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51.
Ming-Jen Pan Patricia A. Hoffman David J. Green John R. Hellmann 《Journal of the American Ceramic Society》1997,80(3):692-698
The spontaneous microcracking of particulate TiB2 –SiC composites is studied as a function of TiB2 volume fraction. The degree of microcracking was examined by measuring elastic properties from room temperature to 1300°C. The results showed that only one composition contains microcracks. All other compositions did not microcrack regardless of TiB2 volume fraction. This was attributed to the difference in the sintering aids. In particular, the Al2 O3 sintering aid needed in these compositions had reacted with SiO2 to form an amorphous grain boundary phase that allowed residual stresses to relax by viscous flow at moderate to high temperatures. The existence of this amorphous grain boundary phase was directly observed by transmission electron microscopy. 相似文献
52.
Thao P. Nghiem Kiki Maulana Kinh Nguyen David Green Agustinus Borgy Waluyo David Taniar 《Journal of Parallel and Distributed Computing》2014
The increasing use of mobile communications has raised many issues of decision support and resource allocation. A crucial problem is how to solve queries of Reverse Nearest Neighbour (RNN). An RNN query returns all objects that consider the query object as their nearest neighbour. Existing methods mostly rely on a centralised base station. However, mobile P2P systems offer many benefits, including self-organisation, fault-tolerance and load-balancing. In this study, we propose and evaluate 3 distinct P2P algorithms focusing on bichromatic RNN queries, in which mobile query peers and static objects of interest are of two different categories, based on a time-out mechanism and a boundary polygon around the mobile query peers. The Brute-Force Search Algorithm provides a naive approach to exploit shared information among peers whereas two other Boundary Search Algorithms filter a number of peers involved in query processing. The algorithms are evaluated in the MiXiM simulation framework with both real and synthetic datasets. The results show the practical feasibility of the P2P approach for solving bichromatic RNN queries for mobile networks. 相似文献
53.
P.K. Abdul Azis I.A. Al-Tisan M.A. Daili T.N. Green A.G.I. Dalvi M.A. Javeed 《Desalination》2003,154(3):291-302
As on land, plants are the real producers in the sea, and on them depend all marine living resources and the basic sustainability of ecosystems. Primary production is performed by chlorophyll-bearing plants ranging from the tiny phytoplankton to the giant kelps through the process ofphotosynthesis. Zooplankton play an important role as secondary producers, and together with phytoplankton they support the vast assemblages of marine food chain with all their diversity and complexity. Data on chlorophyll pigments, phytoplankton and zooplankton are regarded as a sound basis for environmental appraisal of ecosystems. This paper presents a set of data collected from the Saudi Arabian coastal waters near the desalination plants in AI-Jubail. Materials were collected from six different sites covering the intake and discharge zones during cruises carried out in 1997-1998. Analyses of chlorophyll pigments were made using the spectrophotometric method. Plankton samples were collected using a Nansen plankton net with a mesh size of 75 μ and analyzed following standard procedures. Chlorophyll a, b, c and phaeophytin are the most commonly occurring pigments in seawater. Their concentrations showed wide fluctuation. The phytoplankton community was composed of 35 genera representing the Diatoms, Dinoflagellates and blue- green algae. Zooplankton were composed ofProtozoa, Coelenterata, Ctenophora, Aschelminthes, Annelida, Mollusca, Arthropoda, Echinodermata and Chordata. Arthropoda, represented by Cladocera, Copepoda and Crustacean larvae, formed the largest group followed by Chordata. The distribution of phyto- and zooplankton was examined and discussed on a seasonal, annual and inter-annual basis. In terms of species, overall species composition was not affected by plant discharge. The study brings out a greater understanding of the changes experienced by biotic communities as a result of impingement, entrainment and entrapment consequent to water passage through the plant structures. The study reflects the ecological relationships that the phytoplankton and the zooplankton of the region possess with respect to intake and discharge. Further, the study has brought to light a very redeeming feature of the ecosystem to sustain its productivity and planktonic abundance. It was observed that seawater temperature, conductivity and total suspended solids did not act as limiting factors. Besides throwing much light on the little known biological aspects of desalination sites, the data provided constitute a significant addition to the knowledge base of marine living resources in an industrial zone of Gulf coastal waters. 相似文献
54.
The Knoop hardnesses of five glasses decreased with increasing load in accordance with the classic indentation size effect (ISE). At moderate loads, cracking dramatically altered the indentation sizes and the ISE trends in three of the five glasses. Cracked indentations were as much as 10 μm longer than uncracked indentations made under identical conditions. Diagonal length readings must be corrected for optical resolution limitations if low power lenses are used. 相似文献
55.
Optical microscopy is widely used in the characterization of coals and cokes. This Paper shows that the laser Raman microprobe (MOLE) which combines an optical microscope and a Raman spectrometer can provide useful additional information. Three main areas were investigated: identification of minerals in coal and coke; structural characterization of coals and cokes; and the interaction of inorganic additives and coal. Where possible, the results were compared with conventional optical microscopy measurements whereby it was shown that the optical texture and Raman spectra of cokes are not closely related. The Raman spectra of high temperature cokes were used to estimate the size of microcrystalline regions. 相似文献
56.
57.
John C. Lynch Jonathan S. Green Paul K. Hovsepian Kathleen L. Reilly Joseph A. Short 《Journal of Automated Methods and Management in Chemistry》1994,16(4):131-133
Laboratory robotics has been firmly established in many non-QC
laboratories as a valuable tool for automating pharmaceutical
dosage form analysis. Often a single project or product line is used
to justify an initial robot purchase thus introducing robotics to the
laboratory for the first time. However, to gain widespread acceptance
within the laboratory and to justify further investment in robotics,
existing robots must be used to develop analyses for existing manual
methods as well as new projects beyond the scope off the original
purchase justification. The Automation Development Group in
Analytical Research and Development is a team of analysts
primarily devoted to developing new methods and adapting existing
methods for the robot. This team approach developed the expertise
and synergy necessary to significantly expand the contribution of
robotics to automation in the authors'' laboratory. 相似文献
58.
The introduction of residual surface stresses into a material can change the strength distribution simply due to variability in the stress intensity factor of surface cracks. This variability arises from the distribution in surface (critical) crack lengths. A fracture mechanics approach was used to determine the influence of surface compression on the average strength and the standard deviation of the strength distribution. The strengths of the stress-free samples were assumed to fit a twoparameter Weibull distribution, and the increases in strength resulting from the surface compression were determined using fracture mechanics. It was determined from the analysis that the standard deviation/average strength ratio (coefficient of variation) initially increases, passes through a maximum, and ultimately reaches a plateau value below the initial value, as one increases the depth of surface compression. The maximum increase in the strength scatter occurs when the depth of the surface compression is approximately equal to the characteristic crack size. These changes were found to be dependent on the magnitude of the surface stress, as well as the characteristic strength, Weibull modulus, and fracture toughness of the stress-free material. 相似文献
59.
Flexible piezoresistive films, such as, carbon black/polydimethylsiloxane (C-PDMS) composites, are often used as skin analogs and integrated into complex array sensors for tactile sensing. The uniformity of the sensor characteristics heavily depends on the homogeneity of the composite. Therefore, the ability to locally characterize a film that will be integrated into a complex force sensor could be critical. Here, a method to characterize the local sensitivity of flexible piezoresistive films is presented. Using a conductive sphere, which was chosen over a flat probe to eliminate misalignment issues, the surface of a thin film composite is indented to characterize the change in resistivity in terms of average strain. Experiments were performed with 15 and 18 wt% carbon black C-PDMS films of varying thickness. The contact radius of the probe with the piezoresistive film was estimated using the Johnson-Roberts-Kendall contact theory. Theoretical contact area estimates were found to agree with contact radius measurements carried out using optically transparent PDMS films observed through an optical microscope. Results show that C-PDMS with 15 wt% carbon black exhibit a higher rate if change of resistivity and gauge factor than films of same thickness with 18 wt% carbon black. On the other hand, thicker films exhibit higher gauge factors for the two tested carbon black contents. Tests carried out at multiple locations yielded consistent sensitivity values, making these types of composites suitable for array type force sensors. 相似文献
60.
Robert E. Green Jr. Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1992,44(10):12-16
Although nondestructive techniques have been used almost exclusively to detect macroscopic defects in structures or devices, it has become increasingly evident that it is both practical and cost-effective to expand the role of nondestructive evaluation to include all aspects of materials production. In recent years, classical nondestructive testing techniques have been augmented by more sophisticated methods for characterizing the microstructure and the associated physical and chemical properties of materials. 相似文献