A multi-speed drive hub is one of important components in transmission system. The purpose of this work is to develop a system methodology for the design of multi-speed bicycle drive hubs. First, identify the basic characteristics and design requirement of multi-speed drive hub. Second, using the useful gear trains. Third, a method is proposed to determine the feasible multi-speed sequence tables for each gear train. Fourth, an analytic method is formulated to synthesize the gear ratios and gear teeth according to a set of desired speed ratios. Fifth, the basic theory for transmission analysis of multi-speed drive hubs will be developed. The results of this work will be benefit to the development and design of multi-speed bicycle drive hubs.

Bachelor-Arbeit Univ. St. Gallen, 2008.

Le développement de structures de réseau efficaces pour le transport de marchandises est fondamental sur le marché mondial actuel. Les demandes doivent être traitées rapidement, répondre aux besoins des clients dans les meilleurs délais, les congestions et les retards doivent être minimisés, les émissions de CO2 doivent être contrôlés et des coûts de transport moins élevés doivent être proposés aux clients. La structure hub-and-spoke est un modèle de réseau courant utilisé à la fois dans le transport régional comme dans le transport intercontinental, permettant une économie d'échelle grâce aux consolidations opérées au niveau des noeuds hub. Mais, les retards, les congestions et les longs délais de livraison sont des inconvénients de ce type de réseau. Dans cette thèse, un nouveau concept, "sub-hub", est ajouté à la structure du réseau classique hub-and-spoke. Dans les modèles de réseau proposés, une économie d'échelle et des chemins alternatifs plus courts sont mis en oeuvre, en minimisant ainsi le coût de transport et le délai de livraison. Le sub-hub est vu comme un point de connexion entre deux routes distinctes de régions voisines. Des transbordements sans passer par les noeuds hub sont possibles au niveau des sub-hubs. Des congestions peuvent ainsi être évitées et, par conséquent, les retards associés sont ainsi minimisés. Quatre modèles de programmation linéaire en nombres entiers binaires du problème de la localisation de hubs et de routage sont développés dans cette thèse. Des réseaux avec sub-hub et des réseaux sans sub-hub prenant en compte des routes circulaires entre hubs ou des connexions directes entre hubs sont ainsi comparées. Ces modèles sont composés de quatre sous-problèmes (localisation, allocation, conception de service et routage) qui rendent complexe la recherche de solutions. Une approche cutting plane est testée pour résoudre de petites instances de problème tandis qu'une recherche à voisinage variable avec décomposition (VNDS) composée de méthodes exactes (matheuristic) a été développée pour résoudre de grandes instances. Le VNDS mis en oeuvre, explore chaque sous-problème avec différents opérateurs. Des gains importants dans la fonction objective sont observés par les modèles avec sub-hub confirmant ainsi le développement de réseaux plus compétitifs. / The development of efficient network structures for freight transport is a major concern for the current global market. Demands need to be quickly transported and should also meet the customer needs in a short period of time. Traffic congestions and delays must be minimized, since CO2 emissions must be controlled and affordable transport costs have to be offered to customers. Hub-and-spoke structure is a current network model used by both regional and intercontinental transportation, which offers an economy of scale for aggregated demands inside hub nodes. However, delays, traffic congestions and long delivery time are drawbacks from this kind of network. In this thesis, a new concept, which is called "sub-hub", is proposed to the classic hub-and-spoke network structure. In the proposed network models, economy of scale and shorter alternative paths are implemented, thus minimizing the transport cost and delivery time. The sub-hub proposal can be viewed as a connection point between two routes from distinct and close regions. Transshipments without the need to pass through hub nodes are possible inside sub-hubs. This way, congestions can be avoided and, consequently, delays are minimized. Four binary integer linear programming models for hub location and routing problem were developed in this thesis. Networks with sub-hub and networks without sub-hub taking into account circular hub routes or direct connections between hubs are compared. These models are composed of four sub-problems (location, allocation, service design and routing), which hinders the solution. A cutting plane approach was used to solve small instances of problem, while a Variable Neighborhood Decomposition Search (VNDS) composed of exact methods (matheuristic) was developed to solve large instances. The VNDS was used to explore each sub-problem by different operators. Major benefits are provided by models with sub-hub, thus promoting the development of more competitive networks.

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This thesis presents a further study on Dai and Zhang’s (2008) supply networks, which are Cost Saver, Adapter, and Multiple Driven. This concept is centred on hub or focal firm which is the core of the supply networks, built on Miles and Snow’s (2003) strategic typology. In Cost Saver supply network, the hub firm is ‘Defender’; for Adapter supply network it is ‘Prospector’, while in Multiple Driven supply network it is ‘Analyser’. This study explores the interrelationship between the hub and supplier’s configuration and its effect on organisational performance. A comprehensive literature review is carried out with reference to supply chain (SC), supply network (SN) and supply network management (SNM). It stretches to describing Dai and Zhang’s (2008) novel supply networks, its association with Miles and Snow’s theory, the supply network configuration concept, and further expatiates on the need for appropriate supplier configuration for improved performances within the supply networks. The key performance indicators (KPI) adopted for this work, the variables considered in the simulation modelling were evaluated. Usable data were collected from a sample of 630 suppliers, and 15 hub firms. This is accompanied by Hypotheses testing, Case study and Simulation experiments to fulfil the aims and objectives of this research. From the findings of this study, it is confirmed that organisations can be grouped as either the Defender, Prospector, Analyser or Reactor type according to the Miles and Snow typology. The investigation identified that for Multiple Driven, Adapter and Cost Saver supply networks, performances are most improved with an increase in the existence of suppliers of the same typology with the hub organisation within the supply network.

Transportation systems such as mail, freight, passenger and even telecommunication systems most often employ a hub and spoke network structure since correctly designed they give a strong balance between high service quality and low costs resulting in an economically competitive operation. In addition, consumers are increasingly demanding fast and reliable transportation services, with services such as next day deliveries and fast business and pleasure trips becoming highly sought after. This makes finding an efficient design of a hub and spoke network of the utmost importance for any competing transportation company. However real life situations are complicated, dynamic and often require responses to many different fixed and random events. Therefore modeling the question of what is an optimal hub and spoke network structure and finding an optimal solution is very difficult. Due to this, many researchers and practitioners alike make several assumptions and simplifications on the behavior of such systems to allow mathematical models to be formulated and solved optimally or near optimally within a practical timeframe. Some assumptions and simplifications can however result in practically poor network design solutions being found. This thesis contributes to the research of hub and spoke networks by introducing new stochastic models and fast solution algorithms to help bridge the gap between theoretical solutions and designs that are useful in practice. Three main contributions are made in the thesis. First, in Chapter 2, a new formulation and solution algorithms are proposed to find exact solutions to a stochastic p-hub center problem. The stochastic p-hub center problem is about finding a network structure, where travel times on links are stochastic, which minimizes the longest path in the network to give fast delivery guarantees which will hold for some given probability. Second, in Chapter 3, the stochastic p-hub center problem is looked at using a new methodological approach which gives more realistic solutions to the network structures when applied to real life situations. In addition a new service model is proposed where volume of flow is also accounted for when considering the stochastic nature of travel times on links. Third, in Chapter 4, stochastic volume is considered to account for capacity constraints at hubs and, de facto, reduce the costs embedded in excessive hub volumes. Numerical experiments and results are conducted and reported for all models in all chapters which demonstrate the efficiency of the new proposed approaches.

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No description available.

A Vegan Hub in the heart of Stockholm. A place where to learn, get inspired, feel fellowship, have fun. A place where to visit an exhibition about the negative aspects of not being a vegan or come have food and drinks, watch documentaries, participate in cooking classes, find the latest vegan products, go on events or simply to enjoy the beautiful view. A place that hopefully can kill assumptions, spread the positivity about veganism and be a great example of a brighter future.

This dissertation proposes a framework in support of biomass supply chain network design. This framework relies in the use of trucks for short distance biomass transportation, and relies in the use of rail for long-haul, and high-volume transportation of densified biomass. A hub and spoke network design model is proposed for the case when biomass is shipped by rail. These models are created and solved for the following problems: 1) designing a biomass supply chain to deliver densified biomass to a coal fired power plant for coiring and 2) designing biomass-to-biorefinery supply chain using rail for long-haul, and high-volume shipment of densified biomass under economic, environmental, and social criteria. The first problem is modeled as a Mixed-Integer Linear Programming (MILP). A Benders’ decomposition-based algorithm is developed to solve the MILP model because its large size makes it difficult to solve using CPLEX. The numerical analysis indicates that the total unit transportation cost from the farm to a coal plant is $36/ton. Numerical analysis also indicates that biomass cofiring is cost efficient compare to direct coal firing if the renewable energy production tax credit is applied and biomass is located within 75 miles from a coal plant. The second problem is also modeled as a MILP mode. This MILP identifies the number, capacity and location of biorefineries needed to make use of the biomass available in the region. A case study is created using data from a number of States in the Midwest USA. The numerical analysis show that 24.38%-26.12% of the target cellulosic biofuel set by the Energy Independence and Security Act of 2007 can be met at delivery cost $4.01 to $4.02 per gallon. The numerical analysis also reveals the tradeoffs that exist among the economics, environmental impact, and social objectives of using densified biomass for production of biofuel. Finally, this dissertation presents a detailed analysis of the rail transportation cost for products that have similar physical characteristics to densified biomass and biofuel. A numbers of regression equations are developed in order to evaluate and quantify the impact of important factors on the unit transportation cost.