Determination of residual stresses in thin sheet titanium aluminide composites

Residual stresses in Ti₃Al/SiC composites have been measured using two methods. The compressive residual stresses in the fibers were inferred from measurements of the change in their length when the matrix was entirely removed by etching. The stresses were found to vary substantially from fiber to fiber. The longitudinal and transverse stresses in the matrix were measured by X-ray diffraction. Repeated measurements were made as the outer layer of alloy was removed by electropolishing as far as the first row of fibers. In one composite of lower fiber volume fraction, the matrix stresses were thus found to be approximately uniform throughout the specimen. In a higher volume fraction material, on the other hand, the matrix stresses increased significantly with depth from the outer surface: the longitudinal matrix stresses among the fibers were found to be about 60 pct larger than they were on the specimen surface. The implications of these measurements for processing and reliability of thin sheet titanium aluminide composites are discussed.     

The published DNA sequence of human cytomegalovirus strain AD169 lacks 929 base pairs affecting genes UL42 and UL43

Compared with the published DNA sequence (M. S. Chee, et al. Curr. Top. Microbiol. Immunol. 154:125-170, 1990), most isolates of human cytomegalovirus strain AD169 contain an additional 929 bp after nucleotide 54612. This results in a changed reading frame for the 5'-terminal 50 codons of gene UL42 and expansion of gene UL43 (a US22 family member) from 187 (3'-truncated) to 423 (full-length) codons. The UL42 and UL43 gene products are nonessential for growth in culture.     

Laser-based ultrasonics on Gr/epoxy composite

Critical issues are examined in the application of laser generation and detection of ultrasound to the inspection of large area air-frame composites. Among these issues are surface roughness, signal-to-noise ratio, insensitivity to the path length between the part and detector, and wide band vs. narrow-band generation. Demonstrated is the feasibility of transmission C-scans of 150 ply Gr/epoxy panels containing simulated delaminations. Waveforms having a signal-to-noise ratio of greater than 40 dB in 15-mm thick Gr/epoxy were obtained with generating laser powers well below the ablation limit for the graphite epoxy. Detection was shot-noise limited with a detector noise figure of about 5–10 dB.     

Applying Hebbian Theory to Enhance Search Performance in Unstructured Social‐Like Peer‐to‐Peer Networks

Unstructured peer‐to‐peer (p2p) networks usually employ flooding search algorithms to locate resources. However, these algorithms often require a large storage overhead or generate massive network traffic. To address this issue, previous researchers explored the possibility of building efficient p2p networks by clustering peers into communities based on their social relationships, creating social‐like p2p networks. This study proposes a social relationship p2p network that uses a measure based on Hebbian theory to create a social relation weight. The contribution of the study is twofold. First, using the social relation weight, the query peer stores and searches for the appropriate response peers in social‐like p2p networks. Second, this study designs a novel knowledge index mechanism that dynamically adapts social relationship p2p networks. The results show that the proposed social relationship p2p network improves search performance significantly, compared with existing approaches.     

Electrodynamic Focusing of Charged Aerosol Particles

An electrodynamic screen for focusing charged particles carried by an airflow stream has been constructed and tested. The screen has the shape of a cone frustum with half-angle of 8° and is 17 cm long. Entrance and exit diameters are 7.0 and 2.5 cm, respectively. Electrodes forming the screen are three 0.71-mm diameter stainless-steel wires configured as a triple-start helix with 2.0-mm pitch. A three-phase power supply drives each wire with a line-to-ground voltage of 2300 V at 350 Hz with a phase difference of 120° between adjacent wires. Test particles of 5.2-μm aerodynamic diameter with electric charge of 1850–6080 elementary units per particle in an aerosol having a mean flow velocity of 4.3×10^?2 m/s parallel to the vertically oriented cone axis are confined and focused with essentially no particle loss. Minimum distance of approach of the test particles to the screen, as found from computer simulation of particle trajectories, solution of the particle equations of motion by linear approximation, and experimental observation, are in good agreement.     

A systematic review of evidence for the appropriateness of neonatal screening programmes for inborn errors of metabolism

The nicotinic antagonist mecamylamine was evaluated in a randomized smoking cessation trial. Four groups of participants (n = 20 per group) received nicotine plus mecamylamine, nicotine alone, mecamylamine alone, or no drug for 4 weeks before cessation. After the quit-smoking date, all subjects received nicotine plus mecamylamine treatment for 6 weeks. Nicotine skin patches (21 mg/24 hr) and mecamylamine capsules (2.5-5.0 mg twice per day) were used. Precessation mecamylamine significantly prolonged the duration of continuous smoking abstinence; abstinence rates at the end of treatment were 47.5% with mecamylamine and 27.5% without mecamylamine. Nicotine + mecamylamine reduced ad lib smoking, smoking satisfaction, and craving more than either drug alone. Moreover, the orthostatic decrease in blood pressure caused by mecamylamine was offset by nicotine. Mecamylamine before smoking cessation may be an effective adjunct to nicotine patch therapy.     

Optimizing image matches via a verification model

In the literature, we have seen a boom in wide‐baseline matching approaches proposed for locating correspondences between images. However, wrong correspondences or the so‐called outliers are still rather inevitable, especially in urban environments with the presence of repetitive structures, and/or a large dissimilarity in viewpoints. In this paper, we propose a verification model to optimize the image matching results by significantly reducing the number of outliers. Several geometric and appearance‐based measurements are exploited, and conditional probability is used to compute the probability of each true correspondence. The model is validated by extensive experiments on images from the ZuBud database, which are taken in different weather conditions, seasons, and with different cameras. It is also demonstrated on a real‐time application of an image‐based navigation system. © 2010 Wiley Periodicals, Inc.