Polytechnic University of Milan

About: Polytechnic University of Milan is a education organization based out in Milan, Italy. It is known for research contribution in the topics: Computer science & Finite element method. The organization has 18231 authors who have published 58416 publications receiving 1229711 citations. The organization is also known as: PoliMi & L-NESS.

BitIodine: Extracting Intelligence from the Bitcoin Network

Abstract: Bitcoin, the famous peer-to-peer, decentralized electronic currency system, allows users to benefit from pseudonymity, by generating an arbitrary number of aliases (or addresses) to move funds. However, the complete history of all transactions ever performed, called “blockchain”, is public and replicated on each node. The data it contains is difficult to analyze manually, but can yield a high number of relevant information. In this paper we present a modular framework, BitIodine, which parses the blockchain, clusters addresses that are likely to belong to a same user or group of users, classifies such users and labels them, and finally visualizes complex information extracted from the Bitcoin network. BitIodine labels users semi-automatically with information on their identity and actions which is automatically scraped from openly available information sources. BitIodine also supports manual investigation by finding paths and reverse paths between addresses or users. We tested BitIodine on several real-world use cases, identified an address likely to belong to the encrypted Silk Road cold wallet, or investigated the CryptoLocker ransomware and accurately quantified the number of ransoms paid, as well as information about the victims. We release a prototype of BitIodine as a library for building Bitcoin forensic analysis tools.

Silicon drift detectors for high resolution room temperature X-ray spectroscopy

Abstract: New cylindrical silicon drift detectors have been designed, fabricated and tested. They comprise an integrated on-chip amplifier system with continuous reset, on-chip voltage divider, electron accumulation layer stabilizer, large area, homogeneous radiation entrance window and a drain for surface generated leakage current. The test of the 3.5 mm2 large individual devices, which have also been grouped together to form a sensitive area up to 21 mm2 have shown the following spectroscopic results: at room temperature (300 K) the devices have shown a full width at half maximum at the MnKα line of a radioactive 55 Fe source of 225 eV with shaping times of 250 to 500 ns. At −20°C the resolution improves to 152 eV at 2 μs Gaussian shaping. At temperatures below 200 K the energy resolution is below 140 eV. With the implementation of a digital filtering system the resolution approaches 130 eV. The system was operated with count rates up to 800 000 counts per second and per readout node, still conserving the spectroscopic qualities of the detector system.

Detailed modeling of PAH and soot formation in a laminar premixed benzene/oxygen/argon low-pressure flame

Abstract: Combustion-generated polycyclic aromatic hydrocarbons (PAH) and soot particles are of significant environmental concern whereas controlled combustion is of increasing interest for the synthesis of carbonaceous nanostructures such as fullerenic material. Improved understanding of chemical and physical processes involved in PAH and soot formation is required to correlate operating conditions with emission characteristics. A detailed kinetic model describing the formation and consumption of PAH and soot in fuel-rich hydrocarbon combustion has been developed. Using a sectional approach, large PAH and carbonaceous particles with diameters of up to ≈70 nm are defined as classes (BINs) covering given mass ranges. Numbers of carbon and hydrogen atoms corresponding to their average masses are assigned to each BIN, accounting for a decrease in H/C ratios with increasing particle size. The model has been successfully tested for a rich premixed benzene/oxygen/argon flame ( ϕ = 2.4, 10% argon, v = 25 cm s −1 , 5.33 kPa). Model predictions are compared with published experimental data including mole fraction profiles of individual PAH and concentration as well as number density profiles of soot. Reactions of PAH radicals with PAH and between PAH radicals were found to be the dominant pathway to soot nuclei. Surface growth contributes ≈75% to the final particle mass, and reaction of acetylene with particle radicals is the major growth pathway. Surface growth reactions are involved in PAH depletion in the postflame zone. Particle coagulation involving BINs and BIN radicals significantly contributes to the formation of progressively larger particles whereas oxidation by OH plays a non-negligible role in their depletion.

Some Parallel Thinning Algorithms for Digital Pictures

Abstract: If a picture contains elongated objects of different thicknesses, one can make measurements on it which are thickness-invariant by first transforming it so that each object is thinned down to a \"medial line\" of constant thickness. Several algorithms are described which perform such a thinning transformation when applied to the picture in parallel. It is proved that these algorithms do not change the connectivity properties of the picture.