For the bioclimatic units, a parallel classification is proposed to fit with that of the biotic units: 4 Macrobioclimates and 10 bioclimates. Furthermore, 7 ombrotypes and 7 thermotypes are recognized to frame the climatic variation within each climatic territory due to terrain ruggedness, particularly in relation to large or medium sized mountains. Conclusions: The southern hemisphere is substantially more oceanic than the northern hemisphere. This is due to the distribution of the land masses and the modifying effect they have on the flow of air and marine currents. As a result, there is one biome and one subbiome exclusively found in the northern hemisphere (6. Biome of the steppe, and 5.b Continental scrub and woodlands subbiome) and two others which are almost confined to it (2. Biome of the boreal forest, and 3. Biome of the temperate deciduous forests). The 7. Biome of the deserts and 5. Biome of the temperate aridiestival evergreen forests and shrublands occur on the western side of the continents and expand in their interior favoured by rain shadow and continentality effects. Taxonomic reference: The Plant List (2013). Abbreviations: ITCZ = Inter Tropical Convergence Zone; NH = Northern Hemisphere; PCA = Principal Component Analysis; SH = Southern Hemisphere.

Assessment of Reliability Indicators of Combined Systems of Offshore Wind Turbines and Wave Energy Converters

Marine renewable sources can make a significant contribution to the development of electrical energy generation and can increase the power supply reliability of mineral complexes. The development of alternative energy sources is happening at a fast pace, and this is due to the improvement of technologies that allow for generating more energy and operating in more extreme conditions, with almost no negative effect on the environment. However, currently, renewable sources are not able to meet all the energy requirements of the platforms. Hence, a key point is to gradually introduce and develop new technologies. This article explores the advantages of combining power generation by wave converters and offshore wind turbines. It investigates the possibilities of improving the combined systems’ reliabilities through justification of their mutual topology and accounting for the shadow effect from the wave installations.

Research on control methods and technology for reduction of large-scale wind turbine blade vibration

This paper is mainly devoted to the analysis and suppression of large-scale wind turbine blade vibration. Firstly, the mechanism of blade vibration including waved vibration and shimmy vibration is analyzed in detail and the mathematical model of blade vibration is established. Secondly, the influence of tower shadow effect and wind shear on blade flutter is discussed based on the established blade vibration model. In the end, for the suppression of blade vibration, some control schemes based on individual variable-pitch including blade damping control, LQG control, H∞ control and improved LQG control with optimal disturbance observer proposed in this paper are studied. At the same time, the specific processes of controllers design are given and these algorithms are effectively verified by simulations. The results show that the improved LQG control with optimal disturbance observer has the better suppression effect on blade vibration compared with other methods, which can provide a certain theoretical support to choose the control algorithm in reality.

Signal shadowing during intraoperative optical coherence tomography assisted vitreoretinal surgery: A systemic analysis

AbstractPurpose: To analyse the clinical significance of signal shadowing during intraoperative optical coherence tomography (iOCT) assisted vitreoretinal surgery (PPV) caused by vitreoretinal instruments (VRI), dyes, and vitreous substitutes and to quantify its impact on iOCT imaging.Methods: In this retrospective observational study, imaging data from thirty‐five (35) patients undergoing an iOCT‐assisted PPV with Rescan® 700 (Zeiss, Oberkochen, Germany) were analysed. The iOCT image data were divided into three groups: VRI (17 cases), tissue dyes (8 cases), and vitreous substitutes (10 cases). The images were then post‐processed using a graphic software (histogram, grey level (GL)) and compared with paired image controls without clinically perceptive interference to measure the grade of picture quality distortion. Data were statistically analysed.Results: The intraocular portion of all VRI caused a high average GL interference compared to controls (26.9 ± 2.3 vs. 35.9 ± 0.83; p < 0.05), obscuring the area of interest. The instruments' tips produced a low‐grade shadowing, allowing the underlying tissue to be distinguished. The stains analysed demonstrated a wide interference range, indocyanine green (9.2 ± 1.4) and triamcinolon acetonide (13.9 ± 10.0) showed a high shadowing, while lutein‐based dye (38.4 ± 6.4) and Brilliant Blue (39.9 ± 3.3) exhibited no significant distortion. All vitreous substitutes analysed showed an insignificant shadowing effect on iOCT (Air 42.9 ± 5.1, PFCL 46.0 ± 5.1 vs. 44.5 ± 0.32; p < 0.05).Conclusions: All intraocular instruments showed a significant image interference during iOCT assisted surgery. All dyes except Brilliant Blue produced additional shadowing effect compared to controls. Implementation of new imaging techniques or/and materials with low‐grade interference for surgical instruments could overcome a clinically relevant shadow effect on iOCT and maximize the technology's visual accuracy.

Physics-Based Shadow Image Decomposition for Shadow Removal.

We propose a novel deep learning method for shadow removal. Inspired by physical models of shadow formation, we use a linear illumination transformation to model the shadow effects in the image that allows the shadow image to be expressed as a combination of the shadow-free image, the shadow parameters, and a matte layer. We use two deep networks, namely SP-Net and M-Net, to predict the shadow parameters and the shadow matte respectively. This system allows us to remove the shadow effects from images. We then employ an inpainting network, I-Net, to further refine the results. We train and test our framework on the most challenging shadow removal dataset (ISTD). Our method improves the state-of-the-art in terms of mean absolute error (MAE) for the shadow area by 20%. Furthermore, this decomposition allows us to formulate a patch-based weakly-supervised shadow removal method. This model can be trained without any shadow- free images (that are cumbersome to acquire) and achieves competitive shadow removal results compared to state-of-the-art methods that are trained with fully paired shadow and shadow-free images. Last, we introduce SBU-Timelapse, a video shadow removal dataset for evaluating shadow removal methods.

Effects of yawed inflow and blade-tower interaction on the aerodynamic and wake characteristics of a horizontal-axis wind turbine

The aerodynamic characteristics of a wind turbine change dramatically under the influence of complex inflow and interaction between blade and tower. In this study, detailed full-scale CFD models of NREL 5 MW wind turbine are developed to investigate the specific aerodynamic characteristics with varying yaw angles and wind speeds based on OpenFOAM tool box. The total and local blade aerodynamic loads are analyzed by incorporating the effects of yawed inflow and tower. It is clearly noted that the blade load fluctuation amplitude and influence range due to the presence of tower gradually increase when the yaw angle becomes larger. Moreover, the three-point method is employed to extract the angle of attack (AOA) and induce factor of different blade sections within a rotation period. Generally, the fluctuation amplitudes of AOA and induce factor increase with the increase of yaw angle by ignoring the abrupt change induced by the tower shadow effect. Subsequently, the effects of blade rotation on the aerodynamic force of tower for varying wind speeds and yaw angles are considered, and a “negative pressure” state is observed when the blade passes in front of the tower. Finally, the wake effect under yawed inflow is revealed in details.