Superconducting weak links coupled by charge imbalance waves

1983 ◽  
Vol 50 (5-6) ◽  
pp. 475-487 ◽  
Author(s):  
James A. Blackburn
Keyword(s):  
Author(s):  
R. Sharma ◽  
B.L. Ramakrishna ◽  
N.N. Thadhani ◽  
D. Hianes ◽  
Z. Iqbal

After materials with superconducting temperatures higher than liquid nitrogen have been prepared, more emphasis has been on increasing the current densities (Jc) of high Tc superconductors than finding new materials with higher transition temperatures. Different processing techniques i.e thin films, shock wave processing, neutron radiation etc. have been applied in order to increase Jc. Microstructural studies of compounds thus prepared have shown either a decrease in gram boundaries that act as weak-links or increase in defect structure that act as flux-pinning centers. We have studied shock wave synthesized Tl-Ba-Cu-O and shock wave processed Y-123 superconductors with somewhat different properties compared to those prepared by solid-state reaction. Here we report the defect structures observed in the shock-processed Y-124 superconductors.


2021 ◽  
pp. 118223
Author(s):  
M. Autzen ◽  
A.S. Murray ◽  
M. Jain ◽  
J.-P. Buylaert
Keyword(s):  

Logistics ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 12
Author(s):  
Lakshmy Subramanian

Health supply chains aim to improve access to healthcare, and this can be attained only when health commodities appropriate to the health needs of the global population are developed, manufactured, and made available when and where needed. The weak links in the health supply chains are hindering the access of essential healthcare resulting in inefficient use of scarce resources and loss of lives. A chain is only as strong as its weakest link, and demand forecasting is one of the weakest links of health supply chains. Also, many of the existing bottlenecks in supply chains and health systems impede the accurate forecasting of demand, and without the ability to forecast demand with certainty, the stakeholders cannot plan and make commitments for the future. Forecasts are an important feeder for budgeting and logistics planning. Under this backdrop, the study examines how improved forecasting can lead to better short-term and long-term access to health commodities and outlines market-related risks. It explores further how incentives are misaligned creating an uneven distribution of risks, leading to the inability to match demand and supply. For this purpose, a systematic literature review was performed, analyzing 71 articles from a descriptive and content approach. Findings indicate the emerging trends in global health and the consequences of inaccurate demand forecasting for health supply chains. The content analysis identifies key factors that can pose a varying degree of risks for the health supply chain stakeholders. The study highlights how the key factors emerge as enablers and blockers, depending on the impact on the overall health supply chains. The study also provides recommendations for actions for reducing these risks. Consequently, limitations of this work are presented, and opportunities are identified for future lines of research. Finally, the conclusion confirms that by adopting a combination of approaches, stakeholders can ensure better information sharing, identify avenues of diversifying risks, and understand the implications.


Author(s):  
A. Brown ◽  
K. Krishnan ◽  
L. Wayne ◽  
P. Peralta ◽  
S. N. Luo ◽  
...  

Global and local microstructural weak links for spall damage were investigated using 3-D characterization in polycrystalline (PC) and multicrystalline (MC) copper samples, respectively. All samples were shocked via flyer-target plate experiments using a laser drive at low pressures (2–6 GPa). The flyer plates measured approximately 500 μm thick and 8 mm in diameter and the target plates measured approximately 1000 μm thick and 10 mm in diameter. Electron Backscattering Diffraction (EBSD) and optical microscopy were used to determine to presence of voids and relate them to the surrounding microstructure. Statistics on the strength of grain boundaries (GBs) was conducted by analyzing PC samples and collecting the misorientation across GBs with damage present, and it was found that a misorientation range of 25–50° is favorable for damage. Statistics were also taken of copper PC samples that had undergone different heat treatments and it was found that although the 25–50° range is less dominant, it is still favorable for damage nucleation. Removal of initial plastic strain via heat treatments and an increase in Σ3 CSL boundaries, indicative of strong annealing twins, also led to an increased amount of transgranular damage. 3-D X-ray tomography data were used to investigate the shape of the voids present in untreated, as received and heat treated samples. It was found that the as received sample contained a higher amount of “disk”, or, “sheet-like” voids indicative of intergranular damage, whereas the heat treated samples had a higher fraction of spherical shaped voids, indicative of transgranular damage. MC samples were used to study microstructural weak links for spall damage because the overall grain size is much larger than the average void size, making it possible to determine which GBs nucleated damage. Simulations and experimental analysis of damage sites with large volumes indicate that high Taylor factor mismatches with respect to the crystallographic grain GB normal is the primary cause for the nucleation of damage at a GB interface and a low Taylor factor along the shock direction in either grain drives void growth perpendicular to the GB. Cases where experimental results show damage and simulation results show no damage are attributed to the presence of an intrinsic microstructural weak link, such as an incoherent twin boundary.


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