快速热响应复合材料的储/放热性能分析

以膨胀石墨为无机支撑材料、石蜡为有机相变材料,制备出高导热系数和储热密度的快速热响应复合材料,并构建传热性能测试系统对该复合材料的储/放热性能进行研究分析。研究结果表明,复合材料不仅能在熔融状态下保持形状稳定,而且显著提高了在储/放热过程的传热性能,从而有效地解决了传统相变材料高储热密度和低导热系数之间的矛盾。     

液氮冷却条件下激光快速熔凝Ni-28 wt%Sn合金组织演变

研究了在液氮冷却条件下激光快速熔凝Ni-28 wt%Sn亚共晶合金的组织演化过程. 结果显示, 熔池从上至下可以分为三个区域: 表层为平行激光扫描方向的α-Ni转向枝晶区; 中部为近乎垂直于熔池底部外延生长的α-Ni柱状晶区; 底部为少量的残留α-Ni初生相和大量的枝晶间(α-Ni+Ni₃Sn) 共晶组织. 激光熔凝区组织受原始基材组织的影响很大, 熔池中的α-Ni枝晶生长方向受到了热流方向和枝晶择优取向的双重影响. 与基材中存在的层片状、棒状和少量离异(α-Ni+Ni₃Sn)共晶的混合组织相比, 熔池内的共晶组织皆为细小的规则(α-Ni+Ni₃Sn)层片状共晶, 皆垂直于熔池底部外延生长, 并且从熔池顶部至底部, 共晶层片间距逐渐增大. 分别应用描述快速枝晶生长的Kurz-Giovanola-Trivedi 模型和描述快速共晶生长的Trivedi-Magnin-Kurz模型对熔池表层凝固界面前沿的过冷度进行估算, 发现熔池表层α-Ni 枝晶和(α-Ni+Ni₃Sn)层片共晶的生长过冷度在50.4-112.5 K 之间, 远大于相应深过冷凝固(α-Ni+Ni₃Sn) 反常共晶生长的临界过冷度20 K, 这说明文献报道的临界过冷度并不是反常共晶出现的充分条件.     

Determination of 24 pesticides residues in mineral and peat soils by modified QuEChERS method and gas chromatography

A simple extraction and cleanup procedure has been developed for the analysis of 24 organophosphorus (OP), organochlorine (OC) and pyrethroid (PY) pesticides in mineral and peat soils using modified QuEChERS method. The pesticides were extracted from the soil with acidified acetonitrile. The water was removed from the extract by salting out with sodium chloride and addition of magnesium sulfate. For OP pesticides, the extracts were cleaned up with 0.2 g of primary secondary amine packed in glass Pasteur pipette and determined by gas chromatography with flame photometric detector. For OC and PY pesticides, the extracts were cleaned up with 0.2 g of silica gel packed in a glass Pasteur pipette and determined by gas chromatography with electron capture detector. After the cleanup, the extracts had lower colour intensity and reduced matrix interferences. The recovery of the OP and OC pesticides for mineral and peat soils determined at 0.01–1.0 mg kg^?1 fortification levels ranged from 79.0–120.0% and 82.2–117.6%, respectively. The detection limits for OP and OC pesticides were 0.001–0.01 and 0.002–0.005 mg kg^?1, respectively. The recovery of the PY pesticides ranged from 87.5–111.7% at the detection limits of 0.002–0.010 mg kg^?1. The relative standard deviations for all pesticides studied were below 10.8%. The modified method was simple, fast, and had utilized less reagents than the conventional methods. The method was applied to the determination of the pesticide residues in mineral and peat soil samples collected from the vegetable farms.     

脱合金制备纳米多孔双金属氧化物NiMoO4及其电化学性能

采用快速凝固与脱合金相结合的方法制备纳米多孔Ni-Mo合金,然后退火获得三维双连续纳米多孔NiMoO₄,采用XRD、SEM、TEM对多孔NiMoO₄的成分、形貌和结构进行表征,并通过循环伏安、恒电流充放电等方法测试多孔NiMoO₄电极的电化学性能。结果表明,Ni₅Mo₅Al₉₀和Ni_2.5Mo_2.5Al₉₅经脱合金和退火均可获得纳米多孔NiMoO₄,Mo元素对脱合金具有钉扎作用,可减小多孔合金的骨架和孔隙尺寸,由Ni₅Mo₅Al₉₀合金获得纳米多孔NiMoO₄表现出更为优异的超电容性能,其在1 A·g^-1电流密度比容量达708 F·g^-1,当电流密度增加20 A·g^-1,其比容保持率达57.1%。在4 A·g^-1电流密度下循环充放电1 000次,其比容保持率达91.2%。     

基于QuEChERS前处理技术和弱阳离子交换色谱的牛奶和奶粉中三聚氰胺的快速检测方法

应用QuEChERS前处理技术,并结合弱阳离子交换色谱,建立了牛奶和奶粉中三聚氰胺的快速检测方法。样品使用医用酒精(乙醇含量75%)和一种新型脂肪吸附(LAS)材料超声振荡处理,在沉淀(吸附)蛋白质和脂肪的同时提取三聚氰胺,然后经8000 r/min离心,上清液过膜直接分析。色谱分析在弱阳离子交换色谱柱(WCX)上进行,采用2 mmol/L pH为3.8的磷酸二氢钾水溶液为流动相,在5 min内实现分离分析。结果表明,该方法在0.02～20 mg/L内线性相关系数大于0.9999。在1～50 mg/kg添加浓度范围内,牛奶的平均回收率为98.9%～105.2%,相对标准偏差(RSD)为0.9%～3.4%;奶粉的平均回收率为86.4%～102.9%, RSD为1.5%～6.7%。本方法的检出限为0.05 mg/kg(牛奶)和0.1 mg/kg(奶粉)。整个分析检测过程没有使用有毒有害有机溶剂,是一种绿色的分析方法。     

纤维素键合型手性整体柱的制备及其在快速手性分离中的应用

采用N-丙烯酰琥珀酰亚胺(NAS)为基质单体,乙二醇二甲基丙烯酸酯(EDMA)为交联剂,原位聚合制备聚(NAS-co-EDMA)毛细管整体柱,并通过化学键合法将自合成的纤维素-三(4-甲基苯甲酸酯)(CTMB)共价键合到整体柱上,制备用于快速手性分离的纤维素键合型手性整体柱.优化了整体柱制备和衍生化条件;通过对固定相红...     

模拟燃烧热分解气体产物的在线分析-GAP/HMX混合体系压力下的快速热裂解

用T - Jump/FTIR在线联用分析技术,研究了GAP/HMX混合体系在模拟燃烧条件下快速加热高温高压的热裂解.结果表明,与GAP和HMX的单组分比较,GAP/HMX混合体系主要气体产物HCN的浓度明显提高,温度对主要气体产物浓度比HCN/NH3和N2O/HCN的影响与对单组分趋势一致,即随温度的提高HCN/NH、...     

基于微流控技术的磁免疫荧光法在EB病毒检测中的应用

EB病毒(Epstein-Barr virus,EBV)的早期诊断能够降低患者发生重大疾病的风险.临床上常用的EBV抗体的检测方法存在耗时长、试剂消耗大和效率低等缺点.相比于传统的检测方法,微流控(microfluidics)技术具有高通量、试剂消耗少,污染少和自动化程度高等优点,磁免疫荧光技术具有检测效率高、信号强等...     

精化的二次残量迭代法

According to the refined projection principle advocated by Jia[8], we improve the residual iteration method of quadratic eigenvalue problems and propose a refined residual iteration method. We study the restarting issue of the method and develop a practical algorithm. Preliminary numerical examples illustrate the efficiency of the method.     

Comparison of models and visualization of total volatile basic nitrogen content in mutton using hyperspectral imaging and variable selection methods

Hyperspectral imaging combined with variable selection methods was used to perform the rapid and accurate detection and visualization of total volatile basic nitrogen content in mutton. For each sample, several spectra were extracted from the region of muscle pixels for modeling, and the model performance was improved and better than the model established with average spectrum extracting from each sample. By two steps of variable screening with competitive adaptive reweighted sampling and stepwise regression methods, the efficient dimensionality reduction of spectral data was achieved, and the important characteristic variables were selected. The nonlinear model significantly improved the model predictive capability, and the visualization distribution map based on the model was consistent with the actual change of meat spoilage.