• 7. Clean energy close

Optoelectronic measurements of carbon nanotube transistors have shown a wide variety of sensitivites to the incident light. Direct photocurrent processes compete with a number of extrinsic mechanisms. Here we show that visible light absorption in the silicon substrate generates a photovoltage that can electrically gate the nanotube device. The photocurrent induced by the changing gate voltage can be significantly larger than that due to direct electron-hole pair generation in the nanotube. The dominance of photogating in these devices is confirmed by the power and position dependence of the resulting photocurrent. The power dependence is strongly non-linear and photocurrents are measured through the device even when the laser illuminates up to 1~mm from the nanotube. Comment: 18 pages, 7 figures

We have derived values of the Ultraviolet Index (UVI) at solar noon using the Tropospheric Ultraviolet Model (TUV) driven by ozone, temperature and aerosol fields from climate simulations of the first phase of the Chemistry-Climate Model Initiative (CCMI-1). Since clouds remain one of the largest uncertainties in climate projections, we simulated only the clear-sky UVI. We compared the modelled UVI climatologies against present-day climatological values of UVI derived from both satellite data (the OMI-Aura OMUVBd product) and ground-based measurements (from the NDACC network). Depending on the region, relative differences between the UVI obtained from CCMI/TUV calculations and the ground-based measurements ranged between −5.9% and 10.6%. We then calculated the UVI evolution throughout the 21st century for the four Representative Concentration Pathways (RCPs 2.6, 4.5, 6.0 and 8.5). Compared to 1960s values, we found an average increase in the UVI in 2100 (of 2–4%) in the tropical belt (30°N-30°S). For the mid-latitudes, we observed a 1.8 to 3.4 % increase in the Southern Hemisphere for RCP 2.6, 4.5 and 6.0, and found a 2.3% decrease in RCP 8.5. Higher increases in UVI are projected in the Northern Hemisphere except for RCP 8.5. At high latitudes, ozone recovery is well identified and induces a complete return of mean UVI levels to 1960 values for RCP 8.5 in the Southern Hemisphere. In the Northern Hemisphere, UVI levels in 2100 are higher by 0.5 to 5.5% for RCP 2.6, 4.5 and 6.0 and they are lower by 7.9% for RCP 8.5. We analysed the impacts of greenhouse gases (GHGs) and ozone-depleting substances (ODSs) on UVI from 1960 by comparing CCMI sensitivity simulations (1960–2100) with fixed GHGs or ODSs at their respective 1960 levels. As expected with ODS fixed at their 1960 levels, there is no large decrease in ozone levels and consequently no sudden increase in UVI levels. With fixed GHG, we observed a delayed return of ozone to 1960 values, with a corresponding pattern of change observed on UVI, and looking at the UVI difference between 2090s values and 1960s values, we found an 8 % increase in the tropical belt during the summer of each hemisphere. Finally we show that, while in the Southern Hemisphere the UVI is mainly driven by total ozone column, in the Northern Hemisphere both total ozone column and aerosol optical depth drive UVI levels, with aerosol optical depth having twice as much influence on the UVI as total ozone column does.

Climate models are extensively used to assess mitigation and adaptation strategies for climate change, as shown by the Intergovernmental Panel on Climate Change Assessment Reports. The international climate modelling community supports these assessments through internationally coordinated experiments, the latest one in support to the 6th Assessment Report (to come out August 2021) being the 6th phase of the Coupled modeling intercomparison project, CMIP6. These experiments provide climate projections for future climate scenarios but also enhance the scientific basis for model evaluation and for understanding of climate processes. They represent an important investment in both computing and data shared openly through the Earth System Grid Federation, supported by the European Network for Earth System modelling (ENES) infrastructure project, IS-ENES. The future of climate modeling highly depends on available computing power: ensemble of prediction experiments to better estimate uncertainties, increase of resolution to better represent small scale processes, enhanced complexity of the Earth’s climate system to include biogeochemical cycles, capacity to run long experiments to investigate climate stability. Preparing for next generation climate models, enabling efficient high-resolution simulations, is addressed by the European Center of Excellence in HPC, ESiWACE. It gathers the climate and weather modelling communities with the object to enhance synergies between the two communities to address the new computing architectures, a challenge for these communities relying on legacy codes. Presented at the eScience 2021 Conference on September 21st, 2021.

The Cherenkov Telescope Array (CTA) \cite{CTA:2010} will be the successor to current Imaging Atmospheric Cherenkov Telescopes (IACT) like H.E.S.S., MAGIC and VERITAS. CTA will improve in sensitivity by about an order of magnitude compared to the current generation of IACTs. The energy range will extend from well below 100 GeV to above 100 TeV. To accomplish these goals, CTA will consist of two arrays, one in each hemisphere, consisting of 50-80 telescopes and composed of three different telescope types with different mirror sizes. It will be the first open observatory for very high energy $\gamma$-ray astronomy. The Array Control working group of CTA is currently evaluating existing technologies which are best suited for a project like CTA. The considered solutions comprise the ALMA Common Software (ACS), the OPC Unified Architecture (OPC UA) and the Data Distribution Service (DDS) for bulk data transfer. The first applications, like an automatic observation scheduler and the control software for some prototype instrumentation have been developed. Comment: In Proceedings of the 2012 Heidelberg Symposium on High Energy Gamma-Ray Astronomy. All CTA contributions at arXiv:1211.1840

Lithium-ion (Li-ion) batteries are an important component of energy storage systems used in various applications such as electric vehicles and portable electronics. There are many chemistries of Li-ion battery, but LFP, NMC, LMO, and NCA are four commonly used types. In order for the battery applications to operate safely and effectively, battery modeling is very important. The equivalent circuit model (ECM) is a battery model often used in the battery management system (BMS) to monitor and control Li-ion batteries. In this study, experiments were performed to investigate the performance of three different ECMs (1RC, 2RC, and 1RC with hysteresis) on four Li-ion battery chemistries (LFP, NMC, LMO, and NCA). The results indicated that all three models are usable for the four types of Li-ion chemistries, with low errors. It was also found that the ECMs tend to perform better in dynamic current profiles compared to non-dynamic ones. Overall, the best-performed model for LFP and NCA was the 1RC with hysteresis ECM, while the most suited model for NMC and LMO was the 1RC ECM. The results from this study showed that different ECMs would be suited for different Li-ion battery chemistries, which should be an important factor to be considered in real-world battery and BMS applications.

A direct search has been made for magnetic monopoles produced in e + p collisions at a centre of mass energy of 300 GeV at HERA. The beam pipe surrounding the interaction region in 1995-1997 was investigated using a SQUID magnetometer to look for stopped magnetic monopoles. During this time an integrated luminosity of 62 pb-1 was delivered. No magnetic monopoles were observed and charge and mass dependent upper limits on the e + p production cross section are set. The European Physical Journal C, 41 (2) ISSN:1434-6052 ISSN:1434-6044

AbstractAn interesting example of device combining amorphous material and nano‐ or microstructure is the wire solar cell. Solar cells based on silicon nano‐ or microwires have attracted much attention as a promising path for low cost photovoltaic technology. The key point of this structure is the decoupling of the light absorption from the carriers collection. In this work, we use numerical modeling to study two types of radial junction structures: (i) a p–n heterojunction for which p‐or n‐type crystalline silicon (c‐Si) wires are covered by a conformal n‐ or p‐ doped amorphous silicon (a‐Si:H) thin layer and (ii) thin film a‐Si:H p–i–n radial structures realized by conformal covering on thinner c‐Si wires. In the first structure, the a‐Si:H layer is only intended to form the heterojunction and light absorption takes place in the c‐Si wires, whereas in the second one, the absorber material is the a‐Si:H i‐layer and its thickness can be optimized to facilitate the carrier separation and collection. The potential of those both types of Si wires based solar cells will be compared according to the structure design and material properties. Furthermore, the sensitivity of the a‐Si:H p–i–n radial cells to the light‐soaking effect, i.e., the increase of deep defect density resulting from the breaking of weak silicon bonds, will be studied and compared to what is commonly observed on classical a‐Si:H planar p–i–n cells.