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1. Robust PDF Malware Detection with Image Visualization and Processing Techniques

   https://doi.org/10.1109/ICDIS.2019.00024  

   Corum, Andrew ; Jenkins, Donovan ; Zheng, Jun ( January 2019 , 2019 2nd International Conference on Data Intelligence and Security (ICDIS))

   PDF, as one of most popular document file format, has been frequently utilized as a vector by attackers to covey malware due to its flexible file structure and the ability to embed different kinds of content. In this paper, we propose a new learning-based method to detect PDF malware using image processing and processing techniques. The PDF files are first converted to grayscale images using image visualization techniques. Then various image features representing the distinct visual characteristics of PDF malware and benign PDF files are extracted. Finally, learning algorithms are applied to create the classification models to classify a new PDF file as malicious or benign. The performance of the proposed method was evaluated using Contagio PDF malware dataset. The results show that the proposed method is a viable solution for PDF malware detection. It is also shown that the proposed method is more robust to resist reverse mimicry attacks than the state-of-art learning-based method. 

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2. Reduction of PDF uncertainty in the measurement of the weak mixing angle at the ATLAS experiment *

   https://doi.org/10.1088/1674-1137/abe36d  

   Fu, Yao ; Yang, Siqi ; Liu, Minghui ; Han, Liang ; Hou, Tie-Jiun ; Schmidt, Carl ; Wang, Chen ; Yuan, C. -P. ( May 2021 , Chinese Physics C)

   We investigate the parton distribution function (PDF) uncertainty in the measurement of the effective weak mixing angleat the CERN Large Hadron Collider (LHC). The PDF-induced uncertainty is large in proton-proton collisions at the LHC due to the dilution effect. The measurement of the Drell-Yan forward-backward asymmetry () at the LHC can be used to reduce the PDF uncertainty in themeasurement. However, when including the full mass range of lepton pairs in thedata analysis, the correlation between the PDF updating procedure and theextraction leads to a sizable bias in the obtainedvalue. From our studies, we find that the bias can be significantly reduced by removing Drell-Yan events with invariant mass around theZ-pole region, while most of the sensitivity in reducing the PDF uncertainty remains. Furthermore, the lepton charge asymmetry in theWboson events as a function of the rapidity of the charged leptons,, is known to be another observable which can be used to reduce the PDF uncertainty in themeasurement. The constraint fromis complementary to that from, and thus no bias affects theextraction. The studies are performed using the error PDF Updating Method Package (ePump), which is based on Hessian updating methods. In this article, the CT14HERA2 PDF set is used as an example.

    

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3. The PDF4LHC21 combination of global PDF fits for the LHC Run III*

   https://doi.org/10.1088/1361-6471/ac7216  

   Ball, Richard D ; Butterworth, Jon ; Cooper-Sarkar, Amanda M ; Courtoy, Aurore ; Cridge, Thomas ; De Roeck, Albert ; Feltesse, Joel ; Forte, Stefano ; Giuli, Francesco ; Gwenlan, Claire ; et al ( July 2022 , Journal of Physics G: Nuclear and Particle Physics)

   Abstract A precise knowledge of the quark and gluon structure of the proton, encoded by the parton distribution functions (PDFs), is of paramount importance for the interpretation of high-energy processes at present and future lepton–hadron and hadron–hadron colliders. Motivated by recent progress in the PDF determinations carried out by the CT, MSHT, and NNPDF groups, we present an updated combination of global PDF fits: PDF4LHC21. It is based on the Monte Carlo combination of the CT18, MSHT20, and NNPDF3.1 sets followed by either its Hessian reduction or its replica compression. Extensive benchmark studies are carried out in order to disentangle the origin of the differences between the three global PDF sets. In particular, dedicated fits based on almost identical theory settings and input datasets are performed by the three groups, highlighting the role played by the respective fitting methodologies. We compare the new PDF4LHC21 combination with its predecessor, PDF4LHC15, demonstrating their good overall consistency and a modest reduction of PDF uncertainties for key LHC processes such as electroweak gauge boson production and Higgs boson production in gluon fusion. We study the phenomenological implications of PDF4LHC21 for a representative selection of inclusive, fiducial, and differential cross sections at the LHC. The PDF4LHC21 combination is made available via the LHAPDF library and provides a robust, user-friendly, and efficient method to estimate the PDF uncertainties associated to theoretical calculations for the upcoming Run III of the LHC and beyond. 

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4. On the Statistics of Elsasser Increments in Solar Wind and Magnetohydrodynamic Turbulence

   https://doi.org/10.3847/2041-8213/ac92f6  

   Palacios, Juan C. ; Bourouaine, Sofiane ; Perez, Jean C. ( November 2022 , The Astrophysical Journal Letters)

   In this Letter we investigate the dependency with scale of the empirical probability distribution functions (PDF) of Elsasser increments using large sets ofWINDdata (collected between 1995 and 2017) near 1 au. The empirical PDF are compared to the ones obtained from high-resolution numerical simulations of steadily driven, homogeneous reduced MHD turbulence on a 2048³rectangular mesh. A large statistical sample of Alfvénic increments is obtained by using conditional analysis based on the solar wind average properties. The PDF tails obtained from observations and numerical simulations are found to have exponential behavior in the inertial range, with an exponential decrement that satisfies power laws of the formα_l∝l^−μ, wherelis the scale size, withμbetween 0.17 and 0.25 for observations and 0.43 for simulations. PDF tails were extrapolated assuming their exponential behavior extends to arbitrarily large increments in order to determine structure function scaling laws at very high orders. Our results point to potentially universal scaling laws governing the PDF of Elsasser increments and to an alternative approach to investigate high-order statistics in solar wind observations.

    

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5. Precipitation characteristic changes due to global warming in a high‐resolution (16 km) ECMWF simulation

   https://doi.org/10.1002/qj.3432  

   Feng, Xuelei ; Liu, Chuntao ; Xie, Feiqin ; Lu, Jian ; Chiu, Long S. ; Tintera, George ; Chen, Baohua ( January 2019 , Quarterly Journal of the Royal Meteorological Society)

   Changes in precipitation amount, intensity and frequency in response to global warming are examined using global high‐resolution (16 km) climate model simulations based on the European Centre for Medium‐range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) conducted under Project Athena.

   Our study shows the increases of zonal‐mean total precipitation in all latitudes except the northern subtropics (15°–30°N) and southern subtropics‐to‐midlatitudes (30°–40°S). The probability distribution function (PDF) changes in different latitudes suggest a higher occurrence of light precipitation (LP; ≤1 mm/day) and heavy precipitation (HP; ≥30 mm/day) at the expense of moderate precipitation reduction (MP; 1–30 mm/day) from Tropics to midlatitudes, but an increase in all categories of precipitation in polar regions.

   On the other hand, the PDF change with global warming in different precipitation climatological zones presents another image. For all regions and seasons examined, there is an HP increase at the cost of MP, but LP varies. The reduced MP in richer precipitation zones resides in the PDF peak intensities, which linearly increase with the precipitation climatology zones. In particular in the Tropics (20°S to 20°N), the precipitation PDF has a flatter distribution (i.e. HP and LP increases with MP reduction) except for the Sahara Desert. In the primary precipitation zones in the subtropics (20°–40°) of both hemispheres, precipitation over land switches toward higher intensity (HP increases, but MP and LP decrease) in both winter and summer, while precipitation over ocean in both seasons shows a flattening trend in the intensity distribution. For the major precipitation zones of the mid‐to‐high latitude belt (40°–70°), PDF of precipitation tends to be flatter over ocean in summer, but switches toward higher intensities over land in both summer and winter, as well as over ocean in winter.

    

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