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479 results on '"Abdalla R"'

2. Assessment of optical emission analysis for in-process monitoring of powder bed fusion additive manufacturing

Author

Alexander J. Dunbar and Abdalla R. Nassar

Subjects
process optimisation, solid freeform fabrication, in situ monitoring, powder bed fusion, inconel 718, Science, Manufactures, TS1-2301
Abstract

Developing methods which allow real-time monitoring of powder bed fusion (PBF) additive manufacturing (AM) processes is key to enabling in situ assessments of build quality (e.g. lack of fusion and porosity). Here, we investigate the use of optical emission spectroscopy and high-speed (100 kHz) measurement of select wavelength emissions, based on a line-to-continuum approach, to determine if a correlation between PBF AM process inputs, sensor outputs, and build quality exists. Using an open protocol system interfaced with a 3D Systems ProX 200 machine, sensor data were synchronised with the scanner position and the laser state during the buildup of Inconel-718 components under varying powers, scan speeds, and hatch spacing parameters. Sensor measurements were then compared against post-build computed tomography scans. We show evidence that sensor data, when combined with appropriate analyses, are related to both processing conditions and build quality.

Published
2018
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3. Adenocarcinoma of the Colon in a 10-year-old child

Author

Siboe M. M, Abdalla R. O, Lakati K.C, and Oduor P

Subjects
Surgery, RD1-811
Abstract

Colonic adenocarcinoma is rare in children, more so in the first decade of life. Owing to the non -specificity and vagueness of symptoms, most patients in this age group present with advanced malignacy. The authors report a case of adenocarcinoma of the colon in a 10-year-old female child presenting with a history of abdominal pain, distention and constipation. Barium enema high-lighted a narrowing of the distal ascending colon with laparotomy revealing a growth involving the caecum and ascending colon. Histology confirmed it as a poorly diffentiated mucin secreting adenocarcinoma. A right hemicolectomy with end to end ileo-transverse anastomosis was perfomed. Four months later, she pre-sented with symptoms of intestinal obstruction. Intraoperatively, widespread metastatic nodules with recurrent tumour were noted. It is important for clinicians to be aware that colorectal carcinoma does occur in children, and age alone should not be a basis for its exclusion. This case is presented to draw attention to a disease in which the prognosis, by wider recognition of its occurrence in childhood, might be improved.

Published
2018

5. Energy Sources and Propagation

Author

Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., Michaleris, Pan, Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., and Michaleris, Pan

Published
2023
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6. Source-Material Interactions

Author

Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., Michaleris, Pan, Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., and Michaleris, Pan

Published
2023
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15. Multiple Alloy Processing

Author

Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., Michaleris, Pan, Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., and Michaleris, Pan

Published
2023
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16. Post Processing

Author

Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., Michaleris, Pan, Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., and Michaleris, Pan

Published
2023
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17. Process Quality and Reliability

Author

Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., Michaleris, Pan, Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., and Michaleris, Pan

Published
2023
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21. Metallic Feedstock

Author

Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., Michaleris, Pan, Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., and Michaleris, Pan

Published
2023
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23. Analytical Models

Author

Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., Michaleris, Pan, Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., and Michaleris, Pan

Published
2023
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24. Feedstock Delivery and Dynamics

Author

Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., Michaleris, Pan, Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., and Michaleris, Pan

Published
2023
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26. Mechanical Response

Author

Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., Michaleris, Pan, Joshi, Sanjay, Martukanitz, Richard P., Nassar, Abdalla R., and Michaleris, Pan

Published
2023
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28. A very-high-energy component deep in the Gamma-ray Burst afterglow

Author

Arakawa, H. Abdalla R. Adam F. Aharonian F. Ait Benkhali E. O. Anguener M., Arcaro, C., Armand, C., Ashkar, H., Backes, M., Martins, V. Barbosa, Becherini, M. Barnard Y., Berge, D., Bernloehr, K., Bissaldi, E., Blackwell, R., Boettcher, M., Boisson, C., Bolmont, J., Bonnefoy, S., Bregeon, J., Breuhaus, M., Brun, F., Brun, P., Bryan, M., Buechele, M., Bulik, T., Bylund, T., Capasso, M., Caroff, S., Carosi, A., Casanova, S., Cerruti, M., Chand, T., Chandra, S., Chen, A., Colafrancesco, S., Curylo, M., Davids, I. D., Deil, C., Devin, J., deWilt, P., Dirson, L., Djannati-Atai, A., Dmytriiev, A., Donath, A., Doroshenko, V., Dyks, J., Egberts, K., Emery, G., Ernenwein, J. -P., Eschbach, S., Feijen, K., Fegan, S., Fiasson, A., Fontaine, G., Funk, S., Fuessling, M., Gabici, S., Gallant, Y. A., Gate, F., Giavitto, G., Giunti, L., Glawion, D., Glicenstein, J. F., Gottschall, D., Grondin, M. -H., Hahn, J., Haupt, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hofmann, W., Hoischen, C., Holch, T. L., Holler, M., Horns, D., Huber, D., Iwasaki, H., Jamrozy, M., Jankowsky, D., Jankowsky, F., Jardin-Blicq, A., Jung-Richardt, I., Kastendieck, M. A., Katarzynski, K., Katsuragawa, M., Katz, U., Khangulyan, D., Khelifi, B., King, J., Klepser, S., Kluzniak, W., Komin, N., Kosack, K., Kostunin, D., Kreter, M., Lamanna, G., Lemiere, A., Lemoine-Goumard, M., Lenain, J. -P., Leser, E., Levy, C., Lohse, T., Lypova, I., Mackey, J., Majumdar, J., Malyshev, D., Marandon, V., Marcowith, A., Mares, A., Mariaud, C., Marti-Devesa, G., Marx, R., Maurin, G., Meintjes, P. J., Mitchell, A. M. W., Moderski, R., Mohamed, M., Mohrmann, L., Moore, C., Moulin, E., Muller, J., Murach, T., Nakashima, S., de Naurois, M., Ndiyavala, H., Niederwanger, F., Niemiec, J., Oakes, L., Brien, P. O, Odaka, H., Ohm, S., Wilhelmi, E. de Ona, Ostrowski, M., Oya, I., Panter, M., Parsons, R. D., Perennes, C., Petrucci, P. -O., Peyaud, B., Piel, Q., Pita, S., Poireau, V., Noel, A. Priyana, Prokhorov, D. A., Prokoph, H., Puehlhofer, G., Punch, M., Quirrenbach, A., Raab, S., Rauth, R., Reimer, A., Reimer, O., Remy, Q., Renaud, M., Rieger, F., Rinchiuso, L., Romoli, C., Rowell, G., Rudak, B., Ruiz-Velasco, E., Sahakian, V., Sailer, S., Saito, S., Sanchez, D. A., Santangelo, A., Sasaki, M., Schlickeiser, R., Schuessler, F., Schulz, A., Schutte, H. M., Schwanke, U., Schwemmer, S., Seglar-Arroyo, M., Senniappan, M., Seyffert, A. S., Shafi, N., Shiningayamwe, K., Simoni, R., Sinha, A., Sol, H., Specovius, A., Spir-Jacob, M., Stawarz, L., Steenkamp, R., Stegmann, C., Steppa, C., Takahashi, T., Tavernier, T., Taylor, A. M., Terrier, R., Tiziani, D., Tluczykont, M., Trichard, C., Tsirou, M., Tsuji, N., Tuffs, R., Uchiyama, Y., van der Walt, D. J., van Eldik, C., van Rensburg, C., van Soelen, B., Vasileiadis, G., Veh, J., Venter, C., Vincent, P., Vink, J., Voelk, H. J., Vuillaume, T., Wadiasingh, Z., Wagner, S. J., White, R., Wierzcholska, A., Yang, R., Yoneda, H., Zacharias, M., Zanin, R., Zdziarski, A. A., Zech, A., Ziegler, A., Zorn, J., Zywucka, N., de Palma, F., Axelsson, M., and Roberts, O. J.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Gamma-ray bursts (GRBs) are brief flashes of gamma rays, considered to be the most energetic explosive phenomena in the Universe. The emission from GRBs comprises a short (typically tens of seconds) and bright prompt emission, followed by a much longer afterglow phase. During the afterglow phase, the shocked outflow -- produced by the interaction between the ejected matter and the circumburst medium -- slows down, and a gradual decrease in brightness is observed. GRBs typically emit most of their energy via gamma-rays with energies in the kiloelectronvolt-to-megaelectronvolt range, but a few photons with energies of tens of gigaelectronvolts have been detected by space-based instruments. However, the origins of such high-energy (above one gigaelectronvolt) photons and the presence of very-high-energy (more than 100 gigaelectronvolts) emission have remained elussive. Here we report observations of very-high-energy emission in the bright GRB 180720B deep in the GRB afterglow -ten hours after the end of the prompt emission phase, when the X-ray flux had already decayed by four orders of magnitude. Two possible explanations exist for the observed radiation: inverse Compton emission and synchrotron emission of ultrarelativistic electrons. Our observations show that the energy fluxes in the X-ray and gamma-ray range and their photon indices remain comparable to each other throughout the afterglow. This discovery places distinct constraints on the GRB environment for both emission mechanisms, with the inverse Compton explanation alleviating the particle energy requirements for the emission observed at late times. The late timing of this detection has consequences for the future observations of GRBs at the highest energies., Comment: Preprint version of Nature paper. Contacts: E.Ruiz-Velasco, F. Aharonian, E.Bissaldi, C.Hoischen, R.D Parsons, Q.Piel, A.Taylor, D.Khangulyan

Published
2019
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