Rate capability of graphite materials as negative electrodes in lithium-ion capacitors

The lithium-ion exchange rate capability of various commercial graphite materials are evaluated using galvanostatic charge/discharge cycling in a half-cell configuration over a wide range of C-rates (0.1 similar to 60C). The results confirm that graphite is capable of de-intercalating stored charge at high rates, but has a poor intercalating rate capability. Decreasing the graphite coating thickness leads to a limited rate performance improvement of the electrode. Reducing the graphite particle size shows enhanced C-rate capability but with increased irreversible capacity loss (ICL). It is demonstrated that the rate of intercalation of lithium-ions into the graphite is significantly limited compared with the corresponding rate of de-intercalation at high C-rates. For the successful utilisation of commercially available conventional graphite as a negative electrode in a lithium-ion capacitor (LIC), its intercalation rate capability needs to be improved or oversized to accommodate high charge rates.

Experimental and numerical investigation of strain-rate-dependent behavior of kangaroo shoulder cartilage

This thesis introduces a new animal model, kangaroo, to biomechanical investigations of shoulder cartilage research. It examines the effect of cartilage structure and constituents on tissue behavior and its adaptation to mechanical loading. In doing so, the study explains the relationship of tissue's functional behaviors to its structure and constituents which has important implications for tissue engineering strategies catering joint specific cartilage tissue generation.

Carbon dioxide emissions in the short run: The rate and sources of economic growth matter

This paper investigates the short-run effects of economic growth on carbon dioxide emissions from the combustion of fossil fuels and the manufacture of cement for 189 countries over the period 1961-2010. Contrary to what has previously been reported, we conclude that there is no strong evidence that the emissions-income elasticity is larger during individual years of economic expansion as compared to recession. Significant evidence of asymmetry emerges when effects over longer periods are considered. We find that economic growth tends to increase emissions not only in the same year, but also in subsequent years. Delayed effects - especially noticeable in the road transport sector - mean that emissions tend to grow more quickly after booms and more slowly after recessions. Emissions are more sensitive to fluctuations in industrial value added than agricultural value added, with services being an intermediate case. On the expenditure side, growth in consumption and growth in investment have similar implications for national emissions. External shocks have a relatively large emissions impact, and the short-run emissions-income elasticity does not appear to decline as incomes increase. Economic growth and emissions have been more tightly linked in fossil-fuel rich countries.

A curve shortening flow rule for closed embedded plane curves with a prescribed rate of change in enclosed area

Motivated by a problem from fluid mechanics, we consider a generalization of the standard curve shortening flow problem for a closed embedded plane curve such that the area enclosed by the curve is forced to decrease at a prescribed rate. Using formal asymptotic and numerical techniques, we derive possible extinction shapes as the curve contracts to a point, dependent on the rate of decreasing area; we find there is a wider class of extinction shapes than for standard curve shortening, for which initially simple closed curves are always asymptotically circular. We also provide numerical evidence that self-intersection is possible for non-convex initial conditions, distinguishing between pinch-off and coalescence of the curve interior.

Kinetics and mechanism of hot corrosion of γ-Y 2Si 2O 7 in thin-film Na 2SO 4 molten salt

γ-Y 2Si 2O 7 is a promising candidate material both for hightemperature structural applications and as an environmental/thermal barrier coating material due to its unique properties such as high melting point, machinability, thermal stability, low linear thermal expansion coefficient (3.9×10 -6/K, 200°-1300°C), and low thermal conductivity (<3.0 W/ṁK above 300°C). The hot corrosion behavior of γ-Y 2Si 2O 7 in thin-film molten Na 2SO 4 at 850°-1000°C for 20 h in flowing air was investigated using a thermogravimetric analyzer (TGA) and a mass spectrometer (MS). γ-Y 2Si 2O 7 exhibited good resistance against Na 2SO 4 molten salt. The kinetic curves were well fitted by a paralinear equation: the linear part was caused by the evaporation of Na2SO4 and the parabolic part came from gas products evolved from the hotcorrosion reaction. A thin silica film formed under the corrosion scale was the key factor for retarding the hot corrosion. The apparent activation energy for the corrosion of γ-Y 2Si 2O 7 in Na 2SO 4 molten salt with flowing air was evaluated to be 255 kJ/mol.

Hot corrosion of γ-Y2Si2O7 in strongly basic Na2CO3 molten salt environment

γ-Y2Si2O7 is a promising candidate both for high temperature structural applications and as thermal barrier coatings due to its unique combination of properties, such as high melting point, good machinability, high thermal stability, low linear thermal expansion coefficient (3.9 × 10-6 K-1, 25-1400 °C) and low thermal conductivity (<3 W/m K above 300 °C). In this work, the hot corrosion behavior of γ-Y2Si2O7 in strongly basic Na2CO3 molten salt at 850-1000 °C for 20 h in flowing air was investigated. In the employed conditions, multi-layer corrosion scales with total thickness less than 90 μm were formed. At 850-900 °C, the outmost layer of the scale was composed of the reprecipitation of Y2O3, the bottom of a Si-rich Na2O·xSiO2 (x > 3.65) melt layer, and the middle of a NaYSiO4 layer. At 1000 °C, the corrosion products turned out to be a mixture of NaY9Si6O26 and Si-rich Na2O·xSiO2 (x > 3.65). In all cases, a thin layer of protective SiO2 formed under the Na2O·xSiO2 melt and protected the bulk material from further corrosion.

When and why threats go undetected: Impacts of event rate and shift length on threat detection accuracy during airport baggage screening

Objective: We aimed to assess the impact of task demands and individual characteristics on threat detection in baggage screeners. Background: Airport security staff work under time constraints to ensure optimal threat detection. Understanding the impact of individual characteristics and task demands on performance is vital to ensure accurate threat detection. Method: We examined threat detection in baggage screeners as a function of event rate (i.e., number of bags per minute) and time on task across 4 months. We measured performance in terms of the accuracy of detection of Fictitious Threat Items (FTIs) randomly superimposed on X-ray images of real passenger bags. Results: Analyses of the percentage of correct FTI identifications (hits) show that longer shifts with high baggage throughput result in worse threat detection. Importantly, these significant performance decrements emerge within the first 10 min of these busy screening shifts only. Conclusion: Longer shift lengths, especially when combined with high baggage throughput, increase the likelihood that threats go undetected. Application: Shorter shift rotations, although perhaps difficult to implement during busy screening periods, would ensure more consistently high vigilance in baggage screeners and, therefore, optimal threat detection and passenger safety.

The Pandolf load carriage equation is a poor predictor of metabolic rate while wearing explosive ordnance disposal protective clothing

This investigation aimed to quantify metabolic rate when wearing an explosive ordnance disposal (EOD) ensemble (~33kg) during standing and locomotion; and determine whether the Pandolf load carriage equation accurately predicts metabolic rate when wearing an EOD ensemble during standing and locomotion. Ten males completed 8 trials with metabolic rate measured through indirect calorimetry. Walking in EOD at 2.5, 4.0 and 5.5km·h−1 was significantly (p < 0.05) greater than matched trials without the EOD ensemble by 49% (127W), 65% (213W) and 78% (345W), respectively. Mean bias (95% limits of agreement) between predicted and measured metabolism during standing, 2.5, 4 and 5.5km·h−1 were 47W (19 to 75W); −111W (−172 to −49W); −122W (−189 to −54W) and −158W (−245 to −72W), respectively. The Pandolf equation significantly underestimated measured metabolic rate during locomotion. These findings have practical implications for EOD technicians during training and operation and should be considered when developing maximum workload duration models and work-rest schedules.