Deformability design of high‐performance concrete beams

The use of high‐performance materials (HPMs) such as high‐strength concrete (HSC) and high‐strength steel (HSS) is becoming more popular in the construction of beams and columns of tall buildings. These HPMs not only increase the stiffness and decrease the strength‐to‐weight ratio, but also provide a more sustainable construction method by minimising the construction materials needed. However, HSC and HSS are more brittle than normal‐strength concrete and steel, respectively. Therefore, it will adversely affect the deformability of concrete beams. To evaluate the pros and cons of adopting HPM in beam design, the author will investigate the flexural strength and deformability of concrete beams made of HPMs. The deformability in this study is expressed in normalised rotation capacity and investigated by a parametric study using nonlinear moment–curvature analysis taking into account the degree of reinforcement, confining pressure, concrete and steel yield strength. From the results, it is evident that the deformability of concrete beams increases as the degree of reinforcement decreases or confining pressure increases. However, the effects of concrete and steel yield strength depend on other factors. For practical design purpose, charts and formulas are produced for designing high‐performance concrete beams to meet with specified flexural strength and deformability requirement. Copyright © 2011 John Wiley & Sons, Ltd.     

Optimization Procedure for Design of High‐Speed Prop‐Rotors

An optimization procedure has been developed to address the complex and conflicting requirements associated with the design of high‐speed proprotor aircraft. Since the key technical issues are maintenance of propulsive efficiency and aeroelastic stability in high‐speed cruise without deteriorating figure of merit in hover, rotor aerodynamic performance and aeroelastic analysis are coupled, inside a closed loop, to the optimizer. The discipline couplings provide actual blade air‐loads, during hover and cruise, and also provide realistic blade designs. The propulsive efficiency in high‐speed cruise is used as the objective function. Constraints are also imposed on the aeroelastic stability in axial flight and the rotor figure of merit in hover. Both structural and planform design variables are used. The optimization procedure yields significant improvements in the aerodynamic characteristics of the rotor. Off‐design performance studies, conducted with the optimum blade, show overall design improvements.     

Theories of dual diagnosis in mental retardation.

Provides a historical review of theory development in the field of dual diagnosis. Dual diagnosis, defined in this instance as the co-occurrence of mental health disorders with mental retardation, has become a major area of clinical practice and research in the past 10 yrs. Whereas areas such as differential diagnosis, assessment, and prevalence have been major focuses of research, etiologies of dual diagnosis have received less attention. Current etiological theories have practical implications for the treatment and prevention of dual diagnoses and suggest important directions for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wafer-scale assembly of highly ordered semiconductor nanowire arrays by contact printing

Controlled and uniform assembly of "bottom-up" nanowire (NW) materials with high scalability presents one of the significant bottleneck challenges facing the integration of nanowires for electronic applications. Here, we demonstrate wafer-scale assembly of highly ordered, dense, and regular arrays of NWs with high uniformity and reproducibility through a simple contact printing process. The assembled NW pitch is shown to be readily modulated through the surface chemical treatment of the receiver substrate, with the highest density approaching approximately 8 NW/mum, approximately 95% directional alignment, and wafer-scale uniformity. Such fine control in the assembly is attained by applying a lubricant during the contact printing process which significantly minimizes the NW-NW mechanical interactions, therefore enabling well-controlled transfer of nanowires through surface chemical binding interactions. Furthermore, we demonstrate that our printing approach enables large-scale integration of NW arrays for various device structures on both rigid silicon and flexible plastic substrates, with a controlled semiconductor channel width ranging from a single NW ( approximately 10 nm) up to approximately 250 microm, consisting of a parallel array of over 1250 NWs and delivering over 1 mA of ON current.     

The impact of delayed differentiation in make-to-order environments

To cope with the challenges of product proliferation, many firms are shifting their supply chain structures from make-to-stock (MTS) to make-to-order (MTO). An MTO strategy comes at a price however, as customers must wait longer for their configured products. Incorporating delayed differentiation (DD) in an MTO environment offers the potential of reducing the customer's waiting time, since the generic part/component of the products is made available before receiving customer orders. In this paper, we quantify the trade-offs involved in implementing DD in an MTO environment using both customer waiting time and system cost as performance metrics. We show that under common conditions, the introduction of DD results in shorter waiting times and higher cost over a pure MTO strategy. These results are as expected. However, we also derive conditions where DD results not only in shorter customer waiting time but also lower cost, thus dominating a pure MTO strategy. Through a simulation experiment, we test the robustness of our results for the case where the customer arrivals and production times are generally distributed. For firms with the capability of estimating the customer waiting cost, we derive the optimal base-stock level of the generic component to minimise the total cost.     

Die Geschichte der San Francisco–Oakland Bay Bridge

The history of the San Francisco–Oakland Bay Bridge. The San Francisco‐Oakland Bay Bridge is an eminent example of american bridge engineering. It consists of a twin suspension bridge and a cantilever truss bridge which are connected by a tunnel through Yerba Buena Island. This article describes the way from the feasibility studies to the present time. In addition, it details some specific design and construction features, for example the steel construction work and the foundation of the central anchorage which connects the two suspension bridges. Recent reinforcement measures, and the plans for the replacement of the East Bay Crossing by a self‐anchored single tower suspension bridge to improve earthquake safety, are also discussed.     

High-performance enhancement-mode thin-film transistors based on Mg-doped In<Subscript>2</Subscript>O<Subscript>3</Subscript> nanofiber networks

Although In₂O₃ nanofibers (NFs) are well-known candidates as active materials for next-generation, low-cost electronics, these NF based devices still suffer from high leakage current, insufficient on–off current ratios (I_on/I_off), and large, negative threshold voltages (V_TH), leading to poor device performance, parasitic energy consumption, and rather complicated circuit design. Here, instead of the conventional surface modification of In₂O₃ NFs, we present a one-step electrospinning process (i.e., without hot-press) to obtain controllable Mg-doped In₂O₃ NF networks to achieve high-performance enhancement-mode thin-film transistors (TFTs). By simply adjusting the Mg doping concentration, the device performance can be manipulated precisely. For the optimal doping concentration of 2 mol%, the devices exhibit a small V_TH (3.2 V), high saturation current (1.1 × 10^–4 A), large on/off current ratio (>10⁸), and respectable peak carrier mobility (2.04 cm²/(V·s)), corresponding to one of the best device performances among all 1D metal-oxide NFs based devices reported so far. When high-κ HfO _x thin films are employed as the gate dielectric, their electron mobility and V_TH can be further improved to 5.30 cm²/(V·s) and 0.9 V, respectively, which demonstrates the promising prospect of these Mg-doped In₂O₃ NF networks for highperformance, large-scale, and low-power electronics.

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