In this letter, a new scatternet formation algorithm called hybrid mesh tree for Bluetooth ad hoc networks was proposed. The hybrid mesh tree constructs a mesh-shaped topology in one dense area that is extended by tree-shaped topology to the other areas. First, the hybrid mesh tree uses a designated root to construct a tree-shaped subnet, and then propagates a constant k in its downstream direction to determine new roots. Each new root then asks its upstream master to start a return connection procedure to convert the first tree-shaped subnet into a mesh-shaped subnet. At the same time, each new root repeats the same procedure as the designated root to build its own tree-shaped subnet until the whole scatternet is formed. Simulation results showed that the hybrid mesh tree achieved better network performance than Bluetree and generated an efficient scatternet configuration for various sizes of Bluetooth scatternets.

Future high density magnetic recording requires a nanometer spaced head-slider interface, high track seeking velocity and high spindle speed. Such a combination greatly increases the likelihood of slider-disk and slider-particle-disk impact. Furthermore, the impact can generate high flash temperature and leads to data reliability problems, such as partial or full data erasure. This work report a method to conduct controlled experimental investigations into the possibility of such a data erasure even when the temperature is far below the Curie temperature. Results indicate that the high density magnetic transitions are of high likelihood of being affected by the flash temperature. Investigations also extended to micromagnetic modeling of the flash temperature effect. Results suggest that thermally induced local stress can play important roll in the data erasure process. Modeling results also exhibit that smaller grain size and higher recording density are also of higher likelihood of getting the transitions being affected by the flash temperature.

In this letter, we present a novel single-precision floating-point multiply-accumulator (FNA-MAC) to achieve lower hardware resource, reduced computing latency and improved computing accuracy for continuous dot product operations. By further fusing the normalization and alignment in the traditional FMA algorithm, the proposed architecture eliminates the first N-1 normalization and rounding operations for an N-point dot product, and preserves the precision of interim results in a significant bit size that is twice of that in the traditional methods. The normalization and rounding of the final result is processed at the cost of consuming an additional multiply-add operation. The simulation results show that the improvement in computational accuracy is significant. Meanwhile, when comparing to a recently published FMA design, the proposed FNA-MAC can reduce the slice look-up table/flip-flop resource and computing latency by a fact of 18%, 33.3%, respectively.

The increasing complexity of embedded applications and the prevalence of multiprocessor system-on-chip (MPSoC) introduce a great challenge for designers on how to achieve performance and programmability simultaneously in embedded systems. Automatic multithreaded code generation methods taking account of performance optimization techniques can be an effective solution. In this paper, we consider the issue of increasing processor utilization and reducing communication cost during multithreaded code generation from Simulink models to improve system performance. We propose a combination of three-layered multithreaded software with Integer Linear Programming (ILP) based design-time mapping and scheduling policies to get optimal performance. The hierarchical software with a thread layer increases processor usage, while the mapping and scheduling policies formulate a group of integer linear programming formulations to minimize communication cost as well as to maximize performance. Experimental results demonstrate the advantages of the proposed techniques on performance improvements.

In this letter, a decentralized scatternet formation algorithm called Bluelayer is proposed. First, Bluelayer uses a designated root to construct a tree-shaped subnet and propagates an integer variable k1 called counter limit as well as a constant k in its downstream direction to determine new roots. Then each new root asks its upstream master to start a return connection procedure to convert the tree-shaped subnet into a web-shaped subnet for its immediate upstream root. At the same time, each new root repeats the same procedure as the root to build its own subnet until the whole scatternet is formed. Simulation results show that Bluelayer achieves good network scalability and generates an efficient scatternet configuration for various sizes of Bluetooth ad hoc network.

The interaction between slider, lubricant and disk surface is becoming the most crucial robustness concern of advanced data storage systems. This paper reports comparative studies among various techniques for the measurement of head-disk spacing. It is noticed that the triple harmonic method gives a reading much closer to the reading of the head-disk spacing obtained optically at on-track center case, comparing with the PW50 method. Specially prepared disks with different carbon overcoat thickness (6.5 nm, 11 nm, 16 nm and 22 nm) were also used to study the reliability and repeatability of the triple harmonic method.

In this paper, we present Blueweb, a new Bluetooth-based multihop network with an efficient scatternet formation algorithm and a hybrid routing protocol. The Blueweb is designed from the original idea of Bluetree. Blueweb's scatternet formation uses two mechanisms. One is the role exchange mechanism in which only slave nodes serve as the role of relay through the whole scatternet. The other one is the return connection mechanism in which we convert the scatternet from a tree-shaped to a web-shaped topology. Meanwhile, a modified source routing protocol is designed for Blueweb in which we combine the proactive method with the reactive method to discover the optimal path for packet transmission. Furthermore, using computer simulations we compared the system performance of Blueweb and Bluetree with both a static model and a uniform traffic model. With the static model we evaluate the scatternet performance and with the uniform traffic model we evaluate the transmission performance. Our simulation results show that Blueweb achieves superior system performance than Bluetree on both scatternet performance and transmission performance.

A semi-distributed resource allocation scheme based on multihop equilibrium is proposed for OFDM-relay networks. This method aims to reduce the amount of feedback information from the relay nodes (RNs). Moreover, it utilizes radio resource by striking an efficient balance between the capacities of the BS-RN link and RN-MS link. Simulation results show that the proposed semi-distributed scheme achieves good performances in terms of throughputs and fraction of satisfied users.

An atomistic model for annealing simulation is presented. To well simulate both BED (Boron Enhanced Diffusion) and TED (Transient Enhanced Diffusion), the surface emission model, which describes the emission of point defects from surface during annealing, is implemented. The simulation is carried out for RTA annealing (1000 or 1050) after B implantation. The implantation energy varies from 0.5 keV to 13 keV. Agreements between simulation and SIMS data are achieved. Both BED and TED phenomena are characterized. The Enhancement of diffusion is discussed. The surface emission model is studied by simulation. The results shows that the surface emission has little effect on annealing of B 10 keV implantation while obvious effect on annealing of B 0.5 keV implantation. It indicates that the surface emission is much more necessary to simulate BED than TED.

An aggregate signature scheme,which is an extension of ordinary signature, allows anyone to compress n signatures of n messages from n signers into a single short signature for reducing the size multiple individual signatures. Recently, Liu et al. proposed an efficient certificateless aggregate signature scheme with shorter public key size, constant AS size and with constant pairing computations. Although they proved that the scheme has existential unforgeability against adaptive chosen messages attacks. However, in this paper, two concrete attacks are proposed to show that Liu et al.'s scheme actually does not reach the security as they claimed.

Blueweb is a self-organizing Bluetooth-based multihop network equipped with a scatternet formation algorithm and a modified source routing protocol. In this paper, we first review the basic Blueweb network. Then we focus on a heuristic automatic configuration algorithm which can be used to partition a large-scale Blueweb network. This algorithm contains three main functional blocks including route master selection, node assignment, and subnet number decision. The route master selection block selects new route masters at a low computation cost. The node assignment block assigns nodes to each newly configured subnet in order to minimize the average route query cost. The subnet number decision block determines the optimal number of subnet which achieves the largest system performance improvement ratio at minimum operation cost. With these three functional blocks, optimal network configuration for Blueweb routing protocol can be determined. Computer simulations show that a configured Blueweb achieves higher network capacity than an unconfigured Blueweb.