Novel color tunable LaCaGaO4:Bi3+,Eu3+ phosphors for high color rendering warm white LEDs

A series of LaCaGaO₄:xBi³⁺,yEu³⁺ (x = 0.002–0.04, y = 0.02–0.45) phosphors with adjustable emission colors were synthesized by high-temperature solid-state reaction. The samples were identified as pure phases by X-ray diffraction and Rietveld refinement, and the crystal structures were analyzed in detail. The LaCaGaO₄:xBi³⁺ phosphor shows an intense blue emission under near-ultraviolet excitation, originating from the ³P₁ → ¹S₀ transition. The spectrum analysis reveals that the Bi³⁺ ions occupy two luminescence centers in the LaCaGaO₄ host and that energy transfer can occur. A model of the energy transfer between the Bi³⁺ and Eu³⁺ ions was also created and studied in detail. As the Eu³⁺-concentration increased, the emission color of the LaCaGaO₄:0.005Bi³⁺,yEu³⁺ phosphor changed from blue to pink to red. In addition, the fluorescence lifetime, quantum yield, thermal stability, and other properties of the phosphors were characterized and analyzed. Finally, two white light-emitting diode devices with R_a values of 96.6 and 95 and correlated color temperatures of 4578 and 3324 K were fabricated, indicating the potential of phosphors for warm white lighting applications.     

优化微生物菌群结构强化处理腌制含盐废水

通过研究不同菌剂在目标废水中的生长曲线及COD的变化,筛选优势菌剂。结果显示,所购买的1号菌剂为优势耐盐菌剂,其最佳接种量(以体积分数计)为15%。将该菌剂按最佳接种量加入到反应器中,当进水COD为2 500 mg/L,盐度为8 000 mg/L时,对比对照组,COD处理效果明显;当盐度突然提高到10 000 mg/L时,出水COD变化稳定,待短暂适应新环境后,出水COD又趋于盐度提高前的稳定状态。     

精炼处理对Al-Si-Mg合金熔体中TiB2粒子的影响

加入Al-5Ti-1B中间合金的Al-Si-Mg合金熔体,经N2气精炼处理后试样的晶粒尺寸较精炼处理前明显粗化,即精炼处理显著削弱了Al-5Ti-1B中间合金对Al-Si-Mg合金的细化效果。分析认为,精炼过程中一部分TiB2粒子及其聚集团极易被N2气泡捕获并游离出熔体,使异质形核衬底数目大幅减少。针对精炼对细化效果的不利影响,提出了两种解决方案,即采用Al-5Ti-0.6B-0.2C中间合金或先精炼后添加细化剂的操作工艺。     

Dynamic Stability Analysis of Linear Time-varying Systems via an Extended Modal Identification Approach

The problem of linear time-varying(LTV) system modal analysis is considered based on time-dependent state space representations, as classical modal analysis of linear time-invariant systems and current LTV system modal analysis under the ‘‘frozen-time' assumption are not able to determine the dynamic stability of LTV systems.Time-dependent state space representations of LTV systems are first introduced, and the corresponding modal analysis theories are subsequently presented via a stabilitypreserving state transformation. The time-varying modes of LTV systems are extended in terms of uniqueness, and are further interpreted to determine the system's stability. An extended modal identification is proposed to estimate the time-varying modes, consisting of the estimation of the state transition matrix via a subspace-based method and the extraction of the time-varying modes by the QR decomposition. The proposed approach is numerically validated by three numerical cases, and is experimentally validated by a coupled moving-mass simply supported beam experimental case. The proposed approach is capable of accurately estimating the time-varying modes, and provides a new way to determine the dynamic stability of LTV systems by using the estimated time-varying modes.     

Power management in co-phase traction power supply system with super capacitor energy storage for electrified railways

Railway Engineering Science - Increasing railway traffic and energy utilization issues prompt electrified railway systems to be more economical, efficient and sustainable. As regenerative braking...     

环保型城市生态景观照明节能数字化辅助设计

针对环保型城市生态景观照明时平均照度不高、耗电量过大等问题,提出环保型城市生态景观照明节能数字化辅助设计。根据国家规定照明标准,构建环保型城市生态景观照度参照值以及城市住宅防控干扰光强度限制值,并依据规定单位面积照明功率密度值,设定单位面积安装功率限制;依据以上设定标准,通过数字化辅助设计城市生态景观照明原则以及灯具选取指标,构建景观照明节能数字化控制指标体系,结合照明节能评估与改进意见,实现生态景观照明节能数字化控制。分析结果显示:中央布灯方式的路面平均照度与路面总均匀度更高,节能效果高于对称与交错布置;白天场景节能效果高于夜间场景,最高节能占比达到60%;布灯间距为50 cm、灯具角度为0°时,平均照度最高,节能效果最佳。     

Microwave absorption properties of double-layer absorbers based on spindle magnetite nanoparticles and flower-like copper sulfide microspheres

In this work, the spindle magnetite nanoparticles (SMNPs) and flower-like copper sulfide microspheres (FCSMSs) were synthesized via hydrothermal method. The structures, chemical composition and morphologies of samples were analyzed and characterized in detail. The microwave absorption properties of single-layer and double-layer absorbers were investigated based on the electromagnetic transmission line theory in the frequency range from 2 to 18 GHz. The results show that the double-layer absorbers consisting of FCSMSs as matching layer and SMNPs as absorbing layer display superior microwave absorbing performance compared to the single-layer ones due to the proper combination of magnetic loss of SMNPs and dielectric loss of FCSMSs, and the improved impedance matching characteristics. When the thicknesses of the absorbing layer and the matching layer are 1.6 and 0.4 mm, respectively, the minimum reflection loss reaches ??74.3 dB at 10.9 GHz, and the efficient absorption bandwidth is up to 5.34 GHz (8.46–13.8 GHz). The optimal SMNPs/FCSMSs double-layer absorbers can become a novel microwave absorption material with strong-absorption and broad-band.     

静电纺介孔氧化硅基纳米纤维的研究进展

介孔氧化硅是最为典型的介孔材料,其具有比表面积高、孔径均一、易于表面修饰等优异特性,广泛应用于吸附分离、催化、传感以及物质负载与缓释等领域。关于粉体和薄膜形态的介孔氧化硅已有大量报道,但纤维形态,特别是连续纤维形态的介孔氧化硅材料的制备仍然是一项挑战。近年来随着静电纺技术的发展,连续纤维形貌的介孔氧化硅材料的制备取得了重要进展。根据纤维介孔结构的有序度和介孔结构引入方式的不同,对静电纺介孔氧化硅基纳米纤维进行详细的介绍。     

元素粉末法制备SiC_p/2024Al复合材料扩散均匀化研究

利用元素粉末真空热压工艺制备SiCp/2024Al复合材料,采用光学显微镜(OM)、扫描电镜(SEM)和X射线衍射(XRD)对真空热压中各元素粉末的扩散均匀化过程及扩散均匀化温度和保温时间对颗粒增强Al基复合材料显微组织的影响进行了研究。结果表明,该复合材料热压态组织中有Cu的富集相存在;随着扩散均匀化处理过程中温度的升高和时间的延长,Al2CuMg相完全溶入Al基体中,Cu的扩散逐渐充分,各元素分布趋于均匀。该复合材料最佳扩散均匀化处理工艺参数为500℃保温3h。     

丙酮酸化壳聚糖纳米粒子制备研究

壳聚糖在印染、环保、食品、日化、医药等领域的应用十分广泛。但壳聚糖也有局限性,为了进一步拓展壳聚糖的应用范围和开发出一些性能优良的新化合物,所以要对壳聚糖进行化学改性。文章利用壳聚糖C2位上活泼氨基与丙酮酸进行席夫碱反应,制取丙酮酸化壳聚糖。