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To study the characteristics of debris generated by satellite breakup, three hypervelocity impact tests for simulated satellites are carried out at the ballistic range. The simulated satellites are impacted by aluminum blunt nosed cone projectiles at velocities ranging from 3.2km/s to 4.2km/s. The breakup fragments are collected, weighed, size measured and catalogued. The test results show that; 1) the cumulative number of debris is expressed as a good linear relation to characteristic length or mass in logarithmic coordinates, 2) the debris size and mass distributions are very similar in basic forms and patterns. The expression formulas of size and mass distributions are established by data fitting, and the inherent relation between debris size and mass is analyzed. The test results are compared with NASA standard breakup model, and differences and reasons are discussed. [ABSTRACT FROM AUTHOR]

Currently, against the background of carbon trading policies, carbon dioxide is attributed commodity properties for market trading within carbon trading. Relevant data show that, in recent years, logistics enterprises have been facing continuously growing demand and carbon emissions have continuously increased; therefore, enterprises urgently need to strengthen their green transformation. Scientific and rational decision-making tools play a meaningful role in helping enterprises improve their competitiveness. In this context, a new three-way decision-making model based on attribute reduction and hesitation degree is proposed. First, an attribute reduction is performed. The attributes of three types of logistics enterprises are simplified according to the carbon emission evaluation attributes proposed in this study to determine their respective minimum attribute sets. Subsequently, the decision and loss function matrices are established considering the hesitation degree. The conditional probability is calculated using intuitionistic fuzzy similarity, and the probability threshold is calculated using the loss function matrix considering the hesitation degree. Finally, case studies and comparative analyses are conducted to illustrate the practicality and rationality of the proposed method. [ABSTRACT FROM AUTHOR]

Acceleration and compression on deep Convolutional Neural Networks (CNNs) have become a critical problem to develop intelligence on resource-constrained devices. Previous channel pruning can be easily deployed and accelerated without specialized hardware and software. However, weight-level redundancy is not well explored in channel pruning, which results in a relatively low compression ratio. In this work, we propose a Low-rank Approximated channel Pruning (LAP) framework to tackle this problem with two targeted steps. First, we utilize low-rank approximation to eliminate the redundancy within filter. This step achieves acceleration, especially in shallow layers, and also converts filters into smaller compact ones. Then, we apply channel pruning on the approximated network in a global way and obtain further benefits, especially in deep layers. In addition, we propose a spectral norm based indicator to coordinate these two steps better. Moreover, inspired by the integral idea adopted in video coding, we propose an evaluator based on Integral of Decay Curve (IDC) to judge the efficiency of various acceleration and compression algorithms. Ablation experiments and IDC evaluator prove that LAP can significantly improve channel pruning. To further demonstrate the hardware compatibility, the network produced by LAP obtains impressive speedup efficiency on the FPGA. [ABSTRACT FROM AUTHOR]

Localization technique for space debris impacted typical spacecraft protection structure with PVDF sensors is studied in theory and test. The structure types including aluminum plate, curved aluminum plate and Whipple shield are studied to verify the applicability of this localization technique. The localization method based on hyperbola theory is investigated. The hyperbola localization theory is validated by the test of air rifle and hypervelocity ballistic range. The velocity range of the projectile is from 100m/s to 3km/s. The structure types investigated are aluminum plate with thickness of 2mm and Whipple shield with 10cm distance between front and rear wall with thickness of 1mm. Analysis shows that the localization technique based on PVDF sensor in this study is proved to be applicable to detect the position of typical spacecraft protection structure impacted by space debris. [ABSTRACT FROM AUTHOR]

A new breakup threshold model is presented for a satellite under hypervelocity impact, energy density em, the ratio of the kinetic energy to the mass in the impact channel is used to estimate whether the satellite is broken up, and µc, the ratio of the mass of debris with clear statistic regularity to the total debris mass, to describe the degree of breakup: The bigger the µc, the higher the degree of breakup. It is found from numerical simulation that the minimum energy density of breakup is 3. 62 x 10² J/g. The new breakup threshold model is developed by a function among µc, em and η (ratio of satellite's mass of impact channel to its total mass). [ABSTRACT FROM AUTHOR]