天然气管网系统的稳态安全域模型

参考电力系统的安全域概念,提出了天然气管网系统安全域（NGS-SR）的稳态模型、可视化与应用方法。NGS-SR能描述系统全部的安全状态;传统稳态仿真分析只能判断单个状态的安全性。对NGS-SR进行了定义：NGS-SR为系统运行时,所有安全工作点构成的集合;建立了NGS-SR的稳态模型,模型充分考虑了管道压降、节点流量与压力约束等安全要素。提出了NGS-SR安全边界的定义与模型;安全边界是NGS-SR中所有临界安全工作点的集合,NGS-SR是由安全边界围成的封闭区域。通过观测工作点的安全分界现象以说明安全边界的存在,并提出了NGS-SR的观测方法。提出了NGS-SR安全距离的概念与计算方法,对基于NGS-SR安全距离的安全性评估和安全控制进行了说明,简述了如何利用NGS-SR指导系统运行。算例验证了NGS-SR的存在性以及所建立模型与方法的正确性,并与传统安全分析方法进行了对比。NGS-SR描述了天然气管网系统的安全运行范围,可提供丰富的安全控制信息,有助于实现在线安全分析。     

基于关系推理与门控机制的视觉问答方法

针对现有的注意力机制存在缺乏对视觉对象间关系的理解能力及准确度较差的问题,在注意力机制的基础上增加关系推理模块与自适应门控机制. 该方法利用注意力机制关注多个与问题相关的视觉区域,利用关系推理模块中的二元关系推理与多元关系推理加强视觉区域间的联系. 将分别得到的视觉注意力特征与视觉关系特征输入到自适应门控中,动态控制2种特征对预测答案的贡献. 在VQA1.0及VQA2.0数据集上的实验结果表明：该模型与DCN、MFB、MFH及MCB等先进模型相比,在总体精度上均有约2%的提升;利用基于关系推理与门控机制的模型能够更好地理解图像内容,有效地提升视觉问答的准确率.     

川南页岩气体积压裂技术发展与应用

我国四川盆地页岩气资源丰富,经过10余年探索,中国石油在川南地区实现页岩气的规模效益开发,掌握了页岩气勘探开发核心技术,页岩气压裂理论、技术和方法从无到有,从单一到配套,实现了从跟跑到部分领跑的全面进步。2010年至今,川南地区页岩气压裂经历了先导试验、自主研发、系统完善、技术升级4个发展阶段,形成了以体积压裂工艺技术、体积压裂配套技术、压裂裂缝监测与压裂后效果评价技术、工厂化压裂技术为核心的3500m以浅页岩气水平井体积压裂技术体系。研究总结了现阶段页岩气压裂技术进展和应用成效,分析了已有技术的局限性、川南地区压裂难点,提出需要针对不同埋深的页岩储层地质特征开展针对性的压裂理论深化研究与技术攻关,需攻关3500m以浅老区提高采收率、3500m以浅新井提高产量和储量动用程度、3500m以深页岩气提高单井产量及复杂防控等领域,以支撑未来页岩气高效开发。     

用于CSNS反角白光中子源的双屏栅电离室设计及性能研究

为测量中国散裂中子源（China Spallation Neutron Source, CSNS）反角白光中子源150 keV以下能区飞行时间法中子能谱,研制基于¹⁰B(n, α)⁷Li和⁶Li(n, t)α核反应的双屏栅电离室,采用薄窗和薄底衬的结构设计。通过Garfield++、SRIM和Simcenter Magnet Electric程序对屏栅电离室的工作气体、极间距和电场分布等工作参数进行模拟设计,并采用α源及CF₄、P10、90%Ar-10%CO₂三种气体对电离室进行性能参数测试。结果表明,选定电子漂移速度快、扩散系数小,以及阻止本领大的CF4作为CSNS/Back-n束上测试工作气体,阴极-栅极和栅极-阳极间距分别为20 mm和5 mm。屏栅电离室收集区74 mm范围内是电场均匀区,场强的相对偏差≤0.03%;性能测试结果表明,工作气体为CF₄时,电离室对²³⁹Pu/²⁴¹Am/²⁴⁴Cm混合α面源具有很好的能量分辨,最佳能量分辨率为2.4%@5.48 MeV。对比平板型电离室和硅微条探测器的测量结果,验证了本工作研制的屏栅型电离室的能量分辨优势。     

Dynamic development model for long gap discharge streamer-leader system based on fractal theory

Establishing a long air gap discharge model considering the streamer-leader transition and randomness of the discharge path is of great significance to improve the accuracy of discharge characteristic prediction and optimize external insulation design. Based on fractal theory and thermal ionization theory of streamer-leader transition, this work establishes a dynamic development model for the long air gap discharge streamer-leader system, which includes streamer inception, streamer development, leader inception, development of streamer-leader system and final jump. The positive discharge process of a 3 m rod plate is simulated to obtain the fractal distribution of the discharge path and the law of leader development for comparison with the discharge test results. The results show that the simulation model is similar to test results in the development characteristics of leader path distribution, each stage time and leader velocity. Finally, a simulation calculation of a 50% breakdown voltage of the rod-plate gap and ball-plate gap is carried out, with results fairly consistent with test data, proving the effectiveness and practicality of the model.     

The effect of anode axial position on the performance of a miniaturized cylindrical Hall thruster with a cusp-type magnetic field

A 200 W cylindrical Hall thruster with a cusp-type magnetic field was proposed, manifesting convergent plume and high specific impulse. In this paper, a series of ring-shaped anodes are designed and the influence of anode axial position on the performance of CHT with a cusp-type magnetic field is studied. The experimental results indicate that the thruster keeps stable operation at the condition of 140–270 W discharge power. When the anode moves axially towards the upstream cusp field, the thrust enhances from 6.5 mN to 7.6 mN and specific impulse enhances from 1658 s to 1939 s significantly. These improvements of thruster performance should be attributed to the enhancement of current utilization, propellant utilization and acceleration efficiency. According to the analyses on the discharge characteristics, it is revealed that as the anode moves upstream, the electron transport path could be extended, the magnetic field in this extended path could impede electron cross-field transport and facilitate the ionization intensity, yielding to the enhancement of current utilization and propellant utilization efficiency. Moreover, along with this enhancement of upstream ionization at the given anode flow rate, the main ionization region is thought to move upstream and then separate more apparently from the acceleration region, which has been demonstrated by the narrowing of ion energy distribution function shape. This change in acceleration region could decrease the ion energy loss and enhance acceleration efficiency. This work is beneficial for optimizing the electrode structure of thruster and recognize the ionization and acceleration process under the cusp magnetic field.     

DNA sequence of the mat2,3 region of Schizosaccharomyces kambucha shares high homology with the corresponding sequence from Sz. pombe

To define conserved sequences for mat1 imprinting and silencing of the mat2,3 region of Schizosaccharomyces pombe, we determined the DNA sequence of the cognate region (mat2,3 region) of another fission yeast, Sz. kambucha, a yeast species isolated from Kambucha tea mix. The entire mat2,3 region shows more than 98% identity between the two species. Sequence similarity is even higher (99.3%) for mating-type cassettes; deduced amino acid sequences of three of the four Mat peptides (Pi, Pc and Mi) are identical between the two species, while the fourth (Mc) has a single amino acid polymorphism. Comparison of the sequence motif of the imprint site essential for mat1 switching shows that mat-P of Sz. kambucha has a sequence identical to the conserved motif present in Sz. pombe. However, this sequence motif of nine bases differs by one base for mat-M of Sz. kambucha. The sequence of the K region shows about 98% identity between the two species, with the cenH region showing 98.3% homology. Thus, the arrangement of the mat2,3 region in both yeasts is conserved and shows 1-2% nucleotide sequence variation throughout the region. The DNA sequence of the mat2,3 region from Sz. kambucha has been submitted to GenBank under Accession No. AY271822.     

钾原子的能量积聚诱导电离和双光子共振三光子电离

用染料激光激发钾蒸气 ,发现了钾原子的两种电离机制和三个电离通道 :能量积聚诱导的电离 ,4S 6S和4S 4D双光子共振三光子电离。对前两个电离通道 ,分别研究了电离谱与钾蒸气温度和激光强度的关系 ,发现了钾原子的辐射囚禁效应和钾原子电离的非线性现象 ,并给出了定性解释     

一种基于灰度连续区域分割的视频对象分割方法

针对目前许多分割方法中分割边界不精确、计算复杂和缓存帧多等问题，提出了一种结合空间区域分割和运动象素检测的自动分割方法：先将当前视频帧分割为不同的灰度连续区域，再利用二次帧差确定视频图像中的运动象素，然后按一定的规则确定哪些灰度连续区域属于运动区域，从而有效地从静止的复杂背景中分割出运动对象区域。实验结果表明这种分割方法计算简单、分割边界比较精确。