40,694 research outputs found
Owner challenges on major projects: The case of UK government
Many studies agree that owner organisations are important for successful project organising, but they tend to focus on particular aspects of project organising rather than providing a holistic analysis of owners as organisations. Our objective is to collect evidence of the full range of challenges public sector owners face in managing their major projects. After reviewing the literature on owner organisations, we carry out a case survey of 26 major projects to identify the principal challenges using a content analysis of UK National Audit Office Value for Money reports. Our original contribution is that the findings provide the first comprehensive picture of the full range of challenges of project organising faced by owner organisations. These findings push us theoretically to extend the scope of research in project organising to identify an extended core set of dynamic capabilities for project owner organisations to address these challenges
The summatory function of the M\"obius function in function fields
We study the growth rate of the summatory function of the M\"obius function
in the context of an algebraic curve over a finite field. Our work shows a
strong resemblance to its number field counterpart, which was proved by Ng in
2004. We find an expression for a bound of the summatory function, which
becomes sharp when the zeta zeros of the curve satisfy a certain linear
independence property. Extending a result of Kowalski in 2008, we prove that
most curves in the family of universal hyperelliptic curves satisfy this
property. Then, we consider a certain geometric average of such bound in this
family, using Katz and Sarnak's reformulation of the equidistribution theorem
of Deligne. Lastly, we study an asymptotic behavior of this average as the
family gets larger by evaluating the average values of powers of characteristic
polynomials of random unitary symplectic matrices.Comment: 16 pages. In this revision, an error in residue calculation in
Section 2 is corrected, and a few bibliographic items are update
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Department of Energy Engineering (Battery Science and Technology)Aprotic electrolyte based lithium-oxygen batteries are of considerable interest due to its ultrahigh theoretical specific energy density (1675 mAh per gram of oxygen) against the present lithium-ion battery. In spite of the attractiveness of its high theoretical capacity, there is a number of drawbacks such as instability of electrochemical reaction of electrode and electrolytes. In order to overcome these parasitic reactions, significant efforts have been devoted to developing the key materials such as carbon-free air cathodes and high concentrated electrolytes. However, the CO2 evolution during the charging process and low ionic conductivity limit the ideal electrochemical reaction in aprotic electrolytes.
In this thesis, we applied the molten electrolyte based on nitrate-based electrolyte (Li/Na/K/Cs/Ca-NO3). The molten electrolyte, which has a eutectic point of 65???, has the advantages of high stability and high-temperature operation, thereby preventing detrimental solvent byproducts in lithium-oxygen batteries. We examined the Oxygen Evolution Reaction (OER) and Oxygen Reduction Reaction (ORR) on operating temperature using in situ pressure drop and gas analyses, Differential Electrochemical Mass Spectrometry (DEMS). Our results demonstrated that the Li2O2, a discharge product, formed a stable hexagonal morphology in the lithium-oxygen battery upon discharge process by scanning electron microscopy and X-ray diffraction techniques. Also, it leads to improved oxygen mobility at high temperature since a molten salt was used as the electrolyte in lithium-oxygen batteries. In addition, we found that kinetics are improved with increasing operating temperature in molten salt electrolyte cells.ope
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Characterization of a 50kW Inductively Coupled Plasma Torch for Testing of Ablative Thermal Protection Materials Using Non-Air Gases
Thermal protection systems have been a major area of study since the advent of space flight, but recent efforts towards crewed spaceflight missions have placed a new importance on the development of such systems. The 50 kW Inductively Coupled Plasma (ICP) Torch Facility at The University of Texas at Austin allows for rapid testing of high-temperature aerospace materials essential to the development of thermal protection systems in planetary re-entry applications. This ICP Torch Facility has been previously characterized using air as the test gas. However, planets of interest for future exploration have atmospheric compositions that differ from air, so testing heat shield materials in the presence of other gases is critical. To address this disparity between tested and actual environment, the current work characterizes the torch using various combinations of argon, CO2, and N2 by determining its operational range at various power settings, mass flow rates, and mixtures these gases. At each setting, the cold-wall heat flux is also measured to determine the range the torch is able to provide. Measurements indicate that using pure Ar gives the torch the largest operating range with regard to power setting and gas injection mass flow rate, and mixing argon into other gases drastically increases the stable operating range compared to the pure gas. Pure CO2 does not form a stable plasma discharge, but a mixture of 50% argon and 50% CO2 (by mass) provides stable operation up to 40 slpm total gas flow rate with a maximum heat flux of 98 W/cm2. Smaller percentages of CO2 allow the cold-wall heat flux to be increased to 110 W/cm2. Pure N2 forms a stable plasma discharge, but the operating range is very limited, providing stable operation up to 20 slpm total gas flow rate with a maximum heat flux of 110 W/cm2.Aerospace Engineering and Engineering Mechanic
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