Search

Concrete piles are a common obstacle in an antilanding obstacle field. To research the damage ability of concrete piles with different shaped charges, penetration tests of concrete piles with different standoff distances (SODs) were carried out with explosively formed projectiles (EFPs) and jetting projectile charges (JPCs). The pressure was measured at different positions inside the concrete piles during the penetration process, and the failure mechanism and damage characteristics of the concrete piles were analyzed. The penetration velocity of the JPC was measured by placing reticular targets inside the concrete pile. The results show that the damage ability of JPCs to concrete piles is stronger than that of EFPs. When the SOD is in the range of 20∼50 cm, an EFP causes slight damage to a concrete pile. With the increase in SOD, the penetration capacity of JPCs increases, but the damage ability of JPCs decreases. When the SOD is 15 cm, a JPC causes severe damage to a concrete pile, and when the SOD is in the range of 20∼40 cm, a JPC causes moderate damage. When attacking targets with obvious side boundary effects, such as concrete piles, the SOD that results in the strongest damage is not the SOD that results in the strongest penetration ability.

The product bears the shock load during the circulation process. The cushioning materials need to absorb the energy generated during the shock to prevent damage to the product. The cushion packaging system generally consists of products, cushioning materials, and an outside packaging carton. Therefore, it is necessary to study the factors affecting the cushion performance of the system. This paper adopts a BP neural network to develop a more precise constitutive relationship. Based on the trained constitutive network model, the dynamic equation of the system is established, and the Runge-Kutta algorithm is utilized to resolve it. The multi-objective optimization (MOP) model of the series cushioning system is established for the first time. The model considers more factors, such as the stability of the cushioning material and whether to use local cushioning. The factors affecting the performance of the cushioning system are deeply studied, and a variety of evolutionary algorithms (PESA2, SPEA2, MOPSO, MOEA/D, and NSGA-II) are utilized to solve the multi-objective optimization problem. The performances of the solution sets obtained by the evolutionary algorithms are studied based on several performance indicators. The results show that these solution sets have good convergence, and the all-around performance of NSGA-II ranks first. Finally, comparing the knee point of the non-dominated solution set calculated by NSGA-II with the parameters in the literature, it is found that the former has better defense performance and less material consumption, which can be used for future product design. Therefore, the evolutionary algorithm can favorably resolve the multi-objective optimization of the series cushioning packaging system under the dropping shock.

Transportation agencies build statistical models and predict the average crash frequency to identify hazardous road sections and make informed decisions to reduce crashes. In this paper, safety performance models (SPFs) were built and evaluated considering various pavement and roadway characteristics, including pavement friction, which is seldom available for analysis. Four count data models--Poisson model, negative binomial (NB) model, hurdle-NB model (HNB), and zero-inflated NB (ZINB) model--were built based on roadway characteristics and crash data provided by the Oklahoma Department of Transportation (ODOT). Pavement friction, roadway geometry, surface condition characteristics, and traffic exposure were considered the contributing factors to traffic crashes. Established models were compared in terms of the goodness-of-fit, zero inflation, and statistical significance of factors. The HNB model exhibited promising fitting performance with a manageable number of influencing variables. Coefficients in the HNB model suggest that adequate pavement friction and the presence of shoulders can significantly reduce the crash frequency and thus improve roadway safety performance. Potential issues of the statistical models, such as unobserved heterogeneity and multicollinearity, were also discussed. The relation between roadway infrastructure characteristics (including pavement friction) and roadway safety revealed in this study could assist in choosing the proper statistical model for better decision-making and selecting appropriate preventive treatments for improved roadway safety., Author(s): Joshua Q. Li (corresponding author) [1]; Wenyao Liu [1]; Xue Yang [1]; Pan Lu [2]; Kelvin C. P. Wang [1] 1. Introduction Transportation systems play crucial roles in providing [...]

A novel low-profile all-textile microstrip antenna for ultra-wideband (UWB) applications in wireless body area networks (WBANs) is presented. The antenna incorporates flexible materials such as felt and conductive fabrics which provide optimal wearing comfort and durability. The use of a single dielectric substrate layer facilitates the integration process. The antenna also features a full background plane that minimizes the back radiation towards the human body. Multiple branches are designed in a compact area to generate adjacent resonances, and their combination achieves broadband characteristics across the 4.83–9.57 GHz frequency band. The antenna has a miniaturized size of 60 mm × 60 mm, which is 1.6 λ g × 1.6 λ g (where λ g represents the guided wavelength at the center frequency), and it has a high realized gain of up to 10 dBi. The fully grounded structure also ensures good isolation between the antenna and the human body, thereby alleviating concerns regarding safety and radiation degradation in WBAN context. Simulation results indicate that the antenna maintains high performance levels during various bending tests. Given its favourable properties like ultra-wide bandwidth, compact size, low profile, high flexibility, and low specific absorption rate (SAR), the proposed design could find broad application prospects in high-speed WBAN systems. [ABSTRACT FROM AUTHOR]

The complex temporal-spatial variation of raindrop size distribution will affect the precision of precipitation quantitative estimates (QPE) produced from radar data, making it difficult to correct echo attenuation. Given the fact that microwave links can obtain the total path attenuation accurately, we introduce the concept of regional attenuation correction using a multiple-microwave-links network based on the tomographic reconstruction of attenuation coefficients. Derived from the radar-based equation, the effect of rainfall distribution on the propagation of radar and microwave link signals was analyzed. This article focuses on modeling of the tomographic reconstruction of attenuation coefficients and regional attenuation correction algorithms. Finally, a numerical simulation of regional attenuation correction was performed to verify the algorithms employed here. The results demonstrate that the correction coefficient (0.9175) falls between the corrected and initial field of radar reflectivity factor (root mean square error, 2.3476 dBz; average deviation, 0.0113 dBz). Compared with uncorrected data, the accuracy of the corrected radar reflectivity factor was improved by 26.12%, and the corrected rainfall intensity distribution was improved by 51.85% validating the region attenuation correction algorithm. This method can correct the regional attenuation of weather radar echo effectively and efficiently; it can be widely used for the radar attenuation correction and the promotion of quantitative precipitation estimation by weather radar.

A dual‐polarized wide‐beam (DPWB) antenna is optimized by a hybrid topology optimization (HTO) method, which combines the scalar isotropic material with penalization and the level set method. The HTO method has high optimization freedom degree, strong topology‐searching ability and fast convergence speed. The initial model of the antenna is designed as a dual‐feeding square microstrip patch antenna with short‐circuit metal walls around the patch. By optimizing the metal patch on the upper side of the model, the DPWB antenna is obtained. The DPWB antenna is symmetric with respect to both ports. When fed to either port, the half‐power beamwidth of the DPWB antenna can reach 166° (−82° ~ 84°) in the E‐plane and 124° (−62° ~ 62°) in the H‐plane. The performance is verified by both simulation and measurement. The DPWB antenna is further applied to a linear phased array, reaching an E‐plane scanning angle range of 160° (−80° ~ 80°) and an H‐plane scanning angle range of 122° (−61° ~ 61°), with the gain fluctuation less than 3 dB and the sidelobe level less than −10.1 dB. [ABSTRACT FROM AUTHOR]