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| 2. |
- Marcouille, O., et al.
(författare)
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Production of high energy photons with in vacuum wigglers : From SOLEIL wiggler to MAXIV wiggler
- 2019
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Ingår i: Proceedings of the 13th International Conference on Synchrotron Radiation Instrumentation, SRI 2018. - : Author(s). - 9780735417823 ; 2054
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Konferensbidrag (refereegranskat)abstract
- Small gap wigglers become more and more attractive to produce high photon fluxes in the hard X-ray photon range. They use magnet blocks of high magnetization which resists much better to heating (baking, synchrotron radiation) than in the past, produce high magnetic field with numerous periods and are very compact. They also are a very good alternative to superconducting technology which requires special infrastructure, heavy maintenance and is not running cost free. SOLEIL, operating presently at 2.75 GeV has designed and built an in-vacuum wiggler of 38 periods of 50 mm producing 2.1 T at a minimum gap of 5.5 mm to delivered photon beam between 20 keV and 50 keV. Already in operation, further improvements are presently in progress to push photons towards higher energy, in particular thanks to the operation at lower gap (4.5 mm). MAX IV and SOLEIL, in the frame of collaboration, ave built an upgraded version of the existing SOLEIL wiggler with the target to extend the spectral range at high energy (above 50 keV) but also at low energy (4 keV) with the same insertion device. The design of the existing magnetic system has been modified to reach 2.4 T at a minimum gap of 4.2 mm and includes taper operation to avoid undulator structure in the radiated spectrum at low energy.
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| 3. |
- Tavakoli, S., et al.
(författare)
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A hybrid empirical–analytical model for predicting the roll motion of prismatic planing hulls
- 2018
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Ingår i: Journal of Engineering for the Maritime Environment (Part M). - : SAGE Publications Ltd. - 1475-0902 .- 2041-3084. ; 232:2, s. 155-175
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Tidskriftsartikel (refereegranskat)abstract
- During the last 5 years, there have been some major advances in roll motion modeling of planing boats. In this article, previous studies have been reviewed, and an attempt has been made to propose a relatively straightforward method for computing roll motion coefficients and thus predicting the roll response of a planing vessel in calm water on a straight path with constant speed. The proposed method has been developed by modifying, combining, and using previous empirical and analytical methods. Roll restoring moment is determined by implementing an asymmetric parameter in previous relations of lift of planing hulls. Also, an empirical method is proposed for computing righting arm of this moment. Roll damping is computed using previous relations related to damping of lift force and considering the asymmetrical effects. Roll added mass is obtained by utilizing an analytical approach for the roll of a flat plate. However, an effective half-wetted beam computed by asymmetrical effects has been proposed for this purpose. Finally, it has been suggested that current hypothesis be used for time-domain simulation. Validity of the proposed method is evaluated by comparing the obtained righting moment, response amplitude operator, and roll hydrodynamic coefficients against previously published experimental data. This comparison confirms that the proposed method has relatively good accuracy against experimental results. Using the current method, the influence of Froude beam number on roll hydrodynamic coefficients and roll responses has been investigated. It is observed that increase in Froude beam number results in a decrease in roll added mass and an increase in the roll damping. It has also been concluded that for larger load coefficients, the roll hydrodynamic coefficients are larger. Results associated with roll response indicate that an increase in Froude beam number would yield an increase in the amplitude of the response. However, an increase in load coefficient results in a decrease in the response.
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| 4. |
- Tavakoli, S., et al.
(författare)
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Determination of hydrodynamic coefficients in roll motion of high-speed planing hulls
- 2015
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Ingår i: SNAME 13th International Conference on Fast Sea Transportation, FAST 2015. - : The Society of Naval Architects and Marine Engineers.
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Konferensbidrag (refereegranskat)abstract
- Observations by crew of high-speed planing boats and sea trial tests have indicated that high-speed planing hulls suffer poor longitudinal and transverse instabilities, and boat may experience unfavorable motions due to any small environmental excitation. In this regard, dynamic motions of planing boats have been investigated over the last thirty years, during which innovative linear and nonlinear methods have been developed .In these studies, different method s have been developed by various authors to determine forces and moments acting on the hull. However, majority of investigators have focused on vertical motions of planning boats in waves (such as Zarnick [1978], Hicks and Troesch [1994] etc.) and few researchers have only attempted to model motions in transverse and horizontal planes including sway, yaw and roll motions. Furthermore, most of researches dealing with transverse and horizontal planning motions, were experimentally conducted (such as Judge [2010], Morabito et al [2014] etc). There exist only few articles, in which mathematical models for transverse motion have been developed. Therefore, it is needed to develop as implemathematical models for prediction of transverse motions of planing boats for use in conceptual design phase. During the last five years, there has been an increased interesting study of transverse motions, and in the current paper, an attempt has been made for a mathematical study of roll motion of planning hulls.
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| 5. |
- Tavakoli, S., et al.
(författare)
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Prediction of hydrodynamic coefficients of coupled heave and pitch motions of heeled planing boats by asymmetric 2D+T theory
- 2018
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Ingår i: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. - : American Society of Mechanical Engineers (ASME).
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Konferensbidrag (refereegranskat)abstract
- This paper attempts to present a mathematical model to predict hydrodynamic coefficients of a heeled planing hull in vertical plane. This model has been developed by using 2D+T theory and theoretical solution of the water entry of wedge section bodies. Sectional hydrodynamic force acting on the vessel is determined and then extended over the entire length of the vessel. By simplifying final equations of heave force and pitch moment acting on a heeled planing hull, equations for prediction of hydrodynamic coefficients of the vessel are developed. Accuracy of the method is evaluated by comparing its results against previous empirical methods. It is seen that current method has reasonable accuracy in prediction of different hydrodynamic coefficients. Also, effects of heel angle on added mass, damping and stiffness coefficients are studied and discussed.
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