Improvement of the second order approximation of the smoothed particle hydrodynamics

The smoothed particle hydrodynamics (SPH), as a fully Lagrangian particle method, has been successfully applied to astrophysical problems and extended to elastic dynamics and computational fluid dynamics.High order derivatives have to be approximated when elastic dynamics problems are modeled. However, the approximation errors in SPH could lead to computational failure in the case that the order of derivative is high.A novel method was proposed in order to improve the accuracy of SPH method, which shows the relationship between the selected functions and their SPH approximations. The entire involved system was represented by a finite number of particles that carry individual mass and occupy individual space, and the integral interpolation was approximated by a summation interpolation. In addition, error comparison was made between SPH method with and without the present improvement.     

铁路轨检车轴箱振动加速度消趋方法的比较

振动测量数据中往往包含了趋势项,这些趋势项对数据的分析会产生很大的影响,尤其在积分过程中,这种影响会进一步放大,所以消除趋势项是数据分析的基本前提。对包含在轴箱加速度中的趋势项进行消除,并进行双积分以达到与轨面高低不平顺进行比较的目的,采用了三种消趋方法进行对比分析的方式,三种消除趋势项的方法（多项式拟合消趋,滤波消趋及小波消趋）对实测数据的分析结果为：多项式拟合消趋不适于轴箱加速度的积分分析,而滤波消趋与小波消趋能适于这种分析,进一步,从波形包络来看,小波消趋与原波形最接近。最后提出了适合于轴箱加速度分析的消趋方法及其相关参数值。     

Apoptin原核表达载体的构建及在大肠杆菌中的表达

目的构建Apoptin的原核表达载体,并制备抗原物质Apoptin融合蛋白。方法在获得Apoptin融合基因的基础上,成功构建了Apoptin的高效原核表达载体pET-28a( )-Apoptin,将该质粒转化至大肠杆菌E.coliBL21(DE3)受体菌中,以IPTG对其进行诱导表达,聚丙烯酰胺凝胶电泳分析目的蛋白。结果转化有Apoptin的原核表达载体pET-28a( )-Apoptin的大肠杆菌E.coliBL21(DE3)经IPTG诱导后,经SDS-PAGE分析,在相对分子质量约17 000的位置出现目的蛋白条带,大小与Apoptin融合蛋白一致。结论Apoptin原核表达载体pET-28a( )-Apoptin能够表达出Apoptin融合蛋白,为进一步的Apoptin研究和制备Apoptin抗体奠定了基础。     

幽门螺杆菌尿素通道蛋白基因UreI载体的构建、融合表达及纯化

目的构建幽门螺杆菌(H.pylori,Hp)尿素通道蛋白基因UreI的融合表达载体,并在E.coliBL21中表达,为进一步研究UreI的功能奠定基础。方法利用分子克隆技术以Hp DNA染色体为模板,扩增Hp UreI基因片段,将目的基因UreI与载体pET32a( )分别经kpnⅠ和HindⅢ双酶切,纯化,连接。筛选阳性重组载体,转化大肠杆菌BL21,以IPTG诱导表达pET32a( )/UreI融合蛋白。表达产物经Ni-NTA琼脂糖树脂纯化后,用SDS-PAGE及Western blot分析。结果经酶切、测序分析表明,插入的基因片段为Hp UreI编码基因,由585 bp组成,与GenBank相应菌株HP AM417 609序列完全一致,无碱基突变。经SDS-PAGE分析显示重组质粒pET32a( )/UreI在原核细胞中得到了高效融合表达,其重组融合蛋白分子量为130 ku,经Ni-NTA琼脂糖树脂纯化后,其纯度达95%以上,Western blot分析显示,该重组融合蛋白可被6-His鼠抗单克隆抗体所识别,具有良好的反应原性。结论成功地克隆和构建了原核表达载体pET32a( )/UreI,并在原核细胞中得到了高效融合表达。     

WWOX蛋白在非小细胞肺癌中的表达及其临床意义

目的 探讨WWOX(WW domain-containing oxidoreductase)基因在非小细胞肺癌组织中的表达及其临床意义.方法 用免疫组化方法检测50例鳞癌、31例腺癌及20例癌旁正常组织中WWOX基因蛋白的表达,并分析其与各临床病理指标之间的相关性.结果 WWOX基因在72.8%的非小细胞肺癌中失表达或表达减少,而在相邻正常肺组织中有80.0%正常表达.WWOX基因的表达与组织类型、细胞分化程度密切相关(P<0.05),在鳞癌和低分化癌中WWOX基因失表达或表达减少.结论 WWOX蛋白在非小细胞肺癌组织中呈低表达,该蛋白表达的缺失可能在不同类型非小细胞肺癌的形成中发挥了不同的作用.     

高模量沥青混合料的动态模量试验研究

高模量沥青混合料是通过在基质沥青中添加调和硬组分从而提高其模量的。实验对混合料进行了配合比设计,并对其与其它几种混合料在不同温度、不同加载频率条件下进行动态模量对比试验研究。结果显示高模量沥青混合料可以在不降低混合料低温性能的同时,有效提高其高温稳定性,抑制和减少车辙的产生,从而保证道路的良好使用性能。     

三甲益肝冲剂对实验性肝纤维化大鼠脂质过氧化的影响

目的观察三甲益肝冲剂对大鼠肝纤维化的作用并探讨与抗脂质过氧化有关的作用机制。方法雄性SD大鼠40只,随机分为模型组、复方丹参组、三甲益肝冲剂组和正常组。以二甲基亚硝胺(DMN)腹腔注射诱导大鼠肝纤维化模型,复方丹参组造模同时给予复方丹参灌胃,三甲益肝冲剂组造模同时给予三甲益肝冲剂灌胃,共4周。4周后处死大鼠取肝组织标本,光镜观察肝组织的病理变化,放射免疫法测定血清丙二醛(MDA)含量和超氧化物歧化酶(SOD)活性。结果与正常组比较,模型组肝组织Masson染色胶原纤维面积和血清MDA含量显著增加(P<0.05),而血清SOD活性明显下降(P<0.05);与模型组比较,三甲益肝冲剂组Masson染色胶原纤维面积和血清MDA含量显著下降(P<0.05),而SOD活性明显升高(P<0.05)。Masson染色胶原纤维面积和血清MDA含量表达呈正相关关系(r=0.435,P<0.05),与SOD活性呈负相关关系(r=-0.358,P<0.05)。结论三甲益肝冲剂具有良好的抗实验性大鼠肝纤维化作用,其主要作用机制与抗肝脏脂质过氧化损伤有关。     

Experimental study on frictional and sealing performances of packing rings in an oil-free gas compressor

To enhance the reliability and to extend service life of packing rings, tribological and sealing performances are investigated based on the experimental results. Friction force, leakage rate and power consumption of three materials of pressure packing seals are measured in a refitted vertical gas compressor. The rings are made of common filled polytetrafluroethylene (Filled PTFE), PTFE reinforced with 30% mass fraction carbon fiber (30%CF+PTFE), and carbon-carbon composites infiltrated with PTFE (C/C+PTFE), respectively. It is found that packing rings will periodically vibrate with the periodic vibration of pressure packing after the travel direction of motion abruptly turns to the reverse direction. Furthermore, the amplitude of vibration slows down with the increasing crank angle. Approximate value of friction force is available by multiple-point fast Fourier transformation (FFT) employed to process the experimental results by reducing the impact of vibration to a great extent. Of three materials of rings employed in experiments, Filled PTFE presents minimal leakage rate accompanied with maximum power consumption. And 30%CF+PTFE exhibits minimum friction power and moderate leakage rate. As for C/C+PTFE, its high mechanical and thermal properties are favorable factors to enhance the ability of operating under high pressure and velocity and to improve the wear resistance. Unfortunately, this also leads to a large leakage rate. Comprehensive consideration should be taken into to evaluate the availability, reliability and service life for a type of packing ring under dry running conditions.     

关于城市轨道高架桥上安装护轮轨的建议

近年来国内各大城市竞相修建城市轨道交通系统,该系统环保、节能、快速的优势已经逐步显示出来,地铁、轻轨的发展规模必将日益扩大。如何提高城市轨道交通系统运营的安全性将是设计、建设和运营方最应该关心的问题。文章针对城市轨道交通高架桥上安装护轮轨方面提出了一些思考,可供今后城市轨道交通建设参考。