Slip flow in an annular sector duct using radial eigenfunctions

The fully developed slip flow in an annular sector duct is solved by expansions of eigenfunctions in the radial direction and boundary collocation on the straight sides. The method is efficient and accurate. The flow field for slip flow differs much from that of no-slip flow. The Poiseuille number increases with increased inner radius, opening angle, and decreases with slip.

Trace amounts of impurities in electrolytic manganese metal by sector field inductively coupled plasma mass spectrometry

An analytical method, using sector field inductively coupled plasma mass spectrometry （SF-ICP-MS） for rapid simultaneous determination of Be, Na, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, As, Sn, Sb, Pb and Bi in electrolytic manganese metal, was described. At the beginning, the samples were decomposed by HNO3 and H2504, and then analyzed by SF-ICP-MS. Most of the spectral interferences could be avoided by measuring in different mass resolution modes. The matrix effects due to the excess of sulfuric acid and Mn were evaluated. Correction of matrix effects was conducted by using the internal standard elements. The optimum condition for the determination was investigated and discussed. The detection limit is in the range of 0.001-0.169 gg/L. The current method is applied to the determination of trace impurities in electrolytic manganese metal. And experiments show that good results can be obtained much faster, more accurately and conveniently by current method.

Energy Analysis and Exergy Utilization in the Residential Sector of Cameroon

In this paper, we present an analysis of energy and exergy utilization in the residential sector of Cameroon by considering the sectoral energy and exergy flows for the years of 2001-2010. Exergy analysis of Cameroon residential sector utilisation indicates a less efficient picture than that obtained by the energy analysis. Cooking stands out as the most inefficient end use in the Cameroon’s residential sector. In 2010, the energy and exergy efficiency are determined and were respectively 58.74% and 22.63%. Energy and exergy flows diagrams for the overall efficiencies of Cameroon residential sector are illustrated and a comparison with the residential sector of other countries is also done. To carry out this study, a survey of 250 households was conducted and the sharing of the end uses of energy was done and data were gathered.

Some New Criterions for Overall Situation Stability, Sector Stability and Connection Stability of Volterra Systems

Stability of Volterra systems are discusses by subpositive definite matrix, and some new criterions for Volterra systems on overall situation stability, sector stability and connection stability are acquired. These results expand or improve some existing criterions.

Stochastic Air Traffic Flow Management for Demand and Capacity Balancing Under Capacity Uncertainty

This paper introduces an innovative approach to the synchronized demand-capacity balance with special focus on sector capacity uncertainty within a centrally controlled collaborative air traffic flow management(ATFM)framework.Further with previous study,the uncertainty in capacity is considered as a non-negligible issue regarding multiple reasons,like the impact of weather,the strike of air traffic controllers(ATCOs),the military use of airspace and the spatiotemporal distribution of nonscheduled flights,etc.These recessive factors affect the outcome of traffic flow optimization.In this research,the focus is placed on the impact of sector capacity uncertainty on demand and capacity balancing(DCB)optimization and ATFM,and multiple options,such as delay assignment and rerouting,are intended for regulating the traffic flow.A scenario optimization method for sector capacity in the presence of uncertainties is used to find the approximately optimal solution.The results show that the proposed approach can achieve better demand and capacity balancing and determine perfect integer solutions to ATFM problems,solving large-scale instances(24 h on seven capacity scenarios,with 6255 flights and 8949 trajectories)in 5-15 min.To the best of our knowledge,our experiment is the first to tackle large-scale instances of stochastic ATFM problems within the collaborative ATFM framework.

跨境资本极端流动与中国金融部门系统性风险传染

随着全球金融一体化程度提高,跨境资本大幅度异常流动越来越频繁,而跨境资本高频次极端流动可能会加剧金融部门脆弱程度、提高系统性金融风险。本文实证检验了涌入、骤停、外逃、回撤四种类型跨境资本极端流动对我国金融部门系统性风险的影响,得出以下结论:(1)我国跨境资本极端流动的持续期和发生频次均较高,说明我国跨境资本流动具有“大进大出”“急进急出”的特征,且跨境资本极端流动类型频繁转换区间与各金融部门系统性风险的局部峰值具有较高的同步性。(2)不同类型跨境资本极端流动对金融部门系统性风险的影响具有异质性。跨境资本涌入和外逃会增加金融部门的系统性风险,且此时保险部门是各金融部门的风险源;跨境资本骤停和回撤会降低金融部门系统性风险,但资本骤停期间,证券部门是风险源,而资本回撤期间,房地产部门则构成了金融系统的风险隐患。

资金流量核算:演进、模型及应用

围绕资金流量核算的演进历程、资金流量表的编制、模型以及应用四个方面,对资金流量核算研究进行评述。首先,从资金流量核算的起源、发展和完善三个阶段厘清资金流量表的发展脉络;其次,系统梳理国内和国际资金流量表的编制,比较分析主要经济体资金流量表的编制情况,并介绍资金流量表的预测方法;再次,介绍资金流量表的相关分析模型及原理;最后,重点归纳总结资金流量表的应用。

一种测量液膜厚度的超声相控阵实验装置

气液两相流存在于核反应堆蒸发、飞行器冷却、化工生产降膜蒸发等过程,界面波的动态测量对工业过程监控和生产优化具有重要意义。界面波的准确识别与特性参数测量是开展科学研究与工程实践的重要前提。基于超声相控阵测量系统,设计了扇扫的测量方式,可以用于气液界面清晰的流型中液膜厚度和界面波形态三维测量。通过静态标定和圆管验证,确定了像素点和液膜厚度之间的关系,在气相表观流速为0.0719~0.4316 m/s,液相表观流速为0.0567~1.4161 m/s的工况下进行实时动态实验,获得了实时流动过程中较高精度的截面气液相界面信息,并构建了管道内部界面波三维分布形态,为界面波特性研究提供了一种实验参考方法。

区域多扇区耦合容量评估

明确空域单元内部交通流特性及其动态演变机制是评估区域多扇区耦合通行能力的基础,对于提升空中交通管理效率至关重要。基于改进的元胞传输模型(CTM),以实际飞行数据为基增量仿真推演分析了交通流流量、速度与密度间的宏观基本图(MFD)。进一步表征区域多扇区之间的耦合作用,建立区域多扇区耦合快时仿真模型。通过分析区域多扇区需求平均延误关系对区域多扇区耦合容量进行评估,揭示区域运行瓶颈。以合肥区域管制扇区为例,评估了区域多扇区耦合容量,并依据各扇区的延误贡献识别了该区域多扇区运行瓶颈主要集中在ZSOFAR02扇区和ZSOFAR01扇区。研究成果可为提高区域多扇区航路航线网络通行能力提供科学的理论支撑。

The First Five Years of a Phase Theory for Complex Systems and Networks

In this paper,we review the development of a phase theory for systems and networks in its first five years,represented by a trilogy:Matrix phases and their properties;The MIMO LTI system phase response,its physical interpretations,the small phase theorem,and the sectored real lemma;The synchronization of a multi-agent network using phase alignment.Towards the end,we also summarize a list of ongoing research on the phase theory and speculate what will happen in the next five years.

Estimating inter-regional trade flows in China： A sector-specific statistical model

China has huge differences among its regions in terms of socio-economic development, industrial structure, natural resource endowments, and technological advancement. These differences have created complicated linkages between regions in China. In this study, building upon gravity model and location quotient techniques, we develop a sector-specific model to estimate inter-provincial trade flows, which is the base for making a multi-regional input-output table. In the model, we distinguish sectors with less intra-sector input from those with larger intra-sector input, and assume that the former sectors tend to compete among regions while the latter tend to cooperate among regions. Then we apply this new method of inter-regional trade estimation to three sectors： food and tobacco, metal smelting and proc- essing, and electrical equipment. The results show that selection of bandwidth has a significant impact on the assessment of inter-regional trade. Trade flows are more scattered with the increase of bandwidths. As a result, bandwidth reflects the spatial concentration of geo- graphical activities, which should be distinguishable for different industries. We conclude that the sector-specific spatial model can increase the credibility of estimates of inter-regional trade flows.

高压高速条件下柱塞副泄漏流场分析

建立了高压、高转速条件下柱塞泵柱塞副泄漏流场的数学模型,并进行了数值模拟分析。首先,对柱塞副进行了三维动力学分析,对柱塞副受力变化规律进行了Matlab数值分析。然后,建立了基于柱塞倾斜角度φ和偏心距离e的柱塞副倾斜偏心圆环缝隙泄漏流场数学模型,并结合柱塞副动力学分析结果,利用动压支撑理论确定了倾斜偏心泄漏流场数学模型中的φ和e。利用有约束的一维搜索法编写Matlab程序对柱塞副流场进行优化数值求解。最后,利用Fluent软件对柱塞副泄漏流量进行了仿真分析和实验验证。结果表明,高压、高转速条件下,柱塞副处于倾斜偏心状态,实际泄漏流量与通常理论假设的完全同心流场相比流量脉动量变大,而平均流量变小。

双电压合成矩阵变换器特性与电压扇区的关系分析

在双电压合成矩阵变换器中 ,需要将每个周期内的输入、输出电压划分成若干扇区。根据不同的划分方法 ,扇区的形状可以是S形或X形。首先对双电压合成方程的一般形式及占空比的计算方法进行了改进。然后研究了输入、输出电压扇区形状的四种组合即 {X ,X}、{X ,S}、{S ,X}、{S ,S}。针对每一种组合研究了矩阵变换器特性与相应扇区组合的关系。这些特性包括“原点开关”的存在性、最大电压增益及输入电流波形。通过分析比较得出 ,最佳输入、输出电压扇区组合是 {S ,X}。这种组合存在“原点开关” ,便于实现 ,能够同时获得最大的电压增益和对称的正弦输入电流 ,功率因数可以达到 1。通过仿真分析验证了结论的正确性。

中国页岩气开发理论与技术研究进展

中国的页岩气田属于非常规气藏,采用体积压裂工程技术才可以实现有效开采.不过,页岩储层与一般储层的性质不同,纳米级孔隙大量分布,其孔隙和渗透率十分微小,同时还分布有微裂缝,气体在其中的流动具有解吸、扩散、滑脱和渗流等多种微观机理,并且呈现出基质-微裂缝-人工裂缝的跨尺度多流态流动.常规的油气开发理论与技术并不适用于页岩气藏,因此需要有针对性的研究,并建立页岩气开发的理论与技术,才能实现我国页岩气藏的高效地开发.从页岩气流动的基本规律出发,总结了页岩气流动的多流态-多尺度-多场耦合输运机理和渗流规律,归纳了考虑解吸-扩散-滑移-渗流的多尺度非线性渗流统一方程,给出了多尺度全流态图版.通过页岩气多级压裂水平井多区耦合非线性渗流理论、多场耦合非线性渗流理论,形成页岩气藏流场区域储量动用与开发动态变化规律,针对我国页岩气特点构建了页岩气产量递减模型.基于上述理论提出了开发设计方法,提出了我国储层分级评价及优选目标评价方法,并且建立了适合我国储层的分级评价及优选目标方法与指标,对中国页岩气压裂开发工艺适应性技术进展进行了归纳总结.在此基础上,对未来页岩气高效开发理论的发展方向进行了展望,以期对我国页岩气理论和技术研究提供指导.

基于贝叶斯估计的短时空域扇区交通流量预测

为准确把握空域扇区流量分布态势及未来变化趋势,提出了一种基于贝叶斯估计的短时空域扇区交通流量预测方法.首先,通过解析空域系统内航空器原始雷达数据,提取各扇区历史运行信息,建立了多扇区聚合交通流模型;其次,采用贝叶斯估计理论对模型参数进行最优估计和动态更新,预测了空域扇区交通流量的未来演变趋势及其不确定范围;最后,选取国内5个典型繁忙扇区为例,以5 min为时间段,以未来1 h为预测范围,对所提预测方法进行了验证.研究结果表明:85%以上时段交通流量预测结果的绝对误差在3架以内,平均绝对误差均在2架次以内,预测结果的稳定性较好,可充分反映各空域扇区之间短时交通流的动态性和不确定性,符合空中交通的实际情况.

矩阵变换器双电压调制策略的简化控制

针对矩阵变换器传统双电压调制策略存在的扇区随机组合,导致占空比的不确定问题,提出把输入和输出电压区间由6个分成为3个。推导了新方法下输出线电压的通用数学表达式,在新模式下通过输入不平衡的三相电压,验证新的扇区划分方法仍然具有对电网扰动的抵抗能力。该方法简化了软硬件的控制过程,在原理方法上和传统的调制策略等效,在输入输出特性上差异很小。最后通过实验样机平台,用实验的方法验证了新模式的可行性。

中国地区宏观金融社会核算矩阵的编制

本文从突出金融部门角度 ,编制了中国地区宏观金融社会核算矩阵 ,该项研究对于决策者和研究人员全面了解和分析地区经济状况 ,提供了科学的经济数据库。首先 ,论文从宏观经济循环角度 ,在分析了金融部门和地区部门的特点基础上 ,研究了中国地区宏观金融社会核算矩阵的结构和内容 ;其次 ,以《江苏投入产出表》( 2 0 0 0 )和《江苏统计年鉴》为基础 ,结合大量调查 ,编制了江苏宏观金融社会核算矩阵 ;最后 ,利用跨熵 (crossentropy ,CE)技术 。

弯管流量计流量系数的研究

具体介绍了弯管流量计流量系数的实验研究情况,研究了同一规格的多个弯管流量计流量系数间的关系(公称2英寸、90度、弯径比1.5),得出了流量系数与实测弯径比之间的计算公式,为实现该规格的弯管流量计免标定做了一些工作.

农村劳动力跨部门流动能否缩小中国地区收入差距?

本文以劳动力流动规模和流动方式为切入点,探究了欠发达地区农村劳动力跨部门流动与地区收入差距之间的作用机制,为实证检验奠定了必要的理论支撑。在此基础上,考虑空间溢出效应,利用空间杜宾模型考察了2001—2015年期间我国农村劳动力跨部门流动对地区收入差距的影响与异质性表现。经研究发现:农村劳动力跨部门流动能够有效缩小地区收入差距,跨部门流动总规模的直接效应与总效应均显著为正,表明流动规模扩大既有利于提升本地区的相对收入水平,也对所有地区的平均影响呈积极态势;“本地流动”“外出-省内流动”以及“跨省流动”的直接效应和总效应均为正,三种流动方式均呈现有助于缩小地区间收入差距的特征;不同流动方式对本地相对收入水平的促进效应差异化明显,“本地流动”的直接效应大于“外出-省内流动”的直接效应,“跨省流动”直接效应最小;“本地流动”的直接效应大于“外地流动”的直接效应,“省内流动”的直接效应大于“跨省流动”的直接效应。

高超声速再入飞行器抗饱和控制系统设计

针对高超声速再入飞行器纵向静不稳定模型,在考虑气动执行机构饱和非线性特性的情况下,研究了一种基于补偿方案的抗饱和控制系统设计方法。该方法把系统输入饱和特性视为不确定性,采用H∞回路成形技术设计了标称控制器;然后针对标称控制器与被控对象所组成的闭环系统进行补偿器设计;最后基于高超声速再入飞行器纵向静不稳定模型验证了该补偿方案的有效性。