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This study evaluates the shadowing effect of existing tunnels on the evolution of soil arching, focusing on the shape of the tunnel (circular and rectangular) through trapdoor experiments. The displacement and shear strain distributions of ground soil resulting from trapdoor movement were estimated using a digital image correlation technique. The results showed that the shadowing effect of the rectangular tunnel was significantly greater than that of the circular tunnel of the same size. The sand above the tunnel was displaced in a double-groove pattern owing to the presence of the tunnel, and the maximum surface settlement occurred between the tunnel boundary and the trapdoor edge. The circular tunnels exhibited consistently higher maximum surface displacements than that in the rectangular tunnels. The shear strain value of soil was lower for the rectangular tunnel case than that for the circular tunnel case. The rectangular tunnels required lesser trapdoor displacement than that of the circular tunnel to obtain the minimum soil arching ratio. The minimum and ultimate soil arching ratios increased as the burial depth ratio increased for both the tunnel shapes. The maximum stress ratio of the tunnel crown was consistently larger for the circular case than for the rectangular case. [ABSTRACT FROM AUTHOR]

This study aimed to synthesize few-layer MoS2 on SiO2/Si using sulfurization chemical vapor deposition toward beyond-5G and 6G communication. Fabric-like MoO3(s) was directly placed onto a SiO2/Si substrate to lower the oxygen potential, which is achieved through a shadowing effect on vaporization. Successful results were achieved, yielding MoS2 thin films with a coverage of more than 74% and a crystal size in the range of 50 to 600 μm. Two distinct pathways for MoS2(s) formation from MoO3(s) via MoO2(s) and MoS3(s) were also uncovered. The shadowing effect of MoO3(s) vaporization facilitated the two-dimensional growth of MoS2 by mitigating oxygen partial pressure. Therefore, sulfurization chemical vapor deposition shows great application potential in synthesizing high-quality MoS2 thin films with substantial crystal size and coverage, making them suitable for next-generation communication devices. [ABSTRACT FROM AUTHOR]

Characteristics of random ocean waves have been measured by different devices, and X-band marine radar is one of the typical devices. This study proposes an enhanced methodology for estimating the significant wave height of ocean waves through the analysis of X-band radar images, particularly leveraging the shadowing characteristics inherent within radar images. The enhancement of the shadowing-based algorithm is achieved by incorporating three different key physical properties of ocean waves. These include the spatial autocorrelation function (SACF) in the Smith function, the orthogonal property of mean surface slopes, and the relationship of high-order spectral moments. The enhanced algorithm is complementarily integrated with fast Fourier transform (FFT)-based spectral analysis, facilitating the determination of significant wave height without the necessity for supplementary reference measurements. Numerical tests have been conducted using synthetic and real radar images corresponding to various sea states to validate the accuracy and reliability of the proposed methodology. The results demonstrate that the proposed techniques consistently improve the estimation accuracy of significant wave heights for both synthetic and real radar images. Even though the measured real radar images used for validation are not exhaustive in terms of the amount of dataset and range of sea state severity, considering that the proposed technique is in its early development stage, it is inspiring that its effectiveness and physical validity have been demonstrated through the present study. [ABSTRACT FROM AUTHOR]

Abstract—A new analytic theory is developed for asymptotic stage of self-catalyzed growth of III–V nanowires (NWs) by molecular beam epitaxy (MBE), where NWs collect all group III atoms deposited from vapor. The shadowing NW length is derived which corresponds for the full shadowing of the substrate surface in MBE. The NW length and radius are derived depending on the effective deposition thickness and MBE growth parameters. It is shown that the NW length increases, and their length decreases with decreasing the array pitch and increasing the V/III flux ratio. [ABSTRACT FROM AUTHOR]

Since the Apollo era, lunar dust has been one of the major problems for lunar surface explorations, since these very abrasive and adhesive grains are harmful for both the instruments and the human beings. Normally, the lunar surface can get charged with an electric field of several V/m, which is not strong enough to launch the dust grains from the surface. However, the electric field may be enhanced when the solar wind and the sunlight are shadowed by an obstacle. Such a shadowing effect can be caused by either a natural topographic feature or a man-made object. Here we study the shadowing effect of a lunar lander with particle-in-cell simulations. It is found that the shadowed region is negatively charged, with a surface potential as low as −30 V and an electric field as large as 20 V/m. A local dust cloud is caused by the electrostatic dust transport around the lander, with a number density of about 104 m−3 at 1 m altitude and up to 105 m−3 near the surface. The surface potential is determined by the temperature of solar wind, but a higher temperature can bring a weaker electric field and a smaller dust cloud, due to the enhanced Debye length. The electrostatic dust transport favors a larger shadowed area, caused by either a larger solar zenith angle or a higher lander height. In addition, the dust transport favors a conductive lander surface, where the maximum dust density can reach 106 m−3. Our results are helpful for the future lunar explorations and have general implications in studying the dust environment of other airless bodies. [ABSTRACT FROM AUTHOR]

In the present study, the AlCoCrNi high-entropy metallic film was deposited on a Si wafer using a magnetron sputtering system. To capture the effects of the sputtering parameters on the microstructure and mechanical properties of the film, the flow rate of Ar gas injected into the chamber (5, 7, and 8 sccm) was controlled. All films were identified as being of BCC phase with compositions of near equiatomic proportions, regardless of the gas flow rates. Nano-scale clusters were observed on the surfaces of all films, and nano-cracks were found in the film deposited at the Ar gas flow rate of 8 sccm, unlike the films deposited at the gas flow rates of 5 and 7 sccm. Detailed microstructural analysis of film deposition at an Ar gas flow rate of 8 sccm indicated that the void boundaries contribute to the formation of nano-cracks. The nano-indentation results indicated that the Ar gas flow rate 5 sccm specimen, with the smallest cluster size at the topmost surface, showed the highest hardness (12.21 ± 1.05 GPa) and Young's modulus (188.1 ± 11 GPa) values. [ABSTRACT FROM AUTHOR]

Characteristics of random ocean waves have been measured by different devices, and X-band marine radar is one of the typical devices. This study proposes an enhanced methodology for estimating the significant wave height of ocean waves through the analysis of X-band radar images, particularly leveraging the shadowing characteristics inherent within radar images. The enhancement of the shadowing-based algorithm is achieved by incorporating three different key physical properties of ocean waves. These include the spatial autocorrelation function (SACF) in the Smith function, the orthogonal property of mean surface slopes, and the relationship of high-order spectral moments. The enhanced algorithm is complementarily integrated with fast Fourier transform (FFT)-based spectral analysis, facilitating the determination of significant wave height without the necessity for supplementary reference measurements. Numerical tests have been conducted using synthetic and real radar images corresponding to various sea states to validate the accuracy and reliability of the proposed methodology. The results demonstrate that the proposed techniques consistently improve the estimation accuracy of significant wave heights for both synthetic and real radar images. Even though the measured real radar images used for validation are not exhaustive in terms of the amount of dataset and range of sea state severity, considering that the proposed technique is in its early development stage, it is inspiring that its effectiveness and physical validity have been demonstrated through the present study.

Cross-body link refers to the wireless connection between two wearable devices when they are both worn or near the body, such as that of a virtual reality (VR) headset and its controllers. It is one of the most challenging wireless scenarios in terms of link budget, due to severe shadowing effects when controllers are placed at the back side of the body. This is especially true when the users are in an outdoor environment where there is less reflection from the surrounding. This paper investigates the wireless propagation mechanism, including line-of-sight, ground reflection, and creeping waves. Based on that, through simulation and measurement experiments, this work analyzes the impact of different antenna designs on the cross-body link of VR/AR devices, including one novel compact low-profile antenna named Distributed Monopole (DM), and two conventional antennas. Due to the polarization advantages, both the novel DM antenna and the patch antenna shows significantly better performance than the dipole antenna. The DM antenna also shows a 2–4 dB advantage over the patch antenna due to its omni-directional field pattern. Time-domain analysis and statistical approaches are suggested to fully characterize the cross-body link of VR/AR antennas and body propagation.

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The evaluation of laser speckle statistics at different illumination angles is highly significant in industry, e.g., non-destructive surface inspection or motion analysis and measurement. Current speckle theories overlook the shadowing effect and the shape of laser spot, leading to inaccurate speckle statistics at large incident angles. This paper presents an oblique-incidence statistical model (OISM) for calculating subjective speckle statistics under oblique illumination. The model introduces an autocorrelation function of the scattered wave with shadowing effects and considers laser spot deformation by oblique illumination. With these additions, OISM allows for incident angles ranging from 0 ° to 80 ° and any lateral correlation length of the surface-height fluctuations. Extensive experiments demonstrate the accuracy of the proposed model, especially when the lateral correlation length is small or the illumination angle is close to 80 °. [Display omitted] • Subjective speckle statistics are affected by shadowing effect and laser spot shape. • Shadowing effects and laser spot deformation fundamentally affect speckle statistics. • The speckle shape is gradually compressed due to increasing incident angles. [ABSTRACT FROM AUTHOR]

This paper proposes a 2-dimensional low computational cost mirror Kirchhoff approximation (MKA) and the design of simulation parameters to accurately predict the shadowing gain for an arbitrarily shaped conductor cylinder. The disadvantages of the conventional MKA, such as lacking designs for the simulation parameters and a limited applicable range, have motivated the establishment of an extended MKA. The authors propose the design of the simulation parameters for MKA. The applicable range of MKA is extended to an arbitrarily shaped cylinder by multiple planes. This work finds that only the space domain of the zeroth plane and the angular spectrum domain of the last plane need separate windowing functions for accuracy and the calculation time. The details of those windowing functions are introduced, and their necessities are explained. The authors validate the proposed method for an elliptical conductor cylinder with the size of the human body at millimeter waves (17 GHz – 66.5 GHz). Simulations are conducted by changing the object’s location, direction, and frequencies. The results show that the proposed method presents a good accuracy, which has a low root-mean-square error of less than 0.5 dB by comparing it with a full-wave approach based on the method of moment. Furthermore, the calculation time is improved by 1.4 – 67.2 times by comparing it with the uniform theory of diffraction using special functions.

This work aims at inspecting the device operation and performance of a novel flipped npn microstructure solar cell based on low-cost heavily doped silicon wafers. The flipped structure was designed to eliminate the shadowing effect as applied in the conventional silicon-based interdigitated back-contact cell (IBC). Due to the disappearance of the shadowing impact, the optical performance and short-circuit current density of the structure have been improved. Accordingly, the cell power conversion efficiency (PCE) has been improved in comparison to the conventional npn solar cell microstructure. A detailed analysis of the flipped npn structure was carried out in which we performed TCAD simulations for the electrical and optical performance of the flipped cell. Additionally, a comparison between the presented flipped microstructure and the conventional npn solar cell was accomplished. The PCE of the conventional npn structure was found to be 14.5%, while it was about 15% for the flipped structure when using the same cell physical parameters. Furthermore, the surface recombination velocity and base bulk lifetime, which are the most important recombination parameters, were studied to investigate their influence on the flipped microstructure performance. An efficiency of up to 16% could be reached when some design parameters were properly fine-tuned. Moreover, the impact of the different physical models on the performance of the proposed cell was studied, and it was revealed that band gap narrowing effect was the most significant factor limiting the open-circuit voltage. All the simulations accomplished in this analysis were carried out using the SILVACO TCAD process and device simulators. [ABSTRACT FROM AUTHOR]

Understanding the flood impact dynamics on buildings is still a major challenge, especially considering the built environment. Motivated by the problem of the flood-structure interaction, this study experimentally measured loading conditions onto three-dimensional buildings to investigate flood loading mechanisms considering the shadowing effect. A total of 162 scenarios concerning different values of the initial impoundment depth (Hi), aspect ratio of the front building (α), relative longitudinal spacing (λ), and orientation of the front building (θ) were undertaken. Both flood loading mechanisms with and without considering the shadowing effect were discussed elaborately. Results showed that the existence of the front building leads to a dramatic change in flow regime upstream of the rear building, and the shadowing effect highly depends on the development of the flood flow reconstruction. In addition, the shadowing index ηF was introduced, and it was more sensitive to λ than α and θ. When the λ was less than 3.5, relative optimal values of θ were 50°, 45°, and 0° for the scenarios with α=0.5 , α=1.0 , and α=1.5 , respectively. There was a negative dependence of the flood hazard level on the shadowing index. Besides, the modified formula of the maximum flood impact force considering the shadowing effect and fitting formulas between λ and ks were obtained. This research supports the study of flood loading mechanisms and is beneficial to the plan and design of safer building clusters. [ABSTRACT FROM AUTHOR]

In offshore oil and gas exploration and transportation, it is often encountered that the multi-floating structures work side by side. In some sea conditions, there is a strong coupling between the multi-floating structures that seriously affects the safety of offshore operations. Therefore, the prediction of the relative motion and force between the multi-floating structures and the wave elevation around the multi-floating-system has become a hot issue. At present, the problem of double-floating-system is mostly based on linear potential flow theory. However, when the gap width between two floating bodies is small, the viscous and nonlinear effects are not negligible, so the potential flow theory has great limitations. Based on the viscous flow theory, using the finite difference solution program of FLOW3D and using volume of fluid technology to capture the free surface, a three-dimensional numerical wave basin is established, and the numerical results of the wave are compared with the theoretical solution. On this basis, the hydrodynamic model of side-by-side double-floating-system with a narrow gap is established, and the flow field in the narrow gap of the fixed double-floating-system under the regular wave is analyzed in detail. The law of the gap-resonance is studied, which provides valuable reference for the future research on the multi-floating-system.

A new model for nanowire growth by molecular beam epitaxy is proposed which extends the earlier approaches treating an isolated nanowire to the case of ensembles of nanowires. I consider an adsorbing substrate on which the arriving growth species (group III adatoms for III-V nanowires) may diffuse to the nanowire base and subsequently to the top without desorption. Analytical solution for the nanowire length evolution at a constant radius shows that the shadowing of the substrate surface is efficient and affects the growth kinetics from the very beginning of growth in dense enough ensembles of nanowires. The model fits quite well the kinetic data on different Au-catalyzed and self-catalyzed III-V nanowires. This approach should work equally well for vapor-liquid-solid and catalyst-free nanowires grown by molecular beam epitaxy and related deposition techniques on unpatterned or masked substrates. [ABSTRACT FROM AUTHOR]

CdS films have been synthesized using a thermal evaporation method equipped with Glancing Angle Deposition technique at zero and different oblique incident flux angles (α = 20°, 40, 50, 60, and 80°). The physical properties of the samples were systematically investigated by X-ray diffraction (XRD), field emission electron microscopy (FESEM), and Ultraviolet–visible spectroscopy analyzes. The XRD analysis revealed the hexagonal structure of the films deposited at α = 0–80°. The FESEM analysis confirmed the uniform formation of the nano columnar structure of CdS samples prepared at different values of α. Finally, high transmission of the sample produced at 80° deposition angle in the wavelength range of 500–1100 nm has been shown rather than those deposited at the other deposition angles, despite its high thickness (approximately 500 nm). [ABSTRACT FROM AUTHOR]

Throughout the wireless communication network planning process, efficient signal reception power estimation is of great significance for accurate 5 G network deployment. The wireless propagation model predicts the radio wave propagation characteristics within the target communication coverage area, making it possible to estimate cell coverage, inter-cell network interference, and communication rates, etc. In this paper, we develop a series of features by considering various factors in the signal transmission process, including the shadow coefficient, absorption coefficient in test area and base station area, distance attenuation coefficient, density, azimuth angle, relative height and ground feature index coefficient. Then we design a quantile regression neural network to predict reference signal receiving power (RSRP) by feeding the above features. The network structure is specially constructed to be generalized on various complex real environments. To prove the effectiveness of proposed features and deep learning model, extensive comparative ablation experiments are applied. Finally, we have achieved the precision rate (PR), recall rate (RR), and inadequate coverage recognition rate (PCRR) of 84.3%, 78.4%, and 81.2% on the public dataset, respectively. The comparison with a series of state-of-the-art machine learning methods illustrates the superiority of the proposed method. [ABSTRACT FROM AUTHOR]

In recent years, there has been increased research and rapid development in perovskite solar cells. Uniformity, repeatability, and reliability of electrode patterns formed by shadow‐mask technologies are factors that play an important role in efficient experimental studies for achieving high‐throughput samples and high‐performance devices. In this study, some new principles of mask design are investigated to overcome the drawbacks of conventional mask. High precision patterns are obtained by fabricating shadow‐masks with stainless steel plates via a photochemical etching process. An assembly concept design is proposed for shadow‐mask kits to improve versatility and avoid edge chamfer. The highly accurate active area and precise replication of the aperture patterns are obtained by improving the alignment between the samples and the mask patterns. The perovskite solar cell arrays are fabricated on a single substrate and a uniform performance is achieved due to the balanced distribution of electrodes. Thin shadow‐masks with smooth surfaces are employed to diminish the shadowing effect and a power conversion efficiency of 20.85% with a high fill factor of 81.6% is obtained in an inverted perovskite solar cell. The versatility and high quality of our shadow‐mask kits can further promote research in the area of thin‐film and photovoltaic technologies. [ABSTRACT FROM AUTHOR]

5 nm logic technology node is believed to be the first node that will adopt Extremely Ultra-Violet (EUV) lithography on a large scale. We have done a simulation study for typical 5 nm logic design rule patterns. In a 5 nm logic photo process, the most appropriate layers for the EUV lithography are the cut layers, metal layers, and via layers. Generally speaking, critical structures in a lithography process are semi-dense patterns, also known as the “forbidden pitch” patterns, the array edge structures, tip-to-tip structures, tip-to-line structures (under 2D design rules), the minimum area structures, the bi-lines, tri-lines, …, etc. Compared to that from the 193 nm immersion process, the behaviors for the above structures are different. For example, in the 193 nm immersion process, the minimum area is about 2~3 times that of minimum pixel squared, while in EUV photolithographic process, the minimum achievable area is found to be significantly larger. In the simulation, we have kept aware of the stochastics impact due to drastically reduced number of photons absorbed compared to the DUV process, the criteria used for various structures of image contrast are tightened. For example, in 193 nm immersion lithography, we have usually set the minimum Exposure Latitude (EL) for the poly layer, the metal layer, and tip-to-tip pattern, respectively, at 18%, 13%, and 10%. However, in EUV lithography, reasonable targets for the minima are, respectively, >18%, 18%, and 13%. We have also studied the aberration and shadowing impact to the above design rule structures. We will present the results of our work and our explanations.

In the pile group under lateral load, two types of interactions between soil and pile occur, namely the shadowing effect and the edge effect. When the piles in the pile group are subjected to the lateral loading, these two effects reduce the bearing capacity of the piles. In the present study, this pile group has been used to inhibit the integral bridge. In this study, the pile group under lateral load was tested in single-row and two-row arrangements. In the two-row arrangement of the piles, the distance of the piles increases compared to the single-row arrangement of the piles, but the effect of the interaction of the piles changes from the edge effect to the shadowing effect. According to the results of this study in the pile group under lateral load, if the distance between the piles is less than 3 D (D: pile dimension), the shadowing effect has a greater effect on the bearing capacity of the pile group compared to the edge effect. According to laboratory tests, the shear strain of the soil around the piles in single-row arrangement is less than in two-row arrangement. As a result, single-row arrangement has more load bearing capacity than two-row arrangement. [ABSTRACT FROM AUTHOR]

This work aims at inspecting the device operation and performance of a novel flipped npn microstructure solar cell based on low-cost heavily doped silicon wafers. The flipped structure was designed to eliminate the shadowing effect as applied in the conventional silicon-based interdigitated back-contact cell (IBC). Due to the disappearance of the shadowing impact, the optical performance and short-circuit current density of the structure have been improved. Accordingly, the cell power conversion efficiency (PCE) has been improved in comparison to the conventional npn solar cell microstructure. A detailed analysis of the flipped npn structure was carried out in which we performed TCAD simulations for the electrical and optical performance of the flipped cell. Additionally, a comparison between the presented flipped microstructure and the conventional npn solar cell was accomplished. The PCE of the conventional npn structure was found to be 14.5%, while it was about 15% for the flipped structure when using the same cell physical parameters. Furthermore, the surface recombination velocity and base bulk lifetime, which are the most important recombination parameters, were studied to investigate their influence on the flipped microstructure performance. An efficiency of up to 16% could be reached when some design parameters were properly fine-tuned. Moreover, the impact of the different physical models on the performance of the proposed cell was studied, and it was revealed that band gap narrowing effect was the most significant factor limiting the open-circuit voltage. All the simulations accomplished in this analysis were carried out using the SILVACO TCAD process and device simulators.

A new model for nanowire growth by molecular beam epitaxy is proposed which extends the earlier approaches treating an isolated nanowire to the case of ensembles of nanowires. I consider an adsorbing substrate on which the arriving growth species (group III adatoms for III-V nanowires) may diffuse to the nanowire base and subsequently to the top without desorption. Analytical solution for the nanowire length evolution at a constant radius shows that the shadowing of the substrate surface is efficient and affects the growth kinetics from the very beginning of growth in dense enough ensembles of nanowires. The model fits quite well the kinetic data on different Au-catalyzed and self-catalyzed III-V nanowires. This approach should work equally well for vapor-liquid-solid and catalyst-free nanowires grown by molecular beam epitaxy and related deposition techniques on unpatterned or masked substrates.

An ultrasonic anemometer is a sensor that measures wind velocity based on the principle of time-difference method. However, shadowing effect generated by its transducers is one of the main causes of its measurement error. Therefore, how to obtain the measurement error caused by the shadowing effect has become a problem to be solved. There is a lack of quantitative research on the shadowing effect at different environments. Numerical analysis method for ultrasonic anemometers has been becoming an economical and effective method. To further study the shadowing effect of ultrasonic anemometers, this paper simulates ultrasonic anemometers on the fluid dynamics software FLUENT under the conditions of different wind speeds and directions. Velocity nephograms, vorticity maps and wind speeds along the wind path are obtained and analyzed. Results show that the shadowing at different wind speeds and directions has different effects on the wind measurement accuracy of ultrasonic anemometers. To verify the accuracy of the numerical results, they are compared with those of wind tunnel experiments, which proved that the numerical analysis provides accurate and reliable prediction for the quantitative measurement of wind velocities. Therefore, the numerical method can provide a theoretical basis for reducing the measurement error of ultrasonic anemometers. [ABSTRACT FROM AUTHOR]

This paper describes a complete methodology for the computation of transient external heat fluxes (i.e. solar, albedo and earth) for a given set of orbital parameters such as altitude, solar constant etc. and orientation of the satellite. A software module based on this methodology was developed and its performance was assessed by comparing its predictions with the ones obtained by a commercial software on the same test problem. Comparisons revealed that the external fluxes can be computed accurately with the developed module. It was then used in conjunction with an in-house thermal analysis code based on Thermal Network Method (TNM) and Monte Carlo Ray Tracing Technique (MCRT) for the transient simulation of the same test problem. It was shown that the temperature predictions obtained by the in-house code and the commercial software were in excellent agreement with each other and the developed software is a reliable, accurate and complete tool that can be used in the thermal analysis of satellites.

This study proposes a new method to obtain the lateral response of pile groups by incorporating the pile group effect in layered soils. When a pile is loaded laterally, it creates a zone of influence in the direction of loading. In a pile group, each pile placed in the influence zone of prior piles is exposed to extra loads due to the load transfers from other piles. This mechanism results in a group effect which causes each pile in the group to have a different deflection curve compared to that of an identical isolated single pile under the same load. This study starts with a mathematical approach to model the interaction of two piles and then extends it to pile groups. The governing differential equation of a pile deflection problem is modified to take the pile-soil-pile interaction into account and solved analytically for each pile while the soil parameters and displacement fields around each pile are obtained numerically using the finite difference method written in Fortran language. The model captures the additional pile deflections induced by the group effects in pile groups and the results match well with the results of the existing methods, especially the finite element method. [ABSTRACT FROM AUTHOR]

• The deployment of LoRaWAN should be planned theoretically and assistant with measurements. • A channel model features propagation attenuation, shadowing effect, and multipath fading. • The theoretical model is used to develop an APP that can estimate the transmission distance of LoRa. • The feasibility of this APP is verified by practical measurements. • The results show that the model and APP are feasible. Most IoT technologies can make smart grids smarter, and LoRa is an emerging technology suitable for smart grids. The development of LoRa and the deployment of LoRaWAN, however are not mature. This study will investigate LoRa and support the deployment of LoRaWAN in smart grids. Trial and error is not sufficient for deployment of LoRaWAN, and it should be planned using theoretical approaches, assisted by measurements. Therefore, this work uses theoretical considerations to develop a channel model of LoRa that considers propagation attenuation, shadowing effect, and multipath fading. The theoretical model is used to develop an APP that can estimate the transmission distance of LoRa. To verify the feasibility of this APP, experiments use different parameters for the environment and transmission. Each experiment gives a packet error rate for transmission between two nodes. The packet error rate is obtained by measurement, and the distance between nodes is estimated theoretically. Results show that the model and the APP are feasible. This study also finds that the effect of a spreading factor is not as great as proposed by theory. Three factors affect the performance of LoRa, where distance is the main factor and obstacles and noise produce randomness. The contribution of this work is twofold. One is the theoretical channel model and the other is the practical APP. The engineers who are in charge of planning LoRaWAN can use the feasible APP to accelerate the progress of deployment. [ABSTRACT FROM AUTHOR]

• Measurement of the rod worth control banks causes large flux deformation in detectors located outside the core or in reactors of small size. • This work analyzes the feasibility of using the rod drop technique associated with corrections in the reactivity measurement to correctly estimate the rod worth measurement of the control bank. • Experiments and simulations were carried out to estimate the measure of this reactivity value and also to characterize this effect of the redistribution of the flux during the insertion of the control bank in the detector and the shadowing effect due to a partially inserted control bank. • Several effects due to flux redistribution were studied and discussed in this article. The main goal of this study is to quantify the neutron flux redistribution in detectors and the shadowing effect between control rods by proposing an instrumental calibration factor for measurement, based on computer simulations. The MCNP code was used to simulate the rod drop experiment in the IPEN/MB-01 research reactor. A study of the reactivity behavior was carried out during the most transient period of the rod drop experiment (t < 10 s), demonstrating great agreement between the simulation and the experiment carried out using the source jerk method. A methodology was developed to estimate the shadowing effect and the flux redistribution, and to propose a correction of the results obtained (calibration) in the simulations using the MCNP code and the rod drop experiment respectively. The maximum deviations between the reference value obtained from measuring the control banks via the stable period method and the simulated values were 0.5 % and 11.3 %, respectively. [ABSTRACT FROM AUTHOR]

The effects of existing tunnels on the evolution of soil arching require further investigation. In this study, trapdoor models with different distances between the trapdoor and tunnel are examined via discrete element method simulations after a numerical model is established based on experiments. The results show that as the distance between the tunnel and trapdoor (L) increases, the minimum soil arching ratio, ultimate soil arching ratio, and load recovery decrease, thus indicating that the shadowing effect of the tunnel becomes less distinctive. The essential distance affected by the tunnel is between 150 and 200 mm. The stress ratio in region L1 first decreases significantly and then gradually as the trapdoor displacement increases, reaching an ultimate value at L = 50 and 100 mm. The reverse trend is observed when L exceeds 150 mm, which is similarly observed in regions L2 and L3. The height of the equal-displacement region decreases steadily as L increases. Two distinct types of soil-arching structures are identified for interaction and independent arches. The displacement of the trapdoor increases the anisotropy of contact forces within the soil mass. The reorientation and destruction of the contact force fabric provide further insights into the formation of soil arching. [ABSTRACT FROM AUTHOR]

Massive multiple-input multiple-output (MIMO) is a potential candidate key technology for the 5G of wireless communication systems. In research to date, different power loss and shadowing effects on different antenna elements across the large arrays have been neglected. In this paper, based on an idealized propagation model, a new large scale attenuation (LSA) model is proposed, by which the large scale losses (path loss and shadowing effect) over the antenna array can be considered when establishing a massive MIMO channel model. By using this model, the spectral efficiency (in terms of bits/s/Hz sum-rate) of the maximum ratio combining (MRC) detector is derived for the uplink. The spectral efficiency performance of the zero forcing (ZF) detector also can be derived in the same manner. It can be found that the sum-rate performance (MRC and ZF) of our proposed channel model (assuming independent shadowing on all elements of the array) exceeds that of the conventional model (where the LSA effect is not included). Based upon our theoretical and simulation analysis, we have found that the spectral efficiency gap is mainly from the mean value of different shadowing effects across different elements, and the different path losses experienced by different antenna elements provide negligible contribution. This LSA model and the derived performance results could be beneficial and informative for the research, design and evaluation of the next generation of wireless communication system employing a massive MIMO configuration.

Formation of regular arrays of nanorods with high aspect ratio (length to transverse size) has been found in the process of Al thin film growth at oblique angle deposition on silicon substrate by the method of electron beam evaporation. It was found that the optimal conditions for nanostructuring are realized at the inclination angle larger than 80 degrees. [ABSTRACT FROM AUTHOR]

In this work, various silver-based thin films were prepared by sputtering method with inclined substrates in the presence of shadowing object. The morphology and structural and optical properties of the prepared thin films were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS), respectively. The wettability of films was investigated by measuring contact angles of the films. The obtained results show that by increasing shadowing effect, a decrease in contact angle of the prepared samples is observed. Bruggeman homogenization simulation method was applied to describe the film structures. The theoretical part and simulation using Bruggeman homogenization confirm the experimental findings and show the best possible agreements. Finally, an increase in contact angle of the prepared thin films with high porosity and high surface roughness was observed. In films with silver–silver oxide compositions, the higher contribution of oxide part in the structure of the films leads to the hydrophilicity of the surface. [ABSTRACT FROM AUTHOR]

The mechanism of local scour under two vibrating pipelines is investigated numerically in this research. A sediment scour model is adopted to estimate the motion of sediment. The general moving objects model, which is dynamically coupled with fluid flow, is set up to simulate the vortex-induced vibration (VIV) of the pipeline. The sediment scour model and pipeline vibration model are verified with the previous experimental results and show good agreement. Then, the coupling effects between the pipeline vibration and the local scour are investigated numerically. The effects of G/D (the ratio of the distance between the two pipelines to the diameter of the pipelines) on the local scour and the VIV of the pipeline are examined. The results indicate that the maximum scour depth under the vibrating pipelines is much larger than the scour depth under the fixed pipelines. Due to the shadowing effect of the upstream pipeline, the maximum scour depth under the upstream pipeline is deeper than that under the downstream pipeline. The pipeline vibration magnitude is closely related to the strength of the vortex that sheds behind the pipeline. The effect of G/D on the shape and strength of the vortices that shed behind the pipelines is significant. [ABSTRACT FROM AUTHOR]

Of all concentrating solar power technologies available today; the solar tower power plant is placed in the foreground and may become the preferred technology. In the present work, an algorithm, which gives us the cosine efficiency distribution of preliminary design of rotating heliostat field of solar tower power plant in the northern hemisphere, is presented. A regular radial staggered configuration is used. The variable radial distance between consecutives rows is computed considering the blocking factor constant for the entire solar field. A comparative performance analysis is developed between the existing PS 10 solar power plant in Spain, and the reconfigured one using the technology of rotating solar field concept. The study includes the cosine efficiency and the tower shadowing effect. The reconfigured model of PS10 is believed to be more promising than of the original one, in case it is adapted to suit the same technology. [ABSTRACT FROM AUTHOR]

With the development of vehicle networks, the information transmission between vehicles is becoming increasingly important. Many applications, particularly regarding security, are based on communication between vehicles. These applications have strict requirements for factors such as the quality of communication between vehicles and the time delay. Many theoretical communication protocols ignore the presence of buildings or other obstacles that are present during practical use, especially in urban areas. These obstacles can cause a signal to fade or even block direct communication. Many vehicles are often parked at the roadside. Because of their location, these parked vehicles can be used as relays to effectively reduce the shadowing effect caused by obstacles and even solve communication problems. In this paper, we study the problem of parked-vehicle-assistant relay routing communication in vehicle ad hoc networks. We propose an efficient parked vehicle assistant relay routing algorithm that is composed of four parts: a periodic Hello packet exchange mechanism, candidate relay list update, communication link quality evaluation, and candidate relay list selection. Simulation results reveal obvious advantages for indexes such as the quality of communication, success rate, and time delay. [ABSTRACT FROM AUTHOR]

Due to the complex and diverse nature of the propeller-ice contact problem, understanding the contact mechanism and evaluating the ice loads remains challenging. This study investigates the propeller-ice contact problem and explores the internal factors influencing the ice loads through model experiments at different advanced velocities, rotational speeds, and milling depths. The recorded ice load data is then used to predict the extreme loads that the propeller may encounter throughout its life cycle using the probabilistic method. The experimental results reveal that the shadowing effect and angle of attack are the primary reasons advanced velocity affects ice load, with the latter factor also being the internal cause of the load change caused by the rotational speed change. Moreover, the nonlinear increase of the ice load with the cutting depth increase is due to the chord length's change. The probability method analysis shows that the maximum thrust and torque the blade may encounter during its life cycle are approximately 50% and 35% higher than the maximum data recorded in the test. Additionally, this manuscript introduces the ice-making process and proposes a more straightforward calculation method for the shadowing coefficient. • Propeller-ice contact tests were performed at various scenarios. • A calculation method for shadowing coefficient was proposed. • Extreme ice load was evaluated using probabilistic method. [ABSTRACT FROM AUTHOR]

Device-free localization (DFL) plays an increasingly important role in many security and military applications. It can realize localization without the requirement of equipping targets with any devices for signal transmitting or receiving. To reduce the number of measurements in DFL, compressive sensing (CS) theory has been applied. By exploiting the sparse nature of location finding problem, the target location vector can be estimated from a few measurements. However, in changing environments, measurements may diverge from those in a fixed dictionary (sensing matrix), and the mismatches between the dictionary and runtime measurements can significantly deteriorate the localization performance of CS-based DFL methods. To address this, we propose a novel dictionary refinement-based DFL method. It adopts the saddle surface model to characterize the shadowing effects caused by targets and parameterizes the dictionary with the shadowing rate of each link as the underlying parameters. Then, the variational expectation-maximization algorithm is adopted to realize joint localization and dictionary refinement. Simulation results show that the proposed approach achieves higher accuracy and robustness compared with the state-of-the-art fixed dictionary DFL methods.

Abstract A molecular dynamics simulation has been carried out to investigate the effect of the incident angle in the oblique-angle deposition method on the atomic structure of the resulted hydrogenated amorphous silicon (a-Si:H) thin film. The atomic interaction in Si H system was calculated by Murty-Tersoff potential. The simulation results show that the a-Si:H thin film grew in a two-dimension mode at low or normal incidence (0°, 15° and 30°), however, it changed to follow a columnar or island-like mode at high incidence. As incident angles increased from 0° to 75°, the surface roughness increased, the adsorption rate decreased, and the a-Si:H thin film had more porous, lower density and higher content of the dangling bond. The analysis of atomic diffusion indicated that the incident angle played a crucial role in affecting the diffusion of atoms: the diffusion ability of high incidence was greater than that of low incidence. The growth mode, microstructure of a-Si:H thin film, and atomic diffusion ability were mainly influenced by shadowing effect. Highlights • The a-Si:H thin film grew in a two-dimension mode at low or normal incidence (0°, 15° and 30°). • The a-Si:H thin film grew in a columnar or island-like mode at high incidence. • The incident angle played a crucial role in affecting the diffusion of atoms. • The growth mode, microstructure of a-Si:H thin film, and atomic diffusion ability were mainly influenced by shadowing effect. [ABSTRACT FROM AUTHOR]

Device-free localization (DFL) is a technique that can locate targets wearing no devices, and has become an attractive technique for wide applications, such as intrusion detection and gesture recognition. In recent years, research on indoor localization using light sensor mainly focuses on traditional active localization methods, which require photodiodes being attached to targets. In this paper, we explore the visible light-based DFL method. In DFL, shadowed areas caused by different targets may overlap when multiple targets simultaneously exist in a small monitored area, which increases difficulties both in counting target and achieving accuracy localization. This paper presents an accurate geometrical multi-target device-free localization method, which includes a sector ring model and an adaptive multi-target positioning (AMTP) algorithm. The proposed model does well in describing the relationship between the target location and the shadowed area, which provides essential observation information for DFL. The proposed AMTP algorithm improves the accuracy of counting and locating multiple targets through updating weight map of the monitored area in each iteration. Numerous simulation results show that the proposed DFL method effectively achieves multi-target location, and outperforms the traditional geometrical localization method and the fingerprinting localization method both in counting and localization accuracy. [ABSTRACT FROM AUTHOR]

In this article, an accurate and fast approach is proposed to calculate the electromagnetic wave propagation characteristics over the sea surface under tropospheric ducting conditions. The method is based on the parabolic equation and an asymptotic model of a rough sea surface and is used to calculate the electromagnetic characteristics and to model the sea surface reflection. In the proposed model, termed the extremum approximation of the shadowing effect (EA of SE) model, the shadowing effect is considered and simplified to improve the accuracy and shorten the computation time. The probability density functions and the propagation factors of different models are compared, the influence of the rough sea surface and the shadowing effect on the electromagnetic wave propagation is analyzed and the model accuracy and efficiency are evaluated. Some comparisons are made with experimental data. The results show that the average error is about 1 dB less after the shadowing effect is considered; and the proposed approach shortens the computation time about 600 times while maintaining a high accuracy. [ABSTRACT FROM AUTHOR]

RF magnetron sputtering technique was employed to fabricate ZnS nanostructures with special emphasis given to study the effect of substrates (quartz, glass and quartz substrate pre-coated with Au, Ag, Cu and Pt) on the structure, surface evolution and optical properties. Type of substrate has a significant influence on the crystalline phase, film morphology, thickness and surface roughness. The present study elucidates the suitability of quartz substrate for the deposition of stable and highly crystalline ZnS films. We found that the role of metal layer on quartz substrate is substantial in the preparation of hierarchical ZnS structures and these structures are of great importance due to its high specific area and potential applications in various fields. A mechanism for morphological evolution of ZnS structures is also presented based on the roughness of substrates and primary nonlocal effects in sputtering. Furthermore, the findings suggest that a controlled growth of hierarchical ZnS structures may be achieved with an ordinary RF sputtering technique by changing the substrate type. [ABSTRACT FROM AUTHOR]

In magnetron sputtering, the ability to tailor film properties depends primarily on the control of the flux of particles impinging on the growing film. Among deposition mechanisms, the shadowing effect leads to the formation of a rough surface and a porous, columnar microstructure. Re-sputtered species may be re-deposited in the valleys of the films surface and thereby contribute to a reduction of roughness and to fill the underdense regions. Both effects are non-local and they directly compete to shape the final properties of the deposited films. Additional control of the bombarding flux can be obtained by ionizing the sputtered flux, because ions can be controlled with respect to their energy and impinging direction, such as in High-Power Impulse Magnetron Sputtering (HiPIMS). In this work, the relation between ionization of the sputtered species and thin film properties is investigated in order to identify the mechanisms which effectively influence the shadowing effect in Deep Oscillation Magnetron Sputtering (DOMS), a variant of HiPIMS. The properties of two Cr films deposited using the same averaged target power by d.c. magnetron sputtering and DOMS have been compared. Additionally, the angle distribution of the Cr species impinging on the substrate was simulated using Monte Carlo-based programs while the energy distribution of the energetic particles bombarding the substrate was evaluated by energy-resolved mass analysis. It was found that the acceleration of the thermalized chromium ions at the substrate sheath in DOMS significantly reduces the high angle component of their impinging angle distribution and, thus, efficiently reduces atomic shadowing. Therefore, a high degree of ionization in HiPIMS results in almost shadowing effect-free film deposition and allows us to deposit dense and compact films without the need of high energy particle bombardment during growth. [ABSTRACT FROM AUTHOR]

A Boundary Element Method (BEM) approach was developed for the analysis of pile groups. The proposed method includes: the non-linear behavior of the soil by a hyperbolic modulus reduction curve; the non-linear response of reinforced concrete pile sections, also taking into account the influence of tension stiffening; the influence of suction by increasing the stiffness of shallow portions of soil and modeled using the Modified Kovacs model; pile group shadowing effect, modeled using an approach similar to that proposed in the Strain Wedge Model for pile groups analyses. The proposed BEM method saves computational effort compared to more sophisticated codes such as VERSAT-P3D, PLAXIS 3D and FLAC-3D, and provides reliable results using input data from a standard site investigation. The reliability of this method was verified by comparing results from data from full scale and centrifuge tests on single piles and pile groups. A comparison is presented between measured and computed data on a laterally loaded fixed-head pile group composed by reinforced concrete bored piles. The results of the proposed method are shown to be in good agreement with those obtained in situ. [ABSTRACT FROM AUTHOR]

This paper describes a complete methodology for the computation of transient external heat fluxes (i.e. solar, albedo and earth) for a given set of orbital parameters such as altitude, solar constant etc. and orientation of the satellite. A software module based on this methodology was developed and its performance was assessed by comparing its predictions with the ones obtained by a commercial software on the same test problem. Comparisons revealed that the external fluxes can be computed accurately with the developed module. It was then used in conjunction with an in-house thermal analysis code based on Thermal Network Method (TNM) and Monte Carlo Ray Tracing Technique (MCRT) for the transient simulation of the same test problem. It was shown that the temperature predictions obtained by the in-house code and the commercial software were in excellent agreement with each other and the developed software is a reliable, accurate and complete tool that can be used in the thermal analysis of satellites. [ABSTRACT FROM AUTHOR]

Background Microbial food safety and spoilage due to human pathogens and decay-causing microorganisms are the major challenges for the production of fresh produce where contaminations often occur on the surface of the food. Fresh produce cannot be thermally treated as heating adversely affects the organoleptic characteristics and nutrients of the food, and thermally processed fresh produce may not be considered as “fresh” any more. Shortwave ultraviolet (UV-C) is a nonthermal technology that employs physical light energy to inactivate microorganisms on the surface of foods. Scope and approach This article reviewed the most recent development in the application of UV-C for surface decontamination of food with a focus on fresh produce. Considerations and challenges for commercialization of the technology are emphasized. Research on pulsed light (PL) is also discussed as the germicidal effect of PL is mainly due to the UV-C component of the light spectrum. Key findings and conclusions Many factors affect the efficacy of UV-C against foodborne pathogenic bacteria for food surface decontamination; these factors include UV-C dose, location of microorganisms on food, surface characteristics of foods, treatment temperature, species and serotype of microorganisms, state of bacteria, time from inoculation to UV-C treatment, and inoculation level. Combinations of UV-C/PL with other interventions can achieve synergistic and/or additive efficacy against human pathogens. For commercialization of the technology, accurate assessment of absorbed UV doses and means to overcome the shadowing effect are needed. Issues such as survival and growth of pathogens during post-UV-C storage, and possible formation of viable, but nonculturable bacteria require further investigations. [ABSTRACT FROM AUTHOR]