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951.
钻井过程中钻井液和固体碎屑混合而成的泥浆滤液渗透进入地层,对原始地层液体造成了不可避免的污染。取样探针的形状和布局对于在短时间内获取低污染样品有着十分重要的影响。采用合理简化,针对污染侵入和取样2个阶段建立了相关联的一系列模型,对不同类型探针和不同地层条件下的抽取过程用ECLIPSE软件进行数值模拟。通过对各个实例模拟结果的分析比较,为探针的设计和选择提供了依据。采用扩大探针口尺寸、在垂直方向上拉长探针、增加同一组件上的探针口数量和同一地层测试器(MDT)上携带更多探针组件的方式都增加了探针口面积,从而缩短达标作业时间。对于竖向与水平向渗透率比较小的地层环境,在探针口面积相同的情况下,竖直方向尺度较小的探针能更有效率地获得达标样品。 相似文献
952.
《Microelectronics Reliability》2015,55(1):180-191
Electroplated tin finishes are widely used in the electronics industry due to their excellent solderability, electrical conductivity and corrosion resistance. However, the spontaneous growth of tin whiskers during service can result in localised electrical shorting or other harmful effects. Until recently, the growth of tin whiskers was successfully mitigated by alloying the tin with lead. However, restriction in the use of lead in electronics as a result of EU legislation (RoHS) has led to renewed interest in finding a successful alternative mitigation strategy.Whisker formation has been investigated for a bright tin electrodeposit to determine whether whisker growth can, at least partially, be mitigated by control of electroplating parameters such as deposition current density and deposit thickness. The influence of substrate material and storage at 55 °C/85% humidity on whisker growth have also been investigated.Whisker growth studies indicate that deposition parameters have a significant effect on both whisker density and whisker morphology. As deposition current density is increased there is a reduction in whisker density and a transition towards the formation of large eruptions rather than potentially more harmful filament whiskers. Increasing the tin coating thickness also results in a reduction in whisker density. Results demonstrate that whisker growth is most prolific from tin deposits on brass, whilst that from tin deposits on rolled silver is greater than that observed for tin deposits on copper. 相似文献
953.
954.
随着数字技术的快速发展.复杂曲面形态已越来越多地应用于建筑设计中,数字化的生产方式与生产工具也在不断更新与升级.曲面的建构与优化过程对于复杂曲面建筑的实际建造效果有着举足轻重的意义,已成为建筑设计实践过程研究的重要方向。针对这一问题.本文首先归纳并论述复杂曲面建筑的发展历程.进而对建筑设计中复杂曲面的建构逻辑和方法进行研究和阐释.以此作为曲面优化设计的理论基础和依据.最后通过对实际案例的分析归纳,从曲面几何形态,结构形态、环境性能等方面提出深化设计阶段相应的曲面优化策略。 相似文献
955.
This paper investigates project changes and their relationships with stage iteration and multi-functional interaction. Changes often occur in a complex solution-based project, which makes the linear management model limited in its application. Complex project planning is based on assumptions about future events. Assumptions often fail and as a result the plans contain activities that are impossible or unnecessary to execute. The consistency of project planning needs to be restored and maintained by revising or redefining project activities. 相似文献
956.
957.
Aluminium phosphate (AlPO4) was characterized using X-ray diffractometry (XRD), Fourier Transform infrared (FTIR), point of zero charge (PZC) and dissolution studies. XRD showed the sample to be amorphous, FTIR confirmed the presence of OH groups on the surface and PZC was determined at pH 3.45. The dissolution study illustrated a decrease in dissolution with an increase in the pH. Potentiometric titration data were fit to the Gaines–Thomas equation, which showed that AlPO4 is a weakly acidic ion exchanger. Sorption studies were carried out at pH 4–6 and temperatures 293–323 K. The uptake of metal ions was observed to increase with an increase in the pH and temperature. The surface selectivity towards metal ions was found in the order Pb2+> Cu2+> Cd2+. Sorption data were fit to the new equation derived from the proposed mechanism for metal ion uptake. Various parameters such as stoichiometry of the surface H+ ion release, equilibrium constant, standard enthalpy, entropy and free energy changes were evaluated from the plots. The values of all these parameters were found to be closely related to the values reported in the literature. 相似文献
958.
为了增强运载辅酶Q10的纳米结构脂质载体(CoQ10-NLC)的透皮效果,采用促渗剂——壳聚糖季铵盐(QCS)对CoQ10-NLC进行了表面修饰,并结合QCS分子链的自聚集行为,明确了壳聚糖季铵盐修饰的包载辅酶Q10的纳米脂质体(QCS-CoQ10-NLC)的形成机制,得到了粒径在500 nm左右的脂质载体。进一步通过体外透皮实验,考察了QCS-CoQ10-NLC的透皮吸收效果。结果显示,经质量分数0.5%的QCS修饰后,脂质载体可将CoQ10在皮肤中的渗透总量由1.36μg/cm~2显著增加至5.14μg/cm~2。 相似文献
959.
《Ceramics International》2016,42(15):16744-16748
Manganese ferrite powder has been synthesized by ultrasonically assisted co-precipitation method using Fe(NO3)3·2H2O and Mn(NO3)2·H2O as precursors. The precipitate was washed and dried in oven at 80 °C for 2 h to obtain the initial MnFe2O4 powder (denoted by sample S1). Subsequently, other three samples (denoted by S2, S3 and S4) were prepared starting from the initial powder, which was subjected to heat treatment (for 2 h in air) at 400 °C (for sample S2), 700 °C (for sample S3) and 1000 °C (for sample S4). The structural and morphological analysis of samples has been studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). From the XRD analysis of samples one finds that the samples S1 and S2 consist of MnFe2O4 with cubic spinel structure, whilst the samples S3 and S4 consist of FeMnO3 with perovskite structure and Fe2O3; meaning that the thermal treatment of MnFe2O4 induces chemical and structural transformation. The complex impedance measurements, over the frequency range 20 Hz–2 MHz and magnetic measurements have confirmed the structural transformation in the samples subjected of heat treatment. 相似文献
960.
为实现特殊煤种的合理利用,选择树皮残植煤、角质残植煤、树脂残植煤、孢子残植煤和腐泥煤5种典型的特殊原生成因煤为研究对象,系统研究其性质特殊性,调查5种煤在我国的分布范围及资源量(储量),从能源和工艺2方面讨论了原生成因煤的开发利用价值,并从基础研究—勘查—综合利用等多途径,提出了特殊原生成因煤的合理利用建议。结果表明,特殊原生成因煤具有高挥发分、高氢含量和高H/C原子比等特点,且具有很好的生烃潜力。特殊原生成因煤分布在一定成煤期的部分煤层中。特殊原生成因煤的开发利用潜能很大。应加强基础研究,深入分析特殊原生成因煤的特殊性质,查清资源量,结合我国发展和需求,进行战略性的、持续性的综合利用研究。 相似文献