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Anonymous credential systems allow users to obtain a credential on multiple attributes from an organization and then present it to verifiers in a way that no information beyond what attributes are required to be shown is revealed. Moreover, multiple uses of the credential cannot be linked. Thus they represent an attractive tool to realize fine-grained privacy-friendly authentication and access control. In order to avoid a single point of trust and failure, decentralized AC systems have been proposed. They eliminate the need for a trusted credential issuer, e.g., by relying on a set of credential issuers that issue credentials in a threshold manner (e.g., $t$t out of $n$nf). In this article, we present a novel AC system with such a threshold issuance that additionally provides credential delegation. It represents the first decentralized and delegatable AC system. We provide a rigorous formal framework for such threshold delegatable anonymous credentials ($\mathsf {TDAC}$TDAC’s). Our concrete approach departs from previous delegatable ACs and is inspired by the concept of functional credentials. More precisely, we propose a threshold delegatable subset predicate encryption ($\mathsf {TDSPE}$TDSPE) scheme and use $\mathsf {TDSPE}$TDSPE to construct a $\mathsf {TDAC}$TDAC scheme and present a comparison with previous work and performance benchmarks based on a prototype implementation.

In this work, the combination of vibration loading and thermal cycle effects on the fatigue properties of a solder joint in a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) discrete was investigated. The fatigue mechanism under each loading mode was individually analyzed, and then according to the incremental damage superposition approach, the simultaneous effects were thoroughly studied. Under thermal cycling, the creep behavior of the solder is linked to the fatigue life. In fact, the creep accumulated strain in each thermal cycle has a straight relation to the failure time of solder joint. The origin of stress/strain in the assembly is owing to the sharp difference between coefficients of thermal expansions of the components in the electronic package. Regarding the vibration loading, the root mean square of peeling stress as a widely acceptable failure indicator was used to evaluate the vibration effects on the fatigue life. It is determined that the maximum stress is concentrated at the corner of solder layer. This result was similar to the outcomes of thermal cycling. The results also indicated that the combination of thermal and mechanical loadings accelerates the failure of the solder joint of the power MOSFET. Furthermore, the experimental and simulation studies showed similar results and approved the crack initiation at the corner of solder layer.

We analyze a class of signal-to-interference-and-noise-ratio (SINR) random graphs. These random graphs arise in the modeling packet transmissions in wireless networks. In contrast to previous studies on SINR graphs, we consider both a space and a time dimension. The spatial aspect originates from the random locations of the network nodes in the Euclidean plane. The time aspect stems from the random transmission policy followed by each network node and from the time variations of the wireless channel characteristics. The combination of these random space and time aspects leads to fluctuations of the SINR experienced by the wireless channels, which in turn determine the progression of packets in space and time in such a network. In this paper we study optimal paths in such wireless networks in terms of first passage percolation on this random graph. We establish both ‘positive’ and ‘negative’ results on the associated time constant. The latter determines the asymptotics of the minimum delay required by a packet to progress from a source node to a destination node when the Euclidean distance between the two tends to 8. The main negative result states that this time constant is infinite on the random graph associated with a Poisson point process under natural assumptions on the wireless channels. The main positive result states that, when adding a periodic node infrastructure of arbitrarily small intensity to the Poisson point process, the time constant is positive and finite.

The present research deals with the natural frequencies and mode shapes of cylindrical pressure vessels filled with different gasses in various internal pressures. The Hamilton’s principle is employed to derive the governing equations, which are solved using analytical and finite element analyses, and a closed form relation as the equivalent density is obtained to include the gas properties. The experimental modal analysis is performed and the obtained results are compared and validated with analytical and finite element results. The results show that the type of the gas, as well as the gas pressure have significant effect on vibrational behavior of the structure and should be accounted in the design and analysis of vessels.