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 Unassisted, Low Trigger-, and High Holding-Voltage SCR (uSCR) for On-Chip ESD-Protection Applications

A new silicon-controlled rectifier (SCR) is proposed and realized in a 0.35-mum/3.3-V fully salicided BiCMOS process for electrostatic-discharge (ESD) applications. Without using an external trigger circuitry, the unassisted SCR has a trigger voltage as low as 7 V to effectively protect deep-submicrometer MOS circuits, a holding voltage higher than the supply voltage to minimize transient influence and avoid latch-up issue, and a second snapback current density exceeding 60 mA/mum to provide robust ESD-protection solutions.     

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.     

Anti-windup controller design using linear parameter-varying control methods

In this paper, we seek to provide a systematic anti-windup control synthesis approach for systems with actuator saturation within a linear parameter-varying (LPV) design framework. The closed-loop induced L2 gain control problem is considered. Different from conventional two-step anti-windup design approaches, the proposed scheme directly utilizes saturation indicator parameters to schedule accordingly the parameter-varying controller. Hence, the synthesis conditions are formulated in terms of linear matrix inequalities (LMIs) that can be solved very efficiently. The resulting gain-scheduled controller is non-linear in general and would lead to graceful performance degradation in the presence of actuator saturation non-linearities and linear performance recovery. An aircraft longitudinal dynamics control problem with two input saturation non-linearities is used to demonstrate the effectiveness of the proposed LPV anti-windup scheme.     

Integrating DANP and modified grey relation theory for the selection of an outsourcing provider

Globalization has inevitably forced firms to pursue outsourcing as a strategy to reduce operating costs and improve their competitiveness in the global marketplace. However, a successful outsourcing activity depends on the selection of the appropriate provider. Unlike previous multiple criteria decision-making (MCDM) methods that assume the criteria are independent, we propose a novel hybrid model, combining a Decision Making Trial and Evaluation Laboratory (DEMATEL) and Analytical Network Process (ANP) method called DANP, which addresses the dependent relationships between the various criteria to better reflect the real-world situation. At the same time, instead of ranking the alternatives, we apply a modified grey relation method to select and improve the criterion-gaps to the aspiration levels. To demonstrate the usefulness and effectiveness of the proposed model, we use data from a Taiwanese company.     

Highly efficient upconverters for multiphoton fluorescence microscopy

A new generation of efficient two-photon absorbing fluorescent molecules has been developed and used effectively for two-photon laser scanning microscopy. Several examples of the use of these new fluorophores have been presented. In addition, issues relating to the two-photon absorption cross-section, excitation power, sample properties and resolution in two-photon laser scanning microscopy are discussed.     

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.     

Effects of Impact Inertia and Surface Characteristics on Deposited Polymer Droplets in Microcavities

Microflow visualization and computational fluid dynamics (CFD) are complementarity performed to study the evolution of a single poly(ethylenedioxythiophene) (PEDOT) droplet ejected from a piezoelectric ink-jet printhead and the equilibrium film characteristic of the droplet deposition in a microfabricated cavity. The verified CFD code is further applied to investigate the influences of contact angles thetas_s of the PEDOT droplet/air interface and the PEDOT droplet/cavity sidewall interface as well as droplet impact velocity Vd on the transient deposition process in the micro cavity. Impact inertia was studied by varying the droplet Weber number from 30.3 to 42.6. The surface characteristics are explored by choosing thetas_s of 10deg, 30deg, 50deg, 70deg, 90deg, and 110deg. The influences of impact inertia are also examined by increasing Vd from 2.0 to 12.0 m/s at 2.0 m/s interval. The computed results are found in good agreement with the experimental ones. For the first time, critical Weber numbers have been found relating to the ability of the droplet to wet the side walls and fill a microcavity with a uniform film. The results are also new in terms of the identifications of the critical contact angle (thetas_s)_C and critical impact velocity (Vd)_c. At (thetas_s)_C and at and beyond (Vd)_c, the formation of an intact flat film in the cavity is fulfilled.