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Optimal Tradeoffs in Matched Designs Comparing US-Trained and Internationally Trained Surgeons

Journal of the American Statistical Association 2020年第532期115卷 1675-1688页

作者： Pimentel, Samuel D. Kelz, Rachel R. Department of Statistics University of California Berkeley Berkeley CA United States Perelman School of Medicine University of Pennsylvania Philadelphia PA United States

Does receiving a medical education outside the United States impact a surgeon’s performance? We study this question by matching operations performed by internationally trained surgeons to those performed by US-trained surgeons in reanalysis of a large health outcomes study. An effective matched design must achieve several goals, including balancing covariate distributions marginally, ensuring units within individual pairs have similar values on key covariates, and using a sufficiently large sample from the raw data. Yet in our study, optimizing some of these goals forces less desirable results on others. We address such tradeoffs from a multi-objective optimization perspective by creating matched designs that are Pareto optimal with respect to two goals. We provide general tools for generating representative subsets of Pareto optimal solution sets and articulate how they can be used to improve decision-making in observational study design. In the motivating surgical outcomes study, formulating a multi-objective version of the problem helps us balance an important variable without sacrificing two other design goals, average closeness of matched pairs on a multivariate distance and size of the final matched sample. Supplementary materials for this article, including a standardized description of the materials available for reproducing the work, are available as an online supplement. © 2020 American Statistical Association.

关键词： Fine balance Matching Multi-objective optimization network flow optimization Pareto optimality

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New Multi-Commodity flow Formulations for the Generalized Pooling Problem

New Multi-Commodity Flow Formulations for the Generalized Po...

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10th IFAC Symposium on Advanced Control of Chemical Processes (ADCHEM)

作者： Cheng, Xin Tang, Kai Li, Xiang Queens Univ Dept Chem Engn Kingston ON K7L 3N6 Canada

The generalized pooling problem is involved in many planning and scheduling problems in the petrochemical industry. Compared to the standard pooling problem where the blenders (or pools) are not allowed to be connected to one another, the generalized pooling problem has a more complex network structure and allows more types of problem formulations. The state-of-the-art generalized pooling formulations adopt a multi-commodity flow (MCF) strategy that was first proposed by Alfaki and Haugland (2013a) and proved to be stronger than the classical p-formulation. This paper proposes two new MCF formulations for the generalized pooling problem, using mixing and split fractions of blenders rather than the commodity flow fractions. The case study results show that, for some cases, the proposed formulations perform better than the existing MCF formulations, but none of the formulations dominates others for all cases. The results also show that formulations which have similar sizes and similarly tight linear programming relaxations may have dramatically different performance. (C) 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

关键词： Pooling problem Multi-commodity flow Global optimization Blending network flow optimization

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A Novel Approach for Providing QoS with network Coding

A Novel Approach for Providing QoS with Network Coding

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International Symposium on Telecommunications

作者： Salavati, Amir Hesam Khalaj, Babak Hosein Aref, Mohammad Reza Sharif Univ Technol Sch Elect Engn Tehran Iran

ISBN: (纸本)9781424427505

In this paper, we present a decentralized algorithm that computes minimum cost QoS flow sub-graphs in network coded multicast networks. These subgraphs are minimum cost solutions that also satisfy user-specified QoS constraints, specifically handling elastic rate and delay demands. Although earlier network coding algorithms in this area have only demonstrated QoS improvements, the proposed QoS network coding is clearly different in the sense that it guarantees that given QoS constraints are met over the network.

关键词： network coding Quality of service network flow optimization

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Singlow: Simulator for General network flow Problems

Singlow: Simulator for General Network Flow Problems

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International Conference on Innovative Trends in Information Technology (ICITIIT)

作者： Raghavan, S. Bhagtya, Paras Chandrasekaran, K. Natl Inst Technol Dept Comp Sci & Engn Surathkal Karnataka India

ISBN: (数字)9781728142104

ISBN: (纸本)9781728142104

Simulation is an important process and an inevitable part of engineering. There are several applications of simulation with one of the important being visualization of complex methods and processes. This paper aims at creating a simulator for general network flow optimization problems. This work uses a modular approach for creating a simulator. A simulator in this area is necessary for several reasons. The main reason for requirement is its usefulness in explaining the problems to the people/students who might use these kinds of network optimization methods to solve several variety of problems. This simulator can simulate standard problems namely transportation problems with various methods, network flow problem and some popular problems in that area. This simulator will be helpful for educational institutions to teach the students about the standard problems on network flow optimization. Here this paper proposes a framework i.e. Singlow for the above mentioned purpose. This paper explains the framework with the flow of execution by keeping in mind a general simulation software. The Simulator has been designed and implemented using Processing 3.4, a software which facilitates designing graphical user interfaces.

关键词： Simulation network flow optimization Vogels Approximation Method Singlow Force-directed algorithm

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Bandwidth allocation in ATM networks

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Annals of Operations Research 1994年第1期49卷 25-50页

作者： Monteiro, José Augusto Suruagy Gerla, Mario Departmento de Informática Universidade Federal de Pernambuco Recife-PE 50732-970 Caixa Postal 7851 Brazil Computer Science Department University of California at Los Angeles Los Angeles 90024 CA United States

In an ATM network, bandwidth is allocated at different levels and in different stages. At the physical level, the ATM topology can be dynamically reconfigured by adding/removing truns between ATM switches. This allocation of bandwidth is made possible by the SONET Synchronous Transfer Mode (STM) infrastructure equipped with Digital Cross Connect Systems (DCSs). We will refer to this allocation as STM allocation. At the ATM level, we can allocate bandwidth to individual Virtual Circuits (ATM-VC allocation) as well as to Virtual Paths (ATM-VP allocation). For example, in order to implement the Connectionless network Access layer functions we find it convenient to organize the Virtual Paths in a Connectionless Overlay network. This introduces another type of bandwidth allocation (CLS allocation). In this paper, we address and formulate the above bandwidth allocation problems, and propose efficient techniques for their solution. We illustrate these techniques with examples based on STM and CLS allocation, respectively. © 1994 J.C. Baltzer AG, Science Publishers.

关键词： ATM ATM connectionless overlay network bandwidth allocation network flow optimization routing topology design

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(MP)²T: Multiple People Multiple Parts Tracker

(MP)<SUP>2</SUP>T: Multiple People Multiple Parts Tracker

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12th European Conference on Computer Vision (ECCV)

作者： Izadinia, Hamid Saleemi, Imran Li, Wenhui Shah, Mubarak Univ Cent Florida Comp Vis Lab Orlando FL 32816 USA

ISBN: (纸本)9783642337826

We present a method for multi-target tracking that exploits the persistence in detection of object parts. While the implicit representation and detection of body parts have recently been leveraged for improved human detection, ours is the first method that attempts to temporally constrain the location of human body parts with the express purpose of improving pedestrian tracking. We pose the problem of simultaneous tracking of multiple targets and their parts in a network flow optimization framework and show that parts of this network need to be optimized separately and iteratively, due to inter-dependencies of node and edge costs. Given potential detections of humans and their parts separately, an initial set of pedestrian tracklets is first obtained, followed by explicit tracking of human parts as constrained by initial human tracking. A merging step is then performed whereby we attempt to include part-only detections for which the entire human is not observable. This step employs a selective appearance model, which allows us to skip occluded parts in description of positive training samples. The result is high confidence, robust trajectories of pedestrians as well as their parts, which essentially constrain each other's locations and associations, thus improving human tracking and parts detection. We test our algorithm on multiple real datasets and show that the proposed algorithm is an improvement over the state-of-the-art.

关键词： multi-target tracking pedestrians humans body part tracking network flow optimization k-shortest paths

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Balancing Multiple Goals In Observational Study Design

Balancing Multiple Goals In Observational Study Design

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作者： Samuel Pimentel University of Pennsylvania

学位级别：博士

This thesis unites three papers discussing new strategies for matched pair designs using observational data, developed to balance the demands of various disparate design goals. The first chapter introduces a new matching algorithm for large-scale treated-control comparisons when many categorical covariates are present. The algorithm balances covariates and their interactions in a prioritized manner by solving a combinatorial optimization problem, and guarantees computational efficiency through the use of a sparse network representation. The second chapter defines a class of variables called prods which can be ignored when matching in order to strictly attenuate unmeasured bias, if it is present. These variables can be difficult to identify with confidence, so a multiple-control-group strategy is proposed in which investigators match once on all variables, and once ignoring prods; the two treated-control comparisons together give stronger evidence about treatment effects than either one individually. The final paper considers a new version of Fisher's classical lack-of-fit test for regression models, appropriate for data that lack replicated observations. The test uses matched pairs formed by optimal nonbipartite matching as near-replicates, and the model fit is used is used in constructing the matching distance in order to focus attention on variables that are predictive in the null model.

关键词： Causal Inference Combinatorial optimization Lack of fit Matching network flow optimization Unmeasured bias

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Escape from the Delta: preparation and evacuation for catastrophic flooding in California Emergency Management Agency Region IV

Escape from the Delta: preparation and evacuation for catast...

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作者： Yuhas, Timothy C. Naval Postgraduate School

学位级别：硕士

We model the regional highway system of Central California and consider the challenge of evacuating a highly populated region from the threat of catastrophic flood. Specifically, we build a minimum cost network flow problem to represent the movement of more than one million people within Yolo, Sacramento, San Joaquin, and Stanislaus Counties. Our model solves for "best case" evacuation routes and clearing times assuming perfect knowledge of flood inundation and road conditions. Our model is large but efficient, solving 35 separate scenarios in less than 45 minutes. We develop two basic evacuation scenarios, each having many variations, resulting in 490 total scenarios. For these, we analyze model assumptions and the effect of interruptions to evacuation behavior for a range of "what-if" situations.

关键词： Evacuation network flow optimization Minimum Cost network flow

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Effects of burstiness on the air transportation system

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Physical Review E 2017年第1期95卷 012325-012325页

作者： Hidetaka Ito Katsuhiro Nishinari Department of Aeronautics and Astronautics School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Research Center for Advanced Science and Technology The University of Tokyo 4-6-1 Komaba Meguro-ku Tokyo 153-8904 Japan

The effects of burstiness in complex networks have received considerable attention. In particular, the effects on temporal distance and delays in the air transportation system are significant owing to their huge impact on our society. Therefore, in this paper, the temporal distance of empirical U.S. flight schedule data is compared with that of regularized data without burstiness to analyze the effects of burstiness. The temporal distance is calculated by a graph analysis method considering flight delays, missed connections, flight cancellations, and congestion. In addition, we propose two temporal distance indexes based on passengers' behavior to quantify the effects. As a result, we find that burstiness reduces both the scheduled and the actual temporal distances for business travelers, while delays caused by missed connections and congestion are increased. We also find that the decrease of the scheduled temporal distance by burstiness is offset by an increase of the delays for leisure passengers. Moreover, we discover that the positive effect of burstiness is lost when flight schedules are overcrowded.

关键词： network flow optimization Robustness Transportation Transportation networks Weighted networks

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Cross quantum homomorphic encryption based on the butterfly network

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Physical Review A 2024年第6期109卷 062606-062606页

作者： Xing-bo Pan Yu-Ting Lei Xiang-jie Li Xiu-bo Chen Gui-lu Long State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics

Quantum homomorphic encryption hides quantum information from unauthorized participants while still allowing them to perform calculations on encrypted quantum information. In this paper, we propose a cross quantum homomorphic encryption scheme based on the butterfly network, in which every receiver can receive the evaluated quantum state with perfect fidelity. The entangled states between senders of the butterfly network are preshared, and the Bell basis measurements are used to encrypt the quantum plaintext. With both classical and quantum channels, the homomorphic evaluation of quantum plaintext can be completed on the butterfly network perfectly and crossly. Our scheme solves a bottleneck problem of cross evaluation at the bottleneck nodes, and improves the evaluation efficiency and total network throughput. In addition, we have designed quantum circuits according to different quantum evaluations with a butterfly network, which provide a basic blueprint for experimental implementation. The security of the scheme is also analyzed.

关键词： Communication schemes network flow optimization Quantum circuits Quantum communication Quantum state transfer

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