A numerical investigation of 3-D small-scale yielding fatigue crack growth

The 3-D small-scale yielding (SSY) model provides a computational framework to study fatigue crack growth in thin, metallic components (and test specimens) containing an initially sharp, straight-through crack. This work describes a finite element study of plasticity-induced crack closure in the 3-D SSY model under mode I, constant amplitude cyclic loading with a ratio R=K_min/K_max. A purely kinematic hardening model with constant modulus represents the material constitutive behavior. This paper first addresses key computational issues and proposes modeling guidelines leading to 3-D numerical results for fatigue crack growth in SSY that exhibit convergence with mesh refinement. Specifically, computed crack opening loads show an independence of finite element mesh refinement when (a) the plastic zone at peak load encloses more than 10 eight-noded brick elements (b) the reverse plastic zone encloses at least two elements, and (c) the half-thickness has at least five element layers. The paper also describes stress and deformation fields at the crack front for a growing fatigue crack and provides an understanding of localized 3-D effects on the normalized remote opening load value K_op/K_max. In addition, the computational studies demonstrate that the similarity scaling relationship established for R=0 [Roychowdhury and Dodds, Fatigue Fract. Engng. Mater. Struct. (accepted for publication)] also holds for the non-zero ratio R=0.1--a value commonly adopted in experimental programs. In particular, K_op/K_max, at each location along the crack front remains unchanged when the peak load (K_max), thickness (B) and material flow stress (σ₀) all vary to maintain a fixed value of .     

Building Curves with Arbitrary Small MOV Degree over Finite Prime Fields

We present a fast algorithm for building ordinary elliptic curves over finite prime fields having arbitrary small MOV degree. The elliptic curves are obtained using complex multiplication by any desired discriminant.     

基于向量场正规形的电力系统动态分析

随着现代电力系统的日益复杂和非线性程度的增加,电力系统在运行点附近表现出了复杂的动态行为,采用传统小扰动法难以凑效,文中将向量场正规形方法应用于电力系统奇异摄动模型,通过分析电力系统基本响应模式间的非线性相关作用来认识和理解系统的动态特性,深化了线性化分析中的特征分析理论,为分析强非线性下系统的稳定性及非线性动态特性提供了一条新的有效途径。对一简单的电力系统进行分析,得到了一些有益的结论。     

破乳菌种TR-1的筛选与破乳性能实验研究

从克拉玛依受石油污染的土壤中筛选出一株原油破乳菌TR-1。介绍了筛选方法。筛选时使用含水原油静置分层产生的油、水相等体积混合制备的W/O乳状液,35℃、50天自发脱水率<5%;细菌全培养液加量为100mL/L。培养温度35℃,最佳培养pH值7~9,时间5~6天。所得培养液含菌1.1×109个/mL,含干菌体~8.68g/L,35℃、150 min脱水率>90%;2.0 g/L干菌体水悬液相同加量时脱水率为80.0%;现用聚醚破乳剂加量100mg/L时脱水率~55%。TR-1菌主要以菌细胞破乳,所产生物表面活性剂也起一定破乳作用。TR-1菌破乳性能稳定,第1、5、25代全培养液的脱水率分别为88.3%、91.7%、80.0%。2.0 g/L干菌体水悬液用于克拉玛依采油一厂、二厂含水50.0%、66.7%的稀油破乳(50℃),加量100 mL/L时脱水率为66.7%、88.2%,高于现用聚醚破乳剂的脱水率,但对二、三区混合稠油无破乳效果。50℃、150 min自发脱水率为16.5%的含水50.0%的稀油,加入5、204、0 mg/L聚合物PAM后自发脱水率变为2.0%、4.0%、43.9%,再加入100 mL/L干菌体水悬液时脱水率分别为96.5%、80.5%、76.5%,均高于加入100 mg/L化学破乳剂时的相应值。图3表4参6。     

聚合物/羧基甜菜碱二元复合体系驱替水驱后残余油的机理

实验研究在30℃下进行。实验聚表二元复合体系为1.0 g/L HPAM、2.0 g/L羧基甜菜碱在矿化度3.7 g/L的模拟大庆油田采出水中的溶液,与模拟大庆油(黏度10 mPa.s)间的界面张力为5.8×10-3mN/m,1-1000 s-1范围的表观黏度与1.0 g/L HPAM溶液十分接近。在玻璃刻蚀大庆油藏仿真均质微观模型上,水驱20 PV的采收率为55.795%,注入20 PV二元体系使采收率增加39.724%;在二元复合体系驱替过程中,注入、采出口之间主流区域内的水驱后残余油在二元复合体系作用下发生变形,伸长并形成油丝,主要以油丝的形式被驱出;过渡区和边角区的残余油则主要以W/O乳状液的形式被驱出。W/O乳状液中的乳化水滴通过圈闭、Y型孔道挤压及水滴变形、断裂这3种方式形成并汇集为比较连续的W/O乳状液流,二元复合体系以W/O乳状液的形式由主流区扩展到两侧的过渡区,再进入边角区,启动死油区的残余油,从而扩大了波及体积,提高了驱油效率。图5参11。     

Cone-Shaped Hypolimnion and Local Reactor as Outstanding Features in Eutrophication of Lake Maracaibo

Between 1974 and 1979 a large-scale research program to identify and evaluate the pollution problems in tropical Lake Maracaibo was undertaken. Two unique limnological features investigated during this program were a cone-shaped hypolimnion in the center of the lake and an area of unusually high biologic activity within the northeastern coastal area. With respect to the cone-shaped hypolimnion, epilimnetic water moves counterclockwise around the cone like a large-scale vortex. Anoxic conditions, high salinity, and exceedingly high N and P concentrations are found in the hypolimnetic cone. It functions as an internal source of nutrients throughout the year at tropical temperatures. The northeastern coastal area, where massive blooms of algae are an established feature, is likened to a biological reactor. It is characterized as a relatively low energy zone in relation to the horizontal movement of the water in the rest of the lake.     

含碱和表面活性剂的HPAM/Cr+3弱凝胶调驱剂的研制

从3种有机酸铬中选择一种烯基多元羧酸铬为交联剂,用于交联大庆油田三元复合驱油体系,制备弱凝胶调驱剂。以阻力系数(RF)特别是残余阻力系数(RRF)作为性能参数筛选调驱剂各组分的用量,得到了基本配方(以g/L计)如下:HPAM(M=1.2×107,HD=25%)0.9 交联剂(有效成分50%)0.18 表面活性剂(ORS41)3 碱(NaOH)8 稳定剂0.2,用大庆某三元复合驱试验区污水(矿化度3824mg/L)配液,其RRF值为清水(矿化度890mg/L)弱凝胶的～45%。基本配方弱凝胶45℃下7天时粘度18.3mPa·s,RF值81.2,RRF值8.2,随时间而减小,120天时分别为12.8mPa·s,66.1和7.3;油水界面张力仍在10-3mN/m数量级,只比常规三元复合体系略高;体系中表面活性剂在油砂上的静态吸附量为0.495mg/g油砂,比常规三元复合体系的相应值(0.462mg/g油砂)略高;岩心流动实验中测得的表面活性剂滞留量(0.067和0.070mg/g岩心)也高于常规三元复合体系的相应值(0.054和0.059mg/g岩心)。若用Na2CO3代替NaOH,则碱剂浓度可由6～8g/L提高到8～10g/L。表8参4。     

Near-infrared to visible photon upconversion in Mn and Yb containing materials

Near-infrared (NIR) laser excitation into the Yb^{3+ 2}F_7/2→²F_5/2 absorption transition around 10,200 cm⁻¹ at 12 K leads to red and green upconversion emission in MnCl₂:Yb³⁺ and Zn₂SiO₄:Yb³⁺; Mn²⁺, respectively. The photon upconversion (UC) emission is centered around 15,240 cm⁻¹ for MnCl₂:Yb³⁺ and around 19,050 cm⁻¹ for Zn₂SiO₄:Yb³⁺; Mn²⁺ and is ascribed to the Mn^{2+ 4}T₁→⁶A₁ transition in both compounds. The shift of the Mn²⁺ emission energy is due to the different coordination and ligand strength. Pulsed measurements indicate a sequence of ground-state absorption (GSA) and excited-state absorption (ESA) steps for the upconversion process. We conclude that the UC process in both compounds occurs by an exchange mechanism involving Yb³⁺ and Mn²⁺ ions. Zn₂SiO₄:Yb³⁺; Mn²⁺ is the first example of a Yb³⁺–Mn²⁺ upconversion system to show visible (VIS) by eye Mn²⁺ UC emission at room temperature.     

离子微孔膜的研究及应用

叙述了离子孔膜的物理化学特性及其应用发展状况，并结合我院的实际情况综述了离子微孔膜的制备工艺过程，离子微孔膜在重离子成像微孔防伪标识和药液过滤器方面的应用，以及离子微孔膜的研究开发状况。     

The relationship between psychology and cognate fields.

"The listing in the university catalogues which were examined indicated that psychology was most often listed as a social science and next most frequently listed as a biological science. In several universities the psychology department was classified as both a biological and social science. In terms of specific departmental recommendations of courses, it was indicated that there was an interdependence between psychology and the various social sciences. Psychology was found to depend much more heavily on the biological sciences, physical sciences, and mathematics than those areas depended upon psychology. On the other hand, the social sciences, humanities, and service areas were found to depend much more heavily on psychology than the psychology departments depended upon them." (PsycINFO Database Record (c) 2010 APA, all rights reserved)