Specific Network Design Research Articles

A hybrid intersection control strategy for CAVs under fluctuating traffic demands: A value approximation approach

Confronted with growing and fluctuating traffic demands, urban transportation system has been encountering mounting challenges in traffic congestion, especially at intersections. With enhanced traffic control precision enabled by the emerging Connected and Automated Vehicle (CAV) technologies, this study proposes a hybrid control strategy for connected and automated traffic at urban intersections, which enables the integration of diverse control schemes to harness their strengths and mitigate their weaknesses. With rolling horizon strategy, a nonlinear optimization model is developed to determine the optimal traffic control plans considering both current status and forthcoming vehicle arrivals. Vehicle delays are elaborately characterized without relying on any empirical assumptions. The original model is converted to a Mixed Integer Programming with Quadratic Constraints (MIP-QC) by employing appropriate linearization techniques, which could be solved by commercial solvers. For the acquisition of instant and reliable solutions, a multilayer feedforward network-based approximate algorithm is developed, referred as Value Approximation Control (VAC) algorithm. Theoretical derivation is provided to validate the capability of VAC algorithm in the precise approximations of the value function in the traffic plan optimization problem, and ultimately enabling to acquire global optimal solutions via specific network design and training techniques. Numerical experiments on both artificial and researcher-collected datasets demonstrate that our proposed VAC algorithm achieves performance nearly equivalent to the mathematical model. Significantly, it outperforms current state-of-art traffic control methods in terms of both intersection throughput and average vehicle delay. Moreover, sensitivity analysis reveals the robustness of the VAC algorithm against inaccuracy in vehicle arrival information, and the stable performance even in the presence of significant disturbances.

A Triple-Double Convolutional Neural Network for Panchromatic Sharpening.

Pansharpening refers to the fusion of a panchromatic (PAN) image with a high spatial resolution and a multispectral (MS) image with a low spatial resolution, aiming to obtain a high spatial resolution MS (HRMS) image. In this article, we propose a novel deep neural network architecture with level-domain-based loss function for pansharpening by taking into account the following double-type structures, i.e., double-level, double-branch, and double-direction, called as triple-double network (TDNet). By using the structure of TDNet, the spatial details of the PAN image can be fully exploited and utilized to progressively inject into the low spatial resolution MS (LRMS) image, thus yielding the high spatial resolution output. The specific network design is motivated by the physical formula of the traditional multi-resolution analysis (MRA) methods. Hence, an effective MRA fusion module is also integrated into the TDNet. Besides, we adopt a few ResNet blocks and some multi-scale convolution kernels to deepen and widen the network to effectively enhance the feature extraction and the robustness of the proposed TDNet. Extensive experiments on reduced- and full-resolution datasets acquired by WorldView-3, QuickBird, and GaoFen-2 sensors demonstrate the superiority of the proposed TDNet compared with some recent state-of-the-art pansharpening approaches. An ablation study has also corroborated the effectiveness of the proposed approach. The code is available at https://github.com/liangjiandeng/TDNet.

Optimal Pattern Retargeting in IEEE 1687 Networks: A SAT-based Upper-Bound Computation

A growing number of embedded instruments is being integrated into System-on-Chips for testing, monitoring, and several other purposes. To standardize their access protocols, the IEEE 1687 (IJTAG) standard has defined a flexible network infrastructure. Finding the shortest path in such networks requires a comprehensive search over a solution space, bounded by a limited number of time frames. This bound must be selected carefully, as it can neither be too large (to avoid unnecessary long execution time) nor too small (to avoid missing the optimal solution). Previous work was not efficiently applicable to all segments of IJTAG networks, with some providing unrealistic bounds and others having scope limitations or scalability issues. In this work, we present a new methodology for computing the upper-bound on the number of time frames using the Boolean Satisfiability Problem (SAT). Our proposed technique can also be customized to perfectly adapt to instruments access procedures, which in turn increases efficiency by reducing the time spent searching for required configurations. Results show the effectiveness of our work in computing the upper-bound for irregular benchmarks that are not constrained by a specific network design. This is achieved with a controlled increase in execution time, in contrast to previous work.

Heresy or Breakthrough: Fibre Optic Cleaning Without Inspection and Call for an "Open Architecture" Fibre Optic Precision Cleaning Procedure

A new inspection device defines the three-dimensional nature of connector surface areas and potential debris in unseen and previously uncharacterized surfaces. Inspection and cleaning procedures emerged in 2006. There are limitations within these that are resolved with color digital photography of the three-dimensional surfaces rather than the limited two-dimensional perspectives of IEC 61300-3-35. The result is an update of cleaning processes that (only) consider 15-20% of a two-dimensional diameter of the area commonly termed an horizontal ‘end face’. Advanced inspection reveals not only the remaining ‘horizontal end face’, but also introduces and adds vertical surfaces to the ‘end face’ that result in a logical, obvious, and heretofore disregarded three-dimensional structure. (Figure 1) As well, the advanced inspection device reveals connector adapters which are commonly understood to be a source of cross-contamination of one connection to the other. Until this time, there has been no practical means to view connection adapters and alignment sleeve components. (Figure 2) All of these various surfaces may have debris that currently area not considered and are soil points that may induce cross-contamination. These surfaces, as to present an accurate definition of the connector, require redefinition from two dimensions to three. The results of this logical advance bring enhanced cleaning procedures, new tools, and more reliable transmissions for all fiber optic deployments. This means than instead of multiple recleaning, first time cleaning is more possible and successful deployments more probable. When existing standards were first written in 2006, there was less need for precision cleaning and inspection of these surfaces. As fibre optic capacities and transmission speeds have increased, awareness of the three-dimensional nature of connector surfaces leads network designers, installers, and researchers to adopt a higher standard of inspection and precision cleaning to meet the ever-advancing sciences of fibre optic transmission of all types. Each is equally mission critical and one open architecture cleaning procedure follows the crafts person and contractor and is written into specific network designs. In so doing, the network design itself becomes a training tool for subsequent deployments. A new inspection device defines the three-dimensional nature of connector areas and potential debris in unseen and previously uncharacterized surfaces. With IEC 61300-3-35, inspection and cleaning procedures emerged. There are limitations. One procedure is possible: adaptable to all cleaning products in a vendor neutral way.

Regularization by Architecture: A Deep Prior Approach for Inverse Problems

The present paper studies so-called deep image prior (DIP) techniques in the context of ill-posed inverse problems. DIP networks have been recently introduced for applications in image processing; also first experimental results for applying DIP to inverse problems have been reported. This paper aims at discussing different interpretations of DIP and to obtain analytic results for specific network designs and linear operators. The main contribution is to introduce the idea of viewing these approaches as the optimization of Tikhonov functionals rather than optimizing networks. Besides theoretical results, we present numerical verifications.

Integrated Tradespace Analysis of Space Network Architectures

Methods to design space communication networks at the link level are well understood and abound in the literature. Nevertheless, models that analyze the performance and cost of the entire network are scarce, and they typically rely on computationally expensive simulations that can only be applied to specific network designs. This paper presents an architectural model to quantitatively optimize space communication networks given future customer demands, communication technology, and contract modalities to deploy the network. The model is implemented and validated against NASA’s Tracking and Data Relay Satellite System. It is then used to evaluate new architectures for the fourth-generation Tracking and Data Relay Satellite System given the capabilities of new optical and Ka-band technologies, as well as the possibility to deploy network assets as hosted payloads. Results indicate that optical technology can provide a significant improvement in the network capabilities and lifecycle cost, especially when placing these terminals on board commercial satellites as hosted payloads. The cost savings and benefit improvements of such an architecture are discussed and quantified.

Exploring the Design Space of Self-Regulating Power-Aware On/Off Interconnection Networks

With power consumption becoming increasingly critical in interconnected systems, power-aware networks become part-and-parcel of many single-chip and multichip systems. As communication links consume significant power regardless of utilization, a mechanism to realize such power-aware networks is on/off links-network links that can be turned on/off as a function of traffic. In this paper, we investigate and propose self-regulating power-aware interconnection networks that turn their links on/off in response to bursts and dips in traffic in a distributed fashion. We explore the design space of such on/off networks, outlining a 5-step design methodology along with various building block solutions at each step that can be effectively assembled to develop various on/off network designs. We applied our methodology to the design of two classes of on/off networks with links that possess substantially different on/off delays, an on-chip network as well as a chip-to-chip network, and show that our designs are able to adapt dynamically to variations in network traffic. Three specific network designs are then constructed, presented, and evaluated. Our simulations show that link power consumption can be reduced by up to 54.4 percent, with a modest increase in network latency

Seeking Consensus on Designing Marine Protected Areas: Keeping the Fishing Community Engaged

A community group was formed to consider establishing marine reserves within the Channel Islands National Marine Sanctuary in southern California. Membership included representatives from resource agencies, environmental organizations, commercial and recreational fishing interests, and the general public. While the group agreed on several areas for fishing closures, members could not reach consensus on a specific network design. Several factors interfered with the group's effort in attaining agreement resulting in the endeavor subsequently being replaced by a "top-down" approach that lacks the support of the fishing community. Lessons learned from the project emphasize the need by marine protected area participants to recognize irreconcilable impasses early in the process and to seek solutions to maneuver around them. The importance of keeping the fishing community fully engaged is discussed.

Optimizing and controlling the operation of heat‐exchanger networks

AbstractA procedure was developed for on‐line optimization and control systems of heat‐exchanger networks, which features a two‐level control structure, one for a constant configuration control system and the other for a supervisor on‐line optimizer. The coordination between levels is achieved by adjusting the formulation of the optimization problem to meet requirements of the adopted control system. The general goal is always to work without losing stream temperature targets while keeping the highest energy integration. The operation constraints used for heat‐exchanger and utility units emphasize the computation of heat‐exchanger duties rather than intermediate stream temperatures. This simplifies the modeling task and provides clear links with the limits of the manipulated variables. The optimal condition is determined using LP or NLP, depending on the final problem formulation. Degrees of freedom for optimization and equation constraints for considering simple and multiple bypasses are rigorously discussed. An example used shows how the optimization problem can be adjusted to a specific network design, its expected operating space, and the control configuration. Dynamic simulations also show benefits and limitations of this procedure.

Using tabu search to solve the Steiner tree-star problem in telecommunications network design

We present a study of using tabu search to solve a specific network design problem arising in the telecommunication industry. We develop a tabu search heuristic for this problem that incorporates long-term memory and probabilistic move selections. Computational results show that the new heuristic consistently outperforms the best local search currently available, with significantly increased performance differences on more difficult problems.

Planning for pedestrian networks in North American downtowns

AbstractWhile North American urban regions are served by mechanical modes of transportation, downtowns are largely pedestrian environments. The growth and consolidation of office districts over the last twenty years have revived interest in developing coherent and efficient pedestrian networks, which can be coordinated with other transportation needs within the downtown. Ambitious plans for expansion of the downtown for offices, the retail and service industries as well as for housing and entertainment have been adopted in many North American cities during the 1980s. The successful integration of these large central areas depends to a considerable extent on the implementation of expanded pedestrian networks. This paper discusses certain spatial characteristics of North American cities which call for specific network designs and research into the walking environments of central areas. More knowledge is needed of the relative contributions to pedestrian regeneration of land use combinations, the design of networks and of walking paths.

A New Measure for Charcterizing Data Traffic

It is generally recognized that data traffic has more diverse characteristics and transmission requirements than voice traffic. In particular, data traffic associated with many interactive data processing applications is often characterized to be extremely bursty, which lends support to the choice of Packet (or message) switching over circuit switching in data network design. We introduce in this paper a new measure called bursty factor for characterizing the burstiness of a data traffic source. Unlike the usual measures of peak-to-average ratio and duty cycle, the new measure introduced is independent of a specific network design and dependent only upon the traffic source characteristics and performance requirements. It can therefore be used to guide the direction of an initial network design.