Electromagnetic Interference Shielding Anisotropy of Unidirectional CFRP Composites

Carbon fiber-reinforced polymer (CFRP) composites have excellent mechanical properties and electromagnetic interference (EMI) shielding performance. Recently, their EMI shielding performance has also attracted great attention in many industrial fields to resolve electromagnetic pollution. The present paper mainly investigated the EMI shielding anisotropy of CFRP materials using a specified set-up of free-space measurement. The electrical conductivity of unidirectional CFRP composites was identified to vary with the fiber orientation angles, and the formula was proposed to predict the results consistent with the experimental. The obvious EMI shielding anisotropy of unidirectional CFRP composites was clarified by free-space measurement. The theoretical formula can predict the EMI shielding value at different carbon fiber orientation angles, and the predicted results were highly consistent with the experimental results. A comparison of the free-space measurement and the coaxial transmission line method was also conducted, which indicated that special attention should be paid to the influence of the anisotropy of CFRP composites on the shielding results. With those results, the mechanism of EMI shielding anisotropy of CFRP composites is clarified, which will provide an effective design of EMI shielding products with a designable shielding direction and frequency.

Green Agricultural Development Based on Information Communication Technology and the Panel Space Measurement Model

This study was conducted to promote the construction of China’s ecological civilization; to reduce harm to the environment; to quantify the performance of agricultural green development (GD); and to truly achieve green, sustainable, and healthy agricultural development. From the perspectives of resources and the environment, first, information communication technology and the panel space measurement (PSM) model were adopted to analyze relevant indicator data from 2000 to 2019 in China’s 30 provinces. Second, China’s agriculture was measured to explore the overall characteristics, temporal changes, and regional differences of agricultural development. A panel data measurement model was constructed using the generalized least squares method, and the main factors affecting performance development were analyzed, which were verified by giving examples. Third, the governance countermeasures and improvement directors were proposed for agricultural GD in China. It is found that the driving force of performance of agricultural GD in China mainly depends on technological progress and that technological efficiency determines the speed of agricultural development. The regional differences in performance of agricultural GD are obvious in China. The growth in the performance of agricultural GD in the eastern region is much higher than that of the central, western, and northeast regions. In addition, the results show that the performance of agricultural GD is extremely positively correlated with the agricultural economic level, fiscal support for agriculture policy, and the industrialization process and that it is extremely negatively correlated with the level of opening-up, adjustment of agricultural structure, and the environmental regulatory capability of the government. As a result, this study can provide some ideas for the realization of agriculture GD in China.

Broadband Radar Absorbing Structures with a Practical Approach from Design to Fabrication

In this study, a novel broadband radar absorbing volume structure (RAVS) is proposed and demonstrated with a practical point of view from design to fabrication. The proposed RAVS uses a design concept of repeatedly stacked carbon nanotube (CNT) composites and foam cores of the same thickness to improve the applicability to real structures while maintaining absorption performance. The repeatedly stacked CNT composites, which act as electrically lossy materials, result in the multiple scattering of incident electromagnetic waves trapped inside the structure. The trapped incident waves then lose their energy by multiple scattering. Based on this design concept, the RAVS designed through field analysis and parametric study achieved a −10 dB absorption performance from 4 GHz to 16 GHz. With reference to the design values, RAVS was fabricated for verification, and the absorption performance was measured using a free space measurement system. The measurement result showed excellent absorption performance that satisfied −10 dB from 5.8 GHz or less to 14 GHz.

State-Space Measurement Update for GNSS/INS Integrated Navigation

This paper theoretically derives the equivalence conditions for the loosely and tightly coupled GNSS/INS integration algorithms. Firstly, the equivalence is proved when using single epoch GNSS measurements, which means the GNSS processor provides standalone solution. Then, the equivalence proof is further extended for the filtering solutions, which are usually applied for differential GNSS and precise point positioning. Based on these, different state and measurement models for GNSS/INS integration navigation are summarized, and natural differences among these models are discussed. This indicates that once the same measurement and predict information are used, the integration would be equivalent no matter what kind of coupling schemes are used. A flight dataset with GNSS and tactical IMU data is used to evaluate the equivalence and discrepancies among four different measurement models, and the results confirm the theoretical derivations.