Randomized self-routing algorithms for Clos networks

As the VLSI technology makes large crossbar switches affordable, Clos networks have become a feasible option of large interconnection networks. However, to make these networks practical and useful, efficient routing algorithms need to be developed. This paper will develop and study several randomized routing algorithms for Clos networks. The algorithms are based on the idea that if the first column of Clos is set to some configuration somehow, then the resulting network becomes self-routed using the destination addresses. Each of the randomized algorithms sets the first column to a configuration selected by a random process. The algorithms are then self-routed and take no computation time to set the switches. Probabilistic analysis and simulation measurements of the communication delay of permutation routing are conducted. It is shown that the communication delay of any permutation is 3–6 cycles in networks of up to 1024 processors. Although other routing algorithms route arbitrary permutations in one cycle over Clos/Benes networks and 2 cycles over δ networks, these algorithms take prohibitively large times to compute the appropriate switch settings, while our randomized algorithms are self-routed and spend NO time on computing the switch settings. This makes our algorithms superior to any universal nonrandomized routing algorithm for Clos/Benes networks or δ networks. The speed, universality and ease of implementation of our randomized algorithms make Clos networks highly attractive for large parallel computer systems.     

Guided local search as a network planning algorithm that incorporates uncertain traffic demands

A search based heuristic for the optimisation of communication networks where traffic forecasts are uncertain and the problem is NP-complete is presented. While algorithms such as genetic algorithms (GA) and simulated annealing (SA) are often used for this class of problem, this work applies a combination of newer optimisation techniques specifically: fast local search (FLS) as an improved hill climbing method and guided local search (GLS) to allow escape from local minima. The GLS + FLS combination is compared with an optimised GA and SA approaches. It is found that in terms of implementation, the parameterisation of the GLS + FLS technique is significantly simpler than that for a GA and SA. Also, the self-regularisation feature of the GLS + FLS approach provides a distinctive advantage over the other techniques which require manual parameterisation. To compare numerical performance, the three techniques were tested over a number of network sets varying in size, number of switch circuit demands (network bandwidth demands) and levels of uncertainties on the switch circuit demands. The results show that the GLS + FLS outperforms the GA and SA techniques in terms of both solution quality and optimisation speed but even more importantly GLS + FLS has significantly reduced parameterisation time.     

Fabrication and characterization of a thermal switch

The development of a thermal switch based on arrays of liquid–metal micro-droplets is presented. Prototype thermal switches are assembled from a silicon substrate on which is deposited an array of 1600 30-μm liquid–metal micro-droplets. The liquid–metal micro-droplet array makes and breaks contact with a second bare silicon substrate. A gap between the two silicon substrates is filled with either air at 760 Torr, air at of 0.5 Torr or xenon at 760 Torr. Heat transfer and thermal resistance across the thermal switches are measured for “on” (make contact) and “off” (break contact) conditions using guard-heated calorimetry. The figure of merit for a thermal switch, the ratio of “off” state thermal resistance over “on” state thermal resistance, R_off/R_on, is 129 ± 43 for a xenon-filled thermal switch that opens 100 μm and 60 ± 17 for an 0.5 Torr air-filled thermal switch that opens 25 μm. These thermal resistance ratios are shown to be markedly higher than values of R_off/R_on for a thermal switch based on contact between polished silicon surfaces. Transient temperature measurements for the liquid–metal micro-droplet switches indicate thermal switching times of less than 100 ms. Switch lifetimes are found to exceed one-million cycles.     

Assignment of cells to switches in a cellular mobile network using a hybrid Hopfield network-genetic algorithm approach

Handoff and cabling cost management plays a key role in the design of cellular telecommunications networks. The efficient assignment of cells to switches in this type of networks is an NP-complete problem which cannot be solved efficiently unless P = NP. This paper presents a hybrid Hopfield network-genetic algorithm approach to the cell-to-switches assignment problem, in which a Hopfield network manages the problem's constraints, and a genetic algorithm searches for high quality solutions with the minimum possible cost in terms of handoff and cable displayed. We show, by means of computational experiments, the good performance of our approach to this problem.     

An automated signalized junction controller that learns strategies by temporal difference reinforcement learning

This paper shows how temporal difference learning can be used to build a signalized junction controller that will learn its own strategies through experience. Simulation tests detailed here show that the learned strategies can have high performance. This work builds upon previous work where a neural network based junction controller that can learn strategies from a human expert was developed (Box and Waterson, 2012). In the simulations presented, vehicles are assumed to be broadcasting their position over WiFi giving the junction controller rich information. The vehicle's position data are pre-processed to describe a simplified state. The state-space is classified into regions associated with junction control decisions using a neural network. This classification is the strategy and is parametrized by the weights of the neural network. The weights can be learned either through supervised learning with a human trainer or reinforcement learning by temporal difference (TD). Tests on a model of an isolated T junction show an average delay of 14.12 s and 14.36 s respectively for the human trained and TD trained networks. Tests on a model of a pair of closely spaced junctions show 17.44 s and 20.82 s respectively. Both methods of training produced strategies that were approximately equivalent in their equitable treatment of vehicles, defined here as the variance over the journey time distributions.     

A magnetoelectric energy harvester and management circuit for wireless sensor network

This paper presents an electromagnetic energy harvesting scheme by using a composite magnetoelectric (ME) transducer and a power management circuit. In the transducer, the vibrating wave induced from the magnetostrictive Terfenol-D plate in dynamic magnetic field is converged by using an ultrasonic horn. Consequently more vibrating energy can be converted into electricity by the piezoelectric element. A switching capacitor network for storing electricity is developed. The output of the transducer charges the storage capacitors in parallel until the voltage across the capacitors arrives at the threshold, and then the capacitors are automatically switched to being in series. More capacitors can be employed in the capacitor network to further raise the output voltage in discharging. For the weak magnetic field environment, an active magnetic generator and a magnetic coil antenna under ground are used for producing an ac magnetic field of 0.2–1 Oe at a distance of 25–50 m. In combination with the supply management circuit, the electromagnetic energy harvester with a rather weak power output (about 20 μW) under an ac magnetic field of 1 Oe can supply power for wireless sensor nodes with power consumption of 75 mW at a duration of 620 ms.     

Efficient multicast schemes for 3-D Networks-on-Chip

3-D Networks-on-Chip (NoCs) have been proposed as a potent solution to address both the interconnection and design complexity problems facing future System-on-Chip (SoC) designs. In this paper, two topology-aware multicast routing algorithms, Multicasting XYZ (MXYZ) and Alternative XYZ (AL + XYZ) algorithms in supporting of 3-D NoC are proposed. In essence, MXYZ is a simple dimension order multicast routing algorithm that targets 3-D NoC systems built upon regular topologies. To support multicast routing in irregular regions, AL + XYZ can be applied, where an alternative output channel is sought to forward/replicate the packets whenever the output channel determined by MXYZ is not available. To evaluate the performance of MXYZ and AL + XYZ, extensive experiments have been conducted by comparing MXYZ and AL + XYZ against a path-based multicast routing algorithm and an irregular region oriented multiple unicast routing algorithm, respectively. The experimental results confirm that the proposed MXYZ and AL + XYZ schemes, respectively, have lower latency and power consumption than the other two routing algorithms, meriting the two proposed algorithms to be more suitable for supporting multicasting in 3-D NoC systems. In addition, the hardware implementation cost of AL + XYZ is shown to be quite modest.     

A relation context oriented approach to identify strong ties in social networks

Strong ties play a crucial role in transmitting sensitive information in social networks, especially in the criminal justice domain. However, large social networks containing many entities and relations may also contain a large amount of noisy data. Thus, identifying strong ties accurately and efficiently within such a network poses a major challenge. This paper presents a novel approach to address the noise problem. We transform the original social network graph into a relation context-oriented edge-dual graph by adding new nodes to the original graph based on abstracting the relation contexts from the original edges (relations). Then we compute the local k-connectivity between two given nodes. This produces a measure of the robustness of the relations. To evaluate the correctness and the efficiency of this measure, we conducted an implementation of a system which integrated a total of 450 GB of data from several different data sources. The discovered social network contains 4,906,460 nodes (individuals) and 211,403,212 edges. Our experiments are based on 700 co-offenders involved in robbery crimes. The experimental results show that most strong ties are formed with k ? 2.     

A new discrete circuit for readout of resistive sensor arrays

In this paper, we present a method that simplifies the interconnect complexity of N × M resistive sensor arrays from N × M to N + M. In this method, we propose to use two sets of interconnection lines in row–column fashion with all the sensor elements having one of their ends connected to a row line and other end to a column line. This interconnection overloading results in crosstalk among all the elements. This crosstalk causes the spreading of information over the whole array. The proposed circuit in this method takes care of this effect by minimizing the crosstalk. The circuit makes use of the concept of virtual same potential at the inputs of an operational amplifier in negative feedback to obtain a sufficient isolation among various elements. We theoretically present the suitability of the method for small/moderate sized sensor arrays and experimentally verify the predicted behavior by lock-in-amplifier based measurements on a light dependent resistor (LDR) in a 4 × 4 resistor array. Finally, we present a successful implementation of this method on a 16 × 16 imaging array of LDR.     

Some Applications of Magma in Designs and Codes: Oval Designs,Hermitian Unitals and Generalized Reed–Muller Codes

We describe three applications of Magma to problems in the area of designs and the associated codes:  •  Steiner systems, Hadamard designs and symmetric designs arising from an oval in an even-order plane, leading in the classical case to bent functions and difference-set designs;  •  the Hermitian unital as a 2-(q³ +  1, q +  1, 1) design, and the code overF_p where p divides q +  1;  •  a basis of minimum-weight vectors for the code over F_pof the design of points and hyperplanes of the affine geometry AG_d(F_p), where p is a prime.     

Analyzing MPI performance over 10-Gigabit ethernet

Recent work with 10-Gigabit (10 GbE) network adapters has demonstrated good performance in TCP/IP-based local- and wide-area networks (LANs and WANs). In the present work we present an evaluation of host-based 10 GbE adapters in a system-area network (SAN) in support of a cluster. This evaluation focuses on the performance of the message-passing interface (MPI) when running over a 10 GbE interconnect. We find that MPI over 10 GbE provides communications performance comparable to that of TCP alone and fairly competitive with more exotic technologies such as MPI over Quadrics. The optimization of MPI and MPI-based applications to make use of this performance, however, is a non-trivial task. Consequently, it is difficult for MPI-based applications to realize this performance when running current-generation 10 GbE hardware.     

A two-dimensional optical cross-connect with integrated waveguides and surface micromachined crossbar switches

The design, fabrication and test results of an all-optical cross-connect, which uses electrostatically actuated micromechanical digital mirrors to steer optical signals in a network of planar waveguides, are presented. The substrate consists of a network of spliced planar waveguides on silica substrates. The switches, located at the waveguide intersections, are formed with an electroplated T-structure consisting of a horizontal perforated square plate suspended by four elastic beams. When operated, the horizontal plate is pulled up making the mirror move out of the optical path thus steering the beam. An 8×8 switch array has been fabricated and tested. Actuation and relaxation switching times near 3 ms have been demonstrated with an actuation voltage of 120 V. The optical insertion loss for the array typically varied from 2.3 dB for a single trench in the optical path (shortest optical path) to 8 dB for 15 trenches in the optical path (longest optical path).     

Realization strategies of dedicated path protection: A bandwidth cost perspective

Communication networks have to provide a high level of availability and instantaneous recovery after failures in order to ensure sufficient survivability for mission-critical services. Currently, dedicated path protection (or 1 + 1) is implemented in backbone networks to provide the necessary resilience and instantaneous recovery against single link failures with remarkable simplicity. However, in order to satisfy strict availability requirements, connections also have to be resilient against Shared Risk Link Group (SRLG) failures. In addition, switching matrix reconfigurations have to be avoided after a failure in order to guarantee instantaneous recovery. For this purpose, there are several possible realization strategies improving the characteristics of traditional 1 + 1 path protection by lowering reserved bandwidth while conserving all its favorable properties. These methods either utilize diversity coding, network coding, or generalize the disjoint-path constraint of 1 + 1.In this paper, we consider the cost aspect of the traditional and the alternative 1 + 1 realization strategies. We evaluate the bandwidth cost of different schemes both analytically and empirically in realistic network topologies. As the more complex realizations lead to NP-complete problems even in the single link failure case, we propose both Integer Linear Programming (ILP) based optimal methods, as well as heuristic and meta-heuristic approaches to solve them. Our findings provide a tool and guidelines for service providers for selecting the path protection method with the lowest bandwidth cost for their network corresponding to a given level of reliability.     

Efficient HMAC-based secure communication for VANETs

Vehicular Ad Hoc Network (VANET) is an emerging type of network which facilitates vehicles on roads to communicate for driving safety. It requires a mechanism to help authenticate messages, identify valid vehicles, and remove malevolent vehicles which do not obey the rules. Most existing solutions either do not have an effective message verification scheme, or use the public key infrastructure (PKI). In this network, vehicles are able to broadcast messages to other vehicles and a group of known vehicles can also communicate securely among themselves. So group communication is necessary for the network. However, most existing solutions either do not consider this or use pairing operation to realize this. They are either not secure or not effective. In this paper, we provide a more comprehensive set of secure schemes with Hash-based Message Authentication Code (HMAC) in VANETs to overcome their shortcomings. Of course, we still need to use Pairing operation in some place. Our scheme is composed of three schemes: (1) Communications between Vehicles and Road-Side Units (RSUs), (2) One to One Communications within a Group, (3) One to One Communications without a Group. Based on our simulation study, we show that our schemes are effective and the delay caused is much lower. The average delay caused by our first scheme is nearly thousands of times lower than prior schemes. The average delay caused by our second scheme is 0.312 ms, while the delay caused by prior scheme is 12.3 ms. Meanwhile the average delay caused by our third scheme is 0.312 ms, and the delay caused by prior scheme is about 9 s.     

Posting,commenting, and tagging: Effects of sharing news stories on Facebook

Social networking sites such as Facebook provide new ways of sharing news stories that allow users to act as opinion leaders in their networks, encourage discussion, and potentially increase their involvement in current events. This study identifies the particular features of Facebook that facilitate the discussion of news and tests their effects on involvement and feelings of influence. Participants (N = 265) in a 3 (Broadcast level: news feed vs. wall post vs. direct message) × 3 (Elaboration: opinion vs. question vs. no comment) × 2 (Involving-friends: tag vs. no tag) between-subjects factorial experiment were randomly assigned to share a story from a news website on Facebook. Results show that user involvement in the news content depends on the social affordances of the site, particularly those that allow for audience customization and those that drive network feedback. Asking the network’s opinions and targeting specific friends led to greater involvement in the news content. Discussion through comments led to a greater sense of influence and greater involvement for those sharing the news story. These findings highlight the importance of encouraging individuals to act as sources of information in their networks to drive engagement in current events in the changing news landscape.     

耐故障Clos网及其路由算法

提出了一种新的耐故障Clos网,通过在基础Clos网各段中增加冗余的交换单元,使其能够在发生少量故障的情况下正常工作,从而提供更可靠的服务。针对耐故障Clos网,给出一种耐故障Clos路由算法,该算法采用最小分布优先的策略逐列计算Clos网连接说明矩阵,通过重排完全实现无阻塞路由,该算法的时间复杂度在最坏情况下仅为O(N3/2)。该耐故障Clos网及其算法设计可以用于实现更为可靠的Clos网络。     

Passive single chip wireless microwave pressure sensor

A novel micromachined passive wireless pressure sensor is presented. The device consists of a tuned circuit operating at 10 GHz fabricated on to a SiO₂ membrane, supported on a silicon wafer. A pressure difference across the membrane causes it to deflect so that an antenna circuit detunes. The circuit is remotely interrogated to read off the sensor data wirelessly. The chip area is 5 mm × 4 mm and the membrane area is 2 mm² with a thickness of 4 μm. Two on-chip passive resonant circuits were investigated: a meandered dipole and a zigzag antenna. Both have a physical length of 4.25 mm. The sensors show a shift in their resonant frequency in response to changing pressure of 10.28–10.27 GHz for the meandered dipole, and 9.61–9.58 GHz for the zigzag antenna. The sensitivities of the meandered dipole and zigzag sensors are 12.5 kHz/mbar and 16 kHz/mbar respectively.     

Designing layout–timing independent quantum-dot cellular automata (QCA) circuits by global asynchrony

The concept of clocking for QCA, referred to as the four-phase clocking, is widely used. However, inherited characteristics of QCA, such as the way to hold state, the way to synchronize data flows, and the way to power QCA cells, make the design of QCA circuits quite different from VLSI and introduce a variety of new design challenges and the most severe challenges are due to the fact that the overall timing of a QCA circuit is mainly dependent upon its layout. This fact is commonly referred to as the “layout = timing” problem. To circumvent the problem, a novel self-timed QCA circuit design methodology referred to as the Globally Asynchronous, Locally Synchronous (GALS) Design for QCA is proposed in this paper. The proposed technique can significantly reduce the layout–timing dependency from the global network of QCA devices in a circuit; therefore, considerably flexible QCA circuit design and floorplanning will be possible.     

GPU-based parallel vertex substitution algorithm for the p-median problem

We introduce a GPU-based parallel vertex substitution (pVS) algorithm for the p-median problem using the CUDA architecture by NVIDIA. pVS is developed based on the best profit search algorithm, an implementation of vertex substitution (VS), that is shown to produce reliable solutions for p-median problems. In our approach, each candidate solution in the entire search space is allocated to a separate thread, rather than dividing the search space into parallel subsets. This strategy maximizes the usage of GPU parallel architecture and results in a significant speedup and robust solution quality. Computationally, pVS reduces the worst case complexity from sequential VS’s O(p · n²) to O(p · (n ? p)) on each thread by parallelizing computational tasks on GPU implementation. We tested the performance of pVS on two sets of numerous test cases (including 40 network instances from OR-lib) and compared the results against a CPU-based sequential VS implementation. Our results show that pVS achieved a speed gain ranging from 10 to 57 times over the traditional VS in all test network instances.     

Effect of single crystalline MgO powder treatment of phosphor surface on discharge property of high-Xe AC plasma display panels

This paper presents a method of surface treatment of phosphor using a single crystalline MgO powder, and investigates effect of the surface treatment on discharge property of a plasma display panel (PDP). The discharge gas of the PDP was a 88% Ne–12% Xe gas mixture at a pressure of 400 Torr. For the surface treatment, a single crystalline MgO powder was mixed in methanol, sprayed on the phosphor surface, and annealed at 400 °C. This treatment suppressed glow discharge, which was observed very often in the weak discharges for reset of PDP if the phosphor works as a cathode, and provided a favorable condition for the PDP reset operation. When an experimental PDP fabricated using the surface treatment was driven by the twin reset waveform, the measured time delay for 99.9% cumulative probability of address discharge was 830 ns, which meets the timing requirement for addressing a Full HD (1920 × 1080 resolution) PDP with the 10 sub-field single scan method.