A lateral time-of-flight system for charge transport studies

A measurement system for lateral ToF charge carrier transport studies in intrinsic diamond is described. In the lateral ToF geometry, carriers travel close to the sample surface and the system is therefore particularly suited for studies of thin layers as well as the influence of different surface conditions on transport dynamics. A 213 nm pulsed UV laser is used to create electron–hole pairs along a line focus between two parallel metal electrodes on one surface. The use of reflective UV-optics with short focal length allows for a narrow focal line and also for imaging the sample in UV or visible light without any dispersion. A clear hole transit was observed in one homoepitaxial single crystalline diamond film for which the substrate was treated by a Ar/Cl plasma etch prior to deposition. The hole transit signal was sufficiently clear to measure the near-surface hole drift mobility of about 860 cm²/Vs across a contact spacing of 0.3 mm.     

Fe2O3 core-NaCo[Fe(CN)6] shell nanoparticles—Synthesis and characterization

A facile precipitation route was developed for the synthesis of cobalt hexacyanoferrate (CoHCF) as a thin shell around cores of nanoparticles of iron(III) oxide, forming nanoparticles of iron(III) oxide@CoHCF (n-Fe₂O₃@NaCo[Fe(CN)₆]). The morphology and structure of the as-prepared n-Fe₂O₃@NaCo[Fe(CN)₆] were characterized by the techniques of electron microscopies, X-ray diffraction measurements, X-ray photoelectron spectroscopy, infrared spectroscopy and thermogravimetry. Carbon composite electrodes of n-Fe₂O₃@NaCo[Fe(CN)₆] were prepared and the electrochemical behavior of the nanoparticles was evaluated using cyclic voltammetry. The redox couples of n-Fe₂O₃@NaCo[Fe(CN)₆] were investigated and the diffusion coefficients of counter cation in the shell of CoHCF were obtained. The effect of size of particles and the structure of CoHCF was also evaluated. n-Fe₂O₃@NaCo[Fe(CN)₆] represented prominent electrocatalytic activity toward the oxidation of some biologically active compounds.     

Actinides oxalate precipitation in emulsion modeling: From the drop scale to the industrial process

An original process of actinides coprecipitation based on pulsed flow column is studied. The novelty of this process lies in the confinement of the aqueous reagents in separated droplets, dispersed in an inert organic phase (W/O emulsion). Precipitation occurs inside drops when they coalesce. Besides the implementation of well-known technologies of the nuclear industry, this precipitation in emulsion process is particularly convenient for the control of supersaturation, and ensures the sticky precipitates’ confinement within drops, thereby limiting the fouling risk and its adverse consequences on productivity and safety.     

Optimisation of xanthan gum production by palm date (Phoenix dactylifera L.) juice by-products using response surface methodology

The present study was undertaken investigate and optimise the possibility of xanthan gum production by Xanthomonas campestris NRRL B-1459 in batch experiments on date palm juice by-products. Using an experimental Response Surface Methodology complemented with a Central Composite Orthogonal Design, three major independent variables (date juice carbon source, nitrogen source and temperature) were evaluated for their individual and interactive effects on biomass and xanthan gum production. The optimal conditions selected were: 84.68 g/l for carbon source, 2.7 g/l for nitrogen source, and 30.1 °C for temperature. The experimental value obtained for xanthan production under these conditions was about 43.35 g/l, which was close to the 42.96 g/l value predicted by the model. Higher yields of biomass production could be obtained at 46.68 g/l for carbon source, 4.58 g/l for nitrogen source and 30 °C for temperature. The maximum value obtained for biomass production was 3.35 g/l, which was higher than the 2.98 g/l value predicted by the model. The xanthan formed was subjected to HPLC and TLC analyses and its molecular weight as well as pyruvate content were identified. The findings indicated that this polysaccharide contained glucose, glucoronic acid and mannose. Overall, the date palm juice by-products presented in the current study seem to exhibit promising properties that can open new pathways for the production of efficient and cost-effective xanthan gum.     

An Improved Dictionary Cracking Scheme Based on Multiple GPUs for Wi-Fi Network

The Internet has penetrated all aspects of human society and has promoted social progress. Cyber-crimes in many forms are commonplace and are dangerous to society and national security. Cybersecurity has become a major concern for citizens and governments. The Internet functions and software applications play a vital role in cybersecurity research and practice. Most of the cyber-attacks are based on exploits in system or application software. It is of utmost urgency to investigate software security problems. The demand for Wi-Fi applications is proliferating but the security problem is growing, requiring an optimal solution from researchers. To overcome the shortcomings of the wired equivalent privacy (WEP) algorithm, the existing literature proposed security schemes for Wi-Fi protected access (WPA)/WPA2. However, in practical applications, the WPA/WPA2 scheme still has some weaknesses that attackers exploit. To destroy a WPA/WPA2 security, it is necessary to get a PSK pre-shared key in pre-shared key mode, or an MSK master session key in the authentication mode. Brute-force cracking attacks can get a phase-shift keying (PSK) or a minimum shift keying (MSK). In real-world applications, many wireless local area networks (LANs) use the pre-shared key mode. Therefore, brute-force cracking of WPA/WPA2-PSK is important in that context. This article proposes a new mechanism to crack the Wi-Fi password using a graphical processing unit (GPU) and enhances the efficiency through parallel computing of multiple GPU chips. Experimental results show that the proposed algorithm is effective and provides a procedure to enhance the security of Wi-Fi networks.     

Modeling and enforcing invariants of dynamic software architectures

In this paper, we propose an “end-to-end” approach that supports dynamic reconfiguration of software architectures taking advantage of graphical modeling, formal methods and aspect-oriented programming. There are three ingredients of the proposal. The specification end of the solution is covered by a new UML profile enabling to specify the desired architectural style (model), its invariants and the intended reconfiguration operations. In order to verify the consistency of the model and the preservation of the invariants after every reconfiguration, we automatically generate formal specifications in Z notation from the defined model. At the runtime enforcing end of the solution, we propose to encode the enforcement logic as aspect in the AspectJ language. The third important ingredient that makes our approach end-to-end is the automatic translation of formal specifications into aspect-based enforcement code.     

Folksonomy-based personalized search and ranking in social media services

In recent years, social Web users have been overwhelmed by the huge numbers of social media available. Consequentially, users have trouble finding social media suited to their needs. To help such users retrieve useful social media content, we propose a new model of tag-based personalized searches to enhance not only retrieval accuracy but also retrieval coverage. By leveraging social tagging as a preference indicator, we build two models: (i) a latent tag preference model that reflects how a certain user has assigned tags similar to a given tag and (ii) a latent tag annotation model that captures how users have tagged a certain tag to resources similar to a given resource. We then seamlessly map the tags onto items, depending on an individual user's query, to find the most desirable content relevant to the user's needs. Experimental results demonstrate that the proposed method significantly outperforms the state-of-the art algorithms and show our method's feasibility for personalized searches in social media services.