Comparing Elevator Strategies for a Parking Lot

In this paper, we compare elevator strategies for a parking garage. It is assumed that the parking garage has several floors and there is an elevator which can stop on each floor. We begin by considering 4 strategies detailed in page 23. For each strategy, we loop the program 100 times, and get 100 mean values for wait times. Welch\u27s test confirms highly significant differences among the 4 strategies. Repeating the analysis multiple times we see that the best of the 4 strategies is strategy 2, which places the elevator on floor 2 (the median floor) after use

Queues, Planes and Games: Algorithms for Scheduling Passengers, and Decision Making in Stackelberg Games

In this dissertation, I present three theoretical results with real-world applications related to scheduling and distributionally-robust games, important fields in discrete optimization, and computer science. The first chapter provides simple, technology-free interventions to manage elevator queues in high-rise buildings when passenger demand far exceeds the capacity of the elevator system. The problem was motivated by the need to manage passengers safely in light of reduced elevator capacities during the COVID-19 pandemic. We use mathematical modeling, epidemiological expertise, and simulation to design and evaluate our algorithmic solutions. The key idea is to explicitly or implicitly group passengers that are going to the same floor into the same elevator as much as possible, substantiated theoretically using a technique from queuing theory known as stability analysis. This chapter is joint work with Charles Branas, Adam Elmachtoub, Clifford Stein, and Yeqing Zhou, directly in collaboration with the New York City Mayor’s Office of the Chief Technology Officer and the Department of Citywide Administrative Services. The second chapter proposes new algorithms for recomputing passenger itineraries for airlines during major disruptions when carefully planned schedules are thrown into disarray. An airline network is a massive temporal graph, often with tight regulatory and operational constraints. When disruptions propagate through an airline network, the objective is to \textit{recover} within a given time frame from a disruption, meaning we replan schedules affected by the disruption such that the new schedules have to match the originally planned schedules after the time frame. We aim to solve the large-scale airline recovery problem with quick, user-independent, consistent, and near-optimal algorithms. We provide new algorithms to solve the passenger recovery problem, given recovered flight and crew solutions. We build a preprocessing step and construct an Integer Program as well as a network-based approach based on solving multiple-label shortest path problems. Experiments show the tractability of our proposed algorithms on airline data sets with heavy flight disruptions. This chapter is joint work with Clifford Stein, stemming from an internship and collaboration with the Machine Learning team (Artificial Intelligence organization) of GE Global Research, Niskayuna, New York. The third chapter is about computing distributionally-robust strategies for a popular game theory model called Stackelberg games, where one player, called the leader, is able to commit to a strategy first, assuming the other player(s), called follower(s) would best respond to the strategy. In many of the real-world applications of Stackelberg games, parameters such as payoffs of the follower(s) are not known with certainty. Distributionally-robust optimization allows a distribution over possible model parameters, where this distribution comes from a set of possible distributions. The goal for the leader is to maximize their expected utility with respect to the worst-case distribution from the set. We initiate the study of distributionally-robust models for Stackelberg games, show that a distributionally-robust Stackelberg equilibrium always exists across a wide array of uncertainty models, and provide tractable algorithms for some general settings with experimental results. This chapter is joint work with Christian Kroer

Supply Chain and Service Operations with Demand-Side Flexibility

In this thesis, we consider improving supply chain and service systems through demand-side management. In Chapters 1 and 2, we focus on a new notion of flexibility that has emerged in e-commerce called consumer flexibility. Motivated by the fact that some customers may willingly provide flexibility on which product or service they receive in exchange for a reward, firms can design flexible options to leverage this consumer flexibility for significant benefit in their operations. In Chapter 1, we consider the context of online retailing where consumer flexibility can be realized through opaque selling, where some specific attributes of the products are not revealed to the customer until after purchase. In Chapter 2, we focus on the context of online booking systems for scheduled services where consumer flexibility can be realized through large time windows. The main findings are on the power of limited flexibility using simple flexible options with just a small fraction of customers willing to be flexible. In Chapter 3, we study the issue of congested elevator queuing systems due to the requirement of social distancing during a pandemic. We propose simple interventions for safely managing the elevator queues, which require no programming of the elevator system and only manage passenger behaviors. The key idea is to explicitly or implicitly group passengers going to the same or nearby floor into the same elevator as much as possible. Simulations and stability analysis show that our proposed interventions significantly reduce queue length and wait time

AC vs. DC distribution efficiency:Are we on the right path?

The concept of DC power distribution has gained interest within the research community in the past years, especially due to the rapid prevalence of solar PVs as a tool for distributed generation in DC microgrids. Various efficiency analyses have been presented for the DC distribution paradigm, in comparison to the AC counterpart, considering a variety of scenarios. However, even after a number of such comparative efficiency studies, there seems to be a disparity in the results of research efforts, wherein a definite verdict is still unavailable. Is DC distribution a more efficient choice as compared to the conventional AC system? A final verdict is absent primarily due to conflicting results. In this regard, system modeling and the assumptions made in different studies play a significant role in affecting the results of the study. The current paper is an attempt to critically observe the modeling and assumptions used in the efficiency studies related to the DC distribution system. Several research efforts are analyzed for their approach toward the system upon which they have performed efficiency studies. Subsequently, the paper proposes a model that may alleviate the shortcomings in earlier research efforts and be able to give a definite verdict regarding the comparative efficiency of DC and AC networks for residential power distribution

The Second Conference on Lunar Bases and Space Activities of the 21st Century, volume 1

These papers comprise a peer-review selection of presentations by authors from NASA, LPI industry, and academia at the Second Conference (April 1988) on Lunar Bases and Space Activities of the 21st Century, sponsored by the NASA Office of Exploration and the Lunar Planetary Institute. These papers go into more technical depth than did those published from the first NASA-sponsored symposium on the topic, held in 1984. Session topics covered by this volume include (1) design and operation of transportation systems to, in orbit around, and on the Moon, (2) lunar base site selection, (3) design, architecture, construction, and operation of lunar bases and human habitats, and (4) lunar-based scientific research and experimentation in astronomy, exobiology, and lunar geology

Time for Reactive System Modeling

Reactive systems interact with their environment by reading inputs and computing and feeding back outputs in reactive cycles that are also called ticks. Often they are safety critical systems and are increasingly modeled with highlevel modeling tools. The concepts of the corresponding modeling languages are typically aimed to facilitate formal reasoning about program constructiveness to guarantee deterministic output and are explicitly abstracted from execution time aspects. Nevertheless, the worst-case execution time of a tick can be a crucial value, where exceedance can lead to lost inputs or tardy reaction to critical events. This thesis proposes a general approach to interactive timing analysis, which enables the feedback of detailed timing values directly in the model representation to support timing aware modeling. The concept is based on a generic timing interface that enables the exchangeability of the modeling as well as the timing analysis tool for the flexible implementation of varying tool chains. The proposed timing analysis approach includes visual highlighting and modeling pragmatics features to guide the user to timing hotspots for timing related model revisions

Underground mining of aggregates. Main report

This report examines the economic feasibility of underground mining for crushed rock aggregates in the UK, but particularly in the London, South East and East of England regions (the South East area of England). These regions import substantial volumes of crushed rock, primarily from the East Midlands and South West regions, requiring relatively long transport distances to market for this bulk commodity. A key part of the research was to determine whether or not aggregate could be produced and delivered to a local market from an underground aggregates operation at a cost comparable with that for production and transport of the commodity from traditional surface quarries located further afield. In essence the investigation asked – could the reduced transport costs compensate for the higher production costs underground so that underground crushed rock aggregates producers can compete with the established Leicestershire and Somerset surface quarries exporting to the South East? Work Programme The research effort involved establishing and verifying cost models for aggregates production, stone processing (sizing and sorting), haulage of product to market, environmental impact mitigation, health and safety, decommissioning and restoration. Another major element of the work was the re-examination of the BGS exploratory borehole and geophysical databases to identify potential areas of crushed rock aggregates resource at depth in the South East area of England. Land use pressure is typically higher in this area of England than elsewhere so another major part of the research was the identification of potential concurrent uses of land around the surface facilities of underground aggregates mines. The value, development costs for specific developments and determination of yields expected, from these uses were estimated. These were also used to investigate potential economic benefits associated with after uses of remediated surface land above potential underground aggregates mines and also for the new underground space that would be created. Key technical issues such as subsidence within relatively heavily populated areas of the South East area of England were also addressed. Economic Results The discounted cost of aggregate delivered at a discount rate of 10% was the metric used to appraise the options. This is the price of aggregate that leads to a zero net present value of project cash flows realised over the aggregates project life. The results show that the discounted costs of aggregate delivered to a local South East area of England market from an underground mine producing 3.5 million tonnes per annum (MTPA) of crushed rock aggregates, are in the range of £13.03 per tonne to £13.93 per tonne for the top six prospect locations. These are greater than the corresponding cost for a “reference” quarry in Leicestershire producing 3.5 MTPA (£10.95 per tonne), but lower than a “reference” quarry in Leicestershire producing 1.25 MTPA (£16.48 per tonne). These figures indicate that underground crushed rock aggregate mines located within the South East area of England may be able to compete for a share in the overall market by replacing / displacing aggregate imported from the quarries in Leicestershire and Somerset producing around or less than 1.25 MTPA. The surprise in these figures is not really that the more remote surface quarry has a lower discounted cost of aggregate delivered, but that the values for the quarry and underground mine are so close. The capital intensity for the development of underground aggregates mines was found to be higher than that required for surface quarries of comparable scale, by a factor ranging from 1.33 to 1.65 and thus may represent a disincentive for aggregates operators. Carbon Emissions The total carbon emissions of the ‘reference’ 3.5 MTPA quarry in Leicestershire were estimated at 9.28 kg CO2/tonne aggregate delivered and this is to be compared with carbon emissions for the 150 metre deep underground mines serving the local market which were estimated at 9.31 kg CO2/tonne delivered for a Bletchley prospect using an adit to access the sub-surface and 14.25 kg CO2/tonne delivered for a prospect based on the Chitty bore hole using a shaft. Depth of the mine is a key factor in determination of the relative carbon emissions from each of the underground mining operations considered as electricity consumption for ventilation, pumping and winding is proportional to depth. Recommendations The current research generated seven principal recommendations which are discussed in detail in the concluding section of the report. These are: Appraise policy incentives for underground aggregates mining. Conduct an industry-wide consultation on findings from the current research. Obtain public and stakeholder opinion on new uses for underground space. Conduct research to reducing the energy intensity of mine services. Develop a deep level aggregates-specific drilling campaign. Investigate underground aggregates mines developed from existing surface quarries. Investigate underground aggregates as co-products of industrial minerals mining

Lines of Inquiry in Mathematical Modelling Research in Education

This open access book is based on selected presentations from Topic Study Group 21: Mathematical Applications and Modelling in the Teaching and Learning of Mathematics at the 13th International Congress on Mathematical Education (ICME 13), held in Hamburg, Germany on July 24–31, 2016. It contributes to the theory, research and teaching practice concerning this key topic by taking into account the importance of relations between mathematics and the real world. Further, the book addresses the “balancing act” between developing students’ modelling skills on the one hand, and using modelling to help them learn mathematics on the other, which arises from the integration of modelling into classrooms. The contributions, prepared by authors from 9 countries, reflect the spectrum of international debates on the topic, and the examples presented span schooling from years 1 to 12, teacher education, and teaching modelling at the tertiary level. In addition the book highlights professional learning and development for in-service teachers, particularly in systems where the introduction of modelling into curricula means reassessing how mathematics is taught. Given its scope, the book will appeal to researchers and teacher educators in mathematics education, as well as pre-service teachers and school and university educator

Phenomenologies of Mars: Exploring Methods for Reading the Scientific Planetext Of Kim Stanley Robinson’s Mars Trilogy

In 2013, The New Yorker Magazine called Kim Stanley Robinson ‘one of the greatest living science-fiction writers’. And in 2008, Time Magazine named him a ‘hero of the environment.’[1] Yet, no lengthy study has yet been attempted on any of his fiction. This thesis aims to redress this absence with a long-form reading of one of the high peaks of his achievement: the Mars Trilogy. It considers that what I am calling the ‘planetext’ (or planet-text) is a vital narrative space. It assumes the perspectival form in which the Trilogy is told is crucial to understanding how its planetexts are read. The several viewpoints in the Trilogy comprise the several attempts of this thesis toward understanding not only how the planet is used in the novels, but also how it arranges and functions according to textual principles of readability. My several readings adopt the scientific bases of each of these viewpoints, and develops a sense of the way different characters experience the planet around them as either enabled by science, or confounded by it. ‘Planetext’ is therefore a useful neologism for interpreting how such a vast and multidimensional site as Mars is, or is not, encountered through these sciences. Understanding the planetext of Mars is therefore a phenomenological task, with the requirement of reading how each character is able, or unable, to experience and comprehend their experiences. A sense of the phenomenologies of Mars means this thesis must take the approach of seeing how different sciences yield different phenomenologies, and different experiences of the planet. By calling Mars a planetext, this thesis investigates the ways in which language, writing, and textuality participate in building the planet of the Trilogy, treating writing as a coefficient of terraforming. Understood as a kind of planetography, or planetary writing, the planetext (or host of planetexts) foregrounds the written-ness of the Martian space in Robinson’s Trilogy. The planetextual space of the novels shapes a variety of readerly paths through the narrative, which are in turn adopted. As a long study, this thesis understands the planet as a sizeable arena, which challenges the view any one reading can give of it. Acknowledging this as a limitation, its four chapters focus only on four characters, aiming to supplement an overview style of reading the Trilogy with a series of close readings. Understanding the textual status of the planet means paying specific attention to how characters either find meaningful access to the planet, or fail to find any. For Ann Clayborne, a geologist who wants to keep Mars uncontaminated and un-colonized, the planetext forms itself as a zone of différance, in which the task of interpreting the non-living planet must coincide with her resistance to the terraforming project. With Michel Duval, the Martian psychiatrist, readability is itself questioned as he attempts to overcome his depression and homesickness. For Saxifrage Russell, one of the chief terraformers, a discussion over scientific method takes the path of this thesis away from the troubling and compromised planetexts of Ann and Michel, toward how textual meaning is enabled and opened. With Hiroko Ai, a final theorization of what I call viridical force is proposed as a planetextual function, based around the Trilogy’s mention of viriditas and Jacques Derrida’s idea of force, to come to terms with how the planet makes itself available to the reader as expansive, rich in possible meaning, and always arranging itself around the reader. Between the opening of the planetext and its equivocations, this thesis charts its course. [1] Tim Kreider, ‘Our Greatest Living Novelist?’ December 12, 2013. The New Yorker Magazine. http://www.newyorker.com/books/page-turner/our-greatest-political-novelist; Oliver Morton, ‘Kim Stanley Robinson: Heroes of the Environment 2008,’ Wednesday September 24, 2008. Time Magazine. http://content.time.com/ time/specials/packages/article/0,28804,1841778_1841779_1841803,00.htm

Urban sunspaces : ecology of atria and arcades

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1981.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH.Includes bibliographical references (leaves 160-167).Historically, atria were protected interior patios; well perceived for their climate tempering and spatial amenity to the building; matching a peaceful private outdoor with the yearly climate cycles. Public buildings adopted this in larger scale, and with the ending 18th century, atria and arcades merged to a period of architectural highlights of glass covered interiors in steel and glass. Passages, hotels and public buildings of an emerging industrial society in Europe and Northern States spurred the evolution of the "Great Indoors" as an urban feature. The ecology of these indoors were consciously achieved by passive means of temperature control. With the rise of mechanical conditioning and excessive use of glass at facades by the beginning of this century, atria and arcades disappeared more or less from the architectural vocabulary. The late 1950s though experienced a revival of atria as a commercial amenity in malls, hotels and similar type of public places. These atria, however, were generally mechanical conditioned; just typically being enormous energy wasters. With the growing urge for energy conservation today, new parameters form our buildings. For this, atria and arcades of urban scale and passive control achieve a new validity as energy conscious urban form. As the key to our energy future in buildings lies well in the urban context, whose inventory per se offers already a fair degree of energy efficiency, improvements there would yield greatest rewards compared to current suburban solar sprawl. The re-interpretation of atria and arcades will provide a perfect planning tool for this urban energy conservation. The glass covered indoors will match with urban scale and site restraints and spur urban life for livable norther winter cities. Exploring atria and arcades as climate buffers and interior amenity for snow belt latitudes, this thesis presents an architectural review, and concludes with design patterns for habitable and energy conscious urban indoors.by Joachim W. Glässel.M.S