k-fingerprinting: a Robust Scalable Website Fingerprinting Technique

Website fingerprinting enables an attacker to infer which web page a client is browsing through encrypted or anonymized network connections. We present a new website fingerprinting technique based on random decision forests and evaluate performance over standard web pages as well as Tor hidden services, on a larger scale than previous works. Our technique, k-fingerprinting, performs better than current state-of-the-art attacks even against website fingerprinting defenses, and we show that it is possible to launch a website fingerprinting attack in the face of a large amount of noisy data. We can correctly determine which of 30 monitored hidden services a client is visiting with 85% true positive rate (TPR), a false positive rate (FPR) as low as 0.02%, from a world size of 100,000 unmonitored web pages. We further show that error rates vary widely between web resources, and thus some patterns of use will be predictably more vulnerable to attack than others.Comment: 17 page

Controlled synthesis of Pt3Sn/C electrocatalysts with exclusive Sn-Pt interaction designed for use in direct methanol fuel cells

Alloy-type Sn-Pt/C electrocatalysts with Pt/Sn= 1.8-3.0 ratios and exclusive Sn-Pt interaction have been prepared by means of Controlled Surface Reactions (CSRs). As demonstrated by XRD the incorporation of Sn onto Pt/C was achieved satisfactorily yielding a near-stoichiometric fcc Pt3Sn alloy phase along with a certain amount of the Pt(1-x)Snx solid solution. The content and dispersion of the fcc Pt3Sn phase within the electrocatalysts can be controlled by tuning the reaction conditions of CSRs. No evidence of the presence of SnO2 phases in the Sn-modified Pt/C samples were found by means of the XRD and EDS analysis. According to in situ XPS studies the pre-treatment in hydrogen at 350°C resulted in complete reduction of tin to Sn0. These results demonstrate that the method of CSRs is a powerful tool to create of Pt-Sn bimetallic nanoparticles exclusively, without tin introduction onto the carbon support. The performance of the intermetallic SnPt/C catalysts in the CO and methanol electrooxidation reactions depends on the actual composition of the exposed surface and the size of bimetallic particles. In the consecutive tin introduction the decrease of the amount of SnEt4 precursor added per period, accompanied with an increase of the number of anchoring periods, resulted in an increase of the activity in both electrooxidation reactions as a consequence of an optimal balance of Pt/Sn ratio, the content of fcc Pt3Sn phase and metal particle size. It was demonstrated that the increasing tin content above a certain (optimal) amount gives rise to a negative effect on the catalyst performance in the CO and methanol electrooxidation

Predicting weighing deviations in the dispatch workflow process: a case study in a cement industry

The emergence of the Industry 4.0 concept and the profound digital transformation of the industry plays a crucial role in improving organisations' supply chain (SC) performance, consequently achieving a competitive advantage. The order fulfilment process (OFP) consists of one of the key business processes for the organization SC and represents a core process for the operational logistics flow. The dispatch workflow process consists of an integral part of the OFP and is also a crucial process in the SC of cement industry organizations. In this work, we focus on enhancing the order fulfilment process by improving the dispatch workflow process, specifically with respect to the cement loading process. Thus, we proposed a machine learning (ML) approach to predict weighing deviations in the cement loading process. We adopted a realistic and robust rolling window scheme to evaluate six classification models in a real-world case study, from which the random forest (RF) model provides the best predictive performance. We also extracted explainable knowledge from the RF classifier by using the Shapley additive explanations (SHAP) method, demonstrating the influence of each input data attribute used in the prediction process.This work is supported by European Structural and Investment Funds in the FEDER component, through the Operational Competitivenessand Internationalization Programme (COMPETE 2020 ) [Project nº 069716; Funding Reference: POCI-01-0247-FEDER-069716]

Spray-dried Ni catalysts with tailored properties for CO2 methanation

A catalyst production method that enables the independent tailoring of the structural properties of the catalyst, such as pore size, metal particle size, metal loading or surface area, allows to increase the efficiency of a catalytic process. Such tailoring can help to make the valorization of CO2 into synthetic fuels on Ni catalysts competitive to conventional fossil fuel production. In this work, a new spray-drying method was used to produce Ni catalysts supported on SiO2 and Al2O3 nanoparticles with tunable properties. The influence of the primary particle size of the support, different metal loadings, and heat treatments were applied to investigate the potential to tailor the properties of catalysts. The catalysts were examined with physical and chemical characterization methods, including X-ray diffraction, temperature-programmed reduction, and chemisorption. A temperature-scanning technique was applied to screen the catalysts for CO2 methanation. With the spray-drying method presented here, well-organized porous spherical nanoparticles of highly dispersed NiO nanoparticles supported on silica with tunable properties were produced and characterized. Moreover, the pore size, metal particle size, and metal loading can be controlled independently, which allows to produce catalyst particles with the desired properties. Ni/SiO2 catalysts with surface areas of up to 40 m2 g−1 with Ni crystals in the range of 4 nm were produced, which exhibited a high activity for the CO2 methanation

Cobalt-based Catalysts for the Conversion of Biomass-derived Syngas to Ethanol and Higher Oxygenates

Higher oxygenates synthesis by catalytic conversion of synthesis gas are the potential approaches to replace fossil fuels and produce chemicals for pharmaceutical manufacture, detergents and polymer industry. Cobalt-based catalysts are the most promising catalysts to replace noble metal catalysts for producing ethanol, acetaldehyde and higher oxygenates via CO hydrogenation. The formation of higher oxygenates requires active sites that can adsorb CO non-dissociatively and insert to the alkyl intermediate. The hydrogenation of the CO-inserted intermediates yields C2 and C2+ oxygenates. The main focus of this study is to investigate the active site for non-dissociative CO adsorption, and the modification of the catalysts to enhance the production rate for higher oxygenates. The effect of different structural promoters are investigated on copper-cobalt catalysts. Three cobalt–copper catalysts singly promoted with La, Zr, or Al were studied for catalytic conversion of syngas to higher alcohols. CO hydrogenation was carried out, and catalyst activity and selectivity to higher alcohols are the greatest on La promoted catalyst. La promoted catalyst differs from the other two in the first 10 h of time-on-stream, with the product distribution shifted to favor oxygenates formation. These results suggest changes on La promoted catalyst during the reaction. The DRIFTS study of CO adsorption behavior on La promoted copper-cobalt catalyst observed that CO linearly adsorbed on Co2C site. A cobalt carbide phase was formed in the reaction, and Co2C is able to adsorb CO associatively and insert to the intermediates. X-ray absorption techniques detected the existence of cobalt carbide in the lanthanum promoted cobalt-copper catalysts. A further reaction study on a promoter-free bulk Co2C catalyst also detected higher oxygenates as products. To improve the selectivity to ethanol and higher oxygenates and provide a stable catalyst for CO hydrogenation, a novel method using metal organic framework as precursors was performed to synthesize a series of potassium-promoted cobalt catalysts for higher oxygenates synthesis. The MOF-mediated synthesis method provide the catalyst with superior resistance to sintering and deactivation. The potassium promoters suppresses the formation of methane and higher hydrocarbons, while cobalt carbide is formed from the metallic cobalt and the carbon in the catalyst. As a result, the potassium-promoted catalyst synthesized by MOF-mediated method gives high yields to ethanol and higher oxygenates. CO hydrogenation was also carried out using real biomass-derived syngas. The low CO composition and high CO/H2 ratio in the biomass-derived syngas require special catalysts to carry out Fischer-Tropsch reaction and produce liquid fuels. By using K-promoted iron catalysts and ruthenium catalysts, along with the addition of steam into the syngas feedstock, a high yield of liquid hydrocarbons were achieved in the reaction. This study shed light on using biomass-derived syngas for the production of higher oxygenates

Structure-activity relationships for the water-gas shift reaction over supported metal catalysts

The Water-Gas Shift (WGS) reaction (CO + H2O → CO2 + H2) is an important chemical process for industrial hydrogen production. The overall goal of this project is to use kinetic experiments and in situ characterization techniques in tandem, in order to derive structure-activity relationships for various catalytic systems. These relationships facilitate the rational catalyst design by identification of catalyst descriptors. In order to establish such relationships, various studies were undertaken, such as (i) effect of transition admetals on the WGS catalysis by molybdenum carbide (ii) effect of residual oxygen content on the performance of molybdenum carbide for WGS (iii) effect of cobalt as a secondary metal promoter over supported Pt catalysts. ^ In the first study, we were interested in the effects of various admetals on the WGS reaction rate and kinetic parameters measured over molybdenum carbide (MO2C). We focused on the determination of active sites over transition metals supported on MO2C. Molybdenum carbide is known to have WGS rate per gram of catalyst that is higher than the commercial Cu/ZnO/Al 2O3 catalyst at 120°C. This rate is promoted further by using the MO2C as a support for admetals such as Pt, Pd, Au, Cu, Ni and Ag. The extent of promotion in the WGS rate normalized by the BET area of the catalyst is shown to correlate with the apparent reaction order with respect to CO. Based on a progressive decrease in the apparent CO order with increasing WGS rate per unit surface area, the CO adsorption strength over the sites created by the admetals is suggested as a potential descriptor for the rate promotion. in situ X-ray absorption experiments show that Au and Pt re-disperse on the MO2C support after a 600°C carburization pretreatment, making MO2C an ideal candidate for the synthesis of thermally robust supported metal catalysts. The difficulties in characterization of Pt/MO2C by electron microscopy were overcome by using Multi-Walled Carbon Nanotubes (MWCNT) as a \u27TEM friendly\u27 support. Pt-Mo alloy nanoparticles in intimate contact with the MO2C are identified as the dominant active sites. ^ In a follow-up study, the dependence of the WGS rates on the residual oxygen content over MO2C and the Pt-modified bulk MO2C was studied with temperature programmed reduction (TPR). Platinum was shown to enhance the oxygen removal from MO2C after various reduction pretreatments. For a passivated (oxygen covered) MO2C catalyst, the WGS rate per unit surface area at 120°C, measured after a 600°C carburization, is 9 times higher compared to the rate measured on the same catalyst after a relatively milder reduction at 300°C. However, for the Pt/MO2C catalyst, this factor of difference in the rates after the pretreatments at aforementioned temperatures was a factor of 1.5. Thus, a Pt/MO2C catalyst with ∼6-7 times higher WGS rate per gram at 120°C compared to the commercial Cu/ZnO/Al2O3 catalyst is reported with a reduction pretreatment that is viable for commercial practice. ^ In the final study, we have attempted to rationalize the promotion in the WGS rate over Pt supported on MWCNT with addition of secondary metal promoter such as cobalt. X-ray absorption and XRD characterization revealed that for a bimetallic catalyst prepared with sequential impregnation of Pt and Co, isolated cobalt phases (CoOx) are formed along with Pt-Co alloy. The turnover rate for WGS at 300°C was promoted by an order of magnitude at the Co:Pt molar ratio of 3:1, in comparison to the monometallic Pt. A selective leaching treatment removed the CoOx phase, without severely affecting the Pt-Co alloy (Pt-Co coordination number changed from 3 to 2.5). The WGS TOR at 300°C decreased 20 times after the CoOx was leached out. The formation of PtCo alloy was concluded to be inconsequential for promotion of the WGS TOR. The interface sites between CoOx and the PtCo alloy particles are suggested to be the active sites for WGS

6 Access Methods and Query Processing Techniques

The performance of a database management system (DBMS) is fundamentally dependent on the access methods and query processing techniques available to the system. Traditionally, relational DBMSs have relied on well-known access methods, such as the ubiquitous B +-tree, hashing with chaining, and, in som

Presentation of an Immunodominant Immediate-Early CD8+ T Cell Epitope Resists Human Cytomegalovirus Immunoevasion.

Control of human cytomegalovirus (HCMV) depends on CD8+ T cell responses that are shaped by an individual's repertoire of MHC molecules. MHC class I presentation is modulated by a set of HCMV-encoded proteins. Here we show that HCMV immunoevasins differentially impair T cell recognition of epitopes from the same viral antigen, immediate-early 1 (IE-1), that are presented by different MHC class I allotypes. In the presence of immunoevasins, HLA-A- and HLA-B-restricted T cell clones were ineffective, but HLA-C*0702-restricted T cell clones recognized and killed infected cells. Resistance of HLA-C*0702 to viral immunoevasins US2 and US11 was mediated by the alpha3 domain and C-terminal region of the HLA heavy chain. In healthy donors, HLA-C*0702-restricted T cells dominated the T cell response to IE-1. The same HLA-C allotype specifically protected infected cells from attack by NK cells that expressed a corresponding HLA-C-specific KIR. Thus, allotype-specific viral immunoevasion allows HCMV to escape control by NK cells and HLA-A- and HLA-B-restricted T cells, while the virus becomes selectively vulnerable to an immunodominant population of HLA-C-restricted T cells. Our work identifies a T cell population that may be of particular efficiency in HCMV-specific immunotherapy

INFLUENCES OF INTERFACES AND PROMOTERS ON THE WATER-GAS SHIFT REACTION OVER SUPPORTED NOBLE METAL CATALYSTS

The water-gas shift reaction (WGS) is an important reaction to produce high purit