Privacy preserving broadcast message authentication protocol for VANETs

Vehicular Ad-hoc Networks (VANETs) will start becoming deployed within the next decade. Among other benefits, it is expected that VANETs will support applications and services targeting the increase of safety on the road, and assist in improving the efficiency of the road transportation network. However, several serious challenges remain to be solved before efficient and secure VANET technology becomes available, one of them been efficient authentication of messages in a VANET. There is a significant body of research work addressing this issue, however, while progress has been made, the challenge is still far from having been resolved and reliable and secure systems ready for deployment becoming available. In this paper, we propose the Privacy Preserving Broadcast Message Authentication (PPBMA) scheme, which, instead of performing asymmetric verification, uses Message Authentication Code (MAC) functionality and HASH operations to authenticate messages. Moreover, we use two-level key hash chain, which assists avoiding message losses. Simulation results demonstrate that PPBMA has superior performances in terms of packet loss rate and message delivery latency when compared to existing solutions. Due to this advantage, it can support emergency and routine messages alike, while existing solutions can only support routine messages.     

Information Loss of the Mahalanobis Distance in High Dimensions: Application to Feature Selection

When an infinite training set is used, the Mahalanobis distance between a pattern measurement vector of dimensionality D and the center of the class it belongs to is distributed as a chi^2 with D degrees of freedom. However, the distribution of Mahalanobis distance becomes either Fisher or Beta depending on whether cross validation or resubstitution is used for parameter estimation in finite training sets. The total variation between chi^2 and Fisher, as well as between chi^2 and Beta, allows us to measure the information loss in high dimensions. The information loss is exploited then to set a lower limit for the correct classification rate achieved by the Bayes classifier that is used in subset feature selection.     

Defect-induced amorphization of crystalline silicon as a mechanism of disordered-region formation during ion implantation

An atomic-scale simulation study is presented which demonstrates that siliconamorphization during ion implantation can be caused by defect-induced collapseof the crystalline lattice. The amorphization threshold is calculated in termsof critical defect concentrations required to induce the amorphizationtransition at room temperature. These concentrations are found to be about28%, 20%, and 25% of self-interstitials, vacancies, or Frenkel pairs,respectively. These high defect densities are consistent with experimentalmeasurements in silicon self-implanted with high-energy ions. The structureof the defect-induced amorphous phases is similar to that of the bulkamorphous phase produced by rapid quenching of liquid silicon.     

Continuum and atomistic modeling of electromechanically-induced failure of ductile metallic thin films

A multiscale modeling approach is presented for the analysis of electromechanically-induced void morphological evolution and failure in ductile metallic thin films, which are used for device interconnections in integrated circuits. Self-consistent mesoscopic simulations of surface morphological evolution are combined with atomistic calculations of surface properties and molecular-dynamics (MD) simulations of plastic deformation mechanisms in the vicinity of void surfaces. Results are presented that demonstrate a coupled mode of surface instability that leads to formation of electromigration-induced slit-like features and stress-induced crack-like features on void surfaces. In addition, MD results are presented for the dislocation-mediated mechanism and the kinetics of void growth in ductile metallic systems subject to hydrostatic and biaxial tensile strains. The incorporation of MD-derived constitutive information for plastic deformation into the mesoscopic analysis and simulation framework also is discussed.     

Clinical Evaluation of Extracellular ADMA Concentrations in Human Blood and Adipose Tissue

Circulating asymmetrical dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthesis, has been proposed as a biomarker for clinical outcome. Dimethylarginine dimethylaminohydrolase (DDAH) is the main enzyme responsible for ADMA metabolism and elimination. Adipose tissue ADMA concentrations and DDAH activity and their role in diabetes and obesity have not yet been investigated. In this study, we evaluated clinical microdialysis in combination with a sensitive analytical method (GC-MS/MS) to measure ADMA concentrations in extracellular fluid. Adipose tissue ADMA concentrations were assessed before and during an oral glucose tolerance test in lean healthy subjects and subjects with diabetes (n = 4 each), and in morbidly obese subjects before and after weight loss of 30 kg (n = 7). DDAH activity was determined in subcutaneous and visceral adipose tissue obtained during laparoscopic surgery (n = 5 paired samples). Mean interstitial ADMA concentrations did not differ between study populations (healthy 0.17 ± 0.03 μM; diabetic 0.21 ± 0.03 μM; morbidly obese 0.16 ± 0.01 and 0.17 ± 0.01 μM before and after weight loss, respectively). We did not observe any response of interstitial ADMA concentrations to the oral glucose challenge. Adipose tissue DDAH activity was negligible compared to liver tissue. Thus, adipose tissue ADMA plays a minor role in NO-dependent regulation of adipose tissue blood flow and metabolism.     

A nomogram method for estimating the energy produced by wind turbine generators

A simple nomogram is constructed to estimate the power generated by a wind turbine generator (WTG) operated at near maximum efficiency using optimum tip-speed ratio between cut-in and rated wind speed, and at constant power using optimum pitch control between rated and cut-out wind speed. The nomogram is based on information that is readily available for commercial WTGs as well as some simple statistical quantities for the wind at the site. When the wind speed is described by a Weibull distribution, the power of a WTG is estimated in terms of three generalized non-dimensional parameters. When a Rayleigh distribution is employed only two parameters are necessary. A second nomogram is also developed for those less common cases where a small correction of the results of the first nomogram is needed. A mathematical analysis is presented which allows for the construction of single chart nomograms without sacrificing the necessary accuracy. Two application examples demonstrate the degree of accuracy achieved by the nomograms and the advantages they offer for parametric analyses as regards convenience and labor.     

Solar and geothermal heating and cooling of the European Centre for Public Law building in Greece

The European Centre for Public Law in Legraina near Athens in Greece is heated and cooled by a combined solar and geothermal system. The main components of the system are a saline groundwater supplying well, water storage tank for 6 h autonomy, inverter for regulating geothermal flow, heat exchanger, two electrical water source heat pumps placed in cascade, fan coils, air handling units, as well as solar air collectors for air preheating in winter. In addition, hot water is supplied to the building hostel by solar water heaters. Monitoring of the energy system during heating showed excellent energy efficiency and performance.