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Scheme for implementing quantum dense coding with four-particle decoherence-free states in an ion trap 被引量:3
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作者 郑小娟 曹帅 +1 位作者 方卯发 廖湘萍 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第2期431-434,共4页
This paper proposes an experimentally feasible scheme for implementing quantum dense coding of trapped-ion system in decoherence-free states. As the phase changes due to time evolution of components with different eig... This paper proposes an experimentally feasible scheme for implementing quantum dense coding of trapped-ion system in decoherence-free states. As the phase changes due to time evolution of components with different eigenenergies of quantum superposition are completely frozen, quantum dense coding based on this model would be perfect. The scheme is insensitive to heating of vibrational mode and Bell states can be exactly distinguished via detecting the ionic state. 展开更多
关键词 ENTANGLEMENT quantum dense coding trapped ions decoherence-free state
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Generation of steady four-atom decoherence-free states via quantum-jump-based feedback
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作者 吴奇成 计新 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第10期130-134,共5页
A scheme is presented tor generating steady tour-atom decoherence-tree states via tour atoms with the Raman level configuration interacting with a single-mode vacuum cavity field by using quantum-jump-based feedback. ... A scheme is presented tor generating steady tour-atom decoherence-tree states via tour atoms with the Raman level configuration interacting with a single-mode vacuum cavity field by using quantum-jump-based feedback. The scheme meets the condition of a strongly dissipative cavity easily and has a simplified feedback control. Although the spontaneous emission still plays a negative role in the proposed system, we can improve the feedback control to reduce its effect. 展开更多
关键词 Raman three-level atom large detuning four-atom decoherence-free state quantum-jump-basedfeedback
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Generation of arbitrary four-atom entangled decoherence-free states
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作者 计新 吕天全 张寿 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第12期5168-5172,共5页
This paper proposes a scheme to generate arbitrary four-atom entangled decoherence-free states by using simple linear optical elements, four one-sided cavities in which four atoms are confined respectively. By conveni... This paper proposes a scheme to generate arbitrary four-atom entangled decoherence-free states by using simple linear optical elements, four one-sided cavities in which four atoms are confined respectively. By conveniently tuning the titled angle of one half-wave plate, it can obtain arbitrary four-atom entangled decoherence-free states with a successful probability of 1 as long as there is no photon loss. 展开更多
关键词 one-sided cavity linear optical element four-atom entangled decoherence-free states
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The Prisoner of“Freedom”:Cultural Displacement of Santosh in Naipaul’s In a Free State
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作者 LONG Hang-hang 《Journal of Literature and Art Studies》 2023年第5期357-361,共5页
In a Free State is a post-colonial novel written by Naipaul.“One out of Many”is one of the stories in this novel to explore the freedom of the culturally rootless.The protagonist,Santosh,lives under the collision be... In a Free State is a post-colonial novel written by Naipaul.“One out of Many”is one of the stories in this novel to explore the freedom of the culturally rootless.The protagonist,Santosh,lives under the collision between the Indian culture and American culture.In the“crevice”of two different cultures,he is deeply involved in the tumultuous and painful process of cultural displacement.His behaviors in cultural displacement can be divided into three stages.Firstly,he has experienced a“cultural shock”after his arrival in Washington,D.C.as a new comer.Secondly,after being fully exposed to the host culture and American style,he has experienced assimilation and absorption to be like an American.Finally when he escapes from his employer and chooses his own way of living,he finds that he is not free at all because he is confronted with an awkward cultural dilemma:he can neither return to his past life;nor can he aspire to a better future.The anxiety about the dislocation causes misery for his fate.As a result,he becomes a prisoner in an unfamiliar culture,and his“freedom”can only be a rootless“freedom”. 展开更多
关键词 Santosh In a free state NAIPAUL cultural displacement freeDOM
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Funding Climate Change Haven Communities across the Political Spectrum: From Free-Market Capitalism to State-Directed Economies
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作者 Elizabeth C. Hirschman Emma Arnoux +3 位作者 Tze-Wei Huang Inez Latapia Hugo Rodriquez Carmen Vacas 《Journal of Environmental Protection》 2025年第2期180-210,共31页
We examine possible funding sources for constructing Climate Change Haven Communities on a global basis. Areas of the planet that have the potential to house persons migrating to “safe havens” in their own or other ... We examine possible funding sources for constructing Climate Change Haven Communities on a global basis. Areas of the planet that have the potential to house persons migrating to “safe havens” in their own or other countries will require the rapid construction of communities capable of supporting them, their families, businesses and farms. However, different political-economic conditions are found across the areas which can serve as locations for these Climate Change Haven Communities. We develop funding and construction strategies for the United States (free-market capitalism), France and Spain (European Union supported economies), and Taiwan region (state-directed economy). The proposals for the Taiwan region should also be applicable to the rest of China. 展开更多
关键词 Climate Change Haven Communities European Union France Climate Change Spain Climate Change Taiwan Region Climate Change United states Climate Change free-Market Capitalism Industrial Revolution state-Directed Economies
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Phase-sensitive fat suppression steady-state free procession sequence with phase correction 被引量:1
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作者 俎中良 周堃 +2 位作者 张仕刚 高篙 包尚联 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第1期328-334,共7页
Robust and fast fat suppression is a challenge in balanced steady-state free precession (SSFP) magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short ... Robust and fast fat suppression is a challenge in balanced steady-state free precession (SSFP) magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short scan time, phase errors, especially spatially-dependent phase shift, caused by a variety of factors may result in misplacement of fat and water voxels. In this paper, a novel phase correction algorithm was used to calibrate those phase errors during image reconstruction. This algorithm corrects phase by region growing, employing both the magnitude and the phase information of image pixels. Phantom and in vivo imagings were performed to validate the technique. As a result, excellent fat-suppressed images were acquired by using single-acquisition phase-sensitive SSFP with phase correction. 展开更多
关键词 steady-state free precession fat suppression phase-sensitive phase correction
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"But What's Nationality These Days?": Cosmopolitanism Old and New in the Prologue of In a Free State
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作者 Weiwei Xu 《Journal of Foreign Languages and Cultures》 2018年第1期78-84,共7页
关键词 In a free state NATIONALITY displacement COSMOPOLITANISM OPENNESS
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Quick and Simple Spectrophotometric Method of Identification of the Thermal State of Meat on the Basis of Composition and Content of Free Nucleotides
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作者 Magomed Dibirasulaev Georgy Belozerov +1 位作者 Leonid Arkhipov Lidia Stoyanova 《Food and Nutrition Sciences》 2018年第5期572-583,共12页
At present, there is no method for identifying meat frozen in a thermal state acceptable for production control. The role of free nucleotides in the processes of refrigeration and storage of meat, affecting the struct... At present, there is no method for identifying meat frozen in a thermal state acceptable for production control. The role of free nucleotides in the processes of refrigeration and storage of meat, affecting the structural and mechanical properties of muscle tissue, the formation of taste and its biological value is known. In this article we compared methods for identifying the thermal state of meat based on the determination of the composition and content of free nucleotides by high-performance liquid chromatography (HPLC) and spectrophotometry [SF]. High-purity reference substances were used: free nucleotides—ATP, ADP, AMP, IMP and nucleosides-inosine and hypoxanthine. It has been experimentally established that the characteristic peaks of the absorption spectra for extracts of free nucleotides of meat frozen depended from thermal state of meat. The content of ATP is 21.8 times higher in meat frozen in a fresh state, and the amount of IMF is 12.3 times lower than in meat frozen after cooling. The results of studies of meat frozen using the HPLC method and the developed SF method show the adequacy of the data obtained by both methods. SF-method based on the determination of the optical density of the extracts of free nucleotides is recommended to justify the choice of technological process meat defrost modes. 展开更多
关键词 Thermal state of MEAT free NUCLEOTIDES and NUCLEOSIDES HPLC and SPECTROPHOTOMETRIC Methods Defrost MODES
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基于终端滑模转速环的PMSM无模型预测电流控制
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作者 周晓华 张鹏阳 +1 位作者 王月武 吴雪颖 《组合机床与自动化加工技术》 北大核心 2026年第2期79-84,共6页
针对永磁同步电机无模型预测控制系统中传统的转速环PI控制存在超调量大,鲁棒性差等缺点,以及传统的模型预测电流控制(MPCC)对电机参数变化敏感,参数不匹配会导致性能下降的问题,提出一种基于扰动观测器和新型非奇异快速终端滑模转速环... 针对永磁同步电机无模型预测控制系统中传统的转速环PI控制存在超调量大,鲁棒性差等缺点,以及传统的模型预测电流控制(MPCC)对电机参数变化敏感,参数不匹配会导致性能下降的问题,提出一种基于扰动观测器和新型非奇异快速终端滑模转速环的PMSM无模型预测电流控制策略。该策略在转速控制环设计中采用非奇异快速终端滑模控制算法,通过构造新型的滑模趋近律实现有限时间收敛特性。同时构建扩张状态观测器(ESO)对负载转矩等集中扰动进行动态估计,并设计前馈补偿机制将观测值注入控制器,形成具有强抗扰能力的双闭环控制架构,以提高系统的鲁棒性。电流环采用基于超局部模型的无模型预测电流控制(MFPCC)。该方法不依赖于电机参数,进一步提高了系统的鲁棒性。仿真结果表明,与传统的MFPCC相比,所提控制方法在动态响应性能、鲁棒性和参数适应性方面具有显著优势,能够有效抑制超调和抖振,提高了系统的控制精度和稳定性。 展开更多
关键词 永磁同步电机 新型非奇异快速终端滑模控制 无模型预测 扩张状态观测器
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Relation between initial conditions and entanglement sudden death for two-qubit extended Werner-like states
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作者 杨百元 方卯发 黄江 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第8期264-268,共5页
In this paper, the dynamical behavior of entanglement of an uncoupled two-qubit system, which interacts with inde- pendent identical amplitude damping environments and is initially prepared in the extended Werner-like... In this paper, the dynamical behavior of entanglement of an uncoupled two-qubit system, which interacts with inde- pendent identical amplitude damping environments and is initially prepared in the extended Werner-like (EWL) states, is investigated. The results show that whether entanglement sudden death (ESD) of an EWL state will occur or not depends on initial purity and concurrence. The boundaries between ESD states and ESD-free states for two kinds of EWL states are found to be different. Furthermore, some regions are shown where ESD states can be transformed into ESD-free states by local unitary operations. 展开更多
关键词 entanglement sudden death extended Werner-like states ESD states ESD-free states
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增强3DBTFE在心肌炎中的诊断价值:基于路易斯湖标准的多序列对比研究
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作者 王丹 刘恺 +7 位作者 王佳丽 叶冲 陈丽惠 李爱媛 段洋 蒋强盛 徐凯 韩曙光 《中国医学计算机成像杂志》 北大核心 2026年第1期60-67,共8页
目的:探讨对比剂增强三维平衡稳态自由进动(3DBTFE)序列对心肌炎的诊断效能,并与2018版路易斯湖标准(LLC)推荐的T1 mapping、T2 mapping、心肌延迟强化(LGE)等序列对比。方法:前瞻性纳人2024年10月至2025年8月临床确诊的36例心肌炎患者... 目的:探讨对比剂增强三维平衡稳态自由进动(3DBTFE)序列对心肌炎的诊断效能,并与2018版路易斯湖标准(LLC)推荐的T1 mapping、T2 mapping、心肌延迟强化(LGE)等序列对比。方法:前瞻性纳人2024年10月至2025年8月临床确诊的36例心肌炎患者及36例健康志愿者匹配对照,所有患者均接受心脏磁共振成像(CMR)检查(含T2WI-STIR、T2mapping.T1 mapping、LGE及3D BTFE序列)。由2名高年资医师采用AHA17节段法测量心肌T1/T2/细胞外容积(ECV)值,定性评估各序列心肌水肿及强化情况。通过受试者工作特征(ROC)曲线比较各序列诊断效能[曲线下面积(AUC)、灵敏度、特异度],并分析同时存在水肿和强化患者的病变面积(最大及平均面积)及累及节段数差异。采用组内相关系数(ICC)评价两位医师评估结果的一致性。结果:相比于正常对照组,心肌炎组各CMR参数测量值均显著升高(P<0.001);对心肌炎病变的显示,3D BTFE的AUC值为0.915,T2WI-STIR、T1 mapping、T2mapping、ECV、LGE的AUC分别为0.835、0.869、0.855、0.795、0.849,3DBTFE诊断心肌炎的灵敏度(92%)、特异度(90.9%)均优于其他序列(均P<0.05)。对心肌炎病变区面积的显示上,3DBTFE序列最大面积[3.85(2.80,4.13)mm^(2)]、平均最大面积[3.30(2.40,3.60)mm^(2)]均高于LGE、T2WI-STIR序列,两两比较差异有统计学意义(均P<0.05)。3DBTFE在下壁、间隔、侧壁的检出率显著优于LGE和T2WI-STIR序列,差异有统计学意义(P<0.05)。结论:增强3DBTFE序列在心肌炎的诊断有较高的灵敏度,能够准确评估心肌炎病变的位置和范围,为临床提供更精准有价值的诊断信息。 展开更多
关键词 心肌炎 心脏磁共振成像 三维平衡稳态自由进动序列
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Avoidant Learning Ability in Free Flying Housefly (Aldrichina grahami) by Electric Shock 被引量:1
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作者 蒋苹 周东明 马原野 《Zoological Research》 CAS CSCD 北大核心 2009年第5期515-519,共5页
Previous studies have confirmed that both honeybee and Drosophila are capable of learning and memory. This study aimed to investigate whether the house fly (Aldrichina grahami), with strong instincts to adapt their ... Previous studies have confirmed that both honeybee and Drosophila are capable of learning and memory. This study aimed to investigate whether the house fly (Aldrichina grahami), with strong instincts to adapt their living environment, have the learning ability to associate odor stimulus to avoid electric shock in free flying state using a device developed by the authors. The result showed the learning ability ofA. grahami at the electric shock voltages of 5 V, 25 V and 45 V AC. When 60 V was used, the flies were frequently injured. Our results indicate that A. grahami is a good model to study the neural mechanism of learning and memory. The paradigm in this study has some advantages that can be used in future studies of free insects. 展开更多
关键词 Aldrichina grahami free flying state Avoidant learning Electro-shock Voltage threshold
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FREE模型在面向对象测试中的应用研究 被引量:1
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作者 马毅 李建华 《计算机应用研究》 CSCD 北大核心 2002年第9期88-90,共3页
在面向对象分析设计中 ,对象的行为通常与其状态紧密相关。因此 ,基于状态的测试成为面向对象软件中一个有效的测试方法。对FREE模型进行了研究 ,分析了该模型的优缺点及适用范围 ,并将其应用于面向对象软件测试中 ,为基于状态的测试提... 在面向对象分析设计中 ,对象的行为通常与其状态紧密相关。因此 ,基于状态的测试成为面向对象软件中一个有效的测试方法。对FREE模型进行了研究 ,分析了该模型的优缺点及适用范围 ,并将其应用于面向对象软件测试中 ,为基于状态的测试提供一个类行为的可测模型 ,有利于提高面向对象的测试质量。 展开更多
关键词 free模型 面向对象 测试 软件开发 软件方法
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基于终端滑模算法的无模型U控制系统设计
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作者 徐凤霞 曹文远 陆仲达 《高师理科学刊》 2026年第1期17-22,共6页
研究具有强不确定性的无模型连续系统的有限时间终端滑模控制器设计问题。为解决无模型U控制系统的建模问题,提出基于U控制框架的状态扩张观测器,旨在估计系统的状态和不确定项。同时,提出基于U模型的积分型非奇异终端滑模算法,实现了... 研究具有强不确定性的无模型连续系统的有限时间终端滑模控制器设计问题。为解决无模型U控制系统的建模问题,提出基于U控制框架的状态扩张观测器,旨在估计系统的状态和不确定项。同时,提出基于U模型的积分型非奇异终端滑模算法,实现了非线性系统的动态反演,保证系统在有限时间内收敛,改善非线性系统的响应速度,解决无模型U控制系统的快速收敛问题。仿真结果研究验证了控制系统的有效性。 展开更多
关键词 非线性U模型 有限时间 终端滑模控制 状态扩张观测器 无模型系统
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Structural,Dielectric and Complex Impedance Spectroscopy Studies of Lead Free Ca_(0.5+x)Nd_(0.5-x)(Ti_(0.5)Fe_(0.5))O_3 被引量:2
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作者 M.R.Shah A.K.M.Akther Hossain 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2013年第4期323-329,共7页
Structural and various electrical properties of polycrystalline Ca0.5+xNd0,5-x(Ti0.5Fe0.5)O3, prepared by standard solid state reaction technique, were studied. Formation of single phase orthorhombic structure of t... Structural and various electrical properties of polycrystalline Ca0.5+xNd0,5-x(Ti0.5Fe0.5)O3, prepared by standard solid state reaction technique, were studied. Formation of single phase orthorhombic structure of the compositions was confirmed by X-ray diffraction study. The composition dependence of lattice parameters, density and microstructural study show that they vary significantly with Ca content. The dielectric measurements were carried out at room temperature as function of frequency and composition. The experimental results reveal that the dielectric constant (ε′) increases with increasing Ca content. Similar behavior is observed for the dielectric loss (tanδ) and ac conductivity (σac). In complex impedance analysis it is observed that the real part (Z′) vs imaginary part (Z″) graph exhibits a tendency of formation of a single semicircular arc for each composition of samples. Different parameters were determined by fitting the experimental data in Cole-Cole empirical formula. A dominance of grain boundary resistance (Rgb) is observed. The Rgb decreases with increasing Ca content. The high ε′ observed in present samples are suitable for fabrication of devices. 展开更多
关键词 Crystal structure Dielectric properties Lead free PEROVSKITE Solid state reaction
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Comparative Study on Solid-State and Metastable Liquid-State Aging for SAC305/Cu Joints 被引量:2
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作者 Shuang Li Xiao-Wu Hu +2 位作者 Wei-Guo Zhang Yu-Long Li Xiong-Xin Jiang 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2019年第5期629-637,共9页
In order to study the in?uence of the physical state of solder on the interfacial reaction of dip-soldered Sn-3.0 Ag-0.5 Cu/Cu system, two kinds of experiments were designed, including:(1) solid-state aging between th... In order to study the in?uence of the physical state of solder on the interfacial reaction of dip-soldered Sn-3.0 Ag-0.5 Cu/Cu system, two kinds of experiments were designed, including:(1) solid-state aging between the solder and Cu substrate;(2)liquid-state aging between the metastable supercooled liquid-state solder and Cu substrate. The aging times were 30, 60,120 and 180 min, respectively, and the aging temperature was 8 ℃ lower than the melting point of the Sn-3.0 Ag-0.5 Cu(SAC305) alloy(217 ℃). The experimental data revealed that the physical state of the solder obviously affected the formation of the intermetallic compound(IMC), and resulted in the difference in the diffusion of atoms on the interface between the SAC305 solder and Cu substrate. The IMC interface after aging for 30 min presents unique characteristics compared with that of the sample after dip soldering. The IMC interface of solid-state aged SAC305/Cu couple is relatively planar, while the IMC interface under metastable supercooled liquid-state aging conditions presents scallop-like shape. 展开更多
关键词 LEAD-free solder SUPERCOOLING METASTABLE liquid state AGING INTERMETALLIC compound
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基于核磁共振的页岩油吸附/游离微观分布定量表征——以鄂尔多斯盆地三叠系延长组7段为例 被引量:2
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作者 刘飞 杜金良 +3 位作者 孙林 郭睿良 郝博斐 刘鹏 《石油实验地质》 北大核心 2025年第3期645-658,共14页
页岩油赋存状态及其可动性定量评价是当前页岩油地质研究的核心和难点问题。以鄂尔多斯盆地三叠系延长组7段(简称长7段)页岩为研究对象,采用饱和—离心—核磁共振实验方法,结合前人提出的页岩油吸附比例方程,对页岩油吸附/游离含量、比... 页岩油赋存状态及其可动性定量评价是当前页岩油地质研究的核心和难点问题。以鄂尔多斯盆地三叠系延长组7段(简称长7段)页岩为研究对象,采用饱和—离心—核磁共振实验方法,结合前人提出的页岩油吸附比例方程,对页岩油吸附/游离含量、比例、微观分布及可动性特征等开展了综合研究。在饱和正十二烷及20℃离心温度的条件下,长7段页岩游离/吸附油量平均分别为1.9814 mg/g和1.5481 mg/g,吸附油比例平均为0.4307。页岩油吸附相/游离相平均密度比为1.1713,吸附相平均密度为0.8778 cm3/g,平均吸附层厚度为0.9802 nm。吸附油主要赋存于微小孔(小于100 nm),游离油在微小、中、大孔中的赋存含量依次减少。高有机质页岩由于生烃增压微裂缝的存在和较不发育的有机质孔使得总体具有较高的游离油量和较低的吸附油量。石英相关孔隙会明显增大孔隙比表面积进而为吸附油提供更多赋存点位,而黏土矿物含量的增加会显著减少游离油赋存的孔隙体积。游离油量(Q_(f))与中值离心力(ΔP_(L))的比值(Q_(f)/ΔP_(L))是评价页岩油可动性的新型有效参数,该值越高,反映页岩油可动性越好。对于长7段页岩而言,Q_(f)/ΔP_(L)=1.3394 mg/(g·MPa)是页岩油可动性发生显著变化的阈值,大于该值,页岩油可动性明显变好。通过吸附比例方程计算的游离油理论赋存孔径下限介于1.9604~5.8812 nm之间,具体大小与孔隙形态有关。 展开更多
关键词 核磁共振 吸附/游离态 页岩油 微观分布 延长组 鄂尔多斯盆地
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FREE STANDING FILM OF POLYANILINE
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作者 万梅香 曹镛 +2 位作者 李军朝 周维侠 李素珍 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 1991年第3期209-219,共11页
A free standing film of polyaniline as large as 18 cm×18cm×0.002 cm can be obtained by evaporation of a solution of the chemically synthesized base in NMP. Its structure was examined by the elemental analysi... A free standing film of polyaniline as large as 18 cm×18cm×0.002 cm can be obtained by evaporation of a solution of the chemically synthesized base in NMP. Its structure was examined by the elemental analysis, IR, U.V.-visible spectra, XPS, DSC, SEM and X-ray scattering and its conducting behavior as well as electrochemical properties were studied. Results show that the composition, structure of main chain, physical properties of the free standing film of polyanilme is similar to that of the powder. However, some differences in its electronic structure, conductivity at room temperature and potential of redox couple between the flee standing film and powder are observed, which may be due to cross-linking of the film of polyaniline. 展开更多
关键词 Conducting polymers CONDUCTIVITY POLYANILINE free-standing Film The protonation state
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Combined multi-level quantum mechanics theories and molecular mechanics study of water-induced transition state of OH^- + CO_2 reaction in aqueous solution
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作者 李琛 牛美兴 +2 位作者 刘鹏 李永方 王敦友 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第10期200-204,共5页
The presence of a solvent interacting with a system brings about qualitative changes from the corresponding gas-phase reactions. A solvent can not only change the energetics along the reaction pathway, but also radica... The presence of a solvent interacting with a system brings about qualitative changes from the corresponding gas-phase reactions. A solvent can not only change the energetics along the reaction pathway, but also radically alter the reaction mechanism. Here, we investigated the water-induced transition state of the OH^-+CO2→HCO3^- reaction using a multi-level quantum mechanics and molecular mechanics method with an explicit water model. The solvent energy contribution along the reaction pathway has a maximum value which induces the highest energy point on the potential of mean force. The charge transfer from OH^- to CO2 results in the breaking of the OH^- solvation shell and the forming of the CO2 solvation shell. The loss of hydrogen bonds in the OH^- solvation shell without being compensated by the formation of hydrogen bonds in the CO2 solvation shell induces the transition state in the aqueous solution. The calculated free energy reaction barrier at the CCSD(T)/MM level of theory, 11.8 kcal/mol, agrees very well with the experimental value, 12.1 kcal/mol. 展开更多
关键词 transition state reaction pathway free energy barrier solvent effect
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Cavity loss induced generation of W states
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作者 吴怀志 杨贞标 +2 位作者 苏万钧 钟志荣 郑仕标 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第1期49-54,共6页
The existence of decoherence-free subspace (DFS) has been discussed widely. In this paper, we propose an alternative scheme for generating the four-atom W states by manipulating DF qubits. The atoms are divided into... The existence of decoherence-free subspace (DFS) has been discussed widely. In this paper, we propose an alternative scheme for generating the four-atom W states by manipulating DF qubits. The atoms are divided into two pairs and trapped in two separate optical cavities. Manipulation of atoms within DFS may generate a two-atom maximally entangled state in an individual cavity, which is a stable state. After driving the system out of DFS, the atoms will interact resonantly with the cavity field. The photons leaking from the cavities interfere at the beamsplitter, which destroys which-path information, and are finally detected by one of the detectors, leading to the generation of a W state. In addition, the numerical simulation indicates that the fidelity of the prepared state can, for a very wide parameter regime, be very close to unity. 展开更多
关键词 decoherence-free subspace leakage of photons W states
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