Suppression of Repeat-Intensive False Targets Based on Temporal Pulse Diversity

This paper considers the problem of suppressing the repeat-intensive false targets produced by a deception electronic attack (EA) system equipped with a Digital Radio Frequency Memory (DRFM) device. Different from a conventional repeat jammer, this type of jamming intensively retransmits the intercepted signal stored in a DRFM to the victim radar in a very short time-delay interval relative to a radar pulse wide. A multipeak matched-filtering output is then produced other than the merely expected true target. An electronic protection (EP) algorithm based on the space time block code (STBC) is proposed to suppress the adverse effects of this jammer. By transmitting a pulse sequence generated from the STBC in succession and the following cancellation process applied upon the received signal, this algorithm performs successfully in a single antenna system provided that the target models are nonfluctuating or slow fluctuating and the pulse repetition frequency (PRF) is comparatively high. The performance in white and correlated Gaussian disturbance is evaluated by means of Monte Carlo simulations

The aging response of a metastable β Ti alloy, BTi-6554

In this study the effects of different aging heat treatments on the properties and microstructure of a high strength, high toughness metastable β Ti, BTi-6554 (Ti-6Cr-5Mo-5V-4Al), have been compared. An initial β phase solution treatment was followed by aging at moderate temperatures in the α/β dual phase zone by either step aging directly from the solution treatment temperature or by quenching to room temperature prior to the aging heat treatment. The differing heat treatment methods have significant effects on the microstructure and mechanical properties

Adsorption properties of β-cyclodextrin modified hydrogel for methylene blue

With the development of dye and printing, production wastewater has become one of the most primary pollution sources of water and soil pollution. Most of the dyes are toxic substances, which have the “three-way” effect of carcinogenic, teratogenic and mutagenic. Therefore, it is a very difficult but significant issue to deal with the dye in the wastewater. Here, we report a study on low-cost, high-capacity hydrogels that remove water-soluble dyes. The hydrogel is prepared by crosslinking the β-cyclodextrin and functional monomer: acrylamido and 2-acrylamide-2-methylpropane sulfonic acid by aqueous solution polymerization, meanwhile, alkaline hydrolysis is also an important step for adsorption performance. After alkaline hydrolysis, the amide and sulfonic groups in the hydrogel were converted into carboxylate and sulfonate, which was beneficial to the adsorption of cationic dyes. This polymer could remove 96.58% methylene blue (400 mg/L) and only requires 0.02 wt%. Its maximum adsorption capacity for methylene blue could reach 2638.22 mg/g under equilibrium condition. It is the most powerful adsorbent used to treat dye wastewater, according to the report. It also provides some references for hydrogel treatment of dye wastewater.</p

Using Digital Cameras on an Unmanned Aerial Vehicle to Derive Optimum Color Vegetation Indices for Leaf Nitrogen Concentration Monitoring in Winter Wheat

Commercially available digital cameras can be mounted on an unmanned aerial vehicle (UAV) for crop growth monitoring in open-air fields as a low-cost, highly effective observation system. However, few studies have investigated their potential for nitrogen (N) status monitoring, and the performance of camera-derived vegetation indices (VIs) under different conditions remains poorly understood. In this study, five commonly used VIs derived from normal color (RGB) images and two typical VIs derived from color near-infrared (CIR) images were used to estimate leaf N concentration (LNC). To explore the potential of digital cameras for monitoring LNC at all crop growth stages, two new VIs were proposed, namely, the true color vegetation index (TCVI) from RGB images and the false color vegetation index (FCVI) from CIR images. The relationships between LNC and the different VIs varied at different stages. The commonly used VIs performed well at some stages, but the newly proposed TCVI and FCVI had the best performance at all stages. The performances of the VIs with red (or near-infrared) and green bands as the numerator were limited by saturation at intermediate to high LNCs (LNC &gt; 3.0%), but the TCVI and FCVI had the ability to mitigate the saturation. The results of model validations further supported the superiority of the TCVI and FCVI for LNC estimation. Compared to the other VIs derived using RGB cameras, the relative root mean square errors (RRMSEs) of the TCVI were improved by 8.6% on average. For the CIR images, the best-performing VI for LNC was the FCVI (R2 = 0.756, RRMSE = 14.18%). The LNC-TCVI and LNC-FCVI were stable under different cultivars, N application rates, and planting densities. The results confirmed the applicability of UAVbased RGB and CIR cameras for crop N status monitoring under different conditions, which should assist the precision management of N fertilizers in agronomic practices

Fluorescence enhancements of benzene-cored luminophors by restricted intramolecular rotations: AIE and AIEE effects

Photoluminescence of simple arylbenzenes with ready synthetic accessibility is enhanced by two orders of magnitude through aggregate formation; viscosity and temperature effects indicate that the emission enhancement is due to the restriction of their intramolecular rotations in the solid state