Developing system models to help Great Britain's railways embrace innovative technologies with confidence

Railways are under pressure to become more efficient and cut their costs; innovation has a part to play in achieving these goals. The railway is, however, a complex and closely coupled system, making it difficult in the early stages of development, to be clear what the system-wide impact of innovation will be. The research covered in this paper stems from the idea that computer-based models of existing systems can help overcome this problem, by providing a baseline framework against which the impact of innovation can be identified. The paper describes development of a repeatable modelling methodology, which elicits\ud objective system data from Railway Group Standards and integrates it using CORE®, a powerful system modelling tool, to create system models. The ability of such models to help identify impacts is verified, using as an example the introduction of RailBAM (a new technology that acoustically monitors the health of rolling stock axle bearings) into the existing hot axle bearing detection system

Design for Harmony: An Exploration of Enterprise and Product Architecture Tradespace Dynamics

Student research poste

Exploring Dynamic Enterprise and Product Architecture Tradespaces

Student research poste

Effects of Plot Size and Habitat Characteristics on Breeding Success of Scarlet Tanagers

We studied the effects of forest patch size and habitat characteristics on breeding success of Scarlet Tanagers (Piranga olivacea) in western New York in 1995 and 1996. Twenty forest stands were grouped into four size classes: Group I (\u3c10\u3eha, n = 6), Group 11 (10 to 50 ha, n = 7), Group III (\u3e50 to 150 ha, n = 5), and Group IV (\u3e1,000 ha, n = 2). Group I, II, and III sites were habitat patches located in fragmented landscapes, whereas Group IV sites were located in continuous forests. Although densities of male tanagers were similar in Group II, III, and IV sites, tanagers were absent from all forest patches smaller than 10 ha. Territory size did not differ among males in Group II, III, and IV sites. Pairing success exceeded 75% in all forest size classes in 1995 and 1996, and 100% of the observed males were paired in continuous forest sites. Pairing success differed significantly among forest size classes in 1995 and approached significance in 1996. Fledging success increased significantly with area and was highest (64%) in continuous forest sites. Stepwise multiple regression and principal components analysis indicated that male tanagers breeding in for-est patches with higher canopy cover and lower density of oaks had higher pairing success than males in patches with lower canopy cover and higher density of oaks, and that males breeding in larger forest patches with more surrounding forest cover had higher fledging success than males in small patches with less surrounding forest cover. Our results indicate that: (1) breeding density is not a good indicator of habitat quality for forest-interior Neotropical migrants, and (2) large tracts of continuous forest are important for maintaining populations of these species

Space communications responsive to events across missions (SCREAM): an investigation of network solutions for transient science space systems

2022 Spring.Includes bibliographical references.The National Academies have prioritized the pursuit of new scientific discoveries using diverse and temporally coordinated measurements from multiple ground and space-based observatories. Networked communications can enable such measurements by connecting individual observatories and allowing them to operate as a cohesive and purposefully designed system. Timely data flows across terrestrial and space communications networks are required to observe transient scientific events and processes. Currently, communications to space-based observatories experience large latencies due to manual service reservation and scheduling procedures, intermittent signal coverage, and network capacity constraints. If space communications network latencies could be reduced, new discoveries about dynamic scientific processes could be realized. However, science mission and network planners lack a systematic framework for defining, quantifying and evaluating timely space data flow implementation options for transient scientific observation scenarios involving multiple ground and space-based observatories. This dissertation presents a model-based systems engineering approach to investigate and develop network solutions to meet the needs of transient science space systems. First, a systematic investigation of the current transient science operations of the National Aeronautics and Space Administration's (NASA) Tracking and Data Relay Satellite (TDRS) space data network and the Neil Gehrels Swift Observatory resulted in a formal architectural model for transient science space systems. Two methods individual missions may use to achieve timely network services were defined, quantitatively modeled, and experimentally compared. Next, the architectural model was extended to describe two alternative ways to achieve timely and autonomous space data flows to multiple space-based observatories within the context of a purposefully designed transient science observation scenario. A quantitative multipoint space data flow modeling method based in queueing theory was defined. General system suitability metrics for timeliness, throughput, and capacity were specified to support the evaluation of alternative network data flow implementations. A hypothetical design study was performed to demonstrate the multipoint data flow modeling method and to evaluate alternative data flow implementations using TDRS. The merits of a proposed future TDRS broadcast service to implement multipoint data flows were quantified and compared to expected outcomes using the as-built TDRS network. Then, the architectural model was extended to incorporate commercial network service providers. Quantitative models for Globalstar and Iridium short messaging data services were developed based on publicly available sources. Financial cost was added to the set of system suitability metrics. The hypothetical design study was extended to compare the relative suitability of the as-built TDRS network with the commercial Globalstar and Iridium networks. Finally, results from this research are being applied by NASA missions and network planners. In 2020, Swift implemented the first automated command pipeline, increasing its expected gravitational wave follow-up detection rate by greater than 400%. Current NASA technology initiatives informed by this research will enable future space-based observatories to become interoperable sensing devices connected by a diverse ecosystem of network service providers

Teaching an Engineering Systems Doctoral Seminar: Concepts and Structure

This paper describes the current state of the evolving engineering systems doctoral seminar in the Engineering Systems Division (ESD) at MIT. This subject is required for all first year engineering systems doctoral students. It is intended to bring them into the culture of ESD, and to establish a common base on which subsequent subjects can build. It is the first of three required subjects that make up the core of the ESD doctoral program. The seminar is intended to provide students with the foundations and context of engineering systems, largely focused on providing an appreciation for the many facets of socio-technical complexity. We discuss the seminar’s pedagogy, learning objectives, assignments and readings, and provide insights gained from teaching the course

Temperature effects on the vertical movements of the Severn Suspension Bridge’s suspension cables measured by GNSS

The use of GNSS for the deflection monitoring of large bridges has been an ongoing field of research for 20 years. The Severn Suspension Bridge, in the UK, has a main span length of 988 metres. Datasets were gathered in both March 2010 and July 2015 by placing GNSS antennas on the tops of the support towers, as well as on the suspension cables. The data were gathered over four days and three days respectively during these surveys. In addition to the GNSS data, weigh in motion data of the traffic loading, the temperature of the bridge’s steel work, and the air temperature and wind speed and direction at a number of locations were collected. In 2010, the temperature during the survey varied between 0.335ºC to 13.750ºC for the air temperature, and between 0.886ºC to 12.390ºC for the steel temperature. During the survey in 2015, the temperature for the air varied between 10.800ºC to 22.160ºC, and the steel temperature varied between 13.820ºC to 20.410ºC. This paper analyses the vertical movements at the mid span of the bridge’s suspension cable using the data from 2010 and also 2015. The vertical movements are due to a number of reasons. Firstly, the traffic flow will cause rapid changes in the height of the cable, of the order ofdecimetres due to changes in traffic loading over a time period of seconds or minutes. Secondly, the wind will also cause movements in the cable, but mainly in the horizontal direction. Vertical movements due to the vibrating nature of the cable will also be present, at a rate of 0.1Hz or so. Finally, the cable will expand and contract due to the change in temperature. This will take place over a period of tens of minutes. The relation between the antenna location in 2010 and 2015 are calculated against changes in temperature, and correlation between the movements are shown. The overall movements due to the change in temperature during the survey in 2010 can be shown to be of the order of decimetres, and similarly in 2015. The change in a bridge’s height, due to a change in temperature is an important parameter to be known. A bridge in the UK could experience changes in temperature from almost 30ºC to -10ºC in a period of a year during its lifetime. In other parts of the world, this differential could be even more. This could result in a very significant vertical movement of the bridge, which in turn could affect the clearance space under the bridge for passing ships. This type of movement tied with changing tides could result in large ships colliding with such bridges if the clearance is not fully understood