Cost Performance Analysis in Multi-level Tree Networks

Changes in core network size in Japan: Comparisons between the 1990s and 2010s

This article examines changes over time in social network composition among a sample of people aged 85 and over at baseline interview in 1987, who were followed-up two and a half to three years later. Almost half of respondents at follow-up had smaller networks than in 1987, with 19% having fewer relatives in their networks, 30% having fewer friends, and 26% also having fewer confidants. However, for most (84%) there was no change in whether they could name a main helper. Network density (integration) had declined for 30%, a substantial minority. For the remainder there were either increases or no changes. Most of those who needed help with tasks of daily living were given help, and while much of the help was given by relatives, by 1990 professionals were also providing a major part of the help. There were no associations with network change and health or functional ability, or with use of services. Those whose network size had increased were more likely to report at follow-up interview (in 1990) a need for (more) help. Multivariate analysis confirmed that while the greater part of the change in network size was accounted for by changes in numbers of relatives, it was closely followed as an explanatory variable by changes in numbers of friends, indicating that both variables (relatives and friends) account almost equally for changes in network size over time among very elderly people. The research presented here reports a considerable amount of change in network size and structure.

Individual and social network correlates of responding to multiple overdoses among a cohort of people who use drugs

The integration of multiple resources conservation networks is necessary to attain the ever-stringent sustainable goals. This work takes initiatives to develop a heat integrated water network via a proposed P-graph-based sequential methodology. In the first step, a set of feasible water regeneration networks is generated using the conventional P-graph framework. Then, the obtained feasible networks will be used as the inputs in the second stage which aims to generate various sets of feasible heat exchanger networks. It is worth noting that the second model is solved by an extended P-graph framework (P-HENS) for combinatorial process network optimization. The solutions are then ranked based on the total network cost. To demonstrate the effectiveness of the proposed method, a typical water regeneration network (three sources and three sinks) with multi-contaminants is used. The results show a total of 103 feasible water network structures (water network cost ranging from 0.76 M$/y to 1.18 M$/y). Thereafter, a list of feasible HIWRN can be determined using P-HENS. The top four HIWRNs which offer similar total network cost (~1.639 M$/y) are demonstrated. This proposed method provides valuable insights that allow decision-makers to further select the optimal solution which may be more beneficial as compared to the one obtained via conventional methods.

Organic-waste-derived butyric acid-to-biodiesel supply-chain network: Strategic planning design using a deterministic snapshot model

We propose a comprehensive scalable algorithm simultaneously assessing the routing, scheduling and virtualization in Time-Domain Wavelength Interleaved Network (TWIN). TWIN is an energy-efficient optical burst switching technology for metropolitan area and data center intra- and interconnections, with destinations using separate allocated sets of wavelengths for the reception. Given the costs of the optical transponders and the wavelength use per km of fiber length, the proposed algorithm solves the routing and wavelength assignment problem, and in the same time allocates the time slots to traffic flows (performs the slot scheduling), so that the total network cost is minimized. The algorithm also enables the construction of overlayed virtual networking domains at minimum cost, which share the transponders and network links, and can employ different scheduling policies. The performance of the algorithm is compared with the pre-existing optimal dimensioning solution for single virtualization domain based on Integer Linear Programing, for different scenarios. The obtained results show that the network cost is within 27% of the optimal.

Existing methods for handling routing and dimensioning in dynamic WDM networks solve the two problems separately. The main drawback of this approach is that a global minimum cost solution cannot be guaranteed. Given that wavelengths are costly resources, determining the minimum network cost is of fundamental importance. We propose an approach which jointly solves the routing and dimensioning problems in optical burst switching (OBS) networks, guaranteeing a target blocking per connection. The method finds the set of routes and the number of wavelengths per network link that minimise the total network cost. To accomplish this, an integer linear programming problem is solved. The proposed method was applied to ring networks, where the optimal solution achieves a reduction in the network cost of 10–40% (for traffic loads <0.4, compared to solving both problems separately). In the case of mesh topologies, to reduce the computational complexity of the method, we applied a variation of it which achieves a local minimum. Even so, a reduction of 5–20% (for traffic loads <0.4) in the network cost was obtained. This ability to lower network cost could make the proposed method the best choice to date for dynamic network operators.

Capital and total cost targets for mass exchange networks: Part 1: Simple capital cost models

Virtual network functions (VNFs) are placed across the network to complete the required network performance of virtual network slice (vNS), and the placement of VNFs is flexible and problematic. Besides, a VNF can be decomposed into multiple sub-functions, and the same type of sub-function can be re-used by multiple VNFs. Therefore, the resources of subfunctions in different vNS requests can be shared and the cost of the substrate network is reduced. So, function decomposition makes the VNF placement problem more flexible and challenging. In this paper, we study the VNF placement problem with function decomposition for vNS, and formulate it as an integer linear programming (ILP) aiming to minimize the total cost of the substrate network. Then, an approach named Placement algorithm based on Function Decomposition (P-FD) is proposed to get a near-optimal solution of this problem. Finally, simulation results show that P-FD can achieve less total cost compared with algorithms in existing.

Multi-objective optimization of a hydrogen supply chain network: Wind and solid biomass as primary energy sources for the public transport in Sicily

This paper studies an online cost optimization problem for distributed storage and access. The goal is to dynamically create and delete copies of data objects over time at geo-distributed servers to serve access requests and minimize the total storage and network cost. We revisit a recent algorithm in the literature and show that it does not have a competitive ratio of 2 as claimed by constructing a counterexample. We further prove that no deterministic online algorithm can achieve a competitive ratio bounded by 2 for the general cost optimization problem. We develop an online algorithm and prove that it achieves a competitive ratio of max {2, min {γ, 3}}, where γ is the max/min storage cost ratio among all servers. Examples are given to confirm the tightness of competitive analysis.

A multiobjective hub-airport location problem for an airline network design

Despite various planning efforts, airspace capacity can sometimes be exceeded, typically because of disruptive events. Air traffic flow management (ATFM) is the process of managing flights in this situation. In this paper, we present an ATFM model that accounts for different rerouting options (path rerouting and diversion) and preexisting en route flights. The model proposes having a central authority to control all decisions, which is then compared with current practice. We also consider interflight and interairline fairness measures in the network. We use an exact approach to solve small- to medium-sized instances, and we propose a modified fix-and-relax heuristic to solve large-sized instances. Allowing a central authority to control all decisions increases network efficiency compared with the case where the ATFM authority and airlines control decisions independently. Our experiments show that including different rerouting options in ATFM can help reduce delays by up to 8% and cancellations by up to 23%. Moreover, ground delay cost has much more impact on network decisions than air delay cost, and network decisions are insensitive to changes in diversion cost. Furthermore, the analysis of the tradeoff between total network cost and overtaking cost shows that adding costs for overtaking can significantly improve fairness at only a small increase in total system cost. A balanced total cost per flight among airlines can be achieved at a small increase in the network cost (0.2%–3.0%) when imposing airline fairness. In conclusion, the comprehensiveness of the model makes it useful for analyzing a wide range of alternatives for efficient ATFM.

This paper deals with the minimization of the total system cost in the PCS network using CDMA cellular system standard. The total system cost includes the installation costs of base stations (BS), base station controllers (BSC) and PCS exchanges (PCX), the weighted-distance connection costs between BS and BSC and between BSC and PCX and the hard handoff cost. Our objective is to keep each of these costs at a minimum with guaranteed service performance. However, there exists a tradeoff property between these costs. Therefore, we use an efficient and effective searching technique, hierarchical genetic algorithms (HGA), which has the ability to handle multiobjective functions and various constraints and find multiple different solutions for decision making.

Robust multimodal hub network design for hazmat considering a detour strategy