高位箱管路结构对成纸定量波动的影响

1 问题提出 长网纸机的定量波动,不仅影响纸机抄造情况的稳定,更重要的是影响产品质量,因定量超差所造成的产品降等影响一等品率,也造成很大的经济损失。因此。

排渣阀漏气引起纸张定量波动的分析与处理

纸浆经过粗选和精选以后,仍然可能含有少量纤维束、细砂粒和金属颗粒等其他杂质,必须进行净化排除,以减少纸浆中尘埃,避免在纸页成形时造成孔洞、黏结等缺陷。

高位箱管路结构对成纸定量波动的影响

长网纸机的定量波动,不仅影响纸机抄造情况的稳定,更重要的是影响产品质量,因定量超差所造成的产品降等影响一等品率,也造成很大的经济损失.因此,在现有条件下,不增加投入,通过工艺、设备、操作、制度等方面加以改造和完善,降低纸机的定量波动,提高纸机一等品率,增加经济效益,是非常必要的.

铜版原纸的匀度和定量波动问题及其解决方法的研究

目前,国产铜版原纸的匀度差较大和定量不一的问题,关键在供浆系统。流浆箱等方面技术落后,不能适应铜版原纸生产的需要。为了解决这些问题,进行了模拟试验,采用的低速纸机敞开式流浆箱模型以方锥总管及阶梯扩散器作为布浆整流元件,采用稳流室和后墙溢流,供浆系统采用带阻尼装置的 CT 稳浆箱。试验结果表明,试验模型采用的阶梯扩散器和稳流室具有较好的布浆、整流效果,后墙溢流可以除去一部分泡沫,一些优化方案具有良好的流态和分布均匀的堰口喷浆速度。供浆系统采用的 CT 稳浆箱有较好地消除供浆脉动的作用。根据优化方案设计制造的流浆箱样机在生产厂(如云南云丰造纸厂、广东江门造纸厂)的生产试验表明,以方锥总管、阶梯扩散器和短堰池代替单管进浆、翻浆隔板的旧式敞开式流浆箱和在供浆系统中用 CT 稳浆箱代替普通稳浆箱的改造是可行的,成纸的匀度好,纵横向定量波动分别控制在0.5%和2%,对解决铜版原纸匀度差和定量不一是有效的。

图像扫描波动性定量标准及分形扫描矩阵的快速生成

在图像扫描技术中 ,首要的问题是如何尽量减小生成数据的波动性。本文在深入研究各种扫描技术的基础上 ,定义了一种描述扫描产生数据波动性的度量指标 ,基于图像存在局部连续性 ,证明了 Hilbert分形曲线扫描优于其他传统扫描 ,表明其生成数据的最佳连续特性 ,并通过实验分析了图像扫描方式对 DCT变换编码效果的影响。最后 ,给出了一个构造 Hilbert扫描矩阵的快速算法。

纸张定量波动的测定和控制途径

叙述了纸张定量、定量波动的定义,重点介绍了纸张定量的测定方法及产生纸张定量波动的主要原因。最后介绍了对定量波动的情况以及控制纸张定量波动的有效方法。

霍尼韦尔4000系列扫描架故障案例

霍尼韦尔的4000型扫描架在很多纸厂都有使用,长时间运行,受环境、备件寿命、维护保养不到位等因素的影响,其稳定性变差,会出现许多故障影响到正常使用。文中介绍了一例给扫描头供电的±15 v开关电源运行不稳定引起的定量和水分频繁且大幅波动的故障案例。通过对此次故障维修经过和总结的描述,分别进行了background测试、reference测试结果对比方法,放射源衰减后定量放大板放大倍数的调整方法,以及类似故障的维修思路和解决方法。

流浆箱稀释水调节装置

目前，流浆箱所使用的稀释水通常为系统中的白水，其中含有大量的细小纤维、填料等物质，如果直接作为稀释水加入流浆箱的稀释水管内，易形成气泡，气泡破裂会造成纸浆均匀度较差，而且由于泵送白水流量不稳定所造成的横幅定量波动，影响在线纸张横幅定量的均匀度，进而降低成纸的质量。因此，针对现有技术中的不足，亟需提供一种自动调节横幅、确保成品纸横幅均一性的流浆箱稀释水调节装置。

REAL-TIME THREE-DIMENSIONAL ECHOCARDIOGRAPHY FOR QUANTIFYING LEFT VENTRICULAR MASS

To test the accuracy of real-time three-dimensional echocardiography (RT3DE) imaging system for evaluating left ventricular mass (LVM) in phantom and excised canine heart. Methods Ten left ventricular (LV) wall phantoms made of two rubber-bursas, ten excised canine hearts underwent RT3DE and two-dimensional echocardiography (2DE). In RT3DE "full volume" imaging, the myocardial volume was mea-sured using 2,4,8, and 16-plane method with the analysis software of RT3DE. Mass was then calculated by multiplying the resulting myocardial volume by specific density of myocardial tissue. In 2DE the masses were measured by area-length meth-od. The true LV wall phantom mass was measured by water displacement and the canine LVM was weighed by anatomy, which served as a reference standard. We compared RT3DE or 2DE with true mass. Results In LV wall phantoms, RT3DE correlated with true masses strongly (r = 0.813-0.994) and weakly correlated between 2DE and true masses (r = 0.628). In excised canine hearts, there is an excellent correlation between RT3DE and true masses (r = 0.764-0.991), while 2DE value showed a lesser correlation (r = 0.514). There are no difference between RT-3DE and true masses (P > 0.05) but different between 2DE and true masses (P < 0.05). In different planes, there was no difference between 8-plane and 16-plane (P > 0.05) but different between 8-plane and 2, 4-plane (P < 0.05). Conclusion RT3DE can accurately quantify LVM and provide a new tool to evaluate LV function. For LVM by RT3DE, 8-plane measurement method is the best choice for accuracy and convenience.

QUANTITATIVE ASSESSMENT OF MYOCARDIAL PERFUSION DEFECTS WITH REAL-TIME THREE-DIMENSIONAL MYOCARDIAL CONTRAST ECHOCARDIOGRAPHY

Objective To evaluate the feasibility and accuracy of measurement of myocardial perfusion defects with intravenous contrast-enhanced real-time three-dimensional echocardiography (CE-RT3DE). Methods RT3DE was performed in 21 open-chest mongrel dogs undergoing acute ligation of the left anterior descending artery (LAD, n=14) or distal branch of the left circumflex artery (LCX, n=7). A perfluorocarbon microbubble contrast agent was injected intravenously to assess the resulting myocardial perfusion defects with Philips Sonos-7500 ultrasound system. Evans blue dye was injected into the occluded coronary artery for subsequent anatomic identification of underperfused myocardium. In vitro anatomic measurement of myocardial mass after removal of the animal’s heart was regarded as the control. Blinded off-line calculation of left ventricular mass and perfusion defect mass from RT3DE images were performed using an interactive aided-manual tracing technique.Results Total left ventricular (LV) myocardial mass ranged from 38.9 to 78.5 (mean±SD: 60.0±10.1) g. The mass of perfusion defect ranged from 0 to 21.4 (mean±SD: 12.0±5.0) g or 0 to 27% of total LV mass (mean±SD: 19%±6%). The RT3DE estimation of total LV mass (mean±SD: 59.8±9.9 g) strongly correlated with the anatomic measurement (r=0.98; y=2.01+0.96x). The CE-RT3DE calculation of the mass of underperfused myocardium (mean±SD: 12.3±5.3 g) also strongly correlated with the anatomic measurement (r=0.96; y=-0.10+1.04x) and when expressed as percentage of total LV mass (r=0.95; y=-0.20+1.04x). Conclusions RT3DE with myocardial contrast opacification could accurately estimate underperfused myocardial mass in dogs of acute coronary occlusion and would play an important role in quantitative assessment of myocardial perfusion defects in patients with coronary artery disease.

Detailed string stability analysis for bi-directional optimal velocity model

The class of bi-directional optimal velocity models can describe the bi-directional looking effect that usually exists in the reality and is even enhanced with the development of the connected vehicle technologies. Its combined string stability condition can be obtained through the method of the ring-road based string stability analysis. However, the partial string stability about traffic fluctuation propagated backward or forward was neglected, which will be analyzed in detail in this work by the method of transfer function and its H∞ norm from the viewpoint of control theory. Then, through comparing the conditions of combined and partial string stabilities, their relationships can make traffic flow be divided into three distinguishable regions, displaying various combined and partial string stability performance. Finally, the numerical experiments verify the theoretical results and find that the final displaying string stability or instability performance results from the accumulated and offset effects of traffic fluctuations propagated from different directions.

Unsteady Flow Characteristic of Low-Specific-Speed Centrifugal Pump under Different Flow-Rate Conditions

To investigate the unsteady flow characteristics in centrifugal pump, the flow field in a low-specific-speed centri- fugal pump with complex impeller is numerically simulated under different conditions. The RNG r-e turbulence model and sliding mesh are adopted during the process of computation. The results show that the interaction be- tween impeller and volute results in the unstable flow of the fluid, which causes the uneven distribution of pres- sure fluctuations around the circumference of volute. Besides the main frequency and its multiple frequency of pressure fluctuations in the centrifugal pump, the frequency caused by the long blades of complex impeller also plays a dominant role in the low-frequency areas. Furthermore, there exists biggish fluctuation phenomenon near the tongue. The composition of static pressure fluctuations frequency on the volute wall and blade outlet is similar except that the fluctuation amplitude near the volute wall reduces. In general, the different flow rates mainly have influence on the amplitude of fluctuation frequency in the pump, while have little effect on the frequency compo- sition.

UNIFORM DECAY RATE FOR THE TRANSMISSION WAVE EQUATIONS WITH VARIABLE COEFFICIENTS

This paper considers the stabilization of the transmission problem of wave equations with variable coefficients. By introducing both boundary feedback control and distribute feedback control near the transmission boundary, the author establishes the uniform energy decay rate for the problem.