X-ray microbeam transmission/fluorescence method for non-destructive characterization of tungsten coated carbon materials

Tungsten erosion, its subsequent transport and redeposition are of great interest, because a full tungsten divertor is foreseen to be used during the deuterium–tritium operational phase of ITER. The erosion of tungsten and carbon marker layers was extensively studied in the outer divertor of ASDEX Upgrade (AUG), and work is currently in progress to completely replace the existing JET CFC tiles with tungsten-coated tiles within the JET ITER-like wall project. The need for fast and non-destructive method which allows the quantitative determination of the thickness of a tungsten coating on a carbon material on large areas led us to evaluate a combined absorption/fluorescence X-ray (XRTF) technique. The method can provide fast analysis, high spatial resolution and a material selective detection of deposited layers and inclusions. It was applied on W coated fine grain graphite (FGG) tiles from AUG's divertor. It is proved that the method is able to provide information about the uniformity of the tungsten coating on a graphite or CFC substrate whilst the technique can be used to determine the thickness of the tungsten and other marker materials coatings. It represents a unique instrument for the post-mortem analysis of the coatings.     

Cure studies and thermal stability of an acetylene-functionalized polyphenylene resin

Summary Samples of an acetylene-functionalized polyphenylene resin have been thermally cured to determine the effects on char yield and thermooxidative stability. The material's lack of a processing window led to difficulties in handling; it was found that quickly heating small samples above the melting point resulted in complete polymer melting prior to resolidification due to cure. Curing in air and in an inert atmosphere led to decreases and increases in char yields, respectively, at 900°C. Char yields in excess of 90 weight % were obtained at 900°C. The thermooxidative stability of the cured polymer was slightly better than that of the uncured resin, with the biggest improvement being in the 200–400°C range.     

Development of metal supported solid oxide fuel cells for operation at 500–600 °C

A novel metal-supported solid oxide fuel cell has been developed that is capable of operating at temperatures of 500–600 °C. The rationale behind the materials used to construct this fuel cell type is given, and results are presented from cell testing on hydrogen and reformed natural gas, including durability trials of some 2500 h duration. This new fuel cell variant is shown to be tolerant of carbon monoxide, durable, robust to thermal and redox cycling, and capable of delivering technologically relevant power densities. This paper was presented at the Fuel Cells: Materials, Processing, and Manufacturing Technologies Symposium sponsored by the Energy/Utilities Industrial Sector & Ground Transportation Industrial Sector and the Specialty Materials Critical Technologies Sector at the ASM International Materials Solutions Conference, October 13–15, 2003, in Pittsburgh, PA. The symposium was organized by P. Singh, Pacific Northwest National Laboratory, S.C. Deevi, Philip Morris USA, T. Armstrong, Oak Ridge National Laboratory, and T. Dubois, U.S. Army CECOM.     

A Bench‐Scale Study of Conditioning Behaviour in Oil Sands Slurries

Proper conditioning of an oil sand/water slurry is essential for the efficient extraction of bitumen. The conditioning process depends on such variables as ore grade, temperature, mixing intensity, mixing time, and water composition. A technique has been developed in which a microscope and video cameras are used to observe a slurry stirred in a glass cell to evaluate, on a comparative basis, the effect of conditioning parameters on bitumen recovery. Several ores and their blends were studied and found to exhibit large differences in their conditioning behaviour. The method offers the capability of diagnosing ore processability problems and optimizing slurry conditioning.     

Flavonoid content and antioxidant capacity of spinach genotypes determined by high‐performance liquid chromatography/mass spectrometry

BACKGROUND: Flavonoids in different spinach genotypes were separated, identified, and quantified by a high‐performance liquid chromatographic method with photodiode array and mass spectrometric detection. The antioxidant capacities of the genotypes were also measured using two antioxidant assays–oxygen radical absorbance capacity (ORAC_FL) and photochemiluminescence (PCL)–which measure the response to the peroxyl and superoxide anion radicals, respectively. RESULTS: Eighteen flavonoids representing glucuronides and acylated di‐ and triglycosides of methylated and methylene dioxide derivatives of 6‐oxygenated flavonols were identified (patuletin, spinacetin, spinatoside, jaceidin). The total flavonoids ranged from 1805 to 3703 mg kg^?1, indicating 2.0‐fold variation among genotypes. The ORAC_FL and PCL values ranged from 48.7 to 84.4 mmol kg^?1 and from 9.0 to 14.0 mmol kg^?1, respectively, representing as much as 1.7‐fold variation among genotypes. CONCLUSION: The ORAC_FL and PCL values were highly correlated with total flavonoid content (r_xy = 0.96). Copyright © 2008 Society of Chemical Industry     

Recent Advances on Vibration Control of Structures Under Dynamic Loading

In this paper, a review of recent journal articles on passive, active, semi-active, and hybrid vibration control of structures subjected to dynamic loading is presented. Passive systems reviewed include tuned mass damper (TMD), tuned liquid column damper (TLCD), tuned liquid column ball damper (TLCBD), circular TLCD (CTLCD), and pendulum TLCD (PTLCD). Active control systems include active tuned mass dampers (ATMD) and piezoelectric actuators. Semi-active systems include magnetorheological (MR) damper, negative stiffness devices (NSD), magneto-rheological damper TMD (MR-TMD), variable stiffness semi-active TMD (VS-STMD), variable damper STMD (VD-STMD), and recentering variable friction device (RVFD). Hybrid systems include active base isolation system and semi-active MR dampers with nonlinear base isolators. The current frontier of research is semi-active control of structures as well hybridization of various control systems. The problem is complex requiring integration of several different hardware and software technologies with structural design such as smart materials, adaptive dampers, actuators, sensors, and control and signal processing algorithms. This complexity also makes it an exciting area of research and development.     

Phthalonitrile‐epoxy blends: Cure behavior and copolymer properties

Binary blends composed of 4,4′‐bis(3,4‐dicyanophenoxy)biphenyl (biphenyl PN) and diglycidyl ether of bisphenol A (epoxy resin) and oligomeric n = 4 phthalonitrile (n = 4 PN) and epoxy resin were prepared. The cure behavior of the blends was studied under dynamic and isothermal curing conditions using differential scanning calorimetry, simultaneous thermogravimetric/differential thermal analysis, infrared spectroscopy, and rheological analysis. The studies revealed that phthalonitrile‐epoxy blends exhibited good processability and that they copolymerized with or without the addition of curing additive. In the absence of curing additive, the blends required higher temperatures and longer cure times. The thermal and dynamic viscoelastic properties of amine‐cured phthalonitrile‐epoxy copolymers were examined and compared with those of the neat epoxy resin. The properties of the epoxy resin improved with increasing biphenyl PN content and with n = 4 PN addition. Specifically, the copolymers exhibited higher glass transition temperatures, increased thermal and thermo‐oxidative stabililty, and enhanced dynamic mechanical properties relative to the commercially available epoxy resin. The results showed that the phthalonitrile‐epoxy blends and copolymers have an attractive combination of processability and high temperature properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

VoIP保护的重要性

VoIP(语音IP)或互联网电话技术是指通过互联网(而非公共交换电话网络,亦即PSTN)传送的通信服务--语音、传真和/或语音、信息应用.     

Analysis of pore structure,contact angle and pore entrapment of blended cement pastes from mercury porosimetry data

The mercury intrusion porosimetry (MIP) was used to investigate the pore structure characteristics of fly-ash cement pastes with two water to binder ratios (w/b = 0.3, 0.5). The total porosity, pore fraction distribution, contact angle hysteresis and the pore entrapment are quantified from the intrusion/extrusion data. The tortuosity of pore structure is further calculated from pore entrapment. The results show: (1) the w/b ratio is determinant for the formation of pore structure patterns, high w/b ratio providing high porosity, high connectivity but low pore surface roughness to pore structure; (2) the contact angle hysteresis can be related to pore surface roughness, the hysteresis factor α_θ attaining respectively 0.42, 0.75 for Paste I (w/b = 0.5) and Paste II (w/b = 0.3) samples at 180 d; (3) the tortuosity and the porosity obey just roughly the power law and more pore characteristics are needed to describe the tortuosity of blended cement pastes.     

Cascode Configurations for Switched Current Copiers

Various cascode circuits are investigated with regard to their suitability for switched current copier applications. A generalized circuit representation for cascodes is introduced and different cascode circuits are compared with respect to their small-signal parameters as well as their associated dynamic output ranges. A method called reference voltage and current tracking for dynamic output range improvement is proposed. An improved regulated cascode circuit with extended dynamic output range using reference current tracking and level shifting technique is presented. The dynamic output ranges of cascode circuits used in switched current copiers are discussed in detail and the corresponding saturation operating areas are compared. The results are applied to typical switched-current circuits and the use of cascodes in switched-current applications with cascaded current copier cells is investigated.