Choice Of Topology Research Articles

DTDOR: An Efficient Routing Algorithm for Torus Networks

Many different factors, such as topology, routing technique, selection function, flow control policy, complexity of router design, contribute to the performance of networks on chip (NoCs). Among these factors, the choice of topology and routing function has a significant effect on the average packet latency and saturation behavior. Torus is popular in many application domains, while the problem of virtual channel misbalance caused by its deadlock avoidance scheme brings lots of performance pathologies. In this paper, we present a novel deadlock avoidance scheme based on draining scheme, and propose a deadlock-free routing scheme for torus networks. We quantify the effects of the proposed routing scheme on the overall network performance by presenting simulation results for 1-D torus and 2-D torus NoCs. Experimental results show that the novel routing algorithm for torus networks could make more efficient use of virtual channel resources, and hence cutting down packet latency and boosting throughput. Note although this paper has considered 1-D and 2-D torus networks in the experimental evaluation, the new scheme is flexible enough to support highradix torus networks.

Analysis and Optimization of Cascode Structure in Power Amplifier for X-Band Phase Array Radar Application

A 7.7---12 GHz fully monolithic transformer-coupled cascode power amplifier (PA) was designed for X-band phase array radar application. This PA was fabricated in a 0.25-$$\upmu $$μm SiGe BiCMOS technology with chip size of $$2\times 2$$2×2 mm$$^{2}$$2. The best choice of the cascode topology for PA design is discussed and the possible stability issue of this configuration is analyzed. The distributed capacitor structure which is connected to the base of cascode transistor is proposed to reduce the base series inductance and hence, improve circuit stability and boost gain. Moreover, circuit/layout co-design for above structure is completed through full 3D simulation. The PA features a three-stage cascode architecture that includes both medium-speed (medium breakdown voltage) and high breakdown voltage (low-speed) SiGe transistors, and a 1:2 input splitter and a 4:1 output combiner which are designed for a low insertion loss and compact dimensions on-chip. The proposed PA achieves a measured small signal gain of 26.6---29.6 dB from 7.7 to 12 GHz with a 5.0 V DC supply. A 28 dBm maximum output power with an 18.5 % power-added efficiency at 10 GHz have also been achieved.

Synthesis on power electronics for large fuel cells: From power conditioning to potentiodynamic analysis technique

The work addressed in this paper deals with a synthesis on power electronic converters used for fuel cells. The knowledge gap concerns conceptually different electronic converter architectures for PEM (Proton Exchange Membrane) fuel cells able to perform three types of functionalities: The first one is the capacity of emulating an active load representative of electrical drive constraints. In that case, frequency and fuel cell current ripple can be set independently to investigate the dynamic behavior of the fuel cell. The second one is power conditioning applied to large high power and segmented fuel cell systems (“Large” represents several tens of cells and multi-kilowatt stacks), which is a non trivial consideration regarding the topological choices to be made for improving efficiency, compactness and ensure operation under faulty condition. A multi-port resonant isolated boost topology is analyzed enabling soft switching over a large operating range for a thirty kilowatt segmented fuel cell. A splitting current control strategy in case of a segment is under fault is proposed. Each considered converter topologies meet specific constraints regarding fuel cell stack design and power level. The third functionality is the ability for the power electronics to perform analysis and diagnosis techniques, like the cyclic voltammetry on large PEM fuel cell assemblies. The latter technique is an uncommon process for large fuel cell stacks since it is rather performed on small electrochemical cells or little assemblies. Moreover potentiodynamic analysis requires the control of the fuel cell voltage according to particular voltage cycles leading to fuel cell current nonlinearities, which is rather unusual, since the fuel cell current is almost always regulated.

Theoretical and Numerical Design of a Wireless Power Transmission Link With GaN-Based Transmitter and Adaptive Receiver

In this paper, we describe a rigorous theoretical approach to the circuit-level nonlinear design of an entire inductive resonant wireless power transfer (IR-WPT) system, including the transmitter and receiver nonlinear subsystems. Starting from a novel analytical characterization of the inductive resonant link, the system efficiency is parametrically computed as a function of a set of circuital parameters, including the power levels to be transferred. These quantities are then used as design goals inside the nonlinear optimization of the transmitter and receiver blocks. By adopting the last generation miniaturized enhanced-mode AlGaN/GaN-power field-effect transistor and fast Schottky diodes, a Class-D amplifier and a full-bridge rectifier followed by a switching dc-dc Buck converter that acts as load impedance transformer are designed in a single optimization process at 6.78 MHz. Thus, the transmitter and the receiver are directly connected by the IR two-port network, and the system is capable to adapt to variable distances between the resonators of the IR-WPT link. The choice of the Class-D topology for the transmitter and the adaptability of the active receiver enable to get rid of inter-stage matching networks, which can severely reduce the overall efficiency, especially in high power transfer environments. With the proposed IR-WPT system, up to 44 W of transferred power and a peak of 73% dc-to-dc efficiency were obtained with an input dc voltage VDC=30 V at a link distance D=5 cm. Numerical and experimental results are discussed, demonstrating the accuracy of the proposed design procedure.

Simultaneously High Stiffness and Damping in Nanoengineered Microtruss Composites

Materials combining high stiffness and mechanical energy dissipation are needed in automotive, aviation, construction, and other technologies where structural elements are exposed to dynamic loads. In this paper we demonstrate that a judicious combination of carbon nanotube engineered trusses held in a dissipative polymer can lead to a composite material that simultaneously exhibits both high stiffness and damping. Indeed, the combination of stiffness and damping that is reported is quite high in any single monolithic material. Carbon nanotube (CNT) microstructures grown in a novel 3D truss topology form the backbone of these nanocomposites. The CNT trusses are coated by ceramics and by a nanostructured polymer film assembled using the layer-by-layer technique. The crevices of the trusses are then filled with soft polyurethane. Each constituent of the composite is accurately modeled, and these models are used to guide the manufacturing process, in particular the choice of the backbone topology and the optimization of the mechanical properties of the constituent materials. The resulting composite exhibits much higher stiffness (80 times) and similar damping (specific damping capacity of 0.8) compared to the polymer. Our work is a step forward in implementing the concept of materials by design across multiple length scales.

Automated design space exploration for FPGA-based heterogeneous interconnects

The choice of the on-chip communication topology in many systems is of vital importance because it affects the entire inter-component data traffic and impacts significantly the overall system performance and cost. On the other hand, there is today a very large spectrum of on-chip interconnect topologies that potentially meet given communication requirements, determining various trade-offs between cost and performance. This work proposes an automated methodology to search the interconnect design space, avoiding a manual and time consuming try-and-error process. The methodology turns the description of the application communication requirements into an on-chip synthesizable interconnection structure satisfying given area constraints. Targeted at FPGA technologies, the approach combines crossbars and shared buses, connected through bridges, yielding a scalable, efficient structure. The resulting architecture improves the level of communication parallelism that can be exploited, while keeping area requirements low. The paper thoroughly describes the formalisms and the methodology used to derive such optimized heterogeneous topologies. It also discusses some case-studies emphasizing the impact of the proposed approach and highlighting the essential differences with a few other solutions presented in the technical literature.

Characterization of 6.5 kV IGBTs for High-Power Medium-Frequency Soft-Switched Applications

Medium voltage high-power applications are usually realized using high voltage semiconductors (3.3 kV and above) operated in the hard switching mode with low switching frequencies (several hundreds of hertz). However, for high-power dc-dc converters employing a transformer for galvanic isolation, it is attractive to increase the switching frequency so that the transformer size can be reduced. An increase of the switching frequency implies an increase of the switching losses, and this has to be mitigated somehow, usually by choice of resonant topologies or soft switching techniques. Main focus of the paper is on the operation of the insulated gate bipolar transistor (IGBT) within a high-power dc-dc LLC resonant converter, in order to explore interactions between semiconductor and circuit properties, which both must be simultaneously considered in order to achieve the best utilization of a high voltage power semiconductor operating at higher switching frequencies. For these purposes, switching properties of a standard 6.5 kV IGBT are compared with switching properties of two different optimized versions of a 6.5 kV IGBT. Experimental results are included to support theoretical considerations and findings.

ABS-NET: Fully Decentralized Runtime Adaptation for Distributed Objects

We present a formalized, fully decentralized runtime semantics for a core subset of ABS, a language and framework for modelling distributed object-oriented systems. The semantics incorporates an abstract graph representation of a network infrastructure, with network endpoints represented as graph nodes, and links as arcs with buffers, corresponding to OSI layer 2 interconnects. The key problem we wish to address is how to allocate computational tasks to nodes so that certain performance objectives are met. To this end, we use the semantics as a foundation for performing network-adaptive task execution via object migration between nodes. Adaptability is analyzed in terms of three Quality of Service objectives: node load, arc load and message latency. We have implemented the key parts of our semantics in a simulator and evaluated how well objectives are achieved for some application-relevant choices of network topology, migration procedure and ABS program. The evaluation suggests that it is feasible in a decentralized setting to continually meet both the objective of a node-balanced task allocation and make headway towards minimizing communication, and thus arc load and message latency.

Swarm intelligence and the quest to solve a garbage and recycling collection problem

This work focuses on the application of Swarm Intelligence to a problem of garbage and recycling collection using a swarm of robots. Computational algorithms inspired by nature, such as Particle Swarm Optimization (PSO) and Ant Colony Optimization, have been successfully applied to a range of optimization problems. Our idea is to train a number of robots to interact with each other, attempting to simulate the way a collective of animals behave, as a single cognitive entity. What we have achieved is a swarm of robots that interacts like a swarm of insects, cooperating with each other accurately and efficiently. We describe two different PSO topologies implemented, showing the obtained results, a comparative evaluation, and an explanation of the rationale behind the choices of topologies that enhanced the PSO algorithm. Moreover, we describe and implement an Ant Colony Optimization (ACO) approach that presents an unusual grid implementation of a robot physical simulation. Hence, generating new concepts and discussions regarding the necessary modifications for the algorithm towards an improved performance. The ACO is then compared to the PSO results in order to choose the best algorithm to solve the proposed problem.

Locality for quantum systems on graphs depends on the number field

Adapting a definition of Aaronson and Ambainis (2005 Theory Comput. 1 47–79), we call a quantum dynamics on a digraph saturated Z-local if the nonzero transition amplitudes specifying the unitary evolution are in exact correspondence with the directed edges (including loops) of the digraph. This idea appears recurrently in a variety of contexts including angular momentum, quantum chaos, and combinatorial matrix theory. Complete characterization of the digraph properties that allow such a process to exist is a long-standing open question that can also be formulated in terms of minimum rank problems. We prove that saturated Z-local dynamics involving complex amplitudes occur on a proper superset of the digraphs that allow restriction to the real numbers or, even further, the rationals. Consequently, among these fields, complex numbers guarantee the largest possible choice of topologies supporting a discrete quantum evolution. A similar construction separates complex numbers from the skew field of quaternions. The result proposes a concrete ground for distinguishing between complex and quaternionic quantum mechanics.

From singularity theory to finiteness of Walrasian equilibria

The main result of this paper states that there exists a residual subset of the set of critical economies whose associated equilibria are finite in number. We also show that this subset does not contain any open set and therefore the result is the best possible for our choice of topology (compact-open topology). The proof rests on results and concepts from singularity theory.

Narrowband Microwave Filters With Mixed Topology

Narrowband microwave filters exhibiting transmission zeros in the response (either imaginary and/or complex) can be typically designed with cross-coupled or extracted pole topologies. These configurations have advantages and disadvantages that must be carefully considered during the choice of a specific topology. In some cases, however, it may be convenient to choose a mixed topology, i.e., part of the structure with an extracted-pole and part with a cross-coupled configuration. Unfortunately, even if several well-established techniques are available in the literature for the cross-coupled or extracted-pole synthesis taken separately, nothing can be found for the design of mixed topology filters (apart direct optimization). In this study, two solutions for the synthesis of a low-pass prototype with a mixed topology are presented, which noticeably increases the design flexibility of narrowband microwave filters. Several examples are presented for illustrating the proposed techniques for the synthesis of mixed-topology prototype filters. A test filter, synthesized with the second method introduced and fabricated in coaxial technology, has given an experimental validation of the proposed technique.

On a topological choice principle by Murray Bell

In ZF set theory, we investigate the deductive strength of Murray Bellʼs principle (C):For every set{Ai:i∈I}of non-empty sets, there exists a set{Ti:i∈I}such that for everyi∈I,Tiis a compactT2topology onAi, with regard to various choice forms.Among other results, we prove the following:(1)The Axiom of Multiple Choice (MC) does not imply statement (C) in ZFA set theory.(2)If κ is an infinite well-ordered cardinal number, then (C) + “Every filter base on κ can be extended to an ultrafilter” implies “For every family A={Ai:i∈κ} such that for all i∈κ, |Ai|⩾2, there is a function (called a Kinna–Wagner function) f with domain A such that for all A∈A, ∅≠f(A)⊊A” and “For every natural number n⩾2, every family A={Ai:i∈κ} of non-empty sets each of which has at most n elements has a choice function”.(3)If κ is an infinite well-ordered cardinal number, then (C) + “There exists a free ultrafilter on κ” implies “For every family A={Ai:i∈κ} such that for all i∈κ, |Ai|⩾2, there is an infinite subset B⊆A with a Kinna–Wagner function” and “For every natural number n⩾2, every family A={Ai:i∈κ} of non-empty sets each of which has at most n elements has an infinite subfamily with a choice function”.(4)(C) + “Every compact T2 space is effectively normal” implies MC restricted to families of non-empty sets each expressible as a countable union of finite sets, and “For every family A={Ai:i∈ω} such that for all i∈ω, 2⩽|Ai|<ℵ0, there is an infinite subset B⊆A with a Kinna–Wagner function”.(5)(C) + “For every set X, every countable filter base on X can be extended to an ultrafilter on X” implies ACℵ0, i.e., the axiom of choice for countable families of non-empty sets.(6)(C) restricted to countable families of non-empty sets + “For every set X, every countable filter base on X can be extended to an ultrafilter on X” is equivalent to ACℵ0 + “There exists a free ultrafilter on ω”.(7)(C) restricted to countable families of non-empty sets + “For every set X, every countable filter base on X can be extended to an ultrafilter on X” implies the statements: “The Tychonoff product of a countable family of compact spaces is compact” and “For every infinite set X, the (generalized) Cantor cube 2X is countably compact”.(8)(C) restricted to countable families of non-empty sets does not imply “There exists a free ultrafilter on ω” in ZF.(9)(C) + “The axiom of choice for countable families of non-empty sets of reals” implies “There exists a non-Lebesgue-measurable set of reals”.(10)The conjunction of the Countable Union Theorem (the union of a countable family of countable sets is countable) and “Every infinite set is Dedekind-infinite” does not imply (C) restricted to countable families of non-empty sets, in ZFA set theory.

The fundamental group as a topological group

This paper is devoted to the study of a natural group topology on the fundamental group which remembers local properties of spaces forgotten by covering space theory and weak homotopy type. It is known that viewing the fundamental group as the quotient of the loop space often fails to result in a topological group; we use free topological groups to construct a topology which promotes the fundamental group of any space to topological group structure. The resulting invariant, denoted π1τ, takes values in the category of topological groups, can distinguish spaces with isomorphic fundamental groups, and agrees with the quotient fundamental group precisely when the quotient topology yields a topological group. Most importantly, this choice of topology allows us to naturally realize free topological groups and pushouts of topological groups as fundamental groups via topological analogues of classical results in algebraic topology.

Algorithm of a choice of optimum topology of a computer network for the automated control system of air traffic

Algorithm of a choice of optimum topology of a computer network for the automated control system of air traffic

Reliability oriented design of power supplies for high energy physics applications

The paper describes the design of switching converters suitable for power supply application in the LHC proton accelerator, in operation since 2010 at the European Organization for Nuclear Research (CERN) in Geneva (Switzerland). Experiments running at LHC must reliably operate in a harsh environment, due to radiation, high magnetic fields, and stringent thermal constraints. The followed approach takes into account the very tight reliability requirements during all the design stages, from the choice of circuit topologies and radiation hard power components, to the thermal layout and material optimization. Results carried out on prototypes are reported.

Topology Optimization for Hybrid Electric Vehicles With Automated Transmissions

Currently, many different topologies are designed with different transmission technologies such as automated manual transmission (AMT) and continuously variable transmission (CVT). The choice of topology determines the energy-flow efficiency between the hybrid system, the engine, and the vehicle wheels. The optimal topology minimizing fuel consumption is influenced by the transmission technology. Therefore, an AMT (high efficiency) and a push-belt CVT (moderate efficiency), are used in this research for comparison. In addition, a controlled switching topology is introduced as a benchmark, where controlled coupling with additional clutches of the electric machine before or after the transmission minimizing transmission losses and improving hybrid performance is investigated. The results showed that a switching topology can significantly improve CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emission reduction (average relative improvements between 2% and 7%), particularly for CVT-based hybrid vehicles. Moreover, in case of an AMT, a precoupled topology is preferable, and in the case of a CVT, a postcoupled is preferable for full-hybrid vehicles. For these cases, selecting the optimal fixed topology can improve the relative CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emission reduction between 2% and 8%.

Compact X-band SiGe power amplifier for single-chip phased array radar applications

An X-band power amplifier (PA) is presented for single-chip phased array radar applications. In this work, the choice of optimum circuit topology for X-band PA design is discussed and possible stability issues for high and low frequencies are analysed. The PA features a two-stage cascode architecture that includes both high-speed (low breakdown) and high breakdown (low-speed) SiGe transistors. It consists of two stages providing a 23.2 dBm saturated output power with a 28% power-added efficiency at 9 GHz. The output 1-dB compression point (P1dB) is higher than 20 dBm in a 3 GHz bandwidth and has a maximum value of 22.2 dBm. The small-signal gain is 25.5 dB with a 3-dB bandwidth of 3.2 GHz (7.3–10.5 GHz). The PA has been fabricated using 0.25 µm SiGe BiCMOS process provided by IHP Microelectronics. The PA occupies 1 mm×0.6 mm chip area and consumes 120 mA from a 4 V supply voltage. These results demonstrate comparable or better performance than other reported PAs and suitable performance for single-chip phased array applications.

A DYNAMIC JITTER-CONTROLLED TREE-BASED P2P NETWORK TOPOLOGY FOR MULTIPOINT MULTIMEDIA APPLICATIONS

In the last few years peer-to-peer (P2P) systems have gained ground for multipoint video content distribution over IP networks. P2P technologies give new opportunities to define an efficient multimedia streaming application, but at the same time they involve a set of technical challenges and issues due to the best-effort service offered by the underlying Internet, and its dynamic and heterogeneous nature. Stringent requirements in terms of end-to-end delay for real-time applications motivates the choice of a tree-structured topology against other topologies that have been introduced in the last research works, but mainly aimed at non-real-time services like video on demand and live streaming. The target of this paper is to present a platform for multipoint multimedia transmission based on a tree overlay network with jitter control and to show through experiments on real environment that our platform performs better than a traditional tree overlay network system in terms of PSNR, frame loss and playout frozen time.

Understanding hydrogen sorption in a polar metal-organic framework with constricted channels

A high fidelity molecular model is developed for a metal-organic framework (MOF) with narrow (approximately 7.3 Å) nearly square channels. MOF potential models, both with and neglecting explicit polarization, are constructed. Atomic partial point charges for simulation are derived from both fragment-based and fully periodic electronic structure calculations. The molecular models are designed to accurately predict and retrodict material gas sorption properties while assessing the role of induction for molecular packing in highly restricted spaces. Thus, the MOF is assayed via grand canonical Monte Carlo (GCMC) for its potential in hydrogen storage. The confining channels are found to typically accommodate between two to three hydrogen molecules in close proximity to the MOF framework at or near saturation pressures. Further, the net attractive potential energy interactions are dominated by van der Waals interactions in the highly polar MOF - induction changes the structure of the sorbed hydrogen but not the MOF storage capacity. Thus, narrow channels, while providing reasonably promising isosteric heat values, are not the best choice of topology for gas sorption applications from both a molecular and gravimetric perspective.