淀粉接枝丙烯酸高吸水性树脂制备及性能研究

以淀粉和丙烯酸为主要原料通过共聚反应制备淀粉接枝高吸水性树脂,研究了淀粉种类对高吸水性树脂性能的影响,并对高吸水性树脂进行生物降解实验.结果表明,高吸水性树脂的吸水率达到1079 g/g,60℃下8 h的保水率约为15%,在土壤中35 d后其降解率为29%.     

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。     

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。     

Novel efficient SrMgY3(SiO4)3F:Ce3+,Tb3+ phosphor with tunable color and thermal stability through energy transfer

A novel apatite-type SrMgY₃(SiO₄)₃F was synthesized by a high-temperature solid-state reaction. The crystal structure was refined using powder X-ray diffraction data. SrMgY₃(SiO₄)₃F crystallizes in P6₃/m hexagonal space group with lattice parameters of a = b = 9.45270 Å, c = 6.77617 Å, and V = 524.357 Å³. The incorporation of the Ce³⁺ and Tb³⁺ ions into the matrix can generate bright blue and green lights under ultraviolet (UV) light excitation. The codoped Ce³⁺ and Tb³⁺ in SrMgY₃(SiO₄)₃F can effectively improve green emission intensity and thermal stability through the energy transfer from the Ce³⁺ to Tb³⁺ ions. With the increase of Tb³⁺-doping content, the luminescent color of phosphor changes from blue to cyan and finally to green. SrMgY₃(SiO₄)₃F:0.06Ce³⁺,0.90Tb³⁺ phosphor exhibited intense green light emission with a quantum yield of 59.49% and good thermal stability, with an emission intensity at 150°C was 96% of that at 30°C. Finally, the prepared sample was coated on 365 nm UV chips to fabricate white light-emitting diodes with a color rendering index of 82.6 and a correlated color temperature of 2912 K, demonstrating its potential for applications in display and lighting.     

赖氨酸改性壳聚糖的制备研究

本实验以赖氨酸改性壳聚糖为研究对象，对赖氨酸对壳聚糖的改性进行研究。改变壳聚糖与赖氨酸的质量比研究其改性效果。差示扫描量热分析、红外光谱表征以及水溶性试验表明赖氨酸改性壳聚糖是成功的。赖氨酸与壳聚糖的比例为3：1的时，改性较好。赖氨酸改性后的壳聚糖其水溶性显著提高。     

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。     

基于高速数控前瞻控制技术的误差补偿算法

为减少高速数控切削加工时大误差量补偿产生的有害机械振动,提出基于前瞻控制技术的误差补偿新方法.该方法的实现基于以下步骤:针对误差补偿器对中断服务程序单元位置控制的影响,建立具有前瞻控制功能的控制系统硬件框架与相应软件结构,将误差补偿器从中断服务程序单元位置控制环节去除;为获得误差补偿所需要的速度值,阐述前瞻控制速度规划算法的具体实现;根据误差数据段与插补数据段的位置关系,将误差数据进行分类;根据分类,结合前瞻控制算法所确定的速度规划曲线,误差数据在加工时通过指令解析器与插补数据在一个或多个插补周期内线性融合,从而实现误差的补偿.     

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。     

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.     

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.