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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
吸水膨胀型膨润土/交联聚丙烯酰胺颗粒堵剂 总被引:9,自引:0,他引:9
使丙烯酰胺、少量N,N-亚甲基双丙烯酰胺在钙膨润土存在下进行水溶液引发接枝共聚合,聚合产物经造粒、粉碎、筛分,得到粒径0.5~1.0mm的颗粒堵剂。根据颗粒堵剂吸水量大小确定丙烯酰胺与膨润土最佳质量比为7:1,引发剂最佳用量为500g/t,交联剂最佳用量为300g/t,吸水量与这3个参数之间的关系曲线都经过最大值,颗粒堵剂在去离子水中的吸水量为560~650mL/g。该堵剂已大规模生产,在胜利、中原油田许多采油厂已用于调剖、堵水和调驱施工,在青海、江苏、大港、冀东等油田也已开始使用。在胜利东辛采油厂的一个井组,连续3个月在3口井注入该堵剂共27t,使井口压力上升3MPa,产油量大幅度增加。表l参l。 相似文献
73.
Herman Keith C.; Ostrander Rick; Walkup John T.; Silva Susan G.; March John S. 《Canadian Metallurgical Quarterly》2007,75(5):716
A latent profile analysis was conducted on the co-occurring symptoms of 423 adolescents diagnosed with major depressive disorder as part of the Treatment for Adolescents with Depression Study (TADS), a multisite, randomized treatment trial. The participants had a mean (SD) age of 14.6 (1.5) years; of the sample, 45.6% was male and 73.8% was white. Scores on the primary subscales of Conners' Parent Rating Scale-Revised were used as indicators in the analysis. Five classes of symptoms best described the clinical presentation of adolescents enrolled in the TADS. Of the adolescents in the sample, 80% were assigned to classes with clinically significant elevations on 1 or more subscales of the Children's Depression Rating Scale-Revised. The 5 classes met empirical criteria for distinctiveness and were validated against clinical diagnoses, child-rated symptoms, and clinician-rated functional impairment. The findings are consistent with prior studies that showed a high rate of co-occurring symptoms among depressed adolescents. The discussion focuses on understanding subtypes and comorbidity in adolescent depression as well as the implications for treatment and for prevention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
The complete verification of the timing properties of a large critical system cannot be undertaken in a single step or with
a single method. In this paper we present a process that links together a number of techniques and approaches that cover all
stages of development from requirements analysis to code testing. The key elements of the process are: a constrained form
of timed automata that uses delay and deadline to define temporal behaviour, notions of rely and guarantee to cover temporal dependencies, model checking for design verification, SPARK and Ravenscar restrictions for programming,
and scheduling and response time analysis for asserting implementation compliance. Extended examples of the use of the process
are given. 相似文献
75.
以实际工程为背景,采用门式刚架轻型房屋钢结构设计规程,对带吊车门式刚架、吊车梁、抗风柱及基础的受力特点、设计方法进行分析,解决了设计中所遇到的问题。 相似文献
76.
随着单井蒸汽吞吐周期的增加,加剧了油层纵向和平面上的非均质性。汽驱井组油层存在高渗透带或孔道,注入蒸汽上升,从稠油顶部跨越,会出现越顶现象,造成提早汽窜,注蒸汽驱的波及效率进一步降低。针对此问题,开发了稠油注汽井用高温调剖封窜剂。室内研究结果表明,研制的高温调副封窜剂HD、HT具有较好的高温成胶性能和强度。现场应用孤东油田的9口井,有效8口,有效率88.9%,累计增油726.8t。 相似文献
77.
John Hemp 《Flow Measurement and Instrumentation》1994,5(4):247-253
In this paper a fuller and clear derivation of the weight vector theory of Coriolis mass flowmeters is given indicating its potential for the prediction of velocity profile effects in both the traditional kind of meter (vibrating tube) and the compact kind (vibrating element inside a duct). 相似文献
78.
The architects and builders in the past lacked our knowledge concerning fluid dynamics, but they exhibited a deep rooted ability to observe and reflect - thus, different cultures have developed by trial and error. The authors have produced a stimulating analysis which couples the science of fluid dynamics and a sensitive understanding of past cultures. The paper is recommended reading. 相似文献
79.
Merahi Ali Ahmed B. Mohammed F. Jean M. 《AEUE-International Journal of Electronics and Communications》2005,59(6):359-361
A refined study of multi-carrier code division multiple access transmission over a Nakagami fading channel is proposed. The channel power is modeled with an exponential power profile rather than the uniform profile prevalent in other papers. An expression for the bit error rate (BER) is then derived. Numerical results show that MC-CDMA performances depend on the power dispersion of interferers around the desired user power. 相似文献
80.
A. K. Hansen A. C. Boxer J. L. Ellsworth D. T. Garnier I. Karim J. Kesner M. E. Mauel E. E. Ortiz 《Journal of Fusion Energy》2007,26(1-2):57-60
Plasmas in the Levitated Dipole Experiment (LDX) are formed and sustained currently via two electron cyclotron resonance heating
(ECRH) sources: 2.5 kW at 2.45 GHz and 2.5 kW at 6.4 GHz. An important topic being investigated is how varying the ECRH affects
the confinement and stability of the plasma. We report the results of using different operational combinations of our RF sources,
such as varying the power composition, changing the power levels, and sequencing of the onset time. 相似文献