Analysis and Evaluation on NBTI-Induced Circuit Aging

Aging effects degrade circuit performance with time, inducing reliability problem. Accurate prediction of circuit aging can help designer determine the reasonable design margin, avoiding the over-design of the circuit. Based on the physical understanding of aging mechanism, an analysis framework is proposed to predict NBTI-induced circuit aging. The analysis framework starts at the worst case prediction, which assumes the extremely operational conditions. Then, the impacts of different workloads and logic topology of the circuit on the aging-induced degradation are incorporated into the analysis framework to make the predicted result be closer to the practical scenario. Experimental results demonstrate that the effectiveness of the proposed analysis framework.

Localized and Energy-Efficient Topology Control in Wireless Sensor Networks Using Fuzzy-Logic Control Approaches

The sensor nodes in the Wireless Sensor Networks (WSNs) are prone to failures due to many reasons, for example, running out of battery or harsh environment deployment; therefore, the WSNs are expected to be able to maintain network connectivity and tolerate certain amount of node failures. By applying fuzzy-logic approach to control the network topology, this paper aims at improving the network connectivity and fault-tolerant capability in response to node failures, while taking into account that the control approach has to be localized and energy efficient. Two fuzzy controllers are proposed in this paper: one is Learning-based Fuzzy-logic Topology Control (LFTC), of which the fuzzy controller is learnt from a training data set; another one is Rules-based Fuzzy-logic Topology Control (RFTC), of which the fuzzy controller is obtained through designing if-then rules and membership functions. Both LFTC and RFTC do not rely on location information, and they are localized. Comparing them with other three representative algorithms (LTRT, List-based, and NONE) through extensive simulations, our two proposed fuzzy controllers have been proved to be very energy efficient to achieve desired node degree and improve the network connectivity when sensor nodes run out of battery or are subject to random attacks.

A Self-Adaptive Model of Two-Level for Dynamic Peer-to-Peer Networks

The present thesis puts forward a hierarchical P2P model: self-adaptive P2P model of two-level. Super peers compose a self-adaptive DHT network on the top layer, and lower ordinary peers take super peer in the same group as their center server to form a cluster. Data are stored in ordinary peers and super peers hold indices of data and answer for request from ordinary peers. When super peer join or leave, it does not maintain consistency of entire network’s logic topology but only update routing table of its predecessor and successor, besides, super peers update their routing table cache when they transmit messages. The ordinary peers keep backup of super peer for system restore when super peer fails. System can optimize network structure by select peers with high capacity to be super peer and restrict amount of peers in each group.

O-minimal spectra, infinitesimal subgroups and cohomology

By recent work on some conjectures of Pillay, each definably compact group G in a saturated o-minimal expansion of an ordered field has a normal “infinitesimal subgroup” G00 such that the quotient G/G00, equipped with the “logic topology”, is a compact (real) Lie group. Our first result is that the functor G ↦ G/G00 sends exact sequences of definably compact groups into exact sequences of Lie groups. We then study the connections between the Lie group G/G00 and the o-minimal spectrum of G. We prove that G/G00 is a topological quotient of . We thus obtain a natural homomorphism Ψ* from the cohomology of G/G00 to the (Čech-)cohomology of . We show that if G00 satisfies a suitable contractibility conjecture then is acyclic in Čech cohomology and Ψ is an isomorphism. Finally we prove the conjecture in some special cases.

TYPE-DEFINABILITY, COMPACT LIE GROUPS, AND o-MINIMALITY

We study type-definable subgroups of small index in definable groups, and the structure on the quotient, in first order structures. We raise some conjectures in the case where the ambient structure is o-minimal. The gist is that in this o-minimal case, any definable group G should have a smallest type-definable subgroup of bounded index, and that the quotient, when equipped with the logic topology, should be a compact Lie group of the "right" dimension. I give positive answers to the conjectures in the special cases when G is 1-dimensional, and when G is definably simple.