On relative tt-designs in polynomial association schemes

Motivated by the similarities between the theory of spherical $t$-designs and that of $t$-designs in $Q$-polynomial association schemes, we study two versions of relative $t$-designs, the counterparts of Euclidean $t$-designs for $P$- and/or $Q$-polynomial association schemes. We develop the theory based on the Terwilliger algebra, which is a noncommutative associative semisimple $\mathbb{C}$-algebra associated with each vertex of an association scheme. We compute explicitly the Fisher type lower bounds on the sizes of relative $t$-designs, assuming that certain irreducible modules behave nicely. The two versions of relative $t$-designs turn out to be equivalent in the case of the Hamming schemes. From this point of view, we establish a new algebraic characterization of the Hamming schemes.Comment: 17 page

Analysis of the state of the art of precast concrete bridge substructure systems

abstract: In 2001, the American Association of State Highway and Transportation Officials Technology Implementation Group identified prefabricated bridge construction as a technology that should be advanced and implemented as quickly as possible. Bridge designs incorporating prefabricated superstructure elements are not new or innovative, as precast concrete beams or girders have been around since roughly the 1950s. However, until the last 25 years, incorporating precast concrete bridge substructure components into design has been very limited. This research focused on the collection of information related to the design and construction of precast concrete bridge substructures, with sources including state and federal transportation agency websites and published literature; conference and workshop proceedings and presentations; professional associations and societies; and other published literature sources, such as technical journals. This project reviewed this literature to determine the current state of practice with respect to the use of precast substructures on bridges in the United States. This project also evaluated the various precast substructure technologies for their applicability to “typical” Arizona bridges.Final report 687.Includes bibliographical references (p. 99-104)

SYSTEM STUDIES OF FISSION-FUSION HYBRID MOLTEN SALT REACTORS

This work proposes and evaluates a Fission-Fusion Hybrid Molten Salt Reactor (FFHMSR), combining two subsystems, a deuterium + tritium (DT) fusion reactor surrounded by a neutron-absorbing Fusion Blanket (FB) and a critical Molten Salt fission Reactor (MSR). The molten salt, which contains dissolved actinides, circulates at a high rate between them. As envisioned the MSR exhibits the large Conversion Ratio of graphite moderated reactors having small fissile and large fertile inventories. DT fusion neutrons irradiating actinides in the molten salt release additional neutrons which increase isotope conversion and fission. Actinide fuel is continually added while fission products are continually removed so the system\u27s operation never requires refueling interruptions. The choice of molten salt as a eutectic mixture of the fluorides of lithium, sodium, and actinide fuel is explained by eliminating other options. System behavior is explored through simulations invoking modules from the Scale 6.1 code package. Modules include ORIGEN which simulates evolution over time of an isotope inventory and others for neutronics transport, criticality and cross section weighting. The simulation automatically adjusts the ratio of fission to fusion power to maintain MSR criticality, implemented through FORTRAN codes and associated files developed as part of this work. Simulations showed actinide inventories stabilizing to steady levels while fresh actinide fuel from feedstocks of Spent Nuclear Fuel or uranium-238 or thorium-232 continued to be added and fissioned. Required fusion was less than 1% of total power and adequate tritium breeding was obtained. The non-removal strategy was also tried with long-lived fission products (FPs) with the mixed results that some inventories stabilized while others did not. FFHMSR benefits of consuming all actinides and some long-lived FPs are that waste issues are ameliorated while available fission energy is increased by two orders of magnitude. Proliferation resistance is enhanced by the absence of fuel reprocessing and related transportation, by low fissile inventories and by denaturing all fissile by nonfissile isotopes. Safety is enhanced by liquid fuel characteristics allowing emergency draining of fuel to a passively cooled safe location while also providing a stronger negative power coefficient than feasible with solid fuel

On metric Ramsey-type phenomena

The main question studied in this article may be viewed as a nonlinear analogue of Dvoretzky's theorem in Banach space theory or as part of Ramsey theory in combinatorics. Given a finite metric space on n points, we seek its subspace of largest cardinality which can be embedded with a given distortion in Hilbert space. We provide nearly tight upper and lower bounds on the cardinality of this subspace in terms of n and the desired distortion. Our main theorem states that for any epsilon>0, every n point metric space contains a subset of size at least n^{1-\epsilon} which is embeddable in Hilbert space with O(\frac{\log(1/\epsilon)}{\epsilon}) distortion. The bound on the distortion is tight up to the log(1/\epsilon) factor. We further include a comprehensive study of various other aspects of this problem.Comment: 67 pages, published versio

M.I.N.G., Mars Investment for a New Generation: Robotic construction of a permanently manned Mars base

A basic procedure for robotically constructing a manned Mars base is outlined. The research procedure was divided into three areas: environment, robotics, and habitat. The base as designed will consist of these components: two power plants, communication facilities, a habitat complex, and a hangar, a garage, recreation and manufacturing facilities. The power plants will be self-contained nuclear fission reactors placed approx. 1 km from the base for safety considerations. The base communication system will use a combination of orbiting satellites and surface relay stations. This system is necessary for robotic contact with Phobos and any future communication requirements. The habitat complex will consist of six self-contained modules: core, biosphere, science, living quarters, galley/storage, and a sick bay which will be brought from Phobos. The complex will be set into an excavated hole and covered with approximately 0.5 m of sandbags to provide radiation protection for the astronauts. The recreation, hangar, garage, and manufacturing facilities will each be transformed from the four one-way landers. The complete complex will be built by autonomous, artificially intelligent robots. Robots incorporated into the design are as follows: Large Modular Construction Robots with detachable arms capable of large scale construction activities; Small Maneuverable Robotic Servicers capable of performing delicate tasks normally requiring a suited astronaut; and a trailer vehicle with modular type attachments to complete specific tasks; and finally, Mobile Autonomous Rechargeable Transporters capable of transferring air and water from the manufacturing facility to the habitat complex

Interrogating the technical, economic and cultural challenges of delivering the PassivHaus standard in the UK.

A peer-reviewed eBook, which is based on a collaborative research project coordinated by Dr. Henrik Schoenefeldt at the Centre for Architecture and Sustainable Environment at the University of Kent between May 2013 and June 2014. This project investigated how architectural practice and the building industry are adapting in order to successfully deliver Passivhaus standard buildings in the UK. Through detailed case studies the project explored the learning process underlying the delivery of fourteen buildings, certified between 2009 and 2013. Largely founded on the study of the original project correspondence and semi-structured interviews with clients, architects, town planners, contractors and manufacturers, these case studies have illuminated the more immediate technical as well as the broader cultural challenges. The peer-reviewers of this book stressed that the findings included in the book are valuable to students, practitioners and academic researchers in the field of low-energy design. It was launched during the PassivHaus Project Conference, held at the Bulb Innovation Centre on the 27th June 2014

Novel Greening, Processing Route, and Bio-Inspired Hierarchical Structuring of Engineered Cementitious Composites for Sustainable Infrastructure

Strain-hardening cementitious composites (SHCCs) are a family of cementitious materials that preserve the advantages of concrete as a construction material, while eliminating many of concrete’s shortcomings. While concrete is weak and brittle in tension, SHCCs exhibit a degree of tensile ductility under extreme loading and material toughness hundreds of times that of concrete, providing enhanced durability and resilience for cementitious infrastructure. This research covers three materials design projects aimed at expanding the capabilities of the SHCC family, offering their durability and resilience benefits to new infrastructure use cases and enhancing those qualities in others. First, the use of natural plant fibers, rather than synthetic polymer fibers, as the sole reinforcement in SHCC materials is explored as a route for material greening. Strategies to overcome the design challenges associated with the use of natural fibers are reported and a curauá fiber reinforced strain-hardening cementitious composite is introduced. Second, the concept and micromechanical design considerations of strain-hardening cementitious composites are applied to cementitious materials designed for building-scale 3D printing. Automated additive manufacturing techniques, such as 3D printing, are poised to revolutionize the construction industry, offering benefits in time and cost efficiency and human safety. However, the full potential of building-scale 3D printing has been hampered by the required insertion of ancillary reinforcement, antithetical to the bottom-up, freeform 3D printing paradigm. By using SHCC materials as the primary printing material, these limitations could be removed, improving design freedoms, efficiency, and the inherent durability and resiliency of the printed structure. Compositional and processing strategies to achieve printability in SHCC materials (and cementitious materials in general) are investigated and reported. Proof-of-concept printable SHCC materials are demonstrated, and their mechanical performance is characterized. Third, enhanced mechanical property profiles of SHCC materials are pursued, as inspired by the structure and deformation mechanisms of a natural composite material found in seashells. Despite being composed 95% of a brittle chalk-like material, nacre exhibits remarkable tensile strength, tensile ductility, and toughness. Strategies of adapting nacre’s hierarchical structural organization and associated deformation mechanisms to a large size scale and with materials relevant to infrastructural applications are explored and evaluated. SHCCs serve as an efficient means to achieve this structure and these mechanisms due to their characteristic tensile behaviors. These nacre-inspired composite design strategies are pursued as means to improve the holistic mechanical property profiles of SHCCs. Applied to the highest strength versions of SHCCs, these bio-inspired design strategies offer benefits to seismic, blast, and impact resistant infrastructure applications. This research seeks broad impact by addressing the sustainability of infrastructure through material greening and improved durability and resilience of the fundamental building block of most modern infrastructure: cementitious materials. Parametric studies are used to design novel versions of SHCCs with new and useful characteristics, all while deliberately engineering the fiber, matrix, and interfacial properties to generate strain-hardening behavior. In addition to addressing specific compositional or performance targets, resulting in three novel types of functional SHCCs, each design project produces results and implications related to the others.PHDMacromolecular Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/140848/1/dsoltan_1.pd