Solar vane actuator Patent

Design and characteristics of device for sensing solar radiation and providing spacecraft attitude control to maintain direction with respect to incident radiatio

Attitude control for spacecraft Patent

Attitude control system for spacecraft based on conversion of incident solar radiation on movable control surfaces into mechanical torque

The antiferromagnetic phase of the Floquet-driven Hubbard model

A saddle point plus fluctuations analysis of the periodically driven half-filled two-dimensional Hubbard model is performed. For drive frequencies below the equilibrium gap, we find discontinuous transitions to time-dependent solutions. A highly excited, generically non-thermal distribution of magnons occurs even for drive frequencies far above the gap. Above a critical drive amplitude, the low-energy magnon distribution diverges as the frequency tends to zero and antiferromagnetism is destroyed, revealing the generic importance of collective mode excitations arising from a non-equilibrium drive

Rejecting Ingrid Robeyns’ Defense of Limitarianism

This paper critically evaluates the argument put forth by the philosopher Ingrid Robeyns in her work entitled What, if Anything, is Wrong with Extreme Wealth. Robeyns holds the Chair Ethics of Institutions at Utrecht University, and her academic research focuses on issues pertaining to contemporary political philosophy and applied ethics. In her aforementioned publication, Robeyns defends the political theory called limitarianism, which holds that there should be an upper limit to the amount of income that an individual can hold. Limitarianism, like many other political philosophies, presents a view of how resources ought to be distributed in society based, in part, on certain ethical principles. Robeyns explicitly outlines two arguments in support of limitarianism as a political philosophy: (1) by eliminating excess wealth, limitarianism prevents the super-rich from undermining political equality and (2) by redistributing this excess wealth, there will be more resources available to address any urgent unmet needs or collective action problems in society. This paper carefully reviews and ultimately rejects Robeyns’ defense of limitarianism as a theory of political philosophy. This paper sets out to highlight both the flaws in the basic premises of limitarianism as a theory as well as the shortcomings of the specific arguments that Robeyns’ constructs in support of the theory itself

How Personally Relevant Cases of COVID-19 Influence Individuals’ Level of Concern towards the Virus

This paper presents the findings of a statistical analysis exploring the ways in which personally relevant cases of COVID-19 influence an individual\u27s level of concern towards the virus. The analysis makes use of public opinion data collected throughout the pandemic by a market research company called Ipsos. This study conducts an OLS regression analysis using three different samples of data from three distinct periods of time during the pandemic. The paper addresses each component of the study\u27s deductive approach, outlining everything from the initial hypothesis to the conclusions and broader implications. Ultimately, this study does show evidence that an individual\u27s personal experience with COVID-19 influences their attitudes towards the virus. This is consistent with the findings of previous psychological research that has explored how personally salient information affects humans\u27 attitudes and beliefs

Magnetotransport in the CeIrIn5{_5} system: The influence of antiferromagnetic fluctuations

We present an overview of magnetotransport measurements on the heavy-fermion superconductor CeIrIn$_5$. Sensitive measurements of the Hall effect and magnetoresistance (MR) are used to elucidate the low temperature phase diagram of this system. The normal-state magnetotransport is highly anomalous, and experimental signatures of a pseudogap-like precursor state to superconductivity as well as evidence for two distinct scattering times governing the Hall effect and the MR are observed. Our observations point out the influence of antiferromagnetic fluctuations on the magnetotransport in this class of materials. The implications of these findings, both in the context of unconventional superconductivity in heavy-fermion systems as well as in relation to the high temperature superconducting cuprates are discussed

Pair breaking by nonmagnetic impurities in the noncentrosymmetric superconductor CePt3Si

We have studied the effect of Ge substitution and pressure on the heavy-fermion superconductor CePt3Si. Ge substitution on the Si site acts as negative chemical pressure leading to an increase in the unit-cell volume but also introduces chemical disorder. We carried out electrical resistivity and ac heat-capacity experiments under hydrostatic pressure on CePt3Si1-xGex (x=0, 0.06). Our experiments show that the suppression of superconductivity in CePt3Si1-xGex is mainly caused by the scattering potential, rather than volume expansion, introduced by the Ge dopants. The antiferromagnetic order is essentially not affected by the chemical disorder.Comment: 4 pages, 4 figure

Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors

We present the first study of codoped iron-arsenide superconductors of the 122 family (Sr/Ba)_(1-x)K_xFe_(2-y)Co_yAs_2 with the purpose to increase the upper critical field H_c2 compared to single doped (Sr/Ba)Fe_2As_2 materials. H_c2 was investigated by measuring the magnetoresistance in high pulsed magnetic fields up to 64 T. We find, that H_c2 extrapolated to T = 0 is indeed enhanced significantly to ~ 90 T for polycrystalline samples of Ba_0.55K_0.45Fe_1.95Co_0.05As_2 compared to ~75 T for Ba_0.55K_0.45Fe_2As_2 and BaFe_1.8Co_0.2As_2 single crystals. Codoping thus is a promising way for the systematic optimization of iron-arsenic based superconductors for magnetic-field and high-current applications.Comment: 7 pages, 5 figures, submitted to Journal of Applied Physic

Acute Impact of Moderate-Intensity and Vigorous-Intensity Exercise Bouts on Daily Physical Activity Energy Expenditure in Postmenopausal Women

This study determined whether performing a single moderate- or vigorous-intensity exercise bout impacts daily physical activity energy expenditure (PAEE, by accelerometer). Overweight/obese postmenopausal women underwent a 5-month caloric restriction and moderate- (n = 18) or vigorous-intensity (n = 18) center-based aerobic exercise intervention. During the last month of intervention, in women performing moderate-intensity exercise, PAEE on days with exercise (577.7 ± 219.7 kcal·d−1) was higher (P = .011) than on days without exercise (450.7 ± 140.5 kcal·d−1); however, the difference (127.0 ± 188.1 kcal·d−1) was much lower than the energy expended during exercise. In women performing vigorous-intensity exercise, PAEE on days with exercise (450.6 ± 153.6 kcal·d−1) was lower (P = .047) than on days without exercise (519.2 ± 127.4 kcal·d−1). Thus, women expended more energy on physical activities outside of prescribed exercise on days they did NOT perform center-based exercise, especially if the prescribed exercise was of a higher intensity

Optimizing Attitude Control Systems

This paper discusses a practical approach to attitude control system mechanization. Previous efforts reported in the literature have either resulted in systems too complex to mechanize or have not considered the problem in enough of its aspects to make the work meaningful. The classical control optimization techniques are briefly summarized and a critique of these methods is given. The solutions obtained with the classical techniques are either open loop, which is unsatisfactory from an attitude control standpoint, or they are closed loop. These closed loop solutions in general may require measuring all of the system variables, which may not be possible, or they may be far too complex to mechanize. In the proposed approach, called specific optimal control, sensor and actuator characteristics are given and the form of the controller is chosen. Controller parameters are then chosen so as to minimize some performance index. Three analytical methods being developed to perform this optimization are hill climbing, two point boundary value problem formulation, and differential approximation. Each of these methods are discussed. Numerical examples showing the application of these techniques are given in a reference