Essays on Issues in New Product Introduction: Product Rollovers, Information Provision, and Return Policies

In this dissertation we study several key issues faced by firms while introducing new products to market. The first essay looks at product rollovers: introduction of a new product generation while phasing out the old one. We study the strategic decision of dual vs. single roll jointly with operational decisions of inventory and pricing during this transitional period. Our results confirm previous findings and uncover the role and interaction of several parameters that were not examined before. In the second essay, we investigate the role of information provision and return policies in the consumer purchasing behavior and on the overall market outcome. We build a novel model of consumer learning, and we attain significant analytical findings without making any distributional assumptions. We then fully study the joint optimization problem analytically under uniform valuations. In the third essay, we study competition in the framework described in the second essay and we identify the potential Nash equilibria and associated conditions. Our findings demonstrate the effect of competition on return policy and information provision decisions and provide insight on some real-life observations

Optimal Supply & Demand Balance In Service Environments

We study service environments that can be modeled as stochastic finite-capacity double-ended queues, where supply and demand arrive in independent Poisson processes to be instantly paired-off. In the case where throughput (output rate) is not a significant metric of system performance (as typically studied in the literature), we derive analytical results to gain managerial insights. We find that the operational decision on optimal supply/demand balance and the strategic decision on how to achieve that optimal balance can be decoupled and stratified. With the purpose of providing a managerial guide, we identify conditions for when to manipulate demand rather than supply, and vice versa. For the first time in the literature, we study throughput considerations in this context, and we analytically characterize the optimal strategy. Specifically, we show that it is optimal to manipulate either demand, or supply (and not both), and that the optimal system balance and the strategy on how to achieve it are strongly tied. Our findings can shed light on the managerial decision making process in these environments, and they can be used to revisit any governing strategies dictating management of demand (or supply) as a first course of action

The frequency of Duchenne muscular dystrophy/Becker muscular dystrophy and Pompe disease in children with isolated transaminase elevation: results from the observational VICTORIA study

IntroductionElevated transaminases and/or creatine phosphokinase can indicate underlying muscle disease. Therefore, this study aims to determine the frequency of Duchenne muscular dystrophy/Becker muscular dystrophy (DMD/BMD) in male children and Pompe disease (PD) in male and female children with isolated hypertransaminasemia.MethodsThis multi-center, prospective study enrolled patients aged 3–216 months with serum alanine transaminase (ALT) and/or aspartate transaminase (AST) levels >2× the upper limit of normal (ULN) for ≥3 months. Patients with a known history of liver or muscle disease or physical examination findings suggestive of liver disease were excluded. Patients were screened for creatinine phosphokinase (CPK) levels, and molecular genetic tests for DMD/BMD in male patients and enzyme analysis for PD in male and female patients with elevated CPK levels were performed. Genetic analyses confirmed PD. Demographic, clinical, and laboratory characteristics of the patients were analyzed.ResultsOverall, 589 patients [66.8% male, mean age of 63.4 months (standard deviation: 60.5)] were included. In total, 251 patients (188 male and 63 female) had CPK levels above the ULN. Of the patients assessed, 47% (85/182) of male patients were diagnosed with DMD/BMD and 1% (3/228) of male and female patients were diagnosed with PD. The median ALT, AST, and CPK levels were statistically significantly higher, and the questioned neurological symptoms and previously unnoticed examination findings were more common in DMD/BMD patients than those without DMD/BMD or PD (p < 0.001).DiscussionQuestioning neurological symptoms, conducting a complete physical examination, and testing for CPK levels in patients with isolated hypertransaminasemia will prevent costly and time-consuming investigations for liver diseases and will lead to the diagnosis of occult neuromuscular diseases. Trial RegistrationClinicaltrials.gov NCT04120168

Troubleshooting with Questions and Conditional Costs

Abstract. The basic decision-theoretic troubleshooting task is described in this paper. For questions, a new question efficiency measure is defined for direct comparison to actions, and an extended two-step lookahead procedure is suggested. For conditional action costs, matrices of cost effects are introduced for a generic cost mechanism, and an approximate algorithm is developed. In both, the main approach is to adjust efficiencies myopically and to perform a greedy search based on these. Performances of these approaches are tested through empirical studies and compared to other methods from the literature.

Evaluation of fatal diving accidents in Turkey

In any kind of diving there is a risk of accidents, as the move from the topside environment to underwater can affect a diver's physiological and psychological condition. It is important to investigate dive accidents to clarify the causative factors and determine preventive measures