2,608 research outputs found
Forensics in Industrial Control System: A Case Study
Industrial Control Systems (ICS) are used worldwide in critical
infrastructures. An ICS system can be a single embedded system working
stand-alone for controlling a simple process or ICS can also be a very complex
Distributed Control System (DCS) connected to Supervisory Control And Data
Acquisition (SCADA) system(s) in a nuclear power plant. Although ICS are widely
used to-day, there are very little research on the forensic acquisition and
analyze ICS artefacts. In this paper we present a case study of forensics in
ICS where we de-scribe a method of safeguarding important volatile artefacts
from an embedded industrial control system and several other source
Exponential Separation of Quantum and Classical Online Space Complexity
Although quantum algorithms realizing an exponential time speed-up over the
best known classical algorithms exist, no quantum algorithm is known performing
computation using less space resources than classical algorithms. In this
paper, we study, for the first time explicitly, space-bounded quantum
algorithms for computational problems where the input is given not as a whole,
but bit by bit. We show that there exist such problems that a quantum computer
can solve using exponentially less work space than a classical computer. More
precisely, we introduce a very natural and simple model of a space-bounded
quantum online machine and prove an exponential separation of classical and
quantum online space complexity, in the bounded-error setting and for a total
language. The language we consider is inspired by a communication problem (the
set intersection function) that Buhrman, Cleve and Wigderson used to show an
almost quadratic separation of quantum and classical bounded-error
communication complexity. We prove that, in the framework of online space
complexity, the separation becomes exponential.Comment: 13 pages. v3: minor change
Adrift upon a salinity-stratified sea
The structure and variability of upper-ocean properties in the Bay of Bengal (BoB) modulate air-sea interactions, which profoundly influence the pattern and intensity of monsoonal precipitation across the Indian subcontinent. In turn, the bay receives a massive amount of freshwater through river input at its boundaries and from heavy local rainfall, leading to a salinity-stratified surface ocean and shallow mixed layers. Small-scale oceanographic processes that drive variability in near-surface BoB waters complicate the tight coupling between ocean and atmosphere implicit in this seasonal feedback. Unraveling these ocean dynamics and their impact on air-sea interactions is critical to improving the forecasting of intraseasonal variability in the southwest monsoon. To that end, we deployed a wave-powered, rapidly profiling system capable of measuring the structure and variability of the upper 100 m of the BoB. The evolution of upper-ocean structure along the trajectory of the instrumentâs roughly two-week drift, along with direct estimates of vertical fluxes of salt and heat, permit assessment of the contributions of various phenomena to temporal and spatial variability in the surface mixed layer depth. Further, these observations suggest that the particular âbarrier-layerâ stratification found in the BoB may decrease the influence of the wind on mixing processes in the interior, thus isolating the upper ocean from the interior below, and tightening its coupling to the atmosphere abov
Quantum Algorithm for Dynamic Programming Approach for DAGs. Applications for Zhegalkin Polynomial Evaluation and Some Problems on DAGs
In this paper, we present a quantum algorithm for dynamic programming
approach for problems on directed acyclic graphs (DAGs). The running time of
the algorithm is , and the running time of the
best known deterministic algorithm is , where is the number of
vertices, is the number of vertices with at least one outgoing edge;
is the number of edges. We show that we can solve problems that use OR,
AND, NAND, MAX and MIN functions as the main transition steps. The approach is
useful for a couple of problems. One of them is computing a Boolean formula
that is represented by Zhegalkin polynomial, a Boolean circuit with shared
input and non-constant depth evaluating. Another two are the single source
longest paths search for weighted DAGs and the diameter search problem for
unweighted DAGs.Comment: UCNC2019 Conference pape
Relative hyperbolicity and similar properties of one-generator one-relator relative presentations with powered unimodular relator
A group obtained from a nontrivial group by adding one generator and one
relator which is a proper power of a word in which the exponent-sum of the
additional generator is one contains the free square of the initial group and
almost always (with one obvious exception) contains a non-abelian free
subgroup. If the initial group is involution-free or the relator is at least
third power, then the obtained group is SQ-universal and relatively hyperbolic
with respect to the initial group.Comment: 11 pages. A Russian version of this paper is at
http://mech.math.msu.su/department/algebra/staff/klyachko/papers.htm V3:
revised following referee's comment
Multi frequency evaporative cooling to BEC in a high magnetic field
We demonstrate a way to circumvent the interruption of evaporative cooling
observed at high bias field for Rb atoms trapped in the (F=2, m=+2)
ground state. Our scheme uses a 3-frequencies-RF-knife achieved by mixing two
RF frequencies. This compensates part of the non linearity of the Zeeman
effect, allowing us to achieve BEC where standard 1-frequency-RF-knife
evaporation method did not work. We are able to get efficient evaporative
cooling, provided that the residual detuning between the transition and the RF
frequencies in our scheme is smaller than the power broadening of the RF
transitions at the end of the evaporation ramp.Comment: 12 pages, 2 figure
The origin of the anomalously strong influence of out-of-plane disorder on high-Tc superconductivity
The electronic structure of Bi2Sr2-xRxCuOy(R=La, Eu) near the (pi,0) point of
the first Brillouin zone was studied by means of angle-resolved photoemission
spectroscopy (ARPES). The temperature T* above which the pseudogap structure in
the ARPES spectrum disappears was found to have an R dependence that is
opposite to that ofthe superconducting transition temperature Tc. This
indicates that the pseudogap state is competing with high-Tc superconductivity,
and the large Tc suppression observed with increasing the out-of-plane disorder
is due to the stabilization of the pseudogap state.Comment: 4 pages, 4 figure
Double diffusion, shear instabilities, and heat impacts of a pacific summer water intrusion in the Beaufort Sea
© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fine, E., MacKinnon, J., Alford, M., Middleton, L., Taylor, J., Mickett, J., Cole, S., Couto, N., Boyer, A., & Peacock, T. Double diffusion, shear instabilities, and heat impacts of a pacific summer water intrusion in the Beaufort Sea. Journal of Physical Oceanography, 52(2), (2022): 189â203, https://doi.org/10.1175/jpo-d-21-0074.1.Pacific Summer Water eddies and intrusions transport heat and salt from boundary regions into the western Arctic basin. Here we examine concurrent effects of lateral stirring and vertical mixing using microstructure data collected within a Pacific Summer Water intrusion with a length scale of âŒ20 km. This intrusion was characterized by complex thermohaline structure in which warm Pacific Summer Water interleaved in alternating layers of O(1) m thickness with cooler water, due to lateral stirring and intrusive processes. Along interfaces between warm/salty and cold/freshwater masses, the density ratio was favorable to double-diffusive processes. The rate of dissipation of turbulent kinetic energy (Δ) was elevated along the interleaving surfaces, with values up to 3 Ă 10â8 W kgâ1 compared to background Δ of less than 10â9 W kgâ1. Based on the distribution of Δ as a function of density ratio RÏ, we conclude that double-diffusive convection is largely responsible for the elevated Δ observed over the survey. The lateral processes that created the layered thermohaline structure resulted in vertical thermohaline gradients susceptible to double-diffusive convection, resulting in upward vertical heat fluxes. Bulk vertical heat fluxes above the intrusion are estimated in the range of 0.2â1 W mâ2, with the localized flux above the uppermost warm layer elevated to 2â10 W mâ2. Lateral fluxes are much larger, estimated between 1000 and 5000 W mâ2, and set an overall decay rate for the intrusion of 1â5 years.This work was supported by ONR Grant N00014-16-1-2378 and NSF Grants PLR 14-56705 and PLR-1303791, NSF Graduate Research Fellowship Grant DGE-1650112, as well as by the Postdoctoral Scholar Program at Woods Hole Oceanographic Institution, with funding provided by the Weston Howland Jr. Postdoctoral Scholarship
Least Upper Delay Bound for VBR Flows in Networks-on- Chip with Virtual Channels
Real-time applications such as multimedia and gaming require stringent performance guarantees, usually enforced by a tight upper bound on the maximum end-to-end delay. For FIFO multiplexed on-chip packet switched networks we consider worst-case delay bounds for Variable Bit-Rate (VBR) flows with aggregate scheduling, which schedules multiple flows as an aggregate flow. VBR Flows are characterized by a maximum transfer size, peak rate, burstiness, and average sustainable rate. Based on network calculus, we present and prove theorems to derive per-flow end-to-end Equivalent Service Curves (ESC) which are in turn used for computing Least Upper Delay Bounds (LUDBs) of individual flows. In a realistic case study we find that the end-to-end delay bound is up to 46.9% more accurate than the case without considering the traffic peak behavior. Likewise, results also show similar improvements for synthetic traffic patterns. The proposed methodology is implemented in C++ and has low run-time complexity, enabling quick evaluation for large and complex SoCs
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