Absenteeism prediction and labor force optimization in rail dispatcher scheduling

Thesis: M. Eng. in Logistics, Massachusetts Institute of Technology, Engineering Systems Division, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 61-62).Unplanned employee absences are estimated to account for a loss of 3% of scheduled labor hours. This can be costly in railroad dispatcher scheduling because every absence must be filled through overtime or a qualified extra dispatcher. One factor that complicates this problem is the uncertainty of unplanned employee absences. The ability to predict unplanned absences would facilitate effective scheduling of extra dispatchers and help reduce overtime costs. This thesis uses data from a railroad company over a four year period to examine company-wide factors thought to impact the number of unplanned absences among dispatchers. Using Poisson regression, we identify several factors that provide statistical evidence of influencing the number of unplanned absences. These factors are month, snowstorms, shift, and certain holidays. Despite these findings, the overall predictive capability of our regression model is very weak. Instead, we model the number of unplanned absences by shift as a Hadrom process with a Negative Binomial distribution and use Monte Carlo simulation to explore the impact on overtime costs of increasing the number of scheduled extra dispatchers and increasing the number of positions on which each employee is qualified to work. Our results show that increasing the number of extra dispatchers has a greater effect on reducing overtime, but the cost savings from reducing overtime expenses are not enough to offset the additional labor costs of having more employees on staff. Our results provide insight regarding the relationship among extra staff, higher levels of qualification among employees, and the willingness to use overtime in handling unplanned absences.by Taylor Jensen and Qi Sun.M. Eng. in Logistic

Minority Entrepreneurs and Fast Failure

Minority businesses now make up more than a quarter of all U.S. businesses; yet, due to discriminatory lending practices, cultural aversions to debt, and limited access to capital, these businesses continue to have higher failure rates. At the same time, m inority entrepreneurs are more likely to rely on informal lending and less likely to turn to bankruptcy for relief of debt. Doing so slows down failure for minority entrepreneurs — contra Silicon Valley’s new mantra, “fail fast” — and diminishes the minority entrepreneur’s ability to efficiently reallocate resources towards more productive ventures. In this essay, I distinguish the minority entrepreneurial fast failure decision from that of the majority entrepreneur and propose both private orderin g and regulat ory solutions that could help minority entrepreneurs fail faster. I begin by generally modeling the fast failure decision for the majority entrepreneur, highlighting the social costs of failing fast, and describing how formal lending and bankruptcy affect this model. I then explain how this model is distorted for minority entrepreneurs by discriminatory lending practices, cultural aversions to debt, and access to legal counsel. I conclude by suggesting, and critically assessing, proposals that could diminish these distortions, including peer - to - peer (P2P) lending platforms, mandatory educational programs, color - blind and big data loan and credit assessments, and minority loan subsidie

Minority Entrepreneurs and Fast Failure

Minority businesses now make up more than a quarter of all U.S. businesses; yet, due to discriminatory lending practices, cultural aversions to debt, and limited access to capital, these businesses continue to have higher failure rates. At the same time, m inority entrepreneurs are more likely to rely on informal lending and less likely to turn to bankruptcy for relief of debt. Doing so slows down failure for minority entrepreneurs — contra Silicon Valley’s new mantra, “fail fast” — and diminishes the minority entrepreneur’s ability to efficiently reallocate resources towards more productive ventures. In this essay, I distinguish the minority entrepreneurial fast failure decision from that of the majority entrepreneur and propose both private orderin g and regulat ory solutions that could help minority entrepreneurs fail faster. I begin by generally modeling the fast failure decision for the majority entrepreneur, highlighting the social costs of failing fast, and describing how formal lending and bankruptcy affect this model. I then explain how this model is distorted for minority entrepreneurs by discriminatory lending practices, cultural aversions to debt, and access to legal counsel. I conclude by suggesting, and critically assessing, proposals that could diminish these distortions, including peer - to - peer (P2P) lending platforms, mandatory educational programs, color - blind and big data loan and credit assessments, and minority loan subsidie

Tosio Kato (1917–1999)

Tosio Kato was born August 25, 1917, in Kanuma City, Tochigi-ken, Japan. His early training was in physics. He obtained a B.S. in 1941 and the degree of Doctor of Science in 1951, both at the University of Tokyo. Between these events he published papers on a variety of subjects, including pair creation by gamma rays, motion of an object in a fluid, and results on spectral theory of operators arising in quantum mechanics. His dissertation was entitled “On the convergence of the perturbation method”. Kato was appointed assistant professor of physics at the University of Tokyo in 1951 and was promoted to professor of physics in 1958. During this time he visited the University of California at Berkeley in 1954–55, New York University in 1955, the National Bureau of Standards in 1955–56, and Berkeley and the California Institute of Technology in 1957–58. He was appointed professor of mathematics at Berkeley in 1962 and taught there until his retirement in 1988. He supervised twenty-one Ph.D. students at Berkeley and three at the University of Tokyo. Kato published over 160 papers and 6 monographs, including his famous book Perturbation Theory for Linear Operators [K66b]. Recognition for his important work included the Norbert Wiener Prize in Applied Mathematics, awarded in 1980 by the AMS and the Society for Industrial and Applied Mathematics. He was particularly well known for his work on Schrödinger equations of nonrelativistic quantum mechanics and his work on the Navier-Stokes and Euler equations of classical fluid mechanics. His activity in the latter area remained at a high level well past retirement and continued until his death on October 2, 1999

Singular Self-dual Zollfrei Metrics and Twistor Correspondence

We construct examples of singular self-dual Zollfrei metrics explicitly, by patching a pair of Petean's self-dual split-signature metrics. We prove that there is a natural one-to-one correspondence between these singular metrics and a certain set of embeddings of $RP^3$ to $CP^3$ which has one singular point. This embedding corresponds to an odd function on $R$ that is rapidly decreasing and pure imaginary valued. The one-to-one correspondence is explicitly given by using the Radon transform.Comment: 25page

Rolling of asymmetric disks on an inclined plane

In a recent papers, Turner and Turner (2010 {\em Am. J. Phys.} {\bf 78} 905-7) and Jensen (2011 {\em Eur. J. Phys.} {\bf 32} 389-397) analysed the motion of asymmetric rolling rigid bodies on a horizontal plane. These papers addressed the common misconception that the instantaneous point of contact of the rolling body with the plane can be used to evaluate the angular momentum $\mathbf L$ and the torque $\boldsymbol\tau$ in the equation of motion $d\mathbf L/dt = \boldsymbol\tau$. To obtain the correct equation of motion, the "phantom torque" or various rules that depend on the motion of the point about which $\mathbf L$ and $\boldsymbol\tau$ are evaluated were discussed. In this paper, I consider asymmetric disks rolling down an inclined plane and describe the most basic way of obtaining the correct equation of motion; that is, to choose the point about which $\mathbf L$ and $\boldsymbol\tau$ are evaluated that is stationary in an inertial frame

A typology of Twitter interactions to effectively analyse engagement and evidence research impact

In this article, we explore how Twitter engagements can demonstrate different types and extents of research impact. It can be simple to demonstrate social media activity through quantitative metrics; however, it is more complex and challenging to evidence the impact that this activity can have. We start by exploring definitions of impact and public engagement. We then present an analysis of a selection of Twitter interactions from the @BarbieReports ArtActivistBarbie account, creating a typology consisting of four categories: change tweet, cheer tweet, comment tweet and conversation tweet. These categories demonstrate different types of engagement and impact, enabling an understanding of how impact can be claimed from contextual social media analysis. This typology can be used by researchers to analyse tweet interactions in three ways: (1) as indicators of two-way engagement; (2) as evidence of impact; and (3) as part of a wider story of change and influence. The typology presented in this article is intended as a foundation which people can adapt and add to, making it an evolving tool for social media impact analysis

Osmotically driven flows in microchannels separated by a semipermeable membrane

We perform experimental investigations of osmotically driven flows in artificial microchannels by studying the dynamics and structure of the front of a sugar solution traveling in 200 um wide and 50-200 um deep microchannels. We find that the sugar front travels with constant speed, and that this speed is proportional to the concentration of the sugar solution and inversely proportional to the depth of the channel. We propose a theoretical model, which, in the limit of low axial flow resistance, predicts that the sugar front indeed should travel with a constant velocity. The model also predicts an inverse relationship between the depth of the channel and the speed and a linear relation between the sugar concentration and the speed. We thus find good agreement between the experimental results and the predictions of the model. Our motivation for studying osmotically driven flows is that they are believed to be responsible for the translocation of sugar in plants through the phloem sieve element cells. Also, we suggest that osmotic elements can act as integrated pumps with no movable parts in lab-on-a-chip systems.Comment: 7 Pages, submitted to Lab-on-a-chip on October 24th, 200