9 research outputs found
Key Uncertainties in the Recent Air‐Sea Flux of CO 2
The contemporary air-sea flux of CO2 is investigated by the use of an air-sea flux equation, with particular attention to the uncertainties in global values and their origin with respect to that equation. In particular, uncertainties deriving from the transfer velocity and from sparse upper ocean sampling are investigated. Eight formulations of air-sea gas transfer velocity are used to evaluate the combined standard uncertainty resulting from several sources of error. Depending on expert opinion, a standard uncertainty in transfer velocity of either ~5% or ~10% can be argued and that will contribute a proportional error in air-sea flux. The limited sampling of upper ocean fCO2 is readily apparent in the Surface Ocean CO2 Atlas (SOCAT) databases. The effect of sparse sampling on the calculated fluxes was investigated by a bootstrap method; i.e. treating each ship cruise to an oceanic region as a random episode and creating 10 synthetic datasets by randomly selecting episodes with replacement. Convincing values of global net air-sea flux can only be achieved using upper ocean data collected over several decades, but referenced to a standard year. The global annual referenced values are robust to sparse sampling, but seasonal and regional values exhibit more sampling uncertainty. Additional uncertainties are related to thermal and haline effects and to aspects of air-sea gas exchange not captured by standard models. An estimate of global net CO2 exchange referenced to 2010 of -3.0 ± 0.6 Pg C yr-1 is proposed, where the uncertainty derives primarily from uncertainty in the transfer velocit
Antiplane deformation of a bimaterial containing an interfacial crack with the account of friction. [P.] 1, Single loading
The paper presents the exact analytic solution to the antiplane problem for a non-homogeneous bimaterial medium containing
closed interfacial cracks, which faces can move relatively to each other with dry friction. The medium is subjected to the action of normal
and arbitrary single loading in a longitudinal direction. Based on the discontinuity function method the problem is reduced to the solution
of the system of singular integral-differential equations for stress and displacement discontinuities at the possible slippage zones. Influence
of loading parameters and the effects of friction on the sizes of these zones is analyzed. The stress intensity factors, stress and displacement
discontinuities, energy dissipation are determined for several characteristic types of external loading
Longitudinal shear of a bi-material with frictional sliding contact in the interfacial crack
We construct an analytical solution to the anti-plane problem of an inhomogeneous bi-
-material medium with the interfacial crack considering sliding friction. The medium is
exposed to an arbitrary normal and shear loading in the longitudinal direction. Using the
jump function method, the problem is reduced to a solution to singular integral equations for
the jumps of displacements and stresses in the areas with sliding friction. Explicit expressions
for displacements, stress intensity factors and energy dissipation are obtained. Critical load
values for determination of the onset of slippage are investigated. The effect of friction and
loading parameters on the size of the slip zone, stress intensity factors and energy dissipation
is numerically analyzed
Antiplane deformation of a bimaterial containing an interfacial crack with the account of friction 2. Repeating and cyclic loading
The paper presents the exact solution of the antiplane problem for an inhomogeneous bimaterial with the interface crack exposed
to the normal load and cyclic loading by a concentrated force in the longitudinal direction. Using discontinuity function method the
problem is reduced to the solution of singular integral equations for the displacement and stress discontinuities at the domains with sliding
friction. The paper provides the analysis of the effect of friction and loading parameters on the size of these zones. Hysteretic behaviour
of the stress and displacement discontinuities in these domains is observed
MalPhase: Fine-Grained Malware Detection Using Network Flow Data
Economic incentives encourage malware authors to constantly develop new, increasingly complex malware to steal sensitive data or blackmail individuals and companies into paying large ransoms. In 2017, the worldwide economic impact of cyberattacks is estimated to be between 445 and 600 billion USD, or 0.8% of global GDP. Traditionally, one of the approaches used to defend against malware is network traffic analysis, which relies on network data to detect the presence of potentially malicious software. However, to keep up with increasing network speeds and amount of traffic, network analysis is generally limited to work on aggregated network data, which is traditionally challenging and yields mixed results. In this paper we present MalPhase, a system that was designed to cope with the limitations of aggregated flows. MalPhase features a multi-phase pipeline for malware detection, type and family classification. The use of an extended set of network flow features and a simultaneous multi-tier architecture facilitates a performance improvement for deep learning models, making them able to detect malicious flows (>98% F1) and categorize them to a respective malware type (>93% F1) and family (>91% F1). Furthermore, the use of robust features and denoising autoencoders allows MalPhase to perform well on samples with varying amounts of benign traffic mixed in. Finally, MalPhase detects unseen malware samples with performance comparable to that of known samples, even when interlaced with benign flows to reflect realistic network environments
Intra-annual distribution of Temora longicornis
A population model of the copepod Temora longicornis coupled with the ecosystem model 3D CEMBS (Coupled Ecosystem Model of the Baltic Sea) was used to determine the intra-annual distribution of the species biomass in the Gdańsk Basin (the southern Baltic Sea). The population model for T. longicornis consists of twelve equations for twelve state variables, six for mass and six for abundance, i.e. two state variables for each of the six model stages of the development: eggs (Egg), non-feeding stage (N1), subsequent nauplii stages (N2–N6), two copepodite stages (C1–C3 and C4–C5) and adults (C6). The empirical validation of the population model was based on in situ data collected in 2010 and 2011 in the Gdańsk Deep and the western part of the Gulf of Gdańsk. The highest values of the model biomass occurred in the period of high water temperatures – in June 2010 and July 2011 in the Gulf of Gdańsk (ca 5200 mg wet weight (w.w.) m–2 and 6300 mg w.w. m–2), and for almost the whole summer in the Gdańsk Deep (24 500 mg w.w. m–2 and 27 800 mg w.w. m–2). Temora longicornis produced 4 to 5 generations per year in the Gulf of Gdańsk and Gdańsk Deep, respectively. The population model was satisfactorily verified and the calculated results were consistent with the in situ data. Despite some differences between the field and model data, the developed population model of T. longicornis is the first model for this species in the Baltic Sea and, even though it needs further improvement, it can be a useful tool for determining the population dynamics of the species and ecological relationships in the environment