The hiring problem and its algorithmic applications

The hiring problem is a simple model for on-line decision-making under uncertainty, recently introduced in the literature. Despite some related work dates back to 2000, the name and the first extensive studies were written in 2007 and 2008. The problem has been introduced explicitly first by Broder et al. in 2008 as a natural extension to the well-known secretary problem. Soon afterwards, Archibald and Martínez in 2009 introduced a discrete (combinatorial) model of the hiring problem, where the candidates seen so far could be ranked from best to worst without the need to know their absolute quality scores. This thesis introduces an extensive study for the hiring problem under the formulation given by Archibald and Martínez, explores the connections with other on-line selection processes in the literature, and develops one interesting application of our results to the field of data streaming algorithms. In the hiring problem we are interested in the design and analysis of hiring strategies. We study in detail two hiring strategies, namely hiring above the median and hiring above the m-th best. Hiring above the median hires the first interviewed candidate then any coming candidate is hired if and only if his relative rank is better than the median rank of the already hired staff, and others are discarded. Hiring above the m-th best hires the first m candidates in the sequence, then any coming candidate is hired if and only if his relative rank is larger than the m-th best among all hired candidates, and others are discarded. For both strategies, we were able to obtain exact and asymptotic distributional results for various quantities of interest (which we call hiring parameters). Our fundamental parameter is the number of hired candidates, together with other parameters like waiting time, index of last hired candidate and distance between the last two hirings give us a clear picture of the hiring rate or the dynamics of the hiring process for the particular strategy under study. There is another group of parameters like score of last hired candidate, score of best discarded candidate and number of replacements that give us an indicator of the quality of the hired staff. For the strategy hiring above the median, we study more quantities like number of hired candidates conditioned on the first one and probability that the candidate with score q is getting hired. We study the selection rule 1/2-percentile rule introduced by Krieger et al., in 2007, and the seating plan (1/2,1) of the Chinese restaurant process (CRP) introduced by Pitman, which are very similar to hiring above the median. The connections between hiring above the m-th best and the notion of m-records, and also the seating plan (0,m) of the CRP are investigated here. We report preliminary results for the number of hired candidates for a generalization of hiring above the median; called hiring above the alpha-quantile (of the hired staff). The explicit results for the number of hired candidates enable us to design an estimator, called RECORDINALITY, for the number of distinct elements in a large sequence of data which may contain repetitions; this problem is known in the literature as cardinality estimation problem. We show that another hiring parameter, the score of best discarded candidate, can also be used to design a new cardinality estimator, which we call DISCARDINALITY. Most of the results presented here have been published or submitted for publication. The thesis leaves some open questions, as well as many promising ideas for future work. One interesting question is how to compare two different strategies; that requires a suitable definition of the notion of optimality, which is still missing in the context of the hiring problem. We are also interested in investigating other variants of the problem like probabilistic hiring strategies, that is when the hiring criteria is not deterministic, unlike all the studied strategies

The Hiring Problem: An Analytic and Experimental Study

When a small, start-up company intends to grow, it has to hire employees. Because the company requires high quality staff, the employer has to interview a lot of candidates and thus, she may take long time to collect the required staff. Of course, there is another important demand which is the time taken by the hiring process which is required to be as short as possible or the company’s rate of growth which is required to go as quickly as possible. So, the company has two main demands and needs to achieve balance between them. This is an intuitive idea about hiring from which this case study problem bears its name. The hiring problem is just an abstract model of the real hiring process. It is clear that the hiring problem will not cover every aspect of real hiring processes but it investigates some important parameters under a simplified mathematical model. On the other hand, the statement of the problem - as we will see- will give a general mathematical question with many possible applications; it is relevant in many instances where one must make decisions under uncertainty

Sensitivity analysis of sensors in a hydraulic condition monitoring system using CNN models

Condition monitoring (CM) is a useful application in industry 4.0, where the machine’s health is controlled by computational intelligence methods. Data-driven models, especially from the field of deep learning, are efficient solutions for the analysis of time series sensor data due to their ability to recognize patterns in high dimensional data and to track the temporal evolution of the signal. Despite the excellent performance of deep learning models in many applications, additional requirements regarding the interpretability of machine learning models are getting relevant. In this work, we present a study on the sensitivity of sensors in a deep learning based CM system providing high-level information about the relevance of the sensors. Several convolutional neural networks (CNN) have been constructed from a multisensory dataset for the prediction of different degradation states in a hydraulic system. An attribution analysis of the input features provided insights about the contribution of each sensor in the prediction of the classifier. Relevant sensors were identified, and CNN models built on the selected sensors resulted equal in prediction quality to the original models. The information about the relevance of sensors is useful for the system’s design to decide timely on the required sensorsPeer ReviewedPostprint (published version

Object-based classification of QuickBird image and low point density LIDAR for tropical trees and shrubs mapping

This paper assessed the performance of object-based supervised support vector machine (SVM) and rule-based techniques in classifying tropical vegetated floodplain using 0.6m QuickBird image and LIDAR dataset of 1.4 points per square meter (PPSM). This is particularly significant in hydraulic modelling in which vegetation roughness is a big uncertainty and largely relies on land cover classification. The supervised classification resulted in 79.40% overall accuracy whilst the results improved by 8% with rule-based classification. 40 sample plots of trees and shrubs were measured to be compared to obtain the best classification results. The results showed a linear relationship between tree diameters and NDVI with a high Pearson correlation of 0.76 and coefficient of determination (r2) of 0.58. The canopy areas of shrubs were found to be representative spatially with an even higher Pearson correlation of 0.98 and r2 of 0.95. The study concluded that the fusion of QuickBird image and low point density LIDAR in rule-based classification together with field data were useful in quantifying tropical trees and shrubs

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

The Hiring Problem: An Analytic and Experimental Study

When a small, start-up company intends to grow, it has to hire employees. Because the company requires high quality staff, the employer has to interview a lot of candidates and thus, she may take long time to collect the required staff. Of course, there is another important demand which is the time taken by the hiring process which is required to be as short as possible or the company’s rate of growth which is required to go as quickly as possible. So, the company has two main demands and needs to achieve balance between them. This is an intuitive idea about hiring from which this case study problem bears its name. The hiring problem is just an abstract model of the real hiring process. It is clear that the hiring problem will not cover every aspect of real hiring processes but it investigates some important parameters under a simplified mathematical model. On the other hand, the statement of the problem - as we will see- will give a general mathematical question with many possible applications; it is relevant in many instances where one must make decisions under uncertainty

The Hiring Problem: An Analytic and Experimental Study

When a small, start-up company intends to grow, it has to hire employees. Because the company requires high quality staff, the employer has to interview a lot of candidates and thus, she may take long time to collect the required staff. Of course, there is another important demand which is the time taken by the hiring process which is required to be as short as possible or the company’s rate of growth which is required to go as quickly as possible. So, the company has two main demands and needs to achieve balance between them. This is an intuitive idea about hiring from which this case study problem bears its name. The hiring problem is just an abstract model of the real hiring process. It is clear that the hiring problem will not cover every aspect of real hiring processes but it investigates some important parameters under a simplified mathematical model. On the other hand, the statement of the problem - as we will see- will give a general mathematical question with many possible applications; it is relevant in many instances where one must make decisions under uncertainty

Contributions to the law of succession in Ancient Egypt

This Dissertation dealt with the law of succession in Ancient Egypt, and is composed of two parts. The second part is a Catalogue. In this part, I have collected the legislative texts and other sources and designated them as the prime evidence of this study. These documents are arranged in chronologic¬al order. They are 11 tomb inscriptions, 12 papyri, 10 stelae, 20 ostraca, one statue inscription, two clay tablets, and one ceramic bowl. In addition to the demotic Papyrus Mattha, which dates back to c. 250 BCE. It is one of the prime sources of intestate succession. The first part of my work consists of three chapters: the first deals with the definition of the types of property bequeathed in pharaonic Egypt. I discussed the Egyptian terminology for property, in its definition as inheritance. After that I looked at the properties passed from the testator to his heir; these can be movables or immovables. Egyptologists affirm that the Egyptians could bequeath immovables like land and architectural structures as well as movables like pieces of furniture, clothes, tools, grains, etc. Yet no Egyptologist has engaged in an earnest endeavor to organize these items into either category. So one of the purposes of this chapter was to give an account of the items of property. In the second chapter, I studied the elements and means of succession. First, I shed some light on the family members and determined the role of each in the inheritance process. Then I examined the systems of succession law developed in pharaonic times: there were the customary intestate succession and the testate succession (by way of testamentary disposition). I explored how inheritance was divided among family members at the different stages of pharaonic history. The third chapter of my work deals with litigation and disinheritance and consisted of three sections. The first concerned the statutory bodies processing with inheritance matters and their tasks when quarrels flare-up between the heirs; that is besides the legal proceedings taken by the testator, heirs, and trustee in the succession process. The second section provided an analysis of prominent examples of disputes over inheritance across time. Finally, the third section studied the concept of disinheritance in pharaonic Egypt and identified the causes and the factors that made the testator deprived his legitimate heirs of inheritance