Determination of life for a polyimide-epoxy alternator insulation system

Tests were conducted to predict remaining electrical insulation life of a polyimide epoxy insulated 60 KW, 208 volt homopolar inductor alternator, following completion of 23,130 hours of turbo-alternator endurance tests. The sectioned armature winding of this alternator stator was used as means to evaluate and measure end-life at several aging temperatures for development of an Arrhenius plot. A one-half life rate of 11.3 C was established from these data with a predicted remaining life of 60,000 hours at an armature winding temperature of 248 C and a total life, including endurance test time, of 61,645 hours

Cyclic and Long-term Variation of Sunspot Magnetic Fields

Measurements from the Mount Wilson Observatory (MWO) are used to study the long-term variations of sunspot field strengths from 1920 to 1958. Following a modified approach similar to that in Pevtsov et al. (2011), for each observing week we select a single sunspot with the strongest field strength measured that week and then compute monthly averages of these weekly maximum field strengths. The data show the solar cycle variation of the peak field strengths with an amplitude of about 500-700 gauss (G), but no statistically significant long-term trends. Next, we use the sunspot observations from the Royal Greenwich Observatory (RGO) to establish a relationship between the sunspot areas and the sunspot field strengths for Cycles 15-19. This relationship is then used to create a proxy of peak magnetic field strength based on sunspot areas from the RGO and the USAF/NOAA network for the period from 1874 to early 2012. Over this interval, the magnetic field proxy shows a clear solar cycle variation with an amplitude of 500-700 G and a weaker long-term trend. From 1874 to around 1920, the mean value of magnetic field proxy increases by about 300-350 G, and, following a broad maximum in 1920-1960, it decreases by about 300 G. Using the proxy for the magnetic field strength as the reference, we scale the MWO field measurements to the measurements of the magnetic fields in Pevtsov et al. (2011) to construct a combined data set of maximum sunspot field strengths extending from 1920 to early 2012. This combined data set shows strong solar cycle variations and no significant long-term trend (linear fit to the data yields a slope of $-0.2\pm$0.8 G year$^{-1}$). On the other hand, the peak sunspot field strengths observed at the minimum of the solar cycle show a gradual decline over the last three minima (corresponding to cycles 21-23) with a mean downward trend of $\approx$ 15 G year$^{-1}$

Spin Waves in Ferromagnetic Metals and the Dynamical Form of the Landau Quasi-particle Theory

Spin waves in ferromagnetic metals dynamical form of Landau quasi-particle theor

Inclusion of an Introduction to Infrastructure Course in a Civil and Environmental Engineering Curriculum

Civil infrastructure refers to the built environment (sometimes referred to as public works) and consists of roads, bridges, buildings, dams, levees, drinking water treatment facilities, wastewater treatment facilities, power generation and transmission facilities, communications, solid waste facilities, hazardous waste facilities, and other sectors. Although there is a need to train engineers who have a holistic view of infrastructure, there is evidence that civil and environmental engineering (CEE) programs have not fully addressed this increasingly recognized need. One effective approach to address this educational gap is to incorporate a course related to infrastructure into the curriculum for first-year or second-year civil and environmental engineering students. Therefore, this study assesses the current status of teaching such courses in the United States and identifies the incentives for, and the barriers against, incorporating an introduction to infrastructure course into schools’ current CEE curricula. Two distinct activities enabled these objectives. First, a questionnaire was distributed to CEE programs across the United States, to which 33 responses were received. The results indicated that although the majority of participants believe that offering such a course will benefit students by increasing the breadth of the curriculum and by providing a holistic view of CEE, barriers such as the maximum allowable credits for graduation, the lack of motivation within a department—either because such a course did not have a champion or because the department had no plans to revise their curriculum—and a lack of expertise among faculty members inhibited inclusion of the course in curricula. Second, three case studies demonstrating successful inclusion of an introduction to infrastructure course into the CEE curriculum were evaluated. Cases were collected from Marquette University, University of Wisconsin-Platteville, and West Point CEE programs, and it was found that the key to success in including such a course is a motivated team of faculty members who are committed to educating students about different aspects of infrastructure. The results of the study can be used as a road map to help universities successfully incorporate an introduction to infrastructure course in their CEE programs

Soft X-ray seeding studies for the SLAC Linac Coherent Light Source II

We present the results from studies of soft X-ray seeding options for the LCLS-II X-ray free electron laser (FEL) at SLAC. The LCLS-II will use superconducting accelerator technology to produce X-ray pulses at up to 1 MHz repetition rate using 4 GeV electron beams. If properly seeded, these pulses will be nearly fully coherent, and highly stable in photon energy, bandwidth, and intensity, thus enabling unique experiments with intense high-resolution soft X-rays. Given the expected electron beam parameters from start to end simulations and predicted FEL performance, our studies reveal echo enabled harmonic generation (EEHG) and soft X-ray self-seeding (SXRSS) as promising and complementary seeding methods. We find that SXRSS has the advantage of simplicity and will deliver 5-35 times higher spectral brightness than EEHG in the 1-2 nm range, but lacks some of the potential for phase-stable multipulse and multicolor FEL operations enabled by external laser seeding with EEHG

Transport and Spectra in the Half-filled Hubbard Model: A Dynamical Mean Field Study

We study the issues of scaling and universality in spectral and transport properties of the infinite dimensional particle--hole symmetric (half-filled) Hubbard model within dynamical mean field theory. One of the simplest and extensively used impurity solvers, namely the iterated perturbation theory approach is reformulated to avoid problems such as analytic continuation of Matsubara frequency quantities or calculating multi-dimensional integrals, while taking full account of the very sharp structures in the Green's functions that arise close to the Mott transitions and in the Mott insulator regime. We demonstrate its viability for the half-filled Hubbard model. Previous known results are reproduced within the present approach. The universal behavior of the spectral functions in the Fermi liquid regime is emphasized, and adiabatic continuity to the non-interacting limit is demonstrated. The dc resistivity in the metallic regime is known to be a non-monotonic function of temperature with a `coherence peak'. This feature is shown to be a universal feature occurring at a temperature roughly equal to the low energy scale of the system. A comparison to pressure dependent dc resistivity experiments on Selenium doped NiS$_2$ yields qualitatively good agreement. Resistivity hysteresis across the Mott transition is shown to be described qualitatively within the present framework. A direct comparison of the thermal hysteresis observed in V$_2$O$_3$ with our theoretical results yields a value of the hopping integral, which we find to be in the range estimated through first-principle methods. Finally, a systematic study of optical conductivity is carried out and the changes in absorption as a result of varying interaction strength and temperature are identified.Comment: 19 pages, 12 figure

Effect of Optical Coating and Surface Treatments on Mechanical Loss in Fused Silica

We report on the mechanical loss in fused silica samples with various surface treatments and compare them with samples having an optical coating. Mild surface treatments such as washing in detergent or acetone were not found to affect the mechanical loss of flame-drawn fused silica fibers stored in air. However, mechanical contact (with steel calipers) significantly increased the loss. The application of a high-reflective optical coating of the type used for the LIGO test masses was found to greatly increase the mechanical loss of commercially polished fused silica microscope slides. We discuss the implications for the noise budget of interferometers.Comment: 7 pages, 2 figures. Accepted for publication in the Proceedings of the Third Eduardo Amaldi Conference on Gravitational Waves, July 12-16, 1999. Updated version contains a correction of Eq. 3 and an estimate for the loss angle of a LIGO coating. (Neither of these revisions are included in the version published in the conference proceedings.

High quality factor measured in fused silica

We have measured the mechanical dissipation in a sample of fused silica drawn into a rod. The sample was hung from a multiple-bob suspension, which isolated it from rubbing against its support, from recoil in the support structure, and from seismic noise. The quality factor, Q, was measured for several modes with a high value of 57 million found for mode number 2 at 726 Hz. This result is about a factor 2 higher than previous room temperature measurements. The measured Q was strongly dependent on handling, with a pristine flame-polished surface yielding a Q 3-4 times higher than a surface which had been knocked several times against a copper tube.Comment: Preprint - Under review by LSC publications committe