53 research outputs found
The shape of the electron and muon lateral distribution functions of extensive air showers
The lateral density data obtained for different secondaries of an extensive
air shower (EAS) from an array of detectors are usually described by some
suitable lateral density functions (LDFs). Analyzing non-vertical simulated
EASs generated with the CORSIKA code, it is found that the lateral and polar
density distributions of electrons and muons are asymmetric in the ground
plane. It means that typical expressions for symmetric lateral density
functions (SLDFs) (\emph{e.g.} the Nishimura-Kamata-Greisen function) are
inadequate to reconstruct the lateral and polar dependencies of such asymmetric
electron or muon densities accurately. In order to provide a more consistent
LDF for non-vertical shower reconstruction in the ground plane, the paper
considers the issue of the modification of the SLDF analytically. The asymmetry
arising from additional attenuation and correction of the positional
coordinates (radial and polar) of cascade particles causes a gap length between
the center of concentric equidensity ellipses and the EAS core. A toy function
is introduced as a basic LDF to describe the asymmetric lateral and polar
density distributions of electrons or muons of EASs, thereby predicting the gap
length parameter. Consequently, the desired LDF describing the asymmetric
density distributions of electrons and muons of EASs has emerged. We compare
results from detailed simulations with the predictions of the analytical
parametrization. The LDF derived in this work is found to be well-suited to
reconstruct EASs in the ground plane directly.Comment: 18 pages, 37 figure
Explaining the characteristics of lateral shower age of cosmic ray extensive air showers
A simple analytical argument is proposed for a possible explanation of the
characteristics of the lateral shower age () of proton
()/nuclei-initiated showers. The analytical argument states that lateral
density distribution (LDD) of electrons of a -initiated shower is due to
superposition of several electromagnetic (EM) sub-showers developed at a very
early stage in the atmosphere from the decay of neutral pions (s).
Thanks to the superposition property of the electron LDD in a shower, a
plausible analytical parametrization has been worked out by giving well
represented analytic function for the electron LDDs of - and
-initiated showers. Based on cosmic ray extensive air shower
simulations, we have validated how the various characteristics of can be
understood in the context of the present analytical argument. The parameter
of a shower and its correlations with the shower ages of electron- and
-initiated showers supports the idea that the result of superposition
of several EM sub-showers initiated by s with varied energies at a
very early stage might produce the LDD of electrons of a shower. It is also
noticed with the simulated data that the stated feature still persists
concerning the notion of the local shower age parameter.Comment: 9 pages, 6 figures, revision submitted for publication in a Journa
A novel approach for deducing the mass composition of cosmic rays from lateral densities of EAS particles
A Monte Carlo (MC) simulation study of cosmic ray (CR) extensive air showers
(EAS) has been carried out in the energy regime of the KASCADE experiment. From
the characteristics of lateral distributions of electrons and muons of
simulated EAS, some important EAS observables are extracted by a novel
approach, and their CR mass-sensitivity is demonstrated. The study takes into
account the issue of the experimental lateral density profiles of EAS electrons
and muons after introducing the notion of the local age and segmented slope
parameters, aimed to extract information on CR mass composition from observed
data. The estimated lateral shower age and slope from the analysis of the
KASCADE data (KCDC) agrees with the idea of a gradual change of CR mass
composition from light to heavy around the knee.Comment: 8 pages, 10 figures, Accepted in a Journa
ASSURE: RTL Locking Against an Untrusted Foundry
Semiconductor design companies are integrating proprietary intellectual
property (IP) blocks to build custom integrated circuits (IC) and fabricate
them in a third-party foundry. Unauthorized IC copies cost these companies
billions of dollars annually. While several methods have been proposed for
hardware IP obfuscation, they operate on the gate-level netlist, i.e., after
the synthesis tools embed the semantic information into the netlist. We propose
ASSURE to protect hardware IP modules operating on the register-transfer level
(RTL) description. The RTL approach has three advantages: (i) it allows
designers to obfuscate IP cores generated with many different methods (e.g.,
hardware generators, high-level synthesis tools, and pre-existing IPs). (ii) it
obfuscates the semantics of an IC before logic synthesis; (iii) it does not
require modifications to EDA flows. We perform a cost and security assessment
of ASSURE.Comment: Submitted to IEEE Transactions on VLSI Systems on 11-Oct-2020,
28-Jan-202
INVICTUS: Optimizing Boolean Logic Circuit Synthesis via Synergistic Learning and Search
Logic synthesis is the first and most vital step in chip design. This steps
converts a chip specification written in a hardware description language (such
as Verilog) into an optimized implementation using Boolean logic gates.
State-of-the-art logic synthesis algorithms have a large number of logic
minimization heuristics, typically applied sequentially based on human
experience and intuition. The choice of the order greatly impacts the quality
(e.g., area and delay) of the synthesized circuit. In this paper, we propose
INVICTUS, a model-based offline reinforcement learning (RL) solution that
automatically generates a sequence of logic minimization heuristics ("synthesis
recipe") based on a training dataset of previously seen designs. A key
challenge is that new designs can range from being very similar to past designs
(e.g., adders and multipliers) to being completely novel (e.g., new processor
instructions). %Compared to prior work, INVICTUS is the first solution that
uses a mix of RL and search methods joint with an online out-of-distribution
detector to generate synthesis recipes over a wide range of benchmarks. Our
results demonstrate significant improvement in area-delay product (ADP) of
synthesized circuits with up to 30\% improvement over state-of-the-art
techniques. Moreover, INVICTUS achieves up to runtime reduction
(iso-ADP) compared to the state-of-the-art.Comment: 20 pages, 8 figures and 15 table
Development of a Fiber Optic Sensor for Online Monitoring of Thin Coatings
 The thickness measurement of gas, liquid and solid layers is not only important for the basic research on nanoscience but equally valuable in contemporary applied biomedical research. Here, we have developed an optical spectroscopy based technique for the online monitoring of thin films (coatings). A low cost light emitting diode (LED) source combined with a fiber optic bundle and grating based spectrograph have been used to generate white light interferogram. We have monitored online change of refractive index of an air film (~4 μm thickness) with temperature following the change in the intensity profile of the interferogram. A thin film of water between two cover slips (thin glass plates) has also been monitored. We have proposed a schematic for further lowering the cost of the developed instrument for the online monitoring of the coating thickness (semitransparent liquid/gas/solid films) during manufacturing/processing. A brief theoretical analysis on the detection limit of the developed technique has also been discussed in the paper
Feldspar mineralogy and rare-earth element (re)mobilization in iron-oxide copper gold systems from South Australia: a nanoscale study
Nanoscale characterization (TEM on FIB-SEM-prepared foils) was undertaken on feldspars undergoing
transformation from early post-magmatic (deuteric) to hydrothermal stages in granites hosting the Olympic Dam
Cu-U-Au-Ag deposit, and from the Cu-Au skarn at Hillside within the same iron-oxide copper-gold (IOCG) province, South Australia. These include complex perthitic textures, anomalously Ba-, Fe-, or REE-rich compositions, andREE-flourocarbonate + molybdenite assemblages which pseudomorph pre-existing feldspars.
Epitaxial orientations between cryptoperthite (magmatic), patch perthite (dueteric) and replacive albite
(hydrothermal) within vein perthite support interface-mediated reactions between pre-existing alkali-feldspars
and pervading fluid, irrespective of micro-scale crystal morphology. Such observations are consistent with a
coupled dissolution-reprecipitation reaction mechanism, which assists in grain-scale element remobilization via
the generation of transient interconnected microporosity. Micro-scale aggregates of hydrothermal hyalophane
(Ba-rich K-feldspar), crystallizing within previously albitized areas of andesine, reveal a complex assemblage of calc-silicate, As-bearing fluorapatite and Fe oxides along reaction boundaries in the enclosing albite-sericite assemblage typical of deuteric alteration. Such inclusions are good REE repositories and their presence supports REE remobilization at the grain-scale during early hydrothermal alteration. Iron-metasomatism is recognized by nanoscale maghemite inclusions within ‘red-stained’ orthoclase, as well as by hematite in REE-fluorocarbonates, which reflect broader-scale zonation patterns typical for IOCG systems. Potassium-feldspar from the contact between alkali-granite and skarn at Hillside is characterized by 100–1000 ppm REE, attributable to pervasive nanoscale inclusions of calc-silicates, concentrated along microfractures, or pore-attached. Feldspar replacement by REE-fluorcarbonates at Olympic Dam and nanoscale calc-silicate inclusions in feldspar at Hillside are both strong evidence for the role of feldspars in concentrating REE during intense metasomatism. Differences in mineralogical expression are due to the availability of associated elements. Lattice-scale intergrowths of assemblages indicative of Fe-metasomatism, REE-enrichment and sulfide deposition at Olympic Dam are evidence for a spatial and temporal relationship between these processes
Targeted Greybox Fuzzing with Static Lookahead Analysis
Automatic test generation typically aims to generate inputs that explore new
paths in the program under test in order to find bugs. Existing work has,
therefore, focused on guiding the exploration toward program parts that are
more likely to contain bugs by using an offline static analysis.
In this paper, we introduce a novel technique for targeted greybox fuzzing
using an online static analysis that guides the fuzzer toward a set of target
locations, for instance, located in recently modified parts of the program.
This is achieved by first semantically analyzing each program path that is
explored by an input in the fuzzer's test suite. The results of this analysis
are then used to control the fuzzer's specialized power schedule, which
determines how often to fuzz inputs from the test suite. We implemented our
technique by extending a state-of-the-art, industrial fuzzer for Ethereum smart
contracts and evaluate its effectiveness on 27 real-world benchmarks. Using an
online analysis is particularly suitable for the domain of smart contracts
since it does not require any code instrumentation---instrumentation to
contracts changes their semantics. Our experiments show that targeted fuzzing
significantly outperforms standard greybox fuzzing for reaching 83% of the
challenging target locations (up to 14x of median speed-up)
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