43 research outputs found
A new superconductor in lead cuprate (Pb0.5B0.5)Sr-2(Y0.5Ca0.5)Cu2Py
No full textA new lead cuprate superconductor, (Pb0.5Ba0.5)Sr-2(Y0.5Ca0.5)Cu2Oy, With T-c(onset)=62 K and T-c(zero)=31 K, has been prepared. Barium ions occupy the part sites of the lead in the unit cell. The crystal parameters of this superconductor are a=3.82 Angstrom, c=11.93 Angstrom. For one of the samples, an anomalous drop of resistance was observed around 230 K, but it disappeared after 4 thermocycles.Physics, AppliedSCI(E)EI
Cosmological parameter estimation using Very Small Array data out to ℓ= 1500
No full textWe estimate cosmological parameters using data obtained by the Very Small Array (VSA) in its extended configuration, in conjunction with a variety of other cosmic microwave background (CMB) data and external priors. Within the flat Λ cold dark matter (ΛCDM) model, we find that the inclusion of high-resolution data from the VSA modifies the limits on the cosmological parameters as compared to those suggested by the Wilkinson Microwave Anisotropy Probe (WMAP) alone, while still remaining compatible with their estimates. We find that Ωbh2= 0.0234+0.0012−0.0014, Ωdmh2= 0.111+0.014−0.016, h= 0.73+0.09−0.05, nS= 0.97+0.06−0.03, 1010AS= 23+7−3 and τ= 0.14+0.14−0.07 for WMAP and VSA when no external prior is included. On extending the model to include a running spectral index of density fluctuations, we find that the inclusion of VSA data leads to a negative running at a level of more than 95 per cent confidence ( nrun=−0.069 ± 0.032 ), something that is not significantly changed by the inclusion of a stringent prior on the Hubble constant. Inclusion of prior information from the 2dF galaxy redshift survey reduces the significance of the result by constraining the value of Ωm. We discuss the veracity of this result in the context of various systematic effects and also a broken spectral index model. We also constrain the fraction of neutrinos and find that fν < 0.087 at 95 per cent confidence, which corresponds to mν < 0.32 eV when all neutrino masses are equal. Finally, we consider the global best fit within a general cosmological model with 12 parameters and find consistency with other analyses available in the literature. The evidence for nrun < 0 is only marginal within this model
Implementation fidelity of circularity in publicly tendered civil engineering projects
No full textWith the current urgency to become more circular, procurement presents the primary method to deliver the circular policy ambition by purchasing circular products and stimulating circularity in the market. In the building and infrastructure sector, civil engineering projects offer unique opportunities for circularity. This research presents an assessment of the implementation fidelity of the circular ambition within the tendering process. It examines for each of the methods that define the tendering process, the tendered project, and the awarding framework whether the way circularity is being implemented delivers the ambition as expected.Along with the four research phases, the research devises and uses a framework to assess the fidelity of circularity implementation through the methods to include it in the tendering of civil engineering works. The implementation fidelity framework is used to; create a holistic analysis that captures the many facets impacting the tendering process; determine areas of issues and, consequently, room for improvements; and differentiate between the methods to include the circular ambition in the process. Through three study cases, the construct of the analysis managed to capture the data between quantitative and qualitative in a consistent and interpretable manner. It creates a consistent link between the fidelity dimensions, the corresponding issue areas, and the methods to include circularity in the tendering process. The room for improvement follows the three moderating dimensions, exposure, quality of delivery, and participation. The research links the issues impacting the fidelity of circular ambition implementation in three categories: structural issues, implementation traps, and policy-related, to the three moderating dimensions. The research acknowledges that policy-related issues impact at a sector level as issues inherent to the policy itself. Nonetheless, the research finds that, on an organizational level, removing structural issues and implementation traps raises overall fidelity and reduces the effect of policy-related issues. Increasing this fidelity reflects on the efficacy of the methods to include circularity in tendering, individually and as a group of instruments intended to complement each other. In conclusion, the research recommends practical use of the implementation fidelity framework, which would feed into the body of expertise within an organization to improve future tendering processes to include, enable, and produce more circular solutions with more efficacy in the use of the methods. It will also allow aligning perceptions of the contractors and the contracting authority on one hand and the policymakers and policy implementers on the other hand. For future research, examining all five implementation fidelity dimensions for the instruments and processes at the different levels throughout the procurement cycle is most compatible with the circular ambition in the building and infrastructure sector. This could be most beneficial to establish a more vital link between policymakers and policy implementers. Moreover, it would support future efforts to update the circular ambition goals and milestones by presenting a more encompassing image of the policy implementation fidelity in real-world settings.Civil Engineering | Construction Management and Engineerin
FRP Design using structural mechanics models
No full textThe application and expansion of FRP reinforced concrete has been hindered and obstructed through the misconception and misunderstanding that empirically derived rules developed for steel reinforced concrete in cracked regions can be used either directly or as a guidance for FRP reinforced concrete. This assumption is incorrect because the empirical rules developed for steel reinforced concrete in cracked regions, as with all empirical rules, should only be used within the bounds of the testing regimes from which they were developed, which for steel reinforced concrete is normal strength concrete with high ductile steel that has very good bond. As these bounds do not apply to FRP reinforced concrete, the steel RC empirical rules for cracked concrete are of little or no help for FRP RC. In fact, they are often misleading and as such prevent the widespread use of FRP reinforcement. It will be shown and illustrated in this presentation that generic mechanics based rules can be developed at all load conditions for RC beams that applies to both steel and FRP reinforcement. And, furthermore, that these generic mechanics based design rules allay many of the misconceptions inferred by the empirically based RC design rules such as that moment redistribution cannot occur with brittle FRP reinforced concrete which is simply not the case. © Tsinghua University Press, Beijing and Springer-Verlag Berlin Heidelberg 2011.http://books.google.com/books?id=0W8DTwEACAAJ&dq=9783642174865&num=4&client=internal-uds&cd=1&source=ud
Several Important Problems in YBaCuO and Its Doped Systems
No full textABSTRACTThe orthorhombic-tetragonal transition, relationship between oxygen content and TC, electronic state of Cu and TC, lattice energy and TC in YBCO and its doped systems (Cu doped by Sn, Al, Fe, Zn, Ni; Ba by Sr, Ca; Y by Pr,Gd,Dy, respectively.) have been studied systematically. The experiments show that the O-T transition may not be the predominant factor governing superconductivity; there is no regular relationship between superconductivity and the oxygen content. In order to fully understand superconductivity, other defects must be considered; the valence of Cu has a strong correlation with oxygen content, but has no direct relationship with the TC value. The correlation among the electronic states of Ba, Cu and O are discovered, which is helpful to know the electfonic behavior of this material. Finally, we show that the lattice energy has a close relationship with the magnitude of TC. As the lattice energy is decreased, the TC is always depressed without any exception. The authors suggest that the lattice energy may be a probable predominant factor to superconductivity.</jats:p
Dynamic study of oxygen in Cu-O plane in Bi-system superconductors
No full textSuperconducting transition temperature (T-c), hole concentration (n(c)), and crystal structure for Bi1.7Pb0.3Sr2Ca2Cu3Oy (2223) polycrystals and Bi2Sr2CaCu2Oy (2212) single crystals annealed in different atmospheres have been measured. It is found that the consequence of annealing in O-2 is mainly the modification of the oxygen in Cu-O planes, which is different from that in N-2 where the change is in the Bi-O planes. The result provides a good explanation for the complicated changes of the T-c with the annealing conditions.Physics, AppliedSCI(E)EI
An Opposite Behaviour of Semiconducting and Superconducting YBCO Single Crystal
No full textAn opposite thermal dynamic change in superconducting and semiconducting cuprates of YBa2Cu3O7−x(Y-123) is observed. At 450 °C the superconducting Y-123 single crystal shows an endothermal anomaly and a weight loss, while the semiconducting one shows an exothermal anomaly and weight gain. High temperature x-ray diffraction reveals that the lattice parameters of the Y-123 crystal jump significantly at this temperature. A computer simulation demonstrates that the change of the lattice parameters can be related with the change of the lattice energy
NbC-TiN co-precipitation behavior and mechanical properties of X90 pipeline steels by critical-temperature rolling process
No full textStudy of mismatch between two different blocks in Bi-system superconductors
No full textSamples of Bi1.7Pb0.3Sr2Ca2Cu3O10+y (2223) annealed in different atmospheres and having different value of T-c and oxygen contents were obtained and examined by a wide range of measurements as well as theoretical calculation. A roughly quantitative relationship among T-c, oxygen content, c direction thermal expansion coefficient, and mismatch factors are established. It is revealed that the mismatch is important for superconductivity.Physics, AppliedSCI(E)EI
Anomalous Behaviour of Bi-System Superconductors in the Normal State and their Correlation with Superconductivity
No full textOur experiments show that Bi-system samples exhibit two parameter anomalies and two heat and weight anomalies in normal state. For the samples of (Bi,Pb)2Sr2CaCu2Oy, as the superconducting volume is over 65%, two anomalies of heat and weight at about 400 °C and 750 °C, respectively, are significantly observed; as the superconducting volume of the samples is under 50%, or the samples are non-superconducting, the anomaly at about 400 °C is hardly observed. For the samples of (Bi,Pb)2Sr2Ca2Cu3Oy, as the superconducting volume is over 65%, they exhibit two anomalies at about 300 °C and 750 °C, respectively; as the superconducting volume is under 50%, the anomaly at about 300 °C disappears, and as the samples are non-superconducting, it shows a quite opposite behavior to the superconducting samples at about 300 °C. We develop a computer program based on calculation of lattice energy to simulate the experimental results, it is found that the change of the lattice energy can well explain the anomalous phenomena in the samples
