Maximum Absolute Value Research Articles

Exploring the heterogeneities in vehicle-involved traffic violations at intersections using latent class clustering and partial proportional odds models

Vehicle-involved road crashes, mainly caused by traffic violations, result in major property damage and life losses annually. Thus, it is of vital importance to clarify the heterogeneities of various factors in traffic violation severities. This study quantifies the heterogeneities across different clusters. It selects 15 potential factors from six perspectives based on 40,161 police-reported traffic violations at intersections. An unsupervised learning algorithm combining latent class clustering analysis and partial proportional odds model, as well as marginal effects, is applied to clarify the differences. Four clusters are identified as the optimal based on the Akaike information criterion, Bayesian information criterion (BIC), sample-sized adjusted BIC, and entropy-based approach. The results evidenced that the top five influential factors in traffic violations at intersections were legs of entrance, driver age, road type, area type, and signal control. Their maximum absolute values of their marginal effects were more than 35%. Furthermore, there were great heterogeneities across the clusters, especially between cluster 2 and cluster 3. Findings could provide some insightful information to prioritize effective countermeasures to mitigate the losses of traffic violations and improve road safety.

High-Resolution Mapping of Soil Organic Matter at the Field Scale Using UAV Hyperspectral Images with a Small Calibration Dataset

The rapid acquisition of high-resolution spatial distribution of soil organic matter (SOM) at the field scale is essential for precision agriculture. The UAV imaging hyperspectral technology, with its high spatial resolution and timeliness, can fill the research gap between ground-based monitoring and remote sensing. This study aimed to test the feasibility of using UAV hyperspectral data (400–1000 nm) with a small-sized calibration sample set for mapping SOM at a 1 m resolution in typical low-relief black soil areas of Northeast China. The experiment was conducted in an approximately 20 ha field. For calibration, 20 samples were collected using a 100 × 100 m grid sampling strategy, while 20 samples were randomly collected for independent validation. UAV captured hyperspectral images with a spatial resolution of 0.05 × 0.05 m. The extracted spectra within every 1 × 1 m were then averaged to represent the spectra of that grid; this procedure was also performed across the whole field. Upon applying various spectral pretreatments, including absorbance conversion, multiple scattering correction, Savitzky–Golay smoothing filtering, and first-order differentiation, the absolute maximum values of the correlation coefficients of the spectra for SOM increased from 0.41 to 0.58. Importance analysis from the optimal random forest (RF) model showed that the characterized bands of SOM were located in the 450–600 and 750–900 nm regions. When the RF model was used, the UAV hyperspectra data (UAV-RF) were able to successfully predict SOM, with an R2 of 0.53 and RMSE of 1.48 g kg−1. The prediction accuracy was then compared with that obtained using ordinary kriging (OK) and the RF model based on proximal sensing (PS-RF) with the same number of calibration samples. However, the OK method failed to predict the SOM accuracy (RMSE = 2.17 g kg−1; R2 = 0.02) due to a low sampling density. The semi-covariance function was unable to describe the spatial variability of SOM effectively. When the sampling density was increased to 50 × 50 m, OK successfully predicted SOM, with RMSE = 1.37 g kg−1 and R2 = 0.59, and its results were comparable to those of UAV-RF. The prediction accuracy of PS-RF was generally consistent with that of UAV-RF, with RMSE values of 1.41 g kg−1 and 1.48 g kg−1 and R2 values of 0.57 and 0.53, respectively, which indicated that SOM prediction based on UAV-RF is feasible. Additionally, compared with the PS platforms, the UAV hyperspectral technology could simultaneously provide spectral information of tens or even hundreds of continuous bands and spatial information at the same time. This study provides a reference for further research and development of UAV hyperspectral techniques for fine-scale SOM mapping using a small number of samples.

Infrared and visible image fusion with entropy-based adaptive fusion module and mask-guided convolutional neural network

Since infrared and visible images have different descriptions of the same scene and have a lot of complementary information, they are usually fused to obtain a more comprehensive image. To overcome the detail information losing, fusion artifacts, and unnatural fusion in the traditional image fusion, we propose a novel algorithm for infrared and visible image fusion. Firstly, we introduce a guided filter to decompose the input image into a first-level base layer, a second-level base layer and a detail layer. Specifically, for the first-level base layer fusion, we propose an entropy-based image adaptive fusion module, which is guided by the image quality and the information entropy. To reduce the low-frequency information losing, we use the maximum absolute value rule to fuse the second-level base layer. In addition, for the detail layer containing many textures and edges, we construct a mask-guided deep convolutional neural network to fuse it. We label the infrared image pixel-by-pixel in the training set to obtain the foreground target mask, and construct the loss function jointly considering the mask, gradient, and the structural similarity of the image. Masks are only used when training the network. Finally, we reconstruct the image. Experiments show that our algorithm has achieved good performance in both subjective and objective evaluation.

Progressive compaction of soft cellular structures with layer-wisely designed gradient porosity

Soft cellular structures possess excellent recoverable compacting characteristics, which have great potentials for developing a new branch of flexible metamaterials with emerging applications. Inspired by the microstructures of natural materials, a novel type of soft cellular structures with gradient porosity, which are different from the periodic cellular structures, is proposed and designed in this study. In this new design of soft cellular structures, the overall porosity is kept as a constant while the porosity is varying along each layer gradually. In doing so, a new kind of soft cellular structures possess a layer-wisely designed gradient porosity is achieved. This design enables the cellular structures to exhibit a distinct progressive compaction behavior which is completely different from the uniform densification of the soft periodic structures. The progressive compaction of the structure is controllable through designing the gradient of the porosity to regulate stiffness of each layer. The mechanical responses and properties of the gradient soft cellular structures with different porosities and different layer-wise patterns under uniaxial compression are investigated both experimentally and numerically. This study reveals that the maximum absolute values of negative Poisson’s ratio of current gradient soft cellular structures is 2.113 time than that of periodic ones with a same overall porosity. The additional design freedom introduced by porosity gradient is beneficial for adjusting the mechanical properties of soft cellular metamaterials to meet the design demands of various potential applications.

Long-Term Changes of Positive Anomalies of Erythema-Effective UV Irradiance Associated with Low Ozone Events in Germany 1983–2019

In order to assess whether there is an increasing need for adaptation to the associated human health risks, the long-term occurrence (1983–2019) of low-ozone events (LOEs) with associated near-surface anomalies of erythema-effective UV irradiance was examined using an impact-related approach. Based on satellite data, means of four locations in Germany (Sylt, Berlin, Frankfurt, Munich) were compared for three subperiods (T1: 1983–1989, T2: 1990–1997, T3: 1998–2019). The period of peak global ozone depletion in the 1990s (T2) is characterized by a larger frequency of LOEs than the preceding (T1) and the subsequent (T3) subperiods. During the most recent subperiod (T3), the mean number of LOEs is 1.1 ± 0.5 events/year, with a variability of 0 to 4.2 ± 0.8 events/year, and shows a statistically significant decrease in the annual number of −4.8%/year. The annual totals of the LOE-associated anomalies of the erythema-effective UV radiation dose show no trend during T3. With regard to LOE-associated UV index anomalies, spring is the season most affected by LOEs, with more than half of all cumulative UV peak loads, while the absolute maximum values of the LOE-associated UV index anomaly of about 1.8 UV index occur near the summer solstice. Within the most recent subperiod (T3), summer contributes an increasing share of the peak loads. Overall, the study confirms that LOEs pose health risks due to intermittent, pronounced positive anomalies in erythema-effective UV irradiance and therefore require special attention and adaptation measures. Long-term changes can be identified, but to date there has been no evidence of an increasing health risk in Germany.

Radiative Effects and Costing Assessment of Arctic Sea Ice Albedo Changes

The rapid loss of Arctic Sea ice cover and thickness diminishes the surface albedo, which increases the ocean’s absorption of solar heat and exacerbates the Arctic amplification effect. According to the most recent research from the Intergovernmental Panel on Climate Change, the Sixth Assessment Report (IPCC, AR6), the extent of summer sea ice is anticipated to decrease below 1 million km2 by the 2050s as a result of the extreme climate. Nevertheless, past and future changes in sea ice albedo radiative forcing and the resulting economic cost remain to be explored in systematic and multi-disciplinary manners. In this study, we first analyze the evolution of Arctic sea ice radiative forcing (SIRF) from 1982 to 2100 using a radiative kernel method based on albedo data from the Polar Pathfinder-Extent (APP-x) and Coupled Model Intercomparison Project 5 (CMIP5). Then, the SIRF is converted to CO2 equivalent emissions via the Dynamic Integrated Model of Climate and Economy (DICE) model. Finally, the associated costs are calculated using the substitute cost method, based on the social cost of carbon to achieve the Paris Agreement targets. The results show that the average Arctic SIRF was −0.75 ± 0.1 W·m−2 between 1982 and 2020, and increased by 0.12 W·m−2 during this period. The SIRF in April–June accounts for nearly 77% of the average annual value, with a maximum absolute value of –3.2 W·m−2 in May. Through model transformation, it is shown that the Arctic SIRF rising leads to global warming comparable to the effect of an increase of 34.5 Gt of CO2 in the atmosphere relative to pre-industrialization, and results in a loss of 24.4–48.8 trillion USD for climate regulation service (CRS). From 2020 to 2100, in the representative concentration pathway (RCP) 8.5, the Arctic SIRF is projected to increase by 0.31 W·m−2. Combined with the discount rate, the estimated average annual cost over the period ranges from 6.7–13.3 trillion USD. These findings provide a systematic understanding of the radiative effect of Arctic sea ice change on the global climate and the corresponding economic cost.

Evolution of the velocity gradient invariants in homogeneous isotropic turbulence with an inverse energy cascade

An investigation of topological features of homogeneous isotropic turbulence with an inverse energy cascade is performed by using a direct numerical simulation. The inverse energy cascade is induced by reversing the velocity field (i.e., under the transformation from ui to −ui) of a freely decaying isotropic turbulence. In the backward energy transfer process, the joint probability density function (PDF) of Q and R exhibits a novel shape, which seems to be symmetric with the well-known teardrop shape about the Q-axis (Q and R are the second and third invariants of the velocity gradients tensor, respectively). The predominance of the top-right (R > 0 and Q > 0) and the bottom-left (R < 0 and Q < 0) quadrants is observed in the backward energy transfer process. This observation is different from that of the forward energy cascade, in which the top-left (R < 0 and Q > 0) and the bottom-right (R > 0 and Q < 0) quadrants are dominant. The unexpected shape of the joint PDF of Q and R indicates that the turbulence with an inverse energy cascade is dominated by vortex compression and tube-like structures. The PDF of the intermediate eigenvalue of the strain-rate tensor in the inverse energy cascade is negatively skewed, which is opposite to the universal feature of the forward energy cascade. Nevertheless, the preferential alignment of vorticity with the intermediate eigenvector is rather robust, no matter whether the direction of the energy transfer is forward or backward. In addition, it is universal that the vorticity is mostly perpendicular to the eigenvector, which corresponds to a strain-rate eigenvalue with the maximum absolute value among the three eigenvalues. Since the velocity gradient invariants are closely related to the local flow topology, the numerical results reported in this work are expected to shed light on the intrinsic dynamics and mechanisms of inverse energy cascade.

Fabrication of gelatin-EGCG-pectin ternary complex stabilized W/O/W double emulsions by ultrasonic emulsification: Physicochemical stability, rheological properties and structure

Double emulsions have very promising application prospects in the pharmaceutical, cosmetic, and food industries. Nevertheless, its usage in the food industry is restricted mainly due to its immense stability problems. Here, W 1 /O/W 2 double emulsion was prepared by two-step emulsification method using ultrasonic emulsification technology. The physicochemical stability, rheological properties, thermal stability, and microstructure of the double emulsion were investigated. The results revealed that W 1 /O/W 2 double emulsion with optimum stability was prepared on the parameters that the ratio of W 1 (gelatin)/O primary emulsion to the external aqueous phase (gelatin-EGCG-high methoxyl pectin ternary complex) was 6:4, ultrasonic power was 80 W, ultrasonic time was 6 min, and ternary complex concentration was 0.75%. The double emulsion produced under these conditions had the smallest particle size (1143 nm) and the maximum absolute zeta potential value (39.17 ± 0.50 mV). The results of full-featured stability analyzer manifested that the emulsion system no longer underwent phase separation. Confocal laser scanning microscopy (CLSM) successfully observed a uniformly dispersed double emulsion. Furthermore, dynamic rheological properties demonstrated that the cohesive strength of W 1 /O/W 2 double emulsion was strength than that of W 1 /O primary emulsion. Differential scanning calorimetry (DSC) analysis suggested that both remained stable throughout the temperature change, while the W 1 /O/W 2 double emulsion was more thermally stable. Hence, the gelatin-EGCG-high methoxyl pectin ternary complex can act as an effective emulsion stabilizer to stabilize the W 1 /O/W 2 double emulsion. • W/O/W double emulsions were prepared by ultrasonic emulsification method. • Ultrasonic treatment improves the physical stability of the emulsion. • The optimally stable double emulsion system no longer exhibits phase separation. • Ternary complex can be used as emulsion stabilizer to stabilize double emulsion. • Cohesive strength of the double emulsion is enhanced after ultra-sonication.

3D Hand Scanning Methodology for Determining Protective Glove Dimensional Allowances.

There are two types of dimensional allowance (inner and external) related to two distinct areas of occupational health and safety: those being a measure of fit of personal protective equipment (PPE) and those determining the safe and comfortable human interaction with tools and machines, e.g., the latter ones result from wearing PPE increasing the dimensions of the human body and generating limitations in the work environment. In this paper, they are taken to mean the difference between the dimensions of a bare and gloved hand (including glove construction and materials). Dimensional allowances are important in designing the work environment, e.g., machine control panels and tools. The absolute and relative maximum values of dimensional allowances determined in this study for a hand in a firefighter's protective glove for the main anthropometric data are: 16.90 mm (5.90%) for length, 12.00 mm (13.77%) for width, and 15.70 mm (7.96%) for circumference. The obtained results are useful for designers, and especially for designing keys on control panels and LCD touch displays and monitors integrated with machines.

Pseudo-spectral optimization and model predictive control of vehicle shift process with dual clutch transmission

To improve the shift quality of dual clutch transmission (DCT) vehicles and reduce the jerk and sliding friction in the shift process, a real-time planning of clutch optimal engagement trajectory and control method in the shift process is proposed. This method combines pseudo-spectral optimization, machine learning, and model predictive control. First, considering the jerk, sliding friction work, and shift time as the optimization indices, the adaptive pseudo-spectral method is employed to optimize the engagement trajectory of the clutch during the shift process. Based on the optimal trajectory data set, a gradient boosting decision tree-based real-time planning method for the clutch target engagement trajectory is proposed. Second, a model predictive control strategy for the shift process is proposed based on the DCT system model to track the optimal target trajectory in real-time. Simulations and experiments reveal that the proposed target engagement trajectory planning method can plan the clutch target engagement trajectory for various accelerator pedal openings and initial clutch speed states in real-time, and the proposed model predictive control method can accurately track the target trajectory. Compared with the original vehicle strategy, under 35% and 65% accelerator pedal opening, the maximum absolute value of jerk produced by the proposed strategy was reduced by 31.06% and 31.46%, respectively, and the sliding friction work was reduced by 22.87% and 23.24%, respectively. The shift times of the proposed strategy under 35% and 65% accelerator pedal openings were 19.12% and 20.69% lower than that of the original vehicle strategy, respectively.

Analysis of magneto-natural-convection flow in a semi-annulus enclosure filled with a micropolar-nanofluid; a computational framework using CVFEM and FVM

Micropolar fluids are the media in which their behavior is affected by the microrotation of the substructure particles. In the present work, the natural-convection flow of a micropolar-nanofluid (Al2O3/water) in the presence of an inclined magnetic field in a semi-annulus enclosure is investigated. The influence of active parameters on magneto-natural convection is investigated. The governing equations (mass, momentum, microrotation, and energy) are numerically solved by CVFEM. Moreover, for some conservative comparisons, the equations are solved by Ansys Fluent CFD code which is conjugated by an innovative nondimensionlization scheme. The effects of important parameters are investigated on the streamlines, isotherms, microrotation contours, the maximum absolute value of stream function (Ψmax), the average Nusselt number (Nuave) and the maximum absolute value of microrotation Nmax∗. The results discovered that the values of Nuave descend with ascending the Hartmann number (Ha) and material parameter (K) while it ascends with ascending Rayleigh number (Ra) and particle volume fraction (ϕ). The value of Nuave descends 10.8% while Nmax∗ increases 19.8% when K increases from 1 to 2. The value of Nuave descends 44.83% when Ha increases from 25 to 75 at λ=45°. The minimum value of Nuave occurs at λ=45° for Ha=25 and at λ=30° for Ha=50 and Ha=75.

The effect of environmental temperature on influence line of concrete beam type bridge

The influence line (IL) contains information induced by a unit force applied at any cross-section of the bridge, and its change can be used for damage identification. However, environmental temperature will also change the bridge IL, thus affect the damage identification effectiveness. In this paper, the main factors affecting the deflection and strain ILs of the concrete beam type bridges are systematically studied considering that temperature affects the structural static characteristics by changing the elastic modulus of concrete material, structural geometry, boundary condition and axial force. Then, based on the analytical formulas of the deflection and strain ILs of the concrete beam type bridge, the iterative calculation formulas describing the relationship between the ILs and the temperature are derived. Finally, the iterative calculation formulas are verified by numerical examples of beams with equal and variable cross-sections, and experiment in Environmental Coupling Test Chamber. The deflection and strain ILs are identified by parking a vehicle at different locations on the bridge progressively in the experiment. The results indicate that the maximum absolute values of the relative change rate (RCR) of the Ils are even up to10%, and the effect of environmental temperature on the IL concrete beam type bridge cannot be ignored. The proposed iterative calculation formulas can effectively consider the effect of environmental temperature, and reduce the maximum absolute values of the RCR of the Ils to be less than 1%. Thus it can be used to calculate the IL of concrete beam type bridges under actual temperature.

Infrared-visible image fusion method based on sparse and prior joint saliency detection and LatLRR-FPDE

In this paper, a new infrared and visible image fusion method based on saliency detection and LatLRR-FPDE is proposed to ensure the saliency of the fused target and improve the clarity of the texture detail information of the latent low-rank representation (LatLRR) fusion method. In the feature representation stage, source images are decomposed into low-rank and sparse parts based on LatLRR. Then Fourth order Partial Differential Equation (FPDE) is used to extract high-frequency detail information from the low-rank part. In the fusion decision stage, according to the characteristic difference of the decomposed sub-bands, a multi-scale fusion scheme is carried out using rules such as EM (expectation-maximization), average (AVG), and the maximum absolute value. To guarantee the integrity of thermal radiation features in the target area in fusion results, an infrared image saliency detection algorithm is proposed, which utilizes the fusion information obtained from the sparse and prior saliency feature. Specifically, the algorithm uses convex hull center prior and contrast prior to obtain the background-suppressed saliency map. Meanwhile, to make full use of the high-dimensional saliency features in the image decomposition stage, the prior saliency map and the sparse saliency map are fused to improve the accuracy of saliency detection without the demand to extract redundant feature, which largely increases time-efficiency of the model. Finally, infrared feature compensation is performed on the target region of the fused image based on the saliency mapping strategy to make the final fused image having a better infrared target feature representation. The experiments are based on registered public datasets and compared with various popular image fusion algorithms. The subjective and objective results show that the proposed algorithm can effectively keep the integrity of salient infrared features and has superior visual quality.

Precise detection and localization of R-peaks from ECG signals.

Heart rate variability (HRV) is derived from the R-R interval, which depends on the precise localization of R-peaks within an electrocardiogram (ECG) signal. However, current algorithm assessment methods prioritize the R-peak detection's sensitivity rather than the precision of pinpointing the exact R-peak positions. As a result, it is of great value to develop an R-peak detection algorithm with high-precision R-peak localization. This paper introduces a novel R-peak localization algorithm that involves modifications to the well-established Pan-Tompkins (PT) algorithm. The algorithm was implemented as follows. First, the raw ECG signal $ X\left(i\right) $ was band-pass filtered (5-35 Hz) to obtain a preprocessed signal $ Y\left(i\right) $. Second, $ Y\left(i\right) $ was squared to enhance the QRS complex, followed by a 5 Hz low-pass filter to obtain the QRS envelope, which was transformed into a window signal $ W\left(i\right) $ by dynamic threshold with a minimum width of 200 ms to mark the QRS complex. Third, $ Y\left(i\right) $ was used to generate QRS template $ T\left(n\right) $ automatically, and then the R-peak was identified by a template matching process to find the maximum absolute value of all cross-correlation values between $ T\left(n\right) $ and $ Y\left(i\right) $. The proposed algorithm achieved a sensitivity (SE) of 99.78%, a positive prediction value (PPV) of 99.78% and data error rate (DER) of 0.44% in R-peak localization for the MIT-BIH Arrhythmia database. The annotated-detected error (ADE), which represents the error between the annotated R-peak location and the detected R-peak location, was 8.35 ms for the MIT-BIH Arrhythmia database. These results outperformed the results obtained using the classical Pan-Tompkins algorithm which yielded an SE of 98.87%, a PPV of 99.14%, a DER of 1.98% and an ADE of 21.65 ms for the MIT-BIH Arrhythmia database. It can be concluded that the algorithm can precisely detect the location of R-peaks and may have the potential to enhance clinical applications of HRV analysis.

Atmospheric Delay Correction Utilization Method for Out-of-Network PPP-RTK Users

Traditional PPP-RTK algorithm research has focused on users in a reference station network. However, if a proper PPP-RTK user algorithm can be designed for out-of-network users to achieve accurate and rapid positioning, the effective service area of existing reference station networks can be markedly expanded. To address the problem of extrapolating atmospheric corrections for out-of-network users, this study presents a single-reference-station (SRS) PPP-RTK model to address atmospheric delay corrections, by ensuring that only corrections from the closest reference station are used. Several numerical experiments were designed and conducted to compare the performance of the presented model and a widely used interpolation model. The extrapolation error distribution, mean and the maximum of absolute values of errors, and standard deviation of errors were selected as indicators. The results show that the SRS PPP-RTK model is significantly more accurate than the interpolation model. Thus, for out-of-network users, we suggest that the presented SRS PPP-RTK model should be used, and the residual atmospheric delays are needed to be estimated.

Seismic Performance of Superelastic SMA Damper Retrofitted Building

Nonlinear dampers are well known retrofitting system for the building structure, to mitigate seismic hazard. In past, among different type of nonlinear dampers, metallic yield dampers gain significant attention due to its high energy dissipation capacity. However, it has been observed while yield damper reduces floor displacement, but increases floor acceleration and leaves large residual displacement at the end of ground motion. Present study focuses on the application of shape memory alloy (SMA) dampers as an alternative to the yield damper, for retrofitting of building structure under seismic loading. Thus, response analyses are performed for nonlinear building structure without and with yield damper or SMA damper, under a large number of ground motion. Vibration control efficiency of yield and SMA damper are estimated in terms of the absolute maximum values of the floor acceleration, interstory drift ratio, and residual displacement. Response parameters are estimated over wide range of parameters of damper, building structure, and ground motion. Parametric study results revealed that yield damper provides very less acceleration control efficiency and some of cases it become more than uncontrolled structure. In contrast SMA damper slightly improves the acceleration control than yield damper (almost 14 %). In Comparison to the yield damper, SMA damper reduces the interstory drift ratio by 38 % and residual floor displacement by 47 %. Therefore, SMA damper provides major advantage in floor displacement reduction over yield damper, and acts as better re-centring device for seismic retrofitting application.

The internal flow behaviors during Taylor cone formation of pulsating electrohydrodynamic jet printing

The toroidal vortex inside the Taylor cone is one of the most interesting features in electrohydrodynamic (EHD) jet printing. However, due to the considerable difficulty in capturing the microscopic internal fluid flow from the experiment, many aspects of the printing process are still not fully understood. Here, we present a numerical study on the Taylor cone formation process of pulsating EHD jet printing under the variations of several key operational parameters and liquid properties, namely, electric voltage, nozzle height, liquid surface tension coefficient, and liquid dynamic viscosity. In addition to the electrohydrodynamic motion of the liquid–gas interface, we focus our attention to the time evolution of the liquid flow and vortex inside the Taylor cone. The intensity of the vortex is evaluated by analyzing the absolute value of the swirling strength throughout the formation process. By virtue of examining the electric field distribution, interface charge density, velocity field, and the absolute value of the swirling strength from the numerical data, we elucidate the influences of the aforementioned parameters on Taylor cone formation and internal flow behaviors. Eventually, a scaling law of λ2max∝Boe/Ca2 between the maximum absolute value of the swirling strength and the dimensionless variables electric bond number Boe and capillary number Ca is proposed, which applies to all the parameters investigated in this work.

Improved Locating Method for Local Defects in XLPE Cable Based on Broadband Impedance Spectrum

The crosslinked polyethylene (XLPE) cable safety is affected by environmental factors and artificial defects during operation. This work proposes an improved locating method based on broadband impedance spectrum (BIS) to locate local defects in XLPE cables. The calculation process of the algorithm has been analyzed. The selection of the incident Gaussian signal and the peak recognition method have been discussed, where the pulse width of the Gaussian signal was found to be determined primarily by the upper limit frequency of the traveling wave transmitting in the cable. The centroid and function fitting methods were established to reduce the peak recognition error caused by the test sampling rate. This work verified the accuracy of the algorithm through experiments. A vector network analyzer (VNA) was used to test the BIS of the cable. A 20 m-long cable containing abrasion and an inserted nail with different depths was measured in the BIS test. It was found that the abrasion and the nail could be located. The locating deviation of abrasion was within ±1%, and the centroid and function fitting methods could effectively reduce the locating deviation. The locating deviation was within ±1% when the depth of the nail inserted into the cable accounted for less than 50% of the insulation thickness. When the depth exceeded 75% of the insulation thickness, the deviation of each method was more significant, and the maximum absolute value of the deviation was 4%.

Research on Leakage Mechanism of Underwater Shield Tunnels with Different Soil Layers during Operation Period

Different soil layer properties have great influence on tunnel leakage. In this paper, the finite element software is used to analyze the homogeneous leakage model of different soil layers and different degrees of lining deterioration. The working conditions of different soil layer properties and different degrees of lining deterioration are established by means of soil layer permeability coefficient and lining permeability coefficient, and the law of tunnel leakage under each working condition is analyzed. This paper innovatively explores the relationship between the severity of tunnel seepage caused by different lining deterioration and the soil layer properties of the tunnel. Finally, by comparing the field survey data of Dinghuaimen with the leakage law and mechanism summarized by the model, the reliability and feasibility of the model method to explore the leakage mechanism are verified. The model test results are consistent with the project survey data. In this paper, the seepage law and mechanism of underwater shield tunnel are explored and the result shows: (1) The leakage laws and stress distribution laws of a single homogeneous soil layer with different strata properties are similar. The flow velocity in the lower half of the tunnel lining is greater than the upper half, and the maximum velocity occurs at the arch foot; the velocity inside the lining is much smaller than that inside the soil layer. The maximum absolute value of the axial stress of the lining occurs at the arch waist on the left and right sides, and the minimum values of the axial stress of absolute values all occur at the dome. (2) The leakage of underwater tunnels is related to the properties of soil layers. The larger the soil permeability coefficient is, the more serious the deterioration of the tunnel lining will be, and the more serious the tunnel leakage will be. (3) The leakage of complex strata follows the law of leakage in a single homogeneous stratum. The leakage of the tunnel is the most serious in the fine sand layer with the largest permeability coefficient. Moreover, when the seepage phenomenon occurs, the water flow tends to seep along the fine sand layer to the tunnel.

Self-steepening and intrapulse Raman scattering in the presence of nonlinear gain and its saturation

In this paper we present the results of a detailed numerical investigation of the influence of the self-steepening effect on the parameters of the Raman dissipative solitons in the presence of nonlinear gain and its saturation. It has been established that when the effect of self-steepening prevails under the intrapulse Raman scattering it leads to nonlinear changes in the parameters of the Raman dissipative solitons. Comparing the impact of the intrapulse Raman scattering and self-steepening in the presence of nonlinear gain and its saturation on the dissipative solitons, the following differences have been identified: a much slighter change of the amplitude in the presence of self-steepening; different types of nonlinear dependencies of the frequency and velocity in the presence of intrapulse Raman scattering; and a substantial increase of the velocity under the influence of self-steepening. We have found that under the influence of the saturation of the nonlinear gain the observed nonlinear changes of the parameters of Raman dissipative solitons in the presence of the self-steepening effect are weaker. There has been observed a reduction of the maximum values of the amplitude and velocity as well as the maximum absolute values of the frequency of the Raman dissipative solitons.