基于精准能量平衡与预测控制的协调控制系统优化

我国火电机组面临煤质煤种多变的问题,随着电网对AGC、一次调频要求的不断提高,火电机组需进一步提升机炉协调控制系统的适应能力。超超临界机组具有高效节能的特点,是目前提高火电机组热效率的有效途径,以超超临界机组机炉协调控制系统作为研究对象,构建了超超临界机组非线性控制模型以及入炉煤低位发热量的软测量方法,实现了锅炉输入热量、锅炉动态蓄能和汽机侧能量需求的精准平衡;并采用阶梯式预测控制算法取代常规的PID控制器,将前馈和解耦的控制思想融入预测控制算法中,进一步克服了系统强耦合、大惯性、大迟延特性对调节性能的影响,实现了机组在高效宽负荷范围的高效灵活运行。仿真结果表明,加入入炉煤低位发热量作为控制器前馈后,主蒸汽压力、中间点焓值、主汽阀开度等参数均能快速响应滑压运行需求,且有效降低被控参数的超调量;当煤质发生变化时,控制器能迅速调节给煤量,各参数能快速回归设定值,且超调量较小;基于精准能量平衡的阶梯式预测协调控制策略可以有效抑制煤质扰动及锅炉蓄能变化对机炉调节性能的影响,从而进一步提升主汽压力调节的快速性和平稳性。

母猪能量需求研究进展

满足能量需要是决定动物生产效益的关键因素之一。能量需要划分为维持需要和生产需要。维持是指动物生存过程中的一种基本状态,在这种状态下,成年动物或非生产动物保持体重不变,体内营养素的种类和数量保持恒定,分解代谢和合成代谢处于动态平衡。维持需要是指动物在维持状态下对能量和其他营养素的需要。满足维持需要后,摄入能量被用于动物生产、繁殖需要。母猪饲养管理分为四个阶段,分别为后备期、妊娠期、围产期和哺乳期。由于每个阶段母猪生理状态和生产目的不同导致能量需求不同。文章综述了不同时期母猪的能量需求及日粮能量水平、饲喂模式对母猪繁殖性能的影响,为母猪饲粮精准能量水平提供参考依据。

致密油准自然能量开发及产能影响因素研究

致密油准自然能量开发前期受体积压裂区域滞留的入地液影响,近井地带能量得以补充。致密油在生产过程各阶段有不同的能量贡献,在准自然能量开发中,如何实现能量的有效接替,成为致密油藏准自然能量开发提高产能的关键。本文以长庆油田长7油藏为例,分析了X生产试验区块内产能差异的原因,揭示了致密油准自然能量开发各生产阶段产能影响因素,可为致密油藏准自然能量开发压裂、井网部署及工作制度优化提供重要参考。

周期受击简谐振子系统的经典动力学与准能谱统计

研究一个周期受击简谐振子系统在非谐振情况下的经典动力学与准能谱统计.研究发现,随着打击强度κ的增加,经典相空间结构从可积(环)到完全混沌时,准能谱按最近邻能级间距分布仍保持Poisson分布不变,这与周期受击转子系统的结果相同.谱刚度的计算表明,除了κ=30的情况外,κ=0.13、1.6、2.0、2.6等的谱刚度在L<0.1的范围内随L线性变化,呈束状;在L>0.1以后发散开来,呈非线性变化,且κ=0.13的谱刚度趋于饱和.数方差Σ2及高阶矩γ1,γ2随κ的变化不敏感.

谐振子中的Floquet两体问题

由于近期在光诱导的Feshbach共振等实验技术上的发展,具有含时相互作用的量子气体的动力学问题引起了学界广泛的兴趣.人们已经在这一类超冷原子系统中观察到了一系列诸如Farady图案和玻色焰火等新颖的动力学行为.研究了具有周期性调节相互作用强度的谐振子势阱中的两原子动力学问题.虽然Hamilton量的时间依赖性,使系统的能量不再是一个守恒量,但仍然可以利用随时间周期变化的Hamilton量的Floquet理论定义其准能量.推导出了两体问题准能量的精确方程.通过数值求解这些方程,揭示了两体准能谱在不同驱动参数或频率下展现出的各种新颖的动力学行为.

长周期潮汐与全球地震能量释放

采用1850—2012年期间USGS全球M≥5.0地震目录资料,构成全球地震能量-时间序列,进行小波变换和准周期分析.结果表明,全球地震能量释放的时间序列存在9年、19年和45年的3个准周期,其中,45年准周期最为突出.结合起潮力周期的物理背景,对长周期潮汐起潮力与地震能量释放准周期的关系进行了探讨,没有发现全球地震活动的能量释放与潮汐短周期相关的准周期.

乌拉尔阻塞高压的维持发展及其与2020/2021年冬季强寒潮活动的关系

2020年岁末至2021年初前后两次强寒潮侵入我国,引起大范围的强烈而持续的降温。本文对于其相应的环流特点及成因进行了分析研究,主要结论是:(1)从环流形势看,两次寒潮的发展过程,都是属于“横槽转竖”的类型。但是,自2020年的12月中旬至第二次寒潮结束,乌拉尔地区始终维持着宽广的高压脊(阻高),并未出现阻塞崩溃或不连续后退的现象。这与多数东亚地区寒潮爆发时的环流特点有差别。(2)乌拉尔阻塞高压及其脊前北风的加强和维持,使其前侧的斜压性大大加强。下游槽底的等高线日益密集,冷平流也不断发展,增强和向南推进。这些都推动了西伯利亚高压的加强和南扩。(3)在两次寒潮过程发生之前,源自0°E附近的低频静止波能量向东传播,有利于乌拉尔高压脊的维持、加强以及其下游低槽发展,为冷空气的向南爆发提供有利条件。

周期受击简谐振子系统的经典与量子动力学

研究一个周期受击简谐振子系统的经典与量子动力学.研究发现,随着打击强度κ的增加,经典相空间发生分形时,一步时间演化算符的本征值分布也从单位圆的圆周上朝着圆心扩散.而当本征值归一化后,归一化后的本征值分布又回到单位圆周上.

致密油藏多级压裂水平井同井缝间注采可行性

以大庆油田L致密油藏为例,评价了L致密油藏的压裂改造效果;通过现代产量递减分析和试井分析,总结了生产动态规律;论证了水平井准天然能量、注水吞吐、注CO_2吞吐开发效果。针对致密油藏水平井产量递减快的问题,提出多级压裂水平井同井缝间注采方法,即通过注采分隔装置和注采阀进行同井缝间注采,将井间驱替问题转化为缝间驱替问题。采用数值模拟方法,分别计算了准天然能量衰竭开发、注水吞吐、CO_2吞吐、同井缝间注采4种方式的开发指标。分析结果表明,注水吞吐只能短期内提高累积采油量,不能显著提高采收率;同井缝间注采的产量比CO_2吞吐的产量高、稳产期更长、递减率更小、开发效果更好。进一步提出了致密油藏有效开发方式,即先以准天然能量衰竭式开采,控制地层压力均衡下降,在井底压力降到饱和压力附近时,转入同井缝间异步注采。现场实施时,采用水平井缝间强凝胶封堵完井工艺,即在注采缝之间的水平段射孔、注入强凝胶、封堵套管外侧与岩石连通空间。安装注采分隔装置和配注阀,采用温和注水方式,发挥裂缝的渗吸作用,能控制注入水的快速推进,提高致密油藏产量和采收率。

热力学与时空几何

简要介绍引力场的准局域能量及表面压强的概念 ,并在此基础上 ,从热力学第一定律出发 ,加上一些合理的假设 ,推导出史瓦西度规 .这一结果支持了这样一种看法 :热力学与引力有密切的联系 。

An amplitude suppression method based on the decibel criterion

To suppress the strong noise in seismic data with wide range of amplitudes, commonly used methods often yield unsatisfactory denoising results owing to inappropriate thresholds and require parametric testing as well as iterations to achieve the anticipated results. To overcome these problems, a data-driven strong amplitude suppression method based on the decibel criterion in the wavelet domain （ISANA） is proposed. The method determines the denoising threshold based on the decibel criterion and statistically analyzes the amplitude index rather than the abnormally high amplitudes. The method distinguishes the frequency band distributions of the valid signals in the time-frequency domain based on the wavelet transformation and then calculates thresholds in selected time windows, eventually achieving frequency-divided noise attenuation for better denoising. Simulations based on theoretical and real-world data verify the adaptability and low dependence of the method on the size of the time window. The method suppresses noise without energy loss in the signals.

骨密度量值溯源系统设计研究

双能X射线骨密度仪(Dual Energy X-ray Absorptiometry,DEXA)测量获得的骨密度值是用于骨质疏松症诊断的国际金标准,但不同品牌DEXA测量结果的一致性和骨密度值的准确性及溯源方法尚未获得足够关注。为统一DEXA的测量结果,同时为骨质疏松症临床诊断结果互认提供技术支持,本文拟设计并搭建一套多能量X射线骨密度模体校准装置,研究DEXA骨密度模体计量检测和溯源方法,解决DEXA测量骨密度的量值统一和溯源问题。目前,该校准装置已完成设计与加工,经试验验证其辐射剂量等稳定性指标优于1%。

鄂尔多斯盆地长7页岩油藏水平井生产制度

为合理制定长7页岩油藏水平井的生产制度,保障长7页岩油藏的单井产量,基于鄂尔多斯盆地长7页岩油藏开发的理论研究与生产资料,通过计算水平井体积压裂后人工裂缝缝内压力传播距离与时间的关系,以传播到边界的压力不随时间变化的原则确定合理闷井时间为40 d;高含水排液阶段结束的标志是采出水矿化度分析值与原始地层水相近或水平井压裂液置换率大于60%;通过定量分析水平井单段及百米水平段生产规律,建立动态关系式,确定各阶段合理的产液量。

An improved joint method for onset picking of acoustic emission signals with noise

The onset times of acoustic signals with spikes,heavy bodies and unclear takeoffs are difficult to be picked accurately by the automatic method at present.To deal with this problem,an improved joint method based on the discrete wavelet transform(DWT),modified energy ratio(MER)and Akaike information criterion(AIC)pickers,has been proposed in this study.First,the DWT is used to decompose the signal into various components.Then,the joint application of MER and AIC pickers is carried out to pick the initial onset times of all selected components,where the minimum AIC position ahead of MER onset time is regarded as the initial onset time.Last,the average for initial onset times of all selected components is calculated as the final onset time of this signal.This improved joint method is tested and validated by the acoustic signals with different signal to noise ratios(SNRs)and waveforms.The results show that the improved joint method is not affected by the variations of SNR,and the onset times picked by this method are always accurate in different SNRs.Moreover,the onset times of all acoustic signals with spikes,heavy bodies and unclear takeoffs can be accurately picked by the improved joint method.Compared to some other methods including MER,AIC,DWT-MER and DWT-AIC,the improved joint method has better SNR stabilities and waveform adaptabilities.

Gradient principle of horizontal stress inducing rock burst in coal mine

Based on the stress distribution characteristics of rock burst multiple sites, the criterion of horizontal stress inducing layer dislocation rock burst was established. Accordingly, the influencing factors were analyzed. The analysis results indicate that the stress condition, edge of etastic zone depth, supporting strength, and the friction angle and cohesion among coal stratum, roof and floor are sensitive factors. By introducing double-couple model, the layer dislocation rock burst was explained and the energy radiation characteristics were analyzed. The SOS micro-seismic monitoring system was applied to observe the rock burst hazards about a mining face. The results show that P- and S-wave energy radiations produced by rock burst have directional characteristics. The energy radiation characteristics of the 22 rock bursts occurring on 79Z6 long-wall face are basically the same as theoretical results, that is, the ratio of S-wave energy of sensor 4 to 6 is about 1.5 and that of P-wave is smaller than 0.5. The consistency of the monitored characteristics of the energy radiation theoretically increases with the total energy increasing.

Roll-to-roll imprint for high precision grating manufacturing

In this paper,a novel roll-to-roll imprint process is proposed to fabricate gratings in large area. The key challenges in roll-to-roll imprint process,such as the roller mold preparation,imprint system,misalignment of imprint roller and backup roller,and also the imprint pressure,are investigated. Various gratings with different periods and profiles are obtained by the roll-to-roll process. To calibrate the measuring ability of the self-made grating by imprint,a calibration system is built with a dual-frequency laser interferometer. By the calibration,the self-made gratings can achieve ±4μm accuracy in 45mm measuring distance.

Response and energy dissipation of rock under stochastic stress waves

The response and energy dissipation of rock under stochastic stress waves were analyzed based on dynamic fracture criterion of brittle materials integrating with Fourier transform methods of spectral analysis. When the stochastic stress waves transmit through rocks, the frequency and energy ratio of harmonic components were calculated by analytical and discrete analysis methods. The stress waves in shale, malmstone and liparite were taken as examples to illustrate the proposed analysis methods. The results show the harder the rock, the less absorption of energy, the more the useless elastic waves transmitting through rock, and the narrower the cutoff frequency to fracture rock. When the whole stress energy doubles either by doubling the duration time or by increasing the amplitude of stress wave, ratio of the energy of elastic waves transmitting through rock to the whole stress energy (i.e. energy dissipation ratio) is decreased to 10%-15%. When doubling the duration time, the cutoff frequency to fracture rock remains constant. However, with the increase of the amplitude of stress wave, the cutoff frequency increases accordingly.

Energy increment criteria for evaluation of train derailment

The criteria for evaluation of train derailment were studied. The worldwide commonly used evaluation criteria for wheel derailment were summarized and their main problems were pointed out. The mechanism of train derailment was expounded on the basis of system dynamics stability concept. And the energy increment criteria were proposed to evaluate train derailment. By applying the criteria, the calculated results concerning 6 cases of freight train derailment on tangent railway line and 6 cases of freight train derailment on bridge were obtained, which are all in agreement with the practical situation. The safety, comfort and stability results concerning 3 cases of freight train running on bridge were analyzed. In addition, the running speed limits of freight train on the Yanconggou and Donggou bridge in the Beijing-Tonghua railway line of 50km/h and 60km/h, respectively, were proposed. And the running speed of freight train on the Nanjing Yangtze River Bridge can reach 70km/h.

Maintenance and development of the Ural high and its contribution to severe cold wave activities in winter 2020/21

Two successive severe cold waves invaded eastern China from the end of 2020 to early 2021,leading to an extensive,severe,and persistent drop in temperature.The paper investigates the features and formation mechanisms of the two cold waves.The main results are as follows:(1)An anticlockwise turning of the transverse trough was observed in both cold waves.However,a broad ridge was maintained over the Ural area from mid-December 2020 till mid-January 2021.No breakdown or discontinuous westward shift of the blocking high was observed,which is different from typical cold waves in eastern Asia.(2)The maintenance and strengthening of northerly winds in front of the Ural high led to an increase in baroclinicity in-situ.In the downstream region,the gradient of the geopotential height contour in the south of the transverse trough rapidly increased and the advection of cold temperature consistently enhanced and advanced southwards.This in turn caused the intensification and southward expansion of the Siberian high.(3)Energy propagation of the quasi-stationary wave was a reason for the development and persistence of the Ural blocking.Prior to the occurrence of the two cold waves,the energy of the low-frequency stationary wave originating from near 0°E(or even to the west)propagated eastwards,which helped the Ural ridge intensify and maintain.Meanwhile,it also contributed to the development of the trough downstream of the ridge and resulted in the anticlockwise turning of the transverse trough,providing a favorable condition for the southward outbreak of cold air.

三维有挠率引力中的守恒荷

由于引力场的微分同胚不变性,定义能量一直是引力理论中的难题,人们为此发展了一系列方法.本文将Wald基于拉格朗日形式体系构造引力场的准局域能量的方法推广到三维有挠率引力的情形,给出了Mielke-Baekler (MB)模型中的守恒的能量与角动量,并计算了有挠率的BTZ黑洞解的守恒荷.所得结果与基于哈密顿形式体系的方法给出的守恒荷相一致.