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排序方式: 共有471条查询结果,搜索用时 78 毫秒
1.
套管侧钻分支井钻井工程设计及应用原则 总被引:8,自引:3,他引:5
利用老井开窗侧钻分支井,可以提高原油采收率,增加产能和降低成本。对与分支井相关的分式设计。轨迹优化设计,钻柱设计,斜向器开窗方位的优化。开窗技术。轨迹控制应用等方面的主要原则进行了阐述。对进一步推广应用分支井技术,提高我国分支井钻井技术水平有一定的推动作用。 相似文献
2.
A new method using high‐intensity ultrasonic waves, instead of peroxide‐aided reactive extrusion, was applied to modify a linear polypropylene into a branched structure. The ultrasonic waves induced chain scission and created reactive macromolecules of polypropylene successfully in the melt state without any peroxide. To enhance and control the recombination reaction during sonication, a multifunctional agent and an antioxidant were used. The rheological property measurements clearly confirmed that the modified polypropylene had a nonlinear branched structure. It showed shear‐thinning behaviors in its viscosities at low frequencies, high elastic behaviors in Cole–Cole plots, and a high rheological polydispersity index in comparison with a linear polypropylene. The degradation or recombination of polypropylene was adequately controlled by an antioxidant, which stabilized the structure during sonication. Also, the use of an antioxidant was quite effective in improving the extrusion processability by delaying the instability of the extrudate to a higher shear rate. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006 相似文献
3.
Branched polyacrylonitrile (PAN) was prepared through a self‐condensing vinyl copolymerization of acrylonitrile and 2‐(2‐bromopropionyloxy)ethyl acrylate (BPEA). The branched architecture of the product was confirmed by NMR spectra and the average degree of branching (DB ) was estimated. Through a comparison of the intrinsic viscosity of the product with that of its linear analogue, the contraction factor g′ was calculated. It was found that the viscosity of the branched PAN was obviously lower that that of linear PAN. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
4.
5.
Viscosity rise and extent of reaction were followed during the step growth polymerization of linear and branched urethanes in bulk and in solution. Results indicate that intra-molecular reaction may exist in both linear and branched systems. Adding solvent increases the extent of intra-molecular reaction. The system viscosity was found to correlate with CgMw, where C is polymer concentration, g is the ratio of branched to linear polymer radii of gyration, and Mw is the weight-average molecular weight. 相似文献
6.
Won Seok Lyoo Chan Sik Park Joon Ho Kim Han Do Ghim Ji Youl Lee Jinwon Lee Chul Joo Lee 《应用聚合物科学杂志》2003,88(3):832-839
Vinyl pivalate (VPi) was suspension‐polymerized to synthesize high molecular weight (HMW) poly(vinyl pivalate) (PVPi) with a high conversion above 95% for a precursor of syndiotacticity‐rich HMW poly(vinyl alcohol) (PVA). Also, the effects of the polymerization conditions on the conversion, molecular weight, and degree of branching (DB) of PVPi and PVA prepared by the saponification of PVPi were investigated. Bulk polymerization was slightly superior to suspension polymerization in increasing the molecular weight of PVA. On the other hand, the latter was absolutely superior to the former in increasing the conversion of the polymer, indicating that the suspension polymerization rate of VPi was faster than that of the bulk one. These effects could be explained by a kinetic order of a 2,2′‐azobis(2,4‐dimethylvaleronitrile) concentration calculated by the initial rate method. Suspension polymerization of VPi at 55°C by controlling various polymerization factors proved to be successful in preparing PVA of HMW [number‐average degree of polymerization (Pn): 8200–10,500], high syndiotactic diad content (58%), and very high yield (ultimate conversion of VPi into PVPi: 94–98%). In the case of the bulk polymerization of VPi at the same conditions, the maximum Pn and conversion of 10,700–11,800 and 32–43% were obtained, respectively. The DB was lower and the Pn was higher with PVA prepared from PVPi polymerized at lower initiator concentrations. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 832–839, 2003 相似文献
7.
Jiefeng Hai Yuanxia Song Ling Li Xin Liu Xiaoyu Shi Zhuoyue Huang Guangming Qian Zhenhuan Lu Jiangsheng Yu Huawei Hu Shangshang Chen 《Advanced functional materials》2023,33(19):2213429
The elaborate balance between the open-circuit voltage (VOC) and the short-circuit current density (JSC) is critical to ensure efficient organic solar cells (OSCs). Herein, the chalcogen containing branched chain engineering is employed to address this dilemma. Three novel nonfullerene acceptors (NFAs), named BTP-2O , BTP-O-S , and BTP-2S , featuring different peripheral chalcogen containing branched chains are synthesized. Compared with symmetric BTP-2O and BTP-2S grafting two alkoxy or alkylthio branched chains, the asymmetric BTP-O-S grafting one alkoxy and one alkylthio branched chains shows mediate absorption range, applicable miscibility, and favorable crystallinity. Benefiting from the enhanced π–π stacking and charge transport, an optimal power conversion efficiency (PCE) of 17.3% is obtained for the PM6: BTP-O-S -based devices, with a good balance between VOC (0.912 V) and JSC (24.5 mA cm−2), and a high fill factor (FF) of 0.775, which is much higher than those of BTP-2O (16.1%) and BTP-2S -based (16.4%) devices. Such a result represents one of the highest efficiencies among the binary OSCs with VOC surpassing 0.9 V. Moreover, the BTP-O-S -based devices fabricated by using green solvent yield a satisfactory PCE of 17.1%. This work highlights the synergistic effect of alkoxy and alkylthio branched chains for high-performance OSCs by alleviating voltage loss and enhancing FF. 相似文献
8.
Synthesis of Branched DNA Scaffolded Super‐Nanoclusters with Enhanced Antibacterial Performance 下载免费PDF全文
Lu Yang Chi Yao Feng Li Yuhang Dong Zhikun Zhang Dayong Yang 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(16)
Metal nanoclusters (NCs) possess unique optical properties, and exhibit a wide variety of potential applications. DNA with robust molecular programmability is demonstrated as an ideal scaffold to regulate the formation of NCs, offering a rational approach to precisely tune the spatial structures of NCs. Herein, the first use of branched DNA as scaffold to regulate the formation of silver nanoclusters (super‐AgNC) is reported, in which the spatial structures are precisely designed and constructed. Super‐AgNC with tunable shapes and arm‐lengths including Y‐, X‐, and (Y–X)‐ shaped super‐AgNC is achieved. The molecular structures and optical properties of super‐AgNCs are systemically studied. As a proof of application, remarkably, super‐AgNCs exhibit superior antibacterial performance. In addition, super‐AgNCs show excellent biocompatibility with three types of tissue cells including 293T (human embryonic kidney cells), SMCs (vascular smooth muscle cells), and GLC‐82 (lung adenocarcinoma cells). These performances enable the super‐AgNCs adaptable in a variety of applications such as biosensing, bioimaging, and antibacterial agents. 相似文献
9.
利用“细胞CT”——激光扫描共聚焦显微镜可以获得肿瘤细胞三维断层图像,实现肿瘤细胞三维可视化,具有重要临床及科研意义。本文提出了一种针对细胞断层图像轮廓的三维极坐标插值方法,以图形形态学中心为极坐标原点,将轮廓点转换为极坐标表示。按极角采样获得离散轮廓点数据,综合多层轮廓信息,依照表面轮廓变化趋势,进行均匀三次B样条拟合完成插值。并针对肿瘤细胞核常见的分支核结构,利用曲率角点检测和数学形态学相结合的方法实现轮廓分割,并采用基于阈值半径的轮廓匹配方法实现分支轮廓对应,继而实现细胞分支核插值。结果显示,本方法可实现细胞及细胞核的三维插值,插值后轮廓表面三维重建表现出良好的曲面光滑性和连续性。极坐标插值数据可为细胞三维形态结构测量提供便利。 相似文献
10.
将分支前馈神经网络(BFNN)运用于数字字符的模式识别问题中,其某些性能优于标准反向传播(BP)网络。BFNN的隐层神经元与输出神经元之间为分组对应关系,采用的学习算法与标准BP算法类似。BFNN可以根据样本的可分性构建最适宜的网络结构。在对大规模、分类复杂的样本进行识别时,性能优于标准BP网络。 相似文献