Propagation Prediction Method Research Articles

A space marching method for sonic boom near field predictions

The conventional sonic boom propagation prediction method widely adopted in supersonic aircraft design involves a two-step procedure. In the first step, a compressible viscous or inviscid Computational Fluid Dynamics analysis is applied to the aircraft geometry at flight conditions to produce a flow field solution near the aircraft. Then in the second step, a one dimensional nonlinear Burgers’ equation model is used to propagate sonic boom signature traces from the near field solution at flight altitude to the ground along a ray path. For an accurate ground signature prediction the near field signature must be accurately modeled at a sufficient distance from the aircraft flight path in order to minimize errors in the one dimensional propagation model. This is a very challenging task for general purpose CFD tools in a design environment because the cost of maintaining highly accurate off-body solutions increases dramatically as the radial distance is enlarged in the computational domain. It is also particularly difficult to apply these tools for wave propagation because the algorithms are normally lower order and numerically dissipative and dispersive. In this work a space marching procedure based on an optimized higher order finite difference method is developed and applied in conjunction with a CFD solution concentrated in the close vicinity of the aircraft. This new approach is much more efficient, compared to previous methods, in providing highly accurate near field signatures for full carpet ground predictions. Results indicate that near field signatures retain more waveform shape information farther from the aircraft geometry while reducing the CFD cost significantly. The predicted ground signature is also shown to converge in shape as the radial distance of the near field signature grows, which is indicative of a more ideal initial condition being supplied to the one dimensional wave propagation to ground. This feature is very difficult to replicate in a tractable manner with common CFD approaches used in design.

The evaluation of EMI characteristics of 4G-IMT system on FAST around its RQZ

Mobile communication base stations have become ubiquitous with the popularization and development of mobile communication services. Although the Chinese government has designated a radio quiet zone (RQZ) specifically for Five-hundred-meter Aperture Spherical radio Telescope (FAST), the 4G International Mobile Telecommunications (4G-IMT) system is still heavily used to meet the communication needs around the RQZ. To assess the Electromagnetic Interference (EMI) caused by 4G-IMT base stations on the performance of FAST, this paper employs the International Telecommunication Union (ITU) deterministic radio wave propagation prediction model. The interference of 4G-IMT base stations on FAST is evaluated based on relevant parameters, such as the frequency used by both FAST and the base station, in conjunction with the FAST threshold protection requirements. The results indicate that 47.73 % of the data exceed the radio astronomy protection threshold of FAST. In addition, a field experiment was conducted to verify the accuracy of the radio wave propagation prediction method used. The root-mean-square error between the predicted value and the measured value was found to be 6.94 dB, supporting the accuracy of the predicted results. The findings of this study can help suppress interference from mobile communication services around the RQZ of FAST and optimize the electromagnetic environment around FAST.

An Entropy Weight‐Based Method for Path Loss Predictions for Terrestrial Services in the VHF and UHF Bands

AbstractVHF and UHF are widely used frequency bands, and accurate path loss prediction in these bands is of great significance. In order to improve the prediction accuracy and stability of radio wave propagation, we propose a combined modeling method based on the entropy weight method. This method assigns appropriate weights to the predicted values of sub‐models using entropy, and calculates the final predicted value through weighted aggregation. To validate the feasibility of our proposed method, we conduct modeling using data from Denver, Colorado. We compare our method with the ITU‐R models and a model established using the coefficient of variation method. The results demonstrate that our proposed model outperforms the compared models. Specifically, the root‐mean‐square error (RMSE) of our proposed model is reduced by 5.94 and 5.51 dB compared to the ITU‐R P.1546 and 2001 models, respectively. Moreover, our proposed model exhibits better stability than the ITU‐R models. We also use the improvement percentage (γ) to evaluate the degree of improvement of our model over the sub‐models, which is 49.13% and 47.86% for the ITU‐R P.1546 and 2001 models, respectively. Additionally, by comparing the RMSE and absolute error, we find that the entropy weight‐based method outperforms the coefficient of variation‐based method. This research demonstrates the superiority of the entropy weight‐based modeling method, providing a valuable channel modeling approach for path loss prediction and supporting the regional assimilation of radio propagation prediction methods.

A Comprehensive Prediction Model for VHF Radio Wave Propagation by Integrating Entropy Weight Theory and Machine Learning Methods

In order to improve the prediction accuracy and robustness of radio wave propagation in the very high-frequency (VHF) band, we proposed a combination prediction model (hereinafter referred to as CPM) based on the entropy weight theory and the machine learning method. The improved entropy weight method is used to determine the initial weights of recommendation ITU-R P.1546 and ITU-R P.2001 in the combination prediction model based on the systematic analysis of the prediction performance of the two ITU-R models. Furtherly, we modeled the weight mapping using the machine learning method. The statistical comparison shows that the prediction accuracy and robustness of the proposed model are better than ITU-R P.1546 and P.2001 models, in which the root mean square error (RMSE) of path loss is reduced by 3.56dB and 7.35dB, respectively. In addition, the relative error (RE) of path loss is reduced by 0.0157 dB and 0.0255 dB, respectively, corresponding to a 40.53% and 52.62% reduction in the RE of path loss. The above research can provide basic support for the regional assimilation of radio propagation prediction methods.

Wave-based numerical investigation on diffraction correction for a low-height barrier in energy-based sound propagation model for road traffic noise

In energy-based noise propagation prediction methods, such as CNOSSOS-EU in Europe and ASJ RTN-Model in Japan, sound propagation is calculated by using the equation of sound attenuation by the geometrical divergence of the sound power from a sound source and adding various attenuation corrections such as diffraction effect and ground effect. In the ASJ RTN-Model, the insertion loss due to a semi-infinite barrier to a free field is generally used for the diffraction correction for a single barrier, the top of which is regarded as a knife wedge, whereas the diffraction correction for a low-height barrier is different from that for a general single barrier. It is given as the insertion loss due to a low-height barrier to a semi-infinite barrier, the top height of which is at the ground surface level, in a free field: the diffraction correction is zero when the low-height barrier is 0 m high. However, its range of application is not clear. In this paper, the diffraction correction for a low-height barrier is discussed by comparing the results of three-dimensional wave-based numerical analysis and propagation calculations using the ASJ RTN-Model.

Prediction of fatigue crack propagation based on dynamic Bayesian network

To address the problem of low prediction accuracy in the current research on fatigue crack propagation prediction, a prediction method of fatigue crack propagation based on a dynamic Bayesian network is proposed in this paper. The Paris Law of crack propagation and the extended finite element method (XFEM) are combined to establish the state equation of crack propagation. The uncertain factors of crack propagation are analyzed, and the prediction model of fatigue crack propagation based on the dynamic Bayesian network is constructed. A Bayesian inference algorithm based on the combination of Gaussian particle filter and firefly algorithm is proposed. The fatigue experiment of the specimen with the pre-cracks is carried out to test the correlation between the fatigue load cycles and the crack propagation depth. The experimental results show that the crack propagation prediction method proposed in this paper can effectively improve the prediction accuracy of crack propagation depth.

3D RT adaptive path sensing Method: RSSI modelling validation at 4.5 GHz, 28 GHz, and 38 GHz

This paper explains a new Adaptive Path Sensing Method (APSM) for indoor radio wave propagation prediction. Measurement campaigns, which cover indoor line-of-sight (LoS), non-line-of-sight (NLoS) and different room scenarios, are conducted at the new Wireless Communication Centre (WCC) block P15a) of Universiti Teknologi Malaysia (UTM), Johor, Malaysia. The proposed APSM is evaluated through a computerized modelling tool by comparing the Received Signal Strength Indicator (RSSI) with measurement data and the conventional Shooting-Bouncing Ray Tracing (SBRT) method. Simulations of the APSM and SBRT are performed with the same layout of the new WCC block P15a by using the exact building dimensions. The results demonstrate that the proposed method achieves a better agreement with measured data, compared to the conventional SBRT outputs. The reduced computational time and resources required are also important milestones to ray tracing technology. The proposed APSM method can assist engineers and researchers to reduce the time required in modelling and optimizing reliable radio propagation in an indoor environment.

Non-Linear Wear Propagation Property and Prediction Method Having Influencing Pitting Failure of Helical Gears

Non-Linear Wear Propagation Property and Prediction Method Having Influencing Pitting Failure of Helical Gears

AI-Empowered Propagation Prediction and Optimization for Reconfigurable Wireless Networks

Vehicular ad-hoc network (VANET) is one of the most important components to realizing intelligent connected vehicles, which is a high-commercial-value vertical application of the fifth-generation (5G) mobile communication system and beyond communications. VANET requires both ultrareliable low latency and high-data rate communications. In order to evolve towards the reconfigurable wireless networks (RWNs), the 5G mobile communication system is expected to adapt the key parameters of its radio nodes rapidly. However, the current propagation prediction approaches are difficult to balance accuracy and efficiency, which makes the current network unable to perform autonomous optimization agilely. In order to break through this bottleneck, an accurate and efficient propagation prediction and optimization method empowered by artificial intelligence (AI) is proposed in this paper. Initially, a path loss model based on a multilayer perception neural network is established at 2.6 GHz for three base stations in an urban environment. Not like empirical models using environment types or deterministic models employing three-dimensional environment models, this AI-empowered model explores the environment feature by introducing interference clutters. This critical innovation makes the proposed model so accurate as ray tracing but much more efficient. Then, this validated model is utilized to realize a coverage prediction for 20 base stations only within 1 minute. Afterward, key parameters of these base stations, such as transmission power, elevation, and azimuth angles of antennas, are optimized using simulated annealing. This whole methodology paves the way for evolving the current 5G network to RWNs.

Understanding design change propagation in complex engineering systems using a digital twin and design structure matrix

PurposeAs the engineering design process becomes increasingly complex, multidisciplinary teams need to work together, integrating diverse expertise across a range of disciplinary models. Where changes arise, these design teams often find it difficult to handle these design changes due to the complexity and interdependencies inherent in engineering systems. This paper aims to develop an innovative approach to clarifying system interdependencies and predicting the design change propagation at the asset level in complex engineering systems based on the digital-twin-driven design structure matrix (DSM).Design/methodology/approachThe paper first defines the digital-twin-driven DSM in terms of elements and interdependencies, where the authors have defined three types of interdependency, namely, geospatial, physical and logical, at the asset level. The digital twin model was then used to generate the large-scale DSMs of complex engineering systems. The cluster analysis was further conducted based on the improved Idicula–Gutierrez–Thebeau algorithm (IGTA-Plus) to decompose such DSMs into modules for the convenience and efficiency of predicting design change propagation. Finally, a design change propagation prediction method based on the digital-twin-driven DSM has been developed by integrating the change prediction method (CPM), a load-capacity model and fuzzy linguistics. A section of an infrastructure mega-project in London was selected as a case study to illustrate and validate the developed approach.FindingsThe digital-twin-driven DSM has been formally defined by the spatial algebra and Industry Foundation Classes (IFC) schema. Based on the definitions, an innovative approach has been further developed to (1) automatically generate a digital-twin-driven DSM through the use of IFC files, (2) to decompose these large-scale DSMs into modules through the use of IGTA-Plus and (3) predict the design change propagation by integrating a digital-twin-driven DSM, CPM, a load-capacity model and fuzzy linguistics. From the case study, the results showed that the developed approach can help designers to predict and manage design changes quantitatively and conveniently.Originality/valueThis research contributes to a new perspective of the DSM and digital twin for design change management and can be beneficial to assist designers in making reasonable decisions when changing the designs of complex engineering systems.

Prediction method of SSPE propagation based on improved terrain reconstruction

In view of the difficulty of wave propagation prediction and analysis in complex environment, a propagation prediction method of split-step parabolic equation (SSPE) based on terrain reconstruction is proposed. This method uses a two-way SSPE solution with a wide-angle propagation factor and variable step size, and uses the SSPE propagation prediction method based on improved terrain reconstruction to simulate and test the radio wave propagation characteristics of real terrain. Compared with the existing radio wave propagation prediction method, this method combines real terrain, which improves the terrain modeling effect by improving the reconstruction algorithm, and uses variable step size two-way SSPE solution to predict the propagation loss. Simulation test results show that the prediction method is within 6 dB. The accuracy meets the requirements of a high-precision radio wave propagation model, indicating that the method has practical significance and popularization value.

A New Method for Predicting Double-Crack Propagation Trajectories of Brittle Rock

Multi-crack propagation is investigated mainly by experimental measurement and little by theoretical prediction. The classical fracture criteria can better predict tensile fracture under arbitrary loading conditions (pure tensile, pure shear and mixed-mode), but have difficulty in predicting shear fracture. In this paper, Mode I and Mode II SIFs of branch-cracks initiated by the original cracks were calculated by the complex function and superposition method, and a new theory of multi-crack propagation was established based on the criterion of maximum tensile-shear SIF ratio. Theoretical results of two collinear cracks under uniaxial compression show that the cracks initiate more easily at [Formula: see text] (the crack inclination angle) than other angles. Coalescence of branch-crack only occurs at [Formula: see text] with the maximum crack propagation length. Peak stress [Formula: see text] reaches minimum when [Formula: see text] (inner friction angle of rock), and the larger the [Formula: see text], the closer to the compressive strength of rock the [Formula: see text]. Mechanism of the crack initiation and propagation are all Mode I under uniaxial compression. Uniaxial compressive test results of red sandstone (the rock material is assumed to be homogeneous) pre-cracked specimens agree well with predicted results of the crack initiation, stable and unstable propagation, which can prove the validity of the new multi-crack propagation prediction method.

Optimization of Multi-Frequency Network With DVB-T2 Services for Regions With Complex Geographies: A Case Study of Nepal

Planning for Multi-Frequency Network (MFN) with Digital Video Broadcasting-Second Generation Terrestrial (DVB-T2) services is particularly useful during the transition from analog to digital broadcasting. For efficient management of service area as well as resource allocation, it is necessary to administer the use of network parameters, e.g., transmit power, frequency channels, and antenna parameters. This article, therefore, proposes a coverage maximization scheme for the MFN with the DVB-T2 system by using the Genetic Algorithm. In order to effectively perform the optimization over regions with diverse geographical structures, a propagation prediction method considering the complex orography together with Digital Elevation Model is used to predict signal strength at each receiving location. Based on the received signal strength and standard Quality of Service criteria, the overall radio coverage of the network is maximized using the optimum values of transmit power levels, frequency channels, and antenna parameters. Although our analysis and simulations are based on the MFN network in Nepal, the methodology presented in this work can be applied in any region with some alterations in geographical and meteorological parameters.

Rapid prediction method for thermal runaway propagation in battery pack based on lumped thermal resistance network and electric circuit analogy

High-power lithium-ion batteries (LIBs) suffer from thermal runaway (TR) under unusual forces and misuse. Consequent TR propagation can cause battery pack breakdown and even dangerous fires or explosions. In this study, a four-step TR propagation prediction method is proposed for large-scale battery packs with series and parallel connection. To investigate the TR propagation behavior in battery packs, a lumped thermal resistance network was constructed based on the heat transfer characteristics of LIB packs. The energy balance equation for each cell and heat exchange between cells were solved via electrical circuit analogy. TR propagation features are discussed with different TR trigger locations, and the TR prevention effect of phase change materials (PCMs) is evaluated. The proposed prediction method exhibits high computational efficiency and adequate accuracy in resolving TR propagation. The prediction of battery core temperature and the experimental results are good in agreement. The TR propagation includes three stages: initial stage, rapid expanding stage and burst stage. The TR propagates preferentially along the thermal path with lower thermal resistance. When a PCM is applied to prevent TR, the critical behavior of TR propagation prevention is discovered. If the trigger cell of TR is prevented with the PCM, TR propagation in the entire pack can be avoided. The proposed method fulfils the fast prediction of TR propagation, which can provide insights into the on-board thermal safety design of electric vehicles.

Indoor 3-D RT Radio Wave Propagation Prediction Method: PL and RSSI Modeling Validation by Measurement at 4.5 GHz

This article introduces an efficient analysis of indoor 4.5 GHz radio wave propagation by using a proposed three-dimensional (3-D) ray-tracing (RT) modeling and measurement. The attractive facilities of this frequency band have significantly increased in indoor radio wave communication systems. Radio propagation predictions by simulation method based on a site-specific model, such as RT is widely used to categorize radio wave channels. Although practical measurement provides accurate results, it still needs a considerable amount of resources. Hence, a computerized simulation tool would be a good solution to categorize the wireless channels. The simulation has been performed with an in-house developed software tool. Here, the 3-D shooting bouncing ray tracing (SBRT) and the proposed 3-D ray tracing simulation have been performed separately on a specific layout where the measurement is done. Several comparisons have been performed on the results of the measurement: the proposed method, and the existing SBRT method simulation with respect to received signal strength indication (RSSI) and path loss (PL). The comparative results demonstrate that the RSSI and the PL of proposed RT have better agreements with measurement than with those from the conventional SBRT outputs.

The effect of railway platforms and platform canopies on sound propagation

The effect of railway platforms on sound propagation has thus far not been investigated in detail. Due to the vicinity to the track, the platform’s large reflecting horizontal surface, and the often present canopy it is unclear whether standard noise propagation prediction methods can be applied without modifications. Here, the acoustic effect of low railway platforms was investigated using measurements directly at the platform as well as in the distance in order to derive suitable models for the 2.5D boundary element method (BEM) as well as for standardized prediction methods. For the BEM using a source at the center of the track at the height of the platform edge was found to be an optimal solution. Different standard platform variations were investigated. The results show a relatively small, low lying, and localized shielding effect of the platform of up to 3 dB that further diminishes with increasing platform width. In comparison, a low noise barrier at the same position yields up to 4 dB and the effect is less localized. Although a canopy may lead to a better protection of elevated positions, the presence of such a structure also leads to a further decrease of the platform shielding in lower positions. Absorption on the lower side of the canopy can reduce this undesirable effect, however, only when large portions of the canopy are covered with absorbing material. Using the BE calculations and the measurements, two standardized calculation schemes, i.e. the Austrian ONR 305011 and the noise assessment methods defined in the European Directive 2015/996 (EU) were investigated. Both methods overestimate the platform effect. Similar to the BEM, a better agreement is reached when the source position is adjusted to the platform height. Floating elements such as a canopy are not defined in any of these standards, however, non-standard calculations of such objects as already implemented in certain noise mapping software could be used to take into account the attenuation effect for certain receiver positions.

Combined static-cyclic multi-axial crack propagation in cruciform specimens

Two cracks, initiated from the opposite tips of a 45° inclined central notch, were considered in cruciform specimens made of Ti6246. A static load was applied along one arm of the specimen and a cyclic load (R = −1) was applied along the other arm. Crack propagation was carefully monitored by optical means for different ratios of static to cyclic load. The observed crack propagation was simulated using two numerical tools, involving two different mixed-mode crack propagation prediction methods. The experimental evidence shows that there is a switch in crack propagation direction from orthogonal to the cyclic load at low static load levels to orthogonal to the static load for high static load levels. Both numerical procedures were able to predict this switch, albeit at slightly different static to cyclic load ratios.

Radio Propagation Prediction Method Using Point Cloud Data Based on Hybrid of Ray-Tracing and Effective Roughness Model in Urban Environments

Radio Propagation Prediction Method Using Point Cloud Data Based on Hybrid of Ray-Tracing and Effective Roughness Model in Urban Environments

Topic Propagation Prediction Based on Dynamic Probability Model

As social networks play an increasingly important role in people's lives, people are more likely to discuss hot topics on social networks. Predicting the spread of hot topics, known as topic propagation prediction is an important task. Due to the unpredictability of the users and topics in social networks, predicting the topic propagation trend is still a major challenge. Different users play different roles in topic propagation. However, existing studies have not utilized user role analysis. In this paper, we propose a topic propagation prediction method (TPP) based on user role analysis and dynamic probability model. First, we describe our user role analysis, which incorporates four user-factors to characterize user attributes along two dimensions. Second, we combine dynamic probability model with user role analysis to accurately predict the topic propagation trend. Finally, we prove the efficiency of TPP by experiments.

Analysis of ITU‐R VHF/UHF propagation prediction methods performance on irregular terrains covered by forest

In the scope of very high-frequency (VHF) and ultra high-frequency (UHF) terrestrial communication or broadcasting systems planning, the use of point-to-area propagation prediction methods is expected. The benchmarking of such models on different scenarios is very helpful to assist the system planner in choosing those most suited to the site in hands. In this sense, this study provides a comparative performance analysis of the International Telecommunication Union radio communication sector (ITU-R) recommendations P.526, P.1546, and P.1812 and a few other models on a site marked by the presence of irregular terrain covered by forest. A set of measurements at 563 MHz at different spots in Rio de Janeiro city with such features was taken as reference. The best prediction performance was achieved by the P.526 and P.1812 methods, in addition to a wedge diffraction model, with path loss mean errors between -5 and 3 dB, and standard deviations between 8.7 and 9.2 dB. Such results were observed when the presence of the forest layer was incorporated adding a representative clutter height.