21 research outputs found
3D morphological variability in foraminifera unravel environmental changes in the Baltic Sea entrance over the last 200Â years
Human activities in coastal areas have intensified over the last 200 years, impacting also high-latitude regions such as the Baltic Sea. Benthic foraminifera, protists often with calcite shells (tests), are typically well preserved in marine sediments and known to record past bottom-water conditions. Morphological analyses of marine shells acquired by microcomputed tomography (µCT) have made significant progress toward a better understanding of recent environmental changes. However, limited access to data processing and a lack of guidelines persist when using open-source software adaptable to different microfossil shapes. This study provides a post-data routine to analyze the entire test parameters: average thickness, calcite volume, calcite surface area, number of pores, pore density, and calcite surface area/volume ratio. A case study was used to illustrate this method: 3D time series (i.e., 4D) of Elphidium clavatum specimens recording environmental conditions in the Baltic Sea entrance from the period early industrial (the 1800s) to present-day (the 2010 s). Long-term morphological trends in the foraminiferal record revealed that modern specimens have ∼28% thinner tests and ∼91% more pores than their historic counterparts. However, morphological variability between specimens and the BFAR (specimens cm−2 yr−1) in E. clavatum were not always synchronous. While the BFAR remained unchanged, morphological variability was linked to natural environmental fluctuations in the early industrial period and the consequences of anthropogenic climate change in the 21st century. During the period 1940–2000 s, the variations in BFAR were synchronous with morphological variability, revealing both the effects of the increase in human activities and major hydrographic changes. Finally, our interpretations, based on E. clavatum morphological variations, highlight environmental changes in the Baltic Sea area, supporting those documented by the foraminiferal assemblages
Numerical simulations of NMR relaxation in chalk using local Robin boundary conditions
The interpretation of nuclear magnetic resonance (NMR) data is of interest in
a number of fields. In \"{O}gren [Eur. Phys. J. B (2014) 87: 255] local
boundary conditions for random walk simulations of NMR relaxation in digital
domains were presented. Here, we have applied those boundary conditions to
large, three-dimensional (3D) porous media samples. We compared the random walk
results with known solutions and then applied them to highly structured 3D
domains, from images derived using synchrotron radiation CT scanning of North
Sea chalk samples. As expected, there were systematic errors caused by
digitalization of the pore surfaces so we quantified those errors, and by using
linear local boundary conditions, we were able to significantly improve the
output. We also present a technique for treating numerical data prior to input
into the ESPRIT algorithm for retrieving Laplace components of time series from
NMR data (commonly called -inversion)
TACAN: Transmitter Authentication through Covert Channels in Controller Area Networks
Nowadays, the interconnection of automotive systems with modern digital
devices offers advanced user experiences to drivers. Electronic Control Units
(ECUs) carry out a multitude of operations using the insecure Controller Area
Network (CAN) bus in automotive Cyber-Physical Systems (CPSs). Therefore,
dangerous attacks, such as disabling brakes, are possible and the safety of
passengers is at risk. In this paper, we present TACAN (Transmitter
Authentication in CAN), which provides secure authentication of ECUs by
exploiting the covert channels without introducing CAN protocol modifications
or traffic overheads (i.e., no extra bits or messages are used). TACAN turns
upside-down the originally malicious concept of covert channels and exploits it
to build an effective defensive technique that facilitates transmitter
authentication via a trusted Monitor Node. TACAN consists of three different
covert channels for ECU authentication: 1) Inter-Arrival Time (IAT)-based,
leveraging the IATs of CAN messages; 2) offset-based, exploiting the clock
offsets of CAN messages; 3) Least Significant Bit (LSB)-based, concealing
authentication messages into the LSBs of normal CAN data. We implement the
covert channels on the University of Washington (UW) EcoCAR testbed and
evaluate their performance through extensive experiments. We demonstrate the
feasibility of TACAN, highlighting no traffic overheads and attesting the
regular functionality of ECUs. In particular, the bit error ratios are within
0.1% and 0.42% for the IAT-based and offset-based covert channels,
respectively. Furthermore, the bit error ratio of the LSB-based covert channel
is equal to that of a normal CAN bus, which is 3.1x10^-7%.Comment: To be published in ACM/IEEE ICCPS 201