盾构壁后注浆对地表沉降影响模拟研究

结合宁波轨道交通某区间隧道施工, 研究了盾构壁后注浆对地表沉降的影响, 考虑壁后注浆压力消散和浆液固结硬化过程, 采用FLAC3D有限元软件对开挖过程模拟计算, 分析了不同注浆量和不同注浆压力下的地表沉降变化规律以及浆液硬化作用对地表沉降和管片位移的影响规律, 并将地表沉降和拱顶位移的计算值和实测值进行对比分析. 结果表明: 本工程最佳注浆量4.0~5.0m3, 最佳注浆压力约0.3MPa; 硬化作用引起的地表沉降占总沉降约5%, 引起的管片位移占总位移约15%. 针对宁波土质, 合理确定注浆量和注浆压力能够有效控制地表沉降, 合理配制浆液, 实时监控注浆量、注浆压力和浆液强度, 能够有效控制管片的上浮和变形.     

Synthesizing UHMWPE Using Ziegler-Natta Catalyst System of MgCl2(ethoxide type)/ TiCl4/tri-isobutylaluminum

Summery: A Ziegler-Natta catalyst of MgCl₂ (ethoxide type)/TiCl₄ has been synthesized. In order to obtain ultra high molecular weight polyethylene (UHMWPE) tri-isobutylaluminum which is less active to chain transfer was used as cocatalyst. Slurry polymerization was carried out for the polymerization of ethylene while, dilute solution viscometry was performed for the viscosity average molecular weight (Mv) measurement. The effect of [Al]/[Ti] molar ratio, temperature, monomer pressure and polymerization time on the Mv and productivity of the catalyst have been investigated. The results showed increasing [Al]/[Ti] ratio in the range of 78–117, decreased the Mv of the obtained polymer from 7.8 × 10⁶ to 3.7 × 10⁶ however, further increase of the ratio, resulted in decreased of by much slower rate up to [Al]/[Ti] = 588. The higher pressure in the range of 1–7 bars showed the higher the Mv of the polymer obtained, while increasing temperature in the range of 50 to 90 °C decreased the Mv from 9.3 × 10⁶ to 3.7 × 10⁶. The Mv rapidly increase with polymerization time in the first 15 minutes of the reaction, this increase was slowly up to the end of the reaction (120 min). Increasing [Al]/[Ti] ratio raised productivity of the catalyst in the range studied. Rising reaction temperature from 50 to 75 °C increased the productivity of the catalyst however, further increase in the temperature up to the 90 °C decreased activity of the catalyst. Monomer pressure in the range 1 to 7 bars yields higher productivity of the catalyst. Also by varying polymerization conditions synthesizing of UHMWPE with Mv in the range of 3 × 10⁶ to 9 × 10⁶ was feasible.     

离心-凝胶注模成型技术制备梯度碳纤维/HA复合材料

以经过低温氧化和提拉HA溶胶改性处理的碳纤维为增强体,采用离心-凝胶注模成型技术制备梯度碳纤维/HA复合材料.观察了碳纤维改性处理后的形貌,研究了碳纤维/HA浆料的特性,以及浆料的凝胶固化过程.分析了离心转数、碳纤维含量对梯度复合材料生坯密度梯度的影响.观察了烧结后梯度复合材料的显微组织,并测量了不同烧结温度和碳纤维分布的HA复合材料的抗弯强度和断裂韧性.研究结果表明改性处理碳纤维表面形成一层致密的、结合性能较好的膜层,烧结后可以很好地连接基体和碳纤维.在pH =9,分散剂含量为5wt;,浆料固相含量为40wt;,碳纤维含量为2wt;时,碳纤维/HA浆料具有良好的分散性和稳定性.当催化剂和引发剂含量均为0.9wt;时,起始凝胶和终止固化时间与离心成型工艺相匹配.当离心转数为1000 r/min,碳纤维含量为2wt;时,离心-凝胶注模成型所得试样具有良好的密度梯度,1100℃烧结2h后,该复合材料的抗弯强度达到最大值101.7 MPa;断裂韧性为1.98 MPa·m1/2,分别比干压成型制备的均匀碳纤维/HA复合材料提高了29.7;和25.3;.     

90°弯管内冰浆流动特性数值模拟

基于欧拉法建立了冰浆流动的混合模型,对冰浆在90°弯管内的流动特性进行了数值模拟研究,获得了弯管内冰浆的流场和冰晶颗粒的运动轨迹,探讨了弯管管径、曲率半径及冰浆的流速、浓度参数对弯管内冰浆压降的影响,并对弯管压降的模拟结果与实验结果进行对比,两者吻合较好。结果表明:在计算参数范围内,弯管压降随冰浆流速、浓度及弯管曲率半径的增大而增大,随弯管管径的增大而减小;冰浆在弯管内流动形成二次流现象,两个漩涡区域出现在弯管截面两侧;漩涡导致部分冰晶颗粒的运动轨迹发生改变,并使其向弯管下方的负压区聚集,增大了冰晶颗粒的碰撞几率。     

A Simple and Fast Method for Manganese Determination in Antihypertensive Drugs by Slurry Sampling Graphite Furnace Atomic Absorption Spectrometry

Abstract

A simple and rapid procedure for the determination of manganese in anti‐hypertensive drugs is proposed. The samples were treated with dilute nitric acid (1.2% v/v) with stirring using a vortex stirrer to yield a slurry. To determine the best conditions for analysis by graphite furnace atomic absorption spectrometry (GF AAS), a planning factorial was initially employed that demonstrated that the non‐use of chemical modifiers and the use of lower pyrolysis temperatures were more appropriate. Next, the pyrolysis and atomization temperature curves were obtained. The best pyrolysis and atomization temperatures encountered were 500 and 2200°C, respectively. Calibration was performed by matrix matching. The characteristic mass was 0.70±0.14 pg (the recommended mass was 0.60 pg); the limits of detection and quantification were 0.23 and 0.77 µg l^?1, respectively. The precision obtained in the intra‐ and inter‐assay studies of the drug spiked with 0.5, 1.0 and 1.5 µg l^?1 of Mn did not exceed 11% (n=7). Recovery studies of the drug spiked with three levels (n=7) of Mn yielded results between 101.0±4.5 and 116.3±9.7%. The results of an analysis of a certified urine sample (two levels of Mn) agreed at a 95% level of confidence. Forty‐eight antihypertensive drug samples were analyzed, and the results varied from 2.9 ng to 1.9 µg of Mn per capsule^?1.     

水基料浆冷冻浇注成型多孔陶瓷孔结构研究

对水基料浆冷冻浇注成型多孔陶瓷中孔隙结构特征进行了探讨.研究发现:采用水基料浆冷冻浇注成型的多孔陶瓷孔隙为薄片状或层状,这构成了冷冻浇注成型多孔陶瓷的基本形貌特征.较快的冷冻速率可以减小冷冻浇注成型多孔陶瓷的孔径尺寸.料浆中粉体颗粒特别是微小颗粒的存在会对结冰形貌产生影响,颗粒粒径减小会导致冰晶尺寸减小,相应的孔径变小;但尺寸在几十纳米的微小颗粒会促进冰晶生长,导致孔径变大.     

不锈钢宽口径填充毛细管液相色谱柱

 设计了一种零死体积的二通式柱尾结构和一种使匀浆填料均匀进入色谱柱管内的储料池 ,研究了制备内径在 0 5mm～ 1 0mm的不锈钢宽口径填充毛细管液相色谱柱的方法。详述了以不同牌号、规格的反相ODS类固定相制备的不同柱长的色谱柱的性能。通过折合板高 /折合流速关系和不对称因子对柱性能进行了评价 ,结果表明 ,该方法制备的色谱柱柱效达到理论值的 75 %以上、RSD为 6% ,稳定性也很好。将其应用于抗癫痫药物和氯苯类化合物的分析 ,结果令人满意。     

煤的岩相显微组分对水煤浆性质的影响

通过对不同变质程度煤的岩相显微组分分析，考察了煤的岩相显微组分对水煤浆性质的影响。结果表明，在相近的灰分含量下，对于烟煤较高的镜质组、较低的丝质组含量有利于煤的成浆性和稳定性。从多元线性回归结果来看，镜质组和丝质组的含量对煤浆成浆性和流变性的影响较为明显，稳定组分的含量对水煤浆性质的影响较小。丝质组含量对稳定性作用明显，当煤中丝质组含量低于30%时，煤浆产生软沉淀的时间一般都在15d以上。煤的平均最大镜质组反射率与煤的成浆性具有较好的相关性，成浆性随煤的最大镜质组反射率增加而增加，因此可以用最大镜质组反射率来预测煤的成浆性。     

一种适用于三相过程的高活性和高稳定性的甲醇合成催化剂

Methanol is one of the most important basic feedstock for the organic chemical industry and also is a potential fuel. Although the technology for the production of methanol is generally considered mature, much attention is still being paid to the improvements of the process, equipment and catalyst.     

Pretreatment of corn stover using wet oxidation to enhance enzymatic digestibility

Corn stover is an abundant, promising raw material for fuel ethanol production. Although it has a high cellulose content, without pretreatment it resists enzymatic hydrolysis, like most lignocellulosic materials. Wet oxidation (water, oxygen, mild alkali or acid, elevated temperature and pressure) was investigated to enhance the enzymatic digestibility of corn stover. Six different combinations of reaction temperature, time, and pH were applied. The best conditions (60g/L of corn stover, 195°C, 15 min, 12 bar O₂, 2 g/L of Na₂CO₃) increased the enzymatic conversion of corn stover four times, compared to untreated material. Under these conditions 60% of hemicellulose and 30% of lignin were solubilized, whereas 90% of cellulose remained in the solid fraction. After 24-h hydrolysis at 50°C using 25 filter paper units (FPU)/g of dry matter (DM) biomass, the achieved conversion of cellulose to glucose was about 85%. Decreasing the hydrolysis temperature to 40°C increased hydrolysis time from 24 to 72 h. Decreasing the enzyme loading to 5 FPU/g of DM biomass slightly decreased the enzymatic conversion from 83.4 to 71%. Thus, enzyme loading can be reduced without significantly affecting the efficiency of hydrolysis, an important economical aspect.