Reasonable start time of carbon dioxide injection in enhanced coalbed methane recovery involving thermal-hydraulic-mechanical couplings

Injection of gas (CO_(2)) into coal seams is an effective method to benefit from both CO_(2) geological storage and coalbed methane recovery. Based on the dual pore structure of coal mass, and the Weibull distribution of fracture permeability, a menmal-hydraulic-mechanical (THM) coupling mathematical model is proposed involving the non-isothermal adsorption of binary gases, dynamic gas diffusion between matrix and fractures, multiphase seepage, coal deformation, heat conduction and heat convection. This mathematical model is applied to study the process of CO_(2)-enhanced coalbed methane recovery (CO_(2)-ECBM). Results show that the CH4 content of CO_(2)-ECBM in coal seam decreases significantly when compared with that of regular drainage, and decreases rapidly in the early stage but slowly in the later stage. Coal seam permeability evolution is triggered by changes in gas adsorption/desorption, temperature and effective stress. For regular drainage, the early permeability shows a decreasing trend dominated by the increase of effective stress, while the later permeability shows an increasing trend dominated by the CH4 desorption caused shrinkage of coal matrix. For CO_(2)-ECBM, the permeability in coal seam generally shows a downward trend due to both matrix swelling induced by gas adsorption and thermal expansion, particularly near injection well. There appears an increased and delayed peak production rate of CH4. The CH4 production rate of CO_(2)-ECBM is always higher than that of regular drainage. The CH4 cumulative production and CO_(2) cumulative storage linearly increase with time, and the CH4 cumulative production of CO_(2)-ECBM increased by 39.2% in the duration of 5000 d compared with regular drainage. Reasonable CO_(2) injection starting time can overcome the issue of early CO_(2) breakthrough and ineffective increase of CH4 production. In the studied case, the optimal injection starting time is 2500 d. Compared with the simultaneous CH4 extraction and CO_(2) injection, the CH4 cumulative production of optimal time has increased by 30.1%. The research provides a reference for determining the reasonable CO_(2) injection time under similar conditions.

Study of the efficiency of event start time determination at BESⅢ

A method to estimate the efficiency of event start time determination at BESIII is developed.This method estimates the efficiency at the event level by combining the efficiencies of various tracks(e,μ,π,K,p,γ)in a Bayesian way.Efficiencies results and the difference between data and MC at the track level are presented in this paper.For a given physics channel,event start time efficiency and systematic error can be estimated following this method.

Determination of event start time at BESⅢ

The principle of the method for the BESⅢ event start time determination and the code construction are described. The investigation of influence of the noise, the method of rejecting noise and the performance checking by the Monte Carlo physics data sample are also presented. The preliminary results got from the Monte Carlo simulation are presented, the reconstruction effciency of J/ψ→anything events at noise level 0～60% can achieve above 99%, and the error rate is below 1%.

Stochastic modeling for starting-time of phase evolution of random seismic ground motions

In response to the challenge inherent in classical high-dimensional models of random ground motions, a family of simulation methods for nonstationary seismic ground motions was developed previously through employing a wave-group propagation formulation with phase spectrum model built up on the frequency components' starting-time of phase evolution. The present paper aims at extending the formulation to the simulation of non-stationary random seismic ground motions. The ground motion records associated with N–S component of Northridge Earthquake at the type-II site are investigated. The frequency components' starting-time of phase evolution of is identified from the ground motion records, and is proved to admit the Gamma distribution through data fitting. Numerical results indicate that the simulated random ground motion features zeromean, non-stationary, and non-Gaussian behaviors, and the phase spectrum model with only a few starting-times of phase evolution could come up with a sound contribution to the simulation.

小口径定距空爆弹末端防空拦截实时模拟及开舱距离研究

针对现有小口径定距空爆弹末端防空拦截及开舱距离模拟中,无法体现开舱后子弹云团与目标的动态交会过程,并忽略了定距空爆引信实际启动规律,导致毁伤效能评估不准确的问题,开展小口径定距空爆弹末端防空拦截实时模拟及开舱距离进行研究。通过建立多束定向预制破片战斗部、弹目交会及以巡航导弹为拦截目标的等效目标数值模型,搭建小口径定距空爆弹末端防空拦截实时模拟平台。基于实时模拟平台,引入武器系统误差与定距空爆引信实测启动规律,分析炮弹在不同射击距离下开舱距离与毁伤效能的关系,并对小口径定距空爆弹引信技术发展方向进行展望。研究结果表明,引信实际启动规律使得最优毁伤效能随射击距离的增加而减少的幅度增大,在射击远距离目标时,0~20 m的开舱距离内都存在着较高的完全脱靶率。

基于燃烧状态反馈的柴油机低温冷起动逐循环控制研究

为改善低温冷起动工况不良燃烧循环,利用CompactRIO控制器开发了燃烧状态反馈系统,实现了缸压采集和燃烧状态参数实时计算及反馈。设计试验探明了不同温度和转速下喷油时刻对CA50(缸内累积放热量达到50%时所对应的曲轴转角)的影响规律,提出了基于燃烧状态反馈的喷油时刻逐循环控制方法,实现了燃烧参数与控制参数的匹配。采用该控制方法后CA50更集中在高效燃烧区间,最高燃烧压力更高且不良燃烧循环得到改善,起动时间平均减少36%,有效改善了柴油机低温冷起动性能。

萧劲光在安源工作的起止时间考

萧劲光是我国杰出的无产阶级革命家、军事家,国家和军队的优秀领导人,人民海军的主要创建者。萧劲光1922年加入中国共产党,有着漫长而辉煌的革命生涯。安源是萧劲光革命生涯的首站,具有重要意义。现有史料证明,1924年10月初,刚从苏联留学回国的萧劲光,因其突出的革命素养,奉派来到安源参加革命工作,1925年7月下旬离开安源奔赴广东参加国民革命。

分娩镇痛启动时机对分娩结局影响的Meta分析

目的探讨分娩镇痛时机对分娩结局的影响。方法在国内外各大知名数据库检索关于分娩镇痛启动时机相关文献,对文献进行筛选,并用RevMan 5.3.5软件进行分析。结果共纳入14篇文献,证据强度中等。结论目前并无研究表明早期实施分娩镇痛会导致分娩不良结局,反而可以缩短第一产程时间。因此,为了提升产妇分娩舒适度,可以不必按照宫口大小而是根据产妇意愿实施分娩镇痛。

MICAPS中Datatime维护的关键问题

系统介绍了MICAPS中Datatime节目表的功能以及Datatime节目表各项内容的设定对获取资料的作用。对及时地获取各种数值预报产品的技术作了详尽阐述,指出时间、通道和文件名的合理设定直接影响到文件传输的有效性,程序处理的时间搭配和运行方式将影响到计算机的工作效率,也会影响到资料接收的完整性和及时性。

提高含硫气田场站燃气发电机一次启动成功率技术研究

燃气发电机作为气井生产应急保障单元,为高含硫场站自控、通信、仪表系统提供稳定的电源,它一次启动成功对保障气井安全平稳开采具有重要意义。文章针对XX气田场站燃气发电机停市电后难以一次启动成功的情况,对燃气发电机运行现状、工作原理、环境条件等进行分析,确定影响发电机启动成功率的主要因素。通过改进发电机进气结构、优化蓄电池管理、完善巡检制度等措施,将发电机一次启动成功率由55%提升至100%,有效降低了高含硫场站燃气发电机故障频率和维修成本,保障了气田异常停电后的生产安全。

300 MHz、139 fs全光纤超短脉冲激光器

高重复频率超短脉冲光纤激光器在高效加工、生物光学成像等方面具有广泛的应用价值。报道了基于非线性偏振演化效应的高重复频率、百飞秒、集成化光纤激光源。通过集成结构实现重频300.25 MHz、脉冲宽度139 fs的脉冲激光。在384.2 mW的平均泵浦功率下,该激光器连续工作12 h,光谱输出形状未发生变化。其中在6 h内,重复频率漂移量约为25 Hz。此外,该激光器在泵浦功率为512.8 mW时,可以实现自启动,因此,这种结构简单,高重复频率的超短脉冲锁模光纤激光器是一种具有广泛应用潜力的激光源。

An Integrated Scheduling Algorithm for the Same Equipment Process Sequencing Based on the Root-Subtree Vertical and Horizontal Pre-Scheduling

Given the existing integrated scheduling algorithms,all processes are ordered and scheduled overall,and these algorithms ignore the influence of the vertical and horizontal characteristics of the product process tree on the product scheduling effect.This paper presents an integrated scheduling algorithm for the same equipment process sequencing based on the Root-Subtree horizontal and vertical pre-scheduling to solve the above problem.Firstly,the tree decomposition method is used to extract the root node to split the process tree into several Root-Subtrees,and the Root-Subtree priority is set from large to small through the optimal completion time of vertical and horizontal pre-scheduling.All Root-Subtree processes on the same equipment are sorted into the stack according to the equipment process pre-start time,and the stack-top processes are combined with the schedulable process set to schedule and dispatch the stack.The start processing time of each process is determined according to the dynamic start processing time strategy of the equipment process,to complete the fusion operation of the Root-Subtree processes under the constraints of the vertical process tree and the horizontal equipment.Then,the root node is retrieved to form a substantial scheduling scheme,which realizes scheduling optimization by mining the vertical and horizontal characteristics of the process tree.Verification by examples shows that,compared with the traditional integrated scheduling algorithms that sort the scheduling processes as an overall,the integrated scheduling algorithmin this paper is better.The proposed algorithmenhances the process scheduling compactness,reduces the length of the idle time of the processing equipment,and optimizes the production scheduling target,which is of universal significance to solve the integrated scheduling problem.

计及精细化氢能利用的综合能源系统多时间尺度鲁棒优化策略

能源结构改革背景下,构建以氢能驱动、电-热为主体的综合能源系统(HEH-IES)具有重要意义。为提高含电氢耦合单元的IES运行灵活性,同时减小功率波动对系统的影响,提出含多元储能与综合需求响应的氢能精细化利用两阶段调度方法。首先,分析电制氢(P2H)两阶段运行过程与电氢耦合单元运行特性,对氢能的用能过程与设备进行精细化建模;其次,计及多元储能与综合需求响应提出了日前-日内两阶段多时间尺度优化策略,日前阶段充分考虑能源系统的不确定性,构建数据驱动的分布鲁棒优化(DRO)模型,日内阶段遵从日前计划,考虑多能流在灵活性调节时间尺度上的差异,通过多时间尺度的滚动优化降低功率波动的影响;最后,仿真算例证明了所提模型与策略对提升IES的运行灵活性具有积极作用。

双喉道Ludwieg管风洞启动过程及其有效运行时间延长

Ludwieg管风洞是开展高超声速空气动力学实验基础研究的重要平台。但是,快开阀启动式高超声速Ludwieg管风洞长期受快开阀影响,产生不同类型的来流扰动模态。双喉道气动布局可有效消除快开阀启动式高超声速Ludwieg管风洞上游部件的扰动来源,但是会导致风洞有效运行时间大幅缩短。针对该问题,通过非定常数值模拟对双喉道气动布局高超声速Ludwieg管风洞的启动特性进行研究,然后对第1喷管扩张段与稳定段进行了融合设计,研究了不同扩张角与稳定段组合对风洞启动时间以及流场品质的影响。结果表明,采用减小扩张角组合设计能够使双喉道气动布局高超声速Ludwieg管风洞的有效运行时间提升近20%,并且对下游实验段内的静态流场品质几乎无影响,有效提高了风洞的实验能力。同时,相较于较大的扩张角组合,较小的扩张角设计能够减少约10%的总压损失。

SIKOSTART 3RA22型软启动器在工程中的应用

介绍了天津还原铁工程中使用的西门子SIKOSTART 3RA2 2软启动器的结构与功能 ,它具有控制方式灵活多样、各种控制功能完善、设备性能稳定、操作简便等优点 ,使用该控制器保证了生产设备的顺利平稳启动 。

Characterization of Groundwater Pollution Sources with Unknown Release Time History

Characterizations of unknown groundwater pollution sources in terms of source location, source flux release history and sources activity initiation times, from sparse observation concentration measurements are a challenging task. Optimization-based methods are often applied to solve groundwater pollution source characterization problem. These methods are effective only when the starting times of activity of the sources are precisely known, or the possible time window within which the sources activity actually start is known with a fair degree of certainty. However, in real life scenarios, the starting time of the activity of the sources is either unknown or can lie anywhere within a time window of years or decades. Absence of any prior information about the span of time window, within which the sources become active, makes existing source identification methodologies inefficient. As an alternative, an optimization-based source identification model is proposed, to simultaneously estimate source flux release history and sources activity initiation times. The method considers source flux release history and sources activity initiation times as explicit decision variables, optimally estimated by the decision model. Performance of the developed methodology is evaluated for an illustrative study area having multiple sources with different source activity initiation times, missing observation data and transient flow conditions. These evaluation results demonstrate the potential applicability of the proposed methodology and its capability to correctly estimate the unknown source flux releasing history and sources activity initiation times.

Improved Model of Start-Wave Velocity at Intersections Based on Unmanned Aerial Vehicle Data

The basic parameters involved in current start-wave theoretical models such as density and velocity are difficult to obtain through traditional traffic detection devices. Thus it is hard to apply these theoretical models to the actual verification and prediction for real situation. Unmanned aerial vehicle( UAV),which can shoot aerial video and identify vehicles, roads and other objects, is introduced in this study as a new type of traffic information collection method to gather the real-time data of the necessary parameters. An improved start-wave velocity model is proposed,where the speed and density of traffic flow are converted into vehicle space headway,mean vehicle length and other auxiliary parameters which can be recognized from aerial video or other means. A UAV was used for video shooting at intersections in a flight experiment in order to verify the accuracy of the calculated start-wave velocity.The mean absolute error rate between the calculated velocity and the actual velocity is 2. 277%. Moreover, the improved start-wave velocity model showed much better accuracy than the traditional start-wave velocity model. The results indicate that the improved model is accurate enough to be used for model calibration and validation in signal timing optimization.

杭州市科技型初创企业时空演化及区位选择

根据杭州市2005—2020年期间创立的5 414家科技型初创企业样本数据,采用核密度估计、Ripley’s K函数、条件Logit回归等方法分析科技型初创企业的时空演化格局与区位选择影响因素变化,为城市科技产业发展和规划布局提供参考依据。结果表明,科技型初创企业主要分布于西湖区、滨江区和余杭区三个核心区域,并有明显的空间集聚效应,且集聚范围随着年份的推进不断扩大;从演化特征来看,已从相互竞争分裂的块状分散格局转变为片状集聚分布的格局;在网格层面,政策要素、集聚要素和区位要素均是杭州科技型初创企业区位选择的重要影响因素,但不同时期其主要影响有较大差异。

超薄交替变径通道平板脉动热管的传热特性

采用印刷电路工艺,设计制作了厚度为1.00 mm的铜基平板脉动热管.宽度分别为1.00和2.20 mm的通道在平板脉动热管内交替排布,宽通道底部为刻蚀有平行微槽的阵列结构.以HFE-7100为工质,在充液率为30%~50%条件下,对有、无微槽结构的交替变径通道平板脉动热管的启动和传热性能开展比较研究.研究结果表明:平板脉动热管在水平和竖直放置时均可以正常启动,且实现稳定运行,引入微槽结构可以显著改善脉动热管的启动和传热性能,降低蒸发段温度,并增强其抗重力性能;在加热功率为24 W、充液率为30%条件下,超薄脉动热管分别呈水平和竖直放置时,其等效导热系数可分别达到1241和1226 W/(m·℃),比无微槽脉动热管分别提高25.6%和18.7%,能够较好满足部分芯片器件散热冷却的需要.

涡扇发动机装机状态自然低温试验

为完成涡扇发动机状态鉴定,在北方场站开展了发动机装机状态下的自然环境低温试验。通过地面试验完成了自然低温试验环境的量化分析,研究了不同气源起动模式、不同使用方法对装机状态自然低温条件下发动机起动性能的影响,分析了发动机样本量对试验鉴定结果的影响。结果表明:APU供气是低温冷浸透起动的首选起动方式;冷运转可以有效改善发动机低温起动性能,使相对起动时间缩短0.125~0.250;增加发动机样本量可以获得更加科学的鉴定结果,在低温起动过程中,发动机可能出现失速等不稳定现象,甚至造成起动失败。开展了飞行试验,研究了空中低温环境对发动机工作参数及加减速特性的影响。结果表明:在相同高度和速度下发动机加速时间随进气温度的降低而延长,当空中进气温度相差约30℃时,加速时间延长最多约为18%;减速时间随进气温度的变化不大。