Response of real-time black carbon mass instruments to mini-CAST soot

Soot is a climate forcer and a dangerous air pollutant that has been increasingly regulated. In aviation, regulatory measurements of soot mass concentration in the exhaust of aircraft turbine engines are to be based on measurements of black carbon (BC) calibrated to elemental carbon (EC) content of diffusion flame soot. The calibration soot must currently meet only one criterion: minimum EC to total carbon (TC) ratio of 0.8. However, not including soot properties other than the EC/TC ratio may potentially lead to discrepancies between different BC measurements. We studied the response of two instruments, the AVL Micro-Soot Sensor (MSS) and the Artium Laser-Induced Incandescence 300 (LII), to soot from two miniature combustion aerosol standard (mini-CAST) burners. By changing the air-fuel ratio, premixing nitrogen into the fuel, and using a catalytic stripper to remove volatile compounds, we produced a wide range of particle morphologies and EC contents. As the EC content decreased, both the instruments underreported the EC mass, but the LII diverged more severely. Upon closer investigation of eight conditions with EC/TC > 0.8, the LII underreporting was found independent of primary particle size, but increased with decreasing geometric mean diameter of the soot agglomerates. As the geometric mean diameter decreased from 160 nm to 50 nm, the differences between the LII and MSS increased from 15% to 50%. The results suggest that in addition to EC content, calibration procedures for the regulatory BC measurements may need to take particle size distributions into account.

© 2016 American Association for Aerosol Research     

Fourier‐Transform Rheology of Unvulcanized,Carbon Black Filled Styrene Butadiene Rubber

Rubber materials filled with reinforcing fillers display nonlinear rheological behavior at small strain amplitudes below γ₀ < 0.1. Nevertheless, rheological data are analyzed mostly in terms of linear parameters, such as shear moduli (G′, G″), which loose their physical meaning in the nonlinear regime. In this work styrene butadiene rubber filled with carbon black (CB) under large amplitude oscillatory shear (LAOS) is analyzed in terms of the nonlinear parameter I_3/1. Three different CB grades are used and the filler load is varied between 0 and 70 phr. It is found that I_3/1(φ) is most sensitive to changes of the total accessible filler surface area at low strain amplitudes (γ₀ = 0.32). The addition of up to 70 phr CB leads to an increase of I_3/1(φ) by a factor of more than ten. The influence of the measurement temperature on I_3/1 is pronounced for CB levels above the percolation threshold.

     

A monolithically integrated high‐efficiency Cu(In,Ga)Se2 mini‐module structured solely by laser

Monolithically integrated Cu(In,Ga)Se₂ mini‐modules were fabricated in order to reduce the width of patterning related dead area. The Cu(In,Ga)Se₂ layers were prepared on soda‐lime glasses using the multistage process at low substrate temperature below 500 °C. A picosecond laser with a wavelength of 532 nm was used for all of the structuring processes (P1, P2, and P3) for the monolithic integration. A “lift‐off” type structuring was applied for P1 and P3, and an “ablation” type was for P2. The laser structuring was optimized to be minimizing the dead area width, and the width of about 70 µm was successfully achieved. A mini‐module, in which the optimized structuring processes were applied for the integration, demonstrated a certified efficiency of 16.6%. Copyright © 2015 John Wiley & Sons, Ltd.     

Assessing physical activity in the daily life of cystic fibrosis patients

Physical Activity (PA) plays an important role in the health and quality of life of cystic fibrosis (CF) patients, but little is known about their PA in daily living. With the use of accelerometers it is now possible to monitor activity profiles in detail. The goals of this study are to assess feasibility and acceptance of a longer-term use of accelerometers in daily living in CF patients, study the possibility of detecting changes in PA in relation to the patients’ clinical state and compare the findings between a CF and an age-matched healthy control group. We asked 15 CF patients to wear two accelerometers for 21 days and fill in a diary. Ten of them (age 21 to 40, mean 29.5 years) participated and delivered data that could be evaluated. We also recruited 10 age-matched control subjects. Data was processed for calculating usage time and features extracted to construct models of activity. The younger patients, particularly females, were concerned with fashion and style and considered wearing the sensors a challenge. Overall, the compliance of patients with CF seemed to be lower than reported for elder subjects in the literature. Time-series analysis of the data indicated characteristic patterns of PA over time, provided that data pre-processing and noise-filtering had been optimized. Further studies have to assess whether the continuous recording of PA yields additional clinical information in CF and in particular, whether it is possible to detect or even predict exacerbations in patients with CF or other diseases.     

On forecasting large and infrequent snow avalanches

Snow avalanches that threaten a highway or a residential area are often large avalanches that have a return period > 1 year. Danger assessment strongly relies on precipitation data since these avalanches are typically triggered by major snow storms. Given the extensive protection work that is in place in the European Alps, the avalanche control service (also called avalanche commission) responsible for danger assessment will usually monitor the avalanche situation throughout the winter, but only become active in case of a major snow fall. Related safety concepts describing the procedures and measures to be taken in a given danger situation are therefore often based on threshold values for new snow. By analysing the avalanche occurrence of a major avalanche path, we show that forecasting based on new snow amounts involves high uncertainty. Whereas the return period of an avalanche to, for example, the road was about 5 years, the return period for the corresponding new snow depth was substantially smaller, in our case slightly less than 2 years. Similar proportions were found for a number of other avalanche paths with different snow climate. The return period of the critical new snow depth was about 2–5 times smaller than the return period of the avalanche. This proportion is expected to increase with increasing return period. Hence, based on the return period of an avalanche path a first estimate for the critical new snow depth can be made. With a return period of the critical new snow depth of 1–2 years, avalanche prediction for individual avalanche path becomes very challenging since the false alarm ratio is expected to be high.     

Occupant related household energy consumption in Canada: Estimation using a bottom-up neural-network technique

A national model of residential energy consumption requires consideration of the following end-uses: space heating, space cooling, appliances and lighting (AL), and domestic hot water (DHW). The space heating and space cooling end-use energy consumption is strongly affected by the climatic conditions and the house thermal envelope. In contrast, both AL and DHW energy consumption are primarily a function of occupant behaviour, appliance ownership, demographic conditions, and occupancy rate. Because of these characteristics, a bottom-up statistical model is a candidate for estimating AL and DHW energy consumption. This article presents the detailed methodology and results of the application of a previously developed set of neural network models, as the statistical method of the Canadian Hybrid Residential End-Use Energy and Greenhouse Gas Emissions Model (CHREM). The CHREM estimates the national AL and DHW secondary energy consumption of Canadian single-detached and double/row houses to be 248 PJ and 201 PJ, respectively. The energy consumption values translate to per household values of 27.8 GJ and 22.5 GJ, and per capita values of 9.0 GJ and 7.3 GJ, respectively.     

Digital camera identification from sensor pattern noise

In this paper, we propose a new method for the problem of digital camera identification from its images based on the sensor's pattern noise. For each camera under investigation, we first determine its reference pattern noise, which serves as a unique identification fingerprint. This is achieved by averaging the noise obtained from multiple images using a denoising filter. To identify the camera from a given image, we consider the reference pattern noise as a spread-spectrum watermark, whose presence in the image is established by using a correlation detector. Experiments on approximately 320 images taken with nine consumer digital cameras are used to estimate false alarm rates and false rejection rates. Additionally, we study how the error rates change with common image processing, such as JPEG compression or gamma correction.     

Real-time, on-line characterization of diesel generator air toxic emissions by resonance-enhanced multiphoton ionization time-of-flight mass spectrometry

The laser-based resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS) technique has been applied to the exhaust gas stream of a diesel generator to measure, in real time, concentration levels of aromatic air toxics. Volatile organic compounds, as well as several polycyclic aromatic hydrocarbons were detected in the concentration range of 10-200 ppb in the steady-state diesel generator exhaust. The results were verified and compared with conventional extractive sampling and analytical techniques using gas chromatography/mass spectrometry (GC/MS). The high isomer selectivity of the REMPI-TOFMS instrument provided data for individual xylene isomers that are otherwise (partially) coeluting in standard GC/MS analyses. Good agreement was observed between results for volatile and semivolatile organic compounds obtained with REMPI-TOFMS and conventional extractive sampling. Transient events, such as cold start-ups of the diesel generator, resulted in sharp (less than 15 s) peak emissions that were, for benzene, up to a factor of 90 higher than the predominately constant concentrations observed during steady-state operation; warm restarts resulted in lower peak concentrations by a factor of 2.5. These fast transient emissions are only detectable using a real-time approach (1-s resolution) as demonstrated here using REMPI-TOFMS.     

Protactinium-231: A new radionuclide for AMS

For the first time, an AMS system was used to determine concentrations of the actinide Protactinium-231. ²³¹Pa has widespread applications in the earth sciences. It can be used for U-series disequilibrium dating, and ²³¹Pa is an important tracer in Paleoceanography. The Pa isotopes were measured with the compact ETH/PSI-AMS facility TANDY operating at about 300 kV. The linearity of the AMS is documented with two standard-dilution experiments and first measurements of natural samples from very different climate archives are presented. Our results show that it is possible to determine ²³¹Pa amounts in the lower femtogram (1 fg = 10⁻¹⁵ g) range with the TANDY. In natural samples, ²³¹Pa concentrations between 1 and 4 pg/g (1 pg = 10⁻¹² g) were measured with an average total error of 3% (one sigma). The average over all reproducibility of these first measurements was better than 2% with clear potential for improvement.