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排序方式: 共有369条查询结果,搜索用时 116 毫秒
231.
塔河油田奥陶系碳酸盐岩油藏经多轮次周期注水后,井间形成优势水流通道,注入水突破现象日益突出,注水效率逐年降低。针对注水突破技术难题,高温(140 ℃)高矿化度(24×104 mg/L)作业环境,开展调剖体系室内实验研究,优选增稠药剂、分选地表砂,并建立调剖模型、耐冲刷定性分析模型,形成增稠液携砂调剖体系及“细目陶粒+ 塔河砂+ 覆膜砂”三段塞调剖工艺技术。增稠液携砂调剖工艺技术现场试验取得了较好的调剖效果,对今后塔河油田碳酸盐岩调剖有一定的指导意义。 相似文献
232.
Drago Špoljarić 《统计学通讯:理论与方法》2017,46(17):8748-8759
An important aspect in the analysis of long DNA sequences is to identify whether palindromes are over- or under-represented. The essential step in that direction is the analysis of the limiting distribution of the number of clumps of palindromes where clump is defined as the overlapping occurrence of palindromes. Using the Chen–Stein method, it is shown in this paper that the limiting distribution, under suitable conditions and a type of heterogeneous sequence, is the Poisson distribution. Moreover, error bounds and the rate of convergence are derived in terms of total variation distance between two probability distributions. 相似文献
233.
Ziqi Chen Man‐Lai Tang Wei Gao Ning‐Zhong Shi 《Scandinavian Journal of Statistics》2014,41(3):725-741
Motivated by an entropy inequality, we propose for the first time a penalized profile likelihood method for simultaneously selecting significant variables and estimating unknown coefficients in multiple linear regression models in this article. The new method is robust to outliers or errors with heavy tails and works well even for error with infinite variance. Our proposed approach outperforms the adaptive lasso in both theory and practice. It is observed from the simulation studies that (i) the new approach possesses higher probability of correctly selecting the exact model than the least absolute deviation lasso and the adaptively penalized composite quantile regression approach and (ii) exact model selection via our proposed approach is robust regardless of the error distribution. An application to a real dataset is also provided. 相似文献
234.
Since publication use of the WHOQOL-Brèf has rapidly risen. However, as yet no population norms have been published as a reference
point against which researchers can interpret their findings. This study provides preliminary population norms for this purpose.
Randomly sampled community residents from two studies were pooled and used to examine the properties of the WHOQOL-Brèf by
age group, gender and health status. The results showed that general norms for the WHOQOL-Brèf domains were 73.5 (SD=18.1)
for the Physical health domain, 70.6 (14.0) for Psychological wellbeing, 71.5 (18.2) for Social relationships and 75.1 (13.0)
for the Environment domain. In general scores declined slightly by age group. For females scores were stable across the lifespan
with an accelerated decline after the age of 60 years. Males exhibited a more consistent and even decline across the lifespan.
There were significant differences in WHOQOL-Brèf scores when reported by health status, with those in poor health obtaining
scores that were up to 50% lower than those in excellent health. Effect sizes between different health status levels are reported.
These preliminary norms and effect sizes may be used as reference points for interpreting WHOQOL-Brèf scores. They provide
additional information to the numerous national studies already reporting on the validity of the WHOQOL-Brèf. 相似文献
235.
236.
黄利华 《广州市财贸管理干部学院学报》2011,(4):65-68
琼脂具有非常强的凝胶特性。文章以研究琼脂凝胶的流变学特性为切入点,测量凝胶机械模量的动态变化,表征琼脂凝胶形成的过程。利用质构仪测量琼脂凝胶,以凝胶硬度为指标,对琼脂浓度、离子强度、pH值进行单因素试验,优选各因素的较好范围,并通过正交试验得到制备琼脂凝胶的最适条件:琼脂浓度2.5%,离子强度0.8M,pH值为7。 相似文献
237.
Richard J. Roberts 《Accountability in research》2013,20(1-3):45-50
Science is one of the most exciting frontiers of human endeavor and yet is often poorly understood. In this article I argue that improved education of both our children and our adults is key for the future. It is incumbent on all scientists to help educate our citizenry. In addition to the traditional methods we should make better use of television for this purpose. I strongly advocate permeating regular news programs with science news and education. 相似文献
238.
This article develops a computationally and analytically convenient form of the profile likelihood method for obtaining one-sided confidence limits on scalar-valued functions phi = phi(psi) of the parameters psi in a multiparameter statistical model. We refer to this formulation as the likelihood contour method (LCM). In general, the LCM procedure requires iterative solution of a system of nonlinear equations, and good starting values are critical because the equations have at least two solutions corresponding to the upper and lower confidence limits. We replace the LCM equations by the lowest order terms in their asymptotic expansions. The resulting equations can be solved explicitly and have exactly two solutions that are used as starting values for obtaining the respective confidence limits from the LCM equations. This article also addresses the problem of obtaining upper confidence limits for the risk function in a dose-response model in which responses are normally distributed. Because of normality, considerable analytic simplification is possible and solution of the LCM equations reduces to an easy one-dimensional root-finding problem. Simulation is used to study the small-sample coverage of the resulting confidence limits. 相似文献
239.
对仿拟修辞格之本体和仿体的表现形式的研究与探讨显示,仿拟这一修辞格既存在于语法层面(词、短语和句子,语素除外),也存在于语体层面(公文体、政论体、文艺体和广告体,科技体中少见).综而观之,本体和仿体的相互关系表现为本体的先成性、单一性和定型性与仿体的临时性、多元性和拓展性. 相似文献
240.
无线电摄像机是一种新型成像雷达,利用它可以获得目标的二维(距离-方位)微波图像[1]。通过目标二维(距离-方位)像与目标一维距离像的分析对比,指出了目标二维像应用于目标识别领域的优势。针对三种目标分别模拟了其相应的二维像与一维像,仿真识别结果验证了分析的正确性 相似文献