Pool boiling of saturated FC-72 on nano-porous surface

Pool boiling heat transfer from nano-porous surface immersed in a saturated FC-72 dielectric fluid has been experimentally studied at atmospheric pressure (101 kPa). The data obtained from nano-porous surface (Anodisc 25) of thickness about 70 μm made from aluminum oxide (Al₂O₃) obtained from Whatman, were compared to that of a plain surface (aluminum) of thickness about 105 μm. From the experimental data obtained it was evident that there is a reduction of about 30% in the incipient superheat for the applied power for nano-porous surface over plain surface. SEM photographs of the nano-porous coating were taken for determining the size of the pores.     

Delayed failure of ceramic matrix composites in tension at elevated temperatures

Ultimate tensile strength of five different continuous fiber-reinforced ceramic matrix composites (CMCs), including SiC_f/BSAS (two dimensional (2D), 2 types), SiC_f/MAS (2D), SiC_f/SiC (2D), and C_f/SiC (2D, 2 types), was determined as a function of test rate at 1100–1200 °C in air. All five CMCs exhibited a significant dependency of ultimate tensile strength on test rate such that the ultimate tensile strength decreased with decreasing test rate. The dependency of ultimate tensile strength on test rate, the applicability of preload technique, and the predictability of life from one loading configuration (constant stress-rate loading) to another (constant stress loading) all suggested that the overall, phenomenological delayed failure of the CMCs would be governed by a power-law type of slow crack growth.     

Failure loads for notched graphite/epoxy laminates with a softening strip

The strengths of two graphite/epoxy notched laminate systems with a softening strip were investigated. The softening strip was created by replacing the 0°-graphite/epoxy plies by a glass/epoxy composite. Experimental results indicated that the use of softening strips could significantly increase the laminate strength. Analysis was performed with finite elements developed using the classical laminated plate theory and was shown to be adequate. A simple point-stress failure criterion was used to predict the strength of notched laminates with softening strips and the result was found to be satisfactory.     

On the J-integral in periodically layered composites

When a heterogeneous elastic material is represented by an effective homogeneous elastic solid, average stress and strain fields are used. The meaning of the J-integral in the effective homogeneous solid is investigated. A periodically layered medium is considered. The relation between the J-integrals in the original layered medium and the effective medium is derived.     

Characterization of the evaluation of the solid solubility of Si in sintered Fe–Si alloys using DSC technique

Differential scanning calorimeter (DSC) is used to quantify the solid solubility of Si in sintered Fe–Si alloys. The calorimetry tests are run on Fe–Si alloys by arc melting and sintering. The relationship between the Curie temperature and the solid solubility of Si in Fe–Si alloys was determined using DSC. The solid solubility of Si in sintered Fe–Si alloys evaluated according to the relationship between magnetic transition and compositions can be compared with the results from a related quantitative electron probe microanalysis (EPMA).     

Grid implementation of the Apriori algorithm

The paper presents the implementation of an association rules discovery data mining task using Grid technologies. For the mining task we are using the Apriori algorithm on top of the Globus toolkit. The case study presents the design and integration of the data mining algorithm with the Globus services. The paper compares the Grid version with related work in the field and we outline the conclusions and future work.     

Al–Si cast alloys under isothermal and thermomechanical fatigue conditions

This work presents a survey of the isothermal and anisothermal fatigue behavior of aluminum casting alloys obtained from different processes. Experimental results have shown that porosity, especially large and irregular pores, provides the main factor in decreasing fatigue properties of the tested alloys. In materials with similar porosity levels, other microstructural factors became relevant such as, matrix morphology and the amount of alloying elements. Fractographic analyses showed that fatigue cracks preferentially start to propagate in microcracks or interdendritic shrinkage usually located next to the surface. In most cases, propagation takes place in the eutectic phase, although in the thixoformed material, a transition from transgranular to intergranular mode was observed in the crack propagation mode.     

A bibliometric study of China’s semiconductor literature compared with other major asian countries

In this paper we compare the scientific research in the semiconductor-related field in China with some other major nations in Asia. It is based on the bibliometric information from SCI-Expanded database during the time period of 1995–2004. We show that China has been developing fast in semiconductor research, and become the second productive country in Asia as reflected by the publication profile. The evidences indicate a significant increasing trend in the research efforts and readership among Asian countries. Similar to the scientists in Japan and South Korea, Chinese scientists were more inclined to work in larger groups, typically 4 or more authors. The assessment of research quality is further conducted based on citation-based measures. As benchmarks, two western countries, namely USA and Germany, have been compared in the citation analysis. It is revealed that the impacts of research outputs in the Asian countries, except for Japan, have been badly incommensurate with their devoted research efforts compared with USA and Germany. Like most of other Asian countries the research results of Chinese scientists in semiconductor have a low international visibility despite their strong research efforts and increasingly large domestic readership. The application of Leimkuhler curve illustrates vividly the inequality of citation times among the compared countries. Furthermore, the Gini Indices of each country and each pair of countries are calculated which illustrates again the inequality of informetric productivities.     

Thermoelastic composites with columnar microstructure and cylindrically anisotropic phases. Part I: Exact results

A wide class of composite materials, which are in this paper referred to as having columnar microstructure, posses the microgeometrical characteristic that the constituent phases are homogeneous along one and only one direction. This class includes as an important subclass all the composites consisting of a homogeneous matrix reinforced by aligned parallel continuous homogeneous fibers. In the present work, considering a transversely isotropic composite with columnar microstructure and with cylindrically anisotropic phases, a number of exact results are established for effective thermoelastic moduli by modelling the composite as a nested composite cylinder assemblage. The results obtained in this work extend those of Hashin and Rosen [Z. Hashin, B.W. Rosen, The elastic moduli of fiber-reinforced materials, ASME J. Appl. Mech. 31 (1964) 223–232] and Hashin [Z. Hashin, Thermoelastic properties and conductivity of carbon/carbon fiber composites, Mech. Mater. 8 (1990) 293–308].     

Microscopic examination of the microstructure and deformation of conventional and auxetic foams

Auxetic materials have a negative Poisson’s ratio, that is, they expand laterally when stretched longitudinally. One way of obtaining a negative Poisson’s ratio is by using a re-entrant cell structure. Auxetic foam was fabricated from a conventional polymeric foam. Assuming similar mechanical properties for the solid material comprising the foams, the principle variable affecting the properties of the foam is the geometry of the cells. This means that the unusual mechanical properties of auxetic foams are attributed to the deformation characteristics of re-entrant microstructures. In this paper, the results of optical- and scanning electron-microscopic studies of the geometrical parameters for the different foams examined are presented. Examples of the microstructural deformation mechanisms observed are also presented. Comparison between the conventional foams and their auxetic conversions are also made. This revised version was published online in November 2006 with corrections to the Cover Date.