1,720,980 research outputs found
Uncertainty and Cancellations in Advance Surgery Scheduling: An Exact Pattern-Based Solution Approach for Large-Scale Problems applied in a Rolling Horizon Simulation
Full text linkSt. Olavs hospital, Midt-Norges største helseinstitusjon, forventer en økning i etterspørsel på 35 % for kirurgiske inngrep grunnet demografiske endringer. Mangelen på helsepersonell og ressurser gjør effektiv operasjonsplanlegging kritisk. Denne studien setter søkelys på å forbedre kirurgisk planlegging ved sykehusets ortopediavdeling ved å forbedre den eksisterende matematiske modellen foreslått av Schiøtz og Tysse (2022) for operasjonsplanlegginsproblemet ved å inkludere faktorer som usikker operasjonsvarighet og restitusjonstid.
Vi utvikler matematiske modeller som tar sikte på å overholde avdelingens planleggingsregler, prioritere reduksjon av pasientens ventetid og avbrudd i tidsplanen, og ta hensyn til ressurser som operasjonsrom, sengeposter og den overordnede operasjonsplanen ved sykehuset. Denne studien vil også undersøke effektene av å inkludere en kanselleringsregel i sykehusets planleggingssystem og vurdere hvordan regelen kan påvirke planleggingskvaliteten samtidig som risikoen forbundet med overtid og kanselleringer reduseres.
For kvantitativ sammenligning er de foreslåtte planleggingsmodellene integrert i et simuleringsrammeverk med en rullende horisont. Blant betydelige bidrag fra studien er inkluderingen av kanselleringsregler og re-planlegging av pasienter i modellene, og håndtering av store og virkelighetsnære problemstørrelser. Vi har utviklet en mønsterbasert blandet heltallsmodell som klarer å løse problemer av reell størrelse til optimalitet, i motsetning til tradisjonelle to-stegs stokastiske modeller. Modellen tar hensyn til usikkerhet, og klarer i mange tilfeller å lage bedre operasjonsplaner enn en to-stegs modell i våre tester.
Forskningsresultatene våre understreker viktigheten av beregningseffektivitet og avslører et grunnleggende dilemma mellom stabilitet i operasjonsplanen og effektivitet. Et interessant funn er at deterministiske modeller undervurderer overtid, noe som understreker viktigheten av å inkludere usikkerhet, spesielt når vi inkluderer kanselleringsregler. Skalerbarheten til den mønsterbaserte heltallsmodellen, og avanserte filtreringsmetoder for mønstre ved bruk av maskinlæringsteknikker potensielle fremtidige forskningsområder.St. Olavs hospital, central Norway's largest healthcare institution, anticipates a demand increase of 35 % for surgical procedures due to demographic shifts. The shortage of healthcare professionals and resources makes efficient surgery scheduling mission critical. This study focuses on enhancing surgical scheduling at the hospital's Department of Orthopedics by improving the existing mathematical model proposed by Schiøtz and Tysse (2022) for the Advance Scheduling Problem (ASP), incorporating factors like uncertain surgery duration and recovery time.
The enhanced models aim to abide by the department's scheduling rules, prioritize the reduction of patient waiting time and schedule disruption, and account for resources like operating rooms, recovery wards, and the Master Surgery Schedule. This study will also explore the impact of integrating a cancellation rule into the hospital's scheduling system and assess how it might influence the scheduling quality while mitigating the risks associated with overtime and cancellations.
The proposed scheduling models are integrated into a simulation framework using a rolling horizon approach for quantitative comparison. Among the significant contributions of this research are incorporating cancellation rules and rescheduling of surgical cases into the models and handling large problem sizes akin to real-life scenarios at elective clinics. We propose a pattern-based Mixed-Integer Program that can solve real-life size problems to optimality, something traditional two-stage stochastic models can not. Our model considers uncertainty and manages to produce a better surgery schedule than two-stage models in multiple of our tests.
Our research results underscore the importance of computational efficiency and reveal a fundamental dilemma between schedule stability and efficiency. Interestingly, deterministic models were found to underestimate overtime, underscoring the importance of including uncertainty, especially when cancellation rules apply. Future research areas include the scalability of the pattern-based Mixed-Integer Program and advanced pattern filtering methods using machine learning techniques
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Managing Uncertainty in Design and Operation of Natural Gas Infrastructure
No full textSummary of the thesis: This thesis concerns the management of uncertainty in design and operation of natural gas infrastructure by means of mathematical programming. The export of natural gas is an important industry in Norway. Investments in infrastructure such as subsea pipelines and processing facilities with long lifetime are capital intensive and mandate thorough analysis of future cash flows to assess profitability.
Several crucial parameters are uncertain, such as resources, costs and future prices, and analysis of net present value should consider this uncertainty carefully. The long lifetime with significant short-term uncertainty and variability in addition to long-term uncertainty makes this particularly challenging.
Natural gas is not a homogenous commodity, and different composition of gas from each field makes the management of gas quality an important consideration. Gas quality may be altered through mixing in the transport pipeline network, or in processing facilities. Accounting for pooling in the network with quality constraints introduces computationally expensive non-convex formulations.
The main contributions of the work in this thesis consists of modelling short- and long-term uncertainty for design and operation of natural gas networks in models that combine these demands and introduce multi-horizon stochastic programming.
The pooling problem is addressed by a novel discretization scheme and auxiliary linear programs that will improve solution times in many instances. A generalized global optimization multi-commodity pooling formulation with processing facilities and composite quality constraints is appropriate for analysis in this context.
Traditionally, analysts consider uncertainty as exogenous, i.e. unaffected by the decisions in the model. In this thesis, the work on stochastic programming with endogenous uncertainty is reviewed with an expanded taxonomy, with several novel models with decision-dependent probabilities. This demonstrates how this problem may be addressed through the framework of stochastic programming with recourse
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Decision-dependent probabilities in stochastic programs with recourse
No full textStochastic programming with recourse usually assumes uncertainty to be exogenous. Our work presents modelling and application of decision-dependent uncertainty in mathematical programming including a taxonomy of stochastic programming recourse models with decision-dependent uncertainty. The work includes several ways of incorporating direct or indirect manipulation of underlying probability distributions through decision variables in two-stage stochastic programming problems. Two-stage models are formulated where prior probabilities are distorted through an affine transformation or combined using a convex combination of several probability distributions. Additionally, we present models where the parameters of the probability distribution are first-stage decision variables. The probability distributions are either incorporated in the model using the exact expression or by using a rational approximation. Test instances for each formulation are solved with a commercial solver, BARON, using selective branching
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