On the complexity of the upgrading version of the Maximal Covering Location Problem

In this article, we study the complexity of the upgrading version of the maximal covering location problem with edge length modifications on networks. This problem is NP-hard on general networks. However, in some particular cases, we prove that this problem is solvable in polynomial time. The cases of star and path networks combined with different assumptions for the model parameters are analysed. In particular, we obtain that the problem on star networks is solvable in (Formula presented.) time for uniform weights and NP-hard for non-uniform weights. On paths, the single facility problem is solvable in (Formula presented.) time, while the (Formula presented.) -facility problem is NP-hard even with uniform costs and upper bounds (maximal upgrading per edge), as well as, integer parameter values. Furthermore, a pseudo-polynomial algorithm is developed for the single facility problem on trees with integer parameters.</p

On hub location problems in geographically flexible networks

The authors were partially supported by research groups SEJ-584 and FQM-331 (Junta de Andalucia) and projects MTM2016-74983-C02-01 (Spanish Ministry of Education and Science/FEDER), FEDER-US-1256951, P18-FR-1422, P18-FR-2369 (Junta de Andalucia), CEI-3FQM331 (Andalucia Tech), and NetmeetData (Fundacion BBVA - Big Data 2019). We also would like to acknowledge Elena Fernandez (Universidad de Cadiz) for her useful and detailed comments on previous versions of this manuscript.In this paper, we propose an extension of the uncapacitated hub location problem where the potential positions of the hubs are not fixed in advance. Instead, they are allowed to belong to a region around an initial discrete set of nodes. We give a general framework in which the collection, transportation, and distribution costs are based on norm-based distances and the hub-activation setup costs depend not only on the location of the hub that are opened but also on the size of the region where they are placed. Two alternative mathematical programming formulations are proposed. The first one is a compact formulation while the second one involves a family of constraints of exponential size that we separate efficiently giving rise to a branch-and-cut algorithm. The results of an extensive computational experience are reported showing the advantages of each of the approaches.Junta de Andalucia SEJ-584 FQM-331 FEDER-US-1256951 P18-FR-1422 P18-FR-2369Spanish Government European Commission MTM2016-74983-C02-01Andalucia Tech CEI-3FQM331NetmeetData (Fundacion BBVA - Big Data 2019

Upgrading edges in the maximal covering location problem

We study the upgrading version of the maximal covering location problem with edge length modifications on networks. This problem aims at locating p facilities on the vertices (of the network) so as to maximise coverage, considering that the length of the edges can be reduced at a cost, subject to a given budget. Hence, we have to decide on: the optimal location of p facilities and the optimal edge length reductions. This problem is NP-hard on general graphs. To solve it, we propose three different mixed-integer formulations and a preprocessing phase for fixing variables and removing some of the constraints. Moreover, we strengthen the proposed formulations including valid inequalities. Finally, we compare the three formulations and their corresponding improvements by testing their performance over different datasets. © 2022 The Author(s

A Review on Distributed Denial of Service Attack On Network Traffic

Distributed Denial of Service (DDoS) attacks is the most difficult issues for network security. The attacker utilizes vast number of traded off hosts to dispatch attack on victim. Different DDoS defense components go for distinguishing and keeping the attack traffic. The adequacy relies upon the purpose of sending. The reason for this paper is to examine different detection and defense mechanism, their execution and deployment attributes. This helps in understanding which barrier ought to be sent under what conditions and at what areas

Modern International Park City and Ecological Civilization Education Practice: Taking Chengdu Tianfu Greenway as the Core

In the comprehensive development of modern park city and ecological civilization education, Chengdu has gradually explored its own path with international characteristics. The positioning of Chengdu as a “modern and beautiful park city” is an innovation proposed by Mr. Xi Jinping in recent years. This concept not only combines the geographical location of Chengdu with the regional characteristics of the western environment, but also highly respects the historical laws of the development of Chengdu’s Bashu civilization for thousands of years. At the same time, it also absorbs Howard’s “pastoral city” dream and Mountford, the theme of Gedde’s “Organic City Theory” has corrected the shortcomings of Le Corbusier’s mechanized functional space view and presented distinctive Chinese characteristics in theoretical innovation and the development of ecological civilization education. The outstanding performance is the organic integration of the development of Tianfu ecological civilization, the cultural education of Bashu and the aesthetic design practice, the creation of the international brand image of Chengdu’s “three cities and three capitals” and the innovative practical experience results of the dream of “beautiful and livable park city”

Synthesizing architecture and informality : the influence of informality in creating a responsive architecture towards the design of a resilience hub for the community of the Quarry Road informal settlement.

Masters Degree. University of KwaZulu-Natal, Durban.The world is currently facing rapid urbanization with the largest number of people moving from rural areas and countrysides to urban cores. This holds especially true in South Africa. However, as a result of a history of injustices and segregation perpetuated by apartheid and colonialism, a large portion of the South African population remains marginalised even today and occupy the left over space on the frays of cities in informal settlements, enduring poverty and exceedingly hazardous environments. Durban, the location of this study, has nearly a quarter of its inhabitants living in informal settlements (Informalcity, 2012). In a context where these informal settlement communities have become insurgent and have begun to fight for their “right to the city” and a better quality of life, the authorities have been coerced to change their policies on informal settlements and to seek a route towards their normalization as part of South African cities. It is in this context that architecture ought to revaluate its role in responding to the plight of informal settlement communities and to respond to Holston’s (in Bremner, 2010) call for a reinvention of modernist architecture’s social imperatives in these insurgent spaces. The aim of this dissertation is to explore how informality and the culture of informal settlement communities can inform architecture as a means of creating better and more responsive architectural interventions to the issues faced by communities within informal settlements. It hypothesizes that a synthesis of the architecture and informality; through an understanding of the existing socio-spatial dynamics, culture, economic networks, insurgent practices and approach to the production of built form of informal settlement communities; can produce a more responsive architecture capable of increasing informal settlement communities’ resilience to site specific challenges, improve their quality of life and ultimately aid them towards their hopes and aspirations. The literature, precedents and case studies on the subject assist in developing an understanding of the context of urban informality, the lifestyle and daily plight of the informal settlement dweller, as well as approaches towards ameliorating the challenges these communities face through a synthesis of formal and informal processes. Theories such as Culture and Identity, Insurgency and Informality provide insight into the daily life of informal settlements. Critical Regionalism begins to look at a more responsive architectural approach towards the informal, characterised by informal influences. The outcome of the architectural approach developed in this dissertation will be the conceptualization of a Resilience Hub for the Quarry Road West informal settlement community with the aim of responding to and ameliorating site specific challenges the community faces on a daily basis and ultimately improving their quality of life

STATUS OF COMMUNICATION AND TRACKING TECHNOLOGIES IN UNDERGROUND COAL MINES

In 2006, Congress passed the MINER Act requiring mine operators to submit an emergency response plan that included post-accident communications and tracking systems to MSHA within three years of the Act. These systems were required to be designed for maximum survivability after a catastrophic event, such as a fire or explosion, and to be permissible (meets MSHA criteria for explosion-proof). At that time, no commercially available systems existed that met these standards. Several companies undertook developing new, or enhancing existing, technologies to meet these requirements. This research presents the results of a study that was conducted to determine the present day types of systems being used, along with their average annual worker hours, coal production, number of mechanized mining units, and type of communications and tracking systems installed. Furthermore, 10 mines were visited to obtain detailed information related to the various technologies. It was found the most influential parameters on system selection include MSHA district, mining method, and number of underground workers

Physical internet-enabled hyperconnected distribution assessment

L'Internet Physique (IP) est une initiative qui identifie plusieurs symptômes d'inefficacité et non-durabilité des systèmes logistiques et les traite en proposant un nouveau paradigme appelé logistique hyperconnectée. Semblable à l'Internet Digital, qui relie des milliers de réseaux d'ordinateurs personnels et locaux, IP permettra de relier les systèmes logistiques fragmentés actuels. Le but principal étant d'améliorer la performance des systèmes logistiques des points de vue économique, environnemental et social. Se concentrant spécifiquement sur les systèmes de distribution, cette thèse remet en question l'ordre de magnitude du gain de performances en exploitant la distribution hyperconnectée habilitée par IP. Elle concerne également la caractérisation de la planification de la distribution hyperconnectée. Pour répondre à la première question, une approche de la recherche exploratoire basée sur la modélisation de l'optimisation est appliquée, où les systèmes de distribution actuels et potentiels sont modélisés. Ensuite, un ensemble d'échantillons d'affaires réalistes sont créé, et leurs performances économique et environnementale sont évaluées en ciblant de multiples performances sociales. Un cadre conceptuel de planification, incluant la modélisation mathématique est proposé pour l’aide à la prise de décision dans des systèmes de distribution hyperconnectée. Partant des résultats obtenus par notre étude, nous avons démontré qu’un gain substantiel peut être obtenu en migrant vers la distribution hyperconnectée. Nous avons également démontré que l'ampleur du gain varie en fonction des caractéristiques des activités et des performances sociales ciblées. Puisque l'Internet physique est un sujet nouveau, le Chapitre 1 présente brièvement l’IP et hyper connectivité. Le Chapitre 2 discute les fondements, l'objectif et la méthodologie de la recherche. Les défis relevés au cours de cette recherche sont décrits et le type de contributions visés est mis en évidence. Le Chapitre 3 présente les modèles d'optimisation. Influencés par les caractéristiques des systèmes de distribution actuels et potentiels, trois modèles fondés sur le système de distribution sont développés. Chapitre 4 traite la caractérisation des échantillons d’affaires ainsi que la modélisation et le calibrage des paramètres employés dans les modèles. Les résultats de la recherche exploratoire sont présentés au Chapitre 5. Le Chapitre 6 décrit le cadre conceptuel de planification de la distribution hyperconnectée. Le chapitre 7 résume le contenu de la thèse et met en évidence les contributions principales. En outre, il identifie les limites de la recherche et les avenues potentielles de recherches futures.The Physical Internet (PI) is an initiative that identifies several symptoms of logistics systems unsustainability and inefficiency and tackles them by proposing a novel paradigm called Hyperconnected Logistics. Similar to the Digital Internet, which connects thousands of personal and local computer networks, PI will connect the fragmented logistics systems of today. The main purpose is to enhance the performance of logistics systems from economic, environmental and social perspectives. Focusing specifically on the distribution system, this thesis questions the order of magnitude of the performance gain by exploiting the PI-enabled hyperconnected distribution. It is also concerned by the characterization of the hyperconnected distribution planning. To address the first question, an exploratory research approach based on optimization modeling is applied; first, the current and prospective distribution systems are modeled. Then, a set of realistic business samples are created, and their economic and environmental performance by targeting multiple social performances are assessed. A conceptual planning framework is proposed to support the decision making in the hyperconnected distribution system. Based on the results obtained by our investigation, it can be argued that a substantial gain can be achieved by shifting toward Hyperconnected Distribution. It is also revealed that the magnitude of the gain varies by business characteristics and the targeted social performance. Since the Physical Internet is a novel topic, chapter 1 briefly introduces PI and Hyperconnected Logistics. Chapter 2 discusses the research foundations, goal and methodology. It also describes the challenges of conducting this research and highlights the type of contributions aimed for. Chapter 3 presents the optimization models including a core distribution network design modeling approach. Influenced by the characteristics of the current and prospective distribution systems, three distribution system-driven models are developed. Chapter 4 engages with the characterization of the business samples, the modeling and calibration of the parameter that are employed in the models. The exploratory investigation results are presented in Chapter 5. Chapter 6 describes the hyperconnected distribution planning framework. Chapter 7 summarizes the content of the thesis and highlights the main contributions. Moreover, it identifies the research limitations and potential future research avenues