Silvio Hamacher

Silvio Hamacher
Pontifical Catholic University of Rio de Janeiro · Department of Industrial Engineering (IND)

PhD

About

147
Publications
31,292
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2,880
Citations

Publications

Publications (147)
Article
Full-text available
Background Long COVID is an emerging global public health issue. Socially vulnerable communities in low- and-middle-income countries were severely impacted by the pandemic and are underrepresented in research. This prospective study aimed to determine the prevalence of long COVID, its impact on health, and associated risk factors in one such commun...
Article
Full-text available
Objectives No consensus exists about the best COVID-19 vaccination strategy to be adopted by low-income and middle-income countries. Brazil adopted an age-based calendar strategy to reduce mortality and the burden on the healthcare system. This study evaluates the impact of the vaccination campaign in Brazil on the progression of the reported COVID...
Article
Full-text available
Machine scheduling is one of the most studied problems due to its technical challenges and prevalence in real life. In the literature, continuous- and discrete-time formulations are the two most known formulations for scheduling problems. However, continuous-time formulations often suffer from weak linear relaxations, while discrete-time formulatio...
Article
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Introduction: Few community-based interventions addressing the transmission control and clinical management of COVID-19 cases have been reported, especially in poor urban communities from low-income and middle-income countries. Here, we analyse the impact of a multicomponent intervention that combines community engagement, mobile surveillance, mas...
Conference Paper
Full-text available
This work presents 2 formulations for the heterogeneous fleet sizing for well drilling and completion with time-window and precedence relations. The two formulations are based on machine scheduling problems. The first one is inspired by a classical time-indexed formulation where time is discretized in days, and the second one is a bucket-indexed mo...
Conference Paper
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Oil Exploration and Production is a key part of the Supply Chain of the Oil & Gas sector. The phases related to this step can take many years and require high investments associated with wells' building and critical materials and resources hiring. Therefore, this paper presents a case study of a Brazilian company and proposes a new mathematical pro...
Article
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Background The lack of precise definitions and terminological consensus about the impact studies of COVID-19 vaccination leads to confusing statements from the scientific community about what a vaccination impact study is. Objective The present work presents a narrative review, describing and discussing COVID-19 vaccination impact studies, mapping...
Article
Objectives: To understand differences in antimicrobial use between COVID-19 and non-COVID-19 patients. To compare two metrics commonly used for antimicrobial use: Defined Daily Dose (DDD) and Days of Therapy (DOT). To analyse the order in which antimicrobials were prescribed to COVID-19 patients using process mining techniques. Methods: We analy...
Article
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Background: Socially vulnerable populations were vastly affected by the COVID-19 pandemic. The pandemic significantly impacted Brazil, pressuring its healthcare system for several months, with high mortality rates, even among the youngest population. Cohort studies combining disease surveillance are essential for understanding virus circulation in...
Article
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After completion, oil wells often require intervention services to increase productivity, correct oil flow losses, and solve mechanical failures. These interventions, known as workovers, are made using oil rigs, an expensive and scarce resource. The workover rig scheduling problem (WRSP) comprises deciding which wells demanding workovers will be at...
Conference Paper
Full-text available
The planning and monitoring of the contracting processes of contractual instruments are necessary to execute effective operations. In large companies, the planning and monitoring of processes are supported by systems that aim to bring predictability to hiring, avoiding possible delays. This paper proposes predictive models capable of predicting the...
Article
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Background A vaccination campaign targeted adults in response to the pandemic in the City of Rio de Janeiro. Objective We aimed to evaluate the seroprevalence of SARS-CoV-2 antibodies and identify factors associated with seropositivity on vaccinated and unvaccinated residents. Methods We performed a seroepidemiologic survey in all residents of Pa...
Article
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This paper presents a novel technique to compute Lagrangian bounds for nonconvex mixed-integer quadratically constrained quadratic programming problems presenting a separable structure (i.e., a separable problems) such as those arising in deterministic equivalent representations of two-stage stochastic programming problems. In general, the nonconve...
Article
Purpose To compare categorical and continuous combinations of the standardized mortality ratio (SMR) and the standardized resource use (SRU) to evaluate ICU performance. Materials and methods We analysed data from adult patients admitted to 128 ICUs in Brazil and Uruguay (BR/UY) and 83 ICUs in The Netherlands between 2016 and 2018. SMR and SRU wer...
Article
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Background There is limited information on the inequity of access to vaccination in low-and-middle-income countries during the COVID-19 pandemic. Here, we described the progression of the Brazilian immunisation program for COVID-19, and the association of socioeconomic development with vaccination rates, considering the potential protective effect...
Article
Purpose The length of stay (LoS) is one of the most used metrics for resource use in Intensive Care Units (ICU). We propose a structured data-driven methodology to predict the ICU length of stay and the risk of prolonged stay, and its application in a large multicenter Brazilian ICU database. Methods Demographic data, comorbidities, complications,...
Article
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This paper addresses a parallel machine scheduling problem with non-anticipatory family setup times and batching, considering the task’s stochastic processing times and release dates. The problem arises from a real-life ship scheduling problem in the oil and gas industry. We developed an Iterated Greedy simheuristic with built-in Monte Carlo Simula...
Article
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Objectives To estimate the vaccine effectiveness after first and second dose of ChAdOx1 nCoV-19 against symptomatic COVID-19 and infection in a socially vulnerable community in Brazil when Gamma and Delta were the predominant variants circulating. Methods We conducted a test-negative study at the community “Complexo da Maré”, the largest group of...
Article
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Background Studies using Data Envelopment Analysis to benchmark Intensive Care Units (ICUs) are scarce. Previous studies have focused on comparing efficiency using only performance metrics, without accounting for resources. Hence, we aimed to perform a benchmarking analysis of ICUs using data envelopment analysis. Methods We performed a retrospect...
Preprint
Full-text available
We conducted a test-negative study design at the community “Complexo da Maré”, the largest group of favelas in Rio de Janeiro, Brazil, when Gamma and Delta were the predominant variants circulating. We estimated 42.4% (95% CI, 24.6, 56.0) protection against symptomatic COVID-19 after 21 days of one dose of ChAdOx1.
Article
Full-text available
Rigs are critical capital-intensive resources for oil and gas exploration and production operations, such as drilling, completion, and workover. The Rig Scheduling Problem (RSP) comprises deciding which rigs will serve each of the wells and when the operations must be performed. Several studies considering the theoretical and practical perspectives...
Article
PurposeClinical characteristics and management of COVID-19 patients have evolved during the pandemic, potentially changing their outcomes. We analyzed the associations of changes in mortality rates with clinical profiles and respiratory support strategies in COVID-19 critically ill patients.MethodsA multicenter cohort of RT-PCR-confirmed COVID-19 p...
Article
Full-text available
Background Tests are scarce resources, especially in low and middle-income countries, and the optimization of testing programs during a pandemic is critical for the effectiveness of the disease control. Hence, we aim to use the combination of symptoms to build a predictive model as a screening tool to identify people and areas with a higher risk of...
Article
Background Most low-income and middle-income countries (LMICs) have little or no data integrated into a national surveillance system to identify characteristics or outcomes of COVID-19 hospital admissions and the impact of the COVID-19 pandemic on their national health systems. We aimed to analyse characteristics of patients admitted to hospital wi...
Article
Objectives – The coronavirus disease 2019 (COVID-19) pandemic has highlighted inequalities in access to healthcare systems, increasing racial/ethnic disparities and worsening health outcomes in these populations. This study analysed the association between sociodemographic characteristics and COVID-19 in-hospital mortality in Brazil. Study design...
Article
In this paper, we address a variant of a batch scheduling problem with identical parallel machines and non-anticipatory family setup times to minimize the total weighted completion time. We developed an ILS and a GRASP matheuristics to solve the problem using a constructive heuristic and two MIP-based neighborhood searches, considering two batch sc...
Article
In this paper, we deal with a problem that arises from the oil industry with the need to schedule a pipe laying support vessel fleet responsible for connecting oil wells to production platforms. We model it as an identical parallel machine scheduling problem, considering a particular case where jobs are composed of intersecting sets of operations a...
Conference Paper
Full-text available
Diante da pandemia de COVID-19, muitos países adotaram medidas de contenção buscando desacelerar sua propagação. Entretanto, tendo em vista a diversidade de medidas aplicadas e as diferentes curvas de propagação da doença dos vários países, a análise da efetividade das medidas é extremamente complexa, embora relevante para subsidiar decisões de ges...
Preprint
In this paper, we address a variant of a batch scheduling problem with identical parallel machines and non-anticipatory family setup times to minimize the total weighted completion time. We developed an ILS and a GRASP matheuristics to solve the problem using a constructive heuristic and two MIP-based neighborhood searches, considering two batch sc...
Preprint
Full-text available
Background: Tests are scarce resources, especially in low and middle-income countries, and the optimization of testing programs during a pandemic is critical for the effectiveness of the disease control. Hence, we aim to use the combination of symptoms to build a regression model as a screening tool to identify people and areas with a higher risk o...
Article
Background Seasonal variation in stroke incidence remains controversial. Aims We aimed to describe the pattern of seasonality in hospitalizations for stroke in Brazil. Methods We evaluated age-adjusted hospitalization rates for stroke per month using data from the Brazilian Unified Healthcare System and median monthly temperature data obtained fr...
Article
Purpose Studies have shown that a small percentage of ICU patients have prolonged length of stay (LoS) and account for a large proportion of resource use. Therefore, the identification of prolonged stay patients can improve unit efficiency. In this study, we performed a systematic review and meta-analysis to understand the risk factors of ICU LoS....
Preprint
This paper presents a novel technique to solve two-stage stochastic programming models whose deterministic equivalent is represented by a noncon-vex mixed-integer quadratically constrained quadratic programming (MIQCQP) model. In general, the nonconvex nature of these models still poses a challenge for available solvers, which do not consistently p...
Article
Full-text available
OBJECTIVE: To estimate the reporting rates of coronavirus disease 2019 (COVID-19) cases for Brazil as a whole and states. METHODS: We estimated the actual number of COVID-19 cases using the reported number of deaths in Brazil and each state, and the expected case-fatality ratio from the World Health Organization. Brazil’s expected case-fatality rat...
Article
Purpose Characteristics of structure and process impact ICU performance and the outcomes of critically ill patients. We sought to identify organizational characteristics associated with efficient ICUs in low-resource settings. Materials and methods This is a secondary analysis of a multicenter cluster-randomized clinical trial in Brazil (CHECKLIST...
Article
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O número de casos confirmados da doença pelo coronavírus 2019 (COVID-19) é o dado mais importante para que se possa compreender a evolução dessa doença. Contudo, a rápida disseminação da pandemia e o pequeno número de testes realizados tornam difícil estimar o número real de casos e provocam subnotificação em diferentes países. A restrição dos test...
Article
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Objective: To analyse the measures adopted by countries that have shown control over the transmission of coronavirus disease 2019 (COVID-19) and how each curve of accumulated cases behaved after the implementation of those measures. Methods: The methodology adopted for this study comprises three phases: systemizing control measures adopted by di...
Article
A challenging problem for Emergency Department (ED) managers is determining the best allocation of the medical staff that is required to promptly attend patients in the face of increasing demand for emergency care, and the ensuing long patient waiting times. We propose a solution framework that supports physician staffing and scheduling in the ED,...
Chapter
Teaching hospitals must comply with current legislation, which recommends a minimum number of surgeries for the resident’s approval in the training program. Thus, we propose a mathematical-based methodology to find efficient solutions for planning and scheduling elective surgeries that comply with the legislation.
Chapter
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We apply process modeling and simulation to improve surgery planning, through the coordination of operation rooms and intensive care unit (ICU). A case study was carried out in a Brazilian hospital. With the proposed changes, we obtained a 39% reduction in surgery cancelations and a 61% decrease in preoperative length of stay.
Article
Background: Infections by multidrug-resistant Gram-negative (MDRGN) bacteria are among the greatest contemporary health concerns, especially in intensive care units (ICUs), and may be associated with increased hospitalization time, morbidity, costs, and mortality. Aim: The study aimed to predict carbapenem-resistant MDRGN acquisition in ICUs, to de...
Article
Full-text available
Uncertainty is a highly important aspect of maritime transportation. Unforeseen occurrences related to environmental conditions, poor weather, vessel reliability, or port congestion are frequent and have a non-negligible impact on the total time required for vessels to perform (un)loading operations at ports. We study a special case of maritime tra...
Article
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Purpose Appointment scheduling systems traditionally book patients at fixed intervals, without taking into account the complexity factors of the health system. This paper analyzes several appointment scheduling policies of the literature and proposes the most suitable to a bariatric surgery clinic, considering the following complexity factors: (i)...
Article
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We propose methods for improving the relaxations obtained by the normalized multiparametric disaggregation technique (NMDT). These relaxations constitute a key component for some methods for solving nonconvex mixed-integer quadratically constrained quadratic programming (MIQCQP) problems. It is shown that these relaxations can be more efficiently f...
Article
Full-text available
Background Stroke is the third major cause of death in the world and the second in Brazil. The purpose of this work was to assess the stroke-related hospitalization, in-hospital mortality, and case fatality rates under the Brazilian Unified Health System (SUS) from 2009 to 2016. Methods We evaluated the hospital admissions for stroke and their ass...
Data
List of attributes from SIHSUS database used in this work. (PDF)
Data
Population projection data obtained from the Brazilian Institute of Geography and Statistics for each year, age and sex. (PDF)
Data
Formulation and description of the indicators used during the study. (PDF)
Article
Full-text available
Purpose No-shows of patients to their scheduled appointments have a significant impact on healthcare systems, including lower clinical efficiency and higher costs. The purpose of this study was to investigate the factors associated with patient no-shows in a bariatric surgery clinic. Materials and Methods We performed a retrospective study of 13,2...
Chapter
In this work, we propose and apply a methodology for the management and optimization of clinical pathways using process mining. We adapt the Clinical Pathway Analysis Method (CPAM) by taking into consideration healthcare providers’ needs. We successfully applied the methodology in the sepsis treatment of a major Brazilian hospital. Using data extra...
Chapter
Long waiting lines are a frequent problem in hospitals’ Emergency Departments and can be critical to the patient’s health and experience. This study proposes a three-stage solution framework to address this issue: Process Identification, Process Optimization, and Process Simulation. In the first, we use descriptive statistics to understand the data...
Article
This paper addresses a real‐life rescheduling problem of a pipe‐laying support vessel (PLSV) fleet in charge of subsea oil well connections. The short‐term schedule of these vessels is subject to uncertainties inherent to its operations, resulting in ships idleness or delays in oil production. The objective of this study is to develop methods to su...
Article
Among the many challenges involved in efficient healthcare resource planning, the Patient Admission Scheduling Problem is of particular significance, impacting organizational decisions at all planning levels. The problem of scheduling patient admissions involves assigning patients to beds over a given time horizon so as to maximize treatment effici...
Article
Full-text available
We present deterministic and stochastic programming models for the workover rig problem, one of the most challenging problems in the oil industry. In the deterministic approach, an integer linear programming model is used to determine the rig fleet size and schedule needed to service wells while maximizing oil production and minimizing rig usage co...
Article
Full-text available
Background Sepsis is considered a major worldwide health burden, with high mortality and associated costs. Health indicators are essential to define strategies to improve the treatment of diseases, and the epidemiology information of sepsis in developing countries is scarce. Thus, the aim of this work is to assess trends in the incidence, lethality...
Data
The Canadian Institute for Health Information list of International Statistical Classification of Diseases and Related Health Problems Tenth Revision (ICD-10) codes used to define sepsis. (DOCX)
Data
ROC curves from multiple logistic regressions. (DOCX)
Data
Number of hospitals and cases per hospital group from the treatment efficiency matrix for sepsis. (DOCX)
Data
Process to get SIHSUS and CNES data from DATASUS. (DOCX)
Article
No-show appointments significantly impact the functioning of healthcare institutions, and much research has been performed to uncover and analyze the factors that influence no-show behavior. In spite of the growing body of literature on this issue, no synthesis of the state-of-the-art is presently available and no systematic literature review (SLR)...