[en] (Pb_0.87La_0.02Ba_0.1)(Zr_0.7Sn_0.3-x Ti_x)O₃ (PLBZST, 0.06 ≤x ≤0.09) antiferroelectric ceramics were fabricated by conventional solid state reaction process, and their ferroelectric, dielectric, and pyroelectric properties were systemically investigated. PLBZST with different Ti content were all confirmed to be in an antiferroelectric phase at T=50 C, which is close to the lowest phase transition temperature. Compared with conventional FE ceramics, PLBZST antiferroelectric ceramics exhibited higher electric field induced pyroelectric coefficient (p). As the content of Ti increased from 0.06 to 0.09, the pyroelectric coefficient increased from 1000 to 6500 μC/m ²K under a 500 V/mm DC bias field. The maximum pyroelectric coefficient of 8400 μC/m ²K was obtained at x=0.09 when an 850 V/mm DC bias field was applied, which is far larger than that of conventional phase transition pyroelectric materials. Large pyroelectric response is beneficial for the development of infrared detectors and thermal imaging sensors. (orig.)

[en] A real all-digital and all-coherent arbitrary ultra wideband pulse generator is presented. The generator is a multi-core & single-channel (MCSC) direct-digital-synthesizer (DDS) which consists of 16 sub-cores and a high speed digital analog converter AD9739. The ultra-wideband pulses are generated according to the proposed anti-Nyquist sampling theorem. Their frequencies are aliasing in the first and second Nyquist zones. By purposely aliasing the spectrum, the output bandwidth can be increased greatly. All the parameters including pulse width, bandwidth, amplitude, pulse type, pulse repeat frequency and modulation are user-controlled on-the-fly. In order to test the performance, monopole pulse, monocycle pulse and two 4th order Gaussian pulses are generated. The monopole pulse whose pulse rate can achieve 2.5 GHz has a 10% pulse width of 450 ps, a 200 mV peak amplitude and a -10 dB bandwidth of 2.15 GHz. (paper)

[en] xSrFe₁₂O₁₉/(1  −   x )CoFe₂O₄ (0  ⩽   x   ⩽  1.0) composites with about 2 µ m average particle size were prepared by a conventional solid-state route. Results show that the xSrFe₁₂O₁₉/(1  −   x )CoFe₂O₄ composites exhibit a typical single-phase magnetic behavior, suggesting the existence of an exchange-coupling effect. The saturation magnetization ( M _s) of the composites sintered at 1230 °C increases from 49.05 to 64.84 A · m² · kg⁻¹ with the increase of CoFe₂O₄ content. Compared with single-phase CoFe₂O₄, the coercivity ( H _c) of the composites is enhanced markedly from 10.47 to 116.66 kA · m⁻¹. The enhancement of magnetic properties is ascribed to the high coercivity of SrFe₁₂O₁₉, high saturation magnetization ( M _s) of CoFe₂O₄ and the exchange-coupling effect between SrFe₁₂O₁₉ and CoFe₂O₄ ferrites. (paper)

[en] Modified kaolinite clay with 25% (w/w) aluminium sulphate and unmodified kaolin were investigated as adsorbents to remove Pb(II) from aqueous solution. The results show that amount of Pb(II) adsorbed onto modified kaolin (20 mg/g) was more than 4.5-fold than that adsorbed onto unmodified kaolin (4.2 mg/g) under the optimized condition. In addition, the linear Langmuir and Freundlich models were used to describe equilibrium isotherm. It is observed that the data from both adsorbents fitted well to the Langmuir isotherm. The kinetic adsorption of modified and unmodified kaolinite clay fitted well to the pseudo-second-order model. Furthermore, both modified and unmodified kaolinite clay were characterized by X-ray diffraction, Fourier transform infrared (FT-IR) and scanning electron microscope (SEM). Finally, both modified and unmodified kaolinite clay were used to remove metal ions from real wastewater, and results show that higher amount of Pb(II) (the concentration reduced from 178 to 27.5 mg/L) and other metal ions were removed by modified kaolinite clay compared with using unmodified adsorbent (the concentration reduced from 178 to 168 mg/L).

[en] In this paper, firstly, the influence factors of different electronic loads on radar are analyzed from various angles, and a resource allocation model is built for penetration scenarios. Then, the evaluation indexes of radar in different working stages are explained and fused to construct a scientific and reasonable objective function. Finally, a genetic particle swarm(GAPSO) algorithm based on two-dimensional parallel coding is creatively proposed, and the parameters of the algorithm are adjusted adaptively to improve the performance of the algorithm. The simulation results show that the improved GAPSO algorithm has obvious effectiveness and superiority in solving the resource allocation problem in process of jammers shielding target penetration. (paper)

[en] Highlights: • BN evenly dispersed in ceramic matrix and enhanced heat transfer due to the vibrations of whole chain and phonon scattering. • The pyroelectric coefficient, thermal conductivity and dT/dt have been improved with rapid heat transfer. • The output power of the harvester boosted to 65.6% with 0.1 wt% BN. -- Abstract: Recently, recycling energy from wasted heat with pyroelectric materials has received significant attention. However, pyroelectric energy harvesters generally suffer from a low energy efficiency due to the low rates of heat transfer. Here, we report high-performance thermal energy harvesting using novel hybrid pyroelectric ceramics with greatly improved heat transfer and rate of temperature changes. This is achieved by evenly dispersing 0.1 wt% hexagonal boron nitride (hBN) nanosheets into a Pb[(Mn_1/3Nb_2/3)_1/2(Mn_1/3Sb_2/3)_1/2]_0.04(Zr_0.95Ti_0.05)_0.96O₃ (lead magnesium niobate-lead antimony-manganese-lead zirconate titanate: PMN-PMS-PZT) ceramic matrix. Due to the vibrations of whole chain and phonon scattering, heat transfer through the hybrid crystalline chain is more efficient than that of unfilled PMN-PMS-PZT. It is demonstrated that the harvested power was increased by up to 65.6%. This work paved an efficient and cost-effective way to largely improve the traditional pyroelectric ceramic for thermal energy harvesting.