美国展望

你认为美国建筑市场未来的发展方向如何?这取决于你关注的是哪个建筑领域。虽然住宅建筑领域仍然存在一些问题,但其他领域却充满生机。     

Structural Features of C–S–H(I) and Its Carbonation in Air—A Raman Spectroscopic Study. Part I: Fresh Phases

The Raman spectra of a series of mechanochemically prepared calcium silicate hydrate samples of type C–S–H(I) with C/S ratios ranging from 0.2 to 1.5 reveal changes in structure with changes in the C/S ratio. These support the model of Stade and Wieker based entirely on the tobermorite structure. The main characteristic feature of the spectra is the Si–O–Si bending vibration at about 670 cm⁻¹. Comparisons with bending frequencies of some known crystalline phases composed of single silicate chains led to an estimation of the mean Si–O–Si angles in the C–S–H(I) phases to be ∼140°. Finite silicate chains (Q²) dominate the structures of the samples at C/S ratios 0.2–1.0, the spectra showing characteristic bands from 1010 to 1020 cm⁻¹. When the samples are measured in air, the spectra exhibit carbonate bands arising from surface carbonation. The ν₁[CO₃] bands obscure the characteristic Raman scattering of silicate units near 1080 cm⁻¹, which is clearly evident in the fresh samples analyzed in closed capillaries. At C/S>1.00, dimers (Q¹) are the main building unit of the silicate anionic structure, with a characteristic band at 889 cm⁻¹. At C/S ratios 1.33 and 1.50, portlandite (Ca(OH)₂) is also observed.     

Passive multiplexing of printed electroluminescent displays

Abstract— A method is required for creating a graphics display, or pixel array, from printed electroluminescent (PEL) display technology and driving it efficiently and cost effectively. The display is made up of a matrix of capacitive light‐emitting display elements which are to be driven by a passive multiplexing method. A four‐level drive system is required in order to produce the best possible contrast ratio on the display. A four‐level drive system is costly to implement at the high voltages at which PEL displays operate, but a system is presented here which is able to make a significant reduction in the amount of electronics required to control the display. By selectively switching the output from a fly‐back power supply to different parts of the matrix display, the optimum voltages can be obtained across all segments from a single high‐voltage power supply. This provides potential for using passive‐matrix PEL displays in a wide variety of applications, as well as having possible applications for other display technologies such as PDLCs (see demonstration in Fig. 1).     

Did the Stern Review underestimate US and global climate damages?

The Stern Review received widespread attention for its innovative approach to the economics of climate change when it appeared in 2006, and generated controversies that have continued to this day. One key controversy concerns the magnitude of the expected impacts of climate change. Stern's estimates, based on results from the PAGE2002 model, sounded substantially greater than those produced by many other models, leading several critics to suggest that Stern had inflated his damage figures.     

2009年移动短信息业务9大预测

有一位智者曾经说过：“预测未来实际上是一门如何合理看待现在的艺术”。对于整个移动行业来说,2009年,由于严重的金融危机,毫无疑问将是非常艰苦的一年。但是,移动短信息业务的发展不在此例。     

Invariance and convergent and discriminant validity between mothers' and fathers' ratings of oppositional defiant disorder toward adults, ADHD-HI, ADHD-IN, and academic competence factors within Brazilian, Thai, and American children.

Confirmatory factor analysis was used to test the invariance of an oppositional defiant disorder toward adults, attention-deficit/hyperactivity disorder-hyperactivity/impulsivity, attention-deficit/hyperactivity disorder-inattention, and an Academic Competence factor model between mothers' and fathers' ratings within Brazilian (n = 894), Thai (n = 2,075), and American (n = 817) children with the Child and Adolescent Disruptive Behavior Inventory (G. L. Burns, T. Taylor, & J. Rusby, 2001a, 2001b). The results showed invariance of item loadings, intercepts, and residuals, as well as factor variances, covariances, and means between mothers' and fathers' ratings within each sample. Convergent and discriminant validity was also observed for the between-parent factor correlations, thus providing additional support for the construct validity of the Child and Adolescent Disruptive Behavior Inventory. The confirmatory factor analysis invariance procedure provides a much better way to examine between-source ratings of behavior problems in children than do the simple correlation and raw discrepancy score procedures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High-performance and cost-effective membrane electrode assemblies for advanced proton exchange membrane water electrolyzers: Long-term durability assessment

Improved activity and durability performance of a two-cell (86 cm²) proton exchange membrane water electrolyzer (PEMWE) stack is reported for the first time. Both membrane electrode assemblies (MEAs) contain one order of magnitude lower platinum group metal (PGM) loadings compared to the state-of-the-art PEMWEs and incorporate novel Pt recombination layers. The high-performance and cost-effective MEAs are fabricated by the unique reactive spray deposition technology (RSDT). This advanced methodology allows for one-step fabrication of MEAs and ensures precise control and distribution of the catalyst composition and loading. The RSDT-fabricated MEAs contain only 0.2 and 0.3 mg_PGM cm^?2 loading in the cathode and anode electrodes, respectively, and demonstrate excellent activity and durability for over 3000 h of operation at industrially-relevant operating conditions without showing significant loss in performance. This novel work shows that a significant cost reduction for PEMWEs is achieved while maintaining excellent durability, high catalysts activities, and low hydrogen cross-over.