Bearing parameter identification of rotor–bearing system using clustering-based hybrid evolutionary algorithm

A new bearing parameter identification methodology based on global optimization scheme using measured unbalance response of rotor–bearing system is proposed. A new hybrid evolutionary algorithm which is a clustering-based hybrid evolutionary algorithm (CHEA), is proposed for global optimization scheme to improve the convergence speed and global search ability. Clustering of individuals by using a neural network is introduced to evaluate the degree of mature of genetic evolution. After clustering-based genetic algorithm (GA), local search is carried out for each cluster to judge the convexity of each cluster. Finally, random search is adapted for extrasearching to find a potential global candidate, which could be missed in GA and local search. The proposed methodology can identify not only unknown bearing parameters but also unbalance information of disk by simply setting them as unknown parameters. Numerical example and experimental results were used to verify the effectiveness of the proposed methodology.     

Numerical Modeling of Cemented Mine Backfill Deposition

In current underground mining practice, it is common to use tailings, without added cement, to fill mined-out voids (“stopes”). If fine-grained tailings are used, the high placement rates and low permeability can often result in undrained loading conditions and, hence, lower effective stress, when assessed in the conventional manner. Where cement is added, the cement modifies the consolidation characteristics in a number of ways, including increasing the strength and stiffness, reducing the permeability, and inducing volumetric changes associated with the hydration reactions leading to “self-desiccation.” As a result, conventional consolidation-analysis techniques are unsuitable for assessing the behavior. The one-dimensional mine-tailings-consolidation program (MinTaCo) has been modified, and renamed CeMinTaCo, to couple cement hydration with conventional consolidation analysis. The fundamental theory behind the modifications is presented. The model is used to undertake a sensitivity study, which highlights some of the important features of the behavior of cemented backfill, and shows how complex interactions between the various properties produce some outcomes that are counterintuitive.     

An efficient algorithm for superresolution in medium field imaging

In this paper, we study the problem of reconstruction of a high-resolution (HR) image from several blurred low-resolution (LR) image frames in medium field. The image frames consist of blurred, decimated, and noisy versions of a HR image. The HR image is modeled as a Markov random field (MRF), and a maximum a posteriori (MAP) estimation technique is used for the restoration. We show that with the periodic boundary condition, a HR image can be restored efficiently by using fast Fourier transforms. We also apply the preconditioned conjugate gradient method to restore HR images in the aperiodic boundary condition. Computer simulations are given to illustrate the effectiveness of the proposed approach. This research was conducted with support from the Army Research Office Grant DAAD 19-03-1-0261 and the National Science Foundation Grant CCF-0429481. Research supported in part by RGC Grant Nos. 7130/02P, 7046/03P, 7035/04P and 7035/04P and FRG/04-05/II-51.     

Low‐Operating‐Voltage Organic Transistors Made of Bifunctional Self‐Assembled Monolayers

Self‐assembled monolayers (SAMs) are molecular assemblies that spontaneously form on an appropriate substrate dipped into a solution of an active surfactant in an organic solvent. Organic field‐effect transistors are described, built on an SAM made of bifunctional molecules comprising a short alkyl chain linked to an oligothiophene moiety that acts as the active semiconductor. The SAM is deposited on a thin oxide layer (alumina or silica) that serves as a gate insulator. Platinum–titanium source and drain electrodes (either top‐ or bottom‐contact configuration) are patterned by using electron‐beam (e‐beam) lithography, with a channel length ranging between 20 and 1000 nm. In most cases, ill‐defined current–voltage (I–V) curves are recorded, attributed to a poor electrical contact between platinum and the oligothiophene moiety. However, a few devices offer well‐defined curves with a clear saturation, thus allowing an estimation of the mobility: 0.0035 cm² V^–1 s^–1 for quaterthiophene and 8 × 10^–4 cm² V^–1 s^–1 for terthiophene. In the first case, the on–off ratio reaches 1800 at a gate voltage of –2 V. Interestingly, the device operates at room temperature and very low bias, which may open the way to applications where low consumption is required.     

智能屏幕在工业控制中的应用

智能屏幕人机界面的开发人员通过使用闪存和C／C＋＋组件，使产品达到了工业级的可靠性和实时性能。楼宇自动化系统的设计便是一个例子。     

Software Assumptions Lead to Preventable Errors

Undocumented assumptions are often the cause of serious software system failure. Thus, to reduce such failures, developers must become better at discovering and documenting their assumptions. In this article, we focus on common categories of assumptions in software, discuss methods for recognizing when developers are making them, and recommend techniques for documenting them.     

High performance GaAs MESFETs with molecular implanted and optimized lowly-doped drain structure for maximized speed, gain and breakdown performance

GaAs MESFETs with novel lowly-doped drain structures have been developed utilizing molecular implants of silicon trifluoride. Short-channel effects in the 1/4 μm enhancement- and depletion-mode transistors have been suppressed with drain-induced barrier height lowering of less than 70 mV/V and pinch-off voltage shifts of less than 220 mV as the gate length was scaled from 1.0 to 1/4 μm. The 3-terminal breakdown, the transconductance to output conductance ratio, and the unity current gain, cut-off frequency were simultaneously optimized. The E-mode device possessed breakdown of >10 V, G_m · R_ds > 9.5, F_t > 55 GHz, and nominal on-resistance of 2.1 Ω mm while the D-mode device had breakdown >10 V, G_m · R_ds > 6.0, F_t > 45 GHz, and nominal on-resistance of 1.9 Ω mm. These optimized transistors enabled the realization of a variety of low-power digital and high-power mixed signal circuits, using 3-level source-coupled transistor and common-mode logic, such as laser and electro-optic drivers, highly integrated transceivers, multiplexers, demultiplexers, and clock data recover circuits.     

Self‐help housing provision: Production,consumption, accumulation and policy in Atlantic Canada

Self‐help has been a neglected aspect of housing provision in industrialised nations, yet in many locations it accounts for a significant share of new production and can contribute to improved housing circumstances for those whose housing need is not too severe. This paper discusses self‐help housing provision in Atlantic Canada and argues that it reduces the profitability of the residential construction industry and for this and other reasons, self‐help is likely to continue as a major form of production. This paper also evaluates the impact on self‐help of several housing policy options.