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The MultiTree Approach to Reliability in Distributed Networks
 Information and Computation
, 1984
"... Consider a network of asynchronous processors communicating by sending messages over unreliable lines. There are many advantages to restricting all communications to a spanning tree. To overcome the possible failure of k <k edges, we describe a communication protocol which uses k rooted spanning ..."
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Cited by 77 (1 self)
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Consider a network of asynchronous processors communicating by sending messages over unreliable lines. There are many advantages to restricting all communications to a spanning tree. To overcome the possible failure of k <k edges, we describe a communication protocol which uses k rooted spanning trees having the property that for every vertex v the paths from v to the root are edgedisjoint. An algorithm to find two such trees in a 2 edgeconnected graph is described that runs in time proportional to the number of edges in the graph. This algorithm has a distributed version which finds the two trees even when a single edge fails during their construction. The two trees them may be used to transform certain centralized algorithms to distributed, reliable and efficient ones.  1  1. INTRODUCTION Consider a network G=(V ,E ) of n = V asynchronous processors (or vertices) connected by e = E edges. The network may be used to conduct a computation which cannot be done in a single pr...
Shipper collaboration
 Computers & Operations Research
, 2007
"... The interest in collaborative logistics is fuelled by the ever increasing pressure on companies to operate more efficiently, the realization that suppliers, consumers, and even competitors, can be potential collaborative partners in logistics, and the connectivity provided by the Internet. Logistics ..."
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Cited by 5 (1 self)
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The interest in collaborative logistics is fuelled by the ever increasing pressure on companies to operate more efficiently, the realization that suppliers, consumers, and even competitors, can be potential collaborative partners in logistics, and the connectivity provided by the Internet. Logistics exchanges or collaborative logistics networks use the Internet as a common computing platform to implement strategies designed to reduce “hidden costs ” such as asset reposition costs. Through collaboration shippers may be able to identify and submit tours with little or no asset repositioning to a carrier, as opposed to submitting individual lanes, in return for more favorable rates. In this paper, we focus on finding a set of tours connecting regularly executed truckload shipments so as to minimize asset repositioning. Mathematically, the truckload shipper collaboration problem translates into covering a subset of arcs in a directed Euclidean graph by a minimum cost set of constrained cycles. We formulate the lane covering problem, propose several solution algorithms, and conduct a computational study on the effectiveness of these methodologies. 1 1
The 7/5 Conjecture Strengthens Itself
, 1995
"... The following is proved: if every bridgeless graph G has a cycle cover of length at most 7/51€(G)I, then every bridgeless graph G has a cycle cover of length at most 7/51€(G)I such that any edge of G is covered once or twice. ..."
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Cited by 1 (0 self)
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The following is proved: if every bridgeless graph G has a cycle cover of length at most 7/51€(G)I, then every bridgeless graph G has a cycle cover of length at most 7/51€(G)I such that any edge of G is covered once or twice.
Procurement in Truckload Transportation
, 2007
"... We address a number of operational challenges encountered in two emerging types of practices in the procurement of truckload transportation services: collaboration and auctions. The main objective in these two types of procurement strategies is identifying and exploiting synergies between the lanes ..."
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We address a number of operational challenges encountered in two emerging types of practices in the procurement of truckload transportation services: collaboration and auctions. The main objective in these two types of procurement strategies is identifying and exploiting synergies between the lanes of a carrier's network. In shipper collaboration, we take the perspective of a shipper who collaborates with other shippers to seek synergy between his lanes and other participants' lanes. On the other hand, in procurement auctions, although we take the carriers' perspective in our work, a shipper tries to discover the carrier (or carriers) whose network has the most synergy with his lanes. The first part of the thesis concerns the solution of optimization problems arising in collaborative transportation procurement networks where a group of shippers comes together and jointly negotiates with carriers for the procurement of transportation services. Through collaboration, shippers may be able to identify and submit sequences of continuous loaded movements to carriers, reducing the carriers' need for repositioning, and thus lowering the carriers' costs. A portion of the carriers' cost savings may be returned to the shippers in the form of lower prices. We discuss optimization technology that helps identify repeatable, dedicated truckload continuous move tours with little truck repositioning. Timing considerations are critical to practical viability and are a key focus of our efforts. We demonstrate the effectiveness of our algorithms on randomly generated instances as well as on instances derived from realworld data. The second part concerns the pricing of transportation services offered by the trucking companies (carriers). We look at the bid determination problem faced by carriers in transportation procurement auctions where a shipper requests quotes from multiple carriers and purchases the services of the lowest bidder. The specific problem being studied is the bid valuation problem in the case where the carrier must place bids on multiple lanes simultaneously. We model the problem as a stochastic optimization problem and propose a coordinate search algorithm for solving this problem. Then, we conduct a simulation study to demonstrate the positive impact of the approach on carrier profits.
A Parallel Algorithm for Approximating the Minimum Cycle Cover
"... We address the problem of approximating a minimum cycle cover in parallel. We give the first efficient parallel algorithm for finding an approximation to a minimum cycle cover. Our algorithm finds a cycle cover whose size is within a factor of O(1 + n log n m+n ) of the minimum sized cover using O ..."
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We address the problem of approximating a minimum cycle cover in parallel. We give the first efficient parallel algorithm for finding an approximation to a minimum cycle cover. Our algorithm finds a cycle cover whose size is within a factor of O(1 + n log n m+n ) of the minimum sized cover using O(log² n) time on (m + n)= log n processors.