Attitude analysis of the Earth Radiation Budget Satellite (ERBS) yaw turn anomaly

The July 2 Earth Radiation Budget Satellite (ERBS) hydrazine thruster-controlled yaw inversion maneuver resulted in a 2.1 deg/sec attitude spin. This mode continued for 150 minutes until the spacecraft was inertially despun using the hydrazine thrusters. The spacecraft remained in a low-rate Y-axis spin of .06 deg/sec for 3 hours until the B-DOT control mode was activated. After 5 hours in this mode, the spacecraft Y-axis was aligned to the orbit normal, and the spacecraft was commanded to the mission mode of attitude control. This work presents the experience of real-time attitude determination support following analysis using the playback telemetry tape recorded for 7 hours from the start of the attitude control anomaly

A review of the mallet impact test for small scale explosive formulations

Presented at 19th Seminar on New Trends of Energetic Materials (NTREM 2016); 20-22/04/2016, Pardubice Czech RepublicDevelopment of new explosive formulations begins with the generation of only a few milligrams of material which is investigated using a number of small scale tests such as DSC, TGA, response to flame, mallet impact (mallet friction either glancing or direct blow) to determine whether the formulation is safe to scale up to 10 g. The latter of these tests, mallet impact, can be particularly subjective as the result is directly influenced by the operator carrying out the assessment. Not only can there be a change from one operator to another but there can also be a change in the force applied during each strike potentially leading to inconsistent results. This study highlights this encountered variation and assesses the load applied by a variety of operators with varying levels of explosive experience. This paper also proposes the use of a small scale laboratory based impact test which would provide improved confidence in the assessment of impact sensitiveness of explosive formulations and assist in justifying whether a formulation can be taken to the next scale. A small scale version of the BAM impact test (EMTAP Test 43) has been devised that allows the comparison of the sensitiveness of small scale formulations relative to RDX (8.7 J, EMTAP Test 43B) whilst also ensuring a reproducible result

Energy Spectrum Evolution of a Diffuse Field in Elastic Body Caused by Weak Nonlinearity

We study the evolution of diffuse elastodynamic spectral energy density under the influence of weak nonlinearity. It is shown that the rate of change of this quantity is given by a convolution of the linear energy at two frequencies. Quantitative estimates are given for sample aluminum and fused silica blocks of experimental interest.Comment: 9 pages, 3 figures; revised for better presentatio

Scattering fidelity in elastodynamics

The recent introduction of the concept of scattering fidelity, causes us to revisit the experiment by Lobkis and Weaver [Phys. Rev. Lett. 90, 254302 (2003)]. There, the ``distortion'' of the coda of an acoustic signal is measured under temperature changes. This quantity is in fact the negative logarithm of scattering fidelity. We re-analyse their experimental data for two samples, and we find good agreement with random matrix predictions for the standard fidelity. Usually, one may expect such an agreement for chaotic systems only. While the first sample, may indeed be assumed chaotic, for the second sample, a perfect cuboid, such an agreement is more surprising. For the first sample, the random matrix analysis yields a perturbation strength compatible with semiclassical predictions. For the cuboid the measured perturbation strength is much larger than expected, but with the fitted values for this strength, the experimental data are well reproduced.Comment: 4 page

African American Adults’ Experiences with the Health Care System: In Their Own Words

African Americans suffer a disproportionate burden of death and illness from a number of different chronic diseases. Inequalities in health care practices and poor patient and provider communication between African American patients and health care professionals contribute to these disparities. We describe findings from focus groups with 79 urban African Americans in which the participants discussed their interactions with the healthcare system as well as beliefs and opinions of the healthcare system and professionals. Analysis revealed five major themes: (1) historical and contextual foundations; (2) interpersonal experiences with physicians and other health care workers; (3) discrimination; (4) trust, opinions and attitudes, and (5) improving health care experiences. These findings indicate that perceptions of discrimination and racism were prevalent among African Americans in this study, and that the expectation of a negative interaction is a barrier to seeking care. Authors discuss prevention and public health implications of these findings and make recommendations for health care practitioners

Bandwidth and density for block graphs

The bandwidth of a graph G is the minimum of the maximum difference between adjacent labels when the vertices have distinct integer labels. We provide a polynomial algorithm to produce an optimal bandwidth labeling for graphs in a special class of block graphs (graphs in which every block is a clique), namely those where deleting the vertices of degree one produces a path of cliques. The result is best possible in various ways. Furthermore, for two classes of graphs that are ``almost'' caterpillars, the bandwidth problem is NP-complete.Comment: 14 pages, 9 included figures. Note: figures did not appear in original upload; resubmission corrects thi

Effect of Alkyl Chain Length and Linker Atom on the Crystal Packing in 6,12-Dialkoxy- And 6,12-Dialkylsulfanyl-Benzo[1,2- b:4,5- b′]bis[ b]benzothiophenes

The effect of varying the chain length on the solid state conformation and packing of 6,12-dialkoxy- and 6,12-dialkylsulfanyl-benzo[1,2-b:4,5-b′]bis[b]benzothiophenes has been studied. The compounds were prepared by SNAr reaction of 6,12-difluorbenzo[1,2-b:4,5-b′]bis[b]benzothiophene with alkoxides or alkanethiolates derived from C7-C10 alcohols and alkanethiols. Single crystal X-ray diffraction analysis revealed that all but two compounds crystallize in the triclinic space group P1. Two compounds were obtained as monoclinic crystals with space group P21/c. The alkoxy substituted compounds adopted a molecular conformation with a step from the core and a gauche conformation about the C1′-C2′ bond placing the alkyl chains close to parallel with the pentacyclic arene ring system, whereas in the alkylsufanyl derivatives, the alkyl chains were arranged strongly deviated from the plane of the ring, with the sulfur atom antiperiplanar to C3′ of the alkyl chain. NMR measurement of T1 relaxation in CDCl3 showed both the alkoxy and alkylsulfanyl substituents to be freely rotating at ambient temperature in solution, indicating the orientation of the chains in the solid state was due to packing interactions during crystallization

Petrography and geochemistry of Khewra Trap, a unique ultrapotassic rock in the Salt Range of Pakistan

Abstract HKT-ISTP 2013 A

Role of oxygen in the electron-doped superconducting cuprates

We report on resistivity and Hall measurements in thin films of the electron-doped superconducting cuprate Pr$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$. Comparisons between x = 0.17 samples subjected to either ion-irradiation or oxygenation demonstrate that changing the oxygen content has two separable effects: 1) a doping effect similar to that of cerium, and 2) a disorder effect. These results are consistent with prior speculations that apical oxygen removal is necessary to achieve superconductivity in this compound.Comment: 5 pages, 5 figure