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101.
Heather F. Jackson Daniel D. Jayaseelan William E. Lee Michael J. Reece Fawad Inam Dario Manara Carlo Perinetti Casoni Franck De Bruycker Konstantinos Boboridis 《International Journal of Applied Ceramic Technology》2010,7(3):316-326
Melting temperatures of zirconium carbide were investigated in validating a novel thermal analysis technique for refractory materials. Commercial ZrC0.96 powder was densified by spark plasma sintering to >96% relative density after 6–30 min at 2173–2453 K under 40–100 MPa. Sintered ceramics were heated to >4000 K via pulsed laser heating. Mean values for solidus and liquidus transitions were 3451 and 3608 K, respectively, in fair agreement with the present phase diagram. Postmelting analysis revealed dendritic microstructure and composition consistent with single-phase ZrC. Subsurface gas porosity and ZrC–C eutectic indicate complex processes occurring during melting and freezing. 相似文献
102.
In this paper we explore algorithms and architectures for the implementation of a MIMO OFDM Equalizer for high speed wireless
communications. The algorithmic exploration is based on matrix computations and factorizations. A scalable computational methodology
and architecture is proposed for the implementation of a 4×4 MIMO OFDM. A 2×3 Equalizer supporting Maximum Ratio Combining
and Zero Forcing equalization for 20/40 MHz 64-QAM OFDM modulation has been implemented in 150 nm technology. The Equalizer
area is 133k gates and the maximum throughput achieved is 480Mbits/s. The system described in this paper is compliant with
the latest IEEE standard for MIMO wireless communications (802.11n) 相似文献
103.
Pain DJ Carter I Sainsbury AW Shore RF Eden P Taggart MA Konstantinos S Walker LA Meharg AA Raab A 《The Science of the total environment》2007,376(1-3):116-127
Since 1989, a red kite Milvus milvus reintroduction programme has been underway in the United Kingdom, with 4-6 week old nestlings brought into captivity and held for 6-8 weeks before reintroduction. As scavengers, red kites may consume unretrieved game, and ingest shot or lead (Pb) fragments in their prey's flesh. We evaluated exposure to Pb in captive and wild red kites by taking blood samples from 125 captive young red kites prior to release, through analysing 264 pellets (regurgitated by wild birds) collected from under a roost site, and analysing Pb concentrations in livers and/or bones of 87 red kites found dead between 1995 and 2003. Lead isotope analyses of livers were also conducted in an effort to identify Pb exposure routes. Forty-six (36.8%) kites sampled prior to release had elevated blood Pb concentrations (201-3340 microg l(-1)). The source of this Pb was probably small fragments of lead ammunition in the carcasses of birds or mammals either fed to the nestlings by their parents or, more likely, subsequently whilst in captivity. Once released, kites were also exposed to lead shot in their food, and a minimum of 1.5-2.3% of regurgitated pellets contained Pb gunshot. Seven of 44 red kites found dead or that were captured sick and died within a few days had elevated (>6 mg kg(-1) dry weight [d.w.]) liver Pb concentrations, and six of these (14%) had concentrations of >15 mg kg(-1) d.w., compatible with fatal Pb poisoning. Post-mortem analyses indicated that two of these birds had died of other causes (poisoning by rodenticide and a banned agricultural pesticide); the remaining four (9%) probably died of Pb poisoning. Bone samples from 86 red kites showed a skewed distribution of Pb concentration, and 18 samples (21%) had Pb concentrations >20 mg kg(-1) d.w., indicating elevated exposure to Pb at some stage in the birds' life. Lead isotopic signatures (Pb (208/206); Pb (206/207)) in liver samples of the majority of kites were compatible with those found in lead shot extracted from regurgitated pellets. Lead isotope ratios found in the livers of kites with very low Pb concentrations were distinct from UK petrol Pb isotopic signatures, indicating that birds were exposed to little residual petrol Pb. We conclude that the primary source of Pb to which red kites are exposed is lead ammunition (shotgun pellets or rifle bullets), or fragments thereof, in their food sources; in some cases exposure appears sufficient to be fatal. We make recommendations to reduce Pb poisoning in both captive and wild red kites and other scavenging species. 相似文献
104.
Reliability assessment of cutting tool life based on surrogate approximation methods 总被引:2,自引:0,他引:2
Konstantinos Salonitis Athanasios Kolios 《The International Journal of Advanced Manufacturing Technology》2014,71(5-8):1197-1208
A novel reliability estimation approach to the cutting tools based on advanced approximation methods is proposed. Methods such as the stochastic response surface and surrogate modeling are tested, starting from a few sample points obtained through fundamental experiments and extending them to models able to estimate the tool wear as a function of the key process parameters. Subsequently, different reliability analysis methods are employed such as Monte Carlo simulations and first- and second-order reliability methods. In the present study, these reliability analysis methods are assessed for estimating the reliability of cutting tools. The results show that the proposed method is an efficient method for assessing the reliability of the cutting tool based on the minimum number of experimental results. Experimental verification for the case of high-speed turning confirms the findings of the present study for cutting tools under flank wear. 相似文献
105.
Andrea Brambilla Christos E. Frouzakis John Mantzaras Ananias Tomboulides Stefan Kerkemeier Konstantinos Boulouchos 《Combustion and Flame》2014
Transient two-dimensional simulations of fuel-lean H2/air combustion were performed in a 2-mm-height planar channel coated with platinum, using detailed hetero-/homogeneous chemistry and transport as well as heat conduction in the solid wall. The developed model resolved, for the first time, all relevant spatiotemporal scales in a practical channel-flow reactor configuration. A parametric study was carried out to investigate the effects of wall material, inlet velocity, and inlet temperature on the fundamental catalytic and gas-phase combustion processes. Computational singular perturbation (CSP) analysis identified the key catalytic reactions affecting light-off and homogeneous ignition. Homogeneous ignition crucially depended on the OH desorbing fluxes from the catalyst, while flame propagation and stabilization involved time scales of a few milliseconds. During the short duration of the light-off event, the ensuing Stefan velocity appreciably altered the flow field. Predictions of time accurate numerical simulations were further compared against those of a code relying on the quasisteady state assumption, and the specific conditions under which the latter was invalidated were identified. Finally, CSP analysis unraveled the reasons for the high computational cost of the fully transient 2-D simulations. The surface reaction mechanism exhibited a high stiffness with fastest time scales of the order of 10-12 s, pertaining to the hydrogen adsorption and to the H(s) + O(s) = OH(s) + Pt(s) reactions. These time scales were in turn six orders of magnitude shorter than the ones associated with gas-phase chemistry or with a simplified single-step catalytic reaction. 相似文献
106.
Differences in phenotypic responses among strains of the same microbial species constitute an important source of variability in microbiological studies, and as such they need to be assessed, characterized and taken into account. This review provides a compilation of available research data on the strain variability of four basic behavioral aspects of foodborne bacterial pathogens including: (i) virulence; (ii) growth; (iii) inactivation; and (iv) biofilm formation. A particular emphasis is placed on the foodborne pathogens Listeria monocytogenes and Salmonella enterica. The implications of strain variability for food safety challenge studies and microbial risk assessment are discussed also. The information provided indicates that the variability among strains of foodborne bacterial pathogens with respect to their behavior can be significant and should not be overlooked. However, in order for the mechanisms underlying the observed strain variability to be elucidated and understood, phenotypic variability data, such as those reviewed here, should be evaluated in conjunction with corresponding findings of studies assessing the molecular/physiological basis of this variability. 相似文献
107.
Konstantinos Salonitis John Pandremenos John Paralikas George Chryssolouris 《The International Journal of Advanced Manufacturing Technology》2010,49(5-8):803-826
Multifunctional materials are designed so as to meet specific requirements through tailored properties. Smart materials can be considered as multifunctional ones that have the ability to react upon an external stimulus, simulating, in this way, the behavior of nature’s materials. Furthermore, the introduction of biomemetics in the material science, allows the designing of materials with similar processes as nature does: building from molecules to complete structures. This paper focuses on the presentation of the various multifunctional materials reported in the literature and the processing means developed. 相似文献
108.
Built-up columns are often used in steel buildings and bridges providing economical solutions in cases of large spans and/or heavy loads. Two main effects should be taken into account in their design that differentiate them from other structural members. One is the significant influence of shear deformations due to their reduced shear rigidity. The second is the interaction between global and local buckling. These effects are addressed here from both a numerical and an analytical point of view for laced built-up columns. It is concluded that the largest loss of capacity occurs when the local and global Euler critical stresses and the yield stress all coincide. This reduction in capacity becomes more prominent in the presence of imperfections, reaching magnitudes in the order of 50%. Despite the detrimental effects of mode interaction many major design codes do not provide sufficient pertinent guidance. In order to address this issue, a simple analytical method is proposed for calculating the collapse load of laced built-up members taking into account the above effects as well as global imperfections, local out-of straightness and plasticity, which is then verified by means of nonlinear finite element analysis, using either beam or shell elements. The proposed method is found to provide improved accuracy in comparison to EC3 specifications in cases of global elastic failure. 相似文献
109.
110.
Konstantinos P. Demestichas Evgenia F. Adamopoulou John G. Markoulidakis Michael E. Theologou 《Journal of Network and Computer Applications》2009,32(1):116-134
In the current market conditions, network operators are in search of novel value-added services that will increase their revenue. This paper introduces the innovative concept of Anonymous Mobile Community (AMC) services and thoroughly defines and describes a robust platform targeted for their deployment. AMC services take advantage of the terminals’ capabilities to collect information and deliver it to the network. In this context, terminals are enabled to form communities that serve as sources of information. In these communities, the anonymity and privacy of the end-users are respected and guarded. Several examples of promising AMC services are presented and categorized. An indicative example application is the provision of real-time information regarding road-traffic conditions, based on the location and speed of mobile terminals. A system aiming at the provision of diverse AMC services is proposed, and its requirements, architecture and functionality are described in detail. The related scalability issues and business models are carefully outlined, and a use case scenario as well as trial results are presented. 相似文献