Universal twist in Equivariant K-theory for proper and discrete actions

We define equivariant projective unitary stable bundles as the appropriate twists when defining K-theory as sections of bundles with fibers the space of Fredholm operators over a Hilbert space. We construct universal equivariant projective unitary stable bundles for the orbit types, and we use a specific model for these local universal spaces in order to glue them to obtain a universal equivariant projective unitary stable bundle for discrete and proper actions. We determine the homotopy type of the universal equivariant projective unitary stable bundle, and we show that the isomorphism classes of equivariant projective unitary stable bundles are classified by the third equivariant integral cohomology group. The results contained in this paper extend and generalize results of Atiyah-Segal.Comment: 46 pages. To appear in Proceedings of the London Mathematical Society. This version might differ from the published version, thought its mathematical contents are the sam

Board structures around the world: An experimental investigation

We model and experimentally examine the board structure-performance relationship. We examine single-tiered boards, two-tiered boards, insider-controlled boards, and outsider-controlled boards. We find that even insider-controlled boards frequently adopt institutionally preferred rather than self-interested policies. Two-tiered boards adopt institutionally preferred policies more frequently, but tend to destroy value by being too conservative, frequently rejecting good projects. Outsidercontrolled single-tiered boards, both when they have multiple insiders and only a single insider, adopt institutionally preferred policies most frequently. In those board designs where the efficient Nash equilibrium produces strictly higher payoffs to all agents than the coalition-proof equilibria, agents tend to select the efficient Nash equilibria.

Corporate board composition, protocols, and voting behavior: experimental evidence

We model experimentally the governance of an institution. The optimal management of this institution depends on the information possessed by insiders. However, insiders, whose interests are not aligned with the interests of the institution, may choose to use their information to further personal rather than institutional ends. Researchers (e.g., Palfrey 1990) and the business press have both argued that multiagent mechanisms, which inject trustworthy but uninformed “watchdog” agents into the governance process and impose penalties for conflicting recommendations, can implement institutionally preferred outcomes. Our laboratory experiments strongly support this conclusion. In the experimental treatments in which watchdog agents were included, the intuitionally preferred allocation was implemented in the vast majority of cases. Surprisingly, implementation occurred even in the absence of penalties for conflicting recommendations.Corporations - Finance ; Game theory

Board structures around the world: An experimental investigation

We model and experimentally examine the board structure–performance relationship. We examine single-tiered boards, two-tiered boards, insider-controlled boards, and outsider-controlled boards. We find that even insider-controlled boards frequently adopt institutionally preferred rather than self-interested policies. Two-tiered boards adopt institutionally preferred policies more frequently, but tend to destroy value by being too conservative, frequently rejecting good projects. Outsidercontrolled single-tiered boards, both when they have multiple insiders and only a single insider, adopt institutionally preferred policies most frequently. In those board designs where the efficient Nash equilibrium produces strictly higher payoffs to all agents than the coalition-proof equilibria, agents tend to select the efficient Nash equilibria

A Data-driven Approach for Estimating Relative Voltage Sensitivity

Voltage sensitivity expresses analytically the dependency between voltage and active or reactive power. Knowing the voltage sensitivity is necessary in many power system applications, such as the Distributed Energy Resources (DER) optimal placement and control. The majority of voltage sensitivity estimation methods assume having an accurate model of the grid and only consider a balanced grid operation at the nominal point, which is not realistic. In this paper, a method based on Mutual Information (MI) is proposed, which is able to evaluate the nonlinear dependencies between two variables, in order to estimate the relative voltage sensitivity. Contrary to the existing methods, the proposed MI-based approach only requires measurements at the point of interest and does not require any grid model nor measurements from other nodes in the grid. As a use case, the optimal allocation for an Energy Storage System (ESS) in a real medium voltage network in Germany has been presented. Measurement results confirm the effectiveness of the new approach for estimating relative voltage sensitivity

Modeling Superconducting Components of the Electric Aircraft

Electrification of the mobility sector is at the center of attention to reduce CO2 emissions and mitigate man-made climate change. At present, aircraft is responsible for around 2.4 % of the annual global carbon emissions. This is a motivation behind developing fully-electric, zero-emission aircraft. The advantages of superconductivity including compactness, lightweight, and high efficiency make this technology a promising choice to accelerate the transition to electric aircraft. The powertrain for a large electric aircraft includes different components like motors, converters, DC and AC cables, batteries, fuel cells, fault current limiters, power generators and fuel storage. The higher the total power of the electric aircraft, the more interesting it is to use superconducting devices. In this work, the approach to model the overall electric powertrain with MATLAB/SIMULINK is presented. Within the overall model, several superconducting devices are simulated in detail. One component is a resistive superconducting fault current limiter which is modeled via an electrical-thermal lumped-parameter method in MATLAB. The simulation results are given in detail and discussed. In addition, a configurable MATLAB Simulink model of the fault limiter is developed for integration with wider systems models. Another model for a superconducting DC cable has been developed. The electrical-thermal, lumped parameter and two-dimensional modeling of this component are studied and its operation is simulated using MATLAB programming. Finally, the overall simulation methodology is presented and the current status is given

Simulation Models for Superconducting Components of the Electric Aircraft

In recent decades, a growing focus has been on reducing fossil fuel consumption and minimizing CO2 emissions in the transportation sector. The aerospace industry, which accounted for more than 2% of global carbon emissions in 2021, has taken measures to address this issue. One promising solution to achieve this objective is the development of fully electric aircraft (FEA). In this regard, superconducting technology offers promising advantages, including compactness, lightweight, and higher efficiency to speed up this transition. This work considers a superconducting propulsion system for an electric aircraft. Among the components, the modeling of resistive superconducting fault current limiter (RSFCL) and superconducting DC cable are studied. These models are simulated by MATLAB programming and SIMULINK, and the results are shown. The models analyze their electrical-thermal behavior in a short short-circuit and in normal operation conditions. Finally, a SIMULINK model containing the fault limiter and cable is simulated, and the results are presented. As a result, different models are compared and suitable designs are presented for both applications

Highly coherent electron beam from a laser-triggered tungsten needle tip

We report on a quantitative measurement of the spatial coherence of electrons emitted from a sharp metal needle tip. We investigate the coherence in photoemission using near-ultraviolet laser triggering with a photon energy of 3.1 eV and compare it to DC-field emission. A carbon-nanotube is brought in close proximity to the emitter tip to act as an electrostatic biprism. From the resulting electron matter wave interference fringes we deduce an upper limit of the effective source radius both in laser-triggered and DC-field emission mode, which quantifies the spatial coherence of the emitted electron beam. We obtain $(0.80\pm 0.05)\,$nm in laser-triggered and $(0.55\pm 0.02)\,$nm in DC-field emission mode, revealing that the outstanding coherence properties of electron beams from needle tip field emitters are largely maintained in laser-induced emission. In addition, the relative coherence width of 0.36 of the photoemitted electron beam is the largest observed so far. The preservation of electronic coherence during emission as well as ramifications for time-resolved electron imaging techniques are discussed

Entrepreneurially Minded Learning in the Unit Operations Laboratory through Community Engagement in a Blended Teaching Environment

Online and blended learning opportunities in Chemical Engineering curriculum emerged due to COVID-19. After eight weeks of in-person Unit Operations Laboratory sessions, a remote-learning open-ended final project was assigned to student teams. The assignment involved aspects related to entrepreneurial-minded learning (EML) and community-based learning (CBL). Results show correlations between self-directed learning and the EML framework. Continuous support and involvement of a community partner correlate to students\u27

Collusion in uniform-price auctions: experimental evidence and implications for Treasury auctions

In uniform-price auctions of shares there exist collusive equilibria in which bidders capture the entire surplus from the auction as well as competitive equilibria in which the auctioneer captures the entire surplus from the auction. We provide experimental evidence that, in uniform-price auctions, non-binding pre-play communication facilitates convergence to collusive equilibrium outcomes. On the other hand, regardless of the opportunities for communication, in discriminatory-auction experiments subject strategies conform closely with the unique equilibrium in undominated strategies in which bidders' gains are equal to the smallest "tick size" in the bidding schedule. This evidence suggests that uniform-price auctions of Treasury securities may result in lower revenues than the currently employed discriminatory procedure.Government securities ; Treasury bills