A Data-Driven Framework for Decision Making Under Uncertainty: Integrating Markov Decision Processes, Hidden Markov Models and Predictive Modeling

The problem of decision making under uncertainty can be broken down into two parts. First, how do we learn about the world? This involves the problem of modeling the system and its uncertainty. Secondly, given what we currently know about the world, how should we decide what to do, taking into account uncertainty of future events and observations that may change our conclusions. Many systems evolve over time and often the next state of the system is not known with certainty, often modeled as a probability distribution over system states. Dealing with such systems especially when we can make a decision at different points in time is difficult due to uncertainty. Making optimal decisions requires understanding the system including its characteristics, how it evolves and changes over time, and how taken actions affect the system. There are multiple dimensions to this problem, and each dimension might require its own specific method. We need a descriptive method that can summarize the system and its evolution, a predictive model that is used to extract information from the complicated systems and also a prescriptive model that works as the main decision model and incorporates the effects of actions. In this thesis I consider Partially Observable Markov Decision Process (POMDP) as the main decision-making/prescriptive model, Hidden Markov Models (HMM) as the descriptive model of system evolution, and a predictive model to create observations for the POMDP. In this research, I develop a framework by combining these methods and demonstrate its use with two applications. I apply the proposed framework to the problem of diabetes screening and also resource allocation under uncertainty for emergency management. I demonstrate using simulation that implementing the proposed policy will bring about significant improvements in both systems compared to the existing policies

Five Years Pathological Evaluation of Corneal Regrafts: A Study from Southern Iran

Purpose. Corneal regrafts sometimes needed to restore the transparency after graft failure. The aim of the study is five years epidemiologic and histopathological evaluation of corneal regrafts. Methods. In this cross-sectional study, all corneal regrafts during 5 years (2012–2016) were assessed in the Khalili Ophthalmology Center at Shiraz city. Demographic data including age, area of residence, primary disease, type of graft, cause of regraft, interval between primary and subsequent grafts (IPSG), associated eye diseases or surgeries, and systemic diseases were recorded. Also, microscopic findings of corneas were reviewed. Results. Among a total of 1190 corneal grafts, 76 of them (6.38%) were regrafts. The most common type of grafting was penetrating keratoplasty (PK). The shortest IPSG was observed in fungal keratitis. Main causes of graft failure were endothelial dysfunction, infection, immunologic rejection, technical problems, and recurrence of primary disease, respectively. The most common histopathological finding in failed grafts was severe endothelial cell loss (89.8%). Also, more than half and one-third of cases had Descemet membrane changes and stromal ingrowth, respectively. Conclusion. Endothelial cell loss was the major cause of failure in our study. Also, recurrence rate in infective cases, especially fungal keratitis, was very high. Considerable presence of histopathological changes such as doubling of Descemet membrane and retrocorneal fibrous ingrowth need further investigations. Perhaps, modification in techniques of corneal grafting and assessment of donor tissue and recipient bed along with any need for longer medical treatment are the basis for future studies in order to increase graft survival

Development of an ESCO Risk Assessment Model as a Decision-Making Tool for the Energy Savings Certificates Market Regulator: A Case Study

This article is focused on developing an Energy Service Company (ESCO) risk assessment model for use by energy savings certificates (ESC) market regulators. This model enables market regulators to determine the appropriate point in time for ESCOs to sell their certificates with the aim of minimizing risk as well as maximizing economic gain yet remain motivated for reducing the cost of energy efficiency technologies. To this end, the interactions between an ESCO and other parties (such as suppliers) in the market in addition to the principles of the energy efficiency performance contract are taken into consideration. Then, appropriate probability distributions have been fitted to the stochastic variables to be applied in the Net Present Value (NPV) function, based on sampled company data. A case study considers a one MW Organic Rankine Cycle (ORC) implementation in Iran’s petrochemical industry. The finding of this study shows if the ESCO is allowed to sell the certificates during the first seven years as well reduce 30% of the investment cost, the expected Net Present Value over Investment Cost (NPV/I) savings will cover more than one cycle

Prevention of Atrioventricular Block During Radiofrequency Ablation by Pace Mapping of Koch’s Triangle

Background: Complete atrioventricular block (AV block) is a serious complication of slow pathway ablation therapy in the treatment of atrioventricular nodal re-entrant tachycardia (AVNRT). The present study was aimed at determining whether the electroanatomical pace mapping of Koch’s triangle could significantly improve the safety, efficiency, and efficacy of selective slow pathway ablation in the treatment of AVNRT. Methods: A total number of 124 patients were selected to be studied consecutively for radiofrequency (RF) ablation therapy in the treatment of AVNRT. The subjects were divided into two groups: one, designated Group 1, to serve as the control group, and the other, designated Group 2, to serve as the study group. Conventional fluoroscopic slow pathway ablation was performed on the Group 1 subjects (n=66), with the Group 2 subjects receiving slow pathway ablation therapy guided by pace mapping of Koch’s triangle. The slow pathway ablation in Group 2 (n=58) was performed with regard to the pace mapping data obtained on the basis of the St-H interval in the anteroseptal (AS), midseptal (MS), and posteroseptal (PS) regions of Koch’s triangle. The anterograde fast pathway (AFP) location was determined based on the shortest St-H interval obtained by stimulating the anteroseptal (AS), midseptal (MS), and posteroseptal (PS) aspects of Koch’s triangle. Results: In the Group 2 subjects, AFP location was AS in 50 (86.2%) of the cases, MS in 7 (12%) of the cases, and PS in 1 case (1.7%). One patient with posteroseptal AFP was administered retrograde fast pathway ablation therapy. One patient in the control group (Group 1), representing 1.5% of the group, developed persistent AV block in the course of the treatment, but none of the subjects in the study group (Group 2) developed any complications. Conclusion: It was concluded that an atypical fast pathway location is conducive to the development of atrioventricular block in the ablation therapy in AVNRT, with pace mapping of Koch’s triangle having the capacity to eliminate the risk of any such complication developing. It follows that it helps to identify the AFP location before ablation therapy is administered in AVNRT, thereby improving the safety of the treatment

Serological surveillance of bluetongue virus in cattle in central Iran

The aim of this study was to evaluate the seroprevalence and distribution of antibodies to the bluetongue virus (BTV) among dairy Holstein cattle of central Iran. From September 2010 to August 2011, 892 blood samples from Holstein dairy cattle were collected from healthy animals. Blood samples were divided according to type of farm (industrial and non-industrial), season (warm and cold), location (North, South, East, and West), cattle production groups (calf, heifer, dairy and dry) and age groups (under 6 months, 6 months-2 years and over 2 years). The sera were screened using a commercially competitive enzyme-linked immunosorbent assay (c-ELISA) kit. Twenty-four sera (2.69 %) were found to be positive for BTV. Bluetongue virus seroprevalence was significantly higher (χ2 = 8.29, df = 3, p < 0.05) in cattle in southern locations as compared to those in other locations. Older animals (> 2 years) showed a relatively higher seroprevalence, but the difference was not statistically significant (p = 0.06). No statistically significant difference in BTV seroprevalence was noted between farming systems, seasons and cattle production groups (p > 0.05). The results demonstrate that the seroprevalence of BTV is low in cattle from the Isfahan province, central Iran. Further studies are needed to determine the serotypes and vectors of BTV in the central region of Iran