The twentieth century people--a study of the population

Thesis (Ph.D.)--Boston Universit

Large antenna apertures and arrays for deep space communications

Effect of frequency on communications capability, single antennas and arrays, and economic balance between ground station and spacecraft developmen

Decision Performance and Safety Performance: A Value-Focused Thinking Study in the Oil Industry

Considerable research has been performed to develop leading indicators of safety performance. We use value-focused thinking to understand the objectives and evaluation measures that frame a particular safety-related decision within an organization. These decisions are part of the safety culture. Our research partners were two oil shipping companies; we surveyed crewmembers on their tankers to evaluate performance in each decision objective on their vessel. We demonstrate that measurements of the achievement of these objectives are related to future safety performance and thus provide leading indicators of safety

Is Screening Cargo Containers for Smuggled Nuclear Threats Worthwhile?

In recent years, Customs and Border Protection (CBP) has installed radiation sensors to screen cargo containers entering theUnited States. They are concerned that terrorists could use containers to smuggle radiological material into the country and carry out attacks with dirty bombs or a nuclear device. Recent studies have questioned the value of improving this screening system with new sensor technology. The cost of delays caused by frequent false alarms outweighs any reduction in the probability of an attack in an expected cost analysis. We extend existing methodology in three ways to demonstrate how additional factors affect the value of screening investments. We examine the effect that screening has in discouraging terrorists. We model multiple levels of screening. Finally, we consider additional objectives beyond cost. We find that the conclusion about screening depends on key inputs to the probability model (reflecting uncertainties) and to the value function (reflecting the stakeholders’ fundamental objectives)

210 ft advanced antenna system - Report on hydrostatic bearing damage

Advanced antenna thrust bearing accident investigatio

Oblique internal hydraulic jumps at a stratified estuary mouth

Author Posting. © American Meteorological Society, 2017. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 47 (2017): 85-100, doi:10.1175/JPO-D-15-0234.1.Observations and analyses of two tidally recurring, oblique, internal hydraulic jumps at a stratified estuary mouth (Columbia River, Oregon/Washington) are presented. These hydraulic features have not previously been studied due to the challenges of both horizontally resolving the sharp gradients and temporally resolving their evolution in numerical models and traditional observation platforms. The jumps, both of which recurred during ebb, formed adjacent to two engineered lateral channel constrictions and were identified in marine radar image time series. Jump occurrence was corroborated by (i) a collocated sharp gradient in the surface currents measured via airborne along-track interferometric synthetic aperture radar and (ii) the transition from supercritical to subcritical flow in the cross-jump direction via shipborne velocity and density measurements. Using a two-layer approximation, observed jump angles at both lateral constrictions are shown to lie within the theoretical bounds given by the critical internal long-wave (Froude) angle and the arrested maximum-amplitude internal bore angle, respectively. Also, intratidal and intertidal variability of the jump angles are shown to be consistent with that expected from the two-layer model, applied to varying stratification and current speed over a range of tidal and river discharge conditions. Intratidal variability of the upchannel jump angle is similar under all observed conditions, whereas the downchannel jump angle shows an additional association with stratification and ebb velocity during the low discharge periods. The observations additionally indicate that the upchannel jump achieves a stable position that is collocated with a similarly oblique bathymetric slope.We acknowledge the financial support of the Office of Naval Research under Awards N00014-10-1-0932 and N00014-13-1-0364.2017-07-0

A Multiple-Objective Decision Analysis of Stakeholder Values to Identify Watershed Improvement Needs

The paper describes the use of multiple objective decision analysis to qualitatively and quantitatively assess the quality of an endangered watershed and guide future efforts to improve the quality of the watershed. The Upham Brook watershed is an urban watershed that lies at the interface of declining inner city Richmond, Virginia and growth-oriented Henrico County. A section of stream within the watershed has been identified as so dangerously polluted that it threatens the health of the residents who live within the watershed boundaries. With funding provided by the National Science Foundation, the Upham Brook watershed project committee was formed to address the quality of the Upham Brook watershed; it consisted of experts from multiple disciplines: stream ecology, environmental policy, water policy, ground and surface water hydrology and quality, aquatic biology, political science, sociology, citizen participation, community interaction, psychology, and decision and risk analysis. Each members\u27 values and goals were brought together using a watershed management framework to meet the overall objective of the committee: to maximize the quality of the Upham Brook watershed. The resulting model was used to identify the largest value gaps and to identify future programs needed to improve the quality of the watershed

Characterization of human expired breath by solid phase microextraction and analysis using gas chromatography-mass spectrometry and differential mobility spectrometry

Thesis (M. Eng.)--Harvard-MIT Division of Health Sciences and Technology, 2005.Includes bibliographical references (leaves 92-95).Breath analysis has potential to become a new medical diagnostic modality. In this thesis, a method for the analysis of human expired breath was developed using gas chromatography-mass spectroscopy. It was subsequently adopted for gas chromatography-differential mobility spectroscopy, a modality not previously applied to this problem. Tedlar bags and solid-phase microextraction were used for breath sampling and concentration prior to analysis. Four fiber coatings were evaluated with respect to selectivity and sensitivity; extraction time, gas chromatography temperature programming, and sample storage stability were explored for optimization. The method entails extraction and preconcentration with a polydimethylsiloxane-divinylbenzene coated fiber for 30 min at 37⁰C, and extraction profiles for several compounds demonstrate competitive adsorption. 120 compounds were identified in breath with response variability between 23 - 117% about mean values. Feasibility of differential mobility spectroscopy for breath analysis was established, and this method will be the basis for future investigations on the diagnostic potential of breath analysis.by William Merrick.M.Eng

Measuring the impact of roadworks on traffic progression using floating car data

Roadworks projects, while necessary to upgrade and maintain our transport networks, are loathed for their presumed negative impact on our daily commute. The purpose of this study is to investigate how Floating Car Data (FCD) can be used to assess the influence of a work zone on traffic progression. The effective change in speed and travel time was examined within and around a work zone of the recently completed upgrade of the N1 in Cape Town, particularly during the lane closure of the inbound section of the N1 between Durban Road and Jip de Jager Drive. The use of FCD to assess the impact of work zones provided unprecedented insight into traffic patterns such as the change in position of bottlenecks during roadworks. FCD was shown to improve our understanding of traffic movement within work zones. This can provide input to strategies for safer traffic accommodation during roadworks, going some way to improve the daily commute of road users.Papers presented virtually at the 39th International Southern African Transport Conference on 05 -07 July 202

Investigating Dataset Distinctiveness

Just as a human might struggle to interpret another human’s handwriting, a computer vision program might fail when asked to perform one task in two different domains. To be more specific, visualize a self-driving car as a human driver who had only ever driven on clear, sunny days, during daylight hours. This driver – the self-driving car – would inevitably face a significant challenge when asked to drive when it is violently raining or foggy during the night, putting the safety of its passengers in danger. An extensive understanding of the data we use to teach computer vision models – such as those that will be driving our cars in the years to come – is absolutely necessary as these sorts of complex systems find their way into everyday human life. This study works to develop a comprehensive meaning of the style of a dataset, or the quantitative difference between cursive lettering and print lettering, with respect to the image data used in the field of computer vision. We accomplished this by asking a machine learning model to predict which commonly used dataset a particular image belongs to, based on detailed features of the images. If the model performed well when classifying an image based on which dataset it belongs to, that dataset was considered distinct. We then developed a linear relationship between this distinctiveness metric and a model’s ability to learn from one dataset and test on another, so as to have a better understanding of how a computer vision system will perform in a given context, before it is trained