Feedback linearization control of the looper system in hot strip mills

This paper studies on the linearization of a looper system in hot strip mills, that plays an important role in regulating a strip tension or a strip width. Nonlinear dynamic equations of the looper system are analytically linearized by a static feedback linearization algorithm with a compensator. The proposed linear model of the looper is validated by a comparison with a linear model using Taylor’ s series. It is shown that the linear model by static feedback well describes nonlinearities of the looper system than one using Taylor’ s series. Furthermore, it is shown from the design of an ILQ controller that the linear model by static feedback is very useful in designing a linear controller of the looper system.     

基于复杂辐射状配电系统简约模型的可靠性评估算法

建立了一种配电网简约模型，提出了开关节点和负荷区间等概念以及适用于复杂辐射状配电系统的可靠性评估算法。该算法只需考虑开关节点和负荷区间对故障的影响，不需具体到系统各个元件，通过遍历搜索分析故障事件的影响、评估其可靠性。对于分支馈线较多的配电系统，该算法在原理和编程上具有优势，且能计及开关故障、备用电源和计划检修等多种情况。利用C++语言计算RBTS母线6系统 的可靠性指标，验证了该算法的正确性和有效性     

A numerical investigation of the flow between rotating conical cylinders of two different configurations

The flow between two coaxial conical cylinders is numerically studied for two different configurations, with the inner cone rotating and the outer one at rest. It is found that, in one configuration,at least at a small Reynolds number（Re）, the pressure is a decreasing function of z while in the other configuration, it is an increasing function of z. In the first configuration, the pressure curves for different Re have intersections, while in the second configuration they do not. The gap between two conical cylinders is filled with six pairs of Taylor vortices at about the same Reynolds number and in each pair of vortices in the first configuration, the upper vortex is larger than the bottom one while in the second configuration, the bottom vortex is larger than the upper one.     

The Pathology of Cryptology—A Current Survey

Abstract

“The Pathology of Cryptology” is the title of a chapter in David Kahn's book The Codebreakers. This chapter mainly deals with hidden messages, which amateur scientists claim to have discovered in the works of William Shakespeare and in other literary works. The present article picks up this subject and provides it with a theoretic framework under the name of “para-steganography.” Moreover, further case studies are added to those given by Kahn, including many examples that only became known after the publication of The Codebreakers. These considerations show that a hidden code can be found almost anywhere, provided that one looks for it in a suitable manner.     

同轴套管间涡旋流动及强化传热数值模拟

相对旋转两同轴套管间的涡旋流动,能够带来二次流强化传热传质作用,在航空、水处理、生态保护、生物工程和膜分离等领域都具有广泛的应用价值。本文使用Fluent软件,对同轴套管间涡旋流动及传热特性进行数值模拟,考察了内管转速、内外管壁面温差等操作参数变化对同轴套管间流体传热性能的影响,分析了涡旋流动与传热效率之间的关联关系。模拟结果表明:内管转速增加在流场中形成泰勒涡,涡流扰动增大了高温壁面与流体间的热流密度,增强了流体传热效率。增大内外管壁面温差,也可加强流体传热性能,但其强化作用不及内管转速的强化作用显著。受流场中泰勒涡影响,流体速度、温度及热流密度沿轴向的分布都呈正弦状周期性波动,在相邻两涡交界面处,流体传热性能最好,在涡中心处的传热性能最差。     

Task-space control of robots using an adaptive Taylor series uncertainty estimator

An uncertainty estimation and compensation can improve the performance of control systems due to structured and unstructured uncertainty. This paper presents a robust task-space control approach using an adaptive Taylor series uncertainty estimator for electrically driven robot manipulators. It is worth noting that not only the lumped uncertainty is estimated and employed in the indirect form of robust controller, but also the upper bound of approximation error is estimated to form a robustifying term and the asymptotic convergence of tracking error and its time derivative are proven based on stability analysis. Finally, the effectiveness of the proposed controller is shown through simulation and comparison with two valuable control schemes applied on the Selective Compliance Assembly Robot Arm (SCARA) robot manipulator.     

一种新的自适应边缘提取微分算子

提出一种新的微分算子用于边缘提取,基于泰勒展开分别计算图像水平和竖直方向的灰度差分,相比传统一阶或二阶微分算子,其梯度值结果更精确,弥补了传统算子微弱边缘提取少且与原图逼近度较差的缺陷。然后基于大津法思想对图像梯度幅值直方图计算分割阈值,从而得到一种新的能自适应提取边缘的微分算子。仿真结果表明,新算子不仅能够对不同图像自适应提取边缘,并且相比传统微分算子,它能提取更多微弱边缘,尤其对灰度对比度较低的图像。同时对曲线部分具有较好的逼近效果,适用于人脸等线条细节比较丰富的图像。将新算子应用到Canny算子中能获取更精确的结果。     

A qualitative computational study of mass transfer in upward bubble train flow through square and rectangular mini-channels

In this paper we present a new method for numerical simulation of conjugate mass transfer of a dilute species with resistance in both phases and an arbitrary equilibrium distribution coefficient. The method is based on the volume-of-fluid technique and accounts for the concentration jump at the interface by transforming the discontinuous physical concentration field into a continuous numerical one. The method is validated by several test problems and is used to investigate the mass transfer in upward bubble train flow within square and rectangular channels. Computations are performed for a single flow unit cell and a channel hydraulic diameter of 2 mm. The simulations consider the transfer of a dilute species from the dispersed gas into the continuous liquid phase. Optionally, the mass transfer is accompanied by a first-order homogeneous chemical reaction in the liquid phase or a first-order heterogeneous reaction at the channel walls. The results of this numerical study are qualitative in nature. First, because periodic boundary conditions in axial direction are not only used for the velocity field but also for the concentration field and second, because the species diffusivity in the liquid phase is arbitrarily increased so that the liquid phase Schmidt number is 0.8 and the thickness of the concentration and momentum boundary layer is similar. Two different equilibrium distribution coefficients are considered, one where the mass transfer is from high to low concentration, and one where it is vice versa. The numerical study focuses on the influence of the unit cell length, liquid slug length and channel aspect ratio on mass transfer. It is found that for the exposure times investigated the liquid film between the bubble and the wall is saturated and the mass transfer occurs by the major part through the bubble front and rear so that short unit cells are more efficient for mass transfer. Similar observations are made for the homogeneous reaction and for the heterogeneous reaction when the reaction is slow. In case of a fast heterogeneous reaction and when the main resistance to mass transfer is in the gas phase, it appears that for square channels long unit cells are more efficient, while large aspect ratio rectangular channels are more efficient than square channels, suggesting that for these conditions they might be more appropriate for use in monolithic catalysts.     

Culture and psychotherapy: Toward a hermeneutic approach.

Outlines a hermeneutic model of the self and its relationship to culture based on an integration of the hermeneutic work of M. Heidegger, H. Gadamer, and C. Taylor, and the cultural anthropologist C. Geertz. The author begins by first summarizing a hermeneutic theory of culture. Next, how the reigning Western understanding of the person, ontological individualism, makes it difficult to grasp how thoroughly people are shaped by culture is examined. The author then turns to Heidegger's notion of "being-in-the-world" as an alternative non-Cartesian ontology of the human agent that compliments an interpretive view of culture. Also addressed is Taylor's claim that culture is a moral framework that orients us to the good. The author then explores how the hermeneutic notion of dialogue can provide a framework for engaging with those from different cultural backgrounds. Finally, these concepts are applied to a cross-cultural case study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimation of evaporative fraction and evapotranspiration from MODIS products using a complementary based model

We present a new formulation to derive evaporative fraction (EF) and evapotranspiration (ET) maps from remotely sensed data without auxiliary relationships or site-specific relationships. This formulation is based on Granger's complementary relationship and Priestley-Taylor's equation. The proposed model eliminates the wind function and resistance parameters commonly applied to ET calculation by including a relative evaporation parameter (ET/Epot). By combining this relative evaporation parameter, Granger's complementary relationship and Priestley-Taylor equation, we obtain a simple equation to estimate ET. We tested and validated the proposed formulation over the Southern Great Plains (SGP) region of the United States for seven clear sky days during March-October 2003. MODIS Atmospheric and Land products were the only source of data used in this study. Estimates of ET show an overall root mean square error and bias of 33.89 and − 10.96 Wm^− 2, respectively. Our results suggest that the proposed approach is robust and valid for a wide range of atmospheric and surface conditions.