SNS Timing System

This poster describes the timing system being designed for Spallation Neutron Source being built at Oak Ridge National lab

Control system integration

This lecture begins with a definition of an accelerator control system, and then reviews the control system architectures that have been deployed at the larger accelerator facilities. This discussion naturally leads to identification of the major subsystems and their interfaces. We shall explore general strategies for integrating intelligent devices and signal processing subsystems based on gate arrays and programmable DSPs. The following topics will also be covered: physical packaging; timing and synchronization; local and global communication technologies; interfacing to machine protection systems; remote debugging; configuration management and source code control; and integration of commercial software tools. Several practical realizations will be presented

Corrosion control and disinfection studies in spacecraft water systems

Disinfection and corrosion control in the water systems of the Saturn 5 Orbital Workshop Program are considered. Within this framework, the problem areas of concern are classified into four general areas: disinfection; corrosion; membrane-associated problems of disinfectant uptake and diffusion; and taste and odor problems arising from membrane-disinfectant interaction

Macropolyhedral boron-containing cluster chemistry. Ligand-induced two-electron variations of intercluster bonding intimacy. Structures of nineteen-vertex[(eta(5)-C5Me5) HIrB18H19(PMe2Ph)] and the related carbene complex [(eta(5)-C5Me5)HIrB18H19{C(NHMe)(2)}]

Addition of PMe2Ph to fused-cluster syn-[(η5-C5Me5)IrB18H20] 1 to give [(η5-C5Me5)HIrB18H19(PMe2Ph)] 3 entails a diminution in the degree of intimacy of the intercluster fusion, rather than retention of inter-subcluster binding intimacy and a nido → arachno conversion of the character of either of the subclusters. Reaction with MeNC gives [(η5-C5Me5)HIrB18H19{C(NHMe)2}] 4 which has a similar structure, but with the ligand now being the carbene {:C(NHMe)2}, resulting from a reductive assembly reaction involving two MeNC residues and the loss of a carbon atom

Macropolyhedral boron-containing cluster chemistry: two-electron variations in intercluster bonding intimacy. Contrasting structures of 19-vertex [(eta(5)-C5Me5)HIrB18H19(PHPh2)] and [(eta(5) -C5Me5)IrB18H18(PH2Ph)]

Fused double-cluster [(5-C5Me5)IrB18H18(PH2Ph)]8, from syn-[(5-C5Me5)IrB18H20] 1 and PH2Ph, retains the three-atoms-in-common cluster fusion intimacy of 1, in contrast to [(5-C5Me5)HIrB18H19(PHPh2)]6, from PHPh2 with 1, which exhibits an opening to a two atoms-in-common cluster fusion intimacy. Compound 8 forms via spontaneous dihydrogen loss from its precursor [(5-C5Me5)HIrB18H19(PH2Ph)]7, which has two-atoms-in-common cluster-fusion intimacy and is structurally analogous to 6

Letter from the Editors

Even amid the Covid-19 pandemic, The Gettysburg Historical Journal has not forgotten its commitment to publishing the best of undergraduate research. We are heartened to witness students’ continued dedication to excellent work in an array of historical topics. Despite the difficulties we still face—mental and emotional exhaustion, shuttered archives, limited in-person research opportunities—we received a particularly high volume of submissions this year. We are proud to present work from our peers at Gettysburg and around the world in this twentieth edition of our journal. Through the stories we encounter in the past, we gain insight into the human experience in a variety of contexts and receive the tools to work towards a better present and future

Extragalactic Radio Sources and the WMAP Cold Spot

We detect a dip of 20-45% in the surface brightness and number counts of NVSS sources smoothed to a few degrees at the location of the WMAP cold spot. The dip has structure on scales of approximately 1-10 degrees. Together with independent all-sky wavelet analyses, our results suggest that the dip in extragalactic brightness and number counts and the WMAP cold spot are physically related, i.e., that the coincidence is neither a statistical anomaly nor a WMAP foreground correction problem. If the cold spot does originate from structures at modest redshifts, as we suggest, then there is no remaining need for non-Gaussian processes at the last scattering surface of the CMB to explain the cold spot. The late integrated Sachs-Wolfe effect, already seen statistically for NVSS source counts, can now be seen to operate on a single region. To create the magnitude and angular size of the WMAP cold spot requires a ~140 Mpc radius completely empty void at z<=1 along this line of sight. This is far outside the current expectations of the concordance cosmology, and adds to the anomalies seen in the CMB.Comment: revised version, ApJ, in pres

Finite element modelling of pellet-clad interaction during operational transients

A finite element model of pellet-clad interaction in advanced gas cooled reactor fuel experiencing extended reduced power operations is presented. The model considers a 1/8th segment of fuel and overlaying cladding bonded to it. A radial crack is introduced to the pellet, this is able to open and close, straining a section of cladding above the crack. In addition, circumferential cracks in the fuel pellet result in a sliver of fuel being bonded to the cladding; this sliver of fuel contains hairline radial cracks, known as ladder cracks, the opening and closing of which are modelled. Finally, the model predicts the creep strain at the tip of an incipient crack in the cladding, ahead of the radial crack in the fuel pellet. Results show that the crack tip creep strain is strongly dependent on the model of ladder cracking chosen